Steering control device, electric power steering device, and vehicle

Abstract

A steering control device (11) is provided with: a target steering torque setting section (22) that sets a target steering torque for a steering system; and a steering torque control section (23) that controls, on the basis of a deviation between the target steering torque and steering torque acting on the steering system, steering auxiliary torque necessary for causing the steering torque to follow the target steering torque. The target steering torque setting section: sets, when the vehicle is stopped, the target steering torque on the basis of the steering torque and the steering auxiliary torque; sets, in the first vehicle speed range, the target steering torque on the basis of the steering torque, the steering auxiliary torque, the steering angle of the steering system, and the vehicle speed; and sets, in the second vehicle speed range, the target steering torque on the basis of the steering angle and the vehicle speed.

Description

Steering control device, electric power steering device, and vehicle

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

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

[0003] The following Patent Document 1 discloses an electric power steering device that can easily achieve an equivalent steering torque in response to vehicle driving information such as steering angle, without being affected by changes in mechanical characteristics due to road surface conditions or aging deterioration of the steering mechanism. This electric power steering device generates a target steering torque based on the vehicle driving information, converts the generated target steering torque into a target torsional angle, calculates a target torsional angular velocity according to the deviation between the target torsional angle and the detected torsional angle, and controls the torsional angular velocity to follow the target torsional angular velocity.

[0004] Patent Document 2 below discloses an electric power steering device that realizes a torque feedback system with a simple configuration, without adopting a configuration in which the target steering torque is determined based on the steering angle and vehicle speed. This electric power steering device calculates the output torque as the sum of the detected torque and the assist torque, and obtains the target steering torque from the output torque based on predetermined output torque-target steering torque relationship information.

[0005] Patent No. 6504322 Patent No. 4161707

[0006] The electric power steering device disclosed in the above-mentioned Patent Document 1 calculates the target steering torque using a basic map, a damper component, and a hysteresis component. Therefore, when the vehicle speed is 0 km / h (stopped) and the steering angle is other than 0 degrees (neutral position), if the driver releases his or her hands from the steering wheel, the steering wheel attempts to return to the neutral position, resulting in an unintended behavior by the driver. Furthermore, even though the steering wheel stops moving when road friction is greater than or equal to the assist torque, the electric power steering device disclosed in the above-mentioned Patent Document 1 continues to output the target steering torque corresponding to the steering angle. Because the steering torque attempts to follow the target steering torque, current continues to flow, resulting in unnecessary power consumption. Furthermore, if the vehicle is left idling for a long period of time, the motor may overheat and enter an overheat protection state, potentially resulting in performance degradation.

[0007] In the electric power steering device disclosed in the above-mentioned Patent Document 2, the target steering torque is determined only by the output torque (the sum of the detected torque and the assist torque) acting on the wheel side. Therefore, when the road surface reaction torque is equal to or less than the mechanism friction torque, the target steering torque becomes 0, and no assist torque acting on the side returning the steering wheel is generated. In other words, the driver must apply torque to the steering wheel to return the steering wheel, which poses a problem of a deterioration in steering feel.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a steering control device, an electric power steering device, and a vehicle that can prevent unnecessary current consumption when the vehicle is stopped and a deterioration in steering feel when driving, which occur when the characteristics of the required target steering torque differ depending on the vehicle speed.

[0009] In order to solve the above problem, a steering control device according to one aspect of the present disclosure includes a target steering torque setting unit that sets a target steering torque for a steering system, and a steering torque control unit that controls a steering assist torque required to make the steering torque follow the target steering torque based on a deviation between the target steering torque and the steering torque acting on the steering system, wherein the target steering torque setting unit sets the target steering torque based on the steering torque and the steering assist torque when the vehicle is stopped, sets the target steering torque based on the steering torque, the steering assist torque, the steering angle of the steering system, and the vehicle speed in a first vehicle speed range, and sets the target steering torque based on the steering angle and the vehicle speed in a second vehicle speed range.

[0010] Furthermore, a power steering device according to one aspect of the present disclosure includes a steering torque detection unit that detects a steering torque acting on a steering system, a steering state detection unit that detects a steering angle of the steering system, a motor that applies a steering assist torque to the steering system, and the above-mentioned steering control device that controls the drive of the motor based on the detected steering torque and steering angle.

[0011] Furthermore, a vehicle according to one aspect of the present disclosure includes a vehicle speed detection unit that detects the speed of the vehicle, and the above-mentioned electric power steering device that controls the steering assist torque applied to the steering system based on the vehicle speed detected by the vehicle speed detection unit.

[0012] According to the present disclosure, it is possible to prevent unnecessary current consumption when the vehicle is stopped and deterioration of steering feel when the vehicle is traveling, which occur when the characteristics of the required target steering torque differ depending on the vehicle speed.

