JP5018166B2 - Steering device - Google Patents

Description

  The present invention relates to a steering-by-wire type steering apparatus that mechanically separates a steering wheel operation unit and a steering unit that steers a wheel and drives a steering actuator in accordance with the steering wheel operation.

  Conventionally, this type of vehicle steering apparatus has a steering handle that is operated by a driver, a reaction force applying apparatus that applies a steering reaction torque to the operation of the steering handle, and a wheel that rotates according to the operation of the steering handle. And a steered wheel drive device that steers the steered wheels.

  The reaction force imparting device has a spring reaction force torque component that provides a force to return the steering handle to the neutral position and a friction reaction force torque component that simulates the frictional resistance of the steering mechanism in order to give an appropriate response to the steering operation. The target steering reaction torque is calculated by adding a plurality of torque components such as a viscous reaction force torque component that simulates the viscous resistance generated by the steering handle turning operation, and a reaction force actuator (for example, an electric motor) ) Is controlled to apply a target steering reaction torque to the steering wheel. In calculating the target steering reaction torque, the steering angle of the steering wheel detected by the steering angle sensor, the steering angular velocity obtained by differentiating the steering angle with time, the steering angular acceleration obtained by differentiating the steering angular velocity with time, and the like are used. For example, the spring reaction force torque component is calculated in proportion to the steering angle, and the friction reaction force torque component is calculated in proportion to the steering angular velocity.

  The steered wheel drive device calculates a target turning angle based on the steering angle detected by the steering angle sensor, and steers the steering angle so that the turning angle detected by the steering angle sensor becomes the target turning angle. An actuator (for example, an electric motor) is driven to steer the steered wheels.

  In such a steering-by-wire type steering device, it is necessary to prevent a shift between the neutral position of the steering angle sensor (the neutral position of the steering wheel) and the neutral position of the steering angle sensor (the straight traveling position of the wheel). In particular, when a relative angle sensor is used as a steering angle sensor or a steering angle sensor, there is a possibility that a neutral position shift occurs. In the case of a relative angle sensor, an angle with respect to a reference position is detected. If the reference position is deviated from the actual reference position, the detected angle is deviated accordingly.

Therefore, in the vehicle steering apparatus proposed in Patent Document 1, when the neutral position of the steering angle is detected by the steering angle sensor, the output value of the steering angle sensor is set so that the output of the reaction force actuator becomes zero. In addition, when the neutral position of the turning angle is detected by the turning angle sensor, the output value of the turning angle sensor is corrected so that the output of the turning actuator becomes zero. .
JP 2002-37108 A

  However, even in the vehicle steering device proposed in Patent Document 1, when the turning angle sensor has an abnormality, the steering angle neutral position cannot be detected. I can't do it. Therefore, there is a possibility that a deviation occurs between the neutral position detected by the steering angle sensor and the actual neutral position of the steered wheels. If a deviation occurs between the neutral position of the steering angle and the neutral position of the steered wheels, the restoring force (spring reaction force torque component) to the neutral position of the steering wheel does not work properly. That is, torque is generated in a direction in which the steering handle is shifted from the straight traveling direction by an amount corresponding to the shift of the neutral position. For example, even when the steered wheel is directed straight, if the steering angle sensor value takes a value that deviates from the neutral position, the steering reaction torque is applied by that amount and the steering operation is taken. For this reason, the driver feels uncomfortable.

  The present invention has been made to cope with the above problem, and reduces the uncomfortable feeling given to the driver when the correspondence relationship between the steering angle detected by the steering angle sensor and the actual turning angle of the steered wheels deviates. For the purpose.

To achieve the above object, the present invention includes a steering wheel operated by a driver to steer the vehicle, a steering angle detection means for detecting a steering angle of the steering wheel, steering of the steerable wheels In accordance with the stored correspondence, the turning angle detecting means for detecting the angle, the correspondence storage means for storing the correspondence between the steering angle detected by the steering angle detecting means and the target turning angle, and the stored correspondence A steered wheel steerer for steering steered wheels such that the steered angle detected by the steered angle detector is a target steered angle corresponding to the steering angle detected by the steering angle detector ; A reaction force actuator for applying a reaction force torque to the steering of the steering wheel, and a spring reaction force that is set according to the steering angle detected by the steering angle detection means and serves as a force for returning the steering handle to the neutral position Torque generation And the other reaction force torque component different from the spring reaction force component to calculate the target steering reaction torque, and the calculated target steering reaction torque is applied to the steering of the steering wheel. In the steering-by-wire type steering apparatus provided with the steering reaction force control means for controlling the drive of the reaction force actuator, the correspondence relationship between the steering angle detected by the steering angle detection means and the actual turning angle A relational deviation detecting means for determining whether or not a deviation has occurred, and the spring reaction force used when the steering reaction force control means calculates the target steering reaction force torque when the relational deviation is detected. The spring reaction force component reducing means for reducing the torque component, and the other reaction used when the steering reaction force control means calculates the target steering reaction force torque when the relationship deviation is detected. In that a further reaction force increasing means for increasing the magnitude of the torque component.

In the present invention, the steering reaction force control means calculates the target steering reaction force torque by adding together the spring reaction force torque component, which is a force for returning the steering handle to the neutral position, and the other reaction force torque component. The driving of the reaction force actuator is controlled so that the steering reaction force torque is applied to the steering of the steering wheel. On the other hand, the turning control means calculates a target turning angle corresponding to the steering angle detected by the steering angle detection means according to the correspondence stored in the correspondence storage means, and is detected by the turning angle detection means. The driving of the turning actuator is controlled so that the turning angle to become the target turning angle. In such a steering-by-wire type steering device, for example, when the turning angle detection unit fails, the correspondence relationship between the detected steering angle and the actual turning angle is stored in the correspondence storage unit. May deviate from the relationship. In this case, the restoring force (spring reaction force torque component) to the neutral position of the steering wheel does not work properly.

