Steering control device, electric power steering device, and vehicle

Abstract

This steering control device (11) is provided with: a target steering torque setting unit (11) that sets a target steering torque for a steering system; and a steering torque control unit (23) that controls, on the basis of the deviation between the target steering torque and the steering torque acting on the steering system, a steering assist torque required to follow the target steering torque, the target steering torque setting unit sets the target steering torque on the basis of the steering torque and the steering assist torque during parking, and controls, on the basis of the deviation between the target steering torque and the steering torque acting on the steering system, the steering assist torque required to follow the target steering torque. In the first vehicle speed region, the target steering torque is set on the basis of the steering torque, the steering assist torque, the steering angle of the steering system, and the vehicle speed, and in the second vehicle speed region, the target steering torque is set on the basis of the steering angle and the vehicle speed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a steering control device, an electric power steering device, and a vehicle. BACKGROUND

[0002] An electric power steering device has an electric motor that generates a steering assist torque for steering and a steering control device that controls the electric motor, and adds a steering assist force to a steering mechanism of a vehicle such as an automobile. Such an electric power steering device has an advantage of being lightweight and compact compared to a hydraulic electric power steering device.

[0003] Patent Document 1 below discloses an electric power steering device that can easily achieve an equivalent steering torque for a vehicle driving information such as a steering angle, without being affected by a change in mechanism characteristics caused by a road surface state or a chronological aging of a steering mechanism. The electric power steering device generates a target steering torque based on the vehicle driving information, converts the generated target steering torque into a target twist angle, calculates a target twist angle speed corresponding to a deviation between the target twist angle and a detected twist angle, and controls so that the twist angle speed follows the target twist angle speed.

[0004] Patent Document 2 below discloses an electric power steering device that realizes a torque feedback system of a simple structure, without adopting a structure that decides a target steering torque based on a steering angle and a vehicle speed. The electric power steering device calculates an output side torque as a sum of a detected torque and an assist torque, and calculates a target steering torque from the output side torque based on predetermined output side torque-target steering torque relationship information. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent No. 6504322 Patent Document 2: Japanese Patent No. 4161707 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] In the electric power steering apparatus disclosed in the above-described Patent Document 1, the target steering torque is calculated using a basic map, a damper component, and a hysteresis component. Therefore, when the vehicle speed is 0 [km / h] (parking state), the steering angle is 0 [deg] (neutral position), and the driver's hand is removed from the steering wheel (so-called steering wheel), the steering wheel attempts to return to the neutral position, which is an unintended action of the driver. Further, when the road surface friction is greater than the assist torque, the steering wheel stops moving, but in the electric power steering apparatus disclosed in the above-described Patent Document 1, the target steering torque corresponding to the steering angle is continuously output. Since the steering torque is set to follow the target steering torque, current continues to flow, and there is a problem of unnecessary power consumption. Further, if this state continues for a long time in idling, the electric motor can overheat and enter an overheat protection state, and the performance can also decrease.

[0007] In the electric power steering apparatus disclosed in the above-described Patent Document 2, the target steering torque is determined only by the output-side torque (sum of the detected torque and the assist torque) acting on the wheel side. Therefore, when the road surface reaction torque is less than the mechanism friction torque, the target steering torque becomes 0, and no assist torque acting on the side to return the steering wheel is generated. That is, the driver must apply a torque to the steering wheel to return the steering wheel, and there is a problem of a decrease in steering feel.

[0008] The present disclosure was achieved in view of the above-described circumstances, and aims to provide a steering control apparatus, an electric power steering apparatus, and a vehicle that can prevent unnecessary current consumption at the time of parking and a decrease in steering feel at the time of running due to differences in the characteristics of the target steering torque required depending on the vehicle speed. Technical means for solving the technical problem

[0009] To solve the above-described problems, a steering control apparatus according to one embodiment of the present disclosure includes a target steering torque setting section that sets a target steering torque for a steering system, and a steering torque control section that controls a steering assist torque required for the steering torque to follow the target steering torque based on a deviation between the target steering torque and the steering torque acting on the steering system, the target steering torque setting section setting the target steering torque based on the steering torque and the steering assist torque at the time of parking, setting the target steering torque based on the steering torque, the steering assist torque, a steering angle of the steering system, and a vehicle speed in a first vehicle speed region, and setting the target steering torque based on the steering angle and the vehicle speed in a second vehicle speed region.

[0010] Further, an electric power steering apparatus according to one embodiment of the present disclosure includes a steering torque detection section that detects a steering torque acting on a steering system, a steering state detection section that detects a steering angle of the steering system, an electric motor that supplies a steering assist torque to the steering system, and the above-described steering control apparatus that controls driving of the electric motor based on the detected steering torque and the steering angle.

[0011] Further, a vehicle according to one embodiment of the present disclosure includes a vehicle speed detection section that detects a vehicle speed, and the above-described electric power steering apparatus that controls the steering assist torque supplied to the steering system based on the vehicle speed detected by the vehicle speed detection section. Effects of Invention

