JP7348149B2 - 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 a steer-by-wire steering system, even if the steering wheel is steered while the ignition switch is off, if the steering wheel is steered while the steered wheels are not steered, the steering wheel and The positional relationship with the steering wheel deviates from the predetermined correspondence. In this case, after the ignition switch is turned from off to on, the steered wheels may be turned suddenly to the position corresponding to the steering angle, which may cause a sense of discomfort to the driver. Put it away.

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, The controller includes a control unit that controls a target control amount that is a target control amount for controlling the motor torque of the motor, and the control unit sets the target control amount to the motor when the vehicle power is switched from off to on. includes an offset compensation calculation unit that compensates to shift the motor torque generated by an offset amount acquisition processing section that acquires a control amount corresponding to the amount by which the steering wheels have to be steered 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 target control amount so that the target control amount becomes smaller.

According to the above configuration, when the target control amount that requires turning the steered wheels in the first cycle after the vehicle power is switched from off to on is calculated, the target control amount is compensated using the offset amount. Through this, the motor torque generated by the motor is shifted to the side where the motor torque generated by the motor is reduced so that the turning of the steered wheels does not occur suddenly. Thereafter, the target control amount approaches the original target control amount as the offset amount gradually decreases, and eventually comes to match the original target control amount. As a result, even if the target control amount that requires the steered wheels to be steered in the first cycle after the vehicle power is switched from off to on is calculated, the steered wheels will not be steered in the first cycle after the switch. You can prevent sudden movements. Therefore, the sense of discomfort conveyed to the driver can be suppressed.

Specifically, the above-mentioned steering control device further includes a steering shaft having a separate power transmission path from the steered wheels and rotating in conjunction with operation of a steering wheel, and the target control amount is determined by the steering shaft. A target that is calculated as a value of a steering correlation angle that has a correlation with a steering angle that is a steering angle of the steered wheels whose positional relationship with a steering angle that is a rotation angle of a shaft satisfies a predetermined correspondence relationship. The offset amount acquisition processing unit calculates a value of the steering correlation angle obtained so as to satisfy the predetermined correspondence relationship based on the steering angle in the first cycle after the vehicle power source is switched from off to on. and the value of the steering correlation angle obtained based on the actual steering angle, and a startup deviation amount is obtained as the offset amount.

For example, if the power transmission path between the steered wheels is separated and the steering shaft rotates in conjunction with the operation of the steering wheel, as in the above configuration, the steering wheel is turned off while the vehicle is powered off. If the vehicle is steered, the positional relationship between the steering angle and the turning angle will deviate from the predetermined correspondence relationship. In contrast, according to the above configuration, even if the vehicle power is switched from off to on with the positional relationship between the steering angle and the turning angle deviating from the predetermined correspondence relationship, the first It is possible to prevent the steered wheels from suddenly turning so as to be at a position corresponding to the steering angle in the cycle.

In the above steering control device, it is preferable that the predetermined correspondence is a steering angle ratio that is a ratio of the steering angle to the steering angle, and is configured to be variable based on the running state of the vehicle.

When the steering angle ratio is varied as in the above configuration, the offset amount is the shift obtained so as to satisfy a predetermined correspondence relationship based on the steering angle in the first cycle after the vehicle power is switched from off to on. It is particularly effective to obtain the amount of deviation at startup, which is the difference between the value of the rudder correlation angle and the value of the steering correlation angle obtained based on the actual steering angle.

Here, regarding the offset amount, since it forcibly shifts the original target control amount, we would like to eliminate it as soon as possible, but if the amount of decrease in the offset amount is too large, the driver of the steering mechanism It appears as a movement that does not occur.

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 a situation in which the positional relationship between the steering wheel and steered wheels deviates from a predetermined correspondence relationship, (b) is a schematic diagram illustrating how the target pinion angle changes, and (c) is an offset FIG. 2 is a schematic diagram illustrating how the amount 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, which is the steered angle of the steered wheels 16, is changed.