[0013] FIG. 1 is a block diagram showing a configuration of a main part of an electric power steering device and a vehicle according to a first embodiment of the present disclosure. FIG. 2 is a block diagram showing a configuration of a main part of a control unit as a steering control device according to the first embodiment of the present disclosure. FIG. 3 is a block diagram showing an internal configuration of a target steering torque setting unit according to the first embodiment of the present disclosure. FIG. 4 is a block diagram showing an example configuration of a first torque calculation unit according to the first embodiment of the present disclosure. FIG. 5 is a block diagram showing another example configuration of the first torque calculation unit according to the first embodiment of the present disclosure. FIG. 6 is a block diagram showing an example configuration of a second torque calculation unit according to the first embodiment of the present disclosure. FIG. 7 is a block diagram showing another example configuration of the second torque calculation unit according to the first embodiment of the present disclosure. FIG. 8 is a block diagram showing an example characteristic of a second torque calculation unit according to the first embodiment of the present disclosure. FIG. 10 is a block diagram showing an example configuration of a first map torque calculation unit in accordance with a third embodiment of the present disclosure. FIG. 11 is a block diagram showing another example configuration of a first map torque calculation unit in accordance with the third embodiment of the present disclosure. FIG. 12 is a block diagram showing another example configuration of a second map torque calculation unit in accordance with the third embodiment of the present disclosure. FIG. 13 is a diagram showing an example configuration of a first torque map and a second torque map in accordance with the third embodiment of the present disclosure.

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

[0015] [Embodiment 1] <Electric Power Steering Device and Vehicle> Figure 1 is a block diagram showing the configuration of essential parts of an electric power steering device and a vehicle according to embodiment 1 of the present disclosure. As shown in Figure 1, a vehicle VE according to this embodiment includes a vehicle speed sensor 8 (vehicle speed detection unit) and an electric power steering device PS. The electric power steering device PS includes a steering wheel 1, a steering shaft 2, steered wheels 3, a steering angle sensor 4 (steering state detection unit), a torque sensor 5 (steering torque detection unit), a motor 6, a reduction gear 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 handle, and is operated by the driver of the vehicle VE to apply a steering angle to the steered wheels 3 of the vehicle VE. The steering shaft 2 is connected to the steering wheel 1 and rotates in response to the rotation of the steering wheel 1. The steered wheels 3 are provided on both the left and right sides of the vehicle VE and are steered in response to the rotation of the steering shaft 2. The mechanism for steering the steered wheels 3, including the steering wheel 1 and the steering shaft 2, will be referred to as the "steering (steering system)."

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

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

[0019] <Steering Control Device> Figure 2 is a block diagram showing the configuration of a main part of a control unit serving as a steering control device according to embodiment 1 of the present disclosure. As shown in Figure 2, control unit 11 includes a control unit 12 and a current driver 13. Control unit 12 includes a differentiator 21a, a target steering torque setting unit 22, a torque feedback calculator 23 (steering torque controller), and a multiplier 24.

[0020] The differentiator 21a differentiates the rotation angle of the motor 6 detected by the motor rotation angle sensor 10 to calculate the rotation angular velocity of the motor 6 (hereinafter referred to as the "motor rotation angular velocity"). The differentiator 21a, together with the motor rotation angle sensor 10, constitutes a motor rotation angular velocity detection unit 21 that detects the motor rotation angular velocity.

[0021] The target steering torque setting unit 22 sets a target steering torque for the steering. 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 a steering assist torque (details will be described later) output from a multiplier 24 are input to the target steering torque setting unit 22. The target steering torque setting unit 22 sets a target steering torque for the steering using these detection results, etc. The target steering torque setting unit 22 will be described in detail later.

[0022] The torque feedback calculation unit 23 receives as input the steering torque detected by the torque sensor 5, the motor rotational angular velocity detected by the motor rotational angular velocity detection unit 21, and the target steering torque set by the target steering torque setting unit 22. The torque feedback calculation unit 23 calculates a target steering assist torque required to make the steering torque follow the target steering torque, based on the deviation between the target steering torque and the steering torque and the motor rotational angular velocity. Details of the torque feedback calculation unit 23 will be described later.

[0023] The multiplier 24 obtains the steering assist torque by multiplying the current flowing through the motor 6, detected by the current sensor 9, by a predetermined torque constant Kt. Specifically, if the current flowing through the motor 6 is I, the multiplier 24 performs the calculation shown in the following (1) to obtain the steering assist torque Tmotor. The torque constant Kt is set to a value that also takes into consideration the reduction ratio of the reduction mechanism 7. Tmotor=I×Kt (1)

[0024] The control unit 12 of the control unit 11 is realized by a microcomputer including a CPU (Central Processing Unit) and a memory. The memory provided in the microcomputer may include both volatile and non-volatile memory. The current driver 13 is realized by an analog circuit including multiple switching elements such as FETs (Field Effect Transistors).