[0012] According to the present disclosure, it is possible to prevent unnecessary current consumption at the time of parking and a decrease in steering feeling at the time of running due to a difference in characteristics of a target steering torque required according to a vehicle speed. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a block diagram showing a main part structure of an electric power steering apparatus and a vehicle according to Embodiment 1 of the present disclosure. Figure 2 is a block diagram showing a main part structure of a control unit as a steering control apparatus according to Embodiment 1 of the present disclosure. Figure 3 is a block diagram showing an internal structure of a target steering torque setting section in Embodiment 1 of the present disclosure. Figure 4A is a block diagram showing a structure example of a first torque operation section in Embodiment 1 of the present disclosure. Figure 4B is a block diagram showing another structure example of the first torque operation section in Embodiment 1 of the present disclosure. Figure 5 is a graph showing one example of a characteristic of a first torque calculated by the first torque operation section in Embodiment 1 of the present disclosure. Figure 6A is a block diagram showing a structure example of a second torque operation section in Embodiment 1 of the present disclosure. Figure 6B is a block diagram showing another structure example of the second torque operation section in Embodiment 1 of the present disclosure. Figure 7 is a graph showing one example of a characteristic of a second torque calculated by the second torque operation section in Embodiment 1 of the present disclosure. Figure 8is a diagram for illustrating one example of the action of the mediation section when the vehicle speed is changed in the case where the steering angle is other than the neutral position in Embodiment 1 of the present disclosure. Figure 9 is a block diagram showing one example of the internal structure of the torque feedback operation section in Embodiment 1 of the present disclosure. Figure 10 is a block diagram showing the internal structure of the target steering torque setting section in Embodiment 2 of the present disclosure. Figure 11 is a diagram showing one example of the vehicle speed sensing gain map in Embodiment 2 of the present disclosure. Figure 12 is a block diagram showing the internal structure of the target steering torque setting section in Embodiment 3 of the present disclosure. Figure 13A is a block diagram showing a structure example of the 1st map torque operation section in Embodiment 3 of the present disclosure. Figure 13B is a block diagram showing another structure example of the 1st map torque operation section in Embodiment 3 of the present disclosure. Figure 14A is a block diagram showing a structure example of the 2nd map torque operation section in Embodiment 3 of the present disclosure. Figure 14B is a block diagram showing another structure example of the 2nd map torque operation section in Embodiment 3 of the present disclosure. Figure 15 is a diagram showing one example of the 1st torque map and the 2nd torque map in Embodiment 3 of the present disclosure. DETAILED DESCRIPTION

[0014] Hereinafter, a steering control device, an electric power steering device, and a vehicle according to the present disclosure will be described in detail with reference to the drawings. In each embodiment, the same or equivalent parts are designated by the same reference numerals, and overlapping descriptions will be omitted.

[0015] [Embodiment 1] 〈Electric Power Steering Device and Vehicle〉 Figure 1 is a block diagram showing the main part structure of an electric power steering device and a vehicle according to Embodiment 1 of the present disclosure. As shown in Figure 1 the vehicle VE according to the present embodiment includes a vehicle speed sensor 8 (vehicle speed detection section) and an electric power steering device PS. The electric power steering device PS includes a steering wheel 1, a steering shaft 2, a steering wheel 3, a steering angle sensor 4 (steering state detection section), a torque sensor 5 (steering torque detection section), an electric motor 6, a reduction mechanism 7, a current sensor 9, a motor rotation angle sensor 10, and a control unit 11 (steering control device).

[0016] The steering wheel 1 is a so-called steering wheel that is operated by a driver of the vehicle VE to provide a steering angle to the steering wheel 3 of the vehicle VE. The steering shaft 2 is connected to the steering wheel 1 and rotates in accordance with the rotation of the steering wheel 1. The steering wheel 3 is provided on the left and right sides of the vehicle VE and steers in accordance with the rotation of the steering shaft 2. Furthermore, a mechanism that steers the steering wheel 3 including the steering wheel 1 and the steering shaft 2 is referred to as a "steering device (steering system)".

[0017] The steering angle sensor 4 is arranged at the steering wheel 1 and detects a steering angle of the steering wheel 1. The torque sensor 5 is arranged at the steering shaft 2 and detects a steering torque acting on the steering shaft 2. The electric motor 6 is connected to the steering shaft 2 via the reduction mechanism 7 and provides a steering assist torque to the steering shaft 2. The vehicle speed sensor 8 detects a vehicle speed of the vehicle VE. The current sensor 9 detects a current flowing through the electric motor 6. The motor rotation angle sensor 10 detects a rotation angle of the electric motor 6.

[0018] The control unit 11 controls the drive of the electric motor 6 on the basis of the detection results of the steering angle sensor 4, the torque sensor 5, the vehicle speed sensor 8, the current sensor 9, and the motor rotation angle sensor 10 to generate a steering assist torque for the steering device. Specifically, the control unit 11 calculates the steering assist torque to be provided to the steering shaft 2 on the basis of the above-described detection results and controls the current of the electric motor 6 required to generate the steering assist torque. Hereinafter, the control unit 11 will be described in detail.

[0019] <Steering control device> Figure 2 is a block diagram showing a main part structure of the control unit of the steering control device according to Embodiment 1 of the present disclosure. As shown in Figure 2 , the control unit 11 includes a control portion 12 and a current drive portion 13. The control portion 12 includes a differentiator 21a, a target steering torque setting portion 22, a torque feedback calculation portion 23 (steering torque control portion), and a multiplier 24.

[0020] The differentiator 21a differentiates the rotation angle of the electric motor 6 detected by the motor rotation angle sensor 10 and calculates a rotation speed of the electric motor 6 (hereinafter, referred to as "motor rotation speed"). Furthermore, the differentiator 21a and the motor rotation angle sensor 10 constitute a motor rotation speed detection portion 21 that detects the motor rotation speed.

[0021] The target steering torque setting section 22 sets a target steering torque for the steering gear. Here, the steering angle of the steering wheel 1 detected by the steering angle sensor 4, the steering torque detected by the torque sensor 5, the vehicle speed of the vehicle VE detected by the vehicle speed sensor 8, and the steering assist torque (described later) output from the multiplier 24 are input to the target steering torque setting section 22. The target steering torque setting section 22 sets a target steering torque for the steering gear using these detection results and the like. Further, details of the target steering torque setting section 22 are described later.

[0022] The torque feedback operation section 23 is input with the steering torque detected by the torque sensor 5, the motor rotational angular velocity detected by the motor rotational angular velocity detection section 21, and the target steering torque set by the target steering torque setting section 22. The torque feedback operation section 23 operates a target steering assist torque required for the steering torque to follow the target steering torque based on the deviation of the target steering torque from the steering torque and the motor rotational angular velocity. Further, details of the torque feedback operation section 23 are described later.

