JP2007153180A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a steering wheel from turning to the right and left near a neutral position regardless of a driver's operation, even if steering torque detected by a steering torque sensor includes an off-set amount, in a vehicular steering device of a steer-by-wire type. <P>SOLUTION: A target reaction torque computing portion B11 calculates a target reaction torque T* on the basis of a steering wheel steering angle θ. A P1 control computing portion B16 calculates a motor torque command value by PI control computing, by using difference T*-T between the target torque T* and steering torque T in a computing portion 15, thereby feed-back controlling a reaction torque electric motor adding steering reaction force. When the absolute value of the steering wheel steering angle θ is within a range of a predetermined minute value, a neutral torque correction value computing portion B12 and a gain controlling portion B13 calculate a neutral torque correction value changing in proportion to the steering wheel steering angle θ and add to a side increasing a feed-back amount. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steer-by-wire vehicle steering apparatus in which a steering handle and steered wheels are mechanically separated.

  Conventionally, a steer-by-wire vehicle steering apparatus in which a steering wheel and a steered wheel are mechanically separated is well known. In this steer-by-wire vehicle steering device, the reaction force torque electric motor connected to the steering handle via the steering shaft is driven and controlled in accordance with the steering operation of the steering handle. On the other hand, reaction torque is applied. Further, the steering wheel is steered in response to the steering operation of the steering handle by drivingly controlling a steering electric motor for steering the steered wheel according to the steering operation of the steering handle.

In the control of the reaction force torque in the steer-by-wire vehicle steering apparatus, the target reaction force torque calculation unit 1 calculates the target reaction force torque T * based on the steering angle θ as shown in FIG. Then, the motor torque command value calculation unit including the calculator 2 and the PI control calculation unit 3 uses the calculated target reaction force torque T * as a control input and feedback inputs the steering torque T acting on the steering shaft. And Then, the motor torque command value calculation unit calculates a motor torque command value Tmc for applying the target reaction torque T * to the steering shaft according to the difference T * -T between the two inputs. The reaction torque electric motor is driven and controlled in accordance with the motor torque command value Tmc. In this case, the PI control calculation unit 3 normally calculates the sum of the proportional term Gp · (T * −T) and the integral term Gi · ∫ (T * −T) dt as the motor torque command value Tmc {= Gp・ (T * -T) + Gi∫ (T * -T) dt}. Gp and Gi are the gains of the proportional term and the integral term, respectively (see Patent Document 1 below).
JP 2004-34923 A

  However, when the steering handle is in the vicinity of the neutral position, an offset amount may be included in the steering torque T detected by the steering torque sensor. Because of this offset amount, in the state where the steering wheel is in the neutral position and the driver is not operating the steering wheel, for example, when the hand is released from the steering wheel, the integral term Gi · ∫ (T * − Due to the control by T) dt, the steering handle may rotate left and right. Next, this phenomenon will be described in detail. Before that, the relationship between the steering angle θ, the steering torque T, and the positive / negative of the motor torque command value Tmc and the rotation direction of the steering wheel will be described. In this case, the steering angle θ represents positive steering of the steering wheel in the positive direction, and represents leftward steering in the negative direction. The steering torque T is a positive torque acting on the steering shaft when the steering wheel is steered in the right direction, and a negative torque acting on the steering shaft when the steering handle is steered in the left direction. The motor torque command value Tmc is a reaction force that counteracts the left steering of the steering handle, with the rotational direction of the reaction torque torque electric motor generating a reaction torque that opposes the steering of the steering handle in the right direction being positive. The direction of rotation of the reaction force torque electric motor that generates torque is negative.

  Now, even if the steering torque T acting on the steering shaft is actually “0”, the steering torque T detected by the steering torque sensor has a small negative offset amount of an absolute value. Shall. In this case, even if the steering angle θ is “0”, that is, the steering wheel is in the neutral position and the target reaction torque T * is “0” as shown by the broken line in FIG. 10, the motor torque command value Tmc Becomes a negative value having a very small absolute value (point Po in FIG. 10A) at first by feedback control of the steering torque T. In this case, in the feedback control for the reaction force torque electric motor, if there is no integral term, the motor torque command value Tmc is kept at a very small absolute value.