[0025] Here, an outline of the operation of the control unit 11, which is a main part of the electric power steering device PS, will be explained. The operation explained below is repeated at a predetermined control cycle.

[0026] First, the control unit 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 21a of the control unit 12 differentiates the motor rotation angle detected by the motor rotation angle sensor 10 to determine the motor rotation angular velocity. Furthermore, the multiplier 24 of the control unit 12 multiplies the current I flowing through the motor 6, detected by the current sensor 9, by the torque constant Kt to determine the steering assist torque, as shown in the above-mentioned equation (1).

[0027] Next, a target steering torque setting unit 22 of the control unit 12 sets a 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 calculated by the multiplier 24. Next, a torque feedback calculation unit 23 of the control unit 12 calculates a 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 unit 22 and the steering torque detected by the torque sensor 5, and the motor rotational angular velocity calculated by the differentiator 21 a. Next, a current drive unit 13 of the control unit 11 controls the current flowing through the motor 6 to generate the target steering assist torque calculated by the torque feedback calculation unit 23 in the steering.

[0028] 3 is a block diagram illustrating an internal configuration of a target steering torque setting unit according to the first embodiment of the present disclosure. As shown in FIG. 3, the target steering torque setting unit 22 includes an adder 31, a first torque calculation unit 32, a second torque calculation unit 33, and an arbitration unit 34.

[0029] The adder 31 calculates an estimated road surface reaction force by adding the steering torque detected by the torque sensor 5 and the steering assist torque calculated by the multiplier 24. Here, the estimated road surface reaction force calculated by the adder 31 is the torque acting on the steering shaft 2 due to the turning of the wheels by the steering wheel, and can be treated as equivalent to the road surface reaction torque generated in the steered wheels 3.

[0030] This road surface reaction force estimated value can be calculated without directly sensing the road surface reaction torque actually generated on the steered wheels 3. Specifically, if the steering torque detected by the torque sensor 5 is Tsens, the road surface reaction force estimated value Test can be calculated using the following commonly known equation (2): Test=Tsens+Tmotor (2)

[0031] Based on the above equation (2), in the configuration shown in FIG. 3, the steering torque Tsens detected by the torque sensor 5 and the steering assist torque Tmotor calculated by the multiplier 24 are added together by the adder 31 to calculate the road surface reaction force estimated value.

[0032] The first torque calculation unit 32 calculates the first torque based on the road surface reaction force estimated value calculated by the adder 31. Fig. 4A is a block diagram showing an example configuration of the first torque calculation unit according to the first embodiment of the present disclosure. The first torque calculation unit 32 shown in Fig. 4A includes a first torque calculation unit 32a, a sign determination unit 32b, and a multiplier 32c.

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

[0034] 5 is a diagram illustrating an example of the characteristic of the first torque calculated by the first torque calculation unit 32 according to the first embodiment of the present disclosure. As shown in FIG. 5, the first torque calculated by the first torque calculation unit 32 has a characteristic (including a flat shape) that gradually increases as the absolute value of the road surface reaction force estimated value increases. Furthermore, the first torque only takes positive values.

[0035] Fig. 4B is a block diagram showing another example configuration of the first torque calculation unit according to the first embodiment of the present disclosure. The first torque calculation unit 32 shown in Fig. 4B is configured such that the sign determination unit 32b and the multiplier 32c are omitted from the first torque calculation unit 32 shown in Fig. 4A, and only a first torque calculation unit 32a is included. The first torque calculation unit 32 shown in Fig. 4B calculates a first torque that is positive or negative depending on the sign of the road surface reaction force estimated value.

[0036] Second torque calculation unit 33 calculates the second torque based on the vehicle speed detected by vehicle speed sensor 8 and the steering angle detected by steering angle sensor 4. Fig. 6A is a block diagram showing an example configuration of the second torque calculation unit according to the first embodiment of the present disclosure. Second torque calculation unit 33 shown in Fig. 6A includes a second torque map 33a, a sign determination unit 33b, and a multiplier 32c.

[0037] The second torque map 33a is a map that defines the relationship between the vehicle speed, the steering angle, and the second torque. When the vehicle speed and the steering angle are input, the second torque map 33a outputs a second torque that corresponds to the vehicle speed and the steering angle. The sign determination unit 33b determines the sign of the input steering angle, and outputs "+1" if the sign is positive, and outputs "-1" if the sign is negative. The multiplier 33c multiplies the second torque output from the second torque map 33a by the value output from the sign determination unit 33b.

[0038] 7 is a diagram illustrating an example of the characteristic of the second torque calculated by the second torque calculation unit according to the first embodiment of the present disclosure. As shown in FIG. 7 , the second torque calculated by the second torque calculation unit 33 has a characteristic (including a flat shape) that does not decrease as the vehicle speed increases when the absolute value of the steering angle is constant, and also has a characteristic (including a flat shape) that does not decrease as the absolute value of the steering angle increases when the vehicle speed is constant. Furthermore, the second torque only takes positive values.

