JP6102086B2 - Power steering system, vehicle equipped with the same, and control method thereof - Google Patents

Description

  The present invention relates to a power steering system that suppresses energy loss of a pump to the maximum and provides an optimal steering assist force to a driver, a vehicle equipped with the power steering system, and a control method thereof.

  In recent years, a technique for reducing energy by steering by varying a discharge flow rate using a variable capacity power steering pump has been proposed and put into practical use. For example, there is a device that calculates an instruction current of a variable capacity power steering pump based on a steering angle, a steering angular velocity, and a steering acceleration for a vehicle speed other than a high speed (see, for example, Patent Document 1).

  This apparatus regards a case where the vehicle speed is equal to or higher than a predetermined vehicle speed as a straight traveling state, and calculates a command current from a minimum target discharge flow rate with a steering angle, a steering angular velocity, and a steering acceleration as zero. With this control, in the straight traveling state, the discharge flow rate of the variable capacity power steering pump due to disturbances such as slight steering and kickback does not increase excessively, and energy loss can be reduced.

  However, in the above-described apparatus, the vehicle speed is an important factor for setting weights for maneuverability and energy loss reduction. And, as the vehicle speed is lower, the basic flow rate is set higher in order to satisfy the steering performance, and this causes a problem that the energy saving operation area of the pump becomes narrower.

  Also, the discharge flow rate changes according to the driver's steering operation (for example, the operation that changes the steering angle, steering angular velocity, and steering acceleration), and a delay occurs in the reaction time of the discharge flow rate due to the driver's steering operation. The case where it is not possible to demonstrate sufficient assist power occurs. In this case, there is a problem that the driver's corrective steering operation increases and the energy loss of the pump is worsened. Furthermore, since the change in the discharge flow rate generated only in accordance with the vehicle speed and the steering information cannot cope with the steering assist force that should be generated due to the unevenness of the road surface, a feeling that it is difficult for the driver to operate or steer is generated.

  On the other hand, there is an apparatus that sets a target assist amount by a fuzzy rule that increases the target assist amount as the steering degree coefficient calculated based on the traveling speed and steering angular velocity of the vehicle increases (see, for example, Patent Document 2). . This device improves both the ease of steering and the steering stability, and enables simple and fine control by fuzzy rules.

  However, even if simple and fine control is enabled by the fuzzy rule, the same problem as described above occurs because the steering degree coefficient based on the vehicle speed and the steering angular velocity is used.

JP 2011-973 A JP 7-186992 A

The present invention has been made in view of the above problems, and its purpose is to calculate an optimal target steering angle and target steering angular velocity before the driver steers, and to respond to the target steering angle and target steering angular velocity. By controlling the pump based on the basic flow rate, it is possible to reduce energy loss, improve responsiveness, and provide optimal steering assist force, a vehicle equipped with the power steering system, and its It is to provide a control method.

A power steering system of the present invention for solving the above-described object includes a pump that supplies hydraulic oil to a steering assist device that assists the steering performance of the steering wheel, a control device that controls a discharge flow rate of the hydraulic oil of the pump, In the power steering system, the control device always calculates the target steering angle and the target steering angular velocity based on the vehicle state and the road state, and based on the calculated target steering angle and the magnitude of the target steering angular velocity. The basic flow rate calculation means for calculating the basic flow rate according to the first fuzzy rule, and the first discharge flow rate control means for controlling the discharge flow rate of the pump so as to become the basic flow rate at all times .

  According to this configuration, the basic flow rate is calculated based on the target steering angle and the target steering angular velocity calculated using not only the vehicle state such as the vehicle speed and the steering angle but also the road state, and the pump flow rate is adjusted to the basic flow rate. The discharge flow rate can be controlled. As a result, the discharge flow rate of the pump is controlled before the driver performs the steering operation, so that the responsiveness can be improved and the correction steering of the driver can be reduced to suppress the deterioration of the energy loss of the pump.

  In addition, compared with the case where the discharge flow rate is controlled based on the vehicle speed and the driver's steering operation, the pump has a wider energy-saving operation range, and can save energy, and based on the driver's steering operation predicted in advance. Since the pump discharge flow rate is controlled, the responsiveness can be improved and the optimum steering assist force can be provided.

In the power steering system described above, a vehicle speed sensor that acquires a vehicle speed of the vehicle as the vehicle state and a road curvature that acquires a road curvature of a road ahead of the vehicle as the road state before the steering wheel is steered. Curvature acquisition means, based on the yaw angular velocity of the vehicle calculated by multiplying the acquired road curvature and the vehicle speed, and the yaw angle calculated by time integration of the yaw angular velocity. When the basic flow rate calculation means calculates the target steering angle and the target steering angular velocity, the target steering angle and the target steering angular velocity can be calculated from the yaw angle and the yaw angular velocity.

