JP7388995B2 - Steering control device - Google Patents

Description

The present invention relates to a steering control device.

A steering system used in a vehicle includes a steering mechanism that enables the operation of a steering wheel, and a steering mechanism that uses motor torque, which is the output of a motor, to move a steering shaft to steer the wheels of the vehicle. It consists of a mechanism. Patent Document 1 discloses an example of a so-called steer-by-wire steering device, which has a structure in which a power transmission path between the steering mechanism and the steering mechanism is separated.

Patent Document 1 discloses that a steering angle, which is an angle at which a steering wheel is operated, is detected as the state of the steering mechanism. The detected steering angle is used to calculate a target control amount that is a target control amount for controlling the output of a motor provided in the steering mechanism.

JP 2019-131072 Publication

Here, in the above-mentioned steering device, a plurality of control states for controlling the target control amount of the steering mechanism can be prepared. In addition, it is possible to maintain desired functions of the steering system while switching between a plurality of control states. For example, it is possible to switch to a backup control state for controlling the target control amount so that the target control amount can be controlled even if some abnormality occurs.

However, in the above case, there may be a difference in the target control amount before and after switching the control state. In this case, the steering mechanism makes a movement that is not intended by the driver, and this causes a sense of discomfort that is conveyed to the driver.

An object of the present invention is to provide a steering control device that can suppress the sense of discomfort conveyed to the driver.

A steering control device that solves the above problems controls a steering device that includes a steering mechanism that has a motor that generates a motor torque that is a power for moving a steering shaft to steer steering wheels of a vehicle, a control section that controls a target control amount that is a target of a control amount for controlling the motor torque of the motor, the control section controlling a first target control amount obtained under predetermined conditions; The control state can be switched between a plurality of control states including a control state and a second control state that controls a second target control amount obtained under conditions different from the first target control amount. is switched, an offset compensation calculation for compensating so as to shift the target control amount after switching, which is controlled in the control state after switching, toward the target control amount before switching, which is controlled in the control state before switching. an offset amount acquisition processing section that acquires, when the control state is switched, the difference between the target control amounts before and after switching as an offset amount that is an amount to be shifted through the compensation; and an offset amount gradual change processing section that changes the offset amount acquired by the offset amount acquisition processing section so that it gradually becomes smaller.

According to the above configuration, when the control state is switched, the target control amount after switching is set to the target control amount before switching so that the difference from the target control amount before switching is eliminated through compensation using the offset amount. Shifted to the control amount side. Particularly at the moment of switching, the target control amount after switching is compensated to almost match the target control amount before switching. Thereafter, as the offset amount gradually decreases, the target control amount after switching approaches the original target control amount obtained through calculation in the control state after switching, and eventually matches the original target control amount. I come to do it. As a result, even if there is a difference in the target control amount before and after switching the control state, it is possible to prevent this difference from appearing as a movement that is not intended by the driver of the steering mechanism. Therefore, the sense of discomfort conveyed to the driver can be suppressed.

As described above, when a configuration in which the control state is switched is adopted, a backup control state is prepared to maintain the desired function of the steering system in the event of an abnormality in order to cope with an abnormality that may occur. is possible.

Specifically, in the above steering control device, the first target control amount is calculated under a condition using a first state variable detected by a first detection device, and the second target control amount is calculated using a first state variable detected by a first detection device. The calculation is performed under conditions using a second state variable detected by two detection devices, and the first detection device and the second detection device detect independent state variables while detecting the same detection target. A case may be considered in which there are redundant detection devices that perform detection respectively.

According to the above configuration, when an abnormality occurs in the first detection device, it is possible to switch to the second backup control state for calculating the target control amount based on the detection result of the redundant second detection device. can. This is to avoid calculating the target control amount based on the detection result by the first detection device. In this case, even if there is a difference between the state variables before and after switching the control state, the target control amount after switching the control state should be prevented from differing from the target control amount before switching. You will be able to do this. Therefore, even when switching to the backup control state due to an abnormality occurring in the first detection device, it is possible to prevent the steering mechanism from moving unintentionally by the driver. can.

Here, regarding the offset amount, since it forcibly shifts the target control amount after switching, we would like to eliminate it as soon as possible, but if the amount of decrease in the offset amount is too large, the operation of the steering mechanism will eventually be affected. It appears as a movement that the person did not intend.

Therefore, in the above-mentioned steering control device, the offset amount gradual change processing section determines a reduction amount for reducing the offset amount based on at least one of the running state of the vehicle and the steering state of the steering mechanism. It is preferable to change it.

For example, if the vehicle is running at a relatively high speed, or the steering mechanism is turning the steering wheel, it may be possible to increase the amount of reduction to reduce the amount of offset. It can be said that even if the steering mechanism appears as a movement that is not intended by the driver, it is difficult to convey the sense of discomfort to the driver. Therefore, in the above configuration, it is effective to take into account the driving condition of the vehicle and the steering condition of the steering mechanism, and to devise ways to eliminate the amount of offset as quickly as possible while suppressing the driver's discomfort. It is.

Further, in the above steering control device, when the offset amount exists, the offset amount gradual change processing section changes the offset amount by at least a minimum amount regardless of the running state of the vehicle and the steering state of the steering mechanism. It is preferable to have a lower limit guard processing section for reducing the amount.

According to the above configuration, it is possible to prevent the amount of offset from remaining constantly, and it is possible to effectively reduce the amount of offset.

According to the steering control device of the present invention, it is possible to suppress the sense of discomfort conveyed to the driver.

A schematic configuration diagram of a steering device. FIG. 3 is a block diagram showing the functions of a steering control device. FIG. 3 is a block diagram showing the functions of an offset compensation calculation section. FIG. 3 is a block diagram showing the functions of an offset amount gradual change processing section. (a) is a schematic diagram illustrating the manner in which the target pinion angle changes, (b) is a schematic diagram illustrating the manner in which the offset amount changes, and (c) is a schematic diagram illustrating the manner in which the state FLG changes.

