JP2010188799A - Steering control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering control device for a vehicle that continues control in giving assist force even if the reliability of some of a plurality of sensors is reduced. <P>SOLUTION: An electronic control unit 25 determines respective reliability levels regarding detection accuracy of a steering torque sensor 23 and a motor rotation angle sensor 24 based on a voltage V-BAT of a power source detected by a battery voltage sensor 21. Further, a unit 25 changes assist characteristic for determining a relationship of steering torque T or a rotation angle Θ detected by the sensors 23, 24 and torque given to turning operation of a steering wheel 11 by a driver based on the determined reliability level. Namely, the unit 25 changes the assist characteristic using a detection value by the sensor in which the reliability level is deteriorated of the sensors 23, 24, and does not change the assist characteristic using the detection value by the sensor in which the reliability level is not deteriorated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is detected by an electric motor that applies an assist force to the operation of the steering wheel, a plurality of sensors that respectively detect at least a plurality of physical quantities that change in accordance with the operation of the steering wheel, and the plurality of sensors. The present invention relates to a vehicle steering control device including an assist control unit that calculates a target assist force based on the physical quantity and that drives and controls the electric motor based on the calculated target assist force.

  Conventionally, for example, as shown in Patent Document 1 below, an electric power steering device that accurately detects an abnormality in a torque sensor device is known. This conventional electric power steering device is adapted to determine abnormality of the torque sensor device and the power supply circuit at normal time, and when the power supply voltage from the power supply circuit is lowered, the abnormality detection of the torque sensor device is prohibited, When the power supply voltage supplied from the battery to the power supply circuit decreases, the abnormality detection of the power supply circuit is prohibited. Further, when an abnormality occurs in the torque sensor device, an assist force is applied to the turning operation of the steering wheel by controlling the rotation of the electric motor using the steering torque held before the abnormality occurs. It is supposed to be.

  Further, conventionally, as shown in, for example, Patent Document 2 below, an acceleration sensor abnormality detection device is also known. This conventional abnormality detection device corrects an abnormality detection threshold as needed based on fluctuations in the power supply voltage, and detects an abnormality of the acceleration sensor by comparing the detected acceleration with the abnormality detection threshold. It has become.

  Furthermore, conventionally, for example, as shown in Patent Document 3 below, a constant current control device having an abnormality diagnosis function is also known. In this conventional constant current control device, whether the current sensor and the overcurrent sensor function normally by setting the switching elements connected in series before the start of the constant current control to the on state at the same time and making the power supply short-circuited in a pseudo manner. Diagnose whether or not. In this conventional constant current control device, the diagnostic accuracy can be improved by correcting the diagnostic threshold according to the power supply voltage.

JP 2001-122143 A JP 2000-206144 A Japanese Unexamined Patent Publication No. 7-337092

  By the way, in the electric power steering apparatus, when the assist force is applied in order to reduce the burden on the steering wheel operation by the driver, for example, detection values detected by a plurality of sensors mounted on the vehicle such as a torque sensor are used. And determine the magnitude of the assist force. For this reason, the reliability of the detected value to be detected is an important factor in providing an appropriate assist torque.

  That is, in a situation where the detection value detected by each sensor is highly reliable, an appropriate assisting force can be applied to the operation of the steering wheel by the driver. On the other hand, in a situation where the reliability of the detected value detected is low, an appropriate assist force cannot always be applied, and the assist force application control may be stopped. However, if the entire assist force application control is stopped in a situation where some of the sensors are low in reliability, the assist force application control using the detection value by the highly reliable sensor is also stopped. There is concern about the impact on the driver.

  The present invention has been made in order to cope with the above-described problem, and an object of the present invention is to reduce the reliability of some of a plurality of sensors mounted on a vehicle and used for steering control. Even so, an object of the present invention is to provide a vehicle steering control device capable of continuing assist force application control.

  In order to achieve the above object, the present invention is characterized by an electric motor that applies an assisting force to an operation of a steering wheel, and a plurality of physical quantities that respectively detect at least a plurality of physical quantities that change in accordance with the operation of the steering wheel. Steering control of a vehicle comprising: a sensor; and an assist control unit that calculates a target assist force based on each physical quantity detected by the plurality of sensors and drives and controls the electric motor based on the calculated target assist force In the apparatus, a reliability level determination unit that determines a reliability level representing each reliability related to detection accuracy of the plurality of sensors, and a reliability level of each of the plurality of sensors determined by the reliability level determination unit And determining a relationship between each physical quantity detected by the plurality of sensors and the target assist force. In that a assist characteristic changing means for changing the assist characteristic.

  In this case, the reliability level determination means is a determination set in advance according to a change in detection accuracy for each of the plurality of sensors having the same magnitude as the voltage supplied to the plurality of sensors from a power source mounted on the vehicle. Based on the comparison with the voltage, it is preferable to determine a reliability level representing the reliability regarding the detection accuracy of the plurality of sensors. In this case, for example, the voltage supplied from the power source to the plurality of sensors decreases. It is better to determine that the reliability level is getting worse as it goes.

  Further, in this case, the reliability level determination means is configured to compare the operation temperature of the plurality of sensors with an operation guaranteed temperature range that is preset for each of the plurality of sensors and guarantees detection accuracy. In this case, for example, the reliability level deteriorates as the operating temperatures of the plurality of sensors deviate from the guaranteed operating temperature range. It is good to judge.

  Further, in this case, the assist characteristic changing unit is configured to change the assist characteristic corresponding to the physical quantity detected by the sensor determined by the reliability level determination unit to be deteriorated in the reliability level among the plurality of sensors. The sensor is changed so that the magnitude of the target assist force with respect to the detected physical quantity is small, and the reliability level determination unit determines that the reliability level is not deteriorated among the plurality of sensors. It is preferable not to change the assist characteristic corresponding to the physical quantity detected by.

