Steering control device, steering control system, electric power steering device, and vehicle

Abstract

The present invention comprises a torque control unit, a steering angle control unit, a switching unit, and a driving unit. When switching from torque control to steering angle control is instructed, the steering angle control unit sets an initial value of a steering angle control integral term on the basis of a torque control integral term, or continuously changes a target steering torque from the steering torque to the original target steering torque over a predetermined gradual change time. When switching from the steering angle control to the torque control is instructed, the torque control unit sets the initial value of the torque control integral term on the basis of the steering angle control integral term, or continuously changes the target steering angle from the detection steering angle to the original target steering angle over the gradual change time.

Description

Steering control device, steering control system, electric power steering device and vehicle

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

[0002] The steering control device described in Patent Document 1 performs assist control and steering angle control. Assist control is a function that assists the driver in operating a steering mechanism. Assist control is a function typically provided in an electric power steering (EPS) system. Steering angle control is sometimes performed by automatic steering in automatic driving. When automatic steering angle control is started while the driver is steering, the steering control device recalculates a steering angle command value used in steering angle command tracking control based on the steering angle and steering angle command value at the start of steering control so that the actual steering angle gradually approaches the steering angle command value. Specifically, the difference between the actual steering angle (actual steering angle) at the start of automatic steering control and the original value of the steering angle command value is passed through a first-order low-pass filter, and the resulting value is calculated as the recalculated steering angle command value.

[0003] Furthermore, when the steering angle command value used in the steering angle control is recalculated, the steering control device is configured to stop updating the integral value included in the integral term of the steering angle control or to reset the integral value, thereby preventing the controllability from being affected by the control result of the steering angle control based on the recalculated value after returning to normal steering angle command tracking control.

[0004] The electric power steering device of Patent Document 2 performs torque control equivalent to assist control and steering angle control, similar to the operation control device described in Patent Document 1. When steering angle control is started while the driver is steering, the electric power steering device gradually changes the steering angle command value from the actual steering angle to a steering angle command value based on the steering angle control, and the torque control gradually changes the assist torque level from 100% to 0%. The actuator control device described in Patent Document 3 performs torque control equivalent to assist control and steering angle control, similar to the operation control device described in Patent Document 1. When the driver intervenes in steering during self-driving steering, the actuator control device limits or stops integration of the integral term in the steering angle control depending on the steering torque applied by the driver.

[0005] JP 2018-172050 A JP 2017-19498 A JP 2018-24281 A

[0006] In the steering control device described in Patent Document 1, when transitioning from assist control to steering angle control, simply limiting or stopping the integration of the integral term of steering angle control does not ensure continuity with the motor torque or current obtained by assist control. Depending on the steering state, discontinuity in the motor torque or current may occur, which may cause ripples or vibrations in the steering shaft.

[0007] Furthermore, when the driver intervenes in steering during automatic steering, the actuator control device described in Patent Document 3 limits or stops integration of the integral term of the steering angle control in accordance with the steering torque applied by the driver, and starts integration of the integral term of the assist control from a value different from that of the steering angle control. Because continuity of the integral term is not ensured, ripples and vibrations may occur in the steering shaft.

[0008] Furthermore, the above-mentioned documents do not disclose switching between target steering torque control and steering angle control in assist control. Target steering torque control is a control in which a target value of steering torque is set as a target steering torque based on the steering angle, etc., and the detected steering torque value is made to follow the set target steering torque. Like steering angle control, target steering torque control is a target value tracking control, so it cannot be executed in parallel with steering angle control. Continuous switching between the two is difficult because one of the controls must be paused. For example, Patent Document 2 describes a torque gradual change unit on the output side of torque control fading out torque control. However, in target value tracking target steering torque control, such forced limiting processing on the output side prevents the suppression of the deviation between the target and detected steering torque values ​​when torque control is resumed. As a result, the integral term in the tracking control is actually amplified, which can prevent smooth switching of the control.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a steering control device, a steering control system, an electric power steering device, and a vehicle that can suppress ripple and vibration of the steering shaft and simply achieve more continuous and smooth switching between steering angle control by automatic steering and torque control for steering by the driver.

[0010] A first aspect of the present disclosure has been made to solve the above-mentioned problems, and is a steering control device including: a torque control unit that outputs a torque control target current for driving a steering mechanism based on a steering torque; a steering angle control unit that calculates a steering angle control target current based on a steering angle deviation that is a deviation between the steering angle of the steering mechanism and a target steering angle; a switching unit that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as a target current; and a driving unit that applies torque to the steering mechanism based on the target current, wherein the torque control unit outputs a torque control target current based on the steering torque. the steering angle control unit includes a torque integrator that integrates a value based on the steering angle deviation to derive a torque control integral term of the steering angle control target current, and the steering angle control unit includes a steering angle integrator that integrates a value based on the steering angle deviation to derive a steering angle control integral term of the steering angle control target current, and when the switching signal instructs switching from torque control to steering angle control, the steering angle control unit sets an initial value of the steering angle control integral term based on the torque control integral term, and when the switching signal instructs switching from steering angle control to torque control, the torque control unit sets an initial value of the torque control integral term based on the steering angle control integral term.

[0011] A second aspect of the present disclosure includes a torque control unit that outputs a torque control target current based on a torque deviation, which is the deviation between a steering torque acting on a steering mechanism and a target steering torque; a steering angle control unit that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and a target steering angle; a target current output unit that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as a target current, or outputs the sum of the torque control target current and the steering angle control target current as a target current; and a drive unit that applies torque to the steering mechanism based on the target current, wherein when the switching signal instructs switching from steering angle control to torque control, the torque control unit continuously changes the target steering torque from the steering torque to an original target steering torque over a predetermined gradual-change time, and when the switching signal instructs switching from torque control to steering angle control, the steering angle control unit continuously changes the target steering angle from the steering angle to the original target steering angle over the gradual-change time.

[0012] A third aspect of the present disclosure may be a steering control system including a steering torque detection unit that detects a steering torque, a steering angle detection unit that detects a steering angle, and the above-described steering control device.

[0013] A fourth aspect of the present disclosure may be a steering control system including a driving assistance system having an automatic steering control function and the above-described steering control device.

[0014] A fifth aspect of the present disclosure may be an electric power steering device including a steering mechanism and the above-described steering control device.

[0015] A fifth aspect of the present disclosure may be a vehicle including the electric power steering device described above.

[0016] According to the present disclosure, ripple and vibration of the steering shaft can be suppressed, and more continuous and smooth switching between steering angle control by automatic steering and steering torque control by the driver can be easily achieved. For example, in a first aspect, when switching from one of transition torque control and steering angle control to the other, the initial value of the integral term of the other is set to a value based on the integral term of one at that time. Since the continuity of control is high before and after the switch, ripple and vibration of the steering shaft are suppressed, and smooth behavior is achieved. In a second aspect, when switching from one of target steering torque control and steering angle control to the other, the target value of the other at that time is temporarily set to a detected value and gradually changed to the original target value. Since the deviation input to the controller gradually changes from zero to the original deviation, control of the other is gradually initiated. Therefore, ripple and vibration of the steering shaft are avoided, and smooth behavior is achieved. Note that by combining the features of the first and second aspects, behavior during control switching becomes even smoother.

[0017] FIG. 1 is a block diagram illustrating a schematic configuration of an electric power steering device according to a first embodiment. FIG. 2 is a block diagram illustrating a configuration example of a steering control device according to the first embodiment. FIG. 3 is a block diagram illustrating a functional configuration example of a torque control unit and a steering angle control unit according to the first embodiment. FIG. 4 is a block diagram illustrating a functional configuration example of a switching signal generation unit according to the first embodiment. FIG. 5 is a block diagram illustrating a configuration example of a torque gradual change unit according to the first embodiment. FIG. 6 is a block diagram illustrating a configuration example of a steering angle gradual change unit according to the first embodiment. FIG. 7 is an explanatory diagram illustrating a first operation example related to switching of a control method. FIG. 8 is an explanatory diagram illustrating a second operation example related to switching of a control method. FIG. 9 is a block diagram illustrating a configuration example of a torque control unit and a steering angle control unit according to a second embodiment. FIG. 10 is a block diagram illustrating a configuration example of a torque control unit and a steering angle control unit according to a third embodiment. FIG. 11 is a block diagram illustrating a configuration example of a torque control unit and a steering angle control unit according to a fourth embodiment. FIG. 12 is an explanatory diagram illustrating an example of transfer of an integral term according to a fifth embodiment. FIG. 13 is a block diagram illustrating a configuration example of a steering control device according to a sixth embodiment. FIG. 14 is a block diagram illustrating a configuration example of a torque control unit and a steering angle control unit according to the sixth embodiment. FIG. 15 is a block diagram illustrating a configuration example of a steering control system and a vehicle according to a seventh embodiment.