An embodiment in which a steering control device is applied to a steer-by-wire type steering device will be described below with reference to the drawings.
As shown in FIG. 1, a vehicle steering system 10 is a steer-by-wire type steering system. The steering device 10 includes a steering control device 50 that controls the operation of the steering device 10. The steering device 10 includes a steering mechanism SK that is steered by the driver via the steering wheel 11, and a steering mechanism TK that steers the steered wheels 16 in accordance with the steering of the steering mechanism SK by the driver. The steering device 10 of this embodiment has a structure in which the power transmission path between the steering mechanism SK and the steering mechanism TK is mechanically separated at all times.

The steering mechanism SK has a steering shaft 12 connected to a steering wheel 11. The steering mechanism TK has a steering shaft 14 that extends along the vehicle width direction, which is the left-right direction in FIG. Left and right steered wheels 16 are connected to both ends of the steered shaft 14 via tie rods 15, respectively. By linearly moving the steered shaft 14, the steered angle θw of the steered wheels 16 is changed.

Further, the steering mechanism SK includes a reaction force motor 31, a deceleration mechanism 32, a first rotation angle sensor 331, a second rotation angle sensor 332, and a torque sensor 34 as a configuration for generating a steering reaction force. . Incidentally, the steering reaction force refers to a force that acts in a direction opposite to the direction in which the steering wheel 11 is operated by the driver. By applying a steering reaction force to the steering wheel 11, it is possible to give the driver an appropriate feeling of response.

The reaction force motor 31 is a source of steering reaction force. As the reaction motor 31, for example, a three-phase brushless motor is employed. The reaction motor 31, to be more precise, its rotating shaft is connected to the steering shaft 12 via a speed reduction mechanism 32. The torque of the reaction force motor 31 is applied to the steering shaft 12 as a steering reaction force.

Each rotation angle sensor 331, 332 is provided on the reaction force motor 31. The first rotation angle sensor 331 detects the rotation angle θa1 of the reaction force motor 31. The second rotation angle sensor 332 detects the rotation angle θa2 of the reaction force motor 31. Each rotation angle sensor 331, 332 is a redundant rotation angle sensor that detects an independent rotation angle while detecting the rotation angle of the same reaction force motor 31. The rotation angles θa1 and θa2 of the reaction force motor 31 are used to calculate the steering angle θs. The reaction motor 31 and the steering shaft 12 are interlocked via a speed reduction mechanism 32. Therefore, there is a correlation between the rotation angles θa1 and θa2 of the reaction motor 31, the rotation angle of the steering shaft 12, and the steering angle θs, which is the rotation angle of the steering wheel 11. Therefore, the steering angle θs can be determined based on the rotation angles θa1 and θa2 of the reaction motor 31. Note that the first rotation angle sensor 331 is a first detection device, and the rotation angle θa1 detected thereby is an example of a first state variable. Further, the second rotation angle sensor 332 is a second detection device, and the rotation angle θa2 detected thereby is an example of a second state variable.

The torque sensor 34 detects the steering torque Th applied to the steering shaft 12 through a rotational operation of the steering wheel 11. The torque sensor 34 is provided in a portion of the steering shaft 12 closer to the steering wheel 11 than the speed reduction mechanism 32 is.

The steering mechanism TK includes a steering motor 41, a deceleration mechanism 42, and a rotation angle sensor 43 as a configuration for generating a steering force that is the power for steering the steered wheels 16.
The steering motor 41 is a source of steering force. As the steering motor 41, for example, a three-phase brushless motor is employed. A rotating shaft of the steering motor 41 is connected to a pinion shaft 44 via a speed reduction mechanism 42 . The pinion teeth 44a of the pinion shaft 44 are engaged with the rack teeth 14b of the steered shaft 14. The torque of the steering motor 41 is applied to the steering shaft 14 via the pinion shaft 44 as a steering force. In accordance with the rotation of the steering motor 41, the steering shaft 14 moves along the vehicle width direction, which is the left-right direction in FIG.

The rotation angle sensor 43 is provided in the steering motor 41. The rotation angle sensor 43 detects the rotation angle θb of the steering motor 41.
Incidentally, the steering device 10 has a pinion shaft 13. The pinion shaft 13 is provided so as to intersect with the steered shaft 14. The pinion teeth 13a of the pinion shaft 13 are engaged with the rack teeth 14a of the steered shaft 14. The reason for providing the pinion shaft 13 is to support the steering shaft 14 together with the pinion shaft 44 inside a housing (not shown). That is, the steering shaft 14 is supported movably along its axial direction by a support mechanism (not shown) provided in the steering device 10 and is pressed toward the pinion shafts 13 and 44. Thereby, the steered shaft 14 is supported inside the housing. However, other support mechanisms may be provided to support the steered shaft 14 in the housing without using the pinion shaft 13.

As shown in FIG. 1, a steering control device 50 that controls the drive of each motor 31, 41 is connected to the reaction motor 31 and the steering motor 41. The steering control device 50 controls the drive of each motor 31, 41 by controlling the supply of current, which is a control amount of each motor 31, 41, based on the detection results of various sensors. Examples of the various sensors include a vehicle speed sensor 501, a torque sensor 34, rotation angle sensors 331 and 332, and a rotation angle sensor 43. Vehicle speed sensor 501 detects a vehicle speed value V, which is the traveling speed of the vehicle.

Next, the configuration of the steering control device 50 will be explained.
The steering control device 50 includes a central processing unit (CPU) and a memory (not shown), and the CPU executes a program stored in the memory at every predetermined calculation cycle. As a result, various processes are executed.

FIG. 2 shows part of the processing executed by the steering control device 50. The processing shown in FIG. 2 is a part of the processing that is realized by the CPU executing the program stored in the memory, and is described for each type of processing that is realized.

The steering control device 50 includes a steering side control section 50a that controls power supply to the reaction force motor 31. The steering side control section 50a has a steering side current sensor 55. The steering side current sensor 55 detects a steering side actual current value obtained from the current value of each phase of the reaction force motor 31 flowing through the connection line between the steering side control unit 50a and the motor coil of each phase of the reaction force motor 31. Detect Ia. The steering-side current sensor 55 obtains, as a current, a voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the reaction motor 31. Note that, in FIG. 2, for convenience of explanation, the connection lines for each phase and the current sensors for each phase are shown together as one.