[0039] Fig. 6B is a block diagram showing another example configuration of the second torque calculator according to the first embodiment of the present disclosure. The second torque calculator 33 shown in Fig. 6B is configured such that the sign determination unit 33b and the multiplier 33c are omitted from the second torque calculator 33 shown in Fig. 6A and only the second torque map 33a is included. The second torque calculator 33 shown in Fig. 6B calculates a second torque that is positive or negative depending on the sign of the steering angle.

[0040] The arbitration unit 34 outputs a target steering torque based on the vehicle speed detected by the vehicle speed sensor 8, the first torque calculated by the first torque calculation unit 32, and the second torque calculated by the second torque calculation unit 33. The target steering torque output by the arbitration unit 34 is appropriate for each vehicle speed range. Fig. 8 is a diagram for describing an example of the operation of the arbitration unit when the vehicle speed is changed when the steering angle is not at the neutral position in the first embodiment of the present disclosure.

[0041] As shown in FIG. 8 , vehicle speed ranges are divided into a stopped state (vehicle speed 0) and a boundary vehicle speed V1. The vehicle speed range where the vehicle speed is "0 < vehicle speed < V1" is defined as a "first vehicle speed range," and the vehicle speed range where the vehicle speed is "V1 ≦ vehicle speed" is defined as a "second vehicle speed range." As shown in FIG. 8 , the arbitration unit 34 outputs a target steering torque that matches the first torque when the vehicle is stopped, matches the second torque at boundary vehicle speed V1, and is an intermediate value between the first torque and the second torque in between (first vehicle speed range) and does not cause discontinuity depending on the vehicle speed. It can also be said that the arbitration unit 34 calculates the first torque as the target steering torque when the vehicle is stopped, and calculates the target steering torque based on the first torque, the second torque, and the vehicle speed when the vehicle is not stopped.

[0042] Here, the first torque is a torque calculated from an estimated road surface reaction force, which is the sum of the steering torque and the steering assist torque, and the second torque is a torque calculated from the steering angle and the vehicle speed. Therefore, when the vehicle is stopped, the target steering torque setting unit 22 can be said to set the target steering torque based on the steering torque and the steering assist torque. Also, in the first vehicle speed range, the target steering torque can be said to be set based on the steering torque, the steering assist torque, the steering angle of the steering system, and the vehicle speed. Also, in the second vehicle speed range, the target steering torque can be said to be set based on the steering angle and the vehicle speed.

[0043] 9 is a block diagram showing an example of the internal configuration of the torque feedback calculation unit according to the first embodiment of the present disclosure. As shown in FIG. 9 , the torque feedback calculation unit 23 includes a subtractor 41, a first target steering assist torque calculation unit 42, a second target steering assist torque calculation unit 43, a third target steering assist torque calculation unit 44, and an adder 45.

[0044] The subtractor 41 calculates the deviation between the target steering torque and the steering torque. The first target steering assist torque calculation unit 42 has an integrator 42a and an amplifier 42b, and calculates the first target steering assist torque by integrating the deviation calculated by the subtractor 41 and then multiplying it by an integral control gain KTI. The second target steering assist torque calculation unit 43 has an amplifier 43a, and calculates the second target steering assist torque by multiplying the motor rotational angular velocity by a speed control gain KTV.

[0045] The third target steering assist torque calculation unit 44 includes an amplifier 44a, and calculates a third target steering assist torque by multiplying the deviation calculated by the subtractor 41 by a proportional control gain KTP. An adder 45 adds the first target steering assist torque, the second target steering assist torque, and the third target steering assist torque to obtain a target steering assist torque. Note that the torque feedback calculation unit 23 is not limited to the configuration shown in Fig. 9, and any configuration may be used as long as it has a function of making the steering torque follow the target steering torque.

[0046] In this embodiment, the target steering torque setting unit 22 sets an appropriate target steering torque for each vehicle speed range, and the torque feedback calculation unit 23 controls the target steering assist torque so that the driver's steering torque follows the target steering torque. This allows the driver to steer with an appropriate torque.

[0047] In this embodiment, since the first torque is calculated based on the estimated road surface reaction force, even if the driver releases his / her hands from the steering wheel 1 when the steering angle is at a position other than 0 degrees, the target steering torque becomes "0" at the position where the estimated road surface reaction force becomes "0". Note that the position where the estimated road surface reaction force becomes "0" is a position where there is a balance with the mechanism friction torque, and is not limited to the neutral position of the steering wheel 1. When the driver releases his / her hands from the steering wheel 1, the steering torque becomes "0", so there is no deviation between the target steering torque and the steering torque, and it is possible to reduce unnecessary current consumption when the vehicle is stopped.

