Electric power steering device

Abstract

An electric power steering device according to the present disclosure includes an electric motor and a steering control device that controls driving of the electric motor. A steering control device includes a base assist current calculation unit that calculates a base assist current, a steering wheel return current calculation unit that calculates a return current for returning a steering member to a neutral position, and an adder that adds the base assist current and the return current. The steering wheel return current calculation unit includes a base return current calculation unit that calculates a base return current, a return current correction value calculation unit that calculates a return current correction value that corrects the base return current, and a return current calculation unit that calculates a return current on the basis of the base return current and the return current correction value. A basic return current calculation unit calculates a basic return current on the basis of the difference between the target steering angular velocity and the steering angular velocity, and a return current correction value calculation unit determines a correction value on the basis of the steering angular velocity, and calculates a return current correction value by multiplying the correction value by a coefficient corresponding to the steering torque.

Description

Technical Field

[0001] This disclosure relates to electric power steering systems. Background Technology

[0002] Electric power steering systems include an electric motor that generates steering assist torque for the steering system of vehicles such as automobiles and a steering control device that controls the electric motor, thereby adding steering assist force to the vehicle's steering mechanism.

[0003] When a driver releases the steering wheel after operating it while the vehicle is in motion, the steering wheel returns to the neutral position based on the self-centering torque generated during vehicle movement. However, depending on the vehicle's construction, the steering wheel sometimes fails to return to the neutral position solely due to the self-centering torque. Patent documents 1-3 disclose an electric power steering device that performs steering wheel return-to-center control by using an electric motor to assist the steering wheel in returning to the neutral position.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-274662

[0007] Patent Document 2: Japanese Patent No. 4400544

[0008] Patent Document 3: Japanese Patent No. 3551147 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] Steering wheel return control may hinder the driver's steering. In Patent Document 1, when the steering torque applied to the steering system is large, the amount of steering wheel return control applied to the electric motor is reduced compared to when the steering torque is small. In Patent Document 2, as the absolute value of the steering torque applied to the steering system increases, the return torque used to assist the steering wheel in returning to the neutral position is reduced. Here, the electric power steering device performs feedback control based on the steering torque. In the constructions of Patent Documents 1 and 2, the increase or decrease in return torque causes changes in the characteristics of the torque feedback system, thus reducing the stability of the torque feedback system and causing vibration. To suppress the decrease in the stability of the torque feedback system, for example, a phase compensation filter can be considered. However, the phase compensation filter needs to be designed to balance both the driver's steering assistance and steering wheel return control, making adjustment difficult.

[0011] In Patent Document 3, as the steering angular velocity of the steering wheel increases, the return current used to return the steering wheel to the neutral position is reduced. The construction of Patent Document 3 is difficult to apply to steering wheel return control that uses speed feedback control, which determines the target steering angular velocity of the steering wheel and controls it to follow the target steering angular velocity.

[0012] Based on the above, the purpose of this disclosure is to provide an electric power steering device that, in a steering wheel return control system using speed feedback control, prevents the driver's steering from being hindered by the steering wheel return control.

[0013] Technical means for solving technical problems

[0014] One embodiment of the electric power steering device disclosed herein includes: a steering torque detection unit that detects the steering torque acting on the steering system of a vehicle; a steering angle detection unit that detects the steering angle of a steering member included in the steering system; a steering angular velocity detection unit that detects the steering angular velocity of the steering member; an electric motor that applies a steering assist torque to the steering system; and a steering control device that controls the drive of the electric motor, the steering control device including: a basic assist current calculation unit that calculates a basic assist current, i.e., a basic control quantity for assisting the steering of the vehicle, based on the steering torque; a steering wheel return current calculation unit that calculates a return current for returning the steering member to a neutral position; and an adder that adds the basic assist current to the return current, the steering wheel return current calculation unit including: a basic return current calculation unit that calculates a basic return current... The system comprises: a positive current calculation unit that calculates the basic value of the return current, i.e., the base return current, based on the steering angle; a return current correction value calculation unit that calculates a return current correction value to correct the base return current based on the steering angular velocity and the steering torque; and a return current calculation unit that calculates the return current based on the base return current and the return current correction value. The base return current calculation unit includes: a target steering angular velocity calculation unit that calculates the target steering angular velocity of the steering component based on the steering angle; and a return current feedback calculation unit that calculates the difference between the target steering angular velocity and the steering angular velocity, i.e., the steering angular velocity difference, and calculates the base return current based on the steering angular velocity difference. The return current correction value calculation unit determines the correction amount based on the steering angular velocity and multiplies the correction amount by a coefficient corresponding to the steering torque to calculate the return current correction value.

[0015] Invention Effects

[0016] According to this disclosure, an electric power steering device can be provided that, in a steering wheel return control using speed feedback control, prevents the driver's steering from being hindered by the steering wheel return control. Attached Figure Description

[0017] Figure 1 This is a block diagram showing the main structural components of the electric power steering system and vehicle according to Embodiment 1 of this disclosure.

[0018] Figure 2 This is a block diagram showing the main structure of the control unit, which is part of the steering control device according to Embodiment 1 of this disclosure.

[0019] Figure 3 This is a block diagram showing the internal structure of the basic auxiliary current calculation unit in Embodiment 1 of this disclosure.