[0023] The multiplier 24 multiplies the current flowing through the motor 6 detected by the current sensor 9 by a torque constant Kt defined in advance, thereby calculating the steering assist torque. Specifically, if the current flowing through the motor 6 is set as I, the multiplier 24 performs the operation shown in (1) below, thereby calculating the steering assist torque Tmotor. Further, the torque constant Kt is set to a value in which the reduction ratio of the reduction mechanism 7 is also taken into account. Tmotor = I x Kt... (1)

[0024] Further, the control section 12 of the control unit 11 is realized by a microcomputer including a CPU (Central Processing Unit) and a memory. The memory provided to the microcomputer can include both a volatile memory and a non-volatile memory. The current drive section 13 is realized by, for example, an analog circuit provided with a plurality of switching elements such as FETs (Field Effect Transistors).

[0025] Here, a summary of the operation of the control unit 11 which is a main part of the electric power steering apparatus PS is described. Further, the operation described below is repeatedly performed at a predetermined control cycle.

[0026] First, the control section 12 of the control unit 11 acquires the steering angle detected by the steering angle sensor 4, the vehicle speed detected by the vehicle speed sensor 8, the steering torque detected by the torque sensor 5, and the motor rotation angle detected by the motor rotation angle sensor 10. Then, the differentiator 12a of the control section 12 differentiates the motor rotation angle detected by the motor rotation angle sensor 10 to find the motor rotation angular velocity. Further, the multiplier 24 of the control section 12 multiplies the current I flowing through the motor 6 detected by the current sensor 9 by the torque constant Kt to find the steering assist torque, as shown in the above (1) formula.

[0027] Next, the target steering torque setting section 22 of the control section 12 sets the target steering torque using the steering angle detected by the steering angle sensor 4, the vehicle speed detected by the vehicle speed sensor 8, the steering torque detected by the torque sensor 5, and the steering assist torque found by the multiplier 24. Next, the torque feedback operation section 23 of the control section 12 operates the target steering assist torque required to make the steering torque follow the target steering torque based on the deviation between the target steering torque set by the target steering torque setting section 22 and the steering torque detected by the torque sensor 5, and the motor rotation angular velocity found by the differentiator 21a. Next, the current drive section 13 of the control unit 11 controls the current flowing through the motor 6 so that the steering mechanism generates the target steering assist torque operated by the torque feedback operation section 23.

[0028] Figure 3 is a block diagram showing the internal structure of the target steering torque setting section in Embodiment 1 of the present disclosure. As shown in Figure 3 , the target steering torque setting section 22 includes an adder 31, a first torque operation section 32, a second torque operation section 33, and a mediator 34.

[0029] The adder 31 adds the steering torque detected by the torque sensor 5 to the steering assist torque found by the multiplier 24 to find the road reaction force estimate. Here, the road reaction force estimate found by the adder 31 is the torque acting on the steering shaft 2 due to the wheel steering of the steering mechanism, and can be equivalently treated as the road reaction force torque generated by the steered wheels 3.

[0030] Even if the actual road reaction force torque generated in the steered wheels 3 is not directly sensed, this road reaction force estimate can be found by operation. Specifically, if the steering torque detected by the torque sensor 5 is set as Tsens, the road reaction force estimate Test can be found using the well-known (2) formula shown below. Test = Tsens + Tmotor… (2)

[0031] Based on the above (2) formula, in Figure 3In the illustrated structure, the road surface reaction force estimation value is obtained by adding the steering torque Tsens detected by the torque sensor 5 and the steering assist torque Tmotor calculated by the multiplier 24.

[0032] The first torque calculation section 32a calculates the first torque having a magnitude corresponding to the absolute value of the input road surface reaction force estimation value. The sign determination section 32b determines the sign of the input road surface reaction force estimation value, and outputs "+1" in the case where the sign is positive and outputs "-1" in the case where the sign is negative. The multiplier 32c multiplies the first torque calculated by the first torque calculation section 32a by the value output from the sign determination section 32b. Figure 4A is a block diagram showing a structure example of the first torque calculation section in Embodiment 1 of the present disclosure. Figure 4A The illustrated first torque calculation section 32 includes a first torque calculation section 32a, a sign determination section 32b, and a multiplier 32c.

[0033] The first torque calculation section 32a calculates the first torque having a magnitude corresponding to the absolute value of the input road surface reaction force estimation value. The sign determination section 32b determines the sign of the input road surface reaction force estimation value, and outputs "+1" in the case where the sign is positive and outputs "-1" in the case where the sign is negative. The multiplier 32c multiplies the first torque calculated by the first torque calculation section 32a by the value output from the sign determination section 32b.

[0034] Figure 5 is a graph showing one example of the characteristics of the first torque calculated by the first torque calculation section in Embodiment 1 of the present disclosure. As shown in Figure 5 The first torque calculated by the first torque calculation section 32 has characteristics (also including a flat shape) of gradually increasing as the absolute value of the road surface reaction force estimation value increases. Further, the first torque takes only positive values.

[0035] Figure 4B is a block diagram showing another structure example of the first torque calculation section in Embodiment 1 of the present disclosure. Figure 4B The illustrated first torque calculation section 32 is configured to calculate the first torque from Figure 4A The illustrated first torque calculation section 32 omits the sign determination section 32b and the multiplier 32c, and only adopts the first torque calculation section 32a. Figure 4B In the illustrated first torque calculation section 32, the first torque that is positive or negative is calculated in accordance with the sign of the road surface reaction force estimation value.