[0048] In this embodiment, an arbitration unit 34 is provided to continuously transition the target steering torque from the first torque to the second torque. In the second vehicle speed range, the second torque is calculated based on the steering angle and the vehicle speed, so the target steering torque is set in a direction to return the steering wheel 1 to the neutral position when the steering wheel 1 is not in the neutral position. As a result, in the second vehicle speed range, when the driver has his / her hands off the steering wheel 1 (steering torque is "0"), the steering wheel 1 is returned to the neutral position, preventing a deterioration in the steering feeling.

[0049] In the above-described embodiment, the target steering torque when the vehicle is stopped is the first torque alone (100% first torque). However, the present invention also includes a case where the target steering torque is substantially the first torque, such as when the ratio of the first torque to the second torque is 99:1. Furthermore, information indicating the motor rotational angular velocity or the like may be input to the target steering torque setting unit 22 to calculate the target steering torque. By inputting information indicating the motor rotational angular velocity or the like, the target steering torque can be flexibly set based on this additional information, thereby making it possible to improve convergence and provide a sense of friction.

[0050] Furthermore, in this embodiment, the 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, instead of the detection result of the steering angle sensor 4, the motor rotation angle detected by the motor rotation angle sensor 10 may be converted into a steering angle and used. For example, the motor rotation angle detected by the motor rotation angle sensor 10 may be converted into the angle of the steering shaft 2 using the reduction ratio of the reduction mechanism 7 and used. Furthermore, when the motor rotation angle is a relative angle with respect to the angle of the steering shaft 2, a yaw rate sensor or the like (not shown) provided in the vehicle VE may be used to determine that the vehicle is traveling straight ahead, and the relative angle may be offset to zero and used as the absolute angle of the steering shaft 2.

[0051] [Embodiment 2] <Electric power steering device and vehicle> The configurations of the electric power steering device and vehicle according to this embodiment are basically the same as the configurations of the electric power steering device PS and vehicle VE shown in Fig. 1. Therefore, detailed descriptions of the electric power steering device and vehicle according to this embodiment will be omitted.

[0052] <Steering Control Device> The basic configuration 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 configuration of the target steering torque setting unit 22 provided in the control unit 11 is different. The target steering torque setting unit 22 will be described in detail below.

[0053] 10 is a block diagram showing an internal configuration of a target steering torque setting unit according to the second embodiment of the present disclosure. As shown in Fig. 10, target steering torque setting unit 22 according to the present embodiment includes an adder 31, a first torque calculation unit 32, a second torque calculation unit 33, and an arbitration unit 35. That is, target steering torque setting unit 22 according to the present embodiment has a configuration in which arbitration unit 34 of target steering torque setting unit 22 shown in Fig. 3 is replaced with arbitration unit 35.

[0054] The arbitration unit 35 includes a vehicle speed sensitive gain map 35a, a multiplier 35b, a subtractor 35c, a multiplier 35d, and an adder 35e. The vehicle speed sensitive gain map 35a is a map in which a vehicle speed sensitive gain corresponding to the vehicle speed is defined. When a vehicle speed is input to the vehicle speed sensitive gain map 35a, a vehicle speed sensitive gain corresponding to the vehicle speed is output from the vehicle speed sensitive gain map 35a.

[0055] FIG. 11 is a diagram illustrating an example of a vehicle speed sensitive gain map according to the second embodiment of the present disclosure. As shown in FIG. 11 , vehicle speed sensitive gain map 35a is a map having a characteristic in which the vehicle speed sensitive gain changes continuously depending on the vehicle speed. The vehicle speed sensitive gain defined by vehicle speed sensitive gain map 35a takes values ​​between "0" and "1." Vehicle speed sensitive gain map 35a shown in FIG. 11 has a value of "1" when the vehicle is stopped, gradually decreases as the vehicle speed increases in a first vehicle speed range, and reaches "0" in a second vehicle speed range.

[0056] The multiplier 35b multiplies the first torque calculated by the first torque calculation unit 32 by the vehicle speed sensitive gain output from the vehicle speed sensitive gain map 35a to calculate the arbitrated first torque. The subtractor 35c subtracts the vehicle speed sensitive gain output from the vehicle speed sensitive gain map 35a from the value "1". The multiplier 35d multiplies the second torque calculated by the second torque calculation unit 33 by the value output from the subtractor 35c to calculate the arbitrated second torque. The adder 35e adds the arbitrated first torque calculated by the multiplier 35b and the arbitrated second torque calculated by the multiplier 35d to calculate the target steering torque.

