JP2020192927A - Vehicle steering device - Google Patents

Abstract

To provide a vehicle steering device that is able to improve feeling of steering.SOLUTION: A vehicle steering device has a drive mode (a first mode) and a low-speed drive mode (a second mode), as drive modes for the vehicle. In a predetermined area where the absolute value |θh| of the steering angle θh of a handle is equal to or larger than zero, a rate of change of target steering torque Tref in the low-speed drive mode (the second mode) is equal to or higher than that in the drive mode (the first mode). In areas other than the predetermined area, a rate of change of target steering torque Tref in the low-speed drive mode (the second mode) is lower than that in the drive mode (the first mode).SELECTED DRAWING: Figure 14

Description

The present invention relates to a steering device for a vehicle.

The electric power steering device (EPS), which is one of the steering devices for vehicles, applies an assist force (steering assist force) to the steering system of the vehicle by the rotational force of the motor. The EPS applies the driving force of the motor controlled by the electric power supplied from the inverter to the steering shaft or the rack shaft as an assisting force by a transmission mechanism including a reduction mechanism.

For example, a power steering device that gradually increases the steering assist force during low-speed operation such as garage entry operation and gradually returns the increased steering assist force to the normal steering assist force when the garage entry is completed is disclosed. (For example, Patent Document 1).

Patent No. 3891275

Generally, control is performed to reduce the steering assist force during low-speed operation. However, when the steering assist force is uniformly reduced during low-speed driving, it becomes difficult for the driver to recognize the steering angle at which the steering angle is close to zero. In particular, when the vehicle is being moved backward (backward) in order to park the vehicle in a parking area or the like, it becomes difficult for the driver to grasp the steering feeling when visually checking the safety behind the vehicle.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a steering device for a vehicle capable of improving a steering feeling.

In order to achieve the above object, the vehicle steering device according to one aspect of the present invention is a vehicle steering device that assists and controls the steering system of the vehicle by driving and controlling a motor that assists the steering force. The second mode has a first mode and a second mode different from the first mode as the driving mode of the vehicle, and in a predetermined region where the absolute value of the steering angle of the steering wheel is zero or more. The rate of change of the target steering torque of the motor in the first mode is equal to or higher than that of the first mode, and the rate of change of the target steering torque in the second mode is smaller than that of the first mode in a region other than the predetermined region.

As a desirable mode of the vehicle steering device, when a predetermined predetermined operation is detected, the determination unit for determining the second mode and the rate of change gradually increase as the absolute value of the steering angle of the handle increases. A first torque signal that increases along a smaller curve is generated, and a third torque signal is generated by multiplying the second torque signal generated based on the first torque signal by a correction gain to generate the third torque signal. On the other hand, a target steering torque generating unit that adds a fourth torque signal to generate the target steering torque is provided, and the target steering torque generating unit produces a positive correction gain of less than 1 in the second mode. It is preferable to generate a fourth torque signal whose inclination is larger than that of the first torque signal when the absolute value of the steering angle is zero.

According to the above configuration, the burden on the driver in the second mode can be reduced, and the steering feeling can be improved.

As a desirable embodiment of the steering device for a vehicle, it is preferable that the fourth torque signal in the second mode has a constant value in a region where the steering angle is equal to or more than a predetermined value.

As a result, the target steering torque in the second mode can be reduced, and the operation of the steering wheel can be lightened.

As a desirable embodiment of the vehicle steering device, it is preferable that the target steering torque generating unit sets the correction gain to 1 and the fourth torque signal to zero in the first mode.

As a result, a target steering torque suitable for the first mode can be obtained.

As a desirable embodiment of the vehicle steering device, the target steering torque in the second mode is smaller than the target steering torque in the first mode.

As a result, the operation of the handle can be lightened.

According to the present invention, it is possible to provide a steering device for a vehicle that can improve the steering feeling.

FIG. 1 is a diagram showing a general configuration of an electric power steering device. FIG. 2 is a schematic view showing a hardware configuration of a control unit that controls an electric power steering device. FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in an electric power steering device. FIG. 4 is a structural diagram showing an installation example of the steering angle sensor. FIG. 5 is a diagram showing an example of an internal block configuration of the control unit according to the first embodiment. FIG. 6 is an explanatory view of the steering direction. FIG. 7 is a flowchart showing an operation example of the control unit according to the first embodiment. FIG. 8 is a block diagram showing a configuration example of the target steering torque generating unit of the first embodiment. FIG. 9 is a diagram showing a characteristic example of the basic map held by the basic map unit. FIG. 10 is a diagram showing a characteristic example of the damper gain map held by the damper gain map unit. FIG. 11 is a diagram showing a characteristic example of the hysteresis correction unit. FIG. 12 is a block diagram showing a configuration example of the steering reaction force correction unit. FIG. 13 is a diagram showing an example of a correction torque map. FIG. 14 is a diagram showing an example of the target steering torque output from the target steering torque generation unit. FIG. 15 is a block diagram showing a configuration example of the twist angle control unit of the first embodiment. FIG. 16 is a diagram showing an example of an internal block configuration of the control unit according to the second embodiment. FIG. 17 is a block diagram showing a configuration example of the target steering torque generation unit of the second embodiment. FIG. 18 is a block diagram showing a configuration example of the SAT information correction unit. FIG. 19 is an image diagram showing a state of torque generated between the road surface and the steering wheel. FIG. 20 is a diagram showing a characteristic example of the steering torque sensitive gain. FIG. 21 is a diagram showing a characteristic example of the vehicle speed sensitive gain. FIG. 22 is a diagram showing a characteristic example of the steering angle sensitive gain. FIG. 23 is a diagram showing an example of setting the upper limit value and the lower limit value of the torque signal in the limiting portion. FIG. 24 is a block diagram showing a configuration example of the twist angle control unit of the second embodiment. FIG. 25 is a diagram showing a configuration example of the SBW system corresponding to the general configuration of the electric power steering device shown in FIG. FIG. 26 is a block diagram showing an internal block configuration of the control unit according to the third embodiment. FIG. 27 is a diagram showing a configuration example of the target steering angle generation unit. FIG. 28 is a diagram showing a configuration example of the steering angle control unit. FIG. 29 is a flowchart showing an operation example of the third embodiment.

Hereinafter, embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In addition, the components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, that is, those in a so-called equal range. Further, the components disclosed in the following embodiments can be appropriately combined.

(Embodiment 1)
FIG. 1 is a diagram showing a general configuration of an electric power steering device. The electric power steering device (EPS), which is one of the steering devices for vehicles, has a column shaft (steering shaft, steering shaft) 2, a reduction mechanism 3, and a universal joint of the steering wheel 1 in the order in which the force given by the steering wheel is transmitted. It is connected to the steering wheels 8L and 8R via 4a and 4b, a pinion rack mechanism 5, tie rods 6a and 6b, and further via hub units 7a and 7b. Further, the column shaft 2 having the torsion bar is provided with a torque sensor 10 for detecting the steering torque Ts of the steering wheel 1 and a steering angle sensor 14 for detecting the steering angle θh, and is a motor that assists the steering force of the steering wheel 1. 20 is connected to the column shaft 2 via the reduction mechanism 3. Electric power is supplied from the battery 13 to the control unit (ECU) 30 that controls the electric power steering device, and an ignition key signal is input via the ignition key 11. The control unit 30 calculates the current command value of the assist (steering assistance) command based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and compensates the current command value. The current supplied to the motor 20 is controlled by the voltage control command value Vref.

An in-vehicle network such as a CAN (Controller Area Network) 40 that exchanges various vehicle information is connected to the control unit 30. Further, a non-CAN 41 that transmits / receives communications other than CAN 40, analog / digital signals, radio waves, and the like can also be connected to the control unit 30.

The control unit 30 is mainly composed of a CPU (including an MCU, an MPU, etc.). FIG. 2 is a schematic view showing a hardware configuration of a control unit that controls an electric power steering device.

The control computer 1100 constituting the control unit 30 includes a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, a RAM (Random Access Memory) 1003, an EEPROM (Electrically Erasable Programmable ROM) 1004, and an interface (I / F). ) 1005, A / D (Analog / Digital) converter 1006, PWM (Pulse Width Modulation) controller 1007, etc., which are connected to the bus.

The CPU 1001 is a processing device that controls the electric power steering device by executing a computer program for controlling the electric power steering device (hereinafter referred to as a control program).

The ROM 1002 stores a control program for controlling the electric power steering device. Further, the RAM 1003 is used as a work memory for operating the control program. The EEPROM 1004 stores control data and the like input and output by the control program. The control data is used on the control computer program expanded in the RAM 1003 after the power is turned on to the control unit 30, and is overwritten on the EEPROM 1004 at a predetermined timing.