[0036] The second torque calculation section 33 calculates the second torque based on the vehicle speed detected by the vehicle speed sensor 8 and the steering angle detected by the steering angle sensor 4. Figure 6A is a block diagram showing a structure example of the second torque calculation section in Embodiment 1 of the present disclosure. Figure 6A The illustrated second torque calculation section 33 includes a second torque map 33a, a sign determination section 33b, and a multiplier 32c.

[0037] The 2nd torque map 33a is a map that defines a relationship among vehicle speed, steering angle, and 2nd torque. When vehicle speed and steering angle are input, the 2nd torque map 33a outputs a 2nd torque corresponding to the vehicle speed and steering angle. The sign determination section 33b determines the sign of the input steering angle, and outputs "+1" in the case where the sign is positive, and outputs "-1" in the case where the sign is negative. The multiplier 33c multiplies the 2nd torque output from the 2nd torque map 33a by the value output from the sign determination section 33b.

[0038] Figure 7 is a graph showing one example of the characteristics of the 2nd torque calculated by the 2nd torque calculation section in Embodiment 1 of the present disclosure. As shown in Figure 7 , the 2nd torque calculated by the 2nd torque calculation section 33 is a characteristic (also including a flat shape) that does not decrease as vehicle speed becomes higher in the case where the absolute value of the steering angle is the same, and is a characteristic (also including a flat shape) that does not decrease as the absolute value of the steering angle becomes larger in the case where vehicle speed is the same. Further, the 2nd torque takes only positive values.

[0039] Figure 6B is a block diagram showing another structural example of the 2nd torque calculation section in Embodiment 1 of the present disclosure. Figure 6B The 2nd torque calculation section 33 shown in Figure 6A The 2nd torque calculation section 33 shown in Figure 6B In the 2nd torque calculation section 33 shown in

[0040] The mediation section 34 outputs a target steering torque based on the vehicle speed detected by the vehicle speed sensor 8, the 1st torque calculated by the 1st torque calculation section 32, and the 2nd torque calculated by the 2nd torque calculation section 33. The target steering torque output by the mediation section 34 is appropriate for each vehicle speed region. Figure 8 is a graph for explaining one example of the action of the mediation section when the vehicle speed is changed in the case where the steering angle is other than the neutral position in Embodiment 1 of the present disclosure.

[0041] As shown in Figure 8 , the vehicle speed region is divided by the time when the vehicle is stopped (vehicle speed 0) and the boundary vehicle speed V1. The vehicle speed region in which the vehicle speed is "0 < vehicle speed < V1" is set as the "1st vehicle speed region", and the vehicle speed region in which the vehicle speed is "V1 < vehicle speed" is set as the "2nd vehicle speed region". As shown in Figure 8As shown, the mediation section 34 outputs a target steering torque that coincides with the 1st torque at the time of parking, coincides with the 2nd torque at the boundary vehicle speed VI, and is a value intermediate to the 1st torque and the 2nd torque in the intermediate (1st vehicle speed region) and does not produce discontinuity according to the vehicle speed. The mediation section 34 can also calculate the 1st torque as the target steering torque at the time of parking, and calculate the target steering torque based on the 1st torque, the 2nd torque, and the vehicle speed outside the time of parking.

[0042] Here, the 1st torque is a torque calculated from the sum of the steering torque and the steering assist torque, i.e., the road surface reaction force estimation value, and the 2nd torque is a torque calculated from the steering angle and the vehicle speed. Therefore, the target steering torque setting section 22 can set the target steering torque based on the steering torque and the steering assist torque at the time of parking. Further, in the 1st vehicle speed region, the target steering torque can be set based on the steering torque, the steering assist torque, the steering angle of the steering system, and the vehicle speed. Further, in the 2nd vehicle speed region, the target steering torque can be set based on the steering angle and the vehicle speed.

[0043] Figure 9 is a block diagram showing one example of the internal structure of the torque feedback operation section in Embodiment 1 of the present disclosure. As shown, the torque feedback operation section 23 includes a subtracter 41, a 1st target steering assist torque operation section 42, a 2nd target steering assist torque operation section 43, a 3rd target steering assist torque operation section 44, and an adder 45. Figure 9

[0044] The subtracter 41 operates the deviation between the target steering torque and the steering torque. The 1st target steering assist torque operation section 42 includes an integrator 42a and an amplifier 42b, and calculates the 1st target steering assist torque by multiplying the deviation operated by the subtracter 41 by the integral control gain KTI after integrating the deviation. The 2nd target steering assist torque operation section 43 includes an amplifier 43a, and calculates the 2nd target steering assist torque by multiplying the motor rotational angular velocity by the velocity control gain KTV.

[0045] The 3rd target steering assist torque operation section 44 includes an amplifier 44a, and calculates the 3rd target steering assist torque by multiplying the deviation operated by the subtracter 41 by the proportional control gain KTP. The adder 45 adds the 1st target steering assist torque, the 2nd target steering assist torque, and the 3rd target steering assist torque to set the target steering assist torque. Further, the torque feedback operation section 23 is not limited to the structure shown, and can be any structure as long as it has a function of causing the steering torque to follow the target steering torque. Figure 9

[0046] ​​In the present embodiment, the target steering torque is set to an appropriate value for each vehicle speed region by the target steering torque setting section 22, and the target steering assist torque is controlled by the torque feedback operation section 23 so that the steering torque of the driver follows the target steering torque. Therefore, the driver can steer with an appropriate torque.

[0047] Here, in the present embodiment, the first torque is calculated based on the road surface reaction force estimation value, and therefore, even if the driver removes his or her hand from the steering wheel 1 at a position other than the position at which the steering angle is 0 [deg], the target steering torque is "0" at the position at which the road surface reaction force estimation value is "0". Further, the position at which the road surface reaction force estimation value is "0" is a position at which the mechanism friction torque is balanced, and is not limited to the neutral position of the steering wheel 1. In a state in which the driver removes his or her hand from the steering wheel 1, the steering torque becomes "0", and therefore, the deviation between the target steering torque and the steering torque disappears, and the unnecessary current consumption at the time of parking can be suppressed.