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Elements common to or corresponding to each drawing are designated by the same reference numerals, and the description thereof will be incorporated unless otherwise specified. <Embodiment 1> (Electric Power Steering Device) First, a schematic configuration of an electric power steering device PS according to embodiment 1 of the present disclosure will be described. FIG. 1 is a block diagram illustrating a schematic configuration of an electric power steering device PS according to this embodiment. The electric power steering device PS includes a steering wheel 1, a steering shaft 2, steered wheels 3, a steering angle detection unit 4, a torque sensor 5, a motor 6, a reduction mechanism 7, a vehicle speed sensor 8, and a control unit 11. A host controller 9 is mounted on the vehicle. The host controller 9 does not have to be included in the components of the electric power steering device PS.

[0019] The steering wheel 1 is connected at its center to one end of a steering shaft 2. The steering wheel 1 receives operation by the vehicle driver and rotates around the longitudinal direction of the steering shaft 2 due to external forces applied by the operation. The other end of the steering shaft 2 is connected to the center of the axle. The steering shaft 2 rotates around the longitudinal direction in response to the rotation of the steering wheel 1.

[0020] The steerable wheels 3 are installed at both ends of the axle and are steered in response to the rotation of the steering shaft 2. A steering angle is applied to the steerable wheels 3 of the vehicle by the rotation of the steering wheel 1. In this disclosure, the mechanism for steering the steerable wheels 3, including the steering wheel 1 and the steering shaft 2, may be referred to as "steering" or "steering mechanism."

[0021] The steering angle detection unit 4 is arranged on the steering wheel 1 or the steering shaft 2 and includes a steering angle sensor that detects the steering angle of the steering shaft 2. The steering angle detection unit 4 notifies the control unit 11 of the detected steering angle as a detected steering angle. The torque sensor 5 is arranged on the steering shaft 2 and detects the steering torque acting on the steering shaft 2. The torque sensor 5 functions as a steering torque detection unit. The steering torque corresponds to the torque acting on the steering wheel 1 due to an external force applied by operation. The torque sensor 5 notifies the control unit 11 of the detected steering torque as a detected steering torque.

[0022] 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 motor 6 operates under the control of a control unit 11. The vehicle speed sensor 8 detects the speed of the vehicle as the vehicle speed. The vehicle speed sensor 8 notifies the control unit 11 of the detected vehicle speed.

[0023] The host controller 9 is a controller having a control function of the driving assistance system. The control function of the driving assistance system includes, for example, some or all of known functions such as automatic driving, lane keep assist, and automatic parking. The host controller 9 may calculate a target value for the steering angle as a control target value by executing the control function. The host controller 9 outputs the calculated target value to the control unit 11 as a target steering angle.

[0024] The control unit 11 receives the detected steering angle from the steering angle detector 4, the detected steering torque from the torque sensor 5, the vehicle speed from the vehicle speed sensor 8, and the target steering angle from the host controller 9. The control unit 11 controls the operation of the motor 6 based on the detected steering angle, the detected steering torque, the vehicle speed, and the target steering angle, and generates a steering assist torque for the steering mechanism. More specifically, the control unit 11 calculates a target current based on the detected steering angle, the detected steering torque, the vehicle speed, and the target steering angle. The control unit 11 uses a current controller 26 (FIG. 2) to control the current supplied to the motor 6 so that it follows the target current.

[0025] In the present application, a configuration including the current control unit 26 and the motor 6 may be referred to as a drive unit 25 (FIG. 2). The current control unit 26 and the motor 6 may be integrated into a single drive unit 25, or may be implemented as separate components. In addition, a configuration including the control unit 11 and the motor 6 may be referred to as a steering control device 10 (FIG. 2). The control unit 11 and the motor 6 may be integrated into a single steering control device 10, or may be implemented as separate components. In addition, the control unit 11 may be configured as a steering control device 10 without the motor 6.

[0026] <Steering Control Device> Next, a configuration example of the steering control device 10 according to this embodiment will be described. Fig. 2 is a block diagram showing a configuration example of the steering control device 10 according to this embodiment. The steering control device 10 includes a control unit 11 and a motor 6. The control unit 11 includes a differentiating section 24, a torque control section 20, a steering angle control section 21, a switching signal generating section 27, a switching section 23, and a current control section 26.

[0027] The differentiating unit 24 differentiates the detected steering angle input from the steering angle detecting unit 4 to calculate the steering angular velocity of the steering shaft 2. The differentiating unit 24 outputs the calculated steering angular velocity to the steering angle control unit 21 as the detected steering angular velocity. Note that the steering angle detecting unit 4 may be equipped with a motor rotation angle sensor instead of the steering angle sensor. The motor rotation angle sensor detects the rotation angle of the motor 6. The steering angle detecting unit 4 may normalize the integral value obtained by integrating the rotation angle detected by the motor rotation angle sensor and calculate it as the detected steering angular velocity.

[0028] The switching signal generating unit 27 determines whether to execute torque control or steering angle control, i.e., which control method to activate, based on the detected steering torque input from the torque sensor 5. When switching between torque control and steering angle control, the switching signal generating unit 27 determines whether to continuously change the weighting coefficient for one of the control methods from a maximum value to a minimum value over a predetermined gradual change time or more, or whether to continuously change the weighting coefficient for the other control method from a minimum value to a maximum value over a predetermined gradual change time or more. The switching signal generating unit 27 generates a switching signal indicating the control method to be activated and a weighting signal indicating the time change of the weighting coefficient of a predetermined constant control method. The switching signal generating unit 27 outputs the generated switching signal to the steering angle control unit 21, the torque control unit 20, and the switching unit 23. The switching signal generating unit 27 outputs the generated weighting signal to the switching unit 23. An example configuration of the switching signal generating unit 27 will be described later.

[0029] The torque control unit 20 executes processing related to the above-described assist control. In the assist control, the torque control unit 20 calculates a torque control target current using a control method called target steering torque control. The target steering torque control is a method of calculating a target value of the steering torque as a target steering torque based on the detected steering angle input from the steering angle detection unit 4, and making the detected steering torque follow the calculated target steering torque. The torque control unit 20 outputs the calculated torque control target current to the switching unit 23. An example configuration of the torque control unit 20 will be described later.

[0030] The steering angle control unit 21 receives the target steering angle from the host controller 9, the detected steering angle from the steering angle detection unit 4, the detected steering angular velocity from the differentiation unit 24, and a switching signal and a weighting signal from the switching signal generation unit 27. The steering angle control unit 21 references the switching signal and the weighting signal and calculates the target steering angular velocity based on the steering angle deviation, which is the difference between the target steering angle and the detected steering angle. The steering angle control unit 21 calculates a steering angle control target current according to the deviation between the target steering angular velocity and the detected steering angular velocity, and outputs the output value of the calculated steering angle control target current to the switching unit 23. An example configuration of the steering angle control unit 21 will be described later.

[0031] The switching unit 23 switches between the torque control target current input from the torque control unit 20 and the steering angle control target current input from the steering angle control unit 21 in accordance with a switching signal input from the switching signal generation unit 27. When the switching signal indicates a value Trq that activates the torque control, the switching unit 23 outputs the torque control target current as the target current to the current control unit 26. When the switching signal indicates a value Ang that activates the steering angle control, the switching unit 23 outputs the steering angle control target current as the target current to the current control unit 26.

[0032] The current control unit 26 controls the current supplied to the motor 6 so that it follows the target current input from the switching unit 23. The current control unit 26 includes, for example, a microcontroller, a switching element, and a current detector. The current detector detects the current actually supplied from the current control unit 26 to the motor 6 as a current detection value. The analog circuit includes a switching element that controls the opening and closing of the DC power supply and the input terminal of each phase of the motor 6. The microcontroller includes an analog circuit. The microcontroller generates a command for the analog circuit so that the current detection value follows the target current, and outputs the generated command to the analog circuit. The switching element is, for example, a field-effect transistor (FET).

[0033] Next, an example of the configuration of the torque control unit 20 will be described. Fig. 3 is a block diagram showing an example of the functional configuration of the torque control unit 20 and the steering angle control unit 21 according to this embodiment. The torque control unit 20 includes a target steering torque setting unit 51, a gradual torque change unit 58, a subtraction unit 52, multiplication units 53 and 54, a torque integration unit 60, and an addition unit 57.