The ROM 1002, RAM 1003, EEPROM 1004, and the like are storage devices for storing information, and are storage devices (primary storage devices) that can be directly accessed by the CPU 1001.

The A / D converter 1006 inputs signals such as a steering torque Ts, a current detection value Im of the motor 20, and a steering angle θh, and converts them into digital signals.

Interface 1005 is connected to CAN 40. The interface 1005 is for receiving a vehicle speed V signal (vehicle speed pulse) from the vehicle speed sensor 12.

The PWM controller 1007 outputs PWM control signals for each phase of UVW based on the current command value for the motor 20.

FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in an electric power steering device. The steering torque Ts and the vehicle speed Vs are input to the current command value calculation unit 31. The current command value calculation unit 31 refers to a look-up table (assist map, etc.) stored in advance based on the steering torque Ts and the vehicle speed Vs, and refers to the current command value Iref1 which is a control target value of the current supplied to the motor 20. Is calculated.

The compensation signal generation unit 34 generates a compensation signal CM. The compensation signal generation unit 34 includes an astringent estimation unit 341, an inertial estimation unit 342, and a self-aligning torque (SAT: Self Aligning Torque) estimation unit 343. The astringent estimation unit 341 estimates the yaw rate of the vehicle based on the angular velocity of the motor 20, and estimates the compensation value for improving the yaw astringent of the vehicle by braking the swinging motion of the handle 1. The inertia estimation unit 342 estimates the inertial force of the motor 20 based on the angular acceleration of the motor 20, and estimates the compensation value for compensating for the inertial force of the motor 20 in order to improve the responsiveness. The SAT estimation unit 343 estimates the self-aligning torque T _SAT based on the steering torque Ts, the assist torque, the angular velocity and the angular acceleration of the motor 20, and uses the self-aligning torque as a reaction force to compensate the assist torque. presume. The compensation signal generation unit 34 may include an estimation unit that estimates other compensation values in addition to the astringent estimation unit 341, the inertia estimation unit 342, and the SAT estimation unit 343. In the compensation signal CM, the compensation value of the inertia estimation unit 342 and the compensation value of the SAT estimation unit 343 are added in the addition unit 344, and this addition value and the compensation value of the convergence estimation unit 341 are added in the addition unit 345. Is the added value. In the present disclosure, the self-aligning torque T _SAT estimated by the SAT estimation unit 343 is also output to the target steering torque generation unit 200, which will be described later.

In the addition unit 32A, the compensation signal CM from the compensation signal generation unit 34 is added to the current command value Inertia, and by adding the compensation signal CM, the characteristics of the steering system system are compensated to the current command value Inertia, and the convergence property is improved. It is designed to improve inertial characteristics and the like. Then, the current command value Iref1 becomes the characteristic-compensated current command value Iref2 via the addition unit 32A, and the current command value Iref2 is input to the current limiting unit 33. In the current limiting unit 33, the maximum current of the current command value Iref2 is limited, and the current command value Ireffm is generated. The current command value Ireffm is input to the subtraction unit 32B, and the deviation I (Irefm-Im) from the current detection value Im fed back from the motor 20 side is calculated by the subtraction unit 32B. The deviation I is input to the PI control unit 35 for improving the characteristics of the steering operation. Then, the voltage control command value Vref whose characteristics have been improved by the PI control unit 35 is input to the PWM control unit 36, and the motor 20 is PWM-driven via the inverter circuit 37 as the motor drive unit. The current detection value Im of the motor 20 is detected by the current detector 38 and fed back to the subtraction unit 32B. Further, in the inverter circuit 37, a field effect transistor (Field Effect Transistor: (hereinafter, referred to as FET)) is used as a driving element, and the inverter circuit 37 is composed of a bridge circuit of the FET.

In the assist control of the conventional electric power steering device, the steering torque applied manually by the driver is detected by the torque sensor as the torsion torque of the torsion bar, and the motor current is mainly used as the assist current according to the torque. I'm in control. However, when the control is performed by this method, the steering torque may differ depending on the steering angle due to the difference in the road surface condition (for example, inclination). The steering torque may also be affected by variations in the motor output characteristics due to aging.

FIG. 4 is a structural diagram showing an installation example of the steering angle sensor.

The column shaft 2 is provided with a torsion bar 2A. Road surface reaction force Rr and road surface information (friction resistance μ of the road surface) act on the steering wheels 8L and 8R. An upper angle sensor is provided on the handle side of the column shaft 2 with the torsion bar 2A sandwiched between them. A lower angle sensor is provided on the steering wheel side of the column shaft 2 with the torsion bar 2A sandwiched between them. The upper angle sensor detects the handle angle θ ₁ , and the lower angle sensor detects the column angle θ ₂ . The steering angle θh is detected by a steering angle sensor provided on the upper part of the column shaft 2. Torsion angle Δθ of the torsion bar from the deviation of the steering wheel angle theta ₁ and column angle theta _2, represented by the following equation (1). Further, the torsion bar torque Tt is expressed by the following equation (2) using the torsion angle Δθ of the torsion bar expressed by the equation (1). Kt is the spring constant of the torsion bar 2A.

Δθ = θ ₂ −θ ₁ ... (1)

Tt = −Kt × Δθ ... (2)

The torsion bar torque Tt can also be detected using a torque sensor. In the present embodiment, the torsion bar torque Tt is also treated as the steering torque Ts.

FIG. 5 is a diagram showing an example of an internal block configuration of the control unit according to the first embodiment.

The control unit 30 includes a target steering torque generation unit 200, a torsion angle control unit 300, a steering direction determination unit 400, and a conversion unit 500 as an internal block configuration.

In the present embodiment, the steering wheel steering of the driver is assist-controlled by the motor 20 of the EPS steering system / vehicle system 100. The EPS steering system / vehicle system 100 includes an angle sensor, an angular velocity calculation unit, and the like in addition to the motor 20.

In the present disclosure, the target steering torque generation unit 200 generates a target steering torque Tref, which is a target value of steering torque when assisting and controlling the steering system of the vehicle. The conversion unit 500 converts the target steering torque Tref into the target twist angle Δθref. The torsion angle control unit 300 generates a motor current command value Iref, which is a control target value of the current supplied to the motor 20.

The twist angle control unit 300 calculates the motor current command value Iref so that the twist angle Δθ becomes the target twist angle Δθref. The motor 20 is driven by the motor current command value Iref.

The steering direction determination unit 400 determines whether the steering direction is right-turning or left-turning based on the motor angular velocity ωm output from the EPS steering system / vehicle system 100, and outputs the determination results as steering state signals STs. FIG. 6 is an explanatory view of the steering direction.

The steering state indicating whether the steering direction is right-turning or left-turning can be obtained from the relationship between the steering angle θh and the motor angular velocity ωm as shown in FIG. 6, for example. That is, when the motor angular velocity ωm is a positive value, it is determined as “right turn”, and when it is a negative value, it is determined as “left turn”. Instead of the motor angular speed .omega.m, the steering angle [theta] h, may be used an angular velocity that is calculated by performing the speed calculation with respect to the handle angle theta ₁ or column angle theta _2.

The conversion unit 500 converts the target steering torque Tref generated by the target steering torque generation unit 200 into the target torsion angle Δθref using the relationship of the above equation (2).

Next, a basic operation example in the control unit of the first embodiment will be described. FIG. 7 is a flowchart showing an operation example of the control unit according to the first embodiment.

The steering direction determination unit 400 determines whether the steering direction is right-turning or left-turning based on the sign of the motor angular velocity ωm output from the EPS steering system / vehicle system 100, and uses the determination result as the steering state signal STs for target steering. Output to the torque generator 200 (step S10).

The target steering torque generation unit 200 generates a target steering torque Tref based on the vehicle speed Vs, the vehicle speed determination signal Vfile, the steering state signal STs, the steering angle θh, and the actual yaw rate γre (step S20).

The conversion unit 500 converts the target steering torque Tref generated by the target steering torque generation unit 200 into the target torsion angle Δθref (step S20). The target twist angle Δθref is output to the twist angle control unit 300.

The twist angle control unit 300 calculates the motor current command value Iref based on the target twist angle Δθref, steering angle θh, twist angle Δθ, and motor angular velocity ωm (step S30).

Then, current control is performed based on the motor current command value Iref output from the torsion angle control unit 300, and the motor 20 is driven (step S40).

FIG. 8 is a block diagram showing a configuration example of the target steering torque generating unit of the first embodiment. As shown in FIG. 8, the target steering torque generation unit 200 includes a basic map unit 210, a multiplication unit 211, a code extraction unit 213, a differentiation unit 220, a damper gain map unit 230, a hysteresis correction unit 240, and a SAT information correction unit 250. It includes a multiplication unit 260, 264, an addition unit 261, 262, 265, and a steering reaction force correction unit 280. FIG. 9 is a diagram showing a characteristic example of the basic map held by the basic map unit. FIG. 10 is a diagram showing a characteristic example of the damper gain map held by the damper gain map unit.