The steering control device 50 also includes a steering side control section 50b that controls power supply to the steering motor 41. The steered side control section 50b has a steered side current sensor 65. The steered side current sensor 65 is a steered side current sensor obtained from the current value of each phase of the steered motor 41 flowing through a connection line between the steered side control unit 50b and the motor coil of each phase of the steered motor 41. Detect the actual current value Ib. The steering side current sensor 65 acquires, as a current, the voltage drop across a shunt resistor connected to the source side of each switching element in an inverter (not shown) provided corresponding to the steering motor 41. Note that, in FIG. 2, for convenience of explanation, the connection lines for each phase and the current sensors for each phase are shown together as one.

Next, the function of the steering side control section 50a will be explained.
A steering torque Th, a vehicle speed value V, each rotation angle θa1, θa2, a steering side actual current value Ib, which will be described later, and a pinion angle θp, which will be described later, are input to the steering side control unit 50a. The steering side control unit 50a controls the power supply to the reaction force motor 31 based on the steering torque Th, the vehicle speed value V, each rotation angle θa1, θa2, a steering side actual current value Ib described below, and a pinion angle θp described below. do. Note that the pinion angle θp is calculated based on the steering side rotation angle θb.

The steering side control section 50a includes an abnormality detection section 51, a steering angle calculation section 52, a steering reaction force command value calculation section 53, and an energization control section 54.
The rotation angles θa1 and θa2 are input to the abnormality detection unit 51. The abnormality detection unit 51 detects an abnormality in each of the rotation angle sensors 331 and 332 based on the rotation angles θa1 and θa2. The abnormality detection unit 51 detects an abnormality in each rotation angle sensor 331, 332 based on whether or not the rotation angles θa1, θa2 are input at predetermined intervals, and based on comparison with the previous values of the rotation angles θa1, θa2. To detect. For example, the abnormality detection unit 51 detects an abnormality in the first rotation angle sensor 331 when the rotation angle θa1 is no longer input. In this case, when the rotation angle θa1 is input, the abnormality detection unit 51 detects that the first rotation angle sensor 331 has returned to normal. Then, when the abnormality detection unit 51 detects that the first rotation angle sensor 331 is normal and the second rotation angle sensor 332 is normal, it generates a state FLG1 indicating that the sensor is normal. On the other hand, when the abnormality detection unit 51 detects an abnormality in the first rotation angle sensor 331 and detects that the second rotation angle sensor 332 is normal, it generates a state FLG2 indicating an abnormality in the sensor. The states FLG1 and FLG2 obtained in this way are output to the steering angle calculation section 52, the energization control section 54, and the steering side control section 50b.

The state FLG and rotation angles θa1 and θa2 are input to the steering angle calculation unit 52. The steering angle calculation unit 52 calculates the rotation angles θa1 and θa2 by counting the number of revolutions of the reaction force motor 31 from the steering neutral position, which is the position of the steering wheel 11 when the vehicle is moving straight, for example. Convert to an integrated angle that includes a range exceeding °. The steering angle calculation unit 52 calculates the steering angle θs by multiplying the obtained integrated angle by a conversion coefficient based on the rotational speed ratio of the speed reduction mechanism 32. Note that the steering angle θs is positive when the angle is to the right of the steering neutral position, and negative when the angle is to the left of the steering neutral position. The steering angle calculation unit 52 calculates the steering angle θs using the first rotation angle sensor 331 when the state FLG1 is input. On the other hand, the steering angle calculating section 52 calculates the steering angle θs using the second rotation angle sensor 332 when the state FLG2 is input. The steering angle θs thus obtained is output to the steering side control section 50b.

The steering torque Th, the vehicle speed value V, the steered side actual current value Ib, and the pinion angle θp are input to the steering reaction force command value calculation unit 53. The steering reaction force command value calculation unit 53 generates a steering reaction force command as a target control amount that is a target of the steering reaction force, based on the steering torque Th, the vehicle speed value V, the actual steering side current value Ib, and the pinion angle θp. Calculate the value T*. The steering reaction force command value T* obtained in this way is output to the energization control section 54.

The state FLG, the steering reaction force command value T*, the rotation angles θa1, θa2, and the steering-side actual current value Ia are input to the energization control unit 54. The energization control unit 54 calculates a current command value for the reaction force motor 31 based on the steering reaction force command value T*. Then, the energization control unit 54 calculates the deviation between the current command value and the current value on the dq coordinate obtained by converting the steering-side actual current value Ia detected through the steering-side current sensor 55 based on the rotation angles θa1 and θa2. is determined, and the power supply to the reaction force motor 31 is controlled so as to eliminate the deviation. In this case, when the state FLG1 is input, the energization control unit 54 converts the actual steering-side current value Ia detected through the steering-side current sensor 55 based on the rotation angle θa1 to convert the current value on the dq coordinates to the current value on the dq coordinates. Use. On the other hand, when the state FLG2 is input, the energization control unit 54 converts the steering-side actual current value Ia detected through the steering-side current sensor 55 based on the rotation angle θa2, and converts the current value on the dq coordinates. use Thereby, the reaction force motor 31 generates torque according to the steering reaction force command value T*. It is possible to provide the driver with an appropriate feeling of response depending on the road reaction force.

Next, the function of the steered side control section 50b will be explained.
The vehicle speed value V, the state FLG, the rotation angle θb, and the steering angle θs are input to the steering side control unit 50b. The steering side control unit 50b controls power supply to the steering motor 41 based on the vehicle speed value V, the state FLG, the rotation angle θb, and the steering angle θs.

The steering side control section 50b includes a pinion angle calculation section 61, a target pinion angle calculation section 62, a pinion angle feedback control section ("pinion angle F/B control section" in the figure) 63, and an energization control section 64. have.