Therefore, in the present invention, whether or not there is a deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle is determined by the relation deviation detection means. That is, it is determined whether or not the actual correspondence relationship is deviated from the original correspondence relationship stored in the correspondence relationship storage means. When a deviation is detected in the correspondence relationship, the spring reaction force component reducing means reduces the magnitude of the spring reaction force torque component used when calculating the target steering reaction force torque. Therefore, even when the turning angle detecting means is out of order, an inappropriate reaction force torque component does not act on the steering wheel, and the uncomfortable feeling in the steering operation can be reduced. In addition, since the magnitude of the spring reaction force torque component is reduced in calculation, it is not necessary to add a mechanical configuration and can be easily implemented. Further, the other reaction force component increasing means increases the magnitude of another reaction force torque component (a reaction force torque component different from the spring reaction force torque component). Accordingly, a decrease in the spring reaction force torque component can be compensated for by an increase in the other reaction force torque component, and a sudden change in the target steering reaction force torque can be suppressed.
Note that “decreasing the spring reaction force torque component” includes making the spring reaction force torque component zero.
As the other reaction force torque component, a reaction force torque component that is not related to the magnitude of the steering angle is preferable. For example, a friction reaction force torque component that simulates the frictional resistance of the steering mechanism, and with the turning operation of the steering wheel Examples include a viscous reaction force torque component that simulates the generated viscous resistance. Then, the other reaction force component increasing means may increase at least one of them.

  Another feature of the present invention includes an abnormality detection means for determining whether or not an abnormality has occurred in the turning angle detection means, and the relationship deviation detection means has an abnormality detected in the turning angle detection means. In this case, it is determined whether or not there is a deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle.

  For example, when a relative angle sensor that detects a relative angle with respect to a reference position is used as the turning angle detection means, when the reference position deviates from the correct position, the actual steering angle detected by the steering angle detection means Deviation occurs in the correspondence with the steering angle. Therefore, in the present invention, it is determined whether or not an abnormality has occurred in the turning angle detecting means by the abnormality detecting means, and when the abnormality is detected in the turning angle detecting means, the related deviation detecting means is operated. . Accordingly, it is possible to operate the relationship deviation detection means at an appropriate timing.

  Another feature of the present invention is that the yaw rate detecting means for detecting the yaw rate of the vehicle, the vehicle speed detecting means for detecting the traveling speed of the vehicle, the steering angle detected by the steering angle detecting means and the vehicle speed detecting means. And a theoretical yaw rate calculating means for calculating a theoretical yaw rate of the vehicle using at least the vehicle speed as a parameter, and the relationship deviation detecting means is based on a comparison between the detected yaw rate detected and the theoretical yaw rate. The purpose is to determine whether or not there is a deviation in the correspondence between the steering angle detected by the detection means and the actual turning angle.

  In the present invention, the theoretical yaw rate is calculated from the steering angle and the vehicle speed by the theoretical yaw rate calculating means, while the actual yaw rate of the vehicle is detected by the yaw rate detecting means. When there is no deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle, the deviation between the theoretical yaw rate and the detected yaw rate should be small. Therefore, the relationship deviation detection means determines whether or not there is a deviation in the correspondence between the steering angle and the turning angle based on the comparison between the theoretical yaw rate and the detected yaw rate. For example, a deviation between the theoretical yaw rate and the detected yaw rate is calculated, and when the absolute value of this deviation is larger than a predetermined value, it is determined that a relationship deviation has occurred. Accordingly, it is possible to easily detect a shift in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle.

  Another feature of the present invention is that the relationship deviation detecting means is based on the relationship between the magnitude of the drive current that flows to drive the reaction force actuator and the magnitude of the drive current that flows to drive the steering actuator. The purpose is to determine whether or not there is a deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle.

For example, when the steered wheels are traveling in the straight direction, the drive current of the steered actuator is a very small value including zero. At this time, if there is no deviation in the correspondence relationship between the steering angle detected by the steering angle detection means and the actual turning angle, the steering angle is also in the neutral position or a position very close to it, so the reaction force The magnitude of the actuator drive current should also be a small value including zero. Therefore, in the present invention, the relationship between the steering angle detected by the steering angle detecting means and the actual turning angle is deviated from the relationship between the magnitude of the driving force of the reaction force actuator and the magnitude of the driving current of the steering actuator. It is determined whether or not this has occurred. Therefore, it is possible to easily detect the deviation of the correspondence relationship.
In determining the magnitude of the drive current, the magnitude of the current that actually flows through each actuator may be detected, as well as the magnitude of the target current value that flows through each actuator.

  Another feature of the present invention includes vehicle speed detection means for detecting the traveling speed of the vehicle, wherein the relationship deviation detection means is configured such that the vehicle speed detected by the vehicle speed detection means is greater than a reference speed, and the steering actuator is Detected by the steering angle detection means when the magnitude of the drive current passed for driving is smaller than the reference current value and the magnitude of the drive current passed for driving the reaction force actuator is greater than the reference current value In other words, it is determined that there is a deviation in the correspondence between the steering angle and the actual steering angle.

In this invention, when the vehicle speed is larger than the reference speed and the magnitude of the drive current for driving the steering actuator is smaller than the reference current value, that is, when the vehicle is traveling in a substantially straight direction, steering is performed. It is determined whether or not there is a deviation in the correspondence between the steering angle detected by the angle detection means and the actual turning angle. In this case, if normal, the magnitude of the drive current flowing through the reaction force actuator should be a small value. Therefore, when the magnitude of the drive current flowing through the reaction force actuator is larger than the reference current value, it can be determined that the correspondence relationship has shifted. Therefore, in the present invention, it is determined whether or not there is a shift in the correspondence relationship based on the magnitude of the drive current that flows through the reaction force actuator. As a result, it is possible to easily detect the correspondence shift.
Note that the reference current value for comparing the magnitude of the drive current of the steering actuator and the reference current value for comparing the magnitude of the drive current value of the reaction force actuator are set separately and are limited to the same value. is not.