Further, the steering mechanism SK includes a reaction force motor 31, a deceleration mechanism 32, a rotation angle sensor 33, and a torque sensor 34 as components 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.

The rotation angle sensor 33 is provided on the reaction force motor 31. The rotation angle sensor 33 detects the rotation angle θa of the reaction force motor 31. The rotation angle θa of the reaction motor 31 is used to calculate the steering angle θs. The reaction motor 31 and the steering shaft 12 are interlocked via a speed reduction mechanism 32. For this reason, there is a correlation between the rotation angle θa of the reaction motor 31, the rotation angle of the steering shaft 12, and eventually 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 angle θa of the reaction motor 31.

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, a rotation angle sensor 33, and a rotation angle sensor 43. Vehicle speed sensor 501 detects a vehicle speed value V, which is the traveling speed of the vehicle.

Further, the steering control device 50 is connected to a vehicle power source 502 that is a vehicle startup switch such as an ignition switch. The vehicle power supply 502 detects the on/off state of the starting switch of the vehicle, and outputs a starting signal Sig when detecting the on state.

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 54. The steering side current sensor 54 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 54 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, a rotation angle θa, 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, the rotation angle θa, the steering side actual current value Ib, which will be described later, and the pinion angle θp, which will be described later. Note that the pinion angle θp is calculated based on the rotation angle θb of the steering motor 41.

The steering side control section 50a includes a steering angle calculation section 51, a steering reaction force command value calculation section 52, and an energization control section 53.
The rotation angle θa is input to the steering angle calculation unit 51. The steering angle calculation unit 51 calculates the rotation angle θa by, for example, 360° by counting the number of rotations of the reaction force motor 31 from the steering neutral position, which is the position of the steering wheel 11 when the vehicle is traveling straight. Convert to an integrated angle that includes the range exceeding. The steering angle calculation unit 51 calculates the steering angle θs by multiplying the integrated angle obtained by the conversion by a conversion coefficient based on the rotational speed ratio of the speed reduction mechanism 32. The steering angle θs is, for example, positive when the angle is to the right of the midpoint θs0, which is the steering neutral position, and negative when the angle is to the left. 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 52. The steering reaction force command value calculation unit 52 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 turning side actual current value Ib, and the pinion angle θp. Calculate the value T*. The steering reaction force command value T* thus obtained is output to the energization control section 53.

The steering reaction force command value T*, the rotation angle θa, and the steering-side actual current value Ia are input to the energization control unit 53. The energization control unit 53 calculates a current command value Ia* for the reaction force motor 31 based on the steering reaction force command value T*. Then, the energization control unit 53 calculates the deviation between the current command value Ia* 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 54 based on the rotation angle θa. is determined, and the power supply to the reaction force motor 31 is controlled so as to eliminate the deviation. 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 rotation angle θb, and the steering angle θs are input to the steered 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 rotation angle θb, the steering angle θs, and the activation signal Sig.

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. The pinion angle θp is, for example, positive when the angle is to the right of the midpoint θp0, which is the rack neutral position, and negative when the pinion angle is to the left. 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 steering angle θw of the steered wheels 16, and is an example of a steering correlation angle. The pinion angle θp obtained in this way is output to the target pinion angle calculation section 62, the pinion angle feedback control section 63, and the steering reaction force command value calculation section 52.

The vehicle speed value V, the steering angle θs, the pinion angle θp, and the activation signal Sig 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, which is a target angle of the pinion angle θp, based on the vehicle speed value V, the steering angle θs, the pinion angle θp, and the starting signal Sig. calculate.

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. Further, the post-conversion angle θvg is a value that reflects the steered angle θw of the steered wheels 16. Thereby, the steering angle ratio is an example of a predetermined correspondence relationship between the steering angle θw of the steered wheels 16 and the steering angle θs.