When the yaw angle calculation first means for calculating the yaw angle based on the acquired road curvature and the vehicle speed is used, it is not necessary to provide a yaw rate sensor for detecting or measuring the yaw angle, so that the cost can be reduced.

  In addition, in the power steering system described above, whether or not the vehicle is steered rapidly is determined based on an angular deviation value between the target steering angle and the actual steering angle and an angular velocity deviation value between the target steering angular velocity and the actual steering angular velocity. When determining that the sudden steering determination means and the sudden steering determination means determine that the vehicle has been suddenly steered, the sudden steering additional flow rate that increases as the angular deviation value and the angular velocity deviation value increase is calculated. An additional flow rate calculating means, a first corrected flow rate calculating means for calculating a first corrected flow rate by adding the additional flow rate at the time of sudden steering to the basic flow rate, and a discharge flow rate of the pump to be the first corrected flow rate. And a second discharge flow rate control means for controlling.

  Further, in the power steering system described above, the unevenness determining means for determining whether or not the vehicle is traveling on unevenness based on at least one of the vehicle vertical acceleration, the roll acceleration, and the pitch angular velocity, and the unevenness determining means determines whether the vehicle is uneven. When it is determined that the vehicle is traveling, an additional flow calculation unit for unevenness that calculates an additional flow rate during unevenness that increases with at least one increase in the vehicle vertical acceleration, the roll acceleration, or the pitch angular velocity, and the unevenness in the basic flow rate. Second correction flow rate calculation means for calculating a second correction flow rate by adding the additional flow rate, and third discharge flow rate control means for controlling the discharge flow rate of the pump to be the second correction flow rate. Is preferred.

  According to the above configuration, when the vehicle is suddenly steered based on the basic flow rate, and when the vehicle travels on an uneven road, the basic flow rate includes the additional flow amount during sudden steering or the size of the unevenness. Since an additional flow rate during unevenness can be added, an appropriate pump discharge flow rate can be set. Thereby, it is possible to provide the optimum steering assist force while keeping the energy saving operation range wide and to maintain the steering performance.

  In addition, a vehicle for solving the above problem is configured by mounting the power steering system described above. According to this configuration, energy loss of the pump is suppressed to the maximum, so that fuel consumption can be improved, and driving comfort can be improved by providing an optimal steering assist force to the driver. it can.

In addition, a power steering system control method for solving the above-described problem is a power steering system control method for controlling the discharge flow rate of hydraulic oil of a pump that supplies hydraulic oil to a steering assist device that assists the steering performance of the steering wheel. , The vehicle state and the road state are always acquired, the target steering angle and the target steering angular velocity are calculated based on the acquired vehicle state and the road state, and the calculated target steering angle and the target steering angular velocity are calculated. In this method, the basic flow rate is calculated according to a first fuzzy rule based on the magnitude, and the discharge flow rate of the pump is always controlled to be the basic flow rate.

  In addition, in the control method of the power steering system described above, in the basic flow rate calculation step, a yaw angle calculation first step of calculating a yaw angle and a yaw angular velocity based on the detected or measured vehicle speed and road curvature, or detection Alternatively, the target steering angle and the target steering angular velocity are calculated from either one of the yaw angle calculation second step of calculating the yaw angle from the measured yaw angular velocity and the state equation of the vehicle using the yaw angle and the yaw angular velocity. Preferably including a target steering angle calculating step.

  Further, in the control method of the power steering system, before the first discharge flow rate control step, an angular deviation value between the target steering angle and the actual steering angle, and an angular speed deviation between the target steering angular speed and the actual steering angular speed. From the value, it is determined that the vehicle is suddenly steered, and if the vehicle is suddenly steered in the sudden steering determination step, the angular deviation value and the angular velocity deviation value are increased. A sudden steering additional flow rate calculating step for calculating an increasing rapid steering additional flow rate, a first corrected flow rate calculating step for calculating a first corrected flow rate by adding the rapid steering additional flow rate to the basic flow rate, and the pump And a second discharge flow rate control step of controlling the discharge flow rate to be the first corrected flow rate.

  In addition, in the power steering system control method described above, before the first discharge flow rate control step, it is determined whether or not the vehicle is traveling on unevenness from at least one of vehicle vertical acceleration, roll acceleration, and pitch angular velocity. If the vehicle is determined to be traveling on unevenness in the unevenness determination step and the unevenness determination step, an additional flow rate during unevenness that increases with at least one increase in the vehicle vertical acceleration, the roll acceleration, or the pitch angular velocity is calculated. An irregular flow additional flow calculating step, a second corrected flow calculating step of calculating a second corrected flow rate by adding the irregular flow additional flow to the basic flow, and a discharge flow rate of the pump to be the second corrected flow rate. It is preferable to include a third discharge flow rate control step of controlling in this manner.

  According to the present invention, before the driver steers, the optimum target steering angle and the target steering angular velocity are calculated, and the pump is controlled based on the basic flow rate corresponding to the target steering angle and the target steering angular velocity. Loss can be reduced and responsiveness can be improved to improve steering performance.