[0020] Figure 4 This is a block diagram showing the internal structure of the steering wheel return current calculation unit in Embodiment 1 of this disclosure.

[0021] Figure 5A This is a block diagram showing the internal structure of the target steering angular velocity calculation unit in Embodiment 1 of this disclosure.

[0022] Figure 5B This is a block diagram illustrating other structural examples of the target steering angular velocity calculation unit in Embodiment 1 of this disclosure.

[0023] Figure 6A This is a block diagram showing the internal structure of the feedback current calculation unit in Embodiment 1 of this disclosure.

[0024] Figure 6B This is a block diagram illustrating other structural examples of the feedback current calculation unit in Embodiment 1 of this disclosure.

[0025] Figure 7A This is a block diagram showing the internal structure of the synchro current correction value calculation unit in Embodiment 1 of this disclosure.

[0026] Figure 7B This is a block diagram showing other structural examples of the synchro current correction value calculation unit in Embodiment 1 of this disclosure.

[0027] Figure 8 This is a block diagram showing the internal structure of the positive current calculation unit in Embodiment 2 of this disclosure.

[0028] Figure 9 This is a block diagram showing the internal structure of the synchro current correction value limiting unit in Embodiment 2 of this disclosure.

[0029] Figure 10This is a block diagram showing the internal structure of the return current limiting section in Embodiment 2 of this disclosure.

[0030] Figure 11 This is a block diagram showing the internal structure of the synchro current correction value calculation unit in Embodiment 3 of this disclosure.

[0031] Figure 12 This is a block diagram showing the internal structure of the torque coefficient limiting unit in Embodiment 3 of this disclosure. Detailed Implementation

[0032] Hereinafter, with reference to the accompanying drawings, a detailed description of the steering control device, electric power steering device, and vehicle according to embodiments of the present disclosure will be provided. Furthermore, in each embodiment, the same or equivalent parts are labeled with the same reference numerals, and repeated descriptions are omitted.

[0033] [Implementation Method 1]

[0034] <Electric power steering systems and vehicles>

[0035] Figure 1 This is a block diagram illustrating the main structural components of the electric power steering system and vehicle according to Embodiment 1 of this disclosure. Figure 1 As shown, the vehicle VE involved in this embodiment is equipped with an electric power steering system PS. The electric power steering system PS includes a steering wheel 1 (steering component), a steering shaft 2, a steering wheel 3, a steering angle sensor 4 (steering angle detection unit), a torque sensor 5 (steering torque detection unit), an electric motor 6, a reduction gear 7, a vehicle speed sensor 8 (vehicle speed detection unit), a current sensor 9, an electric motor rotation angle sensor 10, and a control unit 11 (steering control device). The electric power steering system PS in this embodiment is a column-assisted electric power steering system. Alternatively, the electric power steering system PS can also be a rack and pinion assisted electric power steering system.

[0036] The steering wheel 1 is the so-called steering wheel, operated by the driver of vehicle VE to provide a steering angle to the steering wheels 3 of vehicle VE. The steering shaft 2 is connected to the steering wheel 1 and rotates according to the rotation of the steering wheel 1. The steering wheels 3 are located on the left and right sides of vehicle VE and turn according to the rotation of the steering shaft 2. In addition, the mechanism that includes the steering wheel 1 and the steering shaft 2 and turns the steering wheels 3 is called the "steering gear (steering system)".

[0037] Steering angle sensor 4 is disposed on steering wheel 1 to detect the steering angle of steering wheel 1. Furthermore, the steering angle of steering wheel 1 is a state quantity related to the lateral movement of vehicle VE. Steering torque sensor 5 is disposed on steering shaft 2 to detect the steering torque acting on steering shaft 2. Electric motor 6 is connected to steering shaft 2 via reduction gear 7 to provide steering assist torque to steering shaft 2. Vehicle speed sensor 8 detects the vehicle speed of vehicle VE. Current sensor 9 detects the current flowing through electric motor 6. Electric motor rotation angle sensor 10 detects the rotation angle of electric motor 6.

[0038] The control unit 11 controls the drive of the electric motor 6 based on the detection results of the steering angle sensor 4, steering torque sensor 5, vehicle speed sensor 8, current sensor 9, and electric motor rotation angle sensor 10, in order to generate steering assist torque for the steering gear. Specifically, the control unit 11 calculates the target current required to generate the steering assist torque supplied to the steering shaft 2 based on the aforementioned detection results, and controls the current of the electric motor 6 based on this target current. The control unit 11 will be described in detail below.

[0039] <Steering Control Device>

[0040] Figure 2 This is a block diagram showing the main structural components of the control unit, which is part of the steering control device according to Embodiment 1 of this disclosure. Figure 2 As shown, the control unit 11 includes a control unit 12 and a current drive unit 13. The control unit 12 includes a differentiator 21a, a basic auxiliary current calculation unit 22, a steering wheel return current calculation unit 23, and an adder 24.