[0048] Further, in the present embodiment, the mediation section 34 is provided to continuously shift the target steering torque from the first torque to the second torque. The second torque is calculated based on the steering angle and the vehicle speed in the second vehicle speed region, and therefore, the target steering torque is set in the direction in which the steering wheel 1 is returned to the neutral position at a position other than the neutral position. Thus, in the second vehicle speed region, when the driver's hand is removed from the steering wheel 1 (the steering torque is "0"), the steering wheel 1 can be returned to the neutral position, and the reduction in the steering feeling can be prevented.

[0049] Further, in the above-described embodiment, the case in which the target steering torque at the time of parking is only the first torque (100% of the first torque) is described, but the case in which the target steering torque is substantially the first torque, such as a case in which the ratio of the first torque to the second torque is 99: 1, is also included. Further, information indicating the rotational angular velocity of the motor or the like can be input to the target steering torque setting section 22 to calculate the target steering torque. By inputting the information indicating the rotational angular velocity of the motor or the like, the target steering torque can be flexibly set based on these additional information, and the convergence, the friction feeling, or the like can be improved.

[0050] Furthermore, in this embodiment, a steering angle sensor 4 is used as the steering state detection unit, and the steering angle detected by the steering angle sensor 4 is used in the target steering torque setting unit 22. However, the result obtained by converting the motor rotation angle detected by the motor rotation angle sensor 10 into a steering angle can be used instead of the detection result of the steering angle sensor 4. For example, the result obtained by converting the motor rotation angle detected by the motor rotation angle sensor 10 into the angle of the steering shaft 2 through the reduction ratio of the reduction mechanism 7 can be used. Moreover, when the motor rotation angle is a relative angle with respect to the angle of the steering shaft 2, it can be determined by the yaw angle sensor or the like (not shown) provided by the vehicle VE that it is driving straight, and compensation can be performed to make the relative angle 0, thereby setting it as the absolute angle of the steering shaft 2.

[0051] [Implementation Method 2] Electric power steering systems and vehicles The electric power steering device and vehicle structure involved in this embodiment are basically the same as... Figure 1 The electric power steering system PS and the vehicle VE shown have the same structure. Therefore, detailed descriptions of the electric power steering system and vehicle involved in this embodiment are omitted.

[0052] <Steering Control Device> The basic structure of the steering control device according to this embodiment is the same as that of the steering control device (control unit 11) according to Embodiment 1. However, the internal structure of the target steering torque setting unit 22 provided in the control unit 11 is different. Hereinafter, the target steering torque setting unit 22 will be described in detail.

[0053] Figure 10 This is a block diagram showing the internal structure of the target steering torque setting unit in Embodiment 2 of this disclosure. Figure 10 As shown, the target steering torque setting unit 22 in this embodiment includes an adder 31, a first torque calculation unit 32, a second torque calculation unit 33, and a regulating unit 35. That is, the target steering torque setting unit 22 in this embodiment is configured to... Figure 3 The adjustment unit 34 of the target steering torque setting unit 22 shown is replaced with the adjustment unit 35.

[0054] The adjustment unit 35 includes a vehicle speed sensing gain map 35a, a multiplier 35b, a subtractor 35c, a multiplier 35d, and an adder 35e. The vehicle speed sensing gain map 35a defines a mapping for the vehicle speed sensing gain corresponding to the vehicle speed. When the vehicle speed is input to the vehicle speed sensing gain map 35a, the vehicle speed sensing gain corresponding to that vehicle speed is output from the vehicle speed sensing gain map 35a.

[0055] Figure 11is a graph showing one example of a vehicle speed sensing gain map in Embodiment 2 of the present disclosure. As shown in Figure 11 The vehicle speed sensing gain map 35a is a map having a characteristic in which the vehicle speed sensing gain continuously changes according to the vehicle speed. The vehicle speed sensing gain prescribed by the vehicle speed sensing gain map 35a takes a value of "0" to "1". Figure 11 The vehicle speed sensing gain map 35a shown in the drawing takes a value of "1" at the time of parking, gradually decreases as the vehicle speed becomes higher in the 1st vehicle speed region, and takes a value of "0" in the 2nd vehicle speed region.

[0056] The multiplier 35b multiplies the 1st torque calculated by the 1st torque calculation section 32 and the vehicle speed sensing gain output from the vehicle speed sensing gain map 35a to calculate the moderated 1st torque. The subtracter 35c subtracts the vehicle speed sensing gain output from the vehicle speed sensing gain map 35a from a value of "1". The multiplier 35d multiplies the 2nd torque calculated by the 2nd torque calculation section 33 and the value output from the subtracter 35c to calculate the moderated 2nd torque. The adder 35e adds the moderated 1st torque calculated by the multiplier 35b and the moderated 2nd torque calculated by the multiplier 35d to calculate the target steering torque.

[0057] Here, as described above, the 1st torque and the vehicle speed sensing gain are multiplied to calculate the moderated 1st torque. In contrast, the 2nd torque and a value obtained by subtracting the vehicle speed sensing gain from a value of "1" are multiplied to calculate the moderated 2nd torque. As shown in Figure 11 At the time of parking, the vehicle speed sensing gain takes a value of "1", and therefore the moderated 2nd torque becomes "0". Further, in the 2nd vehicle speed region, the vehicle speed sensing gain takes a value of "0", and therefore the moderated 1st torque becomes "0". Therefore, for the vehicle speed sensing gain map 35a, it is possible to prescribe the vehicle speed sensing gain that makes the moderated 2nd torque "0" at the time of parking, and it is possible to prescribe the vehicle speed sensing gain that makes the moderated 1st torque "0" in the 2nd vehicle speed region.