The steering angle θh and the vehicle speed Vs are input to the basic map unit 210. The basic map unit 210 outputs a torque signal Tref_a0 with the vehicle speed Vs as a parameter, using the basic map shown in FIG. That is, the basic map unit 210 outputs the torque signal Tref_a0 according to the vehicle speed Vs.

As shown in FIG. 9, the torque signal Tref_a0 has a characteristic of increasing as the magnitude (absolute value) | θh | of the steering angle θh increases. Further, the torque signal Tref_a has a characteristic of increasing as the vehicle speed Vs increases. In FIG. 9, a map is configured according to the magnitude | θh | of the steering angle θh, but a map corresponding to the positive and negative steering angles θh may be configured. In this case, the value of the torque signal Tref_a0 takes a positive or negative value, and the code calculation described later is unnecessary.

The code extraction unit 213 extracts the code of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. As a result, the code extraction unit 213 outputs "1" when the sign of the steering angle θh is "+" and outputs "-1" when the sign of the steering angle θh is "-".

The steering angle θh is input to the differential unit 220. The differentiation unit 220 differentiates the steering angle θh to calculate the steering angular velocity ωh, which is the angular velocity information. The differential unit 220 outputs the calculated steering angular velocity ωh to the multiplication unit 260.

The vehicle speed Vs is input to the damper gain map unit 230. Damper gain map 230, using the damper gain map of vehicle speed sensitive type shown in FIG. 10, and outputs the damper gain D _G corresponding to the vehicle speed Vs.

As shown in FIG. 10, damper gain D _G has gradually increases as the vehicle speed Vs is high. Damper gain D _G may be a mode for varying according to the steering angle [theta] h.

Multiplying unit 260, with respect to the steering angular velocity ωh outputted from the differentiating unit 220, multiplies the damper gain _{D G} outputted from the damper gain map 230, and outputs the result to adding section 262 as a torque signal Tref_b.

The steering direction determination unit 400 makes a determination as shown in FIG. 6, for example. The steering angle θh, the vehicle speed Vs, and the steering state signal STs, which are the determination results shown in FIG. 6, are input to the hysteresis correction unit 240. The hysteresis correction unit 240 calculates the torque signal Tref_c using the following equations (3) and (4) based on the steering angle θh and the steering state signal STs. In the following equations (3) and (4), x is the steering angle θh, y _R = Tref_c and y _L = Tref_c are the torque signals Tref_c. Further, the coefficient a is a value larger than 1, and the coefficient c is a value larger than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic, and the coefficient c is a coefficient representing the roundness of the hysteresis characteristic.

y _R = Ahys {1-a- ^{c (x-b)} } ... (3)

y _L = -Ahys {1-a ^{c (x-b')} } ... (4)

When steering to the right, the torque signal Tref_c (y _R ) is calculated using the above equation (3). When steering to the left, the torque signal Tref_c (y _L ) is calculated using the above equation (4). When switching from right-turn steering to left-turn steering, or when switching from left-turn steering to right-turn steering, the final coordinates (x ₁ , y ₁ ) of the steering angle θh and the previous values of the torque signal Tref_c. Based on the value of, the coefficient b or b'shown in the following equation (5) or (6) is substituted for the above equations (3) and (4) after the steering switching. As a result, continuity before and after steering switching is maintained.

b = x ₁ + (1 / c) log _a {1- (y ₁ / Ahys)} ... (5)

b'= x ₁ − (1 / c) log _a {1- (y ₁ / Ahys)} ... (6)

The above equations (5) and (6) can be derived by substituting x ₁ for x and y ₁ for y _R and y _L in the above equations (3) and (4). ..

When, for example, the Napier number e is used as the coefficient a, the above equations (3), (4), (5), and (6) are the following equations (7), (8), and (9), respectively. ) And (10) can be expressed.

y _R = Ahys [1-exp {-c (x-b)}] ... (7)

y _L = -Ahys [{1-exp {c (x-b')}] ... (8)

b = x ₁ + (1 / c) log _e {1- (y ₁ / Ahys)} ... (9)

b'= x ₁ − (1 / c) log _e {1- (y ₁ / Ahys)} ... (10)

FIG. 11 is a diagram showing a characteristic example of the hysteresis correction unit. In the example shown in FIG. 11, in the above equations (9) and (10), Ahys = 1 [Nm] and c = 0.3 are set, starting from 0 [deg], and +50 [deg], -50. An example of the characteristics of the torque signal Tref_c with hysteresis correction when the steering of [deg] is performed is shown. As shown in FIG. 11, the torque signal Tref_c output from the hysteresis correction unit 240 has a hysteresis characteristic such as the origin of 0 → L1 (thin line) → L2 (broken line) → L3 (thick line).

It should be noted that Ahys, which is a coefficient representing the output width of the hysteresis characteristic, and c, which is a coefficient representing roundness, may be made variable according to one or both of the vehicle speed Vs and the steering angle θh.

Further, the steering angular velocity ωh is obtained by a differential calculation with respect to the steering angle θh, but a low-pass filter (LPF) processing is appropriately performed in order to reduce the influence of high-frequency noise. Further, the differential calculation and the LPF processing may be performed by the high-pass filter (HPF) and the gain. Further, the steering angular velocity ωh may be calculated by performing differential calculation and LPF processing on the steering wheel angle θ1 detected by the upper angle sensor or the column angle θ2 detected by the lower angle sensor instead of the steering angle θh. .. The motor angular velocity ωm may be used as the angular velocity information instead of the steering angular velocity ωh, and in this case, the differential unit 220 becomes unnecessary.

Returning to FIG. 8, the multiplication unit 211 multiplies the torque signal Tref_a0 output from the basic map unit 210 by the sign of the steering angle θh output from the code extraction unit 213, and outputs the torque signal Tref_a to the addition unit 261. Output. As a result, the torque signal Tref_a corresponding to the positive and negative steering angles θh can be obtained.

The torque signal Tref_a, the torque signal Tref_b, and the torque signal Tref_c obtained as described above are added by the addition units 261,262 to obtain the torque signal Tref_e.

The torque signal Tref_a in the present embodiment corresponds to the "first torque signal" of the present disclosure. Further, the torque signal Tref_e in the present embodiment corresponds to the "second torque signal" of the present disclosure.

FIG. 12 is a block diagram showing a configuration example of the steering reaction force correction unit. As shown in FIG. 12, the steering reaction force correction unit 280 includes a correction gain generation unit 281, a correction torque map 282, a code extraction unit 283, and a multiplication unit 284.

The steering angle θh and the low-speed operation mode signal Pf output from the low-speed operation mode detection unit 15 (see FIG. 1) are input to the steering reaction force correction unit 280.

Here, the "low speed operation mode (second mode)" will be described. In the present embodiment, the "low-speed driving mode (second mode)" means, for example, when the vehicle is parked in a parking lot, when the vehicle is moved to a predetermined stop position, or when the vehicle retreats to return from the entered dead end. This is an operation mode selected when the driver performs a predetermined low-speed operation mode transition operation such as moving the vehicle. That is, the low-speed driving mode (second mode) in the present embodiment is a driving mode for moving the vehicle at a low speed when the predetermined low-speed driving mode transition operation as described above is performed.

The low-speed operation mode detection unit 15 is a configuration unit that detects that a predetermined low-speed operation mode transition operation has been performed by the driver and outputs a low-speed operation mode signal Pf. The low-speed driving mode detection unit 15 may be in a mode of detecting that the "parking button" provided on the center console of the vehicle or the like is pressed by the driver and outputting the low-speed driving mode signal Pf. .. Further, in the low-speed driving mode detection unit 15, for example, the driver operates the shift knob of the vehicle to select a position of "reverse (reverse)", "parking F (forward)", or "parking B (reverse)". The mode may be such that the low speed operation mode signal Pf is output by detecting that the signal has been generated. Here, "parking F (forward)" indicates a position to be selected when moving forward in the low-speed operation mode (second mode), and "parking B (backward)" indicates backward in the low-speed operation mode (second mode). Indicates the position to be selected when doing so. The means for selecting the low-speed operation mode (second mode) by the driver may be an embodiment other than the above, and the present invention is not limited by the means for selecting the low-speed operation mode (second mode) by the driver. Absent. In the following description, the normal operation mode when the low speed operation mode (second mode) is not selected is also referred to as a "drive mode (first mode)". That is, in the present disclosure, the low-speed operation mode detection unit 15 detects a predetermined low-speed operation mode transition operation and determines that the low-speed operation mode (second mode) is different from the drive mode (first mode). Corresponds to.

