JP2005204489A - Control system of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to maintain a vehicle in a desired state, by reducing the delay of vehicle behavior in steering of a driver, in a four-wheel-drive vehicle in which four-wheel steering is possible and a motor is mounted on at least one right or left wheel of the front and rear wheels. <P>SOLUTION: The control system of a four-wheel-drive vehicle, in which four-wheel steering is possible, performs the control for giving a moment to a vehicle and the control for setting up an actual steering angle independently of a front wheel and a rear wheel. The moment to be given to the vehicle, the front wheel actual steering angle ratio of the steering input and the actual steering angle to be set as a front wheel, and the rear wheel actual steering angle ratio of the steering input and the actual steering angle to be set as a rear wheel are computed so that at the steering time the yaw rate generated by the vehicle in the case of giving the moment, the body slip angle, and the lateral acceleration are controlled as a desired value. The moment, the front wheel actual steering angle ratio to be computed in this way, and the rear wheel actual steering angle ratio are set in the vehicle, so that it may be possible for the vehicle at the time of steering to generate a suitable vehicle behavior. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to turning stability control of a vehicle that can be driven by four wheels using a motor in addition to an engine and can be steered by front and rear wheels.

  There is known a four-wheel drive (4WD) vehicle in which one of the front and rear wheels is driven by an engine and the other is driven by a driving device such as a motor. Among these four-wheel drive vehicles, if the fisting of the vehicle becomes unstable during traveling, the driving force distribution ratio of the front and rear wheels is changed, or the driving force (ie, “torque”) distribution ratio of the left and right wheels is changed. There are things that change the attitude of the vehicle and turn, such as turning. For example, in the vehicle control device described in Patent Document 1, the vehicle is given to the vehicle based on parameters representing the vehicle running state, such as the vehicle steering angle, vehicle speed, longitudinal acceleration, lateral acceleration, and yaw rate. The target yaw moment (hereinafter simply referred to as “moment”) is calculated.

  There are also four-wheel steering (4WS) vehicles that can steer not only front wheels but also rear wheels. Among such four-wheel steering vehicles, there are some which improve the turning stability of the vehicle by changing the actual steering angle of each of the four wheels when the vehicle turns. For example, the technique described in Patent Document 2 describes a four-wheel drive vehicle that is capable of four-wheel steering, in which one of the front and rear wheels is driven by an engine and the other is driven by a motor.

  By the way, with respect to the driver's steering, the vehicle is delayed and yaw rate, lateral acceleration (hereinafter simply referred to as “lateral acceleration”), vehicle body slip angle, and the like (hereinafter referred to as “vehicle behavior”) are generated. I know that. As described above, since the vehicle behavior occurs after the driver's steering, the driver may feel uncomfortable that the vehicle behavior generated with respect to the steering does not match. In addition, when the driver feels such a sense of incongruity, the stability of the turning motion of the vehicle may be impaired.

  However, in the vehicle control technology described in Patent Documents 1 and 2 described above, only the moment control using a motor or the like is performed, and the cooperation with the steering system is not performed. At times, the vehicle behavior appropriate for the steering could not be obtained. Therefore, the uncomfortable feeling that the driver learns when steering the vehicle cannot be resolved.

JP-A-11-301293 JP-A-6-247168

  The present invention has been made in view of the above points, and is a four-wheel drive vehicle capable of four-wheel steering and having motors mounted on at least one left and right wheels of the front and rear wheels. An object of the present invention is to provide a vehicle control device that can reduce a delay in behavior and maintain the vehicle in a desired state.

  In one aspect of the present invention, a vehicle control device that can drive one of the front and rear wheels by a motor and independently steer the front and rear wheels includes a moment calculation unit that calculates a moment to be applied to the vehicle, Front and rear wheel actual steering angle calculating means for calculating actual steering angles to be set for the front wheels and rear wheels of the vehicle, and the moment calculating means and the front and rear wheel actual steering angle calculating means are desired by the vehicle during steering. It calculates so that it may become the state of.

  The vehicle control device described above calculates a moment to be applied to the vehicle in a four-wheel drive vehicle in which at least one of the front and rear wheels is driven by a motor, and controls a drive torque to each motor based on the calculated moment. To do. Further, the vehicle control device can calculate the actual steering angle that should be set independently for the front wheels and the rear wheels, and can impose the calculated actual steering angles on the front wheels and the rear wheels. In response to the steering operation (ie, steering) by the driver for turning the vehicle, the yaw rate, the lateral acceleration, and the vehicle body slip angle are delayed in the vehicle. For this reason, the vehicle control device described above has a moment to be applied to the vehicle and an actual steering angle of the front and rear wheels to be set on the vehicle (hereinafter, referred to as the following) so that the vehicle at the time of steering turns in a desired state. Simply referred to as “front and rear wheel actual steering angle”). By setting the moment calculated in this way and the front and rear wheel actual steering angles to the vehicle, the vehicle at the time of steering can be made to perform an appropriate vehicle behavior. That is, the vehicle can perform a vehicle behavior in cooperation with the driver's steering operation. Therefore, generation of the yaw rate, lateral acceleration, and vehicle body slip angle acting on the vehicle is not delayed with respect to the driver's steering operation. In addition, the driver does not feel discomfort when operating the steering wheel.

  One aspect of the vehicle control device is based on motor control means for controlling the motor based on the calculated moment, and on the calculated actual steering angle of the front wheel and actual steering angle of the rear wheel, Front and rear wheel steering means for changing the angles of the front and rear wheels of the vehicle, and the motor control means and the front and rear wheel steering means are provided when a driver's steering operation is performed while satisfying a predetermined condition. To do. Examples of the predetermined condition include a case where the speed at which the driver's handle is turned is equal to or higher than a predetermined speed, and a case where the angle at which the driver's handle is turned exceeds a predetermined angle. Thereby, the delay of the vehicle behavior which arises in the vehicle at the time of steering can be reduced. In addition, since the operation of the steering wheel of the driver satisfies a predetermined condition, the moment and the actual steering angle of the front and rear wheels are unnecessarily imposed on the vehicle when the steering wheel is operated instead of turning the vehicle. There is no.

  In another aspect of the vehicle control apparatus, the moment calculating means and the front and rear wheel actual steering angle calculating means are configured so that a yaw rate acting on the vehicle and a vehicle body slip angle of the vehicle become target values. The front and rear wheel actual steering angle calculation means calculates a ratio of the actual steering angle to be set for the rear wheel with respect to the actual steering angle of the front wheel. Under the condition that the yaw rate and vehicle body slip angle generated in the vehicle at the time of steering become target values, the moment to be applied to the vehicle and the actual steering angle ratio between the front and rear wheels to be set in the vehicle (hereinafter referred to as “ Also referred to as “front-rear wheel actual steering angle ratio”). By imposing the calculated moment and the front / rear wheel actual steering angle ratio on the vehicle, the vehicle at the time of steering cooperates with the steering wheel operation by the driver and is stable in a state where a desired yaw rate and vehicle body slip angle are generated. A swivel motion can be performed. Further, since the yaw rate acting on the vehicle and the generation of the vehicle body slip angle are not delayed with respect to the operation of the driver's steering wheel, the driver does not feel uncomfortable.

  In this case, preferably, the moment calculating means and the front and rear wheel actual steering angle calculating means are a ratio of the actual steering angle to be set for the rear wheel with respect to the moment M and the actual steering angle δf of the front wheel based on the equation (1). k and

Yr_ta is the target yaw rate of the vehicle, β_ta is the target vehicle body slip angle of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, Trf is the yaw rate time constant of the front wheels by steering, and Trr is the steering The rear wheel yaw rate time constant, Grm is the yaw rate gain by applying the moment, Trm is the yaw rate time constant by applying the moment, Gbf is the front body slip angle gain by steering, and Gbr is the rear body slip angle by steering. Gain, Tbf is the vehicle slip angle time constant of the front wheel by steering, Tbr is the vehicle slip angle time constant of the rear wheel by steering, Gbm is the vehicle slip angle gain by applying the moment, S is the Laplace operator, ωn is the vehicle's slip angle time constant The vehicle body natural frequency, ζ, is the vehicle body damping ratio of the vehicle. By using Expression (1), the moment to be applied to the vehicle and the actual front / rear wheel steering angle ratio can be calculated immediately.