[0034] The target steering torque setting unit 51 receives the detected steering angle from the steering angle detection unit 4 and calculates the detected steering angular velocity by differentiating the detected steering angle with respect to time. The target steering torque setting unit 51 also receives the vehicle speed from the vehicle speed sensor 8 (not shown). The target steering torque setting unit 51 sets the target steering torque using a known method based on the detected steering angle, vehicle speed, and detected steering angular velocity. The target steering torque setting unit 51 outputs the set target steering torque to the torque gradual change unit 58.

[0035] The torque gradual change unit 58 performs gradual change processing on the target steering torque input from the target steering torque setting unit 51, and outputs the target steering torque obtained by the gradual change processing to the subtraction unit 52. In the present disclosure, "gradual change processing" or "gradual change" refers to processing for determining an output value such that, when an input value changes suddenly at a certain point in time, the output value changes continuously from the input value before the change to the input value after the change over a period of time equal to or longer than a predetermined gradual change time.

[0036] Subtraction unit 52 calculates a torque deviation by subtracting the detected steering torque input from torque sensor 5 from the gradually-changed target steering torque input from torque gradual-change unit 58. Subtraction unit 52 outputs the calculated torque deviation to multiplication units 53 and 54. Multiplication unit 53 multiplies the torque deviation input from subtraction unit 52 by a preset torque control proportional gain Ktp to calculate a torque control proportional term. Multiplication unit 53 outputs the calculated torque control proportional term to addition unit 57. Multiplication unit 54 multiplies the torque deviation input from subtraction unit 52 by a preset torque control integral gain Kti, and outputs the multiplied value to torque integration unit 60.

[0037] The torque integrator 60 time-integrates the multiplied value input from the multiplier 54 to obtain the torque control integral term Iit ０ The torque integration unit 60 calculates the calculated torque control integral term Iit ０ The adder 57 outputs the torque control proportional term input from the multiplier 53 and the torque control integral term Iit ０ and outputs an electrical signal indicating the sum obtained by adding the above to the switching unit 23 as a torque control target current.

[0038] The steering angle control unit 21 includes a steering angle gradual change unit 41 , subtraction units 31 and 34 , multiplication units 32 , 35 and 36 , addition units 33 and 39 , a steering intervention correction unit 40 , and a steering angle integration unit 43 .

[0039] The steering angle gradual-change unit 41 applies gradual-change processing to the target steering angle input from the higher-level controller 9, and outputs the gradually-changed target steering angle obtained by this processing to the subtraction unit 31. The subtraction unit 31 calculates a difference as the steering angle deviation Δθ by subtracting the detected steering angle input from the steering angle detection unit 4 from the gradually-changed target steering angle input from the steering angle gradual-change unit 41. The subtraction unit 31 outputs the calculated steering angle deviation Δθ to the multiplication unit 32. The multiplication unit 32 multiplies the steering angle deviation Δθ input from the subtraction unit by a preset steering angle control gain Kp, and outputs the product to the addition unit 33 as the pre-correction target steering angle speed.

[0040] The steering intervention correction unit 40 performs phase compensation on the detected steering torque input from the torque sensor 5 and calculates a steering intervention correction value by multiplying the phase-compensated detected steering torque by a gain α. The steering intervention correction unit 40 outputs the calculated steering intervention correction value to the adder 33. Therefore, the steering intervention function of the steering intervention correction unit 40 realizes a change in the steering angle in accordance with the driver's intention by adding a correction according to the steering torque to the control value of the steering angle control when steering intervention occurs due to steering by the driver during automatic steering by steering angle control based on the target steering angle. During steering angle control, the actual steering angle follows the target steering angle and is adjusted so that the two match. Therefore, when steering intervention occurs, the steering intervention correction unit 40 compensates for the steering angle at that time to be deviated from the target steering angle in accordance with the steering torque.

[0041] The adder 33 calculates a corrected target steering angular velocity by adding the pre-correction target steering angular velocity input from the multiplier 32 and the steering intervention correction value input from the steering intervention correction unit 40. The adder 33 outputs the calculated target steering angular velocity to the subtracter 34. Note that, instead of the adder 33 that adds the steering intervention correction value to the pre-correction target steering angular velocity, the steering angle control unit 21 may include an adder (not shown) that outputs a sum obtained by adding the steering intervention correction value to the steering angle deviation Δθ to the multiplier 32 as a corrected steering angle deviation, and the product output from the multiplier 32 may be output to the subtracter 34 as the corrected target steering angular velocity. In this case as well, when steering intervention occurs, the steering angular velocity at that time is compensated to deviate from the target steering angular velocity in accordance with the steering torque.

[0042] The subtraction unit 34 outputs a difference obtained by subtracting the detected steering angular velocity from the corrected target steering angular velocity input to itself as a steering angular velocity deviation to the multiplication units 35 and 36. The subtraction unit 34 can acquire the detected steering velocity, for example, from the target steering torque setting unit 51. The multiplication unit 35 multiplies the steering angular velocity deviation input from the subtraction unit 34 by a preset steering angle control proportional gain Kvp to output a steering angle control proportional term to the addition unit 39.

[0043] The multiplication unit 36 ​​multiplies the steering angle velocity deviation input from the subtraction unit 34 by a preset steering angle control integral gain Kvi, and outputs the resulting product to the steering angle integration unit 43. The steering angle integration unit 43 time-integrates the product input from the multiplication unit 36 ​​to obtain a steering angle control integral term Iia ０ The steering angle integral section 43 calculates the calculated steering angle control integral term Iia ０ The steering angle integral unit 43 outputs the steering angle control proportional term Iia input from the multiplication unit 35 to the addition unit 39. A specific example of the configuration and processing of the steering angle integral unit 43 will be described later. The addition unit 39 multiplies the steering angle control proportional term Iia input from the multiplication unit 35 and the steering angle control integral term Iia input from the steering angle integral unit 43 by the sum of the steering angle control proportional term Iia ０ and an electric signal indicating the sum obtained by adding the above and outputs it to the switching unit 23 as a steering angle control target current.

[0044] Next, we will explain an example configuration of the switching signal generation unit 27. Fig. 4 is a block diagram showing an example configuration of the switching signal generation unit 27 according to this embodiment. The switching signal generation unit 27 includes an absolute value processing unit 61, a switching determination unit 62, and a weight signal generation unit 63.

[0045] The absolute value processing unit 61 derives the absolute value of the detected steering torque input from the torque sensor 5 (hereinafter referred to as the "detected steering torque absolute value") and outputs the derived detected steering torque absolute value to the switching determination unit 62. The switching signal generation unit 27 may include a low-pass filter. The low-pass filter cuts off high-frequency components having frequencies higher than a predetermined cutoff frequency from the detected steering torque input from the torque sensor 5, and outputs low-frequency components having frequencies lower than the cutoff frequency to the absolute value processing unit 61 as the filtered detected steering torque. This prevents a phenomenon (chattering) in which the control method is unintentionally switched repeatedly at very short intervals.

[0046] A positive threshold value of the detected steering torque (hereinafter referred to as the "detected steering torque threshold value") is set in advance in the switching determination unit 62. The switching determination unit 62 compares the detected steering torque absolute value input from the absolute value processing unit 61 with the detected steering torque threshold value, and determines whether the detected steering torque absolute value is larger than the detected steering torque threshold value. When the detected steering torque absolute value is greater than the detected steering torque threshold value, the switching determination unit 62 outputs a signal indicating a value Trq indicating that torque control is active as a switching signal Sw to the weight signal generation unit 63, the torque control unit 20, the steering angle control unit 21, and the switching unit 23. Here, "active" means that the function is active. Conversely, Trq indicates that steering angle control is in a paused state. When the detected steering torque absolute value is smaller than the detected steering torque threshold value, the switching determination unit 62 outputs a signal indicating a value Ang that indicates that steering angle control is active as a switching signal Sw to the weight signal generation unit 63, the torque control unit 20, the steering angle control unit 21, and the switching unit 23. In other words, Ang indicates that torque control is in a pause state.

[0047] The weight signal generator 63 determines a weight for a predetermined one of the steering angle control and the torque control based on the switching signal Sw input from the switching determination unit 62. More specifically, the weight signal generator 63 monitors the switching signal Sw and determines whether the switching signal Sw indicates a value Trq indicating torque control or a value Ang indicating steering angle control. The weight signal generator 63 sets a predetermined period of time, starting from the switching time, as a gradual change period. The weight signal generator 63 identifies the time when the control method indicated by the switching signal Sw switches from one of the torque control and the steering angle control to the other as the switching time. The weight signal generator 63 determines the weight so that it changes continuously over time, such that the weight for the other method is 0 at the switching time and 1 at the post-gradual change time, which is the end of the gradual change period. That is, the weight for one method is 1 at the switching time, and the weight for the other method is 0 at the post-gradual change time. The sum of the weights for each control method is normalized to one.