[0057] Here, as described above, the arbitrated first torque is calculated by multiplying the first torque by the vehicle speed sensitive gain. In contrast, the arbitrated second torque is calculated by multiplying the second torque by a value obtained by subtracting the vehicle speed sensitive gain from the value "1." As shown in FIG. 11 , when the vehicle is stopped, the value of the vehicle speed sensitive gain is "1," so the arbitrated second torque is "0." Furthermore, in the second vehicle speed range, the value of the vehicle speed sensitive gain is "0," so the arbitrated first torque is "0." Therefore, it can be said that the vehicle speed sensitive gain map 35a defines the vehicle speed sensitive gain so that the arbitrated second torque is "0" when the vehicle is stopped, and defines the vehicle speed sensitive gain so that the arbitrated first torque is "0" in the second vehicle speed range.

[0058] Since the value of the vehicle speed sensitive gain is "1" when the vehicle is stopped, the first torque is set as the target steering torque when the vehicle is stopped. Since the value of the vehicle speed sensitive gain in the first vehicle speed range is a value between "0" and "1", an intermediate value between the first torque and the second torque is set as the target steering torque in the first vehicle speed range. Since the value of the vehicle speed sensitive gain in the second vehicle speed range is "0", the second torque is set as the target steering torque in the second vehicle speed range. In other words, in this embodiment, the target steering torque set by target steering torque setting unit 22 is similar to that shown in FIG. 8.

[0059] As described above, in this embodiment as well, the first torque is calculated based on the road surface reaction force estimated value, and the target steering torque is continuously shifted from the first torque to the second torque by providing the arbitration unit 35. This makes it possible to reduce unnecessary current consumption when the vehicle is stopped, as in the first embodiment, and to prevent a deterioration in steering feeling.

[0060] 10 is configured to calculate the second torque after arbitration by multiplying the value obtained by subtracting the vehicle speed sensitive gain output from the vehicle speed sensitive gain map 35a from the value "1" by the second torque calculated by the second torque calculation unit 33. However, a vehicle speed sensitive gain map may be provided in addition to the vehicle speed sensitive gain map 35a, in which the vehicle speed sensitive gain at each vehicle speed in the vehicle speed sensitive gain map 35a is subtracted from the value "1", and the second torque after arbitration may be calculated by multiplying the vehicle speed sensitive gain output from this vehicle speed sensitive gain map by the second torque calculated by the second torque calculation unit 33.

[0061] [Embodiment 3] <Electric power steering device and vehicle> The configurations of the electric power steering device and vehicle according to this embodiment are basically the same as the configurations of the electric power steering device PS and vehicle VE shown in Fig. 1. Therefore, detailed descriptions of the electric power steering device and vehicle according to this embodiment will be omitted.

[0062] <Steering Control Device> The basic configuration 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 configuration of the target steering torque setting unit 22 provided in the control unit 11 is different. The target steering torque setting unit 22 will be described in detail below.

[0063] 12 is a block diagram showing the internal configuration of a target steering torque setting unit according to a third embodiment of the present disclosure. As shown in Fig. 12, the target steering torque setting unit 22 according to the present embodiment includes an adder 31, a first map torque calculation unit 36, a second map torque calculation unit 37, and an adder 38. That is, the target steering torque setting unit 22 according to the present embodiment has a configuration in which the first torque calculation unit 32, the second torque calculation unit 33, and the arbitration unit 34 of the target steering torque setting unit 22 shown in Fig. 3 are replaced with the first map torque calculation unit 36, the second map torque calculation unit 37, and the adder 38.

[0064] The first map torque calculation unit 36 ​​calculates the first map torque based on the road surface reaction force estimated value calculated by the adder 31 and the vehicle speed detected by the vehicle speed sensor 8. Fig. 13A is a block diagram showing an example configuration of the first map torque calculation unit according to the third embodiment of the present disclosure. The first map torque calculation unit 36 ​​shown in Fig. 13A includes a first torque map 36a, a sign determination unit 36b, and a multiplier 36c.

[0065] The first torque map 36a is a map that defines the relationship between vehicle speed, estimated road reaction force, and first map torque. When the vehicle speed and estimated road reaction force are input to the first torque map 36a, the first torque map 36a outputs a first map torque that corresponds to the vehicle speed and estimated road reaction force. The sign determination unit 36b determines the sign of the input estimated road reaction force, and outputs "+1" if the sign is positive, and outputs "-1" if the sign is negative. The multiplier 36c multiplies the first map torque output from the first torque map 36a by the value output from the sign determination unit 36b.

[0066] The second map torque calculation unit 37 calculates the second map torque based on the vehicle speed detected by the vehicle speed sensor 8 and the steering angle detected by the steering angle sensor 4. Fig. 14A is a block diagram showing an example configuration of the second map torque calculation unit according to the third embodiment of the present disclosure. The second map torque calculation unit 37 shown in Fig. 14A includes a second torque map 37a, a sign determination unit 37b, and a multiplier 37c.