The offset compensation calculation unit 68 receives the vehicle speed value V, pinion angle θp, converted angle θvg, converted angular velocity ωvg, and activation signal Sig. The offset compensation calculation unit 68 calculates an offset amount θofst, which is a compensation amount when calculating the target pinion angle θp*, based on the vehicle speed value V, the converted angle θvg, the converted angular velocity ωvg, and the activation signal Sig. 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 Ib* for the steering motor 41 based on the steering force command value Tp*. Then, the energization control unit 53 converts the current command value Ib* and the current value on the dq coordinates obtained by converting the steering side actual current value Ib detected through the steering side current sensor 65 based on the rotation angle θb. The deviation 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*.

Here, in the steering device 10, the reaction force motor 31 and the steering motor 41 are not supplied with power by the respective energization control units 53 and 64 while the start switch of the vehicle is off. In other words, even if the steering wheel 11 is steered while the start switch of the vehicle is off, the steerable wheels 16 are not steered. Under these circumstances, if the steering wheel 11 is steered, the positional relationship between the steering wheel 11 and the steered wheels 16 will deviate from a predetermined correspondence based on the steering angle ratio. 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 pinion angle θp are input to the offset amount acquisition processing unit 71. The offset amount acquisition processing unit 71 subtracts the pinion angle θp from the converted angle θvg, and calculates the startup deviation amount Δθvg_p obtained through the subtractor 74. The startup deviation amount Δθvg_p obtained in this way is output to the calculated value switching unit 72.

The calculation value switching section 72 receives the starting signal Sig, the starting deviation amount Δθvg_p, 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 section 75. be done. The startup deviation amount Δθvg_p 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 the start signal Sig is input, the calculated value switching unit 72 is in a selected state so as to output the start-up deviation amount Δθvg_p input to the first input N1 as an offset basic amount θofstb that is the basic amount of the offset amount θofst. control. The selection state in which the start-up deviation amount Δθvg_p is output as the offset basic amount θofstb occurs instantaneously when the start-up signal Sig is input. When the start signal Sig is input, it is determined that the start switch of the vehicle is switched from off to on.

On the other hand, when the activation signal Sig is not input, the calculated value switching section 72 controls the selection state so as to output the offset amount θofst(-) inputted to the second input N2 as the offset basic amount θofstb. The selected state in which the offset amount θofst(-) is output as the offset basic amount θofstb is continuously maintained while the activation signal Sig is not input. While the activation signal Sig is not input, it is determined that it is not the activation time. Not during start-up refers to when the start switch of the vehicle is on or off, or when it is switched from on to off.

As for the basic offset amount θofstb selected as an appropriate value in this way, the starting deviation amount Δθvg_p calculated by the offset amount acquisition processing section 71 is output to the offset amount gradual change processing section 73 when the starting signal Sig is input. 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 while the activation signal Sig is not input.

The startup deviation amount Δθvg_p takes a value other than zero when the positional relationship between the steering wheel 11 and the steered wheels 16 deviates from a predetermined correspondence relationship based on the steering angle ratio. On the other hand, the calculated value switching unit 72 outputs the startup deviation amount Δθvg_p which is input to the first input N1 when it is determined that it is the startup time. In other words, the start-up deviation amount Δθvg_p is a control amount corresponding to the amount by which the steerable wheels 16 have to be steered in the first cycle after start-up, which is immediately after start-up. Then, the calculated value switching unit 72 determines that the positional relationship between the steering wheel 11 and the steered wheels 16 is set to a predetermined value based on the steering angle ratio due to the steering wheel 11 being steered while the start switch of the vehicle is off. It operates so that the deviation from the correspondence relationship is reflected in the basic offset amount θofstb through the startup deviation amount Δθvg_p.