The rotation angle θb is input to the pinion angle calculation section 61. The pinion angle calculation unit 61 calculates the rotation angle θb by, for example, 360° by counting the number of rotations of the steering motor 41 from the rack neutral position, which is the position of the steering shaft 14 when the vehicle is traveling straight. Convert to an integrated angle that includes the range exceeding . The pinion angle calculation unit 61 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 44, by multiplying the integrated angle obtained by the conversion by a conversion coefficient based on the rotational speed ratio of the speed reduction mechanism 42. Note that the pinion angle θp is positive when the angle is to the right of the rack neutral position, and negative when the pinion angle is to the left of the rack neutral position. The steering motor 41 and the pinion shaft 44 are interlocked via a speed reduction mechanism 42 . Therefore, there is a correlation between the rotation angle θb of the steering motor 41 and the pinion angle θp. Using this correlation, the pinion angle θp can be determined from the rotation angle θb of the steering motor 41. Further, the pinion shaft 44 is meshed with the steered shaft 14. Therefore, there is also a correlation between the pinion angle θp and the amount of movement of the steered shaft 14. That is, the pinion angle θp is a value that reflects the steered angle θw of the steered wheels 16. The pinion angle θp obtained in this way is output to the pinion angle feedback control section 63 and the steering reaction force command value calculation section 53.

The vehicle speed value V, the state FLG, and the steering angle θs are input to the target pinion angle calculation unit 62. The target pinion angle calculation unit 62 calculates a target pinion angle θp* as a target control amount that is a target for the pinion angle θp, based on the vehicle speed value V, the state FLG, and the steering angle θs.

Specifically, the target pinion angle calculation section 62 includes a steering angle ratio variable calculation section 67 and an offset compensation calculation section 68.
The vehicle speed value V and the steering angle θs are input to the steering angle ratio variable calculation unit 67. The steering angle ratio variable calculation unit 67 calculates the converted angle θvg by adding the adjustment amount Δθa to the steering angle θs. The steering angle ratio variable calculation unit 67 varies the adjustment amount Δθa for varying the steering angle ratio, which is the ratio of the converted angle θvg to the steering angle θs, in accordance with the vehicle speed value V. For example, the adjustment amount Δθa is varied so that the change in the converted angle θvg with respect to the change in the steering angle θs is larger when the vehicle speed value V is low than when it is high. The converted angle θvg thus obtained is output to the offset compensation calculation unit 68 and the subtracter 69, and is also output to the offset compensation calculation unit 68 as the converted angular velocity ωvg obtained by differentiating the converted angle θvg and passed through the differentiator 66. Output. The post-conversion angle θvg is an angle that is the base of the target pinion angle θp*. Further, the pinion angle θp is controlled based on the target pinion angle θp*. Therefore, there is also a correlation between the converted angle θvg and the pinion angle θp. That is, the converted angular velocity ωvg obtained based on the converted angle θvg is a value that reflects the steered angle θw of the steered wheels 16 as the steered state of the steered mechanism TK.

The offset compensation calculation unit 68 receives the vehicle speed value V, the state FLG, the converted angle θvg, the converted angular velocity ωvg, and the target pinion angle θp*. The offset compensation calculation unit 68 calculates an offset amount, which is a compensation amount when calculating the target pinion angle θp*, based on the vehicle speed value V, the state FLG, the converted angle θvg, the converted angular velocity ωvg, and the target pinion angle θp*. Calculate θofst. The offset amount θofst will be explained in detail later. The offset amount θofst thus obtained is subtracted from the converted angle θvg and outputted to the pinion angle feedback control unit 63 as a target pinion angle θp* obtained through a subtracter 69.

The pinion angle feedback control section 63 receives the target pinion angle θp* and the pinion angle θp. The pinion angle feedback control unit 63 calculates a steering force command value Tp* as a target control amount that is a target of the steering force through feedback control of the pinion angle θp in order to cause the pinion angle θp to follow the target pinion angle θp*. . The thus obtained steering force command value Tp* is output to the energization control section 64.

The energization control unit 64 receives the steering force command value Tp*, the rotation angle θb, and the actual steering-side current value Ib. The energization control unit 64 calculates a current command value for the steering motor 41 based on the steering force command value Tp*. Then, the energization control unit 54 calculates the deviation between the current command value and the current value on the dq coordinate obtained by converting the steering side actual current value Ib detected through the steering side current sensor 65 based on the rotation angle θb. is determined, and the power supply to the steering motor 41 is controlled so as to eliminate the deviation. As a result, the steering motor 41 rotates by an angle corresponding to the steering force command value Tp*.

The steering control device 50 has a plurality of control states including a first control state and a second control state. In the first control state, the target pinion angle θp*(1) is calculated based on the converted angle θvg(1) corresponding to the steering angle θs(1) obtained from the rotation angle θa1 detected by the first rotation angle sensor 331. control. In the second control state, the target pinion angle θp*(2) is calculated based on the converted angle θvg(2) corresponding to the steering angle θs(2) obtained from the rotation angle θa2 detected by the second rotation angle sensor 332. control. The steering control device 50 switches between a first control state and a second control state according to the abnormality detection results of the rotation angle sensors 331 and 332 of the abnormality detection unit 51.

Specifically, the steering control device 50 basically switches to the first control state based on the state FLG1, and if it is determined that the first control state cannot be continued, the steering control device 50 switches to the second control state. Switch. The determination that the first control state cannot be continued is linked to the detection of an abnormality in the first rotation angle sensor 331, that is, the state FLG2. Thereby, the second control state functions as a control state that backs up the first control state. Note that the steering control device 50 switches to the first control state when it is determined that it is possible to return to the first control state while switching to the second control state during backup based on the state FLG2. The determination that it is possible to return to the first control state is linked to the fact that the first rotation angle sensor 331 normally detects the return, that is, the state is FLG1.

Here, if there is a difference between the steering angle θs(1) and the steering angle θs(2), these discrepancies will result in the difference between the target pinion angle θp*(1) and the target pinion angle θp*(2). ) appears as the difference between In other words, there is a possibility that a difference will occur in the target pinion angle θp* before and after switching the control state. In order to cope with this, the steering control device 50, that is, the steering side control section 50b has the function of an offset compensation calculation section 68.

The functions of the offset compensation calculation section 68 will be explained in more detail below.
As shown in FIG. 3, the offset compensation calculation unit 68 includes an offset amount acquisition processing unit 71, a calculation value switching unit 72, and an offset amount gradual change processing unit 73.