  Hereinafter, a vehicle steering apparatus according to two embodiments of the present invention will be described with reference to the drawings. First, the vehicle steering apparatus according to the first embodiment will be described. FIG. 1 schematically shows a system configuration of a vehicle steering apparatus according to the first embodiment.

  This vehicle steering device mechanically includes a steering operation device 10 that is steered by a driver, and a steering device 20 that steers left and right front wheels FW1 and FW2 as steered wheels according to the steering operation of the driver. A separate steer-by-wire system is adopted. The steering operation device 10 includes a steering handle 11 as an operation unit that is rotated by a driver. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force electric motor 13 for generating a reaction force incorporating a speed reduction mechanism is assembled to the lower end of the steering input shaft 12. The steering reaction force electric motor 13 applies a reaction force to the steering operation of the steering handle 11, and corresponds to a reaction force actuator of the present invention.

  The steered device 20 includes a steered shaft 21 that extends in the left-right direction of the vehicle. The left and right front wheels FW1, FW2 are connected to both ends of the steered shaft 21 via tie rods 22a, 22b and knuckle arms 23a, 23b so as to be steerable. The left and right front wheels FW1 and FW2 are steered left and right by the displacement of the steered shaft 21 in the axial direction. On the outer periphery of the turning shaft 21, a turning electric motor 24 assembled in a housing (not shown) is provided. The rotation of the electric motor 24 for turning is decelerated by the screw feed mechanism 26 and converted into displacement in the axial direction of the turning shaft 21. This steering electric motor 24 corresponds to the steering actuator of the present invention.

  Next, the electric control device 30 that controls the rotation of the steering reaction force electric motor 13 and the steering electric motor 24 will be described. The electric control device 30 includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a yaw rate sensor 34. The steering angle sensor 31 is assembled to the steering input shaft 12, detects a rotation angle from the reference point of the steering handle 11, and outputs a signal representing the steering angle θ. Hereinafter, the steering angle θ detected by the steering angle sensor 31 is referred to as an actual steering angle θ. With respect to the actual steering angle θ, the reference point is the neutral position “0”, the left angle is represented by a positive value, and the right angle is represented by a negative value.

  The turning angle sensor 32 detects the amount of axial displacement from the reference point of the turning shaft 21 and outputs a signal representing the turning angle δ of the left and right front wheels FW1, FW2. The steering angle sensor 32 includes a relative angle sensor that detects a rotation angle of the steering electric motor 24 with respect to the reference position of the rotor, and an absolute angle sensor that provides the reference position. The rotation angle of the rotor of the turning electric motor 24 takes a value corresponding to the amount of movement of the turning shaft 21 in the axial direction, that is, the amount of change in the turning angle θ. Therefore, the turning angle sensor 32 detects the steering angle θ by the absolute angle sensor that detects the position of the turning shaft 21 and the relative angle sensor that detects the rotation angle from the reference position. In the present embodiment, two resolver sensors for detecting the rotation angle of the rotor of the steering electric motor 24 are provided as relative angle sensors, and an encoder is provided as an absolute angle sensor.

  The resolver sensor as a relative angle sensor is used at the time of turning control because it can detect the rotation angle of the turning electric motor 24 with high accuracy. Also, the encoder as an absolute angle sensor is not used during turning control because the resolution is coarser than that of a resolver sensor, and the detected value (when detected) when an ignition switch (not shown) is turned on (not shown). Absolute angle) is read and used to set the reference position of the resolver sensor.

  Hereinafter, the turning angle δ detected by the turning angle sensor 32 is referred to as an actual turning angle δ. The actual turning angle δ represents the displacement of the turning shaft 21 corresponding to leftward turning of the left and right front wheels FW1 and FW2 as a positive value with the reference point being the neutral position “0”, and the right and left front wheels FW1 and FW2 The displacement of the turning shaft 21 corresponding to the turning in the right direction is represented by a negative value.

  The vehicle speed sensor 33 outputs a vehicle speed signal representing the vehicle speed V that is the traveling speed of the vehicle. The yaw rate sensor 34 detects the yaw rate of the vehicle and outputs a signal corresponding to the detected yaw rate. Hereinafter, the detected yaw rate is referred to as an actual yaw rate γ. This actual yaw rate γ also represents leftward acceleration as a positive value and rightward acceleration as a negative value.

  The electric control device 30 includes a steering reaction force electronic control unit (hereinafter referred to as a steering reaction force ECU) 35 and a steering electronic control unit (hereinafter referred to as a steering ECU) 36 that are connected to each other. Yes. A steering angle sensor 31 is connected to the steering reaction force ECU 35. In addition, a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a yaw rate sensor 34 are connected to the steering ECU 36.

  The steering reaction force ECU 35 and the steering ECU 36 each have a microcomputer including a CPU, a ROM, a RAM, and the like as main components. The steering reaction force ECU 35 executes the steering reaction force control program shown in FIG. 4 stored in the ROM, and drives and controls the steering reaction force electric motor 13 via the drive circuit 37. The turning ECU 36 executes the turning angle control program shown in FIG. 2 stored in the ROM, and drives and controls the turning electric motor 24 via the drive circuit 38.

  The drive circuits 37 and 38 are respectively controlled by the ECUs 35 and 36 to energize the electric motors 13 and 24. In these drive circuits 37 and 38, current sensors 37a and 38a for detecting drive currents flowing through the electric motors 13 and 24, respectively, are provided, and the drive current value signals detected by the current sensors 37a and 38a are as follows. The ECUs 35 and 36 are supplied.

  Next, steering angle control performed by the steering ECU 36 will be described. FIG. 2 shows a turning angle control program stored in the ROM of the turning ECU 36. The turning ECU 36 performs an initial diagnosis process by turning on an ignition switch (not shown), and then starts a turning angle control routine represented by this program. This turning angle control routine is repeated at a predetermined short cycle.