[0048] However, the weight signal generator 63 uses the value of the switching signal Sw as the weight as is except during the gradual change period. That is, the weight signal generator 63 sets the weight for the other method, which is the method after switching, to 0 during the period preceding the switching time, and sets the weight for the other method to 1 after the gradual change time. The weight signal generator 63 outputs a weight signal Wt indicating the set weight to the torque controller 20 and the steering angle controller 21.

[0049] Next, an example of setting the weight signal Wt will be described. The second row of each of FIGS. 7 and 8 shows an example of setting the weight signal Wt. FIG. 7 illustrates a case where the switching signal indicates Trq during a period preceding switching time T0, switches from Trq to Ang at switching time T0, and continues to be Ang thereafter. During the period preceding switching time T0, the weight signal Wt indicates 0. During the gradual change period from switching time T0 to post-gradual change time T1, the value of the weight signal Wt increases linearly from 0 to 1 over time. During the period following post-gradual change time T1, the weight signal Wt indicates 1.

[0050] 8 illustrates an example in which the switching signal indicates Ang during a period preceding switching time T0, switches from Ang to Trq at switching time T0, and continues to indicate Trq thereafter. During the period preceding switching time T0, the weight signal Wt indicates 1. During the gradual change period from switching time T0 to post-gradual change time T1, the value of the weight signal Wt decreases linearly from 1 to 0 over time. During the period following post-gradual change time T1, the weight signal Wt indicates 0.

[0051] Next, an example of the configuration of the torque gradual-change unit 58 will be described. Fig. 5 is a block diagram showing an example of the configuration of the torque gradual-change unit 58 according to this embodiment. During a gradual-change period related to switching to torque control, the torque gradual-change unit 58 calculates, as the gradual-change target steering torque, the target steering torque adjusted so as to gradually change from the detected steering torque input from the torque sensor 5 to the original target steering torque input from the target steering torque setting unit 51, in accordance with the gradual change of the weight indicated by the weight signal Wt. Furthermore, during a gradual-change period related to switching to steering angle control, the torque gradual-change unit 58 calculates, as the gradual-change target steering torque, the target steering torque adjusted so as to gradually change from the original target steering torque to the detected steering torque, in accordance with the gradual change of the weight indicated by the weight signal Wt.

[0052] Gradual torque change unit 58 includes a subtraction unit 72, multiplication units 73 and 74, and an addition unit 75. Subtraction unit 72 calculates a difference obtained by subtracting the weight indicated by weight signal Wt from 1 as an inverted weight, and outputs an inverted weight signal indicating the inverted weight to multiplication unit 73. The inverted weight corresponds to a weight for torque control. Multiplication unit 73 multiplies the target steering torque by the inverted weight indicated by the inverted weight signal, and outputs the weighted target steering torque to addition unit 75.

[0053] Multiplication unit 74 multiplies the detected steering torque by the weight indicated in the weighting signal and outputs the weighted target steering torque to addition unit 75. The weight indicated in the weighting signal corresponds to the weight for steering angle control. Addition unit 75 outputs the sum of the weighted target steering torque input from multiplication unit 73 and the weighted target steering torque input from multiplication unit 74 to subtraction unit 52 as the gradually changed target steering torque.

[0054] Next, an example of the operation of the torque gradual-change unit 58 will be described. The third row of FIG. 8 shows the time change of the post-gradual-change target steering torque output from the torque gradual-change unit 58. In the period up to the switching time T0, the post-gradual-change target steering torque is equal to the detected steering torque (detected value). At the switching time T0, when the control method switches from steering angle control to torque control, the post-gradual-change target steering torque begins to linearly approach the target steering torque (target value), and at the post-gradual-change time T1, the post-gradual-change target steering torque reaches the target steering torque. In the period from the post-gradual-change time T1 onwards, the post-gradual-change target steering torque becomes equal to the target steering torque. That is, the post-gradual-change target torque gradually changes from the detected steering torque to the target steering torque in synchronization with the gradual change of the weight indicated by the weight signal Wt from 1 to 0 from the switching time T0 to the post-gradual-change time T1.

[0055] Next, an example of the configuration of the steering angle gradually-changing unit 41 will be described. Fig. 6 is a block diagram showing an example of the configuration of the steering angle gradually-changing unit 41 according to this embodiment. During a gradual-change period related to switching to steering angle control, the steering angle gradually-changing unit 41 calculates, as a gradually-changed target steering angle, a target steering angle adjusted so as to gradually change from the detected steering angle input from the steering angle detection unit 4 to the original target steering angle input from the higher-level controller 9, in accordance with the gradual change of the weight indicated by the weight signal Wt. Furthermore, during a gradual-change period related to switching to torque control, the steering angle gradually-changing unit 41 calculates, as a gradually-changed target steering angle, a target steering angle adjusted so as to gradually change from the original target steering angle to the detected steering angle, in accordance with the gradual change of the weight indicated by the weight signal Wt.

[0056] The steering angle gradual-change unit 41 includes a subtraction unit 82, multiplication units 83 and 84, and an addition unit 85. The subtraction unit 82 outputs an inverted weight signal indicating, as an inverted weight, a difference obtained by subtracting the weight indicated in the weight signal Wt from 1 to the multiplication unit 84. The multiplication unit 83 multiplies the target steering angle by the weight indicated in the weight signal and outputs the weighted target steering angle to the addition unit 85.

[0057] The multiplication unit 84 multiplies the detected steering torque by the inversion weight indicated in the inversion weight signal and outputs the inversion-weighted target steering torque to the addition unit 85. The addition unit 85 outputs the sum of the weighted target steering angle input from the multiplication unit 83 and the inversion-weighted detected steering angle input from the multiplication unit 84 to the subtraction unit 31 as the gradually changed target steering angle.

[0058] Next, an example of the operation of the steering angle gradually changing unit 41 will be described. The third row of FIG. 7 shows the time change of the post-gradual-change target steering angle output from the steering angle gradually changing unit 41. In the period up to switching time T0, the post-gradual-change target steering angle is equal to the detected steering angle (detected value). At switching time T0, when the control method switches from torque control to steering angle control, the post-gradual-change target steering angle begins to linearly approximate the target steering angle (target value), and at post-gradual-change time T1, the post-gradual-change target steering angle reaches the target steering angle. In the period after post-gradual-change time T1, the post-gradual-change target steering angle becomes equal to the target steering angle. In other words, the post-gradual-change target steering angle gradually changes from the detected steering angle to the target steering angle in synchronization with the gradual change of the weight indicated by the weight signal Wt from 0 to 1 from switching time T0 to post-gradual-change time T1.

[0059] 7 and 8 illustrate cases in which the detected value and the target value are constant, but they may not necessarily be constant. Even in such cases, the torque gradual-change unit 58 gradually changes the target steering torque between the detected value and the target value based on the weighting signal Wt, and the steering angle gradual-change unit 41 gradually changes the target steering angle between the detected value and the target value based on the weighting signal Wt. Since the target steering torque and the target control method change continuously over time during the gradual-change period starting from the point in time when the control method is switched, smooth switching of the control method is possible.

[0060] Returning to Fig. 3, an example of the configuration of the torque integrator 60 will be described. The torque integrator 60 includes an adder 56, a torque integral switch 59, and a delay unit 55. The adder 56 multiplies the torque control integral gain Kti input from the multiplier 54 by the torque deviation to obtain the torque control integral term Iit ０ The sum Iit obtained by adding the sum Iit to the torque integral switching unit 59 is output.

[0061] When the switching signal Sw input from the switching signal generating unit 27 indicates a value Trq representing torque control, the torque integral switching unit 59 outputs the added value input from the adding unit 56 as the output value Iit directly to the delay unit 55. The delay unit 55 delays the output value Iit input from the torque integral switching unit 59 by one control cycle, and outputs the delayed output value Iit as a new torque control integral term Iit０ The torque control integral term Iit ０ is updated by integrating the torque deviation multiplied value for each control period and then delaying it. The output value Iit is the next torque control integral term Iit ０ It can be considered as follows.