  However, the motor torque command value Tmc at the neutral position gradually increases with the lapse of time by the integral calculation using the integral term Gi · ∫ (T * −T) dt (see FIG. 11). In this case, since the minute offset amount in FIG. 10 is a minute negative value of the absolute value as indicated by the point Po in FIG. 10A, the absolute value of the motor torque command value Tmc slightly increases with time. It becomes a large negative value (see point P1). The motor torque command value Tmc, which is a slightly larger negative value than the absolute value, attempts to rotate the reaction force torque electric motor in the direction in which the steering handle is rotated in the right direction. Now, since the steering handle is not operated by the driver, the steering handle is rotated rightward by being driven by the electric motor for reaction force. In this case, the steering handle does not continue to rotate in the right direction due to the reaction force from the road surface via the steered wheels, and the steering handle has a small rotation angle position from the neutral position to the right (point P2 in FIG. 10B). Stop).

  Although the rotation of the steering handle to the right is a minute angle, it is equivalent to steering the steering handle to the right steering angle θ1, and the target reaction torque T * corresponding to the steering angle θ1. Is calculated as a positive value (see the broken line in FIG. 10C). Since this positive target reaction torque T * generates a reaction torque when the steering handle is steered in the right direction, the motor torque command value Tmc is a positive value that is somewhat large. In this state, since the steering wheel is not operated, the steering torque T is reduced as compared with the case where the steering wheel is operated, and the motor torque command value Tmc is indicated by a point P3 in FIG. Thus, the value is slightly larger than the value corresponding to the point P2. With the motor torque command value Tmc corresponding to this point P3, the reaction torque electric motor rotates the steering handle in the left direction. Thereafter, as shown by points P4, P5, P6,..., The steering handle rotates alternately left and right regardless of the driver's operation.

  The present invention has been made to address the above-described problems, and an object of the present invention is to provide a steer-by-wire system that applies a reaction torque to a steering operation of a steering wheel by a feedback control calculation of a steering torque including an integral term. In a vehicle steering apparatus, even if an offset amount is included in the steering torque detected by the steering torque sensor, the steering handle is prevented from rotating left and right regardless of the operation of the driver.

  In order to achieve the above object, a feature of the present invention is that a steering wheel rotated by a driver and a steering torque connected to a steering shaft connected to the steering handle to react to the steering operation of the steering handle. The reaction force torque electric motor for applying the steering wheel, the steering electric motor for turning the steered wheels, and the reaction force torque electric motor according to the steering operation of the steering handle are driven and controlled. The reaction force torque application control means for controlling the application of reaction force torque to the steering operation of the vehicle, and the steering for controlling the turning of the steered wheels by driving the steering motor according to the steering operation of the steering handle In a steer-by-wire vehicle steering apparatus including a control means, a reaction force torque application control means is assembled to a steering angle sensor for detecting a steering angle of a steering wheel and a steering shaft. A steering torque sensor for detecting a steering torque acting on the steering shaft, a target reaction force torque calculating unit for calculating a target reaction force torque based on the steering angle detected by the steering angle sensor, and a calculated target A motor torque command value for applying the reaction force torque as a control input and using the detected steering torque as a feedback input so that the target reaction force torque calculated according to the difference between the two inputs is applied to the steering shaft. A motor torque command value calculation unit that calculates a motor torque command value by a calculation including at least the integral term of the difference, and steering when the detected steering angle is input and the steering handle is in the vicinity of the neutral position The steering torque offset detected by the torque sensor is canceled by the input steering angle. There to be constructed in accordance with the cancellation means.

  In this case, for example, when the absolute value of the detected steering angle is within a predetermined minute value range, the canceling means calculates a neutral torque correction value that changes in proportion to the detected steering angle. The value calculation unit and a feedback amount correction unit that adds the calculated neutral torque correction value to the side where the feedback amount increases in the calculation of the motor torque command value calculation unit may be configured.