  According to these, the reliability level regarding the detection accuracy of the plurality of sensors mounted on the vehicle can be individually determined based on, for example, the magnitude of the voltage supplied from the power source or the operating temperature. . Then, according to the respective reliability levels, the assist characteristics for determining the relationship between the physical quantity detected by the plurality of sensors and the target assist force are individually changed for each corresponding detected physical quantity (that is, for each sensor). can do.

  Thereby, for example, in a situation where there is a sensor with a lowered (deteriorated) reliability level and a sensor with a higher reliability level, the relationship between the physical quantity detected by the sensor with a lowered (deteriorated) reliability level and the target assist force It is possible to change only the assist characteristic for determining the difference, and not to change the assist characteristic for determining the relationship between the physical quantity detected by the sensor having a high reliability level and the target assist force.

  As a result, even in a situation where sensors with different reliability levels exist, it is possible to continue assisting the steering wheel operation by the driver by combining assist characteristics that are changed according to these different reliability levels. . Therefore, even when the reliability of some of the plurality of sensors is reduced, the assist force application control can be continued and the influence on the driver can be minimized.

It is the schematic which shows the structure of the electric power steering apparatus to which the steering control apparatus which concerns on this invention is applied. FIG. 2 is a functional block diagram functionally representing computer program processing (assist control) executed by the electronic control unit of FIG. 1. It is a graph which shows the assist characteristic (assist torque map 1) showing the relationship between the steering torque and the target assist torque which the assist torque calculating part of FIG. 2 refers. 3 is a graph showing assist characteristics (inertia control torque map 1) representing a relationship between a rotational angular acceleration and a target inertia control torque referred to by a motor inertia control torque calculation unit in FIG. 2; 3 is a graph showing an assist characteristic (damping control torque map 1) representing a relationship between a rotation angular velocity and a target damping control torque referred to by the motor inertia control torque calculation unit of FIG. It is a flowchart of the reliability level determination program performed by the electronic control unit of FIG. It is a figure for demonstrating determination of a reliability level. It is a flowchart of the assist characteristic change program performed by the electronic control unit of FIG. It is a graph which shows the assist characteristic (assist torque map 2) showing the relationship between the steering torque and the target assist torque which the assist torque calculating part of FIG. 2 refers. It is a graph which shows the assist characteristic (assist torque map 3) showing the relationship between the steering torque and the target assist torque which the assist torque calculating part of FIG. 2 refers. 3 is a graph showing an assist characteristic (inertia control torque map 2) representing a relationship between a rotation angular acceleration and a target inertia control torque referred to by a motor inertia control torque calculation unit in FIG. 2; 3 is a graph showing an assist characteristic (damping control torque map 2) representing a relationship between a rotational angular velocity and a target damping control torque referred to by the motor inertia control torque calculation unit of FIG. 3 is a graph showing assist characteristics (inertia control torque map 3) representing a relationship between a rotational angular acceleration and a target inertia control torque referred to by the motor inertia control torque calculation unit of FIG. 3 is a graph showing an assist characteristic (damping control torque map 3) representing a relationship between a rotation angular velocity and a target damping control torque referred to by the motor inertia control torque calculation unit of FIG.

  Hereinafter, a vehicle steering control device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an electric power steering apparatus 10 to which a vehicle steering control apparatus according to this embodiment is applied.

  The electric power steering apparatus 10 includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering shaft 12, and the lower end of the steering shaft 12 is connected to the steered gear unit U.

  The steered gear unit U is, for example, a gear unit adopting a rack and pinion type, and the rotation of the pinion gear 13 integrally assembled to the lower end of the steering shaft 12 is transmitted to the rack bar 14. Yes. The steered gear unit U has an electric motor 15 (hereinafter referred to as an EPS motor 15) for reducing an operation force (more specifically, steering torque) input to the steering handle 11 by the driver. Called). The assist force (more specifically, assist torque) generated by the EPS motor 15 is transmitted to the rack bar 14.

  With this configuration, the rotational force of the steering shaft 12 accompanying the turning operation of the steering handle 11 by the driver is transmitted to the rack bar 14 via the pinion gear 13, and the assist torque of the EPS motor 15 is transmitted to the rack bar 14. Is done. As a result, the rack bar 14 is displaced in the axial direction by the rotational force from the pinion gear 13 and the assist torque of the EPS motor 15. Therefore, the left and right front wheels FW1, FW2 connected to both ends of the rack bar 14 are steered in the left-right direction.

  Next, the electric control device 20 as a steering control device that controls the operation of the above-described EPS motor 15 will be described. The electric control device 20 operates by receiving power from a power supply (battery) (not shown), and detects a physical quantity that changes as the battery voltage sensor 21, the vehicle speed sensor 22, and the steering handle 11 rotate. A steering torque sensor 23 and a motor rotation angle sensor 24 are provided as a plurality of sensors. The battery voltage sensor 21 detects a battery voltage V_BAT (not shown) and outputs a signal corresponding to the voltage V_BAT. The vehicle speed sensor 22 detects the vehicle speed S of the vehicle and outputs a signal corresponding to the vehicle speed S.

  The steering torque sensor 23 is assembled to the steering shaft 12, detects a steering torque T input to the steering shaft 12 when the driver rotates the steering handle 11, and outputs a signal corresponding to the steering torque T. Output. The steering torque sensor 23 outputs the steering torque T when the steering handle 11 is turned rightward as a positive value, and the steering torque T when the steering handle 11 is turned leftward. Is output as a negative value.

  Here, as the steering torque sensor 23, a sensor of a type that changes an electric resistance or a magnetic resistance in accordance with a twist angle of a torsion bar provided in the middle of the steering shaft 12 and outputs a voltage signal corresponding thereto. For this reason, in this embodiment, two sets of resolver sensors are employed as the steering torque sensor 23. As is well known, the resolver sensor includes a resolver rotor that rotates together with the torsion bar, and a resolver stator that is fixed to the vehicle body so as to face the resolver rotor, and an excitation coil is provided on one of the resolver rotor and the resolver stator. And a pair of secondary windings, which are detection coils, are provided with a phase shift of π / 2. Then, by exciting the primary winding with the SIN phase signal, the secondary winding outputs a SIN phase output signal and a COS phase output signal as two types of induced voltage signals corresponding to the rotation angle. Therefore, the steering torque sensor 23 using the resolver sensor detects the rotation angle position by obtaining the amplitude ratio of the SIN phase output signal and the COS phase output signal, and detects the steering torque T corresponding to the rotation angle position. .