[0062] On the other hand, when the switching signal Sw input from the switching signal generating unit 27 indicates the value Ang representing the steering angle control, the torque integral switching unit 59 outputs the next steering angle control integral term Iia input from the steering angle integrator 43 to the delay unit 55. The delay unit 55 delays the output value Iia input from the torque integral switching unit 59 by one control cycle, and outputs the delayed output value Iia as a new torque control integral term Iit ０ to the adders 56 and 57. That is, when the switching signal Sw indicates that the torque control is inactive, the torque integrator 60 sets the value of the steering angle control integral term as the torque control integral term, and when the switching signal Sw indicates that the torque control is active, the torque integrator 60 applies the original torque control integral term as the torque control integral term.

[0063] Next, a configuration example of the steering angle integrator 43 will be described. The steering angle integrator 43 includes an adder 38, a steering angle integral switcher 42, and a delayer 37. The adder 38 multiplies the steering angle control integral gain Kvi input from the multiplier 36 by the steering angle deviation to obtain the steering angle control integral term Iia input from the delayer 37. ０ The sum Iia obtained by adding the sum Iia to the steering angle integral switching unit 42 is output.

[0064] When the switching signal Sw input from the switching signal generating unit 27 indicates the value Ang representing the steering angle control, the steering angle integral switching unit 42 outputs the added value input from the adding unit 38 as the output value Iia to the delay unit 37. This output value Iia is the next steering angle control integral term Iia ０ The delay unit 37 delays the output value Iia input from the steering angle integral switching unit 42 by one control period, and converts the delayed output value Iia into a new steering angle control integral term Iia a ０ The steering angle control integral term Iia is output to the adders 38 and 39. ０is updated by accumulating the multiplied value of the steering angle deviation for each control cycle and then delaying it.

[0065] When the switching signal Sw input from the switching signal generating unit 27 indicates a value Trq representing torque control, the steering angle integral switching unit 42 outputs the output value Iia input from the torque integrator 60 to the delay unit 37. The delay unit 37 delays the output value Iia input from the steering angle integral switching unit 42 by one control cycle, and outputs the delayed output value Iia as a new steering angle control integral term Iia ０ to the adders 38 and 39. That is, when the switching signal Sw indicates a paused state of the steering angle control, the steering angle integrator 43 sets the value of the torque control integral term as the steering angle control integral term, and when the switching signal Sw indicates an active state of the steering angle control, the steering angle integrator 43 applies the original steering angle control integral term as the steering angle control integral term.

[0066] Next, an example of the operation of the steering angle integral switching unit 42 will be described. In the example of FIG. 7, the control method switches from torque control to steering angle control at switching time T0. The steering angle integral switching unit 42 outputs the next torque control integral term Iit input from the torque integrator 60 to the delay unit 37 during a period preceding switching time T0. Therefore, the next torque control integral term Iit is delayed by the delay unit 37, and the current steering angle control integral term Iia is output. ０ is output as

[0067] On the other hand, in the period following the switching time T0, the steering angle integral switching unit 42 outputs the next steering angle control integral term Iia input from the adding unit 38 to the delay unit 37. Therefore, the next steering angle control integral term Iia is delayed by the delay unit 37, and the current steering angle control integral term Iia, which is the original steering angle control integral term, is output. ０ Therefore, as shown in the fourth row of FIG. 7, the steering angle control integral term Iia output from the steering angle integrator 43 is ０ are continuous at the switching time T0 when the control method is switched.

[0068] Next, an example of the operation of the torque integral switching unit 59 will be described. In the example of FIG. 8, the control method switches from steering angle control to torque control at switching time T0. During a period preceding switching time T0, the torque integral switching unit 59 outputs the next steering angle control integral term Iia input from the steering angle integrator 43 to the delay unit 55. Therefore, the next steering angle control integral term Iia is delayed by the delay unit 55, and the current torque control integral term Iit ０ is output as

[0069] On the other hand, in the period following the switching time T0, the torque integral switching unit 59 outputs the next torque control integral term Iit input from the adding unit 56 to the delay unit 55. Therefore, the next torque control integral term Iit is delayed by the delay unit 55, and the current torque control integral term Iit, which is the original torque control integral term, is output. ０ Therefore, as shown in the fourth row of FIG. 8, the torque control integral term Iit ０ are continuous at the switching time T0 when the control method is switched.

[0070] The control unit 11 may be configured to include dedicated hardware or a general-purpose computer system. The computer system includes one or more processors and one or more memories. The processor is, for example, a CPU (Central Processing Unit). The memory may include a volatile storage medium and a non-volatile storage medium. The processor executes processing instructed by commands written in a predetermined program, thereby realizing some or all of the functions of the control unit 11. The computer system may be, for example, a microcontroller.

[0071] The current control unit 26 includes the analog circuit described above. The current control unit 26 may be configured as hardware separate from the computer system of the control unit 11. Even in this case, the current control unit 26 operates under the control of the computer system of the control unit 11. The analog circuit of the current control unit 26 supplies current to the motor 6 so that the actual current value follows the target current output from the computer system having the function of the switching unit 23.

[0072] As described above, the steering control device 10 according to this embodiment includes a torque control unit 20 that outputs a torque control target current for driving the steering mechanism based on steering torque, and a steering angle control unit 21 that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and a target steering angle. The steering control device 10 also includes a switching unit 23 that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as a target current, and a driving unit 25 that applies torque to the steering mechanism based on the target current. The torque control unit 20 includes a torque integrator 60 that integrates a value based on the steering torque to derive a torque control integral term of the torque control target current. The steering angle control unit 21 also includes a steering angle integrator 43 that integrates a value based on the steering angle deviation to derive a steering angle control integral term of the steering angle control target current. When a switching signal instructs switching from torque control to steering angle control, the steering angle control unit 21 sets the torque control integral term as an initial value of the steering angle control integral term. When the switching signal instructs switching from steering angle control to torque control, the torque control unit 20 sets the steering angle control integral term as the initial value of the torque control integral term.

[0073] According to this configuration, when switching between torque control and steering angle control, one of the torque control unit 20 and steering angle control unit 21 switches from a dormant state to an active state, control is started with the value of the integral term in the other control unit as the initial value of the integral term of the one control unit after switching. This reduces or eliminates discontinuity in the target current to be supplied to the motor 6 before and after switching. Smooth switching of the target current allows the motor 6 and steering shaft 2 to behave smoothly without torque ripple or vibration.

[0074] The steering control device 10 according to this embodiment also includes a torque control unit 20 that outputs a torque control target current based on a torque deviation, which is the deviation between the steering torque acting on the steering mechanism and a target steering torque, a steering angle control unit 21 that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and the target steering angle, a target current output unit (e.g., a switching unit 23) that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as the target current, and a drive unit 25 that applies torque to the steering mechanism based on the target current. When the switching signal instructs switching from steering angle control to torque control, the torque control unit 20 continuously changes the target steering torque from the steering torque to the original target steering torque over a predetermined gradual change time, and when the switching signal instructs switching from torque control to steering angle control, the steering angle control unit 21 continuously changes the target steering angle from the steering angle to the original target steering angle over the gradual change time.

[0075] According to this configuration, when switching from one of the target steering torque control and the steering angle control to the other, the target value for the other control is temporarily set to the detected value, and the detected value gradually changes to the target value. As a result, the deviation that serves as the input to the control gradually changes from zero to the original deviation, and the other control is gradually initiated. As a result, the motor 6 and the steering shaft 2 behave smoothly without generating ripples or vibrations.

[0076] Furthermore, the torque control unit 20 may include a torque integrator 60 that integrates the torque deviation to derive the torque control integral term, and the steering angle control unit 21 may include a steering angle integrator 43 that integrates the steering angle deviation to derive the steering angle control integral term. When a switching signal instructs switching from torque control to steering angle control, the steering angle control unit 21 may set an initial value of the steering angle control integral term based on the torque control integral term, and when a switching signal instructs switching from steering angle control to torque control, the torque control unit 20 may set an initial value of the torque control integral term based on the steering angle control integral term.

[0077] According to this configuration, when switching from one of the target steering torque control and the steering angle control to the other, both the integral switching unit and the target value gradual change unit are provided. When the control unit for the other control switches from a dormant state to an active state, the value of the integral term of the control unit for one control can be used as the initial value of the integral term to start control. Furthermore, the other control unit temporarily sets the detected value as the target value at the time of switching and gradually changes it to the original target value. Since the deviation input to the control gradually changes from zero to the original deviation, the other control is gradually started. Therefore, the integral term is continuous before and after switching, and since the integral term gradually changes after switching, the proportional term also gradually changes. This further smooths the behavior of the motor 6 and the steering mechanism when switching between control methods.