  In another aspect of the vehicle control apparatus, the moment calculation means and the front and rear wheel actual steering angle calculation means calculate the yaw rate acting on the vehicle and the lateral acceleration acting on the vehicle to be target values. The front and rear wheel actual steering angle calculating means calculates the ratio of the actual steering angle to be set for the rear wheel to the actual steering angle of the front wheel. By imposing the calculated moment and the front / rear wheel actual steering angle ratio on the vehicle, the vehicle at the time of steering cooperates with the steering wheel operation by the driver and makes a stable turn with the desired yaw rate and lateral acceleration generated. Can do exercise. Further, since the vehicle body slip angle generated in the vehicle at the time of steering is not set to the target value, but the lateral acceleration is set to the target value, it can be realized without being restricted by constraints on the design of the vehicle.

  In this case, preferably, the moment calculating means and the front and rear wheel actual steering angle calculating means are a ratio of the actual steering angle to be set for the rear wheel with respect to the moment M and the actual steering angle δf of the front wheel based on the equation (2). k and

Yr_ta is the target yaw rate of the vehicle, gy_ta is the target lateral acceleration of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, Trf is the yaw rate time constant of the front wheels by steering, and Trr is by steering Rear wheel yaw rate time constant, Grm is yaw rate gain by applying moment, Trm is yaw rate time constant by applying moment, Ggyf is front wheel lateral acceleration gain by steering, Ggyr is rear wheel lateral acceleration gain by steering, T1f Is the first lateral acceleration time constant of the front wheels by steering, T2f is the second lateral acceleration time constant of the front wheels by steering, T1r is the first lateral acceleration time constant of the rear wheels by steering, and T2r is the first lateral acceleration time constant of the rear wheels by steering. The lateral acceleration time constant of 2, Ggym is the lateral acceleration gain by applying the moment, and Tgym is the lateral acceleration by applying the moment. The number, S is a Laplace operator, .omega.n the vehicle body natural frequency of the vehicle, zeta vehicle body damping ratio of the vehicle, and to. By using the equation (2), the moment to be applied to the vehicle and the front and rear wheel actual steering angle ratio can be calculated immediately.

  In another aspect of the vehicle control device, the moment calculating means and the front and rear wheel actual steering angle calculating means include a yaw rate acting on the vehicle, a vehicle body slip angle of the vehicle, and a lateral acceleration acting on the vehicle. The front and rear wheel actual steering angle calculation means calculates the ratio of the actual steering angle to be set for the front wheels to the actual steering angle corresponding to the steering wheel operation, and the actual steering angle corresponding to the steering wheel operation. The ratio of the actual steering angle to be set for the rear wheel with respect to the steering angle is calculated. When the vehicle is steered, the vehicle control device applies a moment to the vehicle, and with respect to the steering operation, the front wheel actual steering angle (hereinafter also simply referred to as “front wheel actual steering angle”) and the rear wheel The actual steering angle (hereinafter also simply referred to as “rear wheel actual steering angle”) is set independently. Further, in a vehicle at the time of steering to which a moment is applied, the moment, the actual front wheel steering angle, and the actual rear wheel steering angle are set under such conditions that the yaw rate, lateral acceleration, and vehicle body slip angle generated in the vehicle become target values. Is calculated. By imposing the calculated value on the vehicle, the vehicle at the time of steering cooperates with the operation of the steering wheel by the driver, and makes a stable turn with the desired yaw rate, lateral acceleration and vehicle body slip angle generated with high accuracy. Can do exercise.

  In this case, preferably, the moment calculating means and the front and rear wheel actual steering angle calculating means are set to the front wheel with respect to the moment M and the actual steering angle θ corresponding to the operation of the steering wheel based on the equation (3). An angle ratio kf and an actual steering angle ratio kr to be set for the rear wheel with respect to an actual steering angle θ corresponding to the operation of the steering wheel;

Yr_ta is the target yaw rate of the vehicle, β_ta is the target vehicle body slip angle of the vehicle, gy_ta is the target lateral acceleration of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, and Trf is by steering Front wheel yaw rate time constant, Trr is the rear wheel yaw rate time constant by steering, Grm is the yaw rate gain by applying the moment, Trm is the yaw rate time constant by applying the moment, Ggyf is the front wheel lateral acceleration gain by steering, and Ggyr is Lateral acceleration gain of the rear wheels by steering, T1f is the first lateral acceleration time constant of the front wheels by steering, T2f is the second lateral acceleration time constant of the front wheels by steering, and T1r is the first lateral acceleration of the rear wheels by steering Constant, T2r is the second lateral acceleration time constant of the rear wheel by steering, Ggym is the lateral acceleration gain by applying the moment, and Tgym is the front Lateral acceleration time constant by applying the moment, Gbf is the front body slip angle gain by steering the vehicle, Gbr is the rear body slip angle gain by steering, Tbf is the front body slip angle time constant by steering, and Tbr is The vehicle slip angle time constant of the rear wheel by steering, Gbm is the vehicle slip angle gain by applying the moment, S is the Laplace operator, ωn is the natural frequency of the vehicle body, and ζ is the vehicle body damping ratio of the vehicle. . By using Expression (3), the moment to be applied to the vehicle and the actual front / rear wheel steering angle ratio can be calculated immediately.

  In the above, preferably, the yaw rate gain Grf of the front wheel by the steering is calculated based on the equation (4),

The yaw rate gain Grr of the rear wheel by the steering is calculated based on the equation (5),

The lateral acceleration gain Ggyf of the front wheel by the steering is calculated based on the equation (6),

The lateral acceleration gain Ggyr of the rear wheel by the steering is calculated based on the equation (7),

The vehicle body slip angle gain Gbf of the front wheels by the steering is calculated based on the equation (8),

The vehicle slip angle gain Gbr of the rear wheel by the steering is calculated based on the equation (9),

The yaw rate gain Grm due to the application of the moment is calculated based on the equation (10),

The lateral acceleration gain Ggym by applying the moment is calculated based on the equation (11),

The vehicle body slip angle gain Gbm by the application of the moment is calculated based on the equation (12),

The yaw rate time constant Trf of the front wheel by the steering is calculated based on the equation (13),

The yaw rate time constant Trr of the rear wheel by the steering is calculated based on the equation (14),

The first lateral acceleration time constant T1f of the front wheel by the steering is calculated based on the equation (15),

The second lateral acceleration time constant T2r of the rear wheel by the steering is calculated based on the equation (16),

The first lateral acceleration time constant T1r of the rear wheel by the steering is calculated based on the equation (17),

The second lateral acceleration time constant T2r of the rear wheel by the steering is calculated based on the equation (18),

The vehicle body slip angle time constant Tbf of the front wheel by the steering is calculated based on the equation (19),

The rear wheel body slip angle time constant Tbr by the steering is calculated based on the equation (20),

The yaw rate time constant Trm by applying the moment is calculated based on the equation (21),

The lateral acceleration time constant Tgym by the application of the moment is calculated based on the equation (22),

The vehicle body natural frequency ωn of the vehicle is calculated based on the equation (23),

The vehicle body damping ratio ζ is calculated based on the equation (24),

m is the mass of the vehicle, V is the speed of the vehicle, I is the moment of inertia of the vehicle in the yaw direction, Kf is the cornering power of the front wheel of the vehicle, Kf is the cornering power of the rear wheel of the vehicle, and L is the vehicle. , Lf is the distance from the center of gravity of the vehicle to the drive shaft of the front wheel, Lr is the distance from the center of gravity of the vehicle to the drive shaft of the rear wheel, and kh is the stability factor of the vehicle. These values can be calculated immediately from the detection values from the sensors that detect the running state provided in the vehicle and the vehicle specification information.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Vehicle configuration]
First, a schematic configuration of a vehicle according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a plan view showing a schematic configuration of a vehicle 100 according to the present embodiment. A vehicle 100 shown in FIG. 1 is an application of the present invention to an FR vehicle (engine front and rear wheel drive system) of 4WD (4-wheel drive) and 4WS (4-wheel steering) specifications.

  The vehicle 100 mainly includes an engine 1, a torque converter 2, a transmission 3, a propeller shaft 4, a differential gear 5, left and right drive shafts 6L and 6R, and left and right drive shafts 9L. And 9R, left and right rear wheels 7L and 7R, left and right front wheels 10L and 10R, a handle 16, a steering shaft 18, a front wheel steering device 20, a rear wheel steering device 21, a battery 13, and an inverter 14 The left and right drive units 8L and 8R, a steering angle sensor 151, a vehicle speed sensor 152, and a vehicle control system 200 are provided. In the following description, regarding the components arranged symmetrically, “L” and “R” are added to the reference signs when left and right distinction is necessary, and “L” when right and left distinction is not necessary. , “R” is omitted. For example, when referring to the left and right drive units, “drive unit 8” is described, and when referring to the left motor, “drive unit 8L” is described.