  The motor rotation angle sensor 24 is assembled to the EPS motor 15, detects a rotation angle Θ from a preset reference rotation position, and outputs a signal corresponding to the rotation angle Θ. The motor rotation angle sensor 24 relates to the rotation direction of the EPS motor 15, and the rotation angle when the EPS motor 15 applies assist torque to the rack bar 14 to steer the left and right front wheels FW1, FW2 to the right. Θ is output as a positive value, and the rotation angle Θ when assist torque is applied to the rack bar 14 in order to steer the left and right front wheels FW1, FW2 to the left is output as a negative value.

  The electric control device 20 includes an electronic control unit 25 that controls the operation of the EPS motor 15. The electronic control unit 25 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operation of the EPS motor 15. For this reason, the respective sensors 21 to 24 are connected to the input side of the electronic control unit 25, and the EPS motor 15 is used as described later by using the detected values detected by the sensors 21 to 24. Control the drive. On the other hand, a drive circuit 26 for driving the EPS motor 15 is connected to the output side of the electronic control unit 25.

  Next, a diagram representing functions realized by computer program processing in the electronic control unit 25 regarding drive control of the EPS motor 15 by the electric control device 20 (more specifically, the electronic control unit 25) configured as described above. This will be described with reference to FIG. The electronic control unit 25 includes an assist control unit 30 that controls driving of the EPS motor 15 and applies appropriate assist torque in order to reduce a burden associated with a turning operation of the steering handle 11 by the driver. . In the following description, the steering torque T and the rotation angle Θ that change according to the turning operation of the steering handle 11 by the driver and the torque (assist force) that is applied by driving the EPS motor 15 are controlled. The relationship is called assist characteristics.

  The assist control unit 30 inputs an assist torque calculation unit 31 that calculates a target assist torque Ta for reducing the steering torque T input by the driver, and the inertia with respect to the rotation of the EPS motor 15. A motor inertia control unit 32 that calculates a target inertia control torque Ti for reducing the steering torque T, and a steering torque T that is input by the driver with respect to vibration that occurs with a change in the rotational drive direction of the EPS motor 15. A damping control unit 33 for calculating a target damping control torque Td for reduction. Note that, by calculating the target damping control torque Td, for example, the behavior of the vehicle at the end of the turn (so-called convergence) can be improved, and the stability can be improved.

  The assist torque control unit 30 includes an adder 34 that adds the target torques Ta, Ti, and Td output from the assist torque calculation unit 31, the motor inertia control torque calculation unit 32, and the damping control torque calculation unit 33, and a damping. A differentiator 35 that supplies the rotational angular velocity Θ ′ of the EPS motor 15 to the control torque calculator 33 and a differentiator 36 that supplies the rotational angular acceleration Θ ″ of the EPS motor 15 to the motor inertia control torque calculator 32. And. First, the assist torque calculation unit 31 will be described.

  The assist torque calculator 31 calculates a target assist torque Ta that increases as the absolute value of the steering torque T detected by the steering torque sensor 23 increases. Therefore, the assist torque calculation unit 31 refers to, for example, an assist torque map (corresponding to an assist torque map 1 described later) as shown in FIG. 3, and a target assist torque corresponding to the absolute value of the input steering torque T Calculate Ta. Here, in the assist torque map, when the steering torque T is small, a dead zone for setting the assist torque Ta to be applied to the turning operation of the steering handle 11 by the driver to “0” is set. That is, in the dead zone, the assist torque calculator 31 calculates the target assist torque Ta as “0” by regarding the magnitude of the steering torque T detected by the steering torque sensor 23 as “0”. Then, the assist torque calculator 31 outputs the calculated target assist torque Ta to the adder 34.

  The assist torque map referred to by the assist torque calculation unit 31 is set for each representative vehicle speed S. As the vehicle speed S increases, the target assist torque Ta becomes relatively small, and the vehicle speed S The target assist torque Ta is set so as to increase relatively with the decrease. Therefore, instead of using such an assist torque map, for example, the target assist torque Ta is expressed as a function of the steering torque T and the vehicle speed S, and the target assist torque Ta is calculated using this function. It is also possible.

  The motor inertia control torque calculator 32 calculates a target inertia control torque Ti that changes according to the absolute value of the rotational angular acceleration Θ ″ of the EPS motor 15 supplied from the differentiator 36. Therefore, the motor inertia control torque calculation unit 32 refers to, for example, an inertia control torque map (corresponding to an inertia control torque map 1 described later) as shown in FIG. The target inertia control torque Ti corresponding to the value is calculated. Here, the differentiator 36 performs time differentiation on the rotational angular velocity Θ ′ of the EPS motor 15 supplied from the differentiator 35, and the differentiator 35 detects the rotational angle Θ of the EPS motor 15 detected by the motor rotational angle sensor 24. Is differentiated with respect to time, and the rotational angular velocity Θ ′ is calculated. Then, the motor inertia control torque calculator 32 outputs the calculated target inertia control torque Ti to the adder 34. Instead of using such an inertia control torque map, for example, the target inertia control torque Ti is expressed as a function of the rotational angular acceleration Θ '', and the target inertia control torque Ti is calculated using this function. It is also possible to implement.

  The damping control torque calculator 33 calculates a target damping control torque Td that changes according to the absolute value of the rotational angular velocity Θ ′ of the EPS motor 15 supplied from the differentiator 35. For this reason, the damping control torque calculator 33 corresponds to the absolute value of the input rotational angular velocity Θ ′ with reference to a damping control torque map (corresponding to a damping control torque map 1 described later) as shown in FIG. 5, for example. The target damping control torque Td to be calculated is calculated. Then, the damping control torque calculator 33 outputs the calculated target damping control torque Td to the adder 34. Instead of using such a damping control torque map, for example, the target damping control torque Td is expressed as a function of the rotational angular velocity Θ ′, and the target damping control torque Td is calculated using this function. It is also possible.