The correction gain generation unit 281 outputs a correction gain G (G is a positive value less than 1) corresponding to the low-speed operation mode signal Pf in the low-speed operation mode (second mode). Specifically, the correction gain generation unit 281 outputs, for example, a correction gain G = 0.3 in the low-speed operation mode (second mode). Further, the correction gain generation unit 281 outputs a correction gain G = 1 in the drive mode (first mode). The value of the correction gain G in the low-speed operation mode (second mode) is an example, and is not limited to 0.3. The value of the correction gain G in the low-speed operation mode (second mode) can be a positive predetermined value less than 1.

In the correction torque map 282, a correction torque is set according to the magnitude | θh | of the steering angle θh. The correction torque map 282 outputs a correction torque signal Tref_p0 according to the magnitude | θh | of the steering angle θh.

The code extraction unit 283 extracts the code of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. As a result, the code extraction unit 283 outputs "1" when the sign of the steering angle θh is "+", and outputs "-1" when the sign of the steering angle θh is "-".

The multiplication unit 284 multiplies the correction torque signal Tref_p0 output from the correction torque map 282 by the sign of the steering angle θh output from the code extraction unit 283, and outputs the correction torque signal Tref_p. As a result, the correction torque signal Tref_p corresponding to the positive and negative steering angles θh can be obtained.

FIG. 13 is a diagram showing an example of a correction torque map. In FIG. 13, the horizontal axis represents the absolute value | θh | of the steering angle θh, and the vertical axis represents the torque.

In FIG. 13, an example of the torque signal Tref_a0 is shown by a broken line, and the correction torque signal Tref_p0 is shown by a solid line. In FIG. 13, a map is configured according to the magnitude (absolute value) | θh | of the steering angle θh, but a map corresponding to the positive and negative steering angles θh may be configured. In this case, the value of the correction torque signal Tref_p0 can take a positive or negative value. The correction torque map 282 may be stored in the EEPROM 1004 of the control computer 1100 constituting the control unit 30, or may be held by the steering reaction force correction unit 280.

As shown in FIG. 13, the correction torque signal Tref_p0 gradually decreases in the rate of change as the absolute value | θh | of the steering angle θh increases in the region where the absolute value | θh | of the steering angle θh is less than the threshold value θh_th. Has the property of increasing along the curve. Further, as shown in FIG. 13, the correction torque signal Tref_p0 has a constant value | Tc | in a region where the absolute value | θh | of the steering angle θh is equal to or higher than the threshold value | θh_th |. In the present embodiment, the inclination K2 at the absolute value | θh | = 0 of the steering angle θh of the correction torque signal Tref_p0 is set to be larger than the inclination K1 at the absolute value | θh | = 0 of the steering angle θh of the torque signal Tref_a0. .. The threshold value | θh_th | and the constant value | Tc | can be any predetermined value.

The steering reaction force correction unit 280 outputs a correction torque signal Tref_p corresponding to the low-speed operation mode signal Pf. The steering reaction force correction unit 280 outputs a correction torque signal Tref_p according to the steering angle θh in the low-speed operation mode (second mode). Further, the steering reaction force correction unit 280 outputs a correction torque signal Tref_p = 0 in the drive mode (first mode) regardless of the steering angle θh.

Returning to FIG. 8, the multiplication unit 264 multiplies the torque signal Tref_e output from the addition unit 261 by the correction gain G output from the steering reaction force correction unit 280, and outputs the torque signal Tref_f to the addition unit 265. .. The addition unit 265 adds the correction torque signal Tref_p output from the steering reaction force correction unit 280 to the torque signal Tref_f output from the multiplication unit 264, and outputs it as the target steering torque Tref. That is, the target steering torque Tref can be expressed by the following equation (11).

Tref = (Tref_e) x G + Tref_p
= Tref_f + Tref_p ... (11)

The torque signal Tref_f in the present embodiment corresponds to the "third torque signal" of the present disclosure. Further, the correction torque signal Tref_p in the present embodiment corresponds to the "fourth torque signal" of the present disclosure.

FIG. 14 is a diagram showing an example of the target steering torque output from the target steering torque generation unit. In FIG. 14, the horizontal axis represents the steering angle θh, and the vertical axis represents the torque.

In FIG. 14, an example of the target steering torque in the drive mode is shown by a broken line, and the target steering torque in the low speed operation mode is shown by a solid line.

In the drive mode (first mode), as described above, the torque signal Tref_e (second torque signal) is multiplied by the correction gain G = 1 and the correction torque signal Tref_p (fourth torque signal) = 0 is added. .. As a result, the target steering torque Tref = torque signal Tref_e (second torque signal), and the target steering torque Tref suitable for the drive mode (first mode) can be obtained.

In the low-speed operation mode (second mode), as described above, the torque signal Tref_e (second torque signal) is multiplied by a positive correction gain G (for example, G = 0.3) of less than 1, and the torque signal Tref_f (Third torque signal) is generated, and the inclination of the steering angle θh at the absolute value | θh | = 0 is larger than that of the torque signal Tref_a (first torque signal) with respect to the torque signal Tref_f (third torque signal). The correction torque signal Tref_p (fourth torque signal) is added to generate the target steering torque Tref. As a result, as shown in FIG. 14, in the low-speed operation mode (second mode), the target steering torque Tref can be made smaller than in the drive mode (first mode), and the operation of the steering wheel 1 can be made lighter. .. Further, as shown in FIG. 14, in a predetermined region where the steering angle θh is around 0 (the region indicated by the alternate long and short dash line in FIG. 14), the change in steering force can be increased with respect to the change in steering angle θh. .. In other words, in a predetermined region where the absolute value | θh | of the steering angle θh of the steering wheel 1 is zero or more, the rate of change of the target steering torque Tref in the low speed operation mode (second mode) is equal to or more than the drive mode (first mode). In a region other than the predetermined region, the rate of change of the target steering torque Tref in the low-speed operation mode (second mode) is smaller than that in the drive mode (first mode). This makes it easier for the driver to recognize the steering angle of zero. Therefore, the burden on the driver can be reduced and the steering feeling can be improved.

In the example shown in FIG. 8, the torque signal Tref_e (second torque signal) obtained by adding the torque signal Tref_a (first torque signal), the torque signal Tref_b, and the torque signal Tref_c is multiplied by the correction gain G. An example of generating a torque signal Tref_f (third torque signal) has been shown, but each of the torque signal Tref_a (first torque signal), the torque signal Tref_b, and the torque signal Tref_c is individually corrected to be less than 1. A mode may be used in which a torque signal Tref_f (third torque signal) is generated by multiplying the gain G and then adding the torque signal.

Hereinafter, the twist angle control unit 300 (see FIG. 5) of the first embodiment will be described with reference to FIG.

FIG. 15 is a block diagram showing a configuration example of the twist angle control unit of the first embodiment. The twist angle control unit 300 calculates the motor current command value Iref based on the target twist angle Δθref, twist angle Δθ, steering angle θh, and motor angular velocity ωm. The torsion angle control unit 300 includes a torsion angle feedback (FB) compensation unit 310, a speed control unit 330, a stabilization compensation unit 340, an output limiting unit 350, a steering angle disturbance compensation unit 360, a subtraction unit 361, an addition unit 363, and a deceleration unit. The ratio part 370 is provided.

The target twist angle Δθref output from the conversion unit 500 is additionally input to the subtraction unit 361. The twist angle Δθ is subtracted and input to the subtracting unit 361. The steering angle θh is input to the steering angle disturbance compensation unit 360. The motor angular velocity ωm is input to the stabilization compensation unit 340.

The twist angle FB compensation unit 310 multiplies the compensation value CFB (transfer function) by the deviation Δθ0 of the target twist angle Δθref and the twist angle Δθ calculated by the subtraction unit 361, and the twist angle Δθ follows the target twist angle Δθref. The target column angular velocity ωref1 is output. The target column angular velocity ωref1 is additionally output to the addition unit 363. The compensation value CFB may be a simple gain Kpp or a commonly used compensation value such as a PI control compensation value.

The steering angle disturbance compensation unit 360 multiplies the steering angle θh by the compensation value Ch (transfer function) and outputs the target column angular velocity ωref2. The target column angular velocity ωref2 is additionally output to the addition unit 363.

The addition unit 363 adds the target column angular velocity ωref1 and the target column angular velocity ωref2, and outputs the target column angular velocity ωref to the speed control unit 330. As a result, it is possible to suppress the influence of the change in the steering angle θh input from the driver on the torsion bar torsion angle Δθ, and improve the followability of the torsion angle Δθ to the target torsion angle Δθref for sudden steering.