  The engine 1 is an internal combustion engine that generates power by exploding an air-fuel mixture in a combustion chamber. The reciprocating motion of the piston due to the combustion of the air-fuel mixture in the combustion chamber is converted into the rotational motion of the crankshaft (not shown) via the connecting rod (not shown). The crankshaft transmits power to the rear wheel 7 via the torque converter 2, the transmission 3, the propeller shaft 4, the differential gear 5, and the drive shaft 6.

  The torque converter 2 is provided between the engine 1 and the transmission 3. The torque converter 2 uses a working fluid such as oil to function as a clutch for intermittently transmitting the rotational torque output from the engine 1 to the transmission 3 and to transmit the rotational torque to the transmission 3 by increasing the rotational torque. It has the function to do.

  The transmission 3 is provided between the torque converter 2 and the propeller shaft 4 and includes a plurality of gears (planetary gears) corresponding to each of the four forward speeds (first speed to fourth speed) and the first reverse speed. . The transmission 3 operates a hydraulic control device (not shown) based on a command signal from the ECU, thereby performing a shift operation from a low speed to a high speed (shift up) or a shift from a high speed to a low speed (shift down). )I do.

  The propeller shaft 4 is a propulsion shaft that is provided between the transmission 3 and the differential gear 5 and transmits the driving force obtained from the engine 1 to the rear wheel 7 side.

  The differential gear 5 is composed of a combination of a plurality of bevel gears, and is a gear that adjusts the rotational speeds of the inner and outer wheels when the vehicle turns. Specifically, when the vehicle 100 travels on a straight road, the differential gear 5 rotates the left and right rear wheels 7 at the same speed. On the other hand, when the vehicle 100 performs a turning motion, a difference in rotational speed between the left and right rear wheels 7 is generated, so that the differential gear 5 adjusts the rotational speed of the differential gear 5 to enable a smooth turning motion.

  The drive shaft 6 is an axle that is rotatably connected to the left and right rear wheels 7. The drive shaft 6 is rotated by a driving force from the engine 1 and transmits power to the rear wheel 7.

  The drive unit 8 includes, for example, an electric motor such as a permanent magnet type synchronous motor and a speed reducer, and is provided at a position for driving the left and right front wheels. A power cable 71 connected to the inverter 14 is connected to each of the drive units 8R and 8L, and a voltage signal is supplied. Then, the drive units 8R and 8L are driven based on the voltage signal.

  The drive shaft 9 is an axle that is rotatably connected to the left and right front wheels 10 independently on the left and right. The drive shafts 9 are output shafts of the left and right drive units 8, respectively, and are given drive force independently from each drive unit 8. That is, the left and right front wheels 10 are driven independently by the left and right drive units 8.

  The handle 16 is operated in order for the driver to turn the vehicle 100. The steering wheel 16 transmits the steering force of the driver. A steering shaft 17 is connected to the center portion of the handle 16. That is, when the driver steers the handle 16, the steering shaft 17 also rotates. Further, the steering shaft 17 is connected to the front wheel steering device 20.

  The front wheel steering device 20 is driven by the steering force transmitted from the steering shaft 17 and the control signal 80 from the vehicle control system 200. The front wheel steering device 20 is connected to the drive shaft 9, and the angle of the front wheel 10 with respect to the vehicle body is changed by driving the front wheel steering device 20.

  The rear wheel steering device 21 is driven by a control signal 81 from the vehicle control device 200. The rear wheel control device 21 is connected to the drive shaft 6, and the angle of the rear wheel 7 with respect to the vehicle body is changed by driving the rear wheel steering device 21.

  In addition, the vehicle 100 is provided with various sensors that detect the traveling state of the vehicle 100 and the like. In FIG. 1, a steering angle sensor 151 and a vehicle speed sensor 152 are shown as sensors mainly used for control of the vehicle 100 according to the present embodiment. The steering angle sensor 151 is a sensor that detects an actual steering angle (that is, “actual steering angle”) corresponding to the input of the handle 16. The vehicle speed sensor 152 is a sensor that detects the traveling speed of the vehicle 100 (that is, “vehicle speed V”).

  An output signal 74 of the steering angle sensor 18 (that is, an electric signal corresponding to “actual steering angle”) is supplied to the vehicle control system 200. Further, an output signal 75 of the vehicle speed sensor 19 (that is, an electric signal corresponding to “vehicle speed”) is also supplied to the vehicle control system 200.

  The battery 13 is a secondary battery such as a lead storage battery or a nickel metal hydride battery, and exchanges power with the inverter 14 via the power cable 70.

  The inverter 14 is a device that mainly controls the amount of generated power, and is connected to the battery 13 through the power cable 70 and the left and right drive units 8 through the power cable 71. Further, the inverter 14 receives a torque control signal 72 from the vehicle control system 200. When the inverter 14 is supplied with electric power from the battery 13, it converts it into a three-phase AC voltage suitable for driving the left and right drive units 8. The inverter 14 supplies the converted three-phase AC voltage to the left and right drive units 8 to drive the left and right drive units 8 independently. The drive control of the left and right drive units 8 by the inverter 14 is performed based on the torque control signal 72 from the vehicle control system 200. Further, when the inverter 14 receives supply of electric power generated from the drive unit 8 when the vehicle decelerates, the inverter 14 converts the electric power into a DC voltage suitable for charging the battery 12, and the power of the battery 13 is changed through the power cable 70. Charge the battery.

  The vehicle control system 200 is a system that drives the left and right front wheels 10 independently and steers the front wheels 10 and the rear wheels 7 independently so that the vehicle 100 at the time of steering performs a desired vehicle behavior. The vehicle control system 200 controls the vehicle 100 during steering so that a yaw rate, a lateral acceleration, and a vehicle body slip angle that are appropriate for the steering of the driver are generated. Specifically, the vehicle control system 200 calculates the moment to be applied to the vehicle 100 and the actual steering angle to be set on the front wheels 10 and the rear wheels 7. Based on the calculated moment, the output torques of the left and right drive units 8L and 8R are determined, and a torque control signal 72 corresponding to the output torque is output to the inverter 14. Further, the actual steering angle of the front wheel 10 is determined based on the calculated actual steering angle ratio to be set for the front wheel 10, and a control signal 80 corresponding to the actual steering angle is output to the front wheel steering device 20. Similarly, the actual steering angle of the rear wheel 7 is determined based on the calculated actual steering angle ratio to be set for the rear wheel 7, and a control signal 81 corresponding to the actual steering angle is output to the front wheel steering device 20. The vehicle control system 200 may be provided in an ECU (Engine Control Unit) (not shown).

[First Embodiment]
Below, the concept regarding the control of the vehicle which concerns on 1st Embodiment of this invention is demonstrated using FIG.2 and FIG.3.

  First, with reference to FIG. 2, a delay in vehicle behavior that occurs when the vehicle 100 is steered will be described. In FIG. 2, for convenience of description, the description will proceed from the state at the start of steering of the vehicle 100.

  FIG. 2A shows a state when the vehicle 100 starts a turning motion (that is, a state when the driver starts steering to turn the vehicle). The turning of the vehicle 100 is performed by the driver turning the handle 16. In this case, since the road is curved leftward, the vehicle 100 has to travel in the direction of the arrow 40, so the driver turns the handle 16 in the direction indicated by the arrow 42 (ie, counterclockwise). As shown in the figure, the vehicle 100 has not yet behaved with respect to steering.

  Next, FIG. 2B shows a state of the vehicle 100 after a predetermined time has elapsed from FIG. FIG. 2 (b) is a diagram showing the middle of the turning motion of the vehicle 100. At this time, a yaw rate r, a lateral acceleration gy, and a vehicle body slip angle β are generated in the vehicle 100. The behavior generated by these vehicles 100 corresponds to what should have occurred when the driver steers the steering wheel 16. That is, it can be seen that the behavior of the vehicle 100 is delayed with respect to the steering by the driver. Therefore, the turning performance of the vehicle may be reduced. In addition, since the driver feels uncomfortable at the time of steering, the vehicle 100 may not be able to make a stable turn because the driver cannot operate the steering wheel 16 appropriately.

  Therefore, in the embodiment of the present invention, when the vehicle 100 is steered, a moment is applied to the vehicle 100 and the actual steering angles of the front and rear wheels are set separately. This is specifically shown in FIG. When the driver operates the steering wheel 16, a moment M is applied to the vehicle 100, and the actual steering angles of the front and rear wheels are set separately (the actual steering angle of the front wheels is δf, and the steering angle of the rear wheels is set). δr). As a result, the vehicle 100 at the time of steering can perform an appropriate behavior in cooperation with the driver's operation of the handle 16. That is, the generation of the yaw rate r, the lateral acceleration gy, and the vehicle body slip angle β is not delayed with respect to the steering. Therefore, the turning performance of the vehicle 100 is improved. In addition, the driver does not feel uncomfortable when operating the handle 16, and can appropriately operate the handle 16, so that the vehicle 100 can also make a stable turn.