[0058] The vehicle speed sensing gain at the time of parking takes a value of "1", and therefore at the time of parking, the 1st torque is set as the target steering torque. The vehicle speed sensing gain in the 1st vehicle speed region takes a value between "0" and "1", and therefore in the 1st vehicle speed region, a value intermediate between the 1st torque and the 2nd torque is set as the target steering torque. The vehicle speed sensing gain in the 2nd vehicle speed region takes a value of "0", and therefore in the 2nd vehicle speed region, the 2nd torque is set as the target steering torque. That is, in the present embodiment, the target steering torque set by the target steering torque setting section 22 is the same as Figure 8 shown in the drawing.

[0059] As described above, in the present embodiment, the 1st torque is also calculated based on the road surface reaction force estimation value, and the mediation section 35 is provided so that the target steering torque is continuously shifted from the 1st torque to the 2nd torque. Thus, as in Embodiment 1, the unnecessary current consumption at the time of parking can be suppressed, and the reduction in steering feeling can be prevented.

[0060] Further, Figure 10 The mediation section 35 shown in the figure is configured to multiply the 2nd torque calculated by the 2nd torque calculation section 33 by a value obtained by subtracting the vehicle speed sensing gain output from the vehicle speed sensing gain map 35a from the value "1" to calculate the post-mediation 2nd torque. However, instead of the vehicle speed sensing gain map 35a, it can also be configured to provide a vehicle speed sensing gain map that outputs a vehicle speed sensing gain obtained by subtracting the vehicle speed sensing gain at each vehicle speed of the vehicle speed sensing gain map 35a from the value "1", and multiply the vehicle speed sensing gain output from the vehicle speed sensing gain map by the 2nd torque calculated by the 2nd torque calculation section 33 to calculate the post-mediation 2nd torque.

[0061] [Embodiment 3] <Electric Power Steering Apparatus and Vehicle> The electric power steering apparatus and vehicle according to the present embodiment have basically the same structure as Figure 1 the electric power steering apparatus PS and the vehicle VE shown in the figure. Therefore, detailed description of the electric power steering apparatus and vehicle according to the present embodiment is omitted.

[0062] <Steering Control Apparatus> The basic structure of the steering control apparatus according to the present embodiment is the same as that of the steering control apparatus (control unit 11) according to Embodiment 1. However, the internal structure of the target steering torque setting section 22 provided in the control unit 11 is different. Hereinafter, the target steering torque setting section 22 is described in detail.

[0063] Figure 12 is a block diagram showing the internal structure of the target steering torque setting section according to Embodiment 3 of the present disclosure. As Figure 12 shown in the figure, the target steering torque setting section 22 according to the present embodiment includes an adder 31, a 1st map torque calculation section 36, a 2nd map torque calculation section 37, and an adder 38. That is, the target steering torque setting section 22 according to the present embodiment is configured to replace the 1st torque calculation section 32, the 2nd torque calculation section 33, and the mediation section 34 of the target steering torque setting section 22 shown in the figure with the 1st map torque calculation section 36, the 2nd map torque calculation section 37, and the adder 38. Figure 3

[0064] The 1st map torque calculation section 36 calculates the 1st map torque based on the road surface reaction force estimation value calculated by the adder 31 and the vehicle speed detected by the vehicle speed sensor 8.​Figure 13A is a block diagram showing a configuration example of the 1st map torque operation section in Embodiment 3 of the present disclosure. Figure 13A The 1st map torque operation section 36 shown includes a 1st torque map 36a, a sign determination section 36b, and a multiplier 36c.

[0065] The 1st torque map 36a is a map that defines a relationship between a vehicle speed, a road reaction force estimation value, and a 1st map torque. When a vehicle speed and a road reaction force estimation value are input to the 1st torque map 36a, a 1st map torque corresponding to the vehicle speed and the road reaction force estimation value is output from the 1st torque map 36a. The sign determination section 36b determines a sign of the input road reaction force estimation value, and outputs "+1" in the case where the sign is positive and outputs "-1" in the case where the sign is negative. The multiplier 36c multiplies the 1st map torque output from the 1st torque map 36a by the value output from the sign determination section 36b.

[0066] The 2nd map torque operation section 37 calculates a 2nd map torque based on a vehicle speed detected by the vehicle speed sensor 8 and a steering angle detected by the steering angle sensor 4. Figure 14A is a block diagram showing a configuration example of the 2nd map torque operation section in Embodiment 3 of the present disclosure. Figure 14A The 2nd map torque operation section 37 shown includes a 2nd torque map 37a, a sign determination section 37b, and a multiplier 37c.

[0067] The 2nd torque map 37a is a map that defines a relationship between a vehicle speed, a steering angle, and a 2nd map torque. When a vehicle speed and a steering angle are input, the 2nd torque map 37a outputs a 2nd map torque corresponding to the vehicle speed and the steering angle. The sign determination section 33b determines a sign of the input steering angle, and outputs "+1" in the case where the sign is positive and outputs "-1" in the case where the sign is negative. The multiplier 37c multiplies the 2nd map torque output from the 2nd torque map 37a by the value output from the sign determination section 37b.

[0068] Figure 15 is a graph showing one example of the 1st torque map and the 2nd torque map in Embodiment 3 of the present disclosure. As shown, the 1st torque map 36a and the 2nd torque map 37a are set in a parking time, a 1st vehicle speed region, and a 2nd vehicle speed region. Figure 15

[0069] ​The first torque map 36a at the time of parking is a characteristic in which the first mapped torque gradually increases as the absolute value of the road surface reaction force estimation value increases (including a flat shape). The first torque map 36a in the first vehicle speed region is a characteristic in which the first mapped torque does not increase as the vehicle speed increases (including a flat shape) in the case where the absolute value of the road surface reaction force estimation value is the same, and is a characteristic in which the first mapped torque does not decrease as the absolute value of the road surface reaction force estimation value increases (including a flat shape) in the case where the vehicle speed is the same. The first torque map 36a in the second vehicle speed region is defined so that the first mapped torque is 0. Further, the first mapped torque takes only a positive value.