1 is a schematic diagram showing a vehicle equipped with a power steering system according to a first embodiment of the present invention. It is the schematic which shows the pump of the power steering system of 1st Embodiment which concerns on this invention. It is a flowchart which shows the control method of the power steering system of 1st Embodiment which concerns on this invention. It is the figure which showed the fuzzy rule used for the control method of the power steering system of 1st Embodiment which concerns on this invention. 5 is a graph showing a fuzzy set used in the control method of the power steering system according to the first embodiment of the present invention, where (a) shows a fuzzy set of target steering angles, and (b) shows a fuzzy set of target steering angular velocities. (C) shows a basic diversion fuzzy set. It is the schematic which shows the vehicle carrying the power steering system of 2nd Embodiment which concerns on this invention. It is a flowchart which shows the control method of the power steering system of 2nd Embodiment which concerns on this invention. It is the figure which showed the fuzzy rule used for the control method of the power steering system of 2nd Embodiment which concerns on this invention. It is the schematic which shows the vehicle carrying the power steering system of 3rd Embodiment concerning this invention. It is a flowchart which shows the control method of the power steering system of 3rd Embodiment concerning this invention. It is the figure which showed the fuzzy rule used for the control method of the power steering system of 3rd Embodiment concerning this invention. It is the schematic which shows the vehicle carrying the power steering system of 4th Embodiment concerning this invention. It is a flowchart which shows the control method of the power steering system of 4th Embodiment concerning this invention.

  Hereinafter, a power steering system according to an embodiment of the present invention, a vehicle equipped with the same, and a control method thereof will be described with reference to the drawings. As shown in FIG. 1, a so-called cab-over type truck having a body 2, a cab 3, and a chassis 4 will be described as an example of a vehicle 1 according to the embodiment. However, the present invention is applied to a bonnet-type general vehicle. Can also be applied. In addition, as the vehicle 1 according to the embodiment, a so-called one-diff vehicle having a 6 × 2 (front 1 axis, rear 2 axis / 1 axis drive) axle structure including a front wheel 5, a rear drive wheel 6 and a rear wheel 7 is exemplified. However, the present invention can also be applied to an axle having a 4 × 2 or 6 × 4 structure.

  First, a power steering system according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, in the vehicle 1, when the driver steers a handle (also referred to as a steering wheel) 8, the front wheel 5 is steered and turns. At this time, the power steering system 10 is provided as a system for assisting the steering of the driver. The power steering system 10 includes a hydraulic steering assist device (hereinafter referred to as power steering) 11 and a pump 12, an ECU (control device) 13, a camera (video acquisition device or image acquisition device) 14, and a vehicle speed sensor. 15.

  The ECU 13 is a device called an engine control unit, and is a device that controls the engine. Alternatively, the ECU 13 may be provided as a control device that controls the discharge flow rate of the pump 12.

As shown in FIG. 2, the pump 12 of the power steering system 10 is a variable displacement vane pump, and includes an adapter 21, a cam ring 22, a rotor 23, a vane 24, a pin 25, a relief valve 26, a differential pressure control valve 27, an electromagnetic A valve 28 is provided, and the ECU 13 operates the solenoid valve 28 to variably control the differential pressure between the upstream side and the downstream side of the solenoid valve 28, that is, the differential pressure between both pressures of the relief valve 26 and the differential pressure control valve 27. Thus, the position of the valve body in the axial direction is controlled, and thereby the amount of eccentricity of the cam ring 22 is controlled to control the discharge flow rate.

  The power steering system 10 according to the first embodiment allows the ECU 13 to advance a driver's steering operation (target steering angle δ (deg) and target steering angular velocity δ ′ (deg / s) based on the vehicle state and the road state. )) And a basic flow rate calculation means S1 for calculating the basic flow rate Q_base by the estimated steering operation, and a first discharge flow rate control means S2 for controlling the discharge flow rate Q_out of the pump 12 to be the basic flow rate Q_base; Is provided.

  Specifically, the basic flow rate calculation means S1 calculates the basic flow rate Q_base based on a fuzzy rule that increases the basic flow rate Q_base as the target steering angle δ and the target steering angular velocity δ ′ increase.

  In addition, the basic flow rate calculation means S1 includes the yaw angle φ (deg) and the yaw angular velocity φ ′ (based on the vehicle speed V (m / s) detected by the vehicle speed sensor 15 and the road curvature ρ (−) measured by the camera 14. The target steering angle δ (deg) and the target steering angular velocity δ ′ (deg / s) from the yaw angle calculation first means S3 for calculating deg / s) and the state equation of the vehicle 1 based on the yaw angle φ and the yaw angular velocity φ ′. ) For calculating a target steering angle.