[0041] Differentiator 21a performs time differentiation on the rotation angle of motor 6 detected by motor rotation angle sensor 10 to calculate the rotational angular velocity of motor 6. Furthermore, differentiator 21a and motor rotation angle sensor 10 together constitute motor rotational angular velocity detection unit 21 for detecting the rotational angular velocity of motor 6. In this embodiment, the rotational angular velocity of motor 6 is used as the steering angular velocity of steering wheel 1. That is, motor rotational angular velocity detection unit 21 functions as steering angular velocity detection unit.

[0042] The steering torque detected by the steering torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 8 are input to the basic auxiliary current calculation unit 22. The basic auxiliary current calculation unit 22 uses these detection results to calculate the basic control quantity for steering of the assisted vehicle VE, namely the basic auxiliary current. Further details regarding the basic auxiliary current calculation unit 22 will be explained later.

[0043] The steering torque detected by the steering torque sensor 5, the steering angle detected by the steering angle sensor 4, the vehicle speed detected by the vehicle speed sensor 8, and the steering angular velocity calculated by the motor rotational angular velocity detection unit 21 are input to the steering wheel return current calculation unit 23. The steering wheel return current calculation unit 23 uses these detection results to calculate the return current used to return the steering wheel 1 to the neutral position. Further details regarding the steering wheel return current calculation unit 23 will be explained later.

[0044] Adder 24 adds the basic auxiliary current calculated by the basic auxiliary current calculation unit 22 to the return current calculated by the steering wheel return current calculation unit 23 to obtain the target current.

[0045] Furthermore, the control unit 12 of the control unit 11 is implemented by a microcomputer including a CPU (central processing unit) and memory. The memory provided in the microcomputer can include both volatile and non-volatile memory. The current drive unit 13 is implemented, for example, by an analog circuit equipped with multiple switching elements such as FETs (field-effect transistors).

[0046] Here, the operation of the control unit 11, which is a major component of the electric power steering system PS, will be explained in general. Furthermore, the operations described below are repeated within a pre-defined control cycle.

[0047] 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 steering 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 performs time differentiation on the motor rotation angle detected by the motor rotation angle sensor 10 to calculate the motor rotation angular velocity (steering angular velocity).

[0048] Next, the basic auxiliary current calculation unit 22 of the control unit 12 calculates the basic auxiliary current based on the steering angle detected by the steering angle sensor 4 and the vehicle speed detected by the vehicle speed sensor 8. The steering wheel return current calculation unit 23 of the control unit 12 calculates the steering wheel return current based on the steering torque detected by the steering torque sensor 5, the steering angle detected by the steering angle sensor 4, the vehicle speed detected by the vehicle speed sensor 8, and the steering angular velocity calculated by the motor rotational angular velocity detection unit 21. The adder 24 adds the basic auxiliary current calculated by the basic auxiliary current calculation unit 22 to the return current calculated by the steering wheel return current calculation unit 23 to obtain the target current. The current drive unit 13 of the control unit 11 controls the current flowing through the motor 6 based on the target current calculated by the adder 24.

[0049] Figure 3This is a block diagram showing the internal structure of the basic auxiliary current calculation unit in Embodiment 1 of this disclosure. For example... Figure 3 As shown, the basic auxiliary current calculation unit 22 includes a basic auxiliary current map 22a, a sign determination unit 22b, and a multiplier 22c.

[0050] The basic auxiliary current mapping 22a defines the relationship between steering torque, vehicle speed, and basic auxiliary current. When steering torque and vehicle speed are input, the basic auxiliary current mapping 22a outputs the absolute value (magnitude) of the basic auxiliary current corresponding to the absolute value of the steering torque and the vehicle speed. The sign determination unit 22b determines the sign of the input steering torque, outputting "+1" if the sign is positive and "-1" if the sign is negative. The multiplier 22c multiplies the basic auxiliary current output from the basic auxiliary current mapping 22a by the value output from the sign determination unit 22b.

[0051] The base auxiliary current mapping 22a has, for example, the following characteristics: The absolute value of the base auxiliary current increases as the absolute value of the steering torque increases. Furthermore, the absolute value of the base auxiliary current increases as the vehicle speed increases.

[0052] Figure 4 This is a block diagram showing the internal structure of the steering wheel return current calculation unit in Embodiment 1 of this disclosure. (As shown...) Figure 4 As shown, the steering wheel return current calculation unit 23 includes a basic return current calculation unit 30, a return current correction value calculation unit 33, and a return current calculation unit 34.

[0053] The steering angle detected by the steering angle sensor 4, the vehicle speed detected by the vehicle speed sensor 8, and the steering angular velocity calculated by the motor rotational angular velocity detection unit 21 are input to the reference return current calculation unit 30. The reference return current calculation unit 30 uses these detection results to calculate the reference return current, which serves as the basic value for the return current. The reference return current calculation unit 30 includes a target steering angular velocity calculation unit 31 and a return current feedback calculation unit 32.

[0054] Figure 5A This is a block diagram showing the internal structure of the target steering angular velocity calculation unit in Embodiment 1 of this disclosure. Figure 5A As shown, the target steering angular velocity calculation unit 31 includes a target steering angular velocity map 31a, a sign determination unit 31b, and a multiplier 31c.

[0055] The steering angle detected by the steering angle sensor 4 and the vehicle speed detected by the vehicle speed sensor 8 are input to the target steering angular velocity calculation unit 31. The target steering angular velocity calculation unit 31 calculates the target steering angular velocity based on the steering angle and the vehicle speed.