  When this control routine is activated, the steering ECU 36 reads the actual steering angle θ and the actual steering angle δ detected by the steering angle sensor 31 and the steering angle sensor 32 in step S11. Subsequently, in step S12, a target turning angle δ * corresponding to the actual steering angle θ is calculated with reference to a target turning angle table stored in advance in the ROM. This target turning angle table sets the correspondence between the steering angle θ of the steering handle 11 and the target turning angle δ *. As shown in FIG. 3, the target turning angle table increases as the steering angle θ increases. The angle δ * is stored. The ROM of the steering ECU 36 that stores this target turning angle table corresponds to the correspondence storage means of the present invention.

  In step S12, the actual steering angle θ is substituted into the steering angle θ of the target turning angle table, and the target turning angle δ * corresponding to the actual steering angle θ is obtained. Instead of using the target turning angle table, a function in which the correspondence relationship between the steering angle θ and the target turning angle δ * is predetermined is stored in the ROM, and the actual steering is performed using the function. The target turning angle δ * corresponding to the angle θ may be calculated.

  Subsequently, the steering ECU 36 proceeds to step S13 to calculate a target drive current value proportional to a difference value (δ * −δ) obtained by subtracting the actual turning angle δ from the target turning angle δ *. By outputting a control signal (for example, PWM control signal) corresponding to the target drive current value to the drive circuit 38, the target drive current is caused to flow to the steering electric motor 24. This energization control is performed, for example, by feeding back the drive current detected by the current sensor 38a. Thereby, the steering electric motor 24 is driven and controlled so that the difference value (δ * −δ) becomes “0”, and the turning shaft 21 is moved in the axial direction via the screw feed mechanism 26 by the rotation. To drive. The left and right front wheels FW1 and FW2 are steered to the target turning angle δ * by the displacement of the turning shaft 21 in the axial direction. As a result, the left and right front wheels FW1, FW2 are steered according to the turning operation of the steering handle 11, and the vehicle is turned left and right. Thus, the steered ECU 36 once ends the steered angle control routine when the process of step S13 is executed. Then, the turning angle control routine is repeated at a predetermined short cycle.

  Next, steering reaction force control performed by the steering reaction force ECU 35 will be described. FIG. 4 shows a steering reaction force control program stored in the ROM of the steering reaction force ECU 35. The steering reaction force ECU 35 performs an initial diagnosis process by turning on an ignition switch (not shown), and then starts a steering reaction force control routine represented by this program. This steering reaction force control routine is repeated at a predetermined short cycle.

  When this control routine is started, first, in step S21, the actual steering angle θ detected by the steering angle sensor 31 is read. Next, in step S22, it is determined whether or not a neutral position shift has occurred. The neutral position deviation detection determined in step S22 is performed by reading the detection result of the neutral position deviation detection control routine (see FIG. 8) executed by the steering ECU 36 in parallel with the present control routine. The neutral position deviation detection control routine will be described later.

  If “NO” in the determination in step S22, that is, if no neutral position deviation is detected, the process proceeds to step S23, and the spring reaction force torque component Ta is calculated. This spring reaction force torque component Ta is a torque component that attempts to return the steering handle 11 to the neutral position among the steering reaction force torque applied to the steering handle 11, and is calculated with reference to the spring reaction force torque table. As shown in FIG. 5, the spring reaction force torque table stores the correspondence between the steering angle θ of the steering handle 11 and the spring reaction force torque component Ta in the ROM of the steering ECU 36. As can be seen from this table, the spring reaction force torque component Ta is set to increase as the steering angle θ increases.

  In step S23, the actual steering angle θ detected by the steering angle sensor 31 is substituted into the steering angle θ of the spring reaction force torque table, and the target spring reaction force torque component Ta corresponding to the actual steering angle θ is obtained. Instead of using the spring reaction force torque table, a function that defines the correspondence between the steering angle θ and the spring reaction force torque component Ta is stored in the ROM, and the steering angle θ is calculated using the function. The corresponding target spring reaction force torque component Ta may be calculated.

  Subsequently, the steering reaction force ECU 35 calculates a friction reaction force torque component Tb in step S24. The friction reaction force torque component Tb is a torque component that simulates the frictional resistance of the steering mechanism among the steering reaction force torque applied to the steering handle 11. Since the friction reaction force torque component Tb depends on the steering angular velocity ω (= dθ / dt) obtained by differentiating the steering angle θ with time and is calculated with hysteresis characteristics, the steering angular velocity ω and the friction reaction force are calculated. Calculation is performed using the friction reaction force torque table shown in FIG. 6 in which the correspondence relationship with the torque component Tb is stored. This friction reaction force torque table is stored in the ROM of the steering reaction force ECU 35.

  The steering angular velocity ω is obtained by calculating the amount of change per unit time of the actual steering angle θ detected by the steering angle sensor 31 because this control routine is repeatedly executed at a predetermined short period. In step S24, the calculated actual steering angular velocity ω is substituted into the steering angular velocity ω of the friction reaction force torque table, and a target friction reaction force torque component Tb corresponding to the actual steering angular velocity ω is obtained. Instead of using the friction reaction force torque table, a function that defines the correspondence between the steering angular velocity ω and the friction reaction force torque component Tb is stored in the ROM, and the steering angular velocity ω is calculated using the function. The corresponding target friction reaction force torque component Tb may be calculated.

  Subsequently, the steering reaction force ECU 35 calculates a viscous reaction force torque component Tc in step S25. The viscous reaction force torque component Tc is a torque component that simulates the viscous resistance generated in accordance with the turning operation of the steering handle 11 out of the steering reaction force torque applied to the steering handle 11. Since the viscous reaction force torque component Tc is calculated in proportion to the steering angular acceleration dω / dt obtained by differentiating the steering angular velocity ω with respect to time, the correspondence relationship between the steering angular acceleration dω / dt and the viscous reaction force torque component Tc is stored. It is calculated using the viscous reaction force torque table shown in FIG. This viscous reaction force torque table is also stored in the ROM of the steering reaction force ECU 35.