(Processing in the vehicle control system)
Next, specific processing in the vehicle control system 200a according to the first embodiment will be described with reference to FIG. The vehicle control system 200a is a system that drives the left and right front wheels 10 independently and also steers the front wheels 10 and the rear wheels 7 independently so that the vehicle 100 during steering performs a desired vehicle behavior.

  FIG. 4 shows the configuration of the vehicle control system 200a according to the first embodiment. The vehicle control system 200a mainly includes a vehicle specification information storage unit 210, a vehicle state quantity calculation unit 220, a moment calculation unit 230, a front and rear wheel actual steering angle ratio calculation unit 232, and a controller unit 240.

  A signal 250 indicating the running state of the vehicle 100 is input from the various sensors 150 to the vehicle control system 200a. The vehicle control system 200a calculates the moment M and the front and rear wheel actual steering angle ratio k based on the input signals of the various sensors 150 and the like. Further, the vehicle control system 200 a derives the torque control signal 72 based on the moment M, and outputs the torque control signal 72 to the inverter 14. Similarly, the vehicle control system 200 a derives a control signal 81 corresponding to the actual steering angle based on the front and rear wheel actual steering angle ratio k, and outputs the control signal 81 to the rear wheel steering device 21 as the control signal 81.

  The various sensors 150 mainly include a steering angle sensor 151 that detects an actual steering angle when the steering wheel 16 is operated by the driver, a vehicle speed sensor 152 that detects a traveling speed of the vehicle, and when the accelerator pedal is depressed by the driver. An accelerator opening sensor 153 for detecting the amount of depression of the vehicle, an acceleration sensor 154 for detecting the longitudinal acceleration and the lateral acceleration of the vehicle 100, a yaw rate sensor 155 for detecting the yaw rate of the vehicle 100 during turning, and the like. The values detected by the various sensors 150 are output to the vehicle state quantity calculation unit 220 described later.

  The vehicle specification information storage unit 210 mainly includes a yaw moment of inertia (hereinafter simply referred to as “moment of inertia”) I, a mass m, a wheel base L, and a distance Lf from the center of gravity to the drive shaft 9 of the front wheel 10 in the vehicle 100. The distance Lr from the center of gravity to the drive shaft 6 of the rear wheel 7, the cornering power Kf of the front wheel 10 (representing the cornering power for one wheel), the cornering power Kf of the rear wheel 7 (representing the cornering power for one wheel) The stability factor kh indicating the static stability of the vehicle is stored. These pieces of information are constants that are not affected by the running state of the vehicle. The vehicle specification information storage unit 210 outputs these stored values to the vehicle state quantity calculation unit 220.

  The vehicle state quantity calculation unit 220 obtains a value (hereinafter referred to as “vehicle state quantity”) obtained based on the signal 250 input from the various sensors 150 and the signal 252 input from the vehicle specification information storage unit 210. ) Is calculated. Specifically, the vehicle state quantity calculation unit 220 includes a target yaw rate calculation unit 221, a target slip angle calculation unit 224, a gain calculation unit 226, and a time constant calculation unit 228. The target yaw rate calculation unit 221 calculates the yaw rate that the vehicle 100 should follow. The target vehicle body slip angle calculation unit 224 calculates the vehicle body slip angle that the vehicle 100 should take. The gain calculation unit 226 and the time constant calculation unit 228 calculate a coefficient in an arithmetic expression used when calculating the moment M and the front and rear wheel actual steering angle ratio k. The vehicle state quantity calculated by the vehicle state quantity calculation unit 220 is output to the moment calculation unit 230 and the front and rear wheel actual steering angle ratio calculation unit 232. An arithmetic expression for calculating the above-described vehicle state quantity will be described later.

  The moment calculation unit 230 acquires a signal 254 indicating the vehicle state quantity from the vehicle state quantity calculation unit 220. Then, moment calculation unit 230 calculates moment M to be applied to vehicle 100 based on this signal 254. This moment M is calculated based on an arithmetic expression stored in a moment calculator 230 or a memory (not shown) in the vehicle control system 200a. The calculated moment M is output to the controller unit 240.

  The front and rear wheel actual steering angle ratio calculation unit 232 acquires a signal 256 indicating the vehicle state quantity from the vehicle state quantity calculation unit 220. Then, the front and rear wheel actual steering angle ratio calculation unit 232 calculates a ratio k (that is, “front and rear wheel actual steering angle ratio”) between the front wheel actual steering angle δf and the rear wheel actual steering angle δr to be set in the vehicle 100. To do. In the first embodiment, the actual steering angle δf of the front wheels is set to be the same as the actual steering angle δ corresponding to the operation of the steering wheel 16 (that is, δf = δ). Therefore, the front and rear wheel actual steering angle ratio k determines the rear wheel actual steering angle δr (that is, δr = kδf = kδ). The front and rear wheel actual steering angle ratio k is calculated based on an arithmetic expression stored in a front and rear wheel actual steering angle ratio calculating unit 232 or a memory (not shown) in the vehicle control system 200a. The calculated front and rear wheel actual steering angle ratio k is output to the controller unit 240.

  The controller unit 240 determines respective output torques in the left and right drive units 8L and 8R so that the vehicle 100 can actually generate the input moment M. Then, the controller unit 214 outputs a torque control signal 72 corresponding to the determined output torque to the inverter 14. Similarly, the controller unit 240 outputs a control signal 81 to the rear wheel steering device 21 so that the rear wheel 7 can realize the actual steering angle δr determined from the inputted front and rear wheel actual steering angle ratio k.

  By imposing the moment M and the front / rear wheel actual steering angle ratio k calculated as described above on the vehicle 100 during steering, the followability of the yaw rate with respect to steering is improved, and the vehicle body slip angle is also maintained at a desired value. Is done. As a result, the vehicle 100 at the time of steering can perform an appropriate behavior in cooperation with the driver's operation of the handle 16. Therefore, the turning performance of the vehicle 100 is improved. In addition, the driver does not feel uncomfortable when operating the handle 16.

  Note that the vehicle control system 200a starts the process for calculating the moment M and the front and rear wheel actual steering angle ratio k when the steering of the steering wheel 16 from the driver is performed while satisfying a predetermined condition. Examples of the predetermined condition include a case where the speed at which the driver's handle 16 is turned is equal to or higher than a predetermined speed, and a case where the angle at which the driver's handle 16 is turned exceeds a predetermined angle. The moment calculation unit 230 and the front and rear wheel actual steering angle ratio calculation unit 232 receive the latest signal every predetermined time, and calculate the moment M and the front and rear wheel actual steering angle ratio k each time. Further, the moment calculation unit 230 and the front and rear wheel actual steering angle ratio calculation unit 232 perform processing when the driver's steering reaches a steady state (that is, when the speed at which the driver's steering wheel 16 is turned to zero). Shall be terminated. That is, when the steering of the vehicle 100 becomes steady, the application of the moment M to the vehicle 100 and the setting of separate actual steering angles for the front and rear wheels are terminated.

(Method of calculating moment and front / rear wheel actual steering angle ratio)
Hereinafter, a method of calculating the moment M applied to the vehicle 100 and the front and rear wheel actual steering angle ratio k set in the vehicle 100 will be described. The moment M and the front and rear wheel actual steering angle ratio k are calculated by the moment calculation unit 230 and the front and rear wheel actual steering angle ratio calculation unit 232 in the vehicle control system 200a, respectively.

  In general, the response of the yaw rate rδ and the vehicle body slip angle βδ to the steering of the vehicle 100 (that is, the yaw rate and the vehicle body slip angle generated by the steering of the vehicle 100) are expressed by equations (25) and (26), respectively. .

Expressions (25) and (26) are expressions obtained by performing Laplace transform on an expression expressed as a function of time (t). Therefore, in Expressions (25) and (26), S is a Laplace operator, and is expressed as a function of the Laplace operator S. Further, δf represents the actual steering angle of the front wheel 10, δr represents the actual steering angle of the rear wheel 7, and δr = kδf (k: front and rear wheel actual steering angle ratio) is satisfied. It should be noted that the equations (25) and (26) indicate the yaw rate and vehicle body slip angle generated in the vehicle 100 only by steering in a situation where no moment is applied to the vehicle 100 by a motor or the like. .