[0056] The target steering angular velocity mapping 31a defines the relationship between the target steering angular velocity, steering angle, and vehicle speed. When the steering angle and vehicle speed are input, the target steering angular velocity mapping 31a outputs the absolute value (magnitude) of the target steering angular velocity corresponding to the absolute value of the steering angle and the vehicle speed. The sign determination unit 31b determines the sign of the input steering angle, outputting "+1" if the sign is positive and "-1" if the sign is negative. The multiplier 31c multiplies the absolute value of the target steering angular velocity output from the target steering angular velocity mapping 31a by the value output from the sign determination unit 31b to calculate the target steering angular velocity.

[0057] The target steering angular velocity mapping 31a has, for example, the following characteristics: The absolute value of the target steering angular velocity increases as the absolute value of the steering angular velocity increases. Furthermore, the absolute value of the target steering angular velocity increases as the vehicle speed increases.

[0058] Figure 5B This is a block diagram illustrating other structural examples of the target steering angular velocity calculation unit in Embodiment 1 of this disclosure. Figure 5B The target steering angular velocity calculation unit 31 shown is configured to... Figure 5A The target steering angular velocity calculation unit 31 shown omits the sign determination unit 31b and the multiplier 31c, and only has the target steering angular velocity mapping 31a. Figure 5B In the target steering angular velocity calculation unit 31 shown, the target steering angular velocity, which is positive or negative, is calculated based on the sign of the steering angle.

[0059] Figure 6A This is a block diagram showing the internal structure of the feedback current calculation unit in Embodiment 1 of this disclosure. (As shown...) Figure 6A As shown, the feedback current calculation unit 32 includes a subtractor 41, a feedback current calculation unit 42, a constant term calculation unit 43, and an adder 44.

[0060] The target steering angular velocity calculated by the target steering angular velocity calculation unit 31 and the steering angular velocity calculated by the motor rotational angular velocity detection unit 21 are input to the return current feedback calculation unit 32. The return current feedback calculation unit 32 calculates the basic return current required to make the steering angular velocity follow the target steering angular velocity based on the difference between the target steering angular velocity and the steering angular velocity. That is, in this embodiment, the electric power steering device PS performs steering wheel return control using speed feedback control, which determines the target steering angular velocity of the steering wheel 1 and controls it to follow the target steering angular velocity.

[0061] Subtractor 41 subtracts the target steering angular velocity from the target steering angular velocity to calculate the difference between the target steering angular velocity and the steering angular velocity, i.e., the steering angular velocity difference. Feedback current calculation unit 42 includes amplifier 42a, which multiplies the steering angular velocity difference calculated by subtractor 41 by the control gain G to obtain the feedback current. The feedback current is used for feedback control to make the steering angular velocity difference close to 0. Constant term calculation unit 43 includes sign determination unit 43a and amplifier 43b. The steering angular velocity is input to constant term calculation unit 43. Sign determination unit 43a determines the sign of the input steering angular velocity, outputting "+1" if the sign is positive and "-1" if the sign is negative. Amplifier 43b multiplies the value output from sign determination unit 43a by constant term gain C to obtain a constant current. Adder 44 adds the feedback current obtained by feedback current calculation unit 42 to the constant current obtained by constant term calculation unit 43 to obtain the base homing current. Furthermore, by setting the constant term gain C, for example, to a value corresponding to the friction generated by the column portion of the motor 6 and / or the steering shaft 2, the effect of this friction can be counteracted.

[0062] Figure 6B This is a block diagram illustrating other structural examples of the feedback current calculation unit in Embodiment 1 of this disclosure. Figure 6B The feedback current calculation unit 32 shown is configured to... Figure 6A The constant term calculation unit 43 and adder 44 are omitted in the feedback current calculation unit 32 shown, leaving only the subtractor 41 and the feedback current calculation unit 42. Figure 6B In the feedback current calculation unit 32 shown, the feedback current calculated by the feedback current calculation unit 42 is output as the basic feedback current.

[0063] Figure 7A This is a block diagram showing the internal structure of the synchro current correction value calculation unit in Embodiment 1 of this disclosure. Figure 7A As shown, the homing current correction value calculation unit 33 includes a speed correction current mapping 33a (correction amount mapping), a sign determination unit 33b, a first multiplier 33c, a torque coefficient mapping 33d, and a second multiplier 33e.

[0064] The steering angular velocity calculated by the motor rotational angular velocity detection unit 21 and the steering torque detected by the steering torque sensor 5 are input to the return current correction value calculation unit 33. Based on the steering angular velocity and steering torque, the return current correction value calculation unit 33 calculates a return current correction value that corrects the base return current calculated by the base return current calculation unit 30 (return current feedback calculation unit 32). The return current correction value is a control quantity calculated based on the steering angular velocity and corresponding to the driver's steering input.

[0065] The speed correction current mapping 33a defines the relationship between the speed correction current (correction amount) and the steering angular velocity. When a steering angular velocity is input, the speed correction current mapping 33a outputs the absolute value (magnitude) of the speed correction current corresponding to the absolute value of the steering angular velocity. The sign determination unit 33b determines the sign of the input steering angular velocity, outputting "+1" if the sign is positive and "-1" if the sign is negative. The first multiplier 33c multiplies the absolute value of the speed correction current output from the speed correction current mapping 33a by the value output from the sign determination unit 33b to obtain the speed correction current.