On the other hand, the start-up deviation amount Δθvg_p takes a value other than zero even when it is not determined that it is the start-up time. On the other hand, the calculated value switching unit 72 does not output the startup deviation amount Δθvg_p input to the first input N1 unless it is determined that it is the startup time, so it is determined that it is the startup time. The operation is performed so that the start-up deviation amount Δθvg_p, which may occur at times other than the time, is not reflected in the offset 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 includes a map that defines the relationship between the absolute value of the converted angular velocity ωvg and the basic reduction amount θdb, which is the basic amount of the reduction amount θd, and inputs the absolute value of the converted angular velocity ωvg. Then, map calculation is performed on the basal decrease amount θdb. 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. 5A to 5C show various changes, taking as an example a case where it is determined that it is time to start up at time t1. The following description will be made on the assumption that the offset amount θofst at time "0" is a zero value and that the vehicle speed value V is constant.

FIG. 5A shows the positional relationship between the steering wheel 11 and the turning angle θw of the turning wheels 16 at time “0”. Here, when the steered angle θw of the steered wheels 16 is at the midpoint θw0 corresponding to the rack neutral position, this is caused by the steering wheel 11 being steered to the right by a predetermined angle while the vehicle starting switch is off. This shows a state in which the positional relationship between the steering wheel 11 and the steered wheels 16 deviates from a predetermined correspondence based on the steering angle ratio. In other words, a state of "θvg≠θp" is shown in which the converted angle θvg obtained based on the steering angle θs and the pinion angle θp obtained based on the pinion shaft 44 do not match.

Then, at time t1, after the start switch of the vehicle is turned on, the offset amount acquisition processing unit 71 functions, so that the difference between the converted angle θvg and the pinion angle θp is determined by the start-up deviation amount Δθvg_p. It is calculated as

In this case, as shown in FIG. 5C, the calculated value switching unit 72 functions to calculate the offset basic amount θofstb indicating the startup deviation amount Δθvg_p, 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 dashed line in FIG. 5(b), when it is determined that it is time to start, the steered wheels 16 must be steered in the first cycle after startup based on the converted angle θvg at that time. Normally, the target pinion angle θp* that should be used is calculated. On the other hand, as shown by the solid line in the figure, the target pinion angle θp* after time t1 after it is determined that it is the time of startup is determined by the compensation using the offset amount θofst. In order to avoid sudden steering operations, the motor torque generated by the steering motor 41 is shifted to the side where it becomes smaller. At the moment when it is determined that it is the time of startup, the target pinion angle θp* is compensated so that the motor torque generated by the steering motor 41 becomes zero.

Thereafter, as shown by the solid line in the same figure, the target pinion angle θp* is gradually reduced by the offset amount θofst, so that the actually calculated post-conversion angle θvg shown by the dashed line in the figure, that is, It approaches the original target pinion angle θp*. Then, the target pinion angle θp* changes to match the actually calculated converted angle θvg, that is, the original target pinion angle θp*, at the timing t2 when the offset amount θofst becomes zero value. become.

The effects of this embodiment will be explained below.
(1) In this embodiment, as shown by the solid line in FIG. 5(b), when it is determined that it is time to start, the steered wheels 16 Even if the target pinion angle θp* at which the motor should be steered is originally calculated, it is possible to suppress sudden turning of the steered wheels 16 in the first cycle after activation. Therefore, the sense of discomfort conveyed to the driver can be suppressed.

(2) In the present embodiment, the startup deviation amount Δθvg_p is acquired as the offset amount θofst. As a result, even if the positional relationship between the steering angle θs and the turning angle θw, that is, the pinion angle θp deviates from a predetermined correspondence relationship based on the steering angle ratio, the steering angle θs is adjusted in the first cycle after startup. It is possible to prevent the steered wheels 16 from suddenly turning so as to reach the corresponding position.

(3) When the steering angle ratio is variable as in this embodiment, the offset amount θofst is the starting deviation amount which is the difference between the converted angle θvg and the pinion angle θp in the first cycle after starting. Obtaining Δθvg_p is particularly effective.