  In equation (25), Grf is the yaw rate gain of the front wheel 10 by steering, Grr is the yaw rate gain of the rear wheel 7 by steering, Trf is the yaw rate time constant of the front wheel 10 by steering, Trr is the yaw rate time constant of the rear wheel 7 by steering, ωn represents the vehicle natural frequency, and ζ represents the yaw damping ratio, which are assumed to satisfy the equations (27) and (32), respectively. These values can be obtained from the traveling state of the vehicle 100 and the like, and correspond to the coefficients of the equation (25) expressed as a function of the Laplace operator S.

In equations (27) to (32), m is the mass of the vehicle 100, L is the wheel base, Lf is the distance from the center of gravity of the vehicle 100 to the drive shaft 9 of the front wheel 10, and Lr is the center of gravity of the vehicle 100 to the rear wheel. 7 is the distance to the drive shaft 6, Kf is the cornering power of the front wheel 10 (for one wheel), Kf is the cornering power of the rear wheel 7 (for one wheel), I is the moment of inertia of the vehicle 100, V is the vehicle speed, and kh is A stability factor indicating the static stability of the vehicle 100 is shown. The meanings indicated by these symbols are used in the following as well.

  In equation (26), Gbf is a vehicle body slip angle gain of the front wheel 10 by steering, Gbr is a vehicle body slip angle gain of the rear wheel 7 by steering, Tbf is a vehicle body slip angle time constant of the front wheel 10 by steering, and Tbr is by steering. The vehicle body slip angle time constant of the rear wheel 7 is shown, and the expressions (33) to (36) are satisfied, respectively. These values can be obtained from the traveling state of the vehicle 100 and the like, and correspond to the coefficients of the equation (26) expressed as a function of the Laplace operator S.

Note that the vehicle natural frequency ωn and the yaw damping ratio ζ in the equation (26) satisfy the equations (31) and (32), respectively.

  The yaw rate gains Grf and Grr due to the steering and the vehicle body slip angle gains Gbf and Gb due to the steering are respectively calculated by the gain calculation unit 226 of the vehicle state quantity calculation unit 220 in the vehicle control system 200a. Further, the yaw rate time constants Trf and Trr due to steering and the vehicle body slip angle gains Tbf and Tbr due to steering are calculated by the time constant calculation unit 228 in the vehicle state quantity calculation unit 220, respectively.

  Here, the force etc. which act on the vehicle 100 when the vehicle 100 is turning will be described with reference to FIG. The vehicle 100 travels at a speed V, and in a state of an actual steering angle δ (actual steering angle corresponding to steering of the handle 16), the vehicle 100 performs a turning motion with a vehicle body slip angle β with respect to the traveling direction indicated by the arrow 45. doing. At this time, since the yaw rate r is generated in the vehicle 100 and the vehicle body slip angle β is generated, the cornering force Ff works on the front wheel 10 and the cornering force Fr works on the rear wheel 7. As described above, in this embodiment, the moment M indicated by the dotted arrow is applied to the vehicle 100 during steering, the actual steering angle of the front wheels 10 is set to δf, and the actual steering angle of the rear wheels 7 is set. It is set to δr. In FIG. 5, for the sake of simplicity, the actual steering angles of the left and right wheels are assumed to be the same.

  When a force (including moment M applied to the vehicle 100) as shown in FIG. 5 is acting on the vehicle 100, the equation of motion in the lateral direction is shown in Equation (37), and the moment equation of motion (around the center of gravity G) Equation (38) shows the equation of moment motion.

As shown in Expression (38), the vehicle 100 is given a moment M according to the present embodiment.

  When Laplace transform is performed on the equation (37) representing the equation of motion in the lateral direction and the equation (38) representing the equation of moment equation, and the actual steering angle δ = 0, the yaw rate r and the vehicle body slip angle β are solved. Equations (39) and (40) are obtained. Here, the reason for setting the actual steering angle δ = 0 is to calculate the yaw rate r and the vehicle body slip angle β when only the moment M is applied to the vehicle 100.

Expressions (39) and (40) are expressed as functions of the Laplace operator S. In Expression (39), rm indicates the yaw rate when the moment M is applied, and in Expression (40), βm indicates the vehicle body slip angle when the moment M is applied. In this way, the yaw rate rm and the vehicle body slip angle βm when the moment M is applied can be obtained.

  In the equation (39), the yaw rate gain Grm when the moment M is applied is expressed by the equation (41), and the yaw rate time constant Trm when the moment M is applied is expressed by the equation (42). These values can be obtained from the traveling state of the vehicle 100 and the like, and correspond to the coefficients of the equation (39) expressed as a function of the Laplace operator S.

Further, in the equation (40), the vehicle body slip angle gain Gbm when the moment M is applied is represented by the equation (43). The vehicle body slip angle gain Gbm can be obtained from the traveling state of the vehicle 100 and the like, and corresponds to the coefficient of the equation (40) expressed as a function of the Laplace operator S.

  As described above, the yaw rate rδ shown in the equation (25) and the vehicle body slip angle βδ shown in the equation (26) are generated in the vehicle 100 when steered. Further, the yaw rate rm shown in the equation (39) and the vehicle body slip angle βm shown in the equation (40) are generated in the vehicle 100 when the moment M is applied. From the above, the yaw rate r ′ generated in the vehicle 100 when the moment M is simultaneously applied when the vehicle 100 is steered can be expressed as in Expression (44).

The yaw rate r ′ shown in the equation (44) is expressed by adding the yaw rate rδ obtained by steering the vehicle 100 shown in the equation (25) and the yaw rate rm when the moment M shown in the equation (39) is applied. .

  On the other hand, the vehicle body slip angle β ′ generated in the vehicle 100 when the moment M is simultaneously applied when the vehicle 100 is steered can be expressed as in Expression (45).

The vehicle body slip angle β ′ shown in Expression (45) is the vehicle body slip angle βδ obtained by steering the vehicle 100 shown in Expression (26) and the vehicle body slip angle βm when the moment M shown in Expression (40) is applied. Expressed as an addition.

  In the first embodiment, the yaw rate r ′ generated in the vehicle 100 follows the target yaw rate Yr_ta in order to improve the stability of the turning motion of the vehicle 100 steered by the driver. In addition, the vehicle body slip angle β ′ generated in the vehicle 100 is maintained at the target vehicle body slip angle β_ta. That is, the yaw rate r ′ and the vehicle body slip angle β ′ generated in the vehicle 100 when the moment M is simultaneously applied when the vehicle 100 is steered must satisfy the conditions shown in the equations (46) and (47), respectively. is there.

Substituting equation (44) into equation (46) yields equation (48). Further, when Expression (45) is substituted into Expression (47), Expression (49) is obtained.

Expression (48) is an expression showing that the yaw rate r 'generated in the vehicle 100 to which the moment M is applied when being steered is matched with the target yaw rate Yr_ta. Further, the equation (49) is an equation showing that the vehicle body slip angle β ′ generated in the vehicle 100 to which the moment M is applied when being steered is matched with the target vehicle body slip angle β_ta.

  When Equation (48) and Equation (49) are combined and solved for the front and rear wheel actual steering angle ratio k and moment M, Equation (50) is obtained.

  From the equation (50), the front-rear wheel actual steering angle ratio k is the target yaw rate Yr_ta, the yaw rate gains Grf and Grr by steering, the yaw rate time constants Trf and Trr by steering, and the yaw rate gain Grm and moment M by applying moment M. Is calculated using the yaw rate time constant Trm by the application of the vehicle body, the vehicle body slip angle gain Gbr of the rear wheel 7 by the steering, the vehicle body slip angle time constant Tbr of the rear wheel 7 by the steering, and the vehicle body slip angle Gbm by the application of the moment M. Is done.

  Further, from the equation (50), the moment M is the target vehicle body slip angle β_ta, the yaw rate gain Grr of the front wheel 10 by steering, the yaw rate time constant Trr of the front wheel 10 by steering, the yaw rate gain Grm and the moment by applying the moment M. The yaw rate time constant Trm by applying M, the vehicle body slip angle gains Gbf and Gbr by steering, the vehicle body slip angle time constants Tbf and Tbr by steering, and the vehicle body slip angle Gbm by applying moment M are calculated.

  As described above, in the first embodiment of the present invention, when the vehicle 100 is steered, a moment is applied to the vehicle 100 and the actual steering angles of the front and rear wheels are set separately. Further, in the vehicle 100 at the time of steering to which the moment M is applied, the yaw rate r ′ and the vehicle body slip angle β ′ generated in the vehicle 100 are calculated under the conditions such that the target values are obtained. Thus, the vehicle 100 at the time of steering can perform a stable turning motion in a state where a desired yaw rate and vehicle body slip angle are generated in cooperation with the operation of the steering wheel 16 by the driver. Further, since the yaw rate acting on the vehicle and the generation of the vehicle body slip angle are not delayed with respect to the operation of the driver's handle 16, the driver does not feel uncomfortable.