When the steering angle θh changes due to the steering of the driver, the change in the steering angle θh affects the torsion angle Δθ as a disturbance, and a deviation occurs with respect to the target torsion angle Δθref. In particular, for sudden steering, the deviation from the target twist angle Δθref due to the change in the steering angle θh becomes remarkable. The basic purpose of the steering angle disturbance compensating unit 360 is to reduce the influence of the steering angle θh as the disturbance.

The speed control unit 330 calculates the motor current command value Is so that the column angular velocity ωc follows the target column angular velocity ωref by IP control (proportional leading PI control). As shown in FIG. 15, the column angular velocity ωc may be a value obtained by multiplying the motor angular velocity ωm by the reduction ratio 1 / N of the reduction ratio unit 370, which is a reduction mechanism.

The subtraction unit 333 calculates the difference (ωref−ωc) between the target column angular velocity ωref and the column angular velocity ωc. The integration unit 331 integrates the difference (ωref−ωc) between the target column angular velocity ωref and the column angular velocity ωc, and adds and inputs the integration result to the subtraction unit 334.

The torsion angular velocity ωt is also output to the proportional portion 332. The proportional unit 332 performs proportional processing with a gain Kvp on the column angular velocity ωc, and subtracts and inputs the proportional processing result to the subtraction unit 334. The subtraction result in the subtraction unit 334 is output as the motor current command value Is. The speed control unit 330 is not an IP control, but a PI control, a P (proportional) control, a PID (proportional integral differential) control, a PI-D control (differential leading PID control), a model matching control, and a model reference. The motor current command value Is may be calculated by a commonly used control method such as control.

The output limiting unit 350 has preset upper and lower limit values for the motor current command value Is. The upper and lower limits of the motor current command value Is are limited, and the motor current command value Iref is output.

The configuration of the torsion angle control unit 300 in this embodiment is an example, and may be different from the configuration shown in FIG. For example, the torsion angle control unit 300 may not include the steering angle disturbance compensation unit 360, the addition unit 363, and the reduction ratio unit 370.

(Embodiment 2)
FIG. 16 is a diagram showing an example of an internal block configuration of the control unit according to the second embodiment. The same components as those described in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted. The control unit (ECU) 30a according to the second embodiment is different from the first embodiment in the configurations of the target steering torque generation unit 201 and the torsion angle control unit 300a.

In addition to the steering angle θh, the vehicle speed Vs, and the vehicle speed determination signal Vfile, the steering torque Ts and the motor angle θm are input to the target steering torque generation unit 201.

The twist angle control unit 300a calculates the motor current command value Imc so that the twist angle Δθ becomes the target twist angle Δθref. The motor 20 is driven by the motor current command value Imcc.

FIG. 17 is a block diagram showing a configuration example of the target steering torque generation unit of the second embodiment. As shown in FIG. 17, the target steering torque generation unit 201 of the second embodiment includes a SAT information correction unit 250 and an addition unit 263 in addition to the configuration described in the first embodiment.

The steering angle θh, vehicle speed Vs, steering torque Ts, motor angle θm, and motor current command value Imc are input to the SAT information correction unit 250. The SAT information correction unit 250 calculates the self-aligning torque (SAT) based on the steering torque Ts, the motor angle θm, and the motor current command value Imc, and further performs filter processing, gain multiplication, and limiting processing to perform torque signal Tref_d. Is calculated.

FIG. 18 is a block diagram showing a configuration example of the SAT information correction unit. The SAT information correction unit 250 includes a SAT calculation unit 251, a filter unit 252, a steering torque sensitive gain unit 253, a vehicle speed sensitive gain unit 254, a steering angle sensitive gain unit 255, and a limiting unit 256.

Here, the state of the torque generated between the road surface and the steering wheel will be described with reference to FIG. FIG. 19 is an image diagram showing a state of torque generated between the road surface and the steering wheel.

When the driver steers the steering wheel, steering torque Ts is generated, and the motor 20 generates assist torque (motor torque) Tm according to the steering torque Ts. As a result, the wheels are steered and a self-aligning torque T _SAT is generated as a reaction force. At that time, torque that becomes resistance to steering the handle is generated by the column shaft conversion inertia (inertia acting on the column shaft by the motor 20 (rotor), the reduction mechanism, etc.) J and friction (static friction) Fr. Further, the rotational speed of the motor 20, the physical torque expressed as a damper section (damper coefficient D _M) (viscous torque) is generated. From the balance of these forces, the equation of motion shown in Eq. (12) below can be obtained.

J x α _M + Fr x sign (ω _M ) + D _M x ω _M = Tm + Ts + T _SAT ... (12)

In the above equation (12), ω _M is the motor angular velocity converted to the column shaft (converted to the value with respect to the column shaft), and α _M is the motor angular acceleration converted to the column shaft. Then, when the above equation (12) is solved for T _SAT , the following equation (13) is obtained.

T _SAT = -Tm-Ts + J x α _M + Fr x sign (ω _M ) + D _M x ω _M ... (13)

As can be seen from the above equation (13), the motor angular velocity ω _M , the motor angular acceleration α _M , the assist torque Tm and the steering torque Ts are obtained in advance by obtaining the column shaft conversion inertia J, the static friction Fr and the damper coefficient DM as constants. The self-aligning torque T _SAT can be calculated more. The column shaft conversion inertia J may be a value converted to the column shaft simply by using the relational expression of the motor inertia and the reduction ratio.

The steering torque Ts, the motor angle θm, and the motor current command value Imc are input to the SAT calculation unit 251. The SAT calculation unit 251 calculates the self-aligning torque T _SAT using the above equation (13). The SAT calculation unit 251 includes a conversion unit 251A, an angular velocity calculation unit 251B, an angular acceleration calculation unit 251C, a block 251D, a block 251E, a block 251F, a block 251G, and adders 251H, 251I, and 251J.

The motor current command value Imc is input to the conversion unit 251A. The conversion unit 251A calculates the column shaft-converted assist torque Tm by multiplying the predetermined gear ratio and torque constant.

The motor angle θm is input to the angular velocity calculation unit 251B. The angular velocity calculation unit 251B calculates the motor angular velocity ω _M converted to the column axis by the differential processing and the multiplication of the gear ratios.

The motor angular velocity ω _M is input to the angular acceleration calculation unit 251C. Angular acceleration calculating unit 251C differentiates the motor angular speed omega _M, calculates the motor angular acceleration alpha _M which is converted column shaft.

Then, using the input steering torque Ts, the calculated assist torque Tm, the motor angular velocity ω _M, and the motor angular acceleration α _M , the blocks 251D, block 251E, block 251F, block 251G, and adders 251H, 251I, According to 251J, the self-aligning torque T _SAT is calculated based on Equation 8 with the configuration shown in FIG.

The motor angular velocity ω _M output from the angular velocity calculation unit 251B is input to the block 251D. Block 251D functions as a sign function and outputs the code of the input data.

The motor angular velocity ω _M output from the angular velocity calculation unit 251B is input to the block 251E. Block 251E is input data is multiplied by the damper coefficient _{D M} outputs.

The block 251F outputs the input data from the block 251D by multiplying the static friction Fr.

The motor angular acceleration α _M output from the angular acceleration calculation unit 251C is input to the block 251G. The block 251G outputs the input data by multiplying it by the column axis conversion inertia J.

The adder 251H adds the steering torque Ts and the assist torque Tm output from the conversion unit 251A.

The adder 251I subtracts the output of block 251G from the output of adder 251H.

The adder 251J adds the output of block 251E and the output of block 251F and subtracts the output of adder 251I.

With the above configuration, the above equation (13) can be realized. That is, the self-aligning torque T _SAT is calculated according to the configuration of the SAT calculation unit 251 shown in FIG.

If the column angle can be directly detected, the column angle may be used as the angle information instead of the motor angle θm. In this case, column axis conversion is unnecessary. Further, instead of the motor angle θm, a signal obtained by converting the motor angular velocity ωm from the EPS steering system / vehicle system 100 into a column axis may be input as the motor angular velocity ω _M , and the differential processing with respect to the motor angle θm may be omitted. Further, the self-aligning torque T _SAT may be calculated by a method other than the above, and a measured value may be used instead of the calculated value.

In order to utilize the self-aligning torque T _SAT calculated by the SAT calculation unit 251 and appropriately convey the steering feeling to the driver, the filter unit 252 extracts the information to be transmitted from the self-aligning torque T _SAT and steers it. The amount transmitted by the torque-sensitive gain unit 253, the vehicle speed-sensitive gain unit 254, and the steering angle-sensitive gain unit 255 is adjusted, and the upper and lower limit values are further adjusted by the limiting unit 256. In the present disclosure, the self-aligning torque T _SAT calculated by the SAT calculation unit 251 is also output to the target steering torque generation unit 201.

The self-aligning torque T _SAT is input to the filter unit 252 from the SAT calculation unit 251. The filter unit 252 performs a filter process on the self-aligning torque T _SAT by, for example, a band bus filter, and outputs SAT information T _ST 1.