[0066] For example, the speed correction current mapping 33a has the following characteristics: as the absolute value of the steering angular velocity increases, the absolute value of the speed correction current increases.

[0067] Torque coefficient mapping 33d is a mapping that defines the relationship between torque coefficient and steering torque. When steering torque is input, torque coefficient mapping 33d outputs the torque coefficient corresponding to the absolute value of the steering torque.

[0068] The torque coefficient mapping 33d has the following characteristics, for example: as the absolute value of the steering torque increases, the torque coefficient increases.

[0069] The second multiplier 33e multiplies the speed correction current by the torque coefficient to obtain the correction value of the return current.

[0070] Figure 7B This is a block diagram showing other structural examples of the synchro current correction value calculation unit in Embodiment 1 of this disclosure. Figure 7B The current correction value calculation unit 33 shown is configured to calculate the current correction value from the current correction value calculation unit 33. Figure 7A The sign determination unit 33b and the first multiplier 33c are omitted in the shown return current correction value calculation unit 33; only the speed correction current mapping 33a, the torque coefficient mapping 33d, and the second multiplier 33e are retained. Figure 7B In the feedback calculation unit 32 shown, the speed correction current, which is positive or negative, is determined according to the sign of the steering angular velocity.

[0071] Back Figure 4 The homing current calculation unit 34 has an adder 34a, which adds the basic homing current obtained by the basic homing current calculation unit 30 (homing current feedback calculation unit 32) to the homing current correction value obtained by the homing current correction value calculation unit 33 to obtain the homing current.

[0072] The basic return current calculated by the basic return current calculation unit 30 (return current feedback calculation unit 32) is a steering wheel return control quantity that uses speed feedback control to make the steering angular velocity follow the target steering angular velocity. The return current correction value calculated by the return current correction value calculation unit 33 is a value calculated based on the steering angular velocity and is a control quantity corresponding to the driver's steering. The return current is calculated by adding the basic return current and the return current correction value, and the basic return current is corrected using the return current correction value corresponding to the driver's steering. Therefore, in steering wheel return control using speed feedback control, it is possible to prevent the steering wheel return control from interfering with the driver's steering.

[0073] As explained above, the electric motor power steering device PS according to this embodiment includes: a steering torque sensor 5 for detecting the steering torque acting on the vehicle VE steering system; a steering angle sensor 4 for detecting the steering angle of the steering wheel 1 included in the steering system; an electric motor rotational angular velocity detection unit 21 for detecting the steering angular velocity of the steering wheel 1; an electric motor 6 for applying steering assist torque to the steering system; and a control unit 11 for controlling the drive of the electric motor 6. The control unit 11 includes: a basic assist current calculation unit 22 for calculating the basic control quantity, i.e., the basic assist current, for assisting the steering of the vehicle VE based on the steering torque; a steering wheel return current calculation unit 23 for calculating the return current for returning the steering wheel 1 to the neutral position; and an adder 24 for adding the basic assist current and the return current. The steering wheel return current calculation unit 23 includes: a basic return current calculation unit 30 that calculates the basic value of the return current based on the steering angle; a return current correction value calculation unit 33 that calculates the return current correction value based on the steering angular velocity and steering torque to correct the basic return current; and a return current calculation unit 34 that calculates the return current based on the basic return current and the return current correction value. The basic return current calculation unit 30 includes: a target steering angular velocity calculation unit 31 that calculates the target steering angular velocity of the steering wheel 1 based on the steering angle; and a return current feedback calculation unit 32 that calculates the difference between the target steering angular velocity and the steering angular velocity, i.e., the steering angular velocity difference, and calculates the basic return current based on the steering angular velocity difference. The return current correction value calculation unit 33 determines the speed correction current based on the steering angular velocity and multiplies the speed correction current by a torque coefficient corresponding to the steering torque to calculate the return current correction value.

[0074] By correcting the base return current using a return current correction value corresponding to the driver's steering, it is possible to prevent the steering wheel return control from hindering the driver's steering in steering wheel return control that uses speed feedback control.

[0075] Furthermore, by implementing steering wheel return control using speed feedback control, the effects of steering wheel return control on the torque feedback system, which consists of the steering torque acting on the steering system, the motor torque of the electric power steering unit PS, and the road reaction torque generated by the vehicle VE, can be suppressed. Therefore, the decrease in stability of the torque feedback system due to steering wheel return control can be prevented.

[0076] In addition, the return current feedback calculation unit 32 calculates the value obtained by adding a quantitative current corresponding to the steering angular velocity to the value based on the steering angular velocity difference, and uses it as the basic return current.

[0077] Therefore, the basic return current taking into account the steering angular velocity can be calculated. In addition, by setting the fixed current, for example, to a value corresponding to the friction generated by the motor 6 and / or the steering system (e.g., the column portion of the steering shaft 2), the effects of the aforementioned friction can be counteracted.