  In step S25, the actual steering angular acceleration dω / dt obtained by calculating the change amount per unit time of the actual steering angular velocity ω is substituted into the steering angular acceleration dω / dt of the viscous reaction force torque table, and the actual steering angle is calculated. A target viscous reaction force torque component Tc corresponding to the acceleration dω / dt is obtained. Instead of using the viscous reaction force torque table, a function that defines the correspondence between the steering angular acceleration dω / dt and the viscous reaction force torque component Tc is stored in the ROM, and steering is performed using the function. The target viscous reaction force torque component Tc corresponding to the angular acceleration dω / dt may be calculated.

  Next, the steering reaction force ECU 35 calculates a target steering reaction force torque T * in step S26. The target steering reaction torque T * is obtained by adding the spring reaction force torque component Ta, the friction reaction force torque component Tb, and the viscous reaction force torque component Tc calculated in steps S23 to S25. In the present embodiment, the target steering reaction torque T * is calculated from the three torque components Ta, Tb, and Tc, but other torque components may be added. For example, a self-alignment torque component that simulates the self-alignment torque input to the steering handle 11 due to friction between the left and right front wheels FW1, FW2 and the road surface may be added. In this case, the self-alignment torque component can be set to be proportional to the actual yaw rate γ detected by the yaw rate sensor 34.

  When the target steering reaction force torque T * is thus calculated, the steering reaction force ECU 35 outputs a control signal (for example, a PWM control signal) corresponding to the target steering reaction force torque T * to the drive circuit 37 in step S27. As a result, a drive current corresponding to the target steering reaction torque T * is caused to flow to the steering reaction force electric motor 13. This energization control is performed, for example, by feeding back the drive current detected by the current sensor 37a. And this steering reaction force control routine is once complete | finished.

  Since this steering reaction force control routine is repeated at a predetermined short cycle, a steering reaction force equal to the sequentially calculated target steering reaction force torque T * is applied to the steering handle 11 via the steering input shaft 12. Thereby, an appropriate reaction torque is applied to the turning operation of the steering handle 11 by the driver, and the driver can comfortably rotate the steering handle 11 while feeling the steering reaction force.

  Incidentally, when the correspondence between the actual steering angle θ detected by the steering angle sensor 31 and the actual turning angle of the left and right front wheels FW1, FW2 is deviated, the restoring force (spring) to the neutral position of the steering handle 11 The reaction torque component Ta) does not work properly. That is, torque is generated in a direction in which the steering handle 11 is shifted from the straight traveling direction by an amount corresponding to the shift of the neutral position. For example, even when the left and right front wheels FW1 and FW2 are directed in the straight direction, if the actual steering angle θ detected by the steering angle sensor 31 takes a value that deviates from the neutral position, the spring reaction force corresponding to the deviation is obtained. Torque works and the steering wheel operation is taken. For this reason, the driver feels uncomfortable.

  Therefore, when the neutral position deviation is detected in step S22, the following two processes (S28, S29) are added. In step S28, the correction coefficient K1 (<1) is set so that the magnitude (absolute value) of the spring reaction force torque component Ta is smaller than that at the normal time (when the neutral position deviation is not detected). . In the present embodiment, the correction coefficient K1 is set to zero (K1 = 0) so that the spring reaction force torque component Ta becomes zero.

  The correction coefficient K1 is multiplied when calculating the spring reaction force torque component Ta in step S23. That is, the final target spring reaction force torque component Ta is calculated by multiplying the spring reaction force torque component Ta obtained with reference to the spring reaction force torque table by the correction coefficient K1. Therefore, in this case, the spring reaction force torque component Ta is cut. The correction coefficient K1 may be set so that the spring reaction force torque component Ta does not become zero and becomes smaller than normal (0 <K1 <1).

  In the next step S29, the correction coefficient K2 (> 1) is set so that the magnitudes (absolute values) of the friction reaction force torque component Tb and the viscous reaction force torque component Tc are larger than in the normal case. This correction coefficient K2 is multiplied when calculating the friction reaction force torque component Tb and the viscous reaction force torque component Tc in steps S24 and S25. That is, the final target friction reaction force torque component Tb is obtained by multiplying the friction reaction force torque component Tb and the viscosity reaction force torque component Tc obtained by referring to the friction reaction force torque table and the viscosity reaction force torque table by the correction coefficient K2. The target viscosity reaction force torque component Tc is calculated. Therefore, the friction reaction force torque component Tb and the viscous reaction force torque component Tc are larger than in the normal case.

  In this case, the friction reaction force torque component Tb and the viscous reaction force torque component Tc may be multiplied by different correction coefficients, or only one of the torque components may be multiplied by the correction coefficient. Also good. Further, the correction coefficient may be varied corresponding to the magnitude obtained by subtracting the spring reaction force torque component Ta. For example, an adjustment unit may be provided that adjusts so as to increase other torque components as the reduction amount of the spring reaction force torque component Ta increases.

  Thus, when the correction coefficients K1 and K2 for each torque component are set in steps S28 and S29, the torque component calculation processing from step S23 described above is performed. Therefore, when the neutral position of the actual steering angle θ and the neutral position of the left and right front wheels FW1 and FW2 are deviated, the spring reaction torque component set according to the steering angle θ is cut, and therefore the steering handle 11 The restoring force to the neutral position is lost, and the steering reaction force torque does not work in the direction of shifting with respect to the straight traveling of the vehicle. In addition, since the spring reaction force torque component is cut, the friction reaction force torque component Tb and the viscous reaction force torque component Tc are increased, and therefore the magnitude of the target steering reaction torque T * obtained by adding them is abruptly changed. do not do. As a result, the uncomfortable feeling for the driver can be reduced.