  In the present invention configured as described above, the canceling means inputs the detected steering angle, and calculates the steering torque offset amount detected by the steering torque sensor when the steering handle is in the vicinity of the neutral position. Cancel by the steering angle detected by the angle sensor. Therefore, even if the steering wheel is in the vicinity of the neutral position and the driver is not operating the steering wheel as in the above-described prior art, the steering wheel rotates to the left or right due to the offset amount of the steering torque. Is avoided.

  Another feature of the present invention is that the neutral torque correction value calculation unit further gradually decreases the absolute value of the neutral torque correction value as the detected absolute value of the steering angle moves away from a predetermined minute value range. It is in doing so. According to this, since it is possible to smoothly shift from the cancel control of the steering torque offset amount according to the steering angle to the feedback control according to the normal steering torque, the driver may feel uncomfortable with the operation of the steering wheel. Disappear.

  A vehicle steering apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a steering apparatus for a vehicle according to the 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. The steer-by-wire method is used. 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 shaft 12, and the output shaft of the reaction force torque electric motor 14 is connected to the lower end of the steering shaft 12 via the speed reduction mechanism 13. The electric motor 14 for reaction force torque gives reaction force torque to the steering operation of the steering handle 11 by the driver, and its rotational force is transmitted to the steering shaft 12 via the speed reduction mechanism 13. ing.

  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. The steered shaft 21 is assembled with a steerable electric motor 24 and a ball screw mechanism 25 constituting a speed reduction mechanism. The steered electric motor 24 steers the left and right front wheels FW1 and FW2. The rotation of the steered motor 24 is reduced by the ball screw mechanism 25 and converted into a linear motion and transmitted to the steered shaft 21.

  Next, the electric control device 30 that controls the rotation of the reaction torque electric motor 14 and the turning electric motor 24 will be described. The electric control device 30 includes a steering angle sensor 31, a steering torque sensor 32, a turning angle sensor 33, and a vehicle speed sensor 34. The steering angle sensor 31 is assembled to the steering shaft 12, detects the rotation angle of the steering handle 11 from the reference position, and outputs it as the steering angle θ. As the steering angle sensor 31, a rotation angle sensor provided in the reaction torque electric motor 14 may be used. In this case, with respect to the steering wheel steering angle θ, the reference position is “0”, the right rotation angle of the steering wheel 11 is represented by a positive value, and the left rotation angle is represented by a negative value. The steering torque sensor 32 is assembled to the steering shaft 12, detects torque acting on the steering shaft 12, and outputs it as steering torque T. The steering torque T represents positive torque acting on the steering shaft 12 when the steering handle 11 is steered in the right direction, and negative torque acting on the steering shaft 12 when the steering handle 11 is steered in the left direction. Represented by

  The turning angle sensor 33 is assembled to the turning shaft 21, detects the amount of axial displacement from the reference position of the turning shaft 21, and outputs it as the turning angle δ of the left and right front wheels FW1, FW2. As the turning angle sensor 33, a rotation angle sensor provided in the turning electric motor 24 may be used. In this case, the turning angle δ has a reference position of “0”, the right turning angle of the left and right front wheels FW1, FW2 is represented by a positive value, and the left turning angle of the left and right front wheels FW1, FW2 is negative. Represented by the value of. The vehicle speed sensor 34 detects and outputs the vehicle speed V. The steering angle sensor 31, the steering torque sensor 32, the turning angle sensor 33, and the vehicle speed sensor 34 are connected to an electronic control unit (hereinafter referred to as ECU) 35.

  The ECU 35 includes a microcomputer including a CPU, ROM, RAM, and the like as main components, calculates a motor torque command value Tmc and a motor rotation angle command value δmc by executing a program, and corresponds to the calculated command values Tmc and δmc. The control signal is output to the drive circuits 36 and 37. The drive circuit 36 drives and controls the reaction force torque electric motor 14 in accordance with a control signal corresponding to the motor torque command value Tmc. The drive circuit 37 drives and controls the steering electric motor 24 in accordance with a control signal corresponding to the motor rotation angle command value δmc.

  Next, the operation of the embodiment configured as described above will be described with reference to the functional block diagram of FIG. This functional block diagram is a block diagram showing the functions of the ECU 35 realized by executing the program. The ECU 35 includes a torque control unit B10 for controlling the reaction force torque electric motor 14 and a steering control unit B20 for controlling the steering electric motor 24.