The SAT information T _ST 1 and the steering torque Ts output from the filter unit 252 are input to the steering torque sensitive gain unit 253. The steering torque sensitive gain unit 253 sets the steering torque sensitive gain.

FIG. 20 is a diagram showing a characteristic example of the steering torque sensitive gain. As shown in FIG. 20, the steering torque sensitive gain unit 253 sets the steering torque sensitive gain so that the sensitivity becomes high in the vicinity of the on-center in the straight running state. The steering torque sensitive gain unit 253 multiplies the steering torque sensitive gain set according to the steering torque Ts by the SAT information T _ST 1 and outputs the SAT information T _ST 2.

In FIG. 20, the steering torque sensitive gain is fixed at 1.0 when the steering torque Ts is Ts1 (for example, 2 Nm) or less, and is less than 1.0 when the steering torque Ts is Ts2 (> Ts1) (for example, 4 Nm) or more. An example is shown in which the steering torque Ts is fixed and is set to decrease at a constant rate between Ts1 and Ts2.

The SAT information T _ST 2 and the vehicle speed Vs output from the steering torque sensitive gain unit 253 are input to the vehicle speed sensitive gain unit 254. The vehicle speed-sensitive gain unit 254 sets the vehicle speed-sensitive gain.

FIG. 21 is a diagram showing a characteristic example of the vehicle speed sensitive gain. As shown in FIG. 21, the vehicle speed-sensitive gain unit 254 sets the vehicle speed-sensitive gain so as to increase the sensitivity during high-speed driving. The vehicle speed-sensitive gain unit 254 multiplies the vehicle speed-sensitive gain set according to the vehicle speed Vs by the SAT information T _ST 2 and outputs the SAT information T _ST 3.

In FIG. 21, the vehicle speed sensitive gain is fixed at 1.0 when the vehicle speed Vs is Vs2 (for example, 70 km / h) or more, and is smaller than 1.0 when the vehicle speed Vs is Vs1 (<Vs2) (for example, 50 km / h) or less. An example is shown in which the vehicle speed Vs is set to increase at a constant rate between Vs1 and Vs2.

The SAT information T _ST 3 and the steering angle θh output from the vehicle speed-sensitive gain unit 254 are input to the steering angle-sensitive gain unit 255. The steering angle sensitive gain unit 255 sets the steering angle sensitive gain.

FIG. 22 is a diagram showing a characteristic example of the steering angle sensitive gain. As shown in FIG. 22, the steering angle sensitive gain unit 255 starts to act from a predetermined steering angle and sets the steering angle sensitive gain so that the sensitivity becomes high when the steering angle is large. The steering angle sensitive gain unit 255 multiplies the steering angle sensitive gain set according to the steering angle θh by the SAT information T _ST 3 and outputs the torque signal Tref_d0.

In FIG. 22, the steering angle sensitive gain is fixed at a predetermined gain value Gα when the steering angle θh is θh1 (for example, 10 deg) or less, and is fixed at 1.0 when the steering angle θh is θh2 (for example, 30 deg) or more, and the steering angle θh is An example is shown in which the increment is set to increase at a constant rate between θh1 and θh2. If it is desired to increase the sensitivity when the steering angle θh is large, Gα may be set in the range of 0 ≦ Gα <1. If it is desired to increase the sensitivity when the steering angle θh is small, Gα may be set in the range of 1 <Gα, although not shown. If it is not desired to change the sensitivity depending on the steering angle θh, Gα = 1 may be set.

The torque signal Tref_d0 output from the steering angle sensitive gain unit 255 is input to the limiting unit 256. The limiting unit 256 is set with an upper limit value and a lower limit value of the torque signal Tref_d0.

FIG. 23 is a diagram showing an example of setting the upper limit value and the lower limit value of the torque signal in the limiting portion. As shown in FIG. 23, the limiting unit 256 has preset upper and lower limit values for the torque signal Tref_d0, and when the input torque signal Tref_d0 is equal to or greater than the upper limit value, the upper limit value is set, and when it is equal to or less than the lower limit value. The lower limit value is output, and in other cases, the torque signal Tref_d0 is output as the torque signal Tref_d.

The steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be curved characteristics instead of linear characteristics as shown in FIGS. 20, 21, and 22. Further, the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be appropriately adjusted according to the steering feeling. Further, the limiting portion 256 may be deleted when there is no possibility that the magnitude of the torque signal will increase or when it is suppressed by other means. The steering torque-sensitive gain unit 253, the vehicle speed-sensitive gain unit 254, and the steering angle-sensitive gain unit 255 can also be omitted as appropriate. Further, the installation positions of the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be interchanged. Further, for example, the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be obtained in parallel and multiplied by the SAT information T _ST 1 by one component.

That is, the configuration of the SAT information correction unit 250 in this embodiment is an example, and may be different from the configuration shown in FIG.

Also in the present embodiment, the same effect as that of the first embodiment can be obtained by providing the target steering torque generation unit 201 with the steering reaction force correction unit 280 described in the above-described first embodiment.

Specifically, the torque signal Tref_a (first torque signal), the torque signal Tref_b, the torque signal Tref_c, and the torque signal Tref_d are added by the addition units 261,262,263 to obtain the torque signal Tref_e (second torque signal). To be done.

Further, the multiplication unit 264 multiplies the torque signal Tref_e (second torque signal) output from the addition unit 261 by the correction gain G output from the steering reaction force correction unit 280, and the torque signal Tref_f (third torque). It is output to the addition unit 265 as a signal). The addition unit 265 adds the correction torque signal Tref_p (fourth torque signal) output from the steering reaction force correction unit 280 to the torque signal Tref_f (third torque signal) output from the multiplication unit 264 to target. It is output as steering torque Tref.

In the drive mode (first mode), as in the first embodiment, the torque signal Tref_e (second torque signal) is multiplied by the correction gain G = 1 to obtain the correction torque signal Tref_p (fourth torque signal) = 0. to add. As a result, the target steering torque Tref = torque signal Tref_e (second torque signal), and the target steering torque Tref suitable for the drive mode (first mode) can be obtained.

In the low-speed operation mode (second mode), the torque is obtained by multiplying the torque signal Tref_e (second torque signal) by a positive correction gain G (for example, G = 0.3) of less than 1 as in the first embodiment. A signal Tref_f (third torque signal) is generated, and a tilt at an absolute value | θh | = 0 of the steering angle θh with respect to the torque signal Tref_f (third torque signal) with respect to the torque signal Tref_a (first torque signal). The correction torque signal Tref_p (fourth torque signal) having a large value is added to generate the target steering torque Tref. As a result, as in the first embodiment, the target steering torque Tref can be made smaller than that in the drive mode (first mode), and the operation of the steering wheel 1 can be made lighter. Further, as in the first embodiment, in the region where the steering angle θh is around 0 (the region indicated by the alternate long and short dash line in FIG. 14), the change in steering force can be increased with respect to the change in steering angle θh. It becomes easier to recognize zero rudder angle. As a result, the burden on the driver can be reduced and the steering feeling can be improved.

Hereinafter, the twist angle control unit 300a of the second embodiment will be described with reference to FIG. 24.

FIG. 24 is a block diagram showing a configuration example of the twist angle control unit of the second embodiment. The twist angle control unit 300a calculates the motor current command value Imc based on the target twist angle Δθref, the twist angle Δθ, and the motor angular velocity ωm. The torsion angle control unit 300a includes a torsion angle feedback (FB) compensation unit 310, a torsion angular velocity calculation unit 320, a speed control unit 330, a stabilization compensation unit 340, an output limiting unit 350, a subtraction unit 361, and an addition unit 362. ..

The target twist angle Δθref output from the conversion unit 500 is additionally input to the subtraction unit 361. The torsion angle Δθ is subtracted and input to the subtraction unit 361 and is input to the torsion angular velocity calculation unit 320. The motor angular velocity ωm is input to the stabilization compensation unit 340.

The twist angle FB compensation unit 310 multiplies the compensation value CFB (transfer function) by the deviation Δθ0 of the target twist angle Δθref and the twist angle Δθ calculated by the subtraction unit 361, and the twist angle Δθ follows the target twist angle Δθref. The target torsional velocity ωref is output. The compensation value CFB may be a simple gain Kpp or a commonly used compensation value such as a PI control compensation value.

The target torsional velocity ωref is input to the speed control unit 330. The torsion angle FB compensation unit 310 and the speed control unit 330 make it possible to make the torsion angle Δθ follow the target torsion angle Δθref and realize a desired steering torque.