[Second Embodiment]
Below, control of the vehicle concerning a 2nd embodiment of the present invention is explained.

  Also in the second embodiment, the moment M is applied to the vehicle 100 during steering by the driver, and the actual steering angle is set separately for the front wheels 10 and the rear wheels 7. However, in the second embodiment, the moment M to be set in the vehicle 100 and the actual front and rear wheel steering angle ratio k are calculated so that the yaw rate and lateral acceleration generated in the vehicle 100 become target values. This is because, as shown in the first embodiment, the vehicle body slip angle is maintained at the target value because it may be difficult to realize due to design restrictions of the vehicle 100.

(Processing in the vehicle control system)
Next, specific processing in the vehicle control system 200b according to the second embodiment will be described with reference to FIG.

  The vehicle control system 200b is a system that drives the left and right front wheels 10 independently and steers the front wheels 10 and the rear wheels 7 independently so that the vehicle 100 during steering performs a desired vehicle behavior.

  The vehicle control system 200b acquires the input signal 250 from the various sensors 150, and changes the angle of the rear wheel 7 and the torque control signal 72 for applying a moment to the vehicle 100 to the inverter 14 and the rear wheel steering device 21. A control signal 81 is output. The various sensors 150, the inverter 14, and the rear wheel steering device 21 are the same as those shown in the first embodiment.

  The vehicle control system 200b has the same basic configuration and processing as those described in the first embodiment. That is, the vehicle specification information storage unit 210, the vehicle state quantity calculation unit 220, the moment calculation unit 230, the front and rear wheel actual steering angle ratio calculation unit 232, and the controller unit 240 are configured. However, the vehicle state quantity calculation unit 220 is different from that shown in the first embodiment in that the vehicle state quantity calculation unit 220 includes a target lateral acceleration calculation unit 225 instead of the target vehicle body slip angle calculation unit 224.

  The target lateral acceleration calculation unit 225 calculates the lateral acceleration that the vehicle 100 should generate based on values input from the various sensors 150 and values input from the vehicle specification information storage unit 210. Therefore, the moment calculator 230 and the front and rear wheel actual steering angle calculator 232 calculate the moment M and the front and rear wheel actual steering angle ratio k based on the target lateral acceleration calculated by the target lateral acceleration calculator 225.

  Thus, by imposing the moment M and the front and rear wheel actual steering angle ratio k calculated by the vehicle body control system 200b according to the second embodiment on the vehicle 100 at the time of steering, the followability of the yaw rate with respect to steering is improved. Further, the lateral acceleration is also maintained at a desired value. As a result, the vehicle 100 during steering can perform an appropriate vehicle behavior in cooperation with the driver's operation of the handle 16. Further, since the moment M and the front and rear wheel actual steering angle ratio k are calculated so that the lateral acceleration becomes the target value, an appropriate vehicle behavior can be realized regardless of the characteristics of the vehicle 100.

(Method of calculating moment and front / rear wheel actual steering angle ratio)
Hereinafter, a method for calculating the moment M applied to the vehicle 100 and the front and rear wheel actual steering angle ratio k set in the vehicle 100 according to the second embodiment will be described. The moment M and the front and rear wheel actual steering angle ratio k are calculated by the moment calculation unit 230 and the front and rear wheel actual steering angle ratio calculation unit 232 in the vehicle control system 200, respectively.

  In general, the yaw rate rδ with respect to the steering of the vehicle 100 is expressed by the above equation (25), and the response of the lateral acceleration gyδ with respect to the steering is expressed by the equation (51). Also in the second embodiment, the actual steering angle δf of the front wheel 10 and the actual steering angle δr of the rear wheel 7 satisfy the relationship δr = kδf, and the actual steering angle δf of the front wheel 10 corresponds to the operation of the steering wheel 16. It is assumed that it matches the actual steering angle δ.

  In equation (51), Ggyf is the lateral acceleration gain of the front wheel 10 by steering, Ggyr is the lateral acceleration gain of the rear wheel 7 by steering, T1f is the first lateral acceleration time constant of the front wheel 10 by steering, and T2f is the front wheel 10 by steering. , The second lateral acceleration time constant, T1r represents the first lateral acceleration time constant of the rear wheel 7 by steering, and T2r represents the second lateral acceleration time constant of the rear wheel 7 by steering. Satisfies the solstice (57). These values can be obtained from the traveling state of the vehicle 100 and the like, and correspond to the coefficients of the equation (51) expressed as a function of the Laplace operator S.

  The lateral acceleration gains Ggyf and Ggyr by the above steering are calculated by the gain calculation unit 226 included in the vehicle state quantity calculation unit 220 in the vehicle control system 200. Further, the time constant calculation unit 228 in the vehicle state quantity calculation unit 220 calculates the lateral acceleration time constants T1f, T2f, T1r, and T2r by steering.

  Next, it is assumed that the force shown in FIG. 5 is applied to the vehicle 100, and the equation of motion of the vehicle 100 is expressed by Expression (37) and Expression (38). When the equation (37) representing the equation of motion in the lateral direction and the equation (38) representing the equation of moment equation are Laplace transformed to solve the lateral acceleration gy under the actual steering angle δ = 0, the equation (58) is obtained. can get.

In Expression (58), gym represents the lateral acceleration when the moment M is applied. In the equation (58), the lateral acceleration gain Ggym when the moment M is applied is expressed by the equation (59), and the lateral acceleration time constant Tgym when the moment M is applied is expressed by the equation (59). These values can be obtained from the traveling state of the vehicle 100 and the like, and correspond to the coefficients of the equation (58) expressed as a function of the Laplace operator S.

  When the vehicle is steered, the yaw rate rδ shown in the equation (25) and the lateral acceleration gyδ shown in the equation (51) are generated. Further, in the vehicle 100 when the moment M is applied, the yaw rate rm shown in the equation (39) and the lateral acceleration gym shown in the equation (58) are generated. Therefore, the yaw rate r 'generated in the vehicle 100 when the moment M is simultaneously applied when the vehicle 100 is steered can be expressed as the equation (44) as described above. Further, the lateral acceleration gy 'generated in the vehicle 100 when the moment M is simultaneously applied when the vehicle 100 is steered can be expressed as in Expression (61).

The lateral acceleration gy ′ shown in the equation (61) is obtained by adding the lateral acceleration gyδ due to the steering of the vehicle 100 shown in the equation (51) and the lateral acceleration gym when the moment M shown in the equation (58) is applied. Is.

  In the second embodiment, the yaw rate r ′ generated in the vehicle 100 is the target yaw rate Yr_ta so that the vehicle 100 steered by the driver can perform the turning motion stably regardless of the characteristics of the vehicle 100. The lateral acceleration gy ′ generated in the vehicle 100 is maintained at the target lateral acceleration gy_ta. That is, the yaw rate r 'generated when the moment M is applied when the vehicle 100 is steered must satisfy the above-described equation (46), and the lateral acceleration gy' must satisfy the equation (62).

Substituting equation (44) into equation (46) yields equation (48), and substituting equation (61) into equation (62) yields equation (63).

Expression (48) is an expression showing that the yaw rate r 'generated in the vehicle 100 to which the moment M is applied when being steered is matched with the target yaw rate Yr_ta. Expression (63) is an expression showing that the lateral acceleration gy 'generated in the vehicle 100 to which the moment M is applied when being steered is made to coincide with the target vehicle body slip angle gy_ta.

  When equations (48) and (63) are combined and solved for front and rear wheel actual steering angle ratio k and moment M, equation (64) is obtained.

  From the equation (64), the front-rear wheel actual steering angle ratio k is the target yaw rate Yr_ta, the yaw rate gains Grf and Grr by steering, the yaw rate time constants Trf and Trr by steering, and the yaw rate gain Grm and moment M by applying moment M. The yaw rate time constant Trm by the application of the steering wheel, the lateral acceleration gain Ggyr of the rear wheel 7 by the steering, the lateral acceleration time constants T1r and T2r of the rear wheel 7 by the steering, the lateral acceleration gain Ggym by the application of the moment M, and the application of the moment M Is calculated using the lateral acceleration time constant Tgym.