  The torque controller B10 includes a target reaction force torque calculator B11, a neutral torque correction value calculator B12, a neutral torque correction value gain controller B13, calculators B14 and B15, and a PI control calculator B16. The target reaction force torque calculation unit B11 calculates a target reaction force torque T * corresponding to the steering angle θ by referring to a target reaction force torque table prepared in advance in the ECU 35. As shown in FIG. 3, the target reaction force table stores a target reaction force torque T * that increases as the steering wheel steering angle θ increases. The target reaction torque calculation unit B11 defines a function indicating the relationship between the steering angle θ and the target reaction torque T * in advance instead of the target reaction force table, and uses the function to handle the steering wheel. The target reaction torque T * corresponding to the steering angle θ may be calculated.

  The neutral torque correction value calculation unit B12 refers to a neutral torque correction value table prepared in advance in the ECU 35 and calculates a neutral torque correction value Ta corresponding to the steering angle θ. As shown in FIG. 4, the neutral torque correction value table is a neutral torque correction value Ta that increases proportionally as the steering wheel steering angle θ increases within a small range of the absolute value of the steering wheel steering angle θ and becomes a constant value outside the above range. Is remembered. The steering wheel steering angle θ defined by the neutral torque correction value table is a minute angle near the neutral position of the steering wheel 11, and Δθ indicates the boundary of the correction region of the steering torque T. The neutral torque correction value calculation unit B12 defines in advance a function indicating the relationship between the steering angle θ of the steering wheel and the neutral torque correction value Ta instead of the neutral torque correction value table, and uses the function to handle the steering wheel. A neutral torque correction value Ta corresponding to the steering angle θ may be calculated.

  The neutral torque correction value gain control unit B13 receives the neutral torque correction value Ta calculated by the neutral torque correction value calculation unit B12, multiplies the input neutral torque correction value Ta by the gain G, and outputs the result to the calculator B14. . The gain G is calculated using the steering wheel steering angle θ by referring to a gain table prepared in advance in the ECU 35. As shown in FIG. 5, the gain table is maintained at “1.0” within the range of the small angle Δθ, and when the range of the small angle Δθ is exceeded, the absolute value | θ | of the steering wheel steering angle θ increases. As a result, a gain G that gradually decreases to “0.0” is stored. The neutral torque correction value gain control unit B13 defines in advance a function indicating the relationship between the absolute value | θ | of the steering wheel steering angle θ and the gain G instead of the gain table, and uses the function. The gain G corresponding to the steering angle θ may be calculated. The signal value output by the calculation of the neutral torque correction value gain control unit B13 as described above changes in the vicinity of the neutral position of the steering wheel 11 as shown in FIG. In particular, it should be noted that within the correction region (| θ | ≦ Δθ), it gradually increases as the steering wheel steering angle θ increases, and gradually changes toward “0, 0” beyond the correction region.

  The calculator B14 adds the steering torque T detected by the steering torque sensor 32 and the output signal value G · Ta of the neutral torque correction gain controller, and outputs the result to the calculator B15. The arithmetic unit B15 subtracts the output signal value T + G · Ta from the arithmetic unit B14 from the target reaction force torque T * calculated by the target reaction force torque calculation unit B11 and supplies the result to the PI control calculation unit B16. Subtracting the output signal value T + G · Ta from the target reaction force torque T * of the calculator B15 means that the target reaction force torque T * is controlled and input, and the output signal value T + G · Ta is input by feedback. Means that. The addition of the output signal value G · Ta from the neutral torque correction value gain controller B13 to the steering torque T in the calculator B14 affects the feedback control by the detected steering torque T in the vicinity of the neutral position of the steering handle 11. Means to cancel.