[0067] The second torque map 37a is a map that defines the relationship between vehicle speed, steering angle, and second map torque. When the vehicle speed and steering angle are input, the second torque map 37a outputs a second map torque that corresponds to the vehicle speed and steering angle. The sign determination unit 37b determines the sign of the input steering angle, and outputs "+1" if the sign is positive, and outputs "-1" if the sign is negative. The multiplier 37c multiplies the second map torque output from the second torque map 37a by the value output from the sign determination unit 37b.

[0068] 15 is a diagram illustrating an example of a first torque map and a second torque map according to the third embodiment of the present disclosure. As shown in Fig. 15, a first torque map 36a and a second torque map 37a are provided for a vehicle stopped state, a first vehicle speed range, and a second vehicle speed range.

[0069] The first torque map 36a when the vehicle is stopped has a characteristic (including a flat shape) in which the first map torque gradually increases as the absolute value of the road surface reaction force estimated value increases. The first torque map 36a in the first vehicle speed range has a characteristic (including a flat shape) in which the first map torque does not increase as the vehicle speed increases when the absolute value of the road surface reaction force estimated value is constant, and has a characteristic (including a flat shape) in which the first map torque does not decrease as the absolute value of the road surface reaction force estimated value increases when the vehicle speed is constant. The first torque map 36a in the second vehicle speed range is specified so that the first map torque is 0. Note that the first map torque takes only positive values.

[0070] The second torque map 37a when the vehicle is stopped is specified so that the second map torque is 0. The second torque map 37a in the first vehicle speed range and the second vehicle speed range has a characteristic (including a flat shape) in which the second map torque does not decrease as the vehicle speed increases when the absolute value of the steering angle is the same, and a characteristic (including a flat shape) in which the second map torque does not decrease as the absolute value of the steering angle increases when the vehicle speed is the same. Note that the second map torque only takes positive values.

[0071] Fig. 13B is a block diagram showing another example configuration of the first map torque calculation unit in the third embodiment of the present disclosure. The first map torque calculation unit 36 ​​shown in Fig. 13B is configured such that the sign determination unit 36b and the multiplier 36c are omitted from the first map torque calculation unit 36 ​​shown in Fig. 13A and only the first torque map 36a is included. The first map torque calculation unit 36 ​​shown in Fig. 14B calculates a first map torque that is positive or negative depending on the sign of the road surface reaction force estimated value.

[0072] Fig. 14B is a block diagram showing another example configuration of the second map torque calculator according to the third embodiment of the present disclosure. The second map torque calculator 37 shown in Fig. 6B is configured such that the sign determination unit 37b and the multiplier 37c are omitted from the second map torque calculator 37 shown in Fig. 14A and only the second torque map 37a is provided. The second map torque calculator 37 shown in Fig. 14B determines a second map torque that is positive or negative depending on the sign of the steering angle.

[0073] The adder 38 adds the first map torque calculated by the first map torque calculation section 36 and the second map torque calculated by the second map torque calculation section 37 together to calculate the target steering torque.

[0074] Here, as shown in Figure 15, the second torque map 37a is defined so that the second map torque is 0 when the vehicle is stopped, and therefore the first map torque is set as the target steering torque when the vehicle is stopped. The first torque map 36a and the second torque map 37a in the first vehicle speed range have the characteristics shown in Figure 15, and therefore a target steering torque that is the sum of the first map torque and the second map torque and does not cause discontinuities depending on the vehicle speed is set in the first vehicle speed range. The first torque map 36a in the second speed range is defined so that the first map torque is 0, and therefore the second map torque is set as the target steering torque in the second vehicle speed range. Thus, in this embodiment as well, the target steering torque set by the target steering torque setting unit 22 is the same as that shown in Figure 8.

[0075] As described above, in this embodiment, the first map torque is calculated based on the estimated road surface reaction force, and the target steering torque is continuously shifted from the first map torque to the second map torque. As a result, as in the first embodiment, it is possible to reduce unnecessary current consumption when the vehicle is stopped, and to prevent a deterioration in the steering feel.

[0076] Furthermore, in the present embodiment, it can be said that the functions of the arbitration unit 34 in the first embodiment and the arbitration unit 35 in the second embodiment are inherent in the first torque map 36 a and the second torque map 37 a in advance. Therefore, in the present embodiment, the target steering torque can be set simply by calculating and adding the first map torque and the second map torque, which reduces the processing load on the control unit 12.

[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 modified without departing from the spirit of the present disclosure. For example, the electric power steering device PS described in the above-described embodiments may be of a column type or a rack-and-pinion type. Furthermore, in terms of performing feedback control based on a target steering torque, the present disclosure is also applicable to a steer-by-wire reaction force device that includes at least a torque sensor. Furthermore, the figures used in the description of the above-described embodiments show examples and are not limited to these.

[0078] The control unit 12 included in the control unit 11 has an internal computer system. A program for implementing the functions of the control unit 12 included in the control unit 11 may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform processing in each component included in the control unit 11. Here, "reading a program recorded on a recording medium into a computer system and executing it" includes installing the program into a computer system. The term "computer system" here includes hardware such as an OS and peripheral devices.