The torsion angular velocity calculation unit 320 performs a differential calculation process on the torsion angle Δθ to calculate the torsion angular velocity ωt. The torsion angular velocity ωt is output to the speed control unit 330. The torsional angular velocity calculation unit 320 may perform pseudo-differentiation by HPF and gain as a differential calculation. Further, the torsion angular velocity calculation unit 320 may calculate the torsion angular velocity ωt from another means or other than the torsion angle Δθ and output it to the speed control unit 330.

The speed control unit 330 calculates the motor current command value Imca1 so that the torsion angular velocity ωt follows the target torsional velocity ωref by IP control (proportional leading PI control).

The subtraction unit 333 calculates the difference (ωref−ωt) between the target torsional velocity ωref and the torsional angular velocity ωt. The integration unit 331 integrates the difference (ωref−ωt) between the target torsional velocity ωref and the torsional angular velocity ωt, and adds and inputs the integration result to the subtraction unit 334.

The torsion angular velocity ωt is also output to the proportional portion 332. The proportional unit 332 performs proportional processing with a gain Kvp on the torsion angular velocity ωt, and subtracts and inputs the proportional processing result to the subtraction unit 334. The subtraction result in the subtraction unit 334 is output as the motor current command value Imca1. The speed control unit 330 is not an IP control, but a PI control, a P (proportional) control, a PID (proportional integral differential) control, a PI-D control (differential leading PID control), a model matching control, and a model reference. The motor current command value Imca1 may be calculated by a commonly used control method such as control.

The stabilization compensation unit 340 has a compensation value Cs (transfer function), and calculates the motor current command value Imca2 from the motor angular velocity ωm. If the gains of the torsion angle FB compensating unit 310 and the speed control unit 330 are increased in order to improve the followability and the disturbance characteristics, a high-frequency controlled oscillation phenomenon occurs. As a countermeasure, the transfer function (Cs) required for stabilizing the motor angular velocity ωm is set in the stabilization compensation unit 340. As a result, it is possible to realize stabilization of the entire EPS control system.

The addition unit 362 adds the motor current command value Imca1 from the speed control unit 330 and the motor current command value Imca2 from the stabilization compensation unit 340, and outputs the motor current command value Imccb.

The output limiting unit 350 is preset with an upper limit value and a lower limit value with respect to the motor current command value Imccb. The output limiting unit 350 limits the upper and lower limits of the motor current command value Imccb and outputs the motor current command value Imcc.

The configuration of the twist angle control unit 300a in this embodiment is an example, and may be different from the configuration shown in FIG. 24. For example, the twist angle control unit 300a may not include the stabilization compensation unit 340.

(Embodiment 3)
In the first and second embodiments, the present disclosure is applied to the column type EPS as one of the steering devices for vehicles, but the present disclosure is not limited to the upstream type such as the column type, and the downstream type such as the rack and pinion. It is also applicable to EPS. Further, by performing feedback control based on the target torsion angle, it can be applied to a steering bar (SBW) reaction force device having at least a torsion bar (arbitrary spring constant) and a sensor for detecting the torsion angle. An embodiment (Embodiment 3) when the present disclosure is applied to an SBW reaction force device provided with a torsion bar will be described.

First, the entire SBW system including the SBW reaction force device will be described. FIG. 25 is a diagram showing a configuration example of the SBW system corresponding to the general configuration of the electric power steering device shown in FIG. The same components as those described in the above-described first and second embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

The SBW system does not have an intermediate shaft that is mechanically coupled to the column shaft 2 at the universal joint 4a in FIG. 1, and transmits the operation of the steering wheel 1 to a steering mechanism composed of steering wheels 8L, 8R, etc. by an electric signal. It is a system. As shown in FIG. 25, the SBW system includes a reaction force device 60 and a drive device 70, and a control unit (ECU) 50 controls both devices. The reaction force device 60 detects the steering angle θh by the steering angle sensor 14, and at the same time, transmits the motion state of the vehicle transmitted from the steering wheels 8L and 8R to the driver as reaction force torque. The reaction force torque is generated by the reaction force motor 61. In the present disclosure, the torque sensor 10 detects the steering torque Ts, but the present invention is not limited to this. Further, the angle sensor 74 detects the motor angle θm of the reaction force motor 61. The drive device 70 drives the drive motor 71 in accordance with the steering of the steering wheel 1 by the driver, applies the driving force to the pinion rack mechanism 5 via the gear 72, and operates the pinion rack mechanism 5 via the tie rods 6a and 6b. Steer the facing wheels 8L and 8R. An angle sensor 73 is arranged in the vicinity of the pinion rack mechanism 5 to detect the steering angle θt of the steering wheels 8L and 8R. In order to coordinately control the reaction force device 60 and the drive device 70, the ECU 50 adds information such as steering angle θh and steering angle θt output from both devices, and based on vehicle speed Vs from the vehicle speed sensor 12 and the like. The voltage control command value Vref1 that drives and controls the reaction force motor 61 and the voltage control command value Vref2 that drives and controls the drive motor 71 are generated.

The configuration of the third embodiment to which the present disclosure is applied to such an SBW system will be described.

FIG. 26 is a block diagram showing the configuration of the third embodiment. In the third embodiment, the twist angle Δθ is controlled (hereinafter referred to as “twist angle control”) and the steering angle θt is controlled (hereinafter referred to as “turning angle control”), and the reaction force device is twisted. It is controlled by control, and the drive unit is controlled by steering angle control. The drive device may be controlled by another control method.

In the torsion angle control, the torsion angle Δθ follows the target torsion angle Δθref calculated through the target steering torque generation unit 202 and the conversion unit 500 using the steering angle θh and the like by the same configuration and operation as in the second embodiment. Such control is performed. The motor angle θm is detected by the angle sensor 74, and the motor angular velocity ωm is calculated by differentiating the motor angle θm by the angular velocity calculation unit 951. The steering angle θt is detected by the angle sensor 73. Further, although the processing in the EPS steering system / vehicle system 100 is not described in detail in the first embodiment, the current control unit 130 includes the subtraction unit 32B, the PI control unit 35, and the PWM control unit shown in FIG. Based on the motor current command value Imc output from the torsion angle control unit 300a and the current value Imr of the reaction force motor 61 detected by the motor current detector 140 by the same configuration and operation as those of 36 and the inverter circuit 37, The reaction force motor 61 is driven to control the current.

In the steering angle control, the target steering angle generation unit 910 generates a target steering angle θtref based on the steering angle θh, and the target steering angle θtref is input to the steering angle control unit 920 together with the steering angle θt. The steering angle control unit 920 calculates the motor current command value Imct so that the steering angle θt becomes the target steering angle θtref. Then, based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940, the current control unit 930 has the same configuration and operation as the current control unit 130, and the drive motor has the same configuration and operation. The 71 is driven to control the current. In the present disclosure, the motor current command value Imct calculated by the steering angle control unit 920 is also output to the target steering torque generation unit 202.

FIG. 27 is a diagram showing a configuration example of the target steering angle generation unit. The target steering angle generation unit 910 includes a limiting unit 931, a rate limiting unit 932, and a correction unit 933.

The limiting unit 931 limits the upper and lower limits of the steering angle θh and outputs the steering angle θh1. Similar to the output limiting unit 350 in the twist angle control unit 300a shown in FIG. 24, the upper limit value and the lower limit value with respect to the steering angle θh are set in advance to limit.

The rate limiting unit 932 sets and limits the amount of change in the steering angle θh1 in order to avoid a sudden change in the steering angle, and outputs the steering angle θh2. For example, the difference from the steering angle θh1 one sample before is used as the change amount, and when the absolute value of the change amount is larger than a predetermined value (limit value), the steering angle is set so that the absolute value of the change amount becomes the limit value. θh1 is added or subtracted and output as the steering angle θh2, and if it is equal to or less than the limit value, the steering angle θh1 is output as it is as the steering angle θh2. Instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to limit the amount of change. You may want to limit the rate.

The correction unit 933 corrects the steering angle θh2 and outputs the target steering angle θtref. For example, the target steering angle θtref is obtained from the steering angle θh2 by using a map that defines the characteristics of the target steering angle θtref with respect to the magnitude | θh2 | of the steering angle θh2. Alternatively, the target steering angle θtref may be obtained by simply multiplying the steering angle θh2 by a predetermined gain.

FIG. 28 is a diagram showing a configuration example of the steering angle control unit. The steering angle control unit 920 has the same configuration as the configuration example of the torsion angle control unit 300a shown in FIG. 24 except for the stabilization compensation unit 340 and the addition unit 362, and has a target torsion angle Δθref and a torsion. The target steering angle θtref and steering angle θt are input instead of the angle Δθ, and the steering angle feedback (FB) compensation unit 921, the steering angular velocity calculation unit 922, the speed control unit 923, the output limiting unit 926 and the subtraction unit 927 are input. However, the same operation is performed with the same configurations as the torsion angle FB compensation unit 310, the torsion angular velocity calculation unit 320, the speed control unit 330, the output limiting unit 350, and the subtraction unit 361, respectively.