[0070] The second torque map 37a at the time of parking is defined so that the second mapped torque is 0. The second torque map 37a in the first vehicle speed region and the second vehicle speed region is a characteristic in which the second mapped torque does not decrease as the vehicle speed increases (including a flat shape) in the case where the absolute value of the steering angle is the same, and is a characteristic in which the second mapped torque does not decrease as the absolute value of the steering angle increases (including a flat shape) in the case where the vehicle speed is the same. Further, the second mapped torque takes only a positive value.

[0071] Figure 13B FIG. 6 is a block diagram showing another example of the first mapped torque operation section in Embodiment 3 of the present disclosure. Figure 13B The first mapped torque operation section 36 shown in FIG. 6 is configured to obtain the first mapped torque from the first torque map 36a. Figure 13A The first mapped torque operation section 36 shown in FIG. 6 omits the sign determination section 36b and the multiplier 36c, and uses only the first torque map 36a. Figure 14B In the first mapped torque operation section 36 shown in FIG. 6, the first mapped torque that is positive or negative is obtained in accordance with the sign of the road surface reaction force estimation value.

[0072] Figure 14B FIG. 7 is a block diagram showing another example of the second mapped torque operation section in Embodiment 3 of the present disclosure. Figure 6B The second mapped torque operation section 37 shown in FIG. 7 is configured to obtain the second mapped torque from the second torque map 37a. Figure 14A The second mapped torque operation section 37 shown in FIG. 7 omits the sign determination section 37b and the multiplier 37c, and uses only the second torque map 37a. Figure 14B In the second mapped torque operation section 37 shown in FIG. 7, the second mapped torque that is positive or negative is obtained in accordance with the sign of the steering angle.

[0073] The adder 38 adds the first mapped torque obtained by the first mapped torque operation section 36 and the second mapped torque obtained by the second mapped torque operation section 37 to obtain the target steering torque.

[0074] Here, as described above, the first mapped torque and the second mapped torque are positive values.Figure 15 As shown, the 2nd torque map 37a at the time of parking is defined so that the 2nd map torque is 0, and thus in the time of parking, the 1st map torque is set as the target steering torque. The 1st torque map 36a and the 2nd torque map 37a in the 1st vehicle speed region are defined as shown, and thus in the 1st vehicle speed region, the target steering torque is set as a value obtained by adding the 1st map torque and the 2nd map torque and without discontinuity according to the vehicle speed. The 1st torque map 36a in the 2nd vehicle speed region is defined so that the 1st map torque is 0, and thus in the 2nd vehicle speed region, the 2nd map torque is set as the target steering torque. Thus, in the present embodiment, the target steering torque set by the target steering torque setting section 22 is also the same as that shown. Figure 15 As shown, the 2nd torque map 37a at the time of parking is defined so that the 2nd map torque is 0, and thus in the time of parking, the 1st map torque is set as the target steering torque. The 1st torque map 36a and the 2nd torque map 37a in the 1st vehicle speed region are defined as shown, and thus in the 1st vehicle speed region, the target steering torque is set as a value obtained by adding the 1st map torque and the 2nd map torque and without discontinuity according to the vehicle speed. The 1st torque map 36a in the 2nd vehicle speed region is defined so that the 1st map torque is 0, and thus in the 2nd vehicle speed region, the 2nd map torque is set as the target steering torque. Thus, in the present embodiment, the target steering torque set by the target steering torque setting section 22 is also the same as that shown. Figure 8 As shown, the 2nd torque map 37a at the time of parking is defined so that the 2nd map torque is 0, and thus in the time of parking, the 1st map torque is set as the target steering torque. The 1st torque map 36a and the 2nd torque map 37a in the 1st vehicle speed region are defined as shown, and thus in the 1st vehicle speed region, the target steering torque is set as a value obtained by adding the 1st map torque and the 2nd map torque and without discontinuity according to the vehicle speed. The 1st torque map 36a in the 2nd vehicle speed region is defined so that the 1st map torque is 0, and thus in the 2nd vehicle speed region, the 2nd map torque is set as the target steering torque. Thus, in the present embodiment, the target steering torque set by the target steering torque setting section 22 is also the same as that shown.

[0075] As described above, in the present embodiment, the 1st torque is calculated based on the road surface reaction force estimation value, and the target steering torque is continuously shifted from the 1st map torque to the 2nd map torque. Thus, as in Embodiment 1, the unnecessary current consumption at the time of parking can be suppressed, and the reduction in steering feeling can be prevented.

[0076] Further, in the present embodiment, the functions of the mediation section 34 in Embodiment 1 and the mediation section 35 in Embodiment 2 can be previously included in the 1st torque map 36a and the 2nd torque map 37a. Thus, in the present embodiment, the target steering torque can be set only by calculating the 1st map torque and the 2nd map torque and adding them, and thus the processing load of the control section 12 can be reduced.

[0077] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be freely changed within the scope of the gist of the present disclosure. For example, the electric power steering apparatus PS described in the above-described embodiments can be a column type or a rack-and-pinion type. Further, the feedback control based on the target steering torque can also be applied to a steer-by-wire reaction force apparatus or the like having at least a torque sensor. In addition, the drawings used in the description of the above-described embodiments represent one example, and are not limited thereto.

[0078] In addition, the control section 12 included in the above-described control unit 11 has a computer system inside. Further, a program for realizing the functions of the control section 12 included in the above-described control unit 11 can be recorded in a recording medium readable by a computer, and the processing in each structure included in the above-described control unit 11 can be executed by reading the program recorded in the recording medium into the computer system and executing the program. Here, "reading the program recorded in the recording medium into the computer system and executing" is included in the case where the program is installed in the computer system. The "computer system" mentioned here includes an OS, a peripheral device, and the like.