  The adder 34 adds the output target torques Ta, Ti, Td, and has a predetermined relationship with the magnitude of the added total torque Tt (corresponding to the assist force), and supplies it to the EPS motor 15. The motor current command value representing the current is determined. The motor current command value determined in this way is supplied to the drive circuit 26, and the drive circuit 26 supplies a drive current corresponding to the supplied motor current command value to the EPS motor 15. Thus, the EPS motor 15 transmits the total torque Tt reflecting the target assist torque Ta, the target inertia control torque Ti, and the target damping control torque Td to the rack bar 14, so that the driver perceives a good steering feeling. Meanwhile, the steering handle 11 can be turned.

  By the way, when the EPS motor 15 is driven and controlled as described above, in particular, the reliability (that is, the detection accuracy) of the steering torque sensor 23 and the motor rotation angle sensor 24, in other words, the detection values of the sensors 23 and 24. Reliability is important. The reliability changes depending on the electric power supplied from the power source (battery) to the steering torque sensor 23 and the motor rotation angle sensor 24, more specifically, the change in the supplied voltage. For this reason, the electronic control unit 25 determines the reliability level of the steering torque sensor 23 and the motor rotation angle sensor 24 that change in accordance with the voltage change of the power source (battery). Hereinafter, the determination of the reliability level will be described.

  When an ignition switch (not shown) is turned on by the driver, the electronic control unit 25 starts execution of the reliability level determination program shown in FIG. 6 in step S10. In step S11, the electronic control unit 25 inputs the voltage V_BAT detected by the battery voltage sensor 21, and proceeds to step S12.

  In step S12, the electronic control unit 25 determines that the voltage V_BAT input from the battery voltage sensor 21 in step S11 is normal as the magnitude of the voltage supplied to the steering torque sensor 23 and the motor rotation angle sensor 24. In order to determine whether or not there is a determination voltage, it is determined whether or not it is greater than a predetermined determination voltage VB_TH1.

  That is, if the input voltage V_BAT is greater than the determination voltage VB_TH1, the electronic control unit 25 determines that the voltage of the power source is sufficiently large and normal, and thus determines “Yes” and proceeds to step S13. In step S13, the electronic control unit 25 supplies a stable voltage to the steering torque sensor 23 and the motor rotation angle sensor 24 from the power source. T) and the reliability level of the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) are set to “1” representing the highest reliability level. On the other hand, if the input voltage V_BAT is equal to or lower than the determination voltage VB_TH1, the voltage of the power supply has decreased, so the electronic control unit 25 determines “No” and proceeds to step S14.

  In step S14, for example, the electronic control unit 25 is disposed in the vicinity of the driver's seat, activates a notification device that notifies the driver of a voltage drop of the power supply by light or sound, and the voltage of the power supply is supplied to the driver. Informs that it is decreasing. In step S15, the electronic control unit 25 determines whether or not the input voltage V_BAT is greater than a determination voltage VB_TH2 set to be smaller than the determination voltage VB_TH1.

  That is, if the input voltage V_BAT is higher than the determination voltage VB_TH2, the electronic control unit 25 determines “Yes” because the voltage of the power supply is slightly reduced, and proceeds to step S16. In step S16, the electronic control unit 25 slightly reduces the magnitude of the voltage supplied from the power source to the steering torque sensor 23 and the motor rotation angle sensor 24. The reliability level of the steering torque T) and the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) is set to “2”, which is inferior to “1”. On the other hand, if the input voltage V_BAT is equal to or lower than the determination voltage VB_TH2, the voltage of the power source has dropped significantly, so the electronic control unit 25 determines “No” and proceeds to step S17. In step S17, the electronic control unit 25 greatly reduces the magnitude of the voltage supplied from the power source to the steering torque sensor 23 and the motor rotation angle sensor 24. The reliability level of the detected steering torque T) and the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) is set to “3”, which is inferior to “2”.

  As described above, when the processing in step S13, step S16 or step S17 is executed, the electronic control unit 25 once ends the execution of the reliability level determination program in step S18. Then, after a predetermined short time has elapsed, the electronic control unit 25 again starts executing the reliability level determination program in step S10. Here, in the determination process of the magnitude of the voltage V_BAT in the steps S12 and S15, when the magnitude is determined by comparing the voltage V_BAT with the determination voltage VB_TH1 and the determination voltage VB_TH2, the voltage V_BAT slightly changes. Accordingly, the “Yes” determination or the “No” determination may be repeated (so-called hunting occurs).

  Therefore, in the determination process of the voltage V_BAT in the steps S12 and S15, as shown in FIG. 7, a determination voltage VB_TH11 slightly larger than the determination voltage VB_TH1 is set and slightly smaller than the determination voltage VB_TH2. It is preferable to provide a hysteresis in the determination condition by setting a large determination voltage VB_TH21 to. Thereby, it is possible to effectively prevent the occurrence of the hunting of the determination accompanying a slight change in the voltage V_BAT, and to determine the magnitude of the voltage V_BAT more accurately. As a result, the reliability levels of the steering torque sensor 23 (ie, the detected steering torque T) and the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) can be set appropriately.

  By the way, in the steering torque sensor 23 and the motor rotation angle sensor 24 that are representatively described in the present embodiment, for example, the steering torque sensor 23 is more easily affected by a voltage change of the power source (battery). For this reason, when the assist torque calculating unit 31 calculates the target assist torque Ta using the steering torque T detected by the steering torque sensor 23, for example, the basic assist torque corresponding to a large proportion of the target assist torque Ta is detected. If the setting is made based on the steering torque T, the steering feeling perceived by the driver may deteriorate.