(4) Here, regarding the offset amount θofst, since it forcibly shifts the actually calculated post-conversion angle θvg, that is, the original target pinion angle θp*, we would like to eliminate it as soon as possible. If the amount of decrease in the offset amount θofst is made too large, the movement of the steering mechanism TK will appear as unintended by the driver.

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.

(5) 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 offset amount θofst can be obtained from the difference between the steering angle θs and the converted pinion angle obtained by inversely converting the pinion angle θp based on the steering angle ratio, instead of obtaining it from the startup deviation amount Δθvg_p. However, it can also be obtained from the difference between the value obtained by converting the steering angle θs into the amount of movement of the steered shaft 14 and the actual amount of movement of the steered shaft 14. In addition, the offset amount θofst can also be obtained from the difference between the steering angle θs when the starting switch of the vehicle is turned off and the steering angle θs when the vehicle is started. In this case, the difference is calculated based on the steering angle ratio. What is necessary is to use the difference after conversion obtained by the conversion.

- When the target control amount to be compensated is the steering force command value Tp* or the current command value Ib*, the offset amount θofst is obtained, for example, from the deviation between the target pinion angle θp* and the pinion angle θp. You can also do that.

- 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 the steering reaction force command value T* is calculated to follow the pinion angle θp.

- Instead of controlling the pinion angle θp, the steering motor 41 may be controlled by directly detecting the amount of movement of the steering shaft 14 and based on the amount of movement. In this case, with respect to the embodiment described above, the control amount related to the pinion angle θp is replaced with the control amount related to the movement amount of the steered shaft 14.

- 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. Even in this case, the positional relationship between the steering wheel 11 and the steered wheels 16 is a predetermined correspondence based on the steering angle ratio due to the steering wheel 11 being steered while the start switch of the vehicle is off. Similar to the above embodiment, there is a state deviated from the above. 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.

- In the steering reaction force command value calculating section 52, 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.
- For example, 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.

- 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.

DESCRIPTION OF SYMBOLS 10... Steering device 11... Steering wheel 12... Steering shaft 14... Steering shaft 16... Steering wheel 41... Steering motor 50... Steering control device 50b... Steering side control part (control part)
62... Target pinion angle calculation section 67... Steering angle ratio variable calculation 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 unit 502...Vehicle power supply SK...Steering mechanism TK...Steering mechanism

Claims (5)

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 includes:
an offset compensation calculation unit that compensates for shifting the target control amount to a side where motor torque generated by the motor becomes smaller when the vehicle power source is switched from off to on;
The offset compensation calculation unit includes:
When the vehicle power source is switched from off to on, an offset is acquired as an offset amount that is an amount of shift through the compensation, which corresponds to the amount by which the steered wheels have to be steered in the first cycle after the switch. A quantity acquisition processing unit;
A steering control device comprising: an offset amount gradual change processing section that changes the target control amount so that the offset amount acquired by the offset amount acquisition processing section gradually becomes smaller. further comprising a steering shaft having a separate power transmission path from the steered wheels and rotating in conjunction with operation of the steering wheel;
The target control amount is a steering correlation that has a correlation with a steering angle that is a steering angle of the steered wheels whose positional relationship with a steering angle that is a rotation angle of the steering shaft satisfies a predetermined correspondence relationship. is the target angle calculated as an angle value,
The offset amount acquisition processing unit is configured to calculate a value of the steering correlation angle obtained so as to satisfy the predetermined correspondence relationship based on the steering angle in the first cycle after the vehicle power source is switched from off to on, and an actual value of the steering correlation angle. The steering control device according to claim 1, wherein a start-up deviation amount, which is a difference from a value of the steering correlation angle obtained based on the steering angle, is acquired as the offset amount. The steering control device according to claim 2, wherein the predetermined correspondence is a steering angle ratio that is a ratio of the steering angle to the steering angle, and is configured to be variable based on the running state of the vehicle. 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. 3. The steering control device according to any one of 3. 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 4, further comprising a processing section.