  Further, from the equation (64), the moment M is the target lateral acceleration gy_ta, the yaw rate gain Grr of the rear wheel 7 by steering, the yaw rate time constant Trr of the rear wheel 7 by steering, the yaw rate gain Grm by the application of the moment M, Yaw rate time constant Trm by applying moment M, lateral acceleration gains Ggyr and Ggyf by steering, lateral acceleration time constants T1f, T2f, T1r, and T2r by steering, lateral acceleration gain Ggym by applying moment M, and applying moment M Is calculated using the lateral acceleration time constant Tgym.

  As described above, in the second embodiment of the present invention, when the vehicle 100 is steered, a moment is applied to the vehicle 100 and the actual steering angles of the front and rear wheels are set separately. Further, in the vehicle 100 during steering to which the moment M is applied, the yaw rate r ′ and the lateral acceleration gy ′ generated in the vehicle 100 are calculated under the conditions such that the target values are obtained. Thus, the vehicle 100 during steering can perform a stable turning motion in a state where a desired yaw rate and lateral acceleration are generated in cooperation with the operation of the steering wheel 16 by the driver. Further, since the generation of the yaw rate and lateral acceleration acting on the vehicle is not delayed with respect to the operation of the driver's handle 16, the driver does not feel uncomfortable. Further, the above control by the vehicle control system 200 does not set the vehicle body slip angle generated in the vehicle 100 at the time of steering to the target value, but sets the lateral acceleration to the target value. This can be realized without being constrained by constraints.

[Third Embodiment]
Below, control of the vehicle concerning a 3rd embodiment of the present invention is explained.

  Also in the third embodiment, the moment M is applied to the vehicle 100 during steering by the driver, and the actual steering angle is set separately for the front wheels 10 and the rear wheels 7. However, in the third embodiment, the moment M to be set in the vehicle 100 and the front and rear wheel actual steering angle ratio k are set so that the yaw rate, lateral acceleration, and vehicle body slip angle generated in the vehicle 100 become target values. calculate.

  Further, in the first embodiment and the second embodiment, the actual steering angle δf of the front wheel 10 is set to the actual steering angle δ corresponding to the operation of the handle 16, and only the actual steering angle δr of the rear wheel 7 is actually steered from the front and rear wheels. Although the angle ratio k is set, in the third embodiment, the actual steering angle δf of the front wheels 10 is also made variable with respect to the input from the steering wheel 16. That is, the actual steering angle δf of the front wheels 10 is independently controlled using the actual steering angle δ corresponding to the operation of the steering wheel 16.

(Processing in the vehicle control system)
Next, specific processing in the vehicle control system 200c according to the third embodiment will be described with reference to FIG.

  The vehicle control system 200c is a system that drives the left and right front wheels 10 independently and steers the front wheels 10 and the rear wheels 7 independently so that the vehicle 100 at the time of steering performs a desired vehicle behavior.

  The vehicle control system 200c acquires the input signal 250 from the various sensors 150, and changes the angle of the front wheel 10 and the torque control signal 72 for applying a moment to the vehicle 100 to the inverter 14 and the rear wheel steering device 21. Control signal 80 and a control signal 81 for changing the angle of the rear wheel 7 are output. Various sensors 150, the inverter 14, and the rear wheel steering device 21 are the same as those described above.

  The vehicle control system 200c includes a vehicle specification information storage unit 210, a vehicle state quantity calculation unit 220, a moment calculation unit 230, a front wheel actual steering angle ratio calculation unit 233, a rear wheel actual steering angle ratio calculation unit 234, a controller The unit 240 is configured. It is assumed that the vehicle specification information storage unit 210 stores the same information as described above.

  The vehicle state quantity calculation unit 220 receives inputs from the various sensors 150 and the vehicle specification information storage unit 210 as in the first embodiment and the second embodiment. The vehicle state quantity calculation unit 220 according to the third embodiment includes a target yaw rate calculation unit 222, a target vehicle body slip angle calculation unit 224, and a target acceleration calculation unit 225. The same processing as that described in the first embodiment or the second embodiment is performed. Based on values input from the various sensors 150 and values input from the vehicle specification information storage unit 210, a target yaw rate, a target vehicle body slip angle, and a target lateral acceleration that the vehicle 100 should generate are calculated. The vehicle state quantity calculation unit 220 outputs the calculated values to the moment calculation unit 230, the front wheel actual steering angle ratio calculation unit 233, and the rear wheel actual steering angle ratio calculation unit 234.

  The moment calculator 230 calculates a moment M to be applied to the vehicle 100. The front wheel actual steering angle ratio calculation unit 233 calculates a ratio between the actual steering angle δ corresponding to the operation of the steering wheel 16 and the actual steering angle δf to be set for the front wheels 10 (that is, “front wheel actual steering angle ratio kf”). . The rear wheel actual steering angle ratio calculation unit 234 is a ratio between the actual steering angle δ corresponding to the operation of the steering wheel 16 and the actual steering angle δr to be set for the rear wheel 7 (ie, “rear wheel actual steering angle ratio kr”). Is calculated. The calculated moment M, front wheel actual steering angle ratio kf, and rear wheel actual steering angle ratio kr are output to the controller unit 240.

  The controller unit 240 determines respective output torques in the left and right drive units 8L and 8R so that the vehicle 100 can actually generate the input moment M. Then, the controller unit 214 outputs a torque control signal 72 corresponding to the determined output torque to the inverter 14. Further, the controller unit 240 outputs a control signal 80 to the front wheel steering device 20 so that the front wheels 10 can realize the actual steering angle δf determined from the input front wheel actual steering angle ratio kf. Similarly, the controller unit 240 outputs a control signal 81 to the rear wheel steering device 21 so that the rear wheel 7 can realize the actual steering angle δr determined from the input rear wheel actual steering angle ratio kr.

  In this manner, by imposing the moment M calculated by the vehicle body control system 200b according to the third embodiment, the front wheel actual steering angle ratio kf, and the rear wheel actual steering angle ratio kr on the vehicle 100 during steering. The yaw rate, lateral acceleration, and vehicle body slip angle with respect to steering are always maintained at desired values. Thereby, the vehicle 100 at the time of steering can accurately perform an appropriate vehicle behavior in cooperation with the driver's operation of the handle 16.

(Calculation method of moment, actual steering angle ratio of front wheels, and actual steering angle ratio of rear wheels)
Hereinafter, a method for calculating the moment M applied to the vehicle 100, the front wheel actual steering angle ratio kf and the front wheel actual steering angle ratio kr set in the vehicle 100, and the like according to the third embodiment will be described. The moment M, the front wheel actual steering angle ratio kf, and the front wheel actual steering angle ratio kr are calculated by the moment calculation unit 230, the front wheel actual steering angle ratio calculation unit 233, and the rear wheels, respectively, in the vehicle control system 200. It is assumed that the actual steering angle ratio calculation unit 234 performs this.

  Assuming that the actual steering angle corresponding to the driver's operation of the steering wheel 16 is θ, the front wheel actual steering angle ratio is kf, and the rear wheel actual steering angle ratio is kr, the yaw rate rδ and lateral acceleration gyδ generated in the vehicle 100 with respect to steering. The vehicle body slip angle βδ is expressed by Expression (65), Expression (66), and Expression (67), respectively.

Note that the symbols in Formula (65), Formula (66), and Formula (67) are used in the same meaning as described above.

  Here, the yaw rate rm, lateral acceleration gym, and vehicle body slip angle βm generated in the vehicle 100 to which the moment M is applied to the vehicle 100 satisfy the above-described equations (39), (58), and (40), respectively. And

  From the above, the yaw rate r ′, the lateral acceleration gy ′, and the vehicle body slip angle β ′ generated in the vehicle 100 when the moment M is applied to the vehicle 100 during steering are expressed by the equations (68), (69), ( 70).

  In the third embodiment, a condition is set such that the yaw rate ', the lateral acceleration gy' and the vehicle body slip angle β 'generated in the vehicle 100 when the moment M is applied to the vehicle 100 during steering are set to target values. In other words, the vehicle 100 satisfies the above-described expression (46), expression (62), and expression (47) at the same time.

  Therefore, substituting equation (68) into equation (46) yields equation (71), substituting equation (69) into equation (62) yields equation (72), and equation (47) yields equation (70). ) Is substituted, equation (73) is obtained.

  Next, when Equation (71), Equation (72), and Equation (73) are combined to solve the front wheel actual steering angle ratio kf, the rear wheel actual steering angle ratio kr, and the moment M, Equation (74) is obtained. .