[0078] In addition, the return current correction value calculation unit 33 includes a speed correction current map 33a that defines the relationship between steering angular velocity and speed correction current, and calculates the speed correction current based on steering angular velocity by referring to the speed correction current map 33a.

[0079] In addition, the return current correction value calculation unit 33 includes a torque coefficient mapping 33d that defines the relationship between steering torque and torque coefficient. The torque coefficient is calculated based on the steering torque by referring to the torque coefficient mapping 33d.

[0080] Therefore, the return current correction value that follows the driver's steering can be calculated more accurately.

[0081] In addition, the electric power steering system PS also has a motor rotation angle sensor 10 that detects the rotation angle of the motor 6. The motor rotation angle detection unit 21 uses the rotation angle detected by the motor rotation angle sensor 10 to detect the steering angular velocity.

[0082] Therefore, the steering angular velocity can be easily detected.

[0083] [Implementation Method 2]

[0084] <Electric power steering systems and vehicles>

[0085] 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.

[0086] <Steering Control Device>

[0087] 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 return current calculation unit 34 provided in the control unit 11 is different. Hereinafter, the return current calculation unit 34 will be described in detail.

[0088] Figure 8 This is a block diagram showing the internal structure of the positive current calculation unit in Embodiment 2 of this disclosure. (As shown...) Figure 8 As shown, the homing current calculation unit 34 in this embodiment includes a homing current correction value limiting unit 51, an adder 52, and a homing current limiting unit 53.

[0089] Figure 9 This is a block diagram showing the internal structure of the return current correction value limiting section in Embodiment 2 of this disclosure. Figure 9 As shown, the sync current correction value limiting unit 51 includes an absolute value calculation unit 51a, an amplifier 51b, and a limiter 51c.

[0090] The basic return current calculated by the basic return current calculation unit 30 and the return current correction value calculated by the return current correction value calculation unit 33 are input to the return current correction value limiting unit 51. The return current correction value limiting unit 51 limits the return current correction value based on the basic return current and calculates the limited return current correction value.

[0091] The absolute value calculation unit 51a calculates the absolute value of the base homing current and outputs it as the upper limit value to the limiter 51c. The amplifier 51b calculates the value obtained by multiplying the absolute value of the base homing current obtained by the absolute value calculation unit 51a by "-1" and outputs it as the lower limit value to the limiter 51c. The limiter 51c compares the homing current correction value obtained by the homing current correction value calculation unit 33 with the aforementioned upper and lower limits. Based on the comparison result, the limiter 51c limits the homing current correction value to a range where the absolute value of the base homing current is the upper limit and the value obtained by multiplying the absolute value of the base homing current by "-1" is the lower limit, and outputs the limited value as the limited homing current correction value.

[0092] Furthermore, the current correction value limiting unit 51 is not limited to... Figure 9 The structure shown can be any structure as long as it has the function of limiting the correction value of the return current within the above range.

[0093] Adder 52 adds the basic return current calculated by the basic return current calculation unit 30 to the restricted return current correction value calculated by the return current correction value limiting unit 51 to calculate the return current before restriction.

[0094] Figure 10This is a block diagram showing the internal structure of the return current limiting section in Embodiment 2 of this disclosure. (As shown...) Figure 10 As shown, the positive current limiting unit 53 includes an absolute value calculation unit 53a, an amplifier 53b, and a limiter 53c.

[0095] The basic return current calculated by the basic return current calculation unit 30 and the pre-limit return current calculated by the adder 52 are input to the return current limiting unit 53. The return current limiting unit 53 limits the pre-limit return current based on the basic return current and calculates the return current.

[0096] The absolute value calculation unit 53a calculates the absolute value of the base homing current and outputs it as the upper limit value to the limiter 53c. The amplifier 53b calculates the value obtained by multiplying the absolute value of the base homing current obtained by the absolute value calculation unit 53a by "-1" and outputs it as the lower limit value to the limiter 53c. The limiter 53c compares the pre-limit homing current obtained by the adder 52 with the above upper and lower limits. Based on the comparison result, the limiter 53c limits the pre-limit homing current to a range where the absolute value of the base homing current is the upper limit value and the value obtained by multiplying the absolute value of the base homing current by "-1" is the lower limit value, and outputs the limited value as the homing current.

[0097] Furthermore, the return current limiting unit 53 is not limited to Figure 10 The structure shown can be any structure as long as it has the function of limiting the positive current of the limiting circuit to the above range.

[0098] As explained above, in this embodiment, the homing current calculation unit 34 further includes: a homing current correction value limiting unit 51, which limits the homing current correction value based on the basic homing current and calculates the limited homing current correction value; and a homing current limiting unit 53, which limits the pre-limiting homing current obtained by adding the basic homing current and the limited homing current correction value based on the basic homing current and calculates the homing current.

[0099] By imposing a limit on the return current correction value and the return current before limitation in the return current calculation unit 34, it is possible to prevent the return current from being over-corrected by the return current correction value, and to more effectively prevent the driver's steering from being hindered by the steering wheel return control.

[0100] [Implementation Method 3]

[0101] <Electric power steering systems and vehicles>

[0102] The electric power steering device and vehicle structure involved in this embodiment are basically the same as... Figure 1The 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.