  Therefore, in determining the detection accuracy, that is, the reliability level of the steering torque sensor 23 and the motor rotation angle sensor 24, the determination voltage VB_TH1 and the determination voltage VB_TH2 are set for each sensor to be determined. Specifically, in the present embodiment, the determination voltage VB_TH1 and the determination voltage VB_TH2 of the steering torque sensor 23 are set to values larger than the determination voltage VB_TH1 and the determination voltage VB_TH2 of the motor rotation angle sensor 24.

  As described above, the determination voltage VB_TH1 and the determination voltage VB_TH2 for the steering torque sensor 23 and the determination voltage VB_TH1 and the determination voltage VB_TH2 for the motor rotation angle sensor 24 are set and the reliability levels are determined. Situations with different levels of reliability occur.

  That is, when the voltage V_BAT supplied from the battery voltage sensor 21 is smaller than the determination voltage VB_TH1 for the steering torque sensor 23 and larger than the determination voltage VB_TH1 for the motor rotation angle sensor 24, the electronic control unit 25 The reliability level of the steering torque sensor 23 (ie, the detected steering torque T) is determined as “2”, and the reliability level of the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) is determined as “1”. When the voltage V_BAT supplied from the battery voltage sensor 21 is smaller than the determination voltage VB_TH2 for the steering torque sensor 23 and larger than the determination voltage VB_TH2 for the motor rotation angle sensor 24, the electronic control unit 25 is The reliability level of the steering torque sensor 23 (ie, the detected steering torque T) is determined as “3”, and the reliability level of the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) is determined as “2”. The reliability level determined in this way is stored in a predetermined storage position in a RAM (not shown) of the electronic control unit 25.

  On the other hand, the electronic control unit 25 changes the assist characteristics according to the respective reliability levels of the steering torque sensor 23 and the motor rotation angle sensor 24 determined by executing the reliability level determination program. Hereinafter, the change of the assist characteristic will be described in detail.

  When the electronic control unit 25 determines the reliability levels of the steering torque sensor 23 and the motor rotation angle sensor 24 (that is, the detected steering torque T and the detected rotation angle Θ), the electronic control unit 25 executes the assist characteristic changing program shown in FIG. . Specifically, the electronic control unit 25 starts executing the assist characteristic changing program in step S30, and inputs each reliability level stored in the RAM in step S31.

  Then, the electronic control unit 25 changes the assist characteristic, more specifically, the assist torque map in accordance with the reliability level of the steering torque sensor 23 (that is, the detected steering torque T) in steps S32 to S36 of the assist characteristic changing program. In steps S37 to S41, the assist characteristics, more specifically, the inertia control torque map and the damping control torque map are changed according to the reliability level of the motor rotation angle sensor 24 (that is, the detected rotation angle Θ). Hereinafter, first, each step process of step S32 to step S36 will be described.

  In step S32, the electronic control unit 25 determines whether or not the reliability level of the steering torque sensor 23 input in step S31 is “1”. That is, if the reliability level of the steering torque sensor 23 is “1”, the electronic control unit 25 determines “Yes” and proceeds to step S33.

  In step S33, the electronic control unit 25 employs the assist torque map 1 having the smallest dead zone shown in FIG. 3 because the reliability level of the steering torque sensor 23 is the highest. This is because the steering torque sensor 23 has high detection accuracy and the steering torque T can be detected very accurately. As described above, by using the assist torque map 1 having the smallest dead zone, the assist torque calculation unit 31 of the assist torque control unit 30 is appropriate even for the value of the detected steering torque T near “0”. The assist torque Ta can be calculated.

  On the other hand, if the reliability level of the steering torque sensor 23 is not “1” in step S32, the electronic control unit 25 determines “No” and proceeds to step S34.

  In step S34, the electronic control unit 25 determines whether or not the reliability level of the steering torque sensor 23 is “2”. That is, if the reliability level of the steering torque sensor 23 is “2”, the electronic control unit 25 determines “Yes” and proceeds to step S35.

  In step S35, the electronic control unit 25 employs the assist torque map 2 having a large dead zone, as shown in FIG. 9, corresponding to the reliability level “2” of the steering torque sensor 23. This is because the detection accuracy of the steering torque sensor 23 decreases (deteriorates) and the detected steering torque T becomes unstable, so the size of the dead zone is set larger than the assist torque map 1 and is perceived by the driver. This is to suppress discomfort. As described above, by using the assist torque map 2 in which the dead zone is set to be large, the assist torque calculation unit 31 of the assist torque control unit 30 can assist the assist torque with respect to a value of the detected steering torque T near “0”. Calculation can be performed with Ta as “0”. As a result, particularly in a situation where the detected steering torque T detected by the steering torque sensor 23 is small and unstable, the assist torque Ta can be set to “0” to suppress the uncomfortable feeling perceived by the driver. it can.

  On the other hand, in step S34, if the reliability level of the steering torque sensor 23 is not “2”, in other words, if the reliability level is “3”, the electronic control unit 25 determines “No” and performs step. Proceed to S36.

  In step S36, since the reliability level of the steering torque sensor 23 is “3”, the electronic control unit 25 employs the assist torque map 3 in which the assist torque Ta is “0” as shown in FIG. . This is because the detection accuracy of the steering torque sensor 23 is significantly lowered (deteriorated) and the detected steering torque T is unstable, so the assist torque Ta determined using this detected steering torque T is set to “0”, This is to suppress the uncomfortable feeling perceived by the driver. As described above, by using the assist torque map 3 in which the assist torque Ta is “0”, the assist torque calculation unit 31 of the assist torque control unit 30 can assist the assist torque Ta in a state where the reliability level is “3”. Can be calculated as “0”. Thereby, in a situation where the detected steering torque T detected by the steering torque sensor 23 becomes unstable, the assist torque Ta can be set to “0”, and the uncomfortable feeling perceived by the driver can be suppressed.