The PI control calculation unit B16 calculates the motor torque command value Tmc by executing the PI control calculation of the following equation 1 using the output signal value T * − (T + G · Ta) of the calculator B15.
Tmc = Kp1 · {T * − (T + G · Ta)} + Ki1 · ∫ {T * − (T + G · Ta)} dt Equation 1
In Equation 1, Kp1 is a predetermined gain of the proportional term in the PI control calculation, and Ki1 is a predetermined gain of the integral term in the PI control calculation. Then, the PI control calculation unit B16 drives and controls the reaction force torque electric motor 14 via the drive circuit 36 in accordance with the motor torque command value Tmc. By this drive control, the reaction force torque electric motor 14 is operated to apply reaction force torque to the steering shaft 12 via the speed reduction mechanism 13. Therefore, the driver turns the steering handle 11 while receiving the reaction torque.

  In this case, the motor torque command value Tmc basically uses the target reaction force torque T * calculated based on the detected steering angle θ as a control input, and the detected steering torque T as a feedback input. Determined according to the PI control law. Therefore, basically, the target reaction torque T * is applied to the steering shaft 12, and the driver rotates the steering handle 11 while feeling the target reaction torque T *.

  Further, when the steering handle 11 is in the vicinity of the neutral position and the steering angle θ is within the correction region of FIG. 6, the neutral torque correction control amount G · Ta is added to the steering torque T as the feedback input. The influence of the offset amount included in the detected steering torque T on the feedback control is canceled. Specifically, it is assumed that the detected steering angle θ is substantially “0” in a state in which the steering handle is in the vicinity of the neutral position and the driver releases his hand from the steering handle 11. In this case, the target reaction force torque T * calculated by the target reaction force torque calculation unit B11 is substantially “0”. However, if the detected steering torque T includes an offset amount, this offset amount cannot be ignored by the integral term calculation in the PI control calculation unit B16, and the motor torque command value Tmc drives the reaction torque electric motor 14. May start to be a valid value. As a result, as described in the background art, there is a possibility that the steering handle 11 starts to rotate left and right regardless of the operation by the driver near the neutral position.

  However, according to the above embodiment, the neutral torque correction control amount G · Ta acts so as to cancel the offset amount of the detected steering torque T. That is, in the case of this embodiment, the detected steering torque T including this offset amount is negative (or positive) means that the driver has operated the steering handle 11 to turn leftward (rightward). It corresponds to that. Since the target reaction torque T * in this case is substantially “0”, the detected steering torque T including the offset amount acts to rotate the steering handle 11 in the right direction (or left direction). . On the other hand, the neutral torque correction control amount G · Ta output from the neutral torque correction value gain control unit B13 can be understood from the graphs of FIGS. 4 to 6 so that the steering handle 11 rotates in the right direction (or left direction). Indicates a positive (or negative) value. The neutral torque correction control amount G · Ta is added to the steering torque T by the calculator B14, and acts to cancel the negative (or positive) value of the detected steering torque T.

  From another viewpoint, the neutral torque correction control amount G · Ta indicating a positive (or negative) value with respect to the rightward (or leftward) rotation of the steering handle 11 is obtained by subtraction of the calculator B15. The sign is inverted and input to the PI control calculation unit B16. This means that when the steering wheel 11 is rotated rightward (or leftward), the neutral torque correction control amount G · Ta rotates the steering wheel 11 leftward (or rightward), that is, in the reverse direction. Works. For this reason, even if the steering handle 11 is in the vicinity of the neutral position and is not operated by the driver, even if the detected steering torque T includes an offset amount, the integral term of the PI control causes the above-mentioned conventional As in the above device, it is possible to avoid a situation in which the steering handle 11 rotates left and right regardless of the operation by the driver.

  Further, when the steering handle 11 is steered by the driver, if the steering angle θ of the steering handle 11 exceeds the correction region of FIG. 6 and enters the non-correction region, the neutral torque correction value gain control unit B13 The gain G gradually changes from “1.0” to “0.0” (see FIG. 5). Therefore, in this case, the neutral torque correction control amount G · Ta gradually changes from a positive or negative value to “0.0” (see FIG. 6), and the canceling action for the offset amount of the steering torque T is performed. Decrease gradually. As a result, it is possible to smoothly shift from the cancel control of the offset amount of the steering torque T according to the steering angle θ to the normal feedback control using the steering torque, and the driver suddenly operates the steering handle 11 with respect to the steering operation. Therefore, the driver does not feel uncomfortable with the steering operation of the steering wheel 11.