[0103] <Steering Control Device>

[0104] 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 return current correction value calculation unit 33 provided in the control unit 11 is different. Hereinafter, the return current correction value calculation unit 33 will be described in detail.

[0105] Figure 11 This is a block diagram showing the internal structure of the synchro current correction value calculation unit in Embodiment 3 of this disclosure. Figure 11 As shown, the sync current correction value calculation unit 33 in this embodiment includes a first amplifier 61, a second amplifier 62, a torque coefficient limiting unit 63, and a multiplier 64.

[0106] The first amplifier 61 calculates the speed correction current by multiplying the steering angular velocity calculated by the motor rotational angular velocity detection unit 21 by the control gain Gw (first gain). The second amplifier 62 calculates the torque coefficient before limiting by multiplying the steering torque detected by the steering torque sensor 5 by the control gain Gt (second gain).

[0107] Figure 12 This is a block diagram showing the internal structure of the torque coefficient limiting unit in Embodiment 3 of this disclosure. Figure 12 As shown, the torque coefficient limiting unit 63 includes a limiter 63a, which limits the torque coefficient before limiting to a range with "1" as the upper limit and "0" as the lower limit, and outputs the value after limiting as the torque coefficient.

[0108] Furthermore, the torque coefficient limiting part 63 is not limited to Figure 11 The structure shown can be any structure as long as it has the function of limiting the torque coefficient before limiting to the above range.

[0109] The multiplier 64 multiplies the speed correction current obtained by the first amplifier 61 by the torque coefficient obtained by the torque coefficient limiting unit 63 to obtain the return current correction value.

[0110] As explained above, in this embodiment, the return current correction value calculation unit 33 multiplies the steering angular velocity with the control gain Gw to calculate the speed correction current.

[0111] Furthermore, the return current correction value calculation unit 33 calculates the torque coefficient based on the value obtained by multiplying the steering torque and the control gain Gt.

[0112] Therefore, for example, compared to the case where the speed correction current or torque coefficient is calculated by reference mapping, the amount of computation in the return current correction value calculation unit 33 can be reduced.

[0113] Furthermore, the technical scope of this disclosure is not limited to the described embodiments, and various modifications can be made without departing from the spirit of this disclosure.

[0114] For example, in the above embodiment, the motor rotational angular velocity detection unit 21 is used as the steering angular velocity detection unit, and the steering angular velocity of the steering wheel 1 is calculated using the rotational speed of the motor 6 detected by the motor rotational angle sensor 10. However, as an alternative to the detection result of the motor rotational angle sensor 10, the steering angular velocity of the steering wheel 1 can be calculated using the value obtained by time differentiation of the steering angle detected by the steering angle sensor 4, or by multiplying the induced voltage generated based on the rotational speed of the motor 6 by a coefficient, or by using both the value obtained by time differentiation of the steering angle and the motor rotational speed.

[0115] Furthermore, in the above embodiment, the steering angle sensor 4 is used as the steering angle detection unit, and the steering angle detected by the steering angle sensor 4 is used in the steering wheel return current calculation unit 23. However, the detection result of the steering angle sensor 4 can be used instead of the result obtained by converting the rotation angle of the motor 6 detected by the motor rotation angle sensor 10 into a steering angle.

[0116] Alternatively, the above-described embodiments or variations can be appropriately combined.

[0117] For example, Embodiment 2 and Embodiment 3 can be combined. That is, the electric power steering device PS can have both the return current calculation unit 34 of Embodiment 2 and the return current correction value calculation unit 33 of Embodiment 3.

[0118] Furthermore, the return current correction value calculation unit 33 can combine the structure of Embodiment 1 and the structure of Embodiment 3. Specifically, as follows: Figure 7A or Figure 7B As shown, the return current correction value calculation unit 33 can refer to the speed correction current mapping 33a to calculate the speed correction current based on the steering angular velocity, and as... Figure 11 As shown, the torque coefficient can be calculated based on the value obtained by multiplying the steering torque by the control gain Gt. Figure 11 As shown, the return current correction value calculation unit 33 can calculate the speed correction current based on the value obtained by multiplying the steering angular velocity by the control gain Gw, and as... Figure 7A or Figure 7B As shown, the torque coefficient can be calculated based on the steering torque by referring to the torque coefficient mapping 33d.

[0119] Furthermore, the control unit 12 of the aforementioned control unit 11 has an internal computer system. Moreover, the program for implementing the functions of the control unit 12 of the control unit 11 can be recorded on a computer-readable recording medium, and the processing within each structure of the control unit 11 is performed by reading the program recorded on the recording medium into the computer system and executing the program. Here, "reading the program recorded on the recording medium into the computer system and executing it" includes installing an application in the computer system. The term "computer system" here includes hardware such as the operating system and peripheral devices.

[0120] Furthermore, "computer system" can include multiple computer devices connected via a network including communication lines such as the Internet, WAN, LAN, or dedicated lines. Additionally, "computer-readable recording medium" refers to portable media such as floppy disks, magneto-optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Thus, recording media storing programs can also be non-transitory recording media such as CD-ROMs.