  From the equation (74), the front wheel actual steering angle ratio kf, the rear wheel actual steering angle ratio kr, and the moment M are the yaw rate gains Grf and Grr due to steering, the yaw rate time constants Trf and Trr due to steering, and the yaw rate due to the moment M being applied. Yaw rate time constant Trm by applying gain Grm and moment M, lateral acceleration gain Ggyf and Ggyr by steering, lateral acceleration time constants T1f, T2f, T1r, and T2r by steering, lateral acceleration gain Ggym by applying moment M, and moment It is calculated using the lateral acceleration time constant Tgym by applying M, the vehicle body slip angle gains Gbf and Gbr by steering, the vehicle body slip angle time constants Tbf and Tbr by steering, and the vehicle body slip angle Gbm by applying moment M. The

  The front wheel actual steering angle ratio kf is calculated using the target yaw rate Yr_ta in addition to the above. The rear wheel actual steering angle ratio kr is calculated using the target lateral acceleration gy_ta in addition to the above. The moment M is calculated using the target vehicle body slip angle β_ta in addition to the above.

  As described above, in the third embodiment of the present invention, when the vehicle 100 is steered, a moment is applied to the vehicle 100, and the actual steering angles of the front wheels 10 and the rear wheels 7 are made independent of the steering operation. Set to. Further, in the steering vehicle 100 to which the moment M is applied, the yaw rate r ′, the lateral acceleration gy ′ generated by the vehicle 100, and the vehicle body slip angle β ′ are calculated under conditions such that the target values are obtained. . Thus, the vehicle 100 at the time of steering can accurately coordinate with the operation of the steering wheel 16 by the driver and accurately perform a stable turning motion in a state where a desired yaw rate, lateral acceleration, and vehicle body slip angle are generated. it can. Further, since the generation of the yaw rate, the lateral acceleration, and the vehicle body slip angle acting on the vehicle is not delayed with respect to the operation of the driver's handle 16, the driver does not feel uncomfortable.

1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment of the present invention. It is the figure which showed the vehicle behavior which arises in the vehicle at the time of steering. It is the figure which showed giving the moment which concerns on this embodiment, etc. at the time of steering of a vehicle. It is a figure showing composition of a vehicle control system concerning a 1st embodiment of the present invention. It is the figure which showed the force etc. which act on a vehicle when a moment is provided at the time of steering of a vehicle. It is a figure which shows the structure of the vehicle control system which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the vehicle control system which concerns on 3rd Embodiment of this invention.

Explanation of symbols

1 Engine 7 Rear Wheel 8 Drive Unit 10 Front Wheel 13 Battery 14 Inverter 16 Handle 20 Front Wheel Steering Device 21 Rear Wheel Steering Device 100 Vehicle 200, 200a, 200b, 200c Vehicle Control System

Claims (8)

A vehicle control device in which one of the front and rear wheels is driven by a motor and the front and rear wheels can be steered independently,
A moment calculating means for calculating a moment to be applied to the vehicle;
Front and rear wheel actual steering angle calculating means for calculating an actual steering angle to be set for the front and rear wheels of the vehicle,
The vehicle control apparatus characterized in that the moment calculation means and the front and rear wheel actual steering angle calculation means calculate the vehicle during steering so that the vehicle is in a desired state. Motor control means for controlling the motor based on the calculated moment;
Front and rear wheel steering means for changing the angles of the front and rear wheels of the vehicle based on the calculated actual steering angle of the front wheels and the actual steering angle of the rear wheels,
The vehicle control device according to claim 1, wherein the motor control unit and the front and rear wheel steering unit are executed when a driver's steering operation is performed while satisfying a predetermined condition. The moment calculating means and the front and rear wheel actual steering angle calculating means calculate the yaw rate acting on the vehicle and the vehicle body slip angle of the vehicle to be target values,
The vehicle control apparatus according to claim 1 or 2, wherein the front and rear wheel actual steering angle calculation means calculates a ratio of an actual steering angle to be set on the rear wheel with respect to an actual steering angle of the front wheel. The moment calculating means and the front and rear wheel actual steering angle calculating means calculate the moment M and the ratio k of the actual steering angle to be set on the rear wheel with respect to the actual steering angle δf of the front wheel based on the equation (1). ,

Yr_ta is the target yaw rate of the vehicle, β_ta is the target vehicle body slip angle of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, Trf is the yaw rate time constant of the front wheels by steering, and Trr is the steering The rear wheel yaw rate time constant, Grm is the yaw rate gain by applying the moment, Trm is the yaw rate time constant by applying the moment, Gbf is the front body slip angle gain by steering, and Gbr is the rear body slip angle by steering. Gain, Tbf is the vehicle slip angle time constant of the front wheel by steering, Tbr is the vehicle slip angle time constant of the rear wheel by steering, Gbm is the vehicle slip angle gain by applying the moment, S is the Laplace operator, ωn is the vehicle's slip angle time constant 4. The vehicle body natural frequency, ζ, is a vehicle body damping ratio of the vehicle. Both of the control device. The moment calculating means and the front and rear wheel actual steering angle calculating means calculate the yaw rate acting on the vehicle and the lateral acceleration acting on the vehicle to be target values,
The vehicle control apparatus according to claim 1 or 2, wherein the front and rear wheel actual steering angle calculation means calculates a ratio of an actual steering angle to be set on the rear wheel with respect to an actual steering angle of the front wheel. The moment calculating means and the front and rear wheel actual steering angle calculating means calculate the moment M and the ratio k of the actual steering angle to be set on the rear wheels with respect to the actual steering angle δf of the front wheels based on the equation (2). ,

Yr_ta is the target yaw rate of the vehicle, gy_ta is the target lateral acceleration of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, Trf is the yaw rate time constant of the front wheels by steering, and Trr is by steering Rear wheel yaw rate time constant, Grm is yaw rate gain by applying moment, Trm is yaw rate time constant by applying moment, Ggyf is front wheel lateral acceleration gain by steering, Ggyr is rear wheel lateral acceleration gain by steering, T1f Is the first lateral acceleration time constant of the front wheels by steering, T2f is the second lateral acceleration time constant of the front wheels by steering, T1r is the first lateral acceleration time constant of the rear wheels by steering, and T2r is the first lateral acceleration time constant of the rear wheels by steering. The lateral acceleration time constant of 2, Ggym is the lateral acceleration gain by applying the moment, and Tgym is the lateral acceleration by applying the moment. The number, S is a Laplace operator, .omega.n the vehicle body natural frequency of the vehicle body damping ratio of the vehicle zeta, it is a control apparatus for a vehicle according to claim 5, characterized in. The moment calculating means and the front and rear wheel actual steering angle calculating means calculate the yaw rate acting on the vehicle, the vehicle body slip angle of the vehicle, and the lateral acceleration acting on the vehicle to be target values,
The front and rear wheel actual steering angle calculating means includes:
The ratio of the actual steering angle to be set on the front wheels to the actual steering angle corresponding to the steering wheel operation,
The vehicle control device according to claim 1 or 2, wherein a ratio of an actual steering angle to be set for a rear wheel with respect to an actual steering angle corresponding to an operation of a steering wheel is calculated. The moment calculating means and the front and rear wheel actual steering angle calculating means are based on the equation (3), the moment M and the ratio kf of the actual steering angle to be set on the front wheels with respect to the actual steering angle θ corresponding to the operation of the steering wheel, A ratio kr of the actual steering angle to be set on the rear wheel with respect to the actual steering angle θ corresponding to the operation of the steering wheel,

Yr_ta is the target yaw rate of the vehicle, β_ta is the target vehicle body slip angle of the vehicle, gy_ta is the target lateral acceleration of the vehicle, Grf is the yaw rate gain of the front wheels by steering, Grr is the yaw rate gain of the rear wheels by steering, and Trf is by steering Front wheel yaw rate time constant, Trr is the rear wheel yaw rate time constant by steering, Grm is the yaw rate gain by applying the moment, Trm is the yaw rate time constant by applying the moment, Ggyf is the front wheel lateral acceleration gain by steering, and Ggyr is Lateral acceleration gain of the rear wheels by steering, T1f is the first lateral acceleration time constant of the front wheels by steering, T2f is the second lateral acceleration time constant of the front wheels by steering, and T1r is the first lateral acceleration of the rear wheels by steering Constant, T2r is the second lateral acceleration time constant of the rear wheel by steering, Ggym is the lateral acceleration gain by applying the moment, and Tgym is the front Lateral acceleration time constant by applying the moment, Gbf is the front body slip angle gain by steering the vehicle, Gbr is the rear body slip angle gain by steering, Tbf is the front body slip angle time constant by steering, and Tbr is The vehicle slip angle time constant of the rear wheel by steering, Gbm is the vehicle slip angle gain by applying the moment, S is the Laplace operator, ωn is the natural frequency of the vehicle body, and ζ is the vehicle body damping ratio of the vehicle. The vehicle control device according to claim 7.

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