In such a configuration, an operation example of the third embodiment will be described with reference to the flowchart of FIG. FIG. 29 is a flowchart showing an operation example of the third embodiment.

When the operation is started, the angle sensor 73 detects the steering angle θt, the angle sensor 74 detects the motor angle θm (step S110), the steering angle θt is the steering angle control unit 920, and the motor angle θm is the angular velocity. Each is input to the calculation unit 951.

The angular velocity calculation unit 951 differentiates the motor angle θm to calculate the motor angular velocity ωm, and outputs the motor angular velocity ωm to the torsion angle control unit 300a (step S120).

After that, the target steering torque generation unit 202 executes the same operation as in steps S10 to S40 shown in FIG. 7, drives the reaction force motor 61, and executes current control (steps S130 to S160).

On the other hand, in the steering angle control, the target steering angle generation unit 910 inputs the steering angle θh, and the steering angle θh is input to the limiting unit 931. The limiting unit 931 limits the upper and lower limit values of the steering angle θh by preset upper and lower limit values (step S170), and outputs the steering angle θh1 to the rate limiting unit 932. The rate limiting unit 932 limits the amount of change in the steering angle θh1 by a preset limit value (step S180), and outputs the steering angle θh2 to the correction unit 933. The correction unit 933 corrects the steering angle θh2 to obtain the target steering angle θtref (step S190), and outputs the steering angle θh2 to the steering angle control unit 920.

The steering angle control unit 920, which has input the steering angle θt and the target steering angle θtref, calculates the deviation Δθt0 by subtracting the steering angle θt from the target steering angle θtref by the subtracting unit 927 (step S200). ). The deviation Δθt0 is input to the steering angle FB compensation unit 921, and the steering angle FB compensation unit 921 compensates for the deviation Δθt0 by multiplying the deviation Δθt0 by the compensation value (step S210), and sets the target steering angular velocity ωtref. Output to the control unit 923. The steering angular velocity calculation unit 922 inputs the steering angle θt, calculates the steering angular velocity ωtt by a differential calculation with respect to the steering angle θt (step S220), and outputs the steering angular velocity ωtt to the speed control unit 923. The speed control unit 923 calculates the motor current command value Imcta by IP control in the same manner as the speed control unit 330 (step S230), and outputs the motor current command value Imcta to the output limiting unit 926. The output limiting unit 926 limits the upper and lower limit values of the motor current command value Imcta by the preset upper limit value and lower limit value (step S240), and outputs the motor current command value Imct as the motor current command value Imct (step S250).

The motor current command value Imct is input to the current control unit 930, and the current control unit 930 is based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940. 71 is driven and current control is performed (step S260).

The order of data input and calculation in FIG. 29 can be changed as appropriate. Further, the speed control unit 923 in the steering angle control unit 920 is not the IP control but the PI control, the P control, the PID control, and the PI-D, like the speed control unit 330 in the twist angle control unit 300a. Control and the like are feasible, and any of P, I, and D controls may be used, and follow-up control by the steering angle control unit 920 and the twist angle control unit 300a is generally used. The control structure may be used. The steering angle control unit 920 is used in a vehicle device as long as it has a control configuration in which the actual angle (here, the steering angle θt) follows the target angle (here, the target steering angle θtref). The control configuration is not limited, and for example, the control configuration used in an industrial positioning device, an industrial robot, or the like may be applied.

In the third embodiment, as shown in FIG. 25, one ECU 50 controls the reaction force device 60 and the drive device 70, but an ECU for the reaction force device 60 and an ECU for the drive device 70 are provided, respectively. You may. In this case, the ECUs transmit and receive data by communication. Further, the SBW system shown in FIG. 25 does not have a mechanical coupling between the reaction force device 60 and the drive device 70, but when an abnormality occurs in the system, the column shaft 2 and the steering mechanism are clutched or the like. The present disclosure is also applicable to SBW systems provided with a mechanical torque transmission mechanism that mechanically couples with. In such an SBW system, when the system is normal, the clutch is turned off to open the mechanical torque transmission, and when the system is abnormal, the clutch is turned on to enable the mechanical torque transmission.

The twist angle control units 300 and 300a in the above-described first to third embodiments directly calculate the motor current command value Imc and the assist current command value Iac, but before calculating them, the motor to be output first. After calculating the torque (target torque), the motor current command value and the assist current command value may be calculated. In this case, in order to obtain the motor current command value and the assist current command value from the motor torque, the generally used relationship between the motor current and the motor torque is used.

Also in the present embodiment, the same effect as that of the first embodiment can be obtained by providing the target steering torque generation unit 202 with the steering reaction force correction unit 280 described in the above-described first embodiment.

The figures used above are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited thereto. Further, the above-described embodiment is an example of a preferred embodiment of the present disclosure, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present disclosure. Further, as long as the mechanism has an arbitrary spring constant between the handle and the motor or the reaction force motor, the mechanism may not be limited to the torsion bar.

1 Handle 2 Column shaft 2A Torsion bar 3 Deceleration mechanism 4a, 4b Universal joint 5 Pinion rack mechanism 6a, 6b Tie rod 7a, 7b Hub unit 8L, 8R Steering wheel 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 13 Battery 14 Steering angle sensor 15 Low-speed operation mode detection unit (judgment unit)
20 Motor 30, 30a, 50 Control unit (ECU)
60 Reaction force device 61 Reaction force motor 70 Drive device 71 Drive motor 72 Gear 73 Angle sensor 100 EPS Steering system / Vehicle system 130 Current control unit 140 Motor current detector 200, 201, 202 Target steering torque generator 210 Basic map Part 211 Multiplying part 213 Code extraction part 220 Differentiation part 230 Damper gain map part 240 Hysteresis correction part 250 SAT information correction part 251 SAT calculation part 251A Conversion part 251B Angular velocity calculation part 251C Angular velocity calculation part 251D, 251E, 251F Block 251H, 251I , 251J Adder 252 Filter part 253 Steering torque sensitive gain part 254 Vehicle speed sensitive gain part 255 Steering angle sensitive gain part 256 Limiting part 260, 264 Multiplying part 261,262,265 Adding part 280 Steering reaction force correction part 281 Correction gain generating part 282 Correction torque map 283 Code extraction unit 284 Multiplying unit 300,300a Twist angle control unit 310 Twist angle feedback (FB) Compensation unit 320 Twist angular velocity calculation unit 330 Speed control unit 331 Integration unit 332 Proportional unit 333,334 Subtraction unit 340 Stabilization Compensation section 350 Output limiting section 360 Steering angle disturbance compensation section 361 Subtraction section 362, 363 Addition section 370 Reduction ratio section 400 Steering direction determination section 500 Conversion section 910 Target steering angle generator 920 Steering angle control section 921 Steering angle feedback (FB) Compensation section 922 Steering angular velocity calculation section 923 Speed control section 926 Output limit section 927 Subtraction section 930 Current control section 931 Limiting section 933 Correction section 932 Rate limiting section 940 Motor current detector 1001 CPU
1005 Interface 1006 A / D Converter 1007 PWM Controller 1100 Control Computer (MCU)

Claims (5)

A vehicle steering device that assists and controls the steering system of a vehicle by driving and controlling a motor that assists the steering force.
As the driving mode of the vehicle,
1st mode and
A second mode different from the first mode,
Have,
In a predetermined region where the absolute value of the steering angle of the steering wheel is zero or more, the rate of change of the target steering torque of the motor in the second mode becomes the first mode or more, and in a region other than the predetermined region, the second mode The steering device for a vehicle in which the rate of change of the target steering torque is smaller than that of the first mode. When a predetermined operation is detected, a determination unit that determines the second mode and a determination unit
A first torque signal that increases along a curve whose rate of change gradually decreases as the absolute value of the steering angle of the handle increases is generated, and a correction gain is applied to the second torque signal generated based on the first torque signal. A target steering torque generating unit that generates the target steering torque by multiplying the third torque signal to generate the third torque signal and adding the fourth torque signal to the third torque signal.
With
The target steering torque generator
The claim that in the second mode, the positive correction gain of less than 1 is generated, and the fourth torque signal having a slope larger than that of the first torque signal when the absolute value of the steering angle is zero is generated. The vehicle steering device according to 1. The vehicle steering device according to claim 2, wherein the fourth torque signal in the second mode is a constant value in a region where the steering angle is a predetermined value or more. The target steering torque generator
The vehicle steering device according to claim 2 or 3, wherein in the first mode, the correction gain is set to 1, and the fourth torque signal is set to zero. The vehicle steering device according to any one of claims 1 to 4, wherein the target steering torque in the second mode is smaller than the target steering torque in the first mode.

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