[0078] Alternatively, the torque control unit 20 may output a torque control target current based on a torque deviation, which is the deviation between the detected steering torque and the target steering torque, and the torque integrator unit 60 may output a torque control integral term based on the torque deviation. With this configuration, the torque control unit realizes target steering torque control based on the target steering torque, and can coexist with steering angle control by setting the detected steering torque as the target steering torque. Therefore, a smooth transition to steering angle control can be realized without impairing the comfortable and robust operation feeling that is a feature of target steering torque control.

[0079] The steering control device 10 may also include a switching signal generator 27 that generates a switching signal according to the magnitude of the steering torque. This configuration accurately determines whether or not the driver intends to intervene in the steering, and contributes to smooth switching between torque control and steering angle control according to the determination result.

[0080] Furthermore, the steering angle control unit 21 may correct the steering angle deviation or the target steering angle velocity by adding a steering intervention correction value according to the steering torque, and calculate the steering angle control target current based on the corrected steering angle deviation or target steering angle velocity. With this configuration, even if there is steering intervention during steering angle control to an extent that the switching signal does not command switching to torque control, the target current is corrected using steering angle control. Even if an operation intervention occurs, the steering angle control continues and the operation of the motor 6 and the steering mechanism is smoothly controlled, thereby improving steering comfort without causing any discomfort to the driver.

[0081] <Embodiment 2> Next, Embodiment 2 of the present disclosure will be described, mainly focusing on the differences from Embodiment 1. For points in common with Embodiment 1, the description thereof will be used unless otherwise specified. FIG. 9 is a block diagram showing an example configuration of a torque control unit 20 and a steering angle control unit 21 according to this embodiment. In the steering control device 10 according to this embodiment, the steering angle control unit 21 further includes an integrating unit 44, and the multiplying unit 32 and the subtracting unit 34 (FIG. 3) are omitted. The integrating unit 44 is provided between the steering intervention correcting unit 40 and the adding unit 33. The steering angle gradual-change unit 41 outputs the target steering angle after gradual change to the adding unit 33.

[0082] The steering angle control unit 21 calculates a steering angle control target current based on a steering angle deviation Δθ, which is the difference between the target steering angle input from the higher-level controller 9 and the detected steering angle input from the steering angle detection unit 4. The steering intervention correction unit 40 performs phase compensation on the detected steering torque input from the torque sensor 5, and outputs a signal indicating a multiplied value obtained by multiplying the phase-compensated detected steering torque by a gain to the integrating unit 44. The integrating unit 44 time-integrates the multiplied value indicated by the signal input from the steering intervention correction unit 40, and outputs the integrated value obtained by the integration to the adding unit 33 as a steering intervention correction value.

[0083] The adder 33 calculates a corrected target steering angle by adding the steering intervention correction value to the gradually changed target steering angle input from the steering angle gradually changing unit 41. The adder 33 outputs the calculated corrected target steering angle to the subtracter 31. The subtracter 31 calculates the difference between the corrected target steering angle input from the adder 33 and the detected steering angle input from the steering angle detection unit 4 as the steering angle deviation Δθ. The subtracter 31 outputs the calculated steering angle deviation Δθ to the multipliers 35 and 36.

[0084] The multiplier 35 multiplies the steering angle deviation Δθ input from the subtractor 31 by the steering angle control proportional gain Kvp to calculate a steering angle control proportional term. The multiplier 35 outputs the calculated steering angle control proportional term to the adder 39. The multiplier 36 multiplies the steering angle deviation Δθ input from the subtractor 31 by the steering angle control integral gain Kvi to output the product to the steering angle integrator 43. The steering angle integrator 43 time-integrates the product input from the multiplier 36 to calculate the steering angle control integral term Iia ０ The steering angle integral section 43 calculates the calculated steering angle control integral term Iia ０ The adder 39 outputs the steering angle control proportional term input from the multiplier 35 and the steering angle control integral term Iia input from the steering angle integrator 43 to the adder 39. ０ and an electric signal indicating the sum obtained by adding the above and outputs it to the switching unit 23 as a steering angle control target current.

[0085] The steering angle control unit 21 may further include a differentiation unit and an addition unit (not shown). The differentiation unit outputs a differentiation value obtained by time-differentiating the steering angle deviation Δθ input from the subtraction unit 31 to the addition unit. The addition unit multiplies the differentiation value input from the differentiation unit by a preset steering angle control differentiation gain and outputs the resulting product to the addition unit 39 as a steering angle control differentiation term. The addition unit 39 may further add a steering angle control differentiation term to the steering angle control proportional term and the steering angle control integral term to determine the steering angle control target current.

[0086] With this configuration, even if there is steering intervention during steering angle control to an extent that the switching signal does not command switching to torque control, the target current is corrected using steering angle control. Even if steering intervention occurs, steering angle control can be continued to smoothly control the operation of the motor 6 and the steering mechanism, so that the driver does not feel any discomfort when steering.

[0087] <Embodiment 3> Next, a third embodiment of the present disclosure will be described, mainly focusing on differences from the first embodiment. The same description as in the first embodiment will be used for commonalities with the first embodiment unless otherwise specified. FIG. 10 is a block diagram showing exemplary configurations of a torque control unit 20 and a steering angle control unit 21 according to the present embodiment. In the steering control device 10 according to the present embodiment, the torque control unit 20 differs from the torque control unit 20 according to the first embodiment in that it is capable of performing normal assist control. Assist control is a method of setting a target assist current as a component of the target current so that the target current is approximately proportional to the steering torque. The torque control unit 20 according to the first embodiment is capable of performing target steering torque control. That is, the torque control unit 20 according to the present embodiment further includes an assist current setting unit 91 and a differentiating unit 90, and does not include the target steering torque setting unit 51 and the torque gradual change unit 58 (FIG. 3).

[0088] An assist map indicating the relationship between steering torque and target assist current is set in advance in the assist current setting unit 91. The target assist current is set so as to be approximately proportional to the steering torque. The assist current setting unit 91 references the assist map and outputs the target assist current corresponding to the steering torque input from the torque sensor 5 to the differentiating unit 90 and the subtracting unit 52. The target assist current may depend on the vehicle speed. In this case, the assist map may be configured to indicate the relationship between the target assist current and a set of steering torque and vehicle speed. The assist current setting unit 91 references the assist map and specifies the target assist current corresponding to the set of steering torque and vehicle speed input from the vehicle speed sensor 8.

[0089] The differentiating unit 90 calculates a target assist current differential value by time differentiating the target assist current input from the assist current setting unit 91. The differentiating unit 90 outputs the calculated target assist current differential value to the multiplying unit 53. The multiplying unit 53 multiplies the target assist current differential value input from the differentiating unit 90 by a preset torque control differential gain Ktd to obtain a torque control differential term, and outputs the result to the adding unit 57.

[0090] Subtraction unit 52 outputs a difference value obtained by subtracting the torque control integral term input from torque integrator 60 from the target assist current input from assist current setting unit 91 to multiplier 54. Multiplier 54 multiplies the difference value input from subtraction unit 52 by torque control proportional gain Ktp and outputs the multiplied value to torque integrator 60. Torque integrator 60 time-integrates the multiplied value input from multiplier 54 and outputs the integrated value as the torque control integral term to subtractor 52 and adder 57. Adder 57 adds the torque control integral term input from torque integrator 60 and the torque control differential term input from multiplier 53, and outputs an electrical signal indicating the sum to switch 23 as the torque control target current.

[0091] Here, the subtractor 52, the multiplier 54, and the torque integrator 60 constitute a low-pass filter for the target assist current. That is, the torque control integral term output from the torque integrator 60 contains low-frequency low-current components, and therefore mainly contains DC components. The torque control proportional gain Ktp is set to a value corresponding to the cutoff frequency of the low-pass filter. Note that the process related to switching the control method in the torque integrator 60 in this embodiment may be the same as the process in the first embodiment.

[0092] As described above, the torque control integral term mainly contains the DC component of the target assist current, whereas the torque control differential term contributes to stabilizing the control system and suppressing disturbances. Therefore, when torque control is active, the torque control unit 20 according to this embodiment functions similarly to normal assist control. The torque integrator 60 according to this embodiment also includes the torque integral switching unit 59, so that the integral term is shared with the steering angle control unit 21 as described above. This enables smooth switching between control methods. However, because the torque control unit 20 according to this embodiment does not perform target value tracking control, the torque gradual changer 58 is not essential, unlike the torque control unit 20 according to the first embodiment.