  Here, for example, even when the voltage supplied from the power source (battery) is temporarily reduced and the reliability level of the steering torque sensor 23 is temporarily deteriorated, the voltage is restored and the reliability level is restored. When the torque increases (improves), the assist torque Ta is calculated using the detected steering torque T by employing the assist torque map 1 or the assist torque map 2. In other words, the assist torque map is appropriately changed according to the reliability level of the steering torque sensor 23 (that is, the detected steering torque T), and the assist torque Ta is appropriately calculated based on the assist torque map that is appropriately changed, in other words, based on the assist characteristics. Is done.

  Next, each step process of step S37 to step S41 in the assist characteristic change program will be described.

  After executing step S36, the electronic control unit 25 proceeds to step S37. In step S37, the electronic control unit 25 determines whether or not the reliability level of the motor rotation angle sensor 24 input in step S31 is “1”. That is, if the reliability level of the motor rotation angle sensor 24 is “1”, the electronic control unit 25 determines “Yes” and proceeds to step S38.

  In step S38, the electronic control unit 25 employs the inertia control torque map 1 shown in FIG. 4 and the damping control torque map 1 shown in FIG. 5 because the reliability level of the motor rotation angle sensor 24 is the highest. . This is because the detection accuracy of the motor rotation angle sensor 24 is high and the rotation angle Θ of the EPS motor 15 can be detected very accurately. Thus, by employing the inertia control torque map 1 and the damping control torque map 1, the motor inertia control torque calculation unit 32 and the damping control torque calculation unit 33 of the assist torque control unit 30 are calculated from the detected rotation angle Θ. An appropriate target inertia control torque Ti and target damping control torque Td can be calculated with respect to the rotational angular acceleration Θ ″ and rotational angular velocity Θ ′ of the EPS motor 15.

  On the other hand, if the reliability level of the motor rotation angle sensor 24 is not “1” in step S37, the electronic control unit 25 determines “No” and proceeds to step S39.

  In step S39, the electronic control unit 25 determines whether or not the reliability level of the motor rotation angle sensor 24 is “2”. That is, if the reliability level of the motor rotation angle sensor 24 is “2”, the electronic control unit 25 determines “Yes” and proceeds to step S40.

  In step S40, the electronic control unit 25 adopts the inertia control torque map 2 corresponding to the reliability level “2” of the motor rotation angle sensor 24, as shown in FIG. At the same time, as shown in FIG. 12, a damping control torque map 2 in which the target damping control torque Td (absolute value) is reduced is adopted. This is because the detection rotational angle Θ becomes unstable because the detection accuracy of the motor rotational angle sensor 24 decreases (deteriorates). Therefore, the target inertia control torque Ti is set smaller than the inertia control torque map 1 with respect to the magnitude of the rotational angular acceleration Θ ″, and the target damping control torque Td (absolutely with respect to the magnitude of the rotational angular velocity Θ ′. Value) is set smaller than the damping control torque map 1. Then, by adopting the inertia control torque map 2 and the damping control torque map 2 in this way, the motor inertia control torque calculation unit 32 and the damping control torque calculation unit 33 of the assist torque control unit 30 can detect the value of the detected rotation angle Θ. In such a situation, the target inertia control torque Ti and the target damping control torque Td (absolute value) are calculated to be small, so that the uncomfortable feeling perceived by the driver can be suppressed.

  On the other hand, in step S39, if the reliability level of the motor rotation angle sensor 24 is not “2”, in other words, if the reliability level is “3”, the electronic control unit 25 determines “No”. Proceed to step S41.

  In step S41, since the reliability level of the motor rotation angle sensor 24 is “3”, the electronic control unit 25 has an inertia control torque map 3 that sets the target inertia control torque Ti to “0” as shown in FIG. And a damping control torque map 3 in which the target damping control torque Td is set to “0” as shown in FIG. This is because the detection accuracy of the motor rotation angle sensor 24 is greatly reduced (deteriorated) and the detection rotation angle Θ is unstable, so this detection rotation angle Θ (that is, the rotation angle acceleration Θ ″ or the rotation angular velocity Θ ′). This is because the target inertia control torque Ti and the target damping control torque Td determined using the above are set to “0”.

  Thus, by adopting the inertia control torque map 3 in which the target inertia control torque Ti is “0” and the damping control torque map 3 in which the target damping control torque Td is “0”, the motor of the assist torque control unit 30 The inertia control torque calculation unit 32 and the damping control torque calculation unit 33 can calculate the target inertia control torque Ti and the target damping control torque Td as “0” in a state where the reliability level is “3”. As a result, in a situation where the detected rotation angle Θ detected by the motor rotation angle sensor 24 becomes unstable, the target inertia control torque Ti and the target damping control torque Td are “0”, so that the uncomfortable feeling perceived by the driver is suppressed. be able to.

  Here, for example, even when the voltage supplied from the power source (battery) is temporarily lowered and the reliability level of the motor rotation angle sensor 24 is temporarily deteriorated, the voltage is restored and the reliability is restored. When the level increases (improves), the inertial control torque map 1 and the damping control torque map 1, or the inertial control torque map 2 and the damping control torque map 2 are adopted, and the target inertial control torque Ti and the target damping control torque Td are obtained. Calculated. That is, the inertia control torque map and the damping control torque map are appropriately changed according to the reliability level of the motor rotation angle sensor 24 (that is, the detected rotation angle Θ), and the target inertia control torque Ti and the target damping control torque Td are appropriately changed. The inertial control torque map and the damping control torque map are calculated appropriately based on the assist characteristics.

  As described above, when the process of step S41 is executed, the electronic control unit 25 proceeds to step S42, and once ends the execution of the assist characteristic changing program. Then, after a predetermined short time has elapsed, the electronic control unit 25 starts executing the assist characteristic changing program again in step S30.

  As can be understood from the above description, according to the present embodiment, the reliability level of the steering torque sensor 23 (that is, the detected steering torque T) and the reliability level of the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) Can be determined individually. Then, according to each reliability level, the assist characteristic determined using the detected steering torque T and the assist characteristic determined using the detected rotation angle Θ can be individually changed.