Next, a control method of the power steering system 10 according to the first embodiment of the present invention will be described with reference to FIGS. As shown in the flowchart of FIG. 3, first, the ECU 13 performs step S110 for reading necessary parameters. In step S110, the inertia moment I (kg · m ² ) of the vehicle 1, the mass M (kg) of the vehicle 1, the cornering power K _f (N / rad) of the front wheels 5, as constants stored in advance in the ECU 13; From the cornering power K _r (N / rad) of the rear drive wheel 6, the distance l _f (m) from the center of gravity (not shown) of the vehicle 1 to the front wheel shaft (rotation axis of the front wheel 5), and the center of gravity of the vehicle 1 The distance l _r (m) to the rear wheel axis (the rotation axis of the rear driving wheel 6) is called. Further, the road curvature ρ (−) measured by the camera 14 as the detected or measured road state and the vehicle speed V (m / s) detected by the vehicle speed sensor 15 as the detected or measured vehicle state are read.

Next, the yaw angle calculation first means S3 of the ECU 13 performs step S120 of calculating the yaw angle φ and the yaw angular velocity φ ′ using the parameters read in step S110. Yaw angle rate phi 'is obtained from the following equation from the road curvature ρ and the vehicle speed V (1).

'When is calculated, the yaw angle rate phi' yaw angle rate phi to be integrated over time to calculate the yaw angle phi. By obtaining the yaw angle φ and the yaw angular velocity φ ′ from the road curvature ρ and the vehicle speed V, for example, a yaw rate sensor is not necessary, so that the cost can be reduced.

Next, the target steering angle calculation means S4 of the ECU 13 performs step S130 for calculating the target steering angle δ and the target steering angular velocity δ ′ using the yaw angle φ and the yaw angular velocity φ ′. The target steering angle δ is obtained from an equation obtained by modifying the state equation of the power steering system 10 expressed by the following equations (2) to (8).

  Once the target steering angle δ is calculated, the target steering angle δ is calculated by differentiating the target steering angle δ with respect to time.

  Next, the basic flow rate calculation means S1 of the ECU 13 performs step S140 of calculating the basic flow rate Q_base using the target steering angle δ and the target steering angular velocity δ ′. In step S140, the basic flow rate Q_base of the pump 12 is determined by the fuzzy rule R1 shown in FIG. 4 according to the target steering angle δ and the target steering angular velocity δ ′.

In this case, the fuzzy rule R1 is an inference made with the fuzzy set F 1 as the input fuzzy set in FIGS. 5A and 5B and the output fuzzy set in FIG. 5C. It is a rule. More specifically, the basic flow rate Q_base when the target steering angle δ is big (large) and the target steering angular velocity δ ′ is big is set to big, the target steering angle δ is middle, and the basic when the target steering angular velocity δ ′ is middle. The basic flow rate Q_base when the flow rate Q_base is middle, the target steering angle δ is small (small), and the target steering angular velocity δ ′ is small is small.

  That is, the basic flow rate Q_base is calculated based on the fuzzy rule R1 that increases the basic flow rate Q_base as the target steering angle δ and the target steering angular velocity δ ′ increase, and a result close to the driver's feeling can be obtained. The driver's know-how regarding steering can be used as an inference.

  Next, the first discharge flow rate control means S2 of the ECU 13 performs step S150 for controlling the electromagnetic valve 28 so that the discharge flow rate Q_out of the pump 12 becomes the basic flow rate Q_base, and this control method is completed.

  According to this control method, before the driver steers the steering wheel 8, the target steering angle δ and the target steering angular velocity δ ′ are calculated from the vehicle state and the road state (parameters read in step S110), and the target steering is calculated. The basic flow rate Q_base corresponding to the fuzzy rule R1 can be calculated from the angle δ and the target steering angular velocity δ ′.

  Thereby, the responsiveness when the driver steers the steering wheel 8 can be improved, the optimum steering assist force can be provided, and the energy loss of the pump 12 can be suppressed. Further, since the driver's steering operation is estimated in advance and the basic flow rate Q_base is increased when a steering operation is necessary, the energy saving operation area of the pump 12 is wide, and the consumed energy can be reduced.

In this embodiment, the cornering power K _f of the front wheels 5 and the cornering power K _r of the rear drive wheels 6 are constants and are proportional to the wheel load. However, for example, they are calculated in consideration of the slip angle. Variables may be used. Moreover, the method of measuring road curvature (rho) by the camera 14 can use the well-known method etc. which are disclosed by Unexamined-Japanese-Patent No. 2001-10518, for example, The measuring method is not limited.

  Next, a power steering system according to a second embodiment of the present invention will be described with reference to FIG. The power steering system 30 includes a road state acquisition device 31 and a handle angle sensor 32 as shown in FIG. 6 instead of the camera 14 of the power steering system 10 of FIG.

  The road condition acquisition device 31 grasps the current position of the vehicle 1 from a map and a sanitary positioning system (also referred to as a global navigation satellite system; GPS, GLONASS, Galileo, etc.) as in car navigation, and the vehicle 1 will travel from now on. It is an apparatus which acquires road curvature (rho) as the road state of the road to perform. Car navigation may be used instead of the road condition acquisition device 31.