  Next, neutral position shift detection control performed by the steering ECU 36 will be described. FIG. 8 shows a neutral position deviation detection control program stored in the ROM of the steering ECU 36. The steering ECU 36 performs an initial diagnosis process by turning on an ignition switch (not shown), and then starts a neutral position deviation detection control routine represented by this program. This neutral position deviation detection control routine is repeated at a predetermined short cycle. The steering ECU 36 executes this neutral position deviation detection control routine in parallel with the above-described steering angle control routine.

  When this control routine is activated, the steering ECU 36 first determines whether or not an abnormality has occurred in the steering angle sensor 32 in step S31. When the turning angle sensor 32 is out of order, the correspondence relationship between the actual steering angle θ and the actual turning angles of the left and right front wheels FW1, FW2 may be shifted. Therefore, in this control routine, first, it is determined whether or not the turning angle sensor 32 is abnormal. Here, the presence / absence of abnormality of the two relative angle sensors and the absolute angle sensor constituting the turning angle sensor 32 is determined.

  For example, it is determined that there is an abnormality when the voltage value or waveform of the output signal of each sensor is out of the normal range due to disconnection or short circuit, or when the outputs of the two relative angle sensors are different. Also, it is determined that there is an abnormality when the absolute angle cannot be read at the initial diagnosis performed when the ignition switch is turned on. Then, the steering ECU 36 determines “NO” and terminates this control routine once when no abnormality is detected in all the three sensors constituting the steering angle sensor 32. On the other hand, if any one of the three sensors is abnormal, “YES” is determined, and the process proceeds to step S32.

  If the turning ECU 36 determines in step S31 that an abnormality has occurred in the turning angle sensor 32, the turning ECU 36 determines in step S32 whether the turning angle is unknown. That is, it is determined whether or not the turning angle is unknown based on the sensor in which no abnormality is detected among the three sensors. If the determination in step S32 is “NO”, that is, if the turning angle can be detected, this control routine is temporarily terminated. On the other hand, if “YES” in step S32, that is, if the turning angle is unknown, the steering ECU 36 advances the process to step S33. For example, it is determined that the turning angle is unknown even when the absolute angle cannot be read at the time of the initial diagnosis.

In step S33, the actual steering angle θ detected by the steering angle sensor 31, the vehicle speed V detected by the vehicle speed sensor 33, and the actual yaw rate γ detected by the yaw rate sensor 34 are read. Subsequently, in step S34, a theoretical yaw rate γ0 of the vehicle is calculated from the actual steering angle θ and the vehicle speed V. The theoretical yaw rate γ0 is a yaw rate value of the vehicle that is estimated in calculation when the vehicle travels at the actual steering angle θ and the vehicle speed V.
γ0 = f (θ, V)
It is calculated by the function. Alternatively, it may be calculated using a conversion table for deriving the theoretical yaw rate γ0 from the actual steering angle θ and the vehicle speed V.

  Subsequently, the steering ECU 36 determines whether or not the deviation Δγ (= | γ−γ0 |) between the actual yaw rate γ detected by the yaw rate sensor 34 and the calculated theoretical yaw rate γ0 is larger than the reference value A in step S35. Determine whether. If the deviation Δγ is larger than the reference value A (S35: YES), it is determined that a neutral position deviation has occurred, the process proceeds to step S36, and a detection signal indicating “there is a neutral position deviation” is detected. Output to the force ECU 35. This detection signal is a signal read in step S22 of the steering reaction force control routine described above. On the other hand, if the deviation Δγ is equal to or smaller than the reference value A, the present control routine is temporarily exited.

  The steering ECU 36 repeatedly executes this control routine at a predetermined short period. The deviation between the neutral position of the actual steering angle θ detected by the steering angle sensor 31 and the actual neutral position of the left and right front wheels FW1, FW2 appears as a deviation between the actual yaw rate γ and the theoretical yaw rate γ0 during vehicle travel. Therefore, in this embodiment, when the turning angle cannot be detected, the yaw rate deviation Δγ is repeatedly calculated, and when the deviation Δγ exceeds the reference value A, the neutral position is misaligned. Judge that Therefore, it is possible to easily detect the displacement of the neutral position.

  This control routine is repeated at a predetermined cycle, but once the relational deviation of the neutral position is detected and a detection signal indicating “there is a neutral position deviation” is output, the next ignition switch is turned on and activated. Until it is stopped. In this case, the detection signal indicating “neutral position deviation exists” is kept on. Therefore, in step S22 of the steering reaction force control routine, the determination of “there is a neutral position deviation” is continued, and the spring reaction force torque component Ta is cut, and the friction reaction force torque component Tb, the viscous reaction force is cut. The increase correction of the torque component Tb is continued. For example, when the neutral position is properly controlled in parallel and it is determined that the neutral position deviation has been eliminated, the output of the detection signal indicating “neutral position deviation” is stopped (turned off). The control routine may be resumed.

  According to the vehicle steering apparatus of the first embodiment described above, the spring reaction force torque component is reduced when the correspondence relationship between the actual steering angle θ and the actual turning angle of the left and right front wheels FW1, FW2 deviates ( Therefore, the steering reaction torque in a direction that prevents the vehicle from traveling straight ahead does not work. Further, since the friction reaction force torque component Tb and the viscous reaction force torque component Tc are increased simultaneously with the reduction of the spring reaction force torque component, the magnitude of the target steering reaction torque T * obtained by adding them does not change suddenly. . Therefore, the uncomfortable feeling of the steering operation due to the neutral position shift can be reduced. In addition, since the magnitude of the spring reaction force torque component Ta is reduced in calculation, it is not necessary to add a mechanical configuration and can be easily implemented.

  In addition, the determination processing for the presence or absence of the neutral position deviation can be easily performed because it is performed by calculation based on the deviation Δγ between the actual yaw rate γ and the theoretical yaw rate γ0. Moreover, since it is performed when the turning angle becomes unknown due to an abnormality of the turning angle sensor 32 and is not performed otherwise, the calculation burden for calculating the yaw rate deviation Δγ is reduced.