[0079] Furthermore, a "computer system" may include multiple computer devices connected via a network including the Internet or communication lines such as a WAN, LAN, or dedicated line. Furthermore, a "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Thus, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0080] The recording medium also includes internal or external recording media accessible from a distribution server for distributing the program. The program may be divided into multiple parts, downloaded at different times, and then combined by the components of the control unit 11. Each divided program may be distributed by a different distribution server. Furthermore, the term "computer-readable recording medium" also includes a medium that stores a program for a certain period of time, such as volatile memory (RAM) within a computer system that serves as a server or client when a program is transmitted over a network. The program may also be a medium for implementing part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-described functions in combination with a program already stored in the computer system.

[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 calculation section, 32...First torque calculation section, 33...Second torque calculation section, 34, 35...Arbitration section, 35a...Vehicle speed sensitive gain map, 36a...First torque map, 37a...Second torque map, VE...Vehicle, PS...Electric power steering device

Claims

1. A target steering torque setting unit that sets a target steering torque for a steering system, A steering torque control unit that controls a steering assist torque necessary to cause 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, Comprising, The target steering torque setting unit, When the vehicle is stopped, sets the target steering torque based on the steering torque and the steering assist torque, In the first vehicle speed range, sets the target steering torque based on the steering torque, the steering assist torque, the steering angle of the steering system, and the vehicle speed, In the second vehicle speed range, sets the target steering torque based on the steering angle and the vehicle speed, Steering control device.

2. The target steering torque setting unit, A first torque calculation unit that calculates a first torque based on the sum of the steering torque and the steering assist torque, A second torque calculation unit that calculates a second torque based on the steering angle and the vehicle speed, When the vehicle is stopped, calculates the first torque as the target steering torque, and when the vehicle is not stopped, calculates the target steering torque based on the first torque, the second torque, and the vehicle speed, The steering control device according to claim 1, comprising.

3. The first torque calculated by the first torque calculation unit has a characteristic of gradually increasing as the absolute value of the sum of the steering torque and the steering assist torque increases. The steering control device according to claim 2.

4. The second torque calculated by the second torque calculation unit has a characteristic that it does not decrease as the vehicle speed increases when the absolute value of the steering angle is the same, and does not decrease as the absolute value of the steering angle increases when the vehicle speed is the same. The steering control device according to claim 2.

5. The arbitration unit, Comprises a vehicle speed sensitive gain map in which a vehicle speed sensitive gain corresponding to the vehicle speed is defined, Multiplies the vehicle speed sensitive gain and the first torque to calculate an arbitration first torque, Multiplies the value obtained by subtracting the vehicle speed sensitive gain from 1 and the second torque to calculate an arbitration second torque, Calculates the target steering torque by adding the arbitration first torque and the arbitration second torque, The vehicle speed sensitive gain map, When the vehicle is stopped, the vehicle speed sensitive gain is defined so that the arbitration second torque becomes 0, In the second vehicle speed range, the vehicle speed sensitive gain is defined so that the arbitration first torque becomes 0. The steering control device according to claim 2.

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

7. The target steering torque setting unit a first torque map defining the relationship between the vehicle speed, the estimated road surface reaction force, and the first map torque; a second torque map defining the relationship between the vehicle speed, the steering angle, and the second map torque; and comprises referencing the first torque map, obtaining a first map torque based on the estimated road surface reaction force obtained from the sum of the steering torque and the steering assist torque and the vehicle speed, referencing the second torque map, obtaining a second map torque based on the steering angle and the vehicle speed, calculating the target steering torque by adding the first map torque and the second map torque, the second torque map is defined such that the second map torque becomes zero at the time of stopping, the first torque map is set such that the first map torque becomes zero in the second vehicle speed range, The steering control device according to claim 1.

8. The steering control device according to claim 7, wherein the first torque map has a characteristic that when 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 increases, and when 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 increases.

9. The steering control device according to claim 7, wherein the second torque map has a characteristic that when the absolute value of the steering angle is the same, the second map torque does not decrease as the vehicle speed increases, and when the vehicle speed is the same, the second map torque does not decrease as the absolute value of the steering angle increases.

10. a steering torque detection unit that detects a steering torque acting on the steering system; a steering state detection unit that detects a steering angle of the steering system; a motor that applies a steering assist torque to the steering system; a steering control device according to any one of claims 1 to 9 that controls driving of the motor based on the detected steering torque and the steering angle; An electric power steering device comprising

11. a vehicle speed detection unit that detects the speed of the vehicle; The electric power steering apparatus according to claim 10, which controls the steering assist torque applied to the steering system based on the vehicle speed detected by the vehicle speed detection unit, A vehicle comprising the same.