  In the power steering system 30 of this embodiment, in addition to the basic flow rate calculation means S1 and the first discharge flow rate control means S2 described above, the ECU 13 has an angle deviation value (δ between the target steering angle δ and the actual steering angle θ). −θ) (hereinafter referred to as an angular deviation value Δδ) and an angular velocity deviation value (δ′−θ ′) (hereinafter referred to as an angular velocity deviation value Δδ ′) between the target steering angular velocity δ ′ and the actual steering angular velocity θ ′. An additional flow calculation means S5 for sudden steering that calculates an additional flow Q_ste at the time of sudden steering to be added to the basic flow Q_base according to the magnitude, and an additional flow at the time of sudden steering when the additional flow Q_ste at the time of sudden steering is greater than zero. The first corrected flow rate calculation means S6 for calculating the first corrected flow rate Q_corr1 to which Q_ste is added, and the discharge flow rate Q_out of the pump 12 is controlled to be the first corrected flow rate Q_corr1. Includes a second discharge flow rate control means S7 to, a.

  Next, a control method of the power steering system 30 according to the second embodiment of the present invention will be described with reference to FIGS. Here, the same steps as those in the control method shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  First, as shown in FIG. 7, the ECU 13 performs step S210 for reading the necessary parameters. In this step S210, instead of the road curvature ρ of the parameter in step S110, the road curvature ρ measured by the road condition acquisition device 31, in addition to the actual steering angle θ (deg) detected by the steering wheel angle sensor 32, The actual steering angular velocity θ ′ (deg / s) obtained by differentiating the actual steering angle θ with respect to time is also read.

Next, if steps S120 to S140 are performed, then the additional flow calculation means S5 at the time of sudden steering of the ECU 13 determines that the angle deviation value Δδ between the target steering angle δ and the actual steering angle θ and the target steering angular velocity δ ′. Step S220 is performed to calculate an angular velocity deviation value Δδ ′ from the actual steering angular velocity θ ′.

  Next, step S230 is performed to calculate the additional flow Q_corr1 during sudden steering using the angular deviation value Δδ and the angular velocity deviation value Δδ ′. In this step S230, the additional flow Q_corr1 at the time of sudden steering to be added to the basic flow Q_base is determined by the fuzzy rule R2 shown in FIG. 8 according to the magnitude of the angle deviation value Δδ and the angular velocity deviation value Δδ ′. Here, let L be the steering angular velocity sensitivity parameter.

The fuzzy rule R2 is an inference rule created using the fuzzy set F2 . Specifically, when the value obtained by adding the value obtained by integrating the steering angular velocity sensitivity parameter L and the angular velocity deviation value Δδ ′ to the angle deviation value Δδ is big, the driver is strongly aware of sudden steering (or the vehicle 1 is suddenly steered). In accordance with the magnitudes of the angle deviation value Δδ and the angular velocity deviation value Δδ ′, the sudden steering additional flow rate Q_ste is set to big, and the angular deviation value Δδ includes the steering angular velocity sensitivity parameter L and the angular velocity deviation. When the value obtained by adding up the values Δδ ′ is a small value, it is treated as a disturbance, and the additional flow Q_ste during sudden steering is set to zero.

  The steering angular velocity sensitivity parameter L can be set to an arbitrary value obtained experimentally. However, if the steering angular velocity sensitivity parameter L is set to a small value, the sensitivity to the steering speed can be increased. Sensitivity can be lowered.

  If the additional flow Q_ste at the time of sudden steering is zero in step S230, next, step S150 is performed, and this control method is completed. On the other hand, if the sudden steering additional flow rate Q_ste is not zero in step S230, the first correction flow rate calculation means S6 of the ECU 13 then adds the rapid steering additional flow rate Q_ste to the basic flow rate Q_base calculated in step S140. In step S240, the first corrected flow rate Q_corr1 is calculated.

  Next, the second discharge flow rate control means S7 of the ECU 13 performs step S250 for controlling the electromagnetic valve 29 so that the discharge flow rate Q_out of the pump 12 becomes the first corrected flow rate Q_coor1, and this control method is completed.

  According to this control method, even if the driver steers the steering wheel 8 more than the driver's steering operation estimated in advance, the sudden steering can be determined, and the additional flow Q_ste at the time of sudden steering accompanying the sudden steering. Can be added to the basic flow rate Q_base. As a result, even when the driver steers suddenly, the steering performance can be maintained by providing the optimum steering assist force without reducing the responsiveness.

  In this embodiment, the road condition acquisition device 31 having a map and a sanitary positioning system is used for the road curvature ρ. For example, a satellite positioning system and a steering recorder (the steering operation when the driver runs on the same route) A road condition acquisition device having a recording device) may be used.