  Thus, for example, in a situation where the reliability level of the motor rotation angle sensor 24 is still high although the reliability level of the steering torque sensor 23 is lowered (deteriorated), the relationship between the detected steering torque T and the target assist torque Ta. It is possible to change only the assist characteristic (assist torque map) for determining. As a result, although the effect of reducing the steering torque T input by the driver to actually rotate the steering handle 11 is slightly impaired, the steering torque T input to the inertia accompanying the rotation of the EPS motor 15 is slightly impaired. The mitigation effect and the mitigation effect of the steering torque T input to the vibration generated with the change in the rotational drive direction of the EPS motor 15 can be sufficiently maintained.

  Thus, according to the present embodiment, even if the reliability level of the steering torque sensor 23 (ie, the detected steering torque T) and the reliability level of the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) are different. By combining the assist characteristics that are changed according to these different reliability levels, the driver can continue to assist the turning operation of the steering handle 11 by the driver. Therefore, the influence on the driver accompanying the assist stop can be minimized.

  In the above embodiment, in the electronic control unit 25, the battery voltage sensor 21 detects the voltage supplied from the power source (battery), and the steering torque sensor 23 (ie, detected steering) according to the detected voltage V_BAT. Torque T) and the reliability level of the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) were determined.

  By the way, each sensor mounted on the vehicle is set with a guaranteed temperature range that guarantees detection accuracy during operation. That is, when the sensor operates within the guaranteed temperature range, the target physical quantity can be detected with high detection accuracy, and the detection accuracy decreases as the guaranteed temperature range is exceeded. Accordingly, the operating temperatures of the steering torque sensor 23 and the motor rotation angle sensor 24 are detected, and the steering temperature sensor 23 (that is, the detected steering torque T) and the motor rotation angle sensor 24 ( That is, it is possible to determine the reliability level of the detected rotation angle Θ). Hereinafter, this modification will be described.

  In this modification, temperature sensors for detecting the operating temperature are provided for the steering torque sensor 23 and the motor rotation angle sensor 24, respectively. The operating temperature detected by each temperature sensor is output to the electronic control unit 25, and the electronic control unit 25 outputs each operating temperature of the output steering torque sensor 23 and motor rotation angle sensor 24. The reliability level is determined based on

  That is, also in this modification, the electronic control unit 25 executes the reliability determination program shown in FIG. 6 as in the above embodiment. However, in this case, the input process in step S11, the determination process in steps S12 and S15, and the notification process in step S14 are each changed.

  Specifically, in the changed step S11, the electronic control unit 25 inputs the operating temperatures of the steering torque sensor 23 and the motor rotation angle sensor 24 from each temperature sensor. In the subsequent changed step S12, the electronic control unit 25 inputs the respective guaranteed temperature ranges set in advance for each of the steering torque sensor 23 and the motor rotation angle sensor 24 in the changed step S11. Each operating temperature is compared, and if the operating temperature is within the guaranteed temperature range, “Yes” is determined and the process proceeds to step S13, where the steering torque sensor 23 (ie, detected steering torque T) and motor rotation angle sensor 24 (ie, detected) are detected. The reliability level of the rotation angle Θ is set to “1”.

  On the other hand, if the operating temperature is not within the guaranteed temperature range, the electronic control unit 25 determines “No” in the changed step S12, and proceeds to the changed step S14. In the changed step S14, the electronic control unit 25 notifies the driver that the operating temperature of at least one of the steering torque sensor 23 and the motor rotation angle sensor 24 is out of the guaranteed temperature range. Then, the electronic control unit 25 proceeds to the subsequent changed step S15.

  In the changed step S15, the electronic control unit 25 compares the operating temperature with a temperature range larger than the guaranteed temperature range set in advance for each of the steering torque sensor 23 and the motor rotation angle sensor 24, and this large temperature. If the operating temperature is within the range, it is determined as “Yes” and the process proceeds to Step S16. In step S16, the electronic control unit 25 sets the reliability levels of the steering torque sensor 23 (ie, the detected steering torque T) and the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) to “2”.

  On the other hand, if the operating temperature is not within the temperature range larger than the guaranteed temperature range, the electronic control unit 25 determines “No” in the changed step S15, and proceeds to step S17. In step S17, the electronic control unit 25 sets the reliability levels of the steering torque sensor 23 (ie, the detected steering torque T) and the motor rotation angle sensor 24 (ie, the detected rotation angle Θ) to “3”.

  As described above, by executing the changed reliability level determination program, the electronic control unit 25 performs the steering torque sensor 23 (that is, the detected steering torque T) and the motor rotation angle sensor 24 (that is, the same as in the above embodiment). The reliability level of the detected rotation angle Θ) can be determined respectively. Then, based on the reliability level determined as described above, the assist characteristic can be changed according to the reliability level by executing the assist characteristic changing program in the same manner as in the above embodiment. Therefore, also in this modification, the same effect as the above embodiment can be obtained.

  In carrying out the present invention, the present invention is not limited to the above-described embodiment and its modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above embodiment, the steering torque sensor 23 (that is, the detected steering torque T) and the motor rotation are based on the magnitude of the voltage V_BAT supplied from the power source (battery) to the steering torque sensor 23 and the motor rotation angle sensor 24. The reliability of the angle sensor 24 (that is, the detected rotation angle Θ) was determined. In the above modification, based on the operating temperatures of the steering torque sensor 23 and the motor rotation angle sensor 24, the steering torque sensor 23 (that is, the detected steering torque T) and the motor rotation angle sensor 24 (that is, the detected rotation angle Θ). Implemented to determine confidence level.

  However, the reliability levels of the steering torque sensor 23 (that is, the detected steering torque T) and the motor rotation angle sensor 24 (that is, the detected rotation angle Θ) are, for example, signal strengths output from these sensors 23 and 24 to the electronic control unit 25. It is also possible to make a determination based on whether or not there is an abnormality in the communication line. Also in this case, for example, by determining the reliability level corresponding to each signal strength, the same effect as in the above embodiment and the modified example can be expected.