The converted angle θvg and the target pinion angle θp* are input to the offset amount acquisition processing unit 71. The offset amount acquisition processing unit 71 subtracts the target pinion angle θp* from the converted angle θvg and calculates the difference Δθvg obtained through the subtractor 74. The target pinion angle θp* input to the offset amount acquisition processing unit 71 is the previous value of the target pinion angle θp* used when controlling the steering motor 41 in the immediately preceding cycle (one cycle before). The target pinion angle θp* of the previous value is a value calculated based on the converted angle θvg of the previous value in the immediately preceding cycle (one cycle before), and is a value that reflects the converted angle θvg of the previous value. In other words, the difference Δθvg can also be said to be the difference between the post-conversion angle θvg obtained by subtracting the previous value of the post-conversion angle θvg from the current post-conversion angle θvg. The difference Δθvg thus obtained is output to the calculated value switching section 72.

The calculated value switching section 72 receives the state FLG, the difference Δθvg, and the offset amount θofst(-) of the previous value, which is the value held in the previous cycle (one cycle ago) through the previous value holding unit 75. The difference Δθvg is input to the first input N1 of the calculated value switching unit 72, and the offset amount θofst(-) is input to the second input N2 of the calculated value switching unit 72.

When a state FLG different from the previous value state FLG, which is the value of the immediately preceding cycle (one cycle before), is input, the calculated value switching unit 72 converts the difference Δθvg input to the first input N1 into an offset amount θofst. The selection state is controlled so that it is output as the offset basic amount θofstb, which is the basic amount of . The selection state in which the difference Δθvg is output as the basic offset amount θofstb occurs instantaneously when the state FLG1 changes to the state FLG2. The time of change from state FLG1 to state FLG2 is the time of switching from the first control state to the second control state. This also applies to the time of switching from the second control state to the first control state, which is the time of change from state FLG2 to state FLG1.

On the other hand, when the same state FLG is input to the state FLG of the previous value, which is the value of the immediately preceding cycle (one cycle before), the calculated value switching unit 72 changes the offset amount θofst that is input to the second input N2. The selection state is controlled so that (-) is output as the offset basic amount θofstb. The selection state in which the offset amount θofst(-) is output as the offset basic amount θofstb is continuously maintained while the input to the state FLG1 or the input to the state FLG2 is maintained. While the input of state FLG1 is maintained, the first control state is maintained. While the input of state FLG2 is maintained, the second control state is maintained.

The basic offset amount θofstb selected as an appropriate value in this way is, for example, when the state FLG changes from state FLG1 to state FLG2, the difference Δθvg calculated by the offset amount acquisition processing section 71 is calculated by the offset amount gradual change processing section 73. Output. Further, as for the basic offset amount θofstb, the offset amount θofst(-), which is the previous value of the offset amount gradual change processing section 73, is output to the offset amount gradual change processing section 73 when the state FLG is maintained.

The difference Δθvg takes a value other than zero if there is a difference between the steering angle θs(1) and the steering angle θs(2) when switching the control state. In contrast, the calculated value switching unit 72 outputs the difference Δθvg that is input to the first input N1 when switching the control state, so that the difference Δθvg that may occur due to the switching of the control state is It operates so as to be reflected in the amount θofstb.

On the other hand, the difference Δθvg takes a value other than zero if there is a difference between the steering angle θs(1) and the steering angle θs(2) even when the control state is not switched. On the other hand, since the calculated value switching unit 72 does not output the difference Δθvg input to the first input N1 unless the control state is switched, the difference Δθvg that may occur other than when the control state is switched is offset It operates so as not to be reflected in the basic amount θofstb.

The offset amount gradual change processing section 73 receives the vehicle speed value V, the converted angular velocity ωvg, and the offset basic amount θofstb.
Specifically, as shown in FIG. 4, the offset amount gradual change processing section 73 includes a reduction gain map calculation section 81, a reduction amount map calculation section 82, a storage section 83, a lower limit guard processing section 84, and a lower limit guard processing section 84. It has a processing section 85.

The vehicle speed value V is input to the reduction gain map calculation unit 81 . The reduction gain map calculating section 81 is provided with a map that defines the relationship between the vehicle speed value V and the reduction gain G, and receives the vehicle speed value V as an input and performs a map calculation on the reduction gain G. The reduction gain G is a gain that functions to gradually reduce the offset amount θofst so that the target pinion angle θp* does not suddenly change due to the decrease in the offset amount θofst. In this case, the reduction gain G is calculated such that its absolute value increases as the vehicle speed value V increases, taking into account the driving state of the vehicle. The reduced gain G thus obtained is output to the multiplier 86.

The converted angular velocity ωvg is input to the reduction amount map calculation unit 82. The reduction amount map calculation unit 82 is equipped with a map that defines the relationship between the converted angular velocity ωvg and the reduced basic amount θdb, which is the basic amount of the reduced amount θd. Perform a map operation. The basic decrease amount θdb is a component that functions to gradually reduce the offset amount θofst so that the target pinion angle θp* does not change suddenly due to a decrease in the offset amount θofst. In this case, the basic amount of decrease θdb is such that the absolute value increases as the amount of change in the converted angular velocity ωvg, that is, the steering angle θw of the steered wheels 16, increases, taking into consideration the steering state of the steering mechanism TK. Calculated. The basic decrease amount θdb obtained in this way is multiplied by the decrease gain G and outputted to the lower limit guard processing unit 84 as a decrease amount θd obtained through the multiplier 86.

The storage unit 83 is a predetermined storage area of a memory (not shown) in which the minimum amount θdmin of the decrease amount θd is stored. The minimum amount θdmin is a component that functions to reduce the offset amount θofst so that the offset amount θofst does not remain constant. The minimum amount θdmin is set to a value within a range that is determined experimentally as an index to ensure a minimum amount of decrease θd even if the decrease amount θd output by the multiplier 86 is smaller than the minimum amount θdmin. . The minimum amount θdmin thus obtained is output to the lower limit guard processing section 84.

The lower limit guard processing unit 84 receives the decrease amount θd output from the multiplier 86 and the minimum amount θdmin output from the storage unit 83. The decrease amount θd is input to the first input M1 of the lower limit guard processing unit 84, and the minimum amount θdmin is input to the second input M2 of the lower limit guard processing unit 84. The lower limit guard processing unit 84 is configured to switch its selection state so that it can switch which of the reduction amount θd and the minimum amount θdmin to output as the reduction amount θd.