  On the other hand, the turning control unit B20 includes a target turning angle calculation unit B21, a calculator B22, and a PI control calculation unit B23. The target turning angle calculation unit B21 refers to a target turning angle table prepared in advance in the ECU 35 and calculates a target turning angle δ * according to the steering wheel steering angle θ. As shown in FIG. 7, the target turning angle table stores a target turning angle δ that increases nonlinearly as the steering wheel steering angle θ increases. In addition, the target turning angle calculation unit B21 corrects the calculated target turning angle δ * according to the vehicle speed V. The target turning angle calculation unit B21 calculates a vehicle speed coefficient Kv corresponding to the vehicle speed V with reference to a vehicle speed coefficient table prepared in advance in the ECU 35. As shown in FIG. 8, the vehicle speed coefficient table stores a vehicle speed coefficient Kv that decreases across “1.0” as the vehicle speed V increases from “0.0”. Then, the target turning angle calculation unit B21 multiplies the calculated target turning angle δ * by the calculated vehicle speed coefficient Kv, and outputs a new target turning angle δ * corrected according to the vehicle speed V.

  The target turning angle calculation unit B21 defines in advance a function indicating the relationship between the steering wheel steering angle θ and the target turning angle δ * in place of the target turning angle table, and uses the function. The target turning angle δ * corresponding to the steering angle θ may be calculated. As for the vehicle speed coefficient Kv, a function indicating the relationship between the vehicle speed V and the vehicle speed coefficient Kv is defined in advance instead of the vehicle speed coefficient table, and the vehicle speed coefficient Kv corresponding to the vehicle speed V is calculated using the function. You may make it do. Further, in the calculation of the target turning angle δ *, the target turning angle δ * that changes nonlinearly with respect to the steering wheel steering angle θ is calculated, but changes linearly with respect to the steering wheel steering angle θ. The target turning angle δ * may be calculated. Further, the correction of the target turning angle δ * by the vehicle speed coefficient Kv may be omitted.

  The target turning angle δ * calculated in this way is supplied to the calculator B22. The calculator B22 receives the detected turning angle δ from the turning angle sensor 33, and subtracts the detected turning angle δ from the target turning angle δ * and supplies it to the PI control calculation unit B23. Subtracting the detected turning angle δ * from the target turning angle δ * of the calculator B22 means that the target turning angle δ * is controlled and input, and that the detected turning angle δ is input by feedback. means.

The PI control calculation unit B23 calculates the motor rotation angle command value δmc by executing the PI control calculation of the following formula 2 using the output signal value δ * -δ of the calculator B22.
δmc = Kp2 · (δ * −δ) + Ki2 · ∫ (δ * −δ) dt Equation 2
In Equation 2, Kp2 is a predetermined gain of the proportional term in the PI control calculation, and Ki2 is a predetermined gain of the integral term in the PI control calculation. Then, the PI control calculation unit B23 drives and controls the steered electric motor 24 via the drive circuit 37 in accordance with the motor rotation angle command value δmc. By this drive control, the steered electric motor 24 is actuated to drive the steered shaft 21 in the axial direction via the ball screw mechanism 25 and steer the left and right front wheels FW1, FW2 to the target steered angle δ *. To do. Therefore, the left and right front wheels FW1 and FW2 are steered left and right in response to the driver's turning operation of the steering handle 11 to the left and right.

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

  For example, in the above embodiment, the PI control by the PI control calculation units B16 and B23 is adopted in the control of the reaction torque electric motor 14 and the steering electric motor 24. However, the present invention is applied to control having at least an integral term in the control of the reaction force torque electric motor 14. Therefore, PID control may be employed instead of these PI control. In this case, the differential terms Kd1 · d {T * − (T + G · Ta)} / dt and Kd2 · d (δ * −δ) / dt are added to the PI control calculations of the above formulas 1 and 2, respectively. The torque command value Tmc and the motor rotation angle command value δmc may be calculated. The Kd1 and Kd2 are predetermined gains of the differential term in the PID control calculation.