[0093] 10 illustrates an example of a configuration in which the torque control unit 20 determines the torque control target current as the sum of a differential term based on the differential value of the target assist current output from the assist current setting unit 91 and an integral term based on the low-pass component of the target assist current, but this is not limiting. For example, the torque control unit 20 may further include a low-pass filter, which outputs the low-pass component of the differential value of the target assist current to the multiplication unit 53. A circuit formed by connecting the differentiation unit 90 and the low-pass filter in series is equivalent to a high-pass filter. In other words, the multiplied value output from the multiplication unit 53 corresponds to the high-pass component of the target assist current. Therefore, the torque control unit 20 is configured equivalent to a phase compensator for the target assist current. Therefore, the torque control unit 20 according to this embodiment can function as a torque control unit based on normal assist control and can smoothly switch between control methods.

[0094] <Fourth Embodiment> Next, a fourth embodiment of the present disclosure will be described, mainly focusing on differences from the first embodiment. The same points as those in the first embodiment will be referred to unless otherwise specified. FIG. 11 is a block diagram showing exemplary configurations of a torque control unit 20 and a steering angle control unit 21 according to this embodiment. In the steering control device 10 according to this embodiment, the torque control unit 20 outputs a torque control target current It to the steering angle control unit 21, and the steering angle control unit 21 outputs a steering angle control target current Ia to the torque control unit 20. In this respect, the fourth embodiment differs from the torque control unit 20 and the steering angle control unit 21 ( FIG. 3 ) according to the first embodiment. The torque control unit 20 according to the first embodiment outputs a next torque control integral term Iit to the steering angle control unit 21, and the steering angle control unit 21 outputs a next steering angle control integral term Iia to the torque control unit 20.

[0095] In this embodiment, the steering angle control target current Ia is input to the torque integral switching unit 59 from the steering angle control unit 21 instead of the steering angle control integral term Iia. The torque control target current It is input to the steering angle integral switching unit 42 from the torque control unit 20 instead of the torque control integral term Iit. The target current includes an integral term in which a DC component is dominant and a proportional term, and therefore is closer to the integral term one control cycle later than the latest integral term obtained up to that point. Therefore, the input target current can more accurately reflect the value of the integral term controlled by the other control unit immediately before switching the control method.

[0096] That is, when a switching signal instructs switching from torque control to steering angle control, the steering angle integral switching unit 42 sets the torque control target current It, which is a value based on the torque control integral value, as the initial value of the steering angle control integral term. When a switching signal instructs switching from steering angle control to torque control, the torque integral switching unit 59 sets the steering angle control target current Ia, which is a value based on the steering angle control integral value, as the initial value of the torque control integral term. Therefore, the value of the target current including the integral term immediately before switching is reflected in the integral term in the control unit related to the control after switching. This enables smoother control switching.

[0097] The torque control unit 20 may include a torque control target current smoothing unit (not shown) that smooths the torque control target current It, and may output the smoothed torque control target current It to the steering angle control unit 21. The steering angle control unit 21 may include a steering angle control target current smoothing unit (not shown) that smooths the steering angle control target current Ia, and may output the smoothed steering angle control target current Ia to the torque control unit 20. The torque control target current smoothing unit and the steering angle control target current smoothing unit may each perform low-pass filtering, moving average processing, or the like. This suppresses high-frequency components or high-frequency noise contained in the torque control target current It and the steering angle control target current Ia.

[0098] High-frequency components with frequencies higher than the steering frequency associated with steering the steering wheel 1 may cause discomfort to the driver. By preventing the transfer of target current from one control unit to the other, the discomfort can be reduced or avoided. Furthermore, blocking high-frequency components smooths the behavior of the motor 6 and steering mechanism associated with switching of the control method. Note that smoothing is not required for the integral term as in the first embodiment. This is because the integral value mainly contains low-frequency components.

[0099] <Fifth Embodiment> Next, the fifth embodiment of the present disclosure will be described, mainly focusing on differences from the first embodiment. The description of the first embodiment will be used for commonalities with the first embodiment unless otherwise specified. The steering control device 10 according to this embodiment has the same functional configuration as the steering control device 10 according to the first embodiment. However, in this embodiment, when the control unit related to the control to be activated switches from one of the torque control unit 20 and the steering angle control unit 21 to the other, one control unit outputs the final value of the integral term at that time to the other control unit, and the other control unit sets the integral term input from one control unit as the initial value of the integral term. During other periods, there is no need to output the integral term from one control unit to the other control unit. In other words, the timing of the transfer of the integral term is limited to the time of control switching, and the target of the transfer is the final value of the integral value of one control unit immediately before the switching time.

[0100] Next, an example of integral term transfer accompanying control method switching will be described. FIG. 12 is an explanatory diagram showing an example of integral term transfer according to this embodiment. FIG. 12 illustrates a case where the active control method switches from torque control to steering angle control at switching time T0. The control method indicated by the switching signal at switching time T0 changes from Ang to Trq. The weighting coefficient changes from 0 to 1 from switching time T0 to post-gradual change time T1. Until switching time T0 is reached, the torque integrator 60 calculates the torque control integral term Iit ０However, it is not necessary to output this to the steering angle control unit 21. When the torque integral switching unit 59 determines that the switching time T0 has been reached based on the switching signal Sw, it delays Iit_n, which is the next value of the latest torque control integral term at that time, using the delay unit 55 and outputs it as the torque control integral term to the steering angle control unit 21. At this time, the steering angle integrator 43 sets the torque control integral term Iit_n input from the torque control unit 20 as the initial value of the steering angle control integral term and starts calculating the steering angle control integral term. Thereafter, in the active state of steering angle control, the steering angle control integral term is sequentially output from the steering angle integrator 43.

[0101] Sixth Embodiment Next, a sixth embodiment of the present disclosure will be described, mainly focusing on the differences from the second embodiment. For points in common with the second embodiment, the description thereof will be used unless otherwise specified. As illustrated in Fig. 13 , the steering control device 10 according to this embodiment includes an adder 28 instead of the switching unit 23 (Fig. 1). The adder 28 adds the torque control target current input from the torque control unit 20 and the steering angle control target current input from the steering angle control unit 21 to obtain an electrical signal, and outputs the electrical signal to the drive unit 25 as a target current.

[0102] 14 , in the steering angle control unit 21 according to this embodiment, the steering intervention correction unit 40 calculates a weighted multiplication value by further multiplying a multiplication value obtained by multiplying the phase-compensated detected steering torque by a gain by the weight indicated by the weight signal Wt input from the switching signal generation unit 27. The steering intervention correction unit 40 outputs the calculated weighted multiplication value to the integrating unit 44.

[0103] Therefore, when the switching signal Sw indicates the pause state of the steering control, the steering intervention correction value also becomes zero in synchronization with the weighting coefficient becoming zero. Moreover, after the switching signal Sw indicates the pause state of the steering control and the weighting coefficient gradually changes from 1 to zero, the steering angle control target current output from the steering angle control unit 21 becomes zero.

[0104] The reason for this is that after the weighting coefficient is gradually changed, the steering angle control unit 21 applies the detected steering angle as the target steering angle, and the steering angle deviation Δθ becomes zero. The steering angle control proportional term calculated in the subsequent stages and the input value to the steering angle integral unit 43 also become zero. Here, the timing of passing the integral term is limited to the switching time, as in the fifth embodiment. Then, the control unit in the pause state resets the value of the integral term to zero. Since the steering angle control integral term in the pause state of steering angle control also becomes zero, the steering angle control target current, which is the sum of the steering angle control proportional term and the steering angle control integral term, also becomes zero.

[0105] On the other hand, after the switching signal Sw indicates the active state of steering control and the weighting coefficient gradually changes from zero to one, the torque control unit 20 applies the detected steering torque as the target steering torque, and the torque deviation becomes zero. The torque control proportional term calculated in the subsequent stages and the input value to the torque integrator unit 60 also become zero. The timing of delivery of the integral term is limited to the switching time, as in the fifth embodiment, and the control unit in the inactive state resets the value of the integral term to zero. Since the torque control integral term in the inactive state of torque control also becomes zero, the torque control target current, which is the sum of the torque control proportional term and the torque control integral term, also becomes zero.

[0106] Therefore, in the pause state, the detected value gradually changes to the target value, and the weighted multiplication value obtained by the steering intervention correction unit 40 also gradually changes to zero, so the target current from the control unit related to the control in the pause state also becomes zero. Therefore, even if the sum of the torque control target current and the steering control target current obtained by the adder 28 is supplied as the target current to be supplied to the motor 6 without switching the target current by the switching unit 23 as described in the first and second embodiments, the target power obtained by one of the controls is substantially supplied to the motor 6. Furthermore, even if either the steering angle control unit 21 or the torque control unit 20 to which the steering angle gradual change unit 41 or the torque gradual change unit 58 belongs switches to the pause state, the target current supplied from the either unit also gradually changes to zero. Therefore, the motor 6 and the steering mechanism behave smoothly when the control method is switched.