  Next, a power steering system according to a third embodiment of the present invention will be described with reference to FIG. The power steering system 40 includes an acceleration sensor 41 as shown in FIG. 9 in addition to the power steering system 10 of FIG.

The acceleration sensor 41 only needs to be able to measure the vertical acceleration Z (m / s ² ), roll acceleration α (m / s ² ), and pitch acceleration β (m / s ² ) of the vehicle 1. Sensors are preferred, and gyro sensors can be used instead.

  The power steering system 40 includes an ECU 13 that calculates an uneven flow additional flow rate calculation means S8 that calculates an uneven flow additional flow rate Q_rou to be added to the basic flow rate Q_base according to the vertical acceleration Z, roll acceleration α, and pitch acceleration β. When the hour additional flow rate Q_rou is greater than zero, the second corrected flow rate calculation means S9 for calculating the second corrected flow rate Q_corr2 obtained by adding the irregular flow additional flow rate Q_rou to the basic flow rate Q_base, and the discharge flow rate Q_out of the pump 12 is the second. And third discharge flow rate control means S10 that controls the flow rate to be corrected flow rate Q_corr2.

  Next, a control method for the power steering system 40 according to the third embodiment of the present invention will be described with reference to FIGS. 10 and 11. Here, the same steps as those in the control method shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  First, as shown in FIG. 10, the ECU 13 performs step S310 for reading in the necessary parameters. In step S310, in addition to the parameters in step S110, the vertical acceleration Ζ, roll acceleration α, and pitch acceleration β of the vehicle 1 detected by the acceleration sensor 41 are also read.

  Next, when steps S120 to S140 are performed, the uneven flow additional flow calculation means S8 of the ECU 13 calculates the uneven flow additional flow Q_rou using the vertical acceleration Ζ, the roll acceleration α, and the pitch acceleration β. Step S320 is performed. In this step S320, the irregular flow additional flow Q_rou to be added to the basic flow Q_base is determined by the fuzzy rule R3 shown in FIG. 11 according to the magnitudes of the vertical acceleration Ζ, the roll acceleration α, and the pitch acceleration β.

The fuzzy rule R3 is a inference rule is created using the fuzzy set F 3. Specifically, when the vertical acceleration Ζ, roll acceleration α, and pitch acceleration β are big, the driver determines that it is difficult to steer (or the unevenness of the road on which the vehicle 1 is traveling is large), and the vertical acceleration Ζ, Depending on the magnitude of roll acceleration α and pitch acceleration β, the additional flow Q_rou at the time of unevenness is set to big, and when vertical acceleration Ζ, roll acceleration α, and pitch acceleration β are small, it is processed as disturbance and added at the time of unevenness The flow rate Q_rou is set to zero.

  If the additional flow Q_rou at the time of unevenness is zero in step S320, next, step S150 is performed and the control method is completed. On the other hand, if the uneven flow additional flow Q_rou is not zero in step S320, the second corrected flow calculation means S9 of the ECU 13 then adds the uneven flow additional flow Q_rou to the basic flow Q_base calculated in step S140. Step S330 for calculating the second corrected flow rate Q_corr2 is performed.

  Next, the third discharge flow rate control means S10 of the ECU 13 performs step S340 for controlling the electromagnetic valve 28 so that the discharge flow rate Q_out of the pump 12 becomes the second corrected flow rate Q_coor2, and this control method is completed.

According to this control method, the vertical acceleration Ζ vehicle 1, roll acceleration alpha, and the pitch acceleration beta, it is possible to determine the magnitude of the road surface irregularities, the pump according to the size of the unevenness of the road surface The 12 discharge flow rates Q_out can be increased. Thereby, when the driver performs the steering holding operation or the steering operation on the uneven road surface, it is possible to suppress the sense that the steering wheel 8 is caught and it is difficult to perform the steering holding operation or the steering operation.

As in the prior art, determining the flow rate according to the vehicle speed V cannot set an appropriate flow rate according to the unevenness of the road surface. If the flow rate is set high, the energy saving area becomes narrow, and if it is set low, the road surface The flow rate is insufficient with respect to the unevenness, and the steerability is deteriorated. The present invention provides a basic flow rate Q_
The problem can be solved by adding an uneven flow additional flow Q_rou corresponding to the size of the road surface unevenness to the base.

Next, a power steering system of a reference example will be described with reference to FIG. This power steering system 50 includes a yaw rate sensor 51 as shown in FIG. 12 in place of the camera 14 of the power steering system 10 of the first embodiment shown in FIG. An acceleration sensor 53 is provided.

  The power steering system 50 includes a basic flow rate calculation means having a yaw angle φ detected by the yaw rate sensor 51 and a yaw angle calculation second means for differentiating the yaw angle φ with respect to time and calculating a yaw angle velocity φ ′. S11, first discharge flow rate control unit S2, sudden steering additional flow rate calculation unit S5, first correction flow rate calculation unit S6, second discharge flow rate control unit S7, uneven flow rate additional flow rate calculation unit S8, second correction flow rate calculation unit S9 And third discharge flow rate control means S10.