  In the above embodiment, the left and right front wheels FW1 and FW2 are steered by driving the steered shaft 21 in the axial direction via the ball screw mechanism 25 by the steered electric motor 24 assembled to the steered shaft 21. I tried to do it. However, instead of this, the steered shaft 21 is constituted by a rack bar, the pinion gear is meshed with the rack teeth of the rack bar, and the pinion gear is rotated around the axis line by the electric motor via the speed reduction mechanism, so that the left and right front wheels FW1, You may make it steer FW2.

1 is an overall schematic diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is a functional block diagram showing the function implement | achieved by the electronic control unit of FIG. 1 by execution of a computer program. It is a graph which shows the relationship between a steering wheel steering angle and a target reaction force torque. It is a graph which shows the relationship between a steering wheel steering angle and a neutral torque correction value. It is a graph which shows the relationship between the absolute value of a steering wheel steering angle, and a gain. It is a time chart which shows the change of the neutral torque correction control amount with respect to a steering angle. It is a graph which shows the relationship between a steering wheel steering angle and a target turning angle. It is a graph which shows the relationship between a vehicle speed and a vehicle speed coefficient. It is a functional block diagram of the conventional control apparatus which controls generation | occurrence | production of steering reaction force torque by PI control method. (A)-(C) is an explanatory view for explaining generation of right-and-left rotation of the steering handle near the neutral position due to the offset amount of the detected steering torque by the conventional PI control method. It is explanatory drawing for demonstrating that a motor torque command value increases by the integral term of the conventional PI control method resulting from the offset amount of a detected steering torque.

Explanation of symbols

FW1, FW2 ... front wheel, 11 ... steering handle, 13 ... electric motor for reaction torque, 20 ... steering device, 24 ... electric motor for turning, 31 ... steering angle sensor, 32 ... steering torque sensor, 35 ... electronic control Unit (ECU), B10 ... torque control unit, B11 ... target reaction torque calculation unit, B12 ... neutral torque correction value calculation unit, B13 ... neutral torque correction value gain control unit, B14, B15 ... calculation unit, B15 ... PI control Arithmetic unit.

Claims (3)

A steering wheel that is turned by a driver;
An electric motor for reaction force torque connected to a steering shaft connected to the steering handle for applying reaction force torque to the steering operation of the steering handle;
An electric motor for turning to steer the steered wheels;
A reaction torque application control means for controlling the application of the reaction torque to the steering operation of the steering handle by drivingly controlling the electric motor for the reaction torque according to the steering operation of the steering handle;
In a steer-by-wire vehicle steering apparatus, comprising: a steering control unit that drives and controls the steering electric motor according to a steering operation of a steering handle, and steers the steered wheels.
The reaction torque application control means,
A steering angle sensor for detecting the steering angle of the steering wheel;
A steering torque sensor that is assembled to the steering shaft and detects a steering torque acting on the steering shaft;
A target reaction torque calculator for calculating a target reaction torque based on the steering angle detected by the steering angle sensor;
The calculated target reaction torque is used as a control input and the detected steering torque is used as a feedback input so that the calculated target reaction torque is applied to the steering shaft in accordance with the difference between the two inputs. A motor torque command value calculating unit for calculating a motor torque command value by a calculation including at least an integral term of the difference,
The detected steering angle is input, and an offset amount of the steering torque detected by the steering torque sensor when the steering handle is in the vicinity of the neutral position is configured by canceling means for canceling by the input steering angle. A vehicle steering apparatus. In the vehicle steering apparatus according to claim 1,
The canceling means,
A neutral torque correction value calculator that calculates a neutral torque correction value that changes in proportion to the detected steering angle when the absolute value of the detected steering angle is within a predetermined minute value range;
A steering apparatus for a vehicle, comprising: a feedback amount correction means for adding the calculated neutral torque correction value to a side where the feedback amount increases in the calculation of the motor torque command value calculation unit. In the vehicle steering apparatus according to claim 2,
The neutral torque correction value calculation unit further steers the vehicle so that the absolute value of the neutral torque correction value is gradually reduced as the detected absolute value of the steering angle moves away from the predetermined minute value range. apparatus.

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