Specifically, the lower limit guard processing unit 84 determines whether the decrease amount θd input to the first input M1 is greater than or equal to the minimum amount θdmin. Then, when the decrease amount θd input to the first input M1 is greater than or equal to the minimum amount θdmin, the lower limit guard processing unit 84 outputs the decrease amount θd input to the first input M1 as the final decrease amount θd. The selection state of the lower limit guard processing unit 84 is controlled so that the lower limit guard processing unit 84 is selected. On the other hand, the lower limit guard processing unit 84 performs lower limit guard processing so that when the decrease amount θd input to the first input M1 is smaller than the minimum amount θdmin, the minimum amount θdmin is output as the final decrease amount θd. The selection state of section 84 is controlled. That is, the lower limit guard processing unit 84 operates to reduce the offset amount θofst by at least the minimum amount θdmin so that the offset amount θofst does not remain constant. The decrease amount θd selected as an appropriate value in this manner is output to the multiplier 87.

The basic offset amount θofstb is input to the code processing unit 85. The sign processing unit 85 determines the sign of the basic offset amount θofstb, and calculates either "1" or "-1" as a value according to the sign. The code processing unit 85 calculates "1" when the basic offset amount θofstb is a positive value, and calculates "-1" when it is a negative value. The value of "1" or "-1" obtained in this way is multiplied by the decrease amount θd and outputted to the subtractor 88 as the final decrease amount θd obtained through the multiplier 87, and then is obtained from the offset basic amount θofstb. The offset amount θofst obtained through the subtracter 88 is output to the subtracter 69 .

Note that the offset amount gradual change processing unit 73 operates so that the decrease amount θd output from the lower limit guard processing unit 84 is reflected in the offset amount θofst when the offset amount θofst is a value other than zero. On the other hand, when the offset amount θofst has a zero value, the offset amount gradual change processing unit 73 operates so that the decrease amount θd output from the lower limit guard processing unit 84 is not reflected on the offset amount θofst. Further, the offset amount gradual change processing unit 73 operates so that the sign of the offset basic amount θofstb is not reversed as a result of the reduction amount θd being reflected. That is, when the absolute value of the offset basic amount θofstb is smaller than the absolute value of the decrease amount θd, the offset amount gradual change processing unit 73 makes the absolute value of the reduction amount θd the same value as the absolute value of the offset basic amount θofstb. It works like this.

The operation of this embodiment will be explained below.
FIGS. 5(a) to 5(c) show various change modes, taking as an example the case where the state FLG changes to the state FLG2 indicating an abnormality of the sensor at the timing of time t1 between the state FLG1 indicating the normality of the sensor. It shows. In the following, it is assumed that the offset amount θofst at time "0" is zero value, and that the steering angle θs(1) corresponding to the rotation angle θa1 and the steering angle θs(2) corresponding to the rotation angle θa2 are constant. The description will be made on the assumption that the angle changes with a predetermined angular difference a and that the vehicle speed value V is constant.

As shown in FIG. 5(a), there is an angular difference between the converted angle θvg(1) shown by the dashed-dot line at the bottom of the graph and the converted angle θvg(2) shown by the dashed-double line at the top of the graph. It changes with a. This is a change in the target pinion angle θp*(1) calculated based on the converted angle θvg(1) and a change in the target pinion angle θp*(2) calculated based on the converted angle θvg(2). can be captured. Then, at time t1, the offset amount acquisition processing section 71 functions to calculate the angular difference a as the difference Δθvg.

In this case, as shown in FIG. 5B, the calculated value switching unit 72 functions to calculate the offset basic amount θofstb indicating the angular difference a, and this is calculated as the offset amount θofst. After time t1, the offset amount θofst gradually decreases due to the function of the offset amount gradual change processing unit 73. The offset amount θofst gradually decreases until it reaches a zero value at time t2. The offset amount θofst that changes in this way is reflected by the function of the offset compensation calculation unit 68 so as to be subtracted from the current converted angle θvg to compensate for the target pinion angle θp*.

As a result, as shown by the solid line in FIG. 5(a), when the control state is switched, the target pinion angle θp*, which is the target control amount after switching after time t1, is changed through compensation using the offset amount θofst. , is shifted toward the target pinion angle θp*(1), which is the target control amount before switching before time t1. Particularly at the moment of switching, the target pinion angle θp* is compensated to substantially match the target pinion angle θp*(1).

Thereafter, as shown by the solid line in the figure, the target pinion angle θp* approaches the original target pinion angle θp*(2) as the offset amount θofst gradually decreases. Then, the target pinion angle θp* changes to match the original target pinion angle θp*(2) at time t2 when the offset amount θofst becomes zero.

The effects of this embodiment will be explained below.
(1) In this embodiment, as shown by the solid line in FIG. 5(a), the difference between the target pinion angle θp*(1) and the target pinion angle θp*(2) before and after switching the control state Even if there is a difference, it is possible to prevent such a difference from appearing as a change in the target pinion angle θp* used for actual control. In other words, it is possible to prevent the steering mechanism TK from appearing as an unintended movement by the driver. Therefore, the driver's discomfort can be suppressed.

(2) According to the present embodiment, when an abnormality occurs in the first rotation angle sensor 331, the detection result of the redundant second rotation angle sensor 332 is used to calculate the target pinion angle θp*. It is possible to switch to a second control state for backup. This is to avoid calculating the target pinion angle θp* based on the detection result by the first rotation angle sensor 331. In this case, even if there is a difference between the steering angle θs(1) and the steering angle θs(2) before and after switching the control state, the target pinion angle θp* after switching the control state is It becomes possible to suppress the occurrence of a difference with respect to the target pinion angle θp*. Therefore, even when switching to the backup control state due to an abnormality occurring in the first rotation angle sensor 331, the steering mechanism TK is prevented from moving unintended by the driver. be able to.

(3) Here, regarding the offset amount θofst, since it forcibly shifts the original target pinion angle θp*(2) after switching, we would like to eliminate it as soon as possible. If it is made too large, it will eventually appear as a movement that is not intended by the driver of the steering mechanism TK.