  Next, a vehicle steering apparatus according to a second embodiment will be described. The second embodiment is a modification of the neutral position deviation detection routine in the first embodiment, and the other configurations are the same as those in the first embodiment. Therefore, only the neutral position deviation detection routine different from the first embodiment will be described. FIG. 9 shows a neutral misalignment detection program stored in the ROM of the steering ECU 36 as the second embodiment. The steering ECU 36 performs an initial diagnosis process by turning on an ignition switch (not shown), and then starts a neutral position deviation detection control routine represented by this program. This neutral position deviation detection control routine is repeated at a predetermined short cycle.

  When this control routine is activated, the steering ECU 36 first determines in step S41 whether or not an abnormality has occurred in the turning angle sensor 32. If no abnormality is detected, the control routine is temporarily terminated. On the other hand, when it is determined in step S41 that an abnormality has occurred in the turning angle sensor 32, in the next step S42, it is determined whether or not the turning angle is unknown, and the turning angle can be detected. If so, this control routine is temporarily terminated. The determination processes in steps S41 and S42 are the same as those in steps S31 and S32 in the first embodiment.

  If “YES” in step S42, that is, if the turning angle is unknown, the steering ECU 36 advances the process to step S43. In this step S43, the vehicle speed V detected by the vehicle speed sensor 33, the current value flowing through the steering reaction force electric motor 13 detected by the current sensor 37a (hereinafter referred to as reaction force motor current i1), and current sensor A current value (hereinafter referred to as a steered motor current i2) flowing in the steered electric motor 24 detected by 38a is read. In this case, the reaction force motor current i1 may be read directly from the current sensor 37a or may be read via the steering reaction force ECU 35. Further, instead of actually using the current values detected by the current sensors 37a and 38a, the control target current value (the target drive current value to be supplied to the steering reaction force electric motor 13, the steering electric motor 24) (Target drive current value to be passed) may be used.

  Subsequently, the steering ECU 36 determines whether or not the vehicle speed V detected by the vehicle speed sensor 33 is greater than the reference vehicle speed Vref in step S44. When the vehicle speed V is less than or equal to the reference vehicle speed Vref (S44: NO), the determination routine for determining the neutral position deviation is not satisfied, and thus this control routine is temporarily terminated. In this case, if the timing of a timer described later is started, the timer value t is cleared to zero in step S50.

  If it is determined in step S44 that the vehicle speed V is greater than the reference speed Vref, then the determination process of step S45 is performed. In step S45, it is determined whether or not the magnitude (absolute value regardless of the rotation direction) of the steered motor current i2 detected by the current sensor 38a is smaller than the reference current value i2ref. When the magnitude of the turning motor current i2 is equal to or greater than the reference current value i2ref (S45: NO), the control routine is temporarily terminated because the determination condition for determining the neutral position deviation is not satisfied. Also in this case, if the timing of the timer is started, the timer value t is cleared to zero in step S50.

  In step S45, when it is determined that the magnitude of the steered motor current i2 is smaller than the reference current value i2ref, the determination process of step S46 is subsequently performed. In step S46, it is determined whether or not the magnitude of the reaction force motor current i1 detected by the current sensor 37a (absolute value regardless of the rotation direction) is larger than the reference current value i1ref. When the magnitude of the reaction force motor current i1 is equal to or smaller than the reference current value i1ref (S46: NO), the present control routine is temporarily terminated. Also in this case, if the timing of the timer is started, the timer value t is cleared to zero in step S50.

  In step S46, if it is determined that the magnitude of the reaction force motor current i1 is greater than the reference current value i1ref, there is a risk of a neutral position shift, so that the continuation state is determined by the timer. That is, in step S47, the timer value t is incremented by the value 1, and in step S48, it is determined whether or not the incremented timer value t has exceeded the reference time tref. This timer value t is cleared to zero when the control routine is started.

  In step S48, if the timer value t does not exceed the reference time tref, this control routine is once ended. This control routine is repeated at a predetermined short cycle. Before the reference time tref elapses, the vehicle speed V becomes equal to or lower than the reference vehicle speed Vref (S44: NO), and the magnitude of the steering motor current i2 becomes equal to or higher than the reference current value i2ref (S45: NO). When the magnitude of the reaction force motor current i1 becomes equal to or smaller than the reference current value i1ref (S46: NO), the timer value t is cleared to zero (S50).

  When such determination processing is repeated and the continuous time in which the three conditions of Steps S44 to S46 are satisfied exceeds the reference time tref, it is determined in Step S49 that a neutral position shift has occurred, A detection signal indicating “there is deviation” is output to the steering reaction force ECU 35. This detection signal is a signal read in step S22 of the steering reaction force control routine described above.

  When the steering ECU 36 outputs a detection signal indicating "there is a neutral position deviation" to the steering reaction force ECU 35, the steering ECU 36 maintains the output state of the detection signal and executes this control routine as in the first embodiment. finish. Therefore, after that, for example, even if the vehicle speed V falls below the reference speed Vref, the determination output of “there is a neutral position deviation” is continued. For example, when the neutral position is properly controlled in parallel and it is determined that the neutral position deviation has been eliminated, the output of the detection signal indicating “neutral position deviation” is stopped (turned off). The control routine may be resumed.

Here, the determination principle of the neutral position deviation in the second embodiment will be described.
When the left and right front wheels FW1, FW2 are traveling in the straight direction, the drive current of the steering electric motor 24 is a very small value. At this time, if there is no deviation in the correspondence between the actual steering angle θ detected by the steering angle sensor 31 and the actual turning angle of the left and right front wheels FW1, FW2, the actual steering angle θ is also set to the neutral position or Since the position is very close to that, the magnitude of the drive current of the steering reaction force electric motor 13 should also be a small value.