  In addition, when the additional flow Q_ste at the time of sudden steering and the additional flow Q_rou at the time of unevenness are each greater than zero, a third corrected flow Q_corr3 is calculated by adding the additional flow Q_ste at the time of sudden steering and the additional flow Q_rou at the time of unevenness to the basic flow Q_base. Third corrected flow rate calculating means S12, and fourth discharge flow rate control means S13 for controlling the discharge flow rate Q_out of the pump 12 to be the third corrected flow rate Q_corr3.

Next, a control method of the power steering system 50 of the reference example will be described with reference to FIG. The same steps as those in the control method shown in FIGS. 3, 7, and 10 are denoted by the same reference numerals, and the description thereof is omitted.

First, the ECU 13 performs step S410 for reading necessary parameters. In step S410, instead of the parameters in step S110, the yaw angle φ detected by the yaw rate sensor 51, the yaw angular velocity φ ′ obtained by differentiating the yaw angle φ with respect to time, and the actual steering angle θ detected by the steering wheel angle sensor 52. (Deg), the actual steering angular velocity θ ′ (deg / s) obtained by differentiating the actual steering angle θ with time, the vertical acceleration Ζ (m / s ² ) of the vehicle 1 detected by the acceleration sensor 53, and the roll acceleration α (m / S ² ) and pitch acceleration β (m / s ² ).

  Next, if step S130 to step S140 is performed, then step S320 is performed. In step S320, when the uneven flow rate additional flow Q_rou is not zero, next, after performing step S330, the process proceeds to the next step S220.

  On the other hand, when the uneven flow rate additional flow Q_rou is zero, step S <b> 330 is not performed, and then step S <b> 220 to step S <b> 230 are performed.

  In this step S230, when the uneven flow additional flow Q_rou is zero and the sudden steering additional flow Q_ste is zero, next, step S150 is performed, and this control method is completed. Further, when the uneven flow additional flow Q_rou is zero and the sudden steering additional flow Q_ste is greater than zero, next, Steps S240 to S250 are performed, and this control method is completed. In addition, when the uneven flow additional flow Q_rou is greater than zero and the sudden steering additional flow Q_ste is zero, step S340 is performed, and this control method is completed.

Further, when the uneven flow additional flow rate Q_rou is greater than zero and the sudden steering additional flow rate Q_ste is greater than zero, the ECU 13 adds the third correction flow rate calculation means S12 to the basic flow rate Q_base calculated in step S140 during unevenness. Step S420 is performed to calculate the third corrected flow rate Q_corr3 by adding the flow rate Q_rou and the additional flow rate Q_ste at the time of sudden steering.

  Next, the fourth discharge flow rate control means S13 of the ECU 13 performs step S430 for controlling the electromagnetic valve 28 so that the discharge flow rate Q_out of the pump 12 becomes the third corrected flow rate Q_coor3, and this control method is completed.

  According to this control method, based on the basic flow rate Q_base, during sudden steering and when traveling on uneven roads, the basic flow rate Q_base is added to the basic flow rate Q_base during sudden steering due to sudden steering and the additional flow rate during unevenness due to the size of the unevenness. Since Q_rou can be added, the discharge flow rate Q_out can be set appropriately. Thereby, it is possible to maintain the steering performance while widening the energy saving operation range.

Since the vehicle 1 equipped with the power steering systems 10 , 30, and 40 of the first to third embodiments described above suppresses the energy loss of the pump 12 to the maximum, the fuel consumption can be improved. Driving comfort can be improved by providing an optimal steering assist force to the driver. Note that, as in the reference example, the second embodiment and the third embodiment may be combined.

Note that the processes until obtaining the yaw angle φ and the yaw angular velocity φ ′ have been described in the calculation method using the camera 14 described in the control method of the first embodiment and the control method of the second embodiment. the road condition acquisition device 31 one may use any of the calculation method used.

  Further, in the embodiment, step S230 for calculating the additional flow Q_ste at the time of sudden steering and step S320 for calculating the additional flow Q_rou at the time of unevenness are performed after step S140 for calculating the basic flow Q_base, but before step S140. This may be done after reading the necessary parameters.

In addition, the control methods of the first to third embodiments described above are set to be performed at predetermined time intervals, or parameters (for example, road curvature ρ, actual steering angle θ, It may be set to be performed when the vertical acceleration Ζ of the vehicle 1 changes).

  Furthermore, the fuzzy rules R1, R2, and R3 used in step S140, step S230, and step S320 can be arbitrarily set according to the vehicle state, the road surface state, the state of the steering operation, and the like, other than those described in the embodiment. These rules may be added and the rules described may be deleted, and the present invention is not limited to the above.