[0079] In addition, the "computer system" can include a plurality of computer devices connected via a network including an Internet, or a WAN, a LAN, a dedicated line, or the like. In addition, the "computer-readable recording medium" refers to a portable medium such as a floppy disk, a magneto-optical disk, a ROM, a CD-ROM, and the like, and a storage device such as a hard disk built in a computer system. Thus, the recording medium storing the program can also be a non-transitory recording medium such as a CD-ROM.

[0080] In addition, the recording medium also includes a recording medium provided inside or outside that can be accessed from a distribution server to distribute the program. It can be a structure in which the program is divided into a plurality of, downloaded at different timings respectively, and then combined in each structure provided in the control unit 11, and the distribution server for distributing each divided program can be different. In addition, the "computer-readable recording medium" also includes a medium that retains the program for a certain period of time, as a volatile memory (RAM) inside a computer system that becomes a server or a client when transmitting the program through a network. In addition, the above program can also be a program for realizing a part of the above function. Further, it can also be a so-called difference file (difference program) that can realize the above function by combining with a program already recorded in the computer system. Explanation of Reference Signs

[0081] 1 steering wheel 2 steering shaft 4 steering angle sensor 5 torque sensor 6 motor 8 vehicle speed sensor 11 control unit 22 target steering torque setting section 23 torque feedback operation section 32 first torque operation section 33 second torque operation section 34, 35 mediation section 35a vehicle speed sensing gain map 36a first torque map 37a second torque map VE vehicle PS electric power steering device

Claims

1. A steering control device characterized by comprising: includes: a target steering torque setting section that sets a target steering torque for a steering system; and a steering torque control section that controls a steering assist torque required for the steering system to follow the target steering torque based on a deviation between the target steering torque and a steering torque acting on the steering system, the target steering torque setting section sets the target steering torque based on the steering torque and the steering assist torque at the time of parking, in a first vehicle speed region, the target steering torque is set based on the steering torque, the steering assist torque, a steering angle of the steering system, and a vehicle speed, in a second vehicle speed region, the target steering torque is set based on the steering angle and the vehicle speed.

2. The steering control device according to claim 1, wherein the target steering torque setting section includes: a first torque calculation section that calculates a first torque based on a sum of the steering torque and the steering assist torque; a second torque calculation section that calculates a second torque based on the steering angle and the vehicle speed; and a mediation section that calculates the first torque as the target steering torque at the time of parking, and calculates the target steering torque based on the first torque, the second torque, and the vehicle speed in cases other than at the time of parking.

3. The steering control device according to claim 2, wherein the first torque calculated by the first torque calculation section is a characteristic that gradually increases as the absolute value of the sum of the steering torque and the steering assist torque increases.

4. The steering control device according to claim 2 or 3, wherein the second torque calculated by the second torque calculation section is a characteristic that does not decrease as the vehicle speed increases in the case where the absolute value of the steering angle is the same, and is a characteristic that does not decrease as the absolute value of the steering angle increases in the case where the vehicle speed is the same.

5. The steering control device according to any one of claims 2 to 4, wherein the mediation section has a vehicle speed sensing gain map that defines a vehicle speed sensing gain corresponding to the vehicle speed, multiplies the vehicle speed sensing gain and the first torque to calculate a mediated first torque, multiplies a value obtained by subtracting the vehicle speed sensing gain from 1 and the second torque to calculate a mediated second torque, adds the mediated first torque and the mediated second torque to calculate the target steering torque, the vehicle speed sensing gain map defines the vehicle speed sensing gain such that the mediated second torque becomes 0 at the time of parking, in the second vehicle speed region, the vehicle speed sensing gain is defined such that the mediated first torque becomes 0.

6. The steering control device according to claim 5, wherein the vehicle speed sensing gain map is defined such that the vehicle speed sensing gain continuously changes according to the vehicle speed.

7. The steering control device according to claim 1, wherein the target steering torque setting section includes: a first torque map that defines a relationship between the vehicle speed, a road reaction force estimation value, and a first map torque; and a second torque map that defines a relationship between the vehicle speed, the steering angle, and a second map torque, a first map torque is calculated with reference to the first torque map, based on the road reaction force estimation value and the vehicle speed obtained from the sum of the steering torque and the steering assist torque, a second map torque is calculated with reference to the second torque map, based on the steering angle and the vehicle speed, the target steering torque is calculated by adding the first map torque and the second map torque, the second torque map is defined so that the second map torque becomes 0 at the time of parking, the first torque map is set so that the first map torque becomes 0 in the second vehicle speed region.

8. The steering control device according to claim 7, wherein the first torque map is of a characteristic that, in the case where the sum of the steering torque and the steering assist torque is the same, the first map torque does not increase as the vehicle speed becomes higher, and, in the case where the vehicle speed is the same, the first map torque does not decrease as the absolute value of the sum of the steering torque and the steering assist torque becomes larger.

9. The steering control device according to claim 7 or 8, wherein the second torque map is of a characteristic that, in the case where the absolute value of the steering angle is the same, the second map torque does not decrease as the vehicle speed becomes higher, and, in the case where the vehicle speed is the same, the second map torque does not decrease as the absolute value of the steering angle becomes larger.

10. An electric power steering apparatus characterized by comprising: including: a steering torque detection section that detects a steering torque acting on a steering system; a steering state detection section that detects a steering angle of the steering system; an electric motor that provides a steering assist torque to the steering system; and the steering control device according to any one of claims 1 to 9, which controls driving of the electric motor based on the detected steering torque and the steering angle. including:

11. A vehicle characterized by comprising: a vehicle speed detection section that detects a speed of a vehicle; and the electric power steering device according to claim 10, which controls the steering assist torque provided to the steering system based on the vehicle speed detected by the vehicle speed detection section. ​ ​

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