  Therefore, in the second embodiment, when the vehicle speed V is greater than the reference speed Vref and the magnitude of the steered motor current i2 is smaller than the reference current value i2ref, that is, when the vehicle is traveling in a substantially straight direction. In addition, the neutral position deviation is determined based on the magnitude of the reaction force motor current i1. At this time, when the magnitude of the reaction force motor current i1 is larger than the reference current value i1ref, it can be determined that there is a neutral position deviation. Therefore, the neutral position shift can be easily detected. Further, since the determination is made after confirming the continuation of the reference time tref, erroneous determination due to temporary condition matching during the steering operation is prevented, and determination accuracy is high.

  As mentioned above, although the vehicle steering apparatus of this embodiment was demonstrated, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention.

  Further, in the present embodiment, the neutral position deviation is detected by the steering ECU 36, but the detection (the neutral position deviation detection routine shown in FIGS. 8 and 9) is performed by the steering reaction force ECU 35. May be. In this case, the vehicle speed sensor 33 and the yaw rate sensor 34 are connected to the steering reaction force ECU 35 and their detection signals are input.

  In the present embodiment, the friction reaction force torque component Tb and the viscous reaction force torque component Tc are used as reaction force torque components other than the spring reaction force torque component Ta, but only one of the reaction force torque components is used. Or another reaction torque component such as a self-alignment torque component may be used.

1 is an overall system configuration diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is a flowchart of a turning angle control program executed by the turning ECU according to the first embodiment. It is a graph showing the target turning angle table which concerns on 1st Embodiment. It is a flowchart of the steering reaction force control program executed by the steering reaction force ECU according to the first embodiment. It is a graph showing the spring reaction force torque table which concerns on 1st Embodiment. It is a graph showing the friction reaction force torque table which concerns on 1st Embodiment. It is a graph showing the viscous reaction force torque table which concerns on 1st Embodiment. It is a flowchart of the neutral position shift detection program performed by ECU for steering which concerns on 1st Embodiment. It is a flowchart of the neutral position shift detection program performed by ECU for steering which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Steering operation apparatus, 11 ... Steering handle, 12 ... Steering input shaft, 13 ... Electric motor for steering reaction force, 20 ... Steering device, 21 ... Steering shaft, 24 ... Electric motor for steering, 30 ... Electric control Device 31 ... steering angle sensor 32 ... steering angle sensor 33 ... vehicle speed sensor 34 ... yaw rate sensor 37a, 38a ... current sensor 35 ... steering reaction force ECU 36 ... steering ECU FW1, FW2 ... left and right front wheels, T * ... target steering reaction torque, Ta ... spring reaction force torque component, Tb ... friction reaction force torque component, Tc ... viscous reaction force torque component, V ... vehicle speed, γ ... actual yaw rate, γ0 ... theoretical yaw rate , Δ ... actual steering angle, θ ... actual steering angle, i1 ... reaction force motor current, i2 ... steering motor current.

Claims (5)

A steering handle operated by a driver to steer the vehicle ;
A steering angle detecting means for detecting a steering angle of the steering wheel,
A turning angle detecting means for detecting a turning angle of the turning wheel;
Correspondence relationship storage means for storing the correspondence relationship between the steering angle detected by the steering angle detection means and the target turning angle;
In accordance with the stored correspondence relationship, the steered wheels are rotated so that the steered angle detected by the steered angle detecting unit becomes a target steered angle corresponding to the steering angle detected by the steered angle detecting unit. Steered wheel steering means for steering ;
A reaction force actuator for applying reaction force torque to the steering of the steering wheel;
A spring reaction force torque component set according to the steering angle detected by the steering angle detection means and serving as a force for returning the steering handle to a neutral position, and another reaction force torque component different from the spring reaction force component A steering reaction force control means for calculating a target steering reaction force torque by adding together, and controlling the drive of the reaction force actuator so that the calculated target steering reaction force torque is applied to the steering of the steering wheel; In a steering-by-wire steering device equipped with
A relation deviation detection means for judging whether or not a deviation occurs in the correspondence relationship between the steering angle detected by the steering angle detection means and the actual steering angle;
A spring reaction force component reducing means for reducing the spring reaction force torque component used when the steering reaction force control means calculates the target steering reaction force torque when the relationship deviation is detected ;
When the relationship deviation is detected, the other reaction force component increasing means for increasing the magnitude of the other reaction force torque component used when the steering reaction force control means calculates the target steering reaction torque. A steering apparatus characterized by comprising. Comprising an abnormality detection means for determining whether an abnormality has occurred in the turning angle detection means,
Whether the relationship deviation detection means has a deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual steering angle when an abnormality is detected in the steering angle detection means. The steering apparatus according to claim 1, wherein it is determined whether or not. Yaw rate detection means for detecting the yaw rate of the vehicle;
Vehicle speed detecting means for detecting the traveling speed of the vehicle;
A theoretical yaw rate calculating means for calculating a theoretical yaw rate of the vehicle using at least the parameters of the steering angle detected by the steering angle detecting means and the vehicle speed detected by the vehicle speed detecting means;
Whether the relationship deviation detection means has a deviation in the correspondence between the steering angle detected by the steering angle detection means and the actual turning angle based on a comparison between the detected yaw rate detected and the theoretical yaw rate. The steering apparatus according to claim 1, wherein it is determined whether or not. The relationship deviation detection means is detected by the steering angle detection means from the relationship between the magnitude of the drive current that flows to drive the reaction force actuator and the magnitude of the drive current that flows to drive the steering actuator. The steering apparatus according to claim 1, wherein it is determined whether or not there is a deviation in a correspondence relationship between the steering angle and the actual steering angle. Vehicle speed detecting means for detecting the traveling speed of the vehicle,
The relationship deviation detecting means is configured such that the vehicle speed detected by the vehicle speed detecting means is greater than a reference speed, the magnitude of the drive current that is supplied to drive the steering actuator is less than a reference current value, and When the magnitude of the drive current that flows to drive the force actuator is greater than the reference current value, there is a deviation in the correspondence relationship between the steering angle detected by the steering angle detection means and the actual turning angle. The steering apparatus according to claim 4 , wherein the determination is made.

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