  Moreover, in the said embodiment and its modification, the reliability level was implemented as three levels "1"-"3". However, the number of reliability levels is not limited to this, and it goes without saying that the levels can be further divided and implemented. By subdividing the levels in this way, the assist characteristics can be changed more finely, and steering control that provides more appropriate assist torque becomes possible.

  In the above-described embodiment and its modifications, the reliability levels of the steering torque sensor 23 (that is, the steering torque T) and the motor rotation angle sensor 24 (that is, the rotation angle Θ) are determined. Then, the assist characteristic (target assist torque Ta) using the steering torque T and the assist characteristic (target inertia control torque Ti and target damping control torque Td) using the rotation angle Θ are changed according to the determined reliability level. Implemented.

  In this case, instead of the steering torque sensor 23 and the motor rotation angle sensor 24, various sensors that are mounted on the vehicle and detect a physical quantity that changes in accordance with the turning operation of the steering handle 11, for example, the steering handle 11 by the driver. Steering angle sensor that detects the amount of rotation operation, steering angle sensor that detects the amount of steering of the left and right front wheels FW1, FW2, a motor current detection sensor that is provided in the EPS motor 15 and detects a drive current, and a motor of the EPS motor 15 It is also possible to employ a motor voltage sensor or the like that detects the terminal voltage.

  For example, instead of or in addition to the motor rotation angle sensor 24, a steering angle sensor is adopted, and the EPS motor 15 is driven in accordance with a change in the amount of rotation (steering angle) of the steering handle 11 detected by the steering angle sensor. Assume a controlled case. In this case, for example, the inertia control torque map 1 (and the damping control torque map 1) is employed when the reliability level of the steering angle sensor is “1”, and the inertia control is performed when the reliability level is “2”. The torque map 2 (and the damping control torque map 2) is adopted, and the inertia control torque map 3 (and the damping control torque map 3) is adopted when the reliability level is “3”. As described above, even when other sensors are employed, the reliability levels of the various sensors are determined and determined by using the detection values of these sensors, as in the above-described embodiment and its modifications. By changing the assist characteristic or other characteristics depending on the reliability level, the same effects as those of the above-described embodiment and its modifications can be expected.

  Furthermore, in the above embodiment and the modification, the assist torque calculation unit 31, the motor inertia control unit 32, and the damping control unit 33 of the assist control unit 30 are respectively set to the target assist torque Ta, the target inertia control torque Ti, and the target damping control. The torque Td was calculated, and the adder 34 added the target torques Ta, Ti and Td to calculate the total torque Tt. In this case, it is possible to omit the adder 34 and output the target assist torque Ta, the target inertia control torque Ti, and the target damping control torque Td to the drive circuit 26. Even in this case, the same effects as those of the above-described embodiment and the modification can be obtained by changing the assist torque map, the inertia control torque map, and the damping control torque map according to the reliability level.

FW1, FW2 ... front left and right wheels, 10 ... electric power steering device, 11 ... steering handle, 12 ... steering shaft, 13 ... pinion gear, 14 ... rack bar, 15 ... EPS motor, 20 ... electric control device, 21 ... battery voltage sensor , 22 ... Vehicle speed sensor, 23 ... Steering torque sensor, 24 ... Motor rotation angle sensor, 25 ... Electronic control unit, 26 ... Drive circuit, 30 ... Assist control unit, 31 ... Assist torque calculation unit, 32 ... Motor inertia control torque calculation 33, Damping control torque calculation unit, U ... Steering gear unit

Claims (6)

An electric motor that applies an assisting force to the operation of the steering wheel, a plurality of sensors that respectively detect at least a plurality of physical quantities that change in accordance with the operation of the steering handle, and each physical quantity that is detected by the plurality of sensors. In a vehicle steering control device comprising: an assist control unit that calculates a target assist force based on the calculated target assist force and drives and controls the electric motor based on the calculated target assist force;
A reliability level determination means for determining a reliability level representing each reliability related to the detection accuracy of the plurality of sensors;
Assist characteristics for determining a relationship between each physical quantity detected by the plurality of sensors and the target assist force according to the reliability level of each of the plurality of sensors determined by the reliability level determination unit. A steering control device for a vehicle, comprising: an assist characteristic changing means for changing. The vehicle steering control device according to claim 1,
The reliability level determination means includes
The plurality of sensors based on a comparison between a magnitude of a voltage supplied to the plurality of sensors from a power source mounted on a vehicle and a determination voltage set in advance for each of the plurality of sensors according to a change in detection accuracy. A vehicle steering control device that determines a reliability level representing each reliability related to the detection accuracy of the vehicle. In the vehicle steering control device according to claim 2,
The reliability level determination means includes
The vehicle steering control device according to claim 1, wherein the reliability level is determined to deteriorate as the voltage supplied from the power source to the plurality of sensors decreases. The vehicle steering control device according to claim 1,
The reliability level determination means includes
A reliability level representing the reliability of the detection accuracy of the plurality of sensors based on a comparison between the operation temperature of the plurality of sensors and an operation guaranteed temperature range that is preset for each of the plurality of sensors to guarantee detection accuracy. A steering control device for a vehicle, characterized in that The vehicle steering control device according to claim 4,
The reliability level determination means includes
The vehicle steering control device according to claim 1, wherein the reliability level is determined to be worse as the operating temperatures of the plurality of sensors deviate from the operation guaranteed temperature range. The vehicle steering control device according to claim 1,
The assist characteristic changing means includes
Among the plurality of sensors, the assist characteristic corresponding to the physical quantity detected by the sensor determined that the reliability level has deteriorated by the reliability level determination means is expressed by the target assist force with respect to the detected physical quantity. Change the size to be smaller,
Steering of a vehicle characterized by not changing the assist characteristic corresponding to the physical quantity detected by a sensor determined by the reliability level determination means that the reliability level is not deteriorated among the plurality of sensors. Control device.

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