Therefore, the offset amount gradual change processing section 73 is designed to have the functions of a reduction gain map calculation section 81 that takes into account the running state of the vehicle, and a reduction amount map calculation section 82 that takes into account the steering state of the steering mechanism TK. ing. Thereby, the larger the vehicle speed value V and the larger the amount of change in the turning angle θw of the steered wheels 16, the larger the reduction amount θd for reducing the offset amount θofst. Therefore, it is possible to suppress the driver's discomfort and to eliminate the offset amount θofst as quickly as possible.

(4) The offset amount gradual change processing section 73 has the function of the lower limit guard processing section 84 that considers the minimum amount θdmin. Thereby, it is possible to prevent the offset amount θofst from remaining constantly, and it is possible to effectively reduce the offset amount θofst.

The above embodiment may be modified as follows. Further, the following other embodiments can be combined with each other within a technically consistent range.
- The offset amount gradual change processing section 73 may not have the function of the lower limit guard processing section 84 if there is no problem even if there is a situation where the offset amount θofst does not become small. In addition, the offset amount gradual change processing unit 73 may have a function of basically decreasing the offset amount θofst by the minimum amount θdmin. In this case, the reduction gain map calculation section 81 and the reduction amount map calculation section 82 can be deleted. Further, the offset amount gradual change processing unit 73 may reduce the offset amount θofst by multiplying the offset basic amount θofstb by a gain. The gain in this case may consider the same state as the reduction gain map calculation section 81 and the reduction amount map calculation section 82.

- In addition to the decrease gain map calculation unit 81 and the decrease amount map calculation unit 82, the offset amount gradual change processing unit 73 may include a calculation unit that takes into account other states. Further, the offset amount gradual change processing unit 73 may leave only one of the decrease gain map calculation unit 81 and the decrease amount map calculation unit 82, or may add a calculation unit that takes into account other states instead of both. The other state may be, for example, the current amount of the offset amount θofst, that is, the remaining amount. In this case, the degree of change in decrease may be made more gradual as the remaining amount is smaller.

- In the reduction gain map calculating section 81, the manner in which the reduction gain G changes can be changed as appropriate. For example, the vehicle speed value V may be classified into low speed, medium speed, high speed, etc., and the change mode of the reduction gain G may be made different for each classification, such as maintaining the reduction gain G constant in the case of low speed.

- In the reduction amount map calculation unit 82, the change mode of the basic reduction amount θdb can be changed as appropriate. For example, if the angular velocity ωvg after conversion is classified into small speed, medium speed, high speed, etc., and if the speed is small, the basic decrease amount θdb is kept constant, and the change mode of the basic decrease amount θdb is different for each classification. You can also let

- The reduction amount map calculation unit 82 can also use a pinion angular velocity obtained by differentiating the pinion angle θp instead of the converted angular velocity ωvg. In addition, the reduction amount map calculation unit 82 can also use the steering angle θs and the pinion angle θp to calculate the basic reduction amount θdb according to the angle at that time.

- The backup control state may be for an abnormality in the torque sensor by making the torque sensor 34 redundant, or may be for an abnormality in the power supply configuration by making the power supply configuration of the steering device 10 redundant, The steered side control section 50b may be made redundant to handle abnormalities in the steered side control section. When the steered side control section 50b is made redundant, for example, it is provided with a first steered side control section and a second steered side control section. In this case, the winding of the steering motor 41 is also made redundant, and the first steering side control section and the second steering side control section cooperate to control the drive of the steering motor 41. Further, the first steering side control section receives a component according to the detection result of the first rotation angle sensor 331, and the second steering side control section receives a component according to the detection result of the second rotation angle sensor 332. is input, and each of them individually calculates the target pinion angle θp*. Moreover, a master-slave control system is employed between the first steering side control section and the second steering side control section, for example. In this case, in the first control state where the first rotation angle sensor 331 is normal, the first steering side control section is the master control section, and the target pinion angle θp* calculated by the first steering side control section is Using this, each steering side control section cooperatively controls the drive of the steering motor 41. On the other hand, in the second control state where the first rotation angle sensor 331 is abnormal, the function of the first steering side control section is stopped and only the second steering side control is performed. The drive of the steering motor 41 is controlled using the target pinion angle θp* calculated by . Even in this case, there is a possibility that the target pinion angle θp* before and after switching the control state may deviate, as in the above embodiment. Similar to the above embodiment, this problem can be solved by applying the offset compensation calculation unit 68 of the above embodiment.

- The backup control state may be for an abnormality in the function of varying the steering angle ratio of the variable steering angle ratio calculating section 67. In this case, regarding the steering angle ratio variable calculation unit 67, when the vehicle speed sensor 501, that is, the vehicle speed value V is abnormal in the first control state in which the steering angle ratio is varied in which the vehicle speed sensor 501, that is, the vehicle speed value V is normal, Alternatively, the steering angle ratio may be switched to a second control state in which the steering angle ratio is fixed. Even in this case, there is a possibility that the target pinion angle θp* before and after switching the control state may deviate, as in the above embodiment. Similar to the above embodiment, this problem can be solved by applying the offset compensation calculation unit 68 of the above embodiment.

- The sensor that detects the rotation angle, which is a state variable used to calculate the target pinion angle θp* for each control state, may be one that detects independent rotation angles while different detection targets are used. For example, the steering device 10 may include a steering angle sensor that directly detects the steering angle θs of the steering shaft 12. In this case, the first rotation angle sensor 331 and the steering angle sensor are connected to the steering side control section 50a. Then, in the first control state in which the target pinion angle θp* is calculated using the rotation angle θa detected by the first rotation angle sensor 331, the steering side control unit 50b detects that the first rotation angle sensor 331 is abnormal. In this case, the control state may be switched to a second control state in which the target pinion angle θp* is calculated using the rotation angle detected by the steering angle sensor. Even in this case, there is a possibility that the target pinion angle θp* before and after switching the control state may deviate, as in the above embodiment. Similar to the above embodiment, this problem can be solved by applying the offset compensation calculation unit 68 of the above embodiment.