[0121] Additionally, the recording medium may include a recording medium that can be accessed from a distribution server to distribute the program, either internally or externally. Furthermore, it may be a structure where the program is divided into multiple parts, downloaded at different times, and then merged into various structures within the control unit 11. Moreover, the distribution servers used to distribute the individual parts of the program may be different. Additionally, the term "computer-readable recording medium" includes media that retain the program for a certain period of time, such as volatile memory (RAM) within a computer system that serves as a server or client when sending a program over a network. Furthermore, the program described above may be a program used to implement the aforementioned functions. Additionally, it may be a so-called differential file (differential program) capable of implementing the aforementioned functions through combination with programs already recorded in the computer system.

[0122] Label Explanation

[0123] 1. Steering wheel (steering component)

[0124] 2 steering shafts

[0125] 4. Steering angle sensor (steering angle detection unit)

[0126] 5. Steering torque sensor (steering torque detection unit)

[0127] 6 electric motors

[0128] 10 Motor Rotation Angle Sensor

[0129] 11. Control Unit (Steering Control Device)

[0130] 21. Motor rotational angular velocity detection unit (steering angular velocity detection unit)

[0131] 22 Basic Auxiliary Current Calculation Unit

[0132] 23 Steering wheel return current calculation unit

[0133] 24 Adders

[0134] 30 Basic Returning Current Calculation Unit

[0135] 31 Target Turning Angular Velocity Calculation Unit

[0136] 32-phase positive current feedback operation unit

[0137] 33-way current correction value calculation unit

[0138] 33a Velocity Correction Current Mapping (Correction Amount Mapping)

[0139] 33d torque coefficient mapping

[0140] 34-way positive current calculation unit

[0141] 51 Return Current Correction Value Limiting Section

[0142] 53 Return Current Limiting Section

[0143] VE vehicles

[0144] PS electric power steering system.

Claims

1. An electric power steering device, characterized in that, include: A steering torque detection unit that detects the steering torque acting on the vehicle's steering system; A steering angle detection unit that detects the steering angle of the steering components included in the steering system; A steering angular velocity detection unit that detects the steering angular velocity of the steering component; An electric motor that applies steering assist torque to the steering system; as well as A steering control device that controls the drive of the electric motor. The steering control device includes: The basic auxiliary current calculation unit calculates the basic control quantity, i.e., the basic auxiliary current, that assists the steering of the vehicle based on the steering torque. A steering wheel return current calculation unit calculates the return current used to return the steering component to the neutral position; and An adder that adds the base auxiliary current to the positive current. The steering wheel return current calculation unit includes: The basic return current calculation unit calculates the basic value of the return current, i.e., the basic return current, based on the turning angle. A return current correction value calculation unit calculates a return current correction value to correct the basic return current based on the steering angular velocity and the steering torque; and The correction current calculation unit calculates the correction current based on the base correction current and the correction current correction value. The basic return current calculation unit includes: A target steering angular velocity calculation unit calculates the target steering angular velocity of the steering component based on the steering angle; and The return-to-center current feedback calculation unit calculates the difference between the target steering angular velocity and the steering angular velocity, i.e., the steering angular velocity difference, and calculates the basic return-to-center current based on the steering angular velocity difference. The return current correction value calculation unit determines the correction amount based on the steering angular velocity, and calculates the return current correction value by multiplying the correction amount by a coefficient corresponding to the steering torque.

2. The electric power steering device as described in claim 1, characterized in that, The return current feedback calculation unit calculates the value obtained by adding a constant corresponding to the steering angular velocity to the value based on the difference in steering angular velocity, and uses this value as the basic return current.

3. The electric power steering device as described in claim 1 or 2, characterized in that, The current calculation unit for the positive current also has: A current correction value limiting unit limits the current correction value based on the basic current correction value and calculates the limited current correction value. as well as The homing current limiting unit limits the pre-limiting homing current, which is obtained by adding the base homing current to the homing current correction value after limiting, based on the base homing current, and calculates the homing current.

4. The electric power steering device as described in any one of claims 1 to 3, characterized in that, The homing current correction value calculation unit has a correction amount mapping that defines the relationship between the steering angular velocity and the correction amount, and calculates the correction amount based on the steering angular velocity by referring to the correction amount mapping.

5. The electric power steering device as described in any one of claims 1 to 3, characterized in that, The correction current calculation unit calculates the correction amount by multiplying the steering angular velocity by the first gain.

6. The electric power steering device as described in any one of claims 1 to 5, characterized in that, The return current correction value calculation unit has a torque coefficient mapping that defines the relationship between the steering torque and the coefficient, and calculates the coefficient based on the steering torque by referring to the torque coefficient mapping.

7. The electric power steering device as described in any one of claims 1 to 5, characterized in that, The return current correction value calculation unit calculates the coefficient based on the value obtained by multiplying the steering torque by the second gain.

8. The electric power steering device as described in any one of claims 1 to 7, characterized in that, The steering angular velocity detection unit uses at least one of the value obtained by differentiating the steering angle over time and the induced voltage generated by the drive of the motor to detect the steering angular velocity.

9. The electric power steering device as described in any one of claims 1 to 7, characterized in that, It also includes a motor rotation angle sensor for detecting the rotation angle of the motor. The steering angular velocity detection unit uses the rotation angle detected by the motor rotation angle sensor to detect the steering angular velocity.

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