  The power stainless ring system of the present invention calculates an optimal target steering angle and target steering angular velocity before the driver steers, and controls the pump based on the basic flow rate corresponding to the target steering angle and target steering angular velocity. As a result, energy loss can be reduced, and responsiveness can be improved to improve steering performance. Therefore, the present invention can be applied to a vehicle equipped with a hydraulic power steering system.

1 Vehicle 2 Body 3 Cab 4 Chassis 5 Front Wheel 6 Rear Drive Wheel 7 Rear Wheel 8 Handle (Steering Wheel)
10, 30, 40, 50 Power steering system 11 Power steering (steering assist device)
12 pump 13 ECU (control device)
14 Camera (Video acquisition device or image acquisition device)
15 Vehicle speed sensor 31 Road condition acquisition device 32, 52 Steering angle sensor (steering angle sensor)
41, 53 Acceleration sensor 51 Yaw rate sensor S1 Basic flow rate calculation means S2 First discharge flow rate control means S3 Yaw angle calculation first means S4 Target steering angle calculation means S5 Steep steering additional flow rate calculation means S6 First correction flow rate calculation means S7 2 discharge flow rate control means S8 irregularity additional flow rate calculation means S9 second corrected flow rate calculation means S10 third discharge flow rate control means S11 basic flow rate calculation means (basic flow rate calculation means comprising yaw angle calculation second means)
S12 Third corrected flow rate calculation means S13 Fourth discharge flow rate calculation means

Claims (7)

In a power steering system comprising: a pump that supplies hydraulic oil to a steering assist device that assists steering performance of the steering wheel; and a control device that controls a discharge flow rate of the hydraulic oil of the pump.
The control device is
Basically, the target steering angle and the target steering angular velocity are calculated based on the vehicle state and the road state, and the basic flow rate is calculated according to the first fuzzy rule based on the calculated target steering angle and the target steering angular velocity. Flow rate calculating means;
And a first discharge flow rate control means for controlling the discharge flow rate of the pump so as to become the basic flow rate at all times . A vehicle speed sensor that constantly acquires a vehicle speed of the vehicle as the vehicle state; and road curvature acquisition means that acquires a road curvature of a road ahead of the vehicle as the road state, and the control device acquires the Based on the yaw angular velocity of the vehicle calculated by multiplying the road curvature and the vehicle speed, and the yaw angle calculated by time integration of the yaw angular velocity, the basic flow rate calculation means performs the target steering angle and the target steering. The power steering system according to claim 1, wherein the angular velocity is calculated. A configuration in which the control device calculates the target steering angle and the target steering angular velocity by the basic flow rate calculation means using the following formulas (2) to (8) obtained by modifying the state equation of the steering system. The power steering system according to claim 2, wherein the power steering system is configured as described above.


Where I is the moment of inertia of the vehicle, M is the mass of the vehicle, Kf is the cornering power of the front wheel, Kr is the cornering power of the rear wheel, lf is the distance from the center of gravity of the vehicle to the front wheel axis, and lr is the center of gravity of the vehicle. Is the yaw angle, φ ′ is the yaw angular velocity calculated from the yaw angle, V is the vehicle speed, and δ is the target steering angle. A handle angle sensor for acquiring an actual steering angle when the driver steers the handle;
The control device is
A second fuzzy based on the magnitude of an angle deviation value between the target steering angle and the acquired actual steering angle, and an angular speed deviation value between the target steering angular speed and the acquired actual steering angle. A sudden steering additional flow rate calculating means for calculating a sudden steering additional flow rate according to a rule;
First corrected flow rate calculating means for calculating a first corrected flow rate by adding the additional flow rate during the sudden steering to the basic flow rate;
The power steering system according to any one of claims 1 to 3, further comprising second discharge flow rate control means for controlling the discharge flow rate of the pump to be the first corrected flow rate. It has unevenness acquisition means for acquiring vehicle vertical acceleration, roll acceleration, and pitch angular velocity,
The control device is
An uneven flow additional flow rate calculating means for calculating an uneven flow additional flow rate according to a third fuzzy rule based on the magnitudes of the acquired vehicle vertical acceleration, roll acceleration, and pitch angular velocity, and
Second corrected flow rate calculating means for calculating a second corrected flow rate by adding the irregular flow additional flow rate to the basic flow rate;
The power steering system according to any one of claims 1 to 4, further comprising third discharge flow rate control means for controlling the discharge flow rate of the pump to be the second corrected flow rate.   A vehicle comprising the power steering system according to any one of claims 1 to 5. In a control method of a power steering system for controlling a discharge flow rate of a hydraulic fluid of a pump that supplies hydraulic fluid to a steering assist device that assists steering performance of a steering wheel,
Always get vehicle status and road status,
Based on the obtained vehicle state and road state, the target steering angle and the target steering angular velocity are calculated,
A basic flow rate is calculated according to a first fuzzy rule based on the calculated target steering angle and the target steering angular velocity,
A control method for a power steering system , wherein the discharge flow rate of the pump is always controlled to be the basic flow rate.