- Instead of obtaining the basic offset amount θofstb from the difference Δθvg, it can also be obtained from the difference between before and after switching the control state for rotation angle θa1 and rotation angle θa2, or from the difference before and after switching the control state for the target pinion angle θp*. It can also be obtained from the difference. In addition, the basic offset amount θofstb can also be obtained from the difference between before and after switching the control state regarding the converted angle θvg.

- The offset compensation calculation section 68 of the above embodiment may be added as a function of the steering side control section 50a. This is effective when calculating the steering reaction force command value T* based on the rotation angles θa1 and θa2, that is, the steering angle θs. In addition, this modification is effective when the backup control state is made redundant for the torque sensor 34 and is used in response to an abnormality in the torque sensor.

- The code processing unit 85 can also calculate and output "0 (zero value)" when the basic offset amount θofstb is a zero value. In this case, if the basic offset amount θofstb has a zero value, the decrease amount θd has a zero value. In other words, when applying this modification, the offset amount gradual change processing section 73 does not reflect the decrease amount θd output from the lower limit guard processing section 84 on the offset amount θofst when the offset amount θofst is a zero value. It can work like this.

- The steering angle ratio variable calculation unit 67 may vary the steering angle ratio in accordance with, for example, a yaw rate detected by a yaw rate sensor of the vehicle, in addition to the vehicle speed value V. In this case, the steering angle ratio variable calculation unit 67 fixes the steering angle ratio when the yaw rate sensor, that is, the yaw rate is abnormal, in the first control state in which the steering angle ratio is varied when the yaw rate sensor, that is, the yaw rate is normal. Alternatively, the control state may be changed to a second control state in which the vehicle speed is varied based only on the vehicle speed value V. Even in this case, there is a possibility that the target pinion angle θp* before and after switching the control state may deviate, as in the above embodiment. Similar to the above embodiment, this problem can be solved by applying the offset compensation calculation unit 68 of the above embodiment. This modification can be similarly applied to a case where the steering angle ratio is varied in accordance with the lateral acceleration sensor of the vehicle in addition to the vehicle speed value V.

- The pinion angle feedback control unit 63 may vary the F/B gain depending on the yaw rate detected by a yaw rate sensor of the vehicle, for example. In this case, regarding the pinion angle feedback control section 63, in the first control state in which the F/B gain is varied when the yaw rate sensor, that is, the yaw rate is normal, the F/B gain is changed when the yaw rate sensor, that is, the yaw rate is abnormal. You may make it switch to the 2nd control state which is fixed. Even in this case, there is a possibility that the target pinion angle θp* before and after switching the control state may deviate, as in the above embodiment. Similar to the above embodiment, this problem can be solved by applying the offset compensation calculation section 68 of the above embodiment. This modification can be similarly applied to the case where the F/B gain is varied according to other state variables.

- In the steering reaction force command value calculating section 53, when calculating the steering reaction force command value T*, it is sufficient to use at least the steering torque Th, and it is not necessary to use the vehicle speed value V, or it is possible to use a combination of other elements. It may also be used as

- In the above embodiment, the steering angle ratio may be fixed. In this case, the steering angle ratio variable calculation section 67 can be deleted.
- In the above embodiment, the steering motor 41 is arranged coaxially with the steering shaft 14, or is connected to the steering shaft 14 via a belt type reducer using a ball screw mechanism. You may also adopt one that connects.

- In the above embodiment, the CPU that constitutes the steering control device 50 is one or more processors that execute a computer program, or one or more application-specific integrated circuits that execute at least part of various processes. The present invention may be implemented as a dedicated hardware circuit, or as a circuit including a combination of the processor and the dedicated hardware circuit. Memory may also be comprised of any available media that can be accessed by a general purpose or special purpose computer.

- In the above embodiment, the steering device 10 has a linkless structure in which the steering mechanism SK and the steering mechanism TK are mechanically separated at all times. In this way, the steering mechanism SK and the steering mechanism TK may be mechanically separated by the clutch 21. Further, the steering device 10 may be an electric power steering device that provides an assist force that is a force for assisting the steering of the steering wheel 11. In this case, the steering wheel 11 is mechanically connected to the pinion shaft 13 via the steering shaft 12.

10... Steering device 14... Steered shaft 16... Steered wheel 41... Steering motor 50... Steering control device 50b... Steering side control section (control section)
68...Offset compensation calculation section 71...Offset amount acquisition processing section 73...Offset amount gradual change processing section 81...Decrease gain map calculation section 82...Decrease amount map calculation section 84...Lower limit guard processing section 331...First rotation angle sensor (first 1 detection device)
332...Second rotation angle sensor (second detection device)
TK...Steering mechanism

Claims (3)

The object to be controlled is a steering device including a steering mechanism having a motor that generates a motor torque that is a power for moving a steering shaft to steer steering wheels of a vehicle,
comprising a control unit that controls a target control amount that is a target of the control amount for controlling the motor torque of the motor;
The control unit controls a first control state that controls a first target control amount obtained under a predetermined condition and a second target control amount obtained under conditions different from the first target control amount. A plurality of control states including a second control state can be switched, and after the control state is switched, the target control amount after switching to be controlled in the control state after switching is an offset compensation calculation unit that compensates to shift the control amount toward the target control amount before switching to control in the control state;
The offset compensation calculation unit includes:
an offset amount acquisition processing unit that acquires, when the control state is switched, a difference between the target control amount before and after switching as an offset amount that is an amount to be shifted through the compensation;
an offset amount gradual change processing section that changes the offset amount acquired by the offset amount acquisition processing section so that it gradually becomes smaller ;
The first target control amount is calculated under conditions using a first state variable detected by a first detection device,
The second target control amount is calculated under conditions using a second state variable detected by a second detection device,
A steering control device characterized in that the first detection device and the second detection device are redundant detection devices that respectively detect independent state variables while detecting the same detection target. The offset amount gradual change processing unit changes the amount of reduction for reducing the offset amount based on at least one of a running state of the vehicle and a steering state of the steering mechanism. Steering control device. The offset amount gradual change processing section includes a lower limit guard for reducing the offset amount by at least a minimum amount, regardless of the running state of the vehicle and the steering state of the steering mechanism, when the offset amount exists. The steering control device according to claim 2 , further comprising a processing section.