[0107] As described above, the steering control device 10 according to this embodiment includes the torque control unit 20 that outputs a torque control target current based on a torque deviation, which is the deviation between the steering torque acting on the steering mechanism and a target steering torque, the steering angle control unit 21 that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and the target steering angle, a target current output unit (e.g., the adder 28) that outputs the sum of the torque control target current and the steering angle control target current as a target current, and the drive unit 25 that applies torque to the steering mechanism based on the target current. When a switching signal instructs switching from steering angle control to torque control, the torque control unit 20 continuously changes the target steering torque from the steering torque to the original target steering torque over a predetermined gradual-change time, and when a switching signal instructs switching from torque control to steering angle control, the steering angle control unit 21 continuously changes the target steering angle from the steering angle to the original target steering angle over the gradual-change time.

[0108] According to this configuration, when switching from one of the target steering torque control and the steering angle control to the other, the target value for the other control is temporarily set to the detected value, and the detected value gradually changes to the target value. As a result, the deviation that serves as the input to the control gradually changes from zero to the original deviation, and the other control is gradually initiated. As a result, the motor 6 and the steering shaft 2 behave smoothly without generating ripples or vibrations.

[0109] <Seventh Embodiment> Next, differences between a seventh embodiment of the present disclosure and the above-described embodiments will be described. For commonalities with the above-described embodiments, the description thereof will be used unless otherwise specified. As illustrated in FIG. 15 , the control unit 11 according to this embodiment may be realized as a steering control device. The steering control device according to this embodiment is configured by omitting the motor 6 from the steering control device according to any one of the first to sixth embodiments. The control unit 11 may be realized, for example, as part of a function of an electronic control unit (ECU).

[0110] The steering control system S1 according to this embodiment includes a control unit 11, a steering angle detection unit 4, and a torque sensor 5. The steering control system S1 may include a motor 6. The steering control system S2 according to this embodiment includes the steering control system S1 and a host controller 9. The steering angle detection unit 4 and the torque sensor 5 may be omitted from the steering control system S2. The steering control system S2 may also include the motor 6.

[0111] The host controller 9 may be configured as a driving assistance system having an automatic steering control function as described above. A computer system may be shared by the host controller 9 and the control unit 11. That is, some of the resources of the computer system may be used to implement the control unit 11, and other resources may be used to implement the host controller 9. The steering control system S2 may be configured to include a computer system having one or more processors and a memory. The processor reads a program non-temporarily stored in the memory and executes processing instructed by commands written in the read program, thereby implementing the functions of each part of the control unit 11 and the host controller 9. The computer system may be realized as an electronic control device.

[0112] The vehicle V1 according to this embodiment is equipped with an electric power steering device PS (FIG. 1). That is, the vehicle V1 is equipped with a steering control device 10 and a steering mechanism. In FIG. 15, the steering mechanism elements are exemplified by a steering shaft 2, steered wheels 3, and a reduction mechanism 7. The vehicle V1 may or may not be equipped with a host controller 9.

[0113] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments or modified examples, and can be freely modified within the scope of the present disclosure. For example, the electric power steering device PS according to the above-described embodiments may be a column-type or a rack-and-pinion-type. Furthermore, the host controller 9 may also be applied to other functions, such as a steer-by-wire steering reaction force function, as long as it has the function of executing steering angle control based on a target steering angle. In the above description, an example is given in which the steering control device 10 acquires a target steering angle from the host controller 9, but the steering control device 10 may also have the function of calculating the target steering angle.

[0114] Furthermore, the figures used in the description of the above-described embodiments are merely examples and are not intended to be limiting. The direction of arrows in block diagrams and other drawings is for the convenience of explanation and does not limit the direction of the flow of information, data, signals, etc. during implementation. Furthermore, the present disclosure is not limited by the above description, but is limited by the scope of the appended claims.

[0115] According to the steering control device 10, steering control system S1, electric power steering device PS or vehicle V1 of the present disclosure, smooth switching between torque control and steering angle control can be realized.

[0116] 1...Steering wheel, 2...Steering shaft, 5...Torque sensor, 6...Motor, 10...Steering control device, 11...Control unit, 20...Torque control section, 21...Steering angle control section, 23...Switching section, 25...Drive section, 28...Adding section, Sw...Switching signal, Wt...Weighting signal, 58...Torque gradual change section, 41...Steering angle gradual change section, Δθ...Steering angle deviation, Iit...Next value of torque control integral term, Iito...Current value of torque control integral term, Iia...Next value of steering angle control integral term, Iiao...Current value of steering angle control integral term, 60...Torque integration section, 43...Steering angle integration section, S1, S2...Steering control system, PS...Electric power steering device, V1...Vehicle

Claims

1. A steering control device comprising: a torque control unit that outputs a torque control target current for driving a steering mechanism based on steering torque; a steering angle control unit that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and a target steering angle; a switching unit that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as a target current; and a driving unit that applies torque to the steering mechanism based on the target current, wherein the torque control unit comprises a torque integration unit that integrates a value based on the steering torque to derive a torque control integral term of the torque control target current, and the steering angle control unit comprises a steering angle integration unit that integrates a value based on the steering angle deviation to derive the steering angle control integral term of the steering angle control target current, and when the switching signal instructs switching from torque control to steering angle control, the steering angle control unit sets an initial value of the steering angle control integral term based on the torque control integral term, and when the switching signal instructs switching from steering angle control to torque control, the torque control unit sets an initial value of the torque control integral term based on the steering angle control integral term. A steering control device characterized by:

2. A steering control device comprising: a torque control unit that outputs a torque control target current based on a torque deviation, which is the deviation between the steering torque acting on the steering mechanism and a target steering torque; a steering angle control unit that calculates a steering angle control target current based on a steering angle deviation, which is the deviation between the steering angle of the steering mechanism and a target steering angle; a target current output unit that selects one of the torque control target current and the steering angle control target current in response to a switching signal and outputs the selected current as the target current, or outputs the sum of the torque control target current and the steering angle control target current as the target current; and a drive unit that applies torque to the steering mechanism based on the target current, wherein when the switching signal commands switching from steering angle control to torque control, the torque control unit continuously changes the target steering torque from the steering torque to an original target steering torque over a predetermined gradual change time, and when the switching signal commands switching from torque control to steering angle control, the steering angle control unit continuously changes the target steering angle from the steering angle to the original target steering angle over the gradual change time.

3. A steering control device according to claim 2, characterized in that: the torque control section comprises a torque integrator section that integrates the torque deviation to derive a torque control integral term; the steering angle control section comprises a steering angle integrator section that integrates the steering angle deviation to derive a steering angle control integral term; when the switching signal instructs switching from torque control to steering angle control, the steering angle control section sets an initial value of the steering angle control integral term based on the torque control integral term; and when the switching signal instructs switching from steering angle control to torque control, the torque control section sets an initial value of the torque control integral term based on the steering angle control integral term.

4. A steering control device according to claim 1 or claim 3, characterized in that when the switching signal indicates a pause state of torque control, the torque control section sets the torque control integral term based on the steering angle control integral term, and when the switching signal indicates a pause state of steering angle control, the steering angle control section sets the steering angle control integral term based on the torque control integral term.

5. A steering control device according to claim 1, characterized in that the torque control unit outputs the torque control target current based on a torque deviation, which is the deviation between the steering torque and a target steering torque, and the torque integration unit outputs the torque control integral term based on the torque deviation.

6. A steering control device according to any one of claims 1 to 5, further comprising a switching signal generating unit that generates the switching signal in accordance with the magnitude of the steering torque.

7. A steering control device according to any one of claims 1 to 6, characterized in that the steering angle control unit corrects the steering angle deviation or the target steering angular velocity by adding a steering intervention correction value according to the steering torque, and calculates a steering angle control target current based on the corrected steering angle deviation or the target steering angular velocity.

8. A steering control system comprising: a steering torque detection unit that detects the steering torque; a steering angle detection unit that detects the steering angle; and the steering control device according to any one of claims 1 to 7.

9. A steering control system comprising: a driving assistance system having an automatic steering control function; and a steering control device according to any one of claims 1 to 7.

10. An electric power steering device comprising: the steering mechanism; and the steering control device according to any one of claims 1 to 7.

11. A vehicle equipped with the electric power steering device according to claim 10.

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