JP7147553B2 - electric power steering device - Google Patents

Description

The present invention relates to an electric power steering system.

A control method for an electric power steering device described in Patent Document 1 below is known as a technique for improving the steering feeling of a passenger. This control device detects or estimates the self-aligning torque (SAT), and responds to the steering state (further steering state, steering return state, steering holding state), vehicle speed, steering angle, steering angular velocity, and steering torque. determine the gain to be applied. Then, by multiplying the detected or estimated self-aligning torque by each of these gains, the SAT compensation value for compensating the self-aligning torque (SAT) in the electric power steering device is determined, and the actuator that drives the steering shaft is driven. The current command value to be corrected is corrected with the SAT compensation value.

Patent No. 4715446

However, with the technique described in Patent Document 1, it is difficult to obtain the SAT compensation value when the steering speed is relatively slow (for example, immediately after holding the steering wheel), and the current command value for driving the actuator that drives the steering shaft is corrected. Can not. Further, when the steering state is switched, the steering state sensitive gain is switched and the SAT compensation value becomes discontinuous. As a result, the steering feeling suddenly changes.
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is capable of correcting a current command value for driving an actuator that drives a steering shaft even when the steering speed is relatively slow, and is capable of correcting a steering current command value when the steering state is switched. An object of the present invention is to provide an electric power steering device capable of suppressing sudden changes in feeling.

To achieve the above object, an electric power steering apparatus according to one aspect of the present invention includes a steering mechanism having an actuator that drives a steering shaft, a steering torque detection unit that detects steering torque applied to the steering mechanism, and a steering mechanism. A steering position detector that detects a steering position, a current command value calculator that calculates a current command value for driving the actuator based on at least the steering torque, and a steering state of the steering mechanism that is in the additional steering state or in the reverse steering state. and a correction value calculation unit that calculates a correction value for correcting the current command value according to whether the current command value is
The correction value calculation unit includes a correction value adjustment unit that adjusts the correction value based on the amount of change in the steering position based on the steering position when the steering state is switched between the additional steering state and the return steering state.

According to the present invention, an electric power steering that can correct a current command value for driving an actuator that drives a steering shaft even when the steering speed is relatively slow, and can suppress a sudden change in steering feeling when the steering state is switched. equipment can be provided.

1 is a configuration diagram showing an outline of an example of an electric power steering device according to an embodiment; FIG. It is a block diagram showing an example of functional composition of a control unit of a 1st embodiment. It is a block diagram showing an example of functional composition of a correction value operation part of a 1st embodiment. (a) is a diagram showing an example of characteristics of a vehicle speed gain calculated by a vehicle speed steering angle gain calculator, and (b) is a diagram showing an example of characteristics of a steering angle gain. FIG. 5 is an explanatory diagram of an example of a method of determining a steering state by a steering state determination unit; FIG. 5 is a diagram showing an example of characteristics of steering torque and steering angle; (a) is a diagram showing an example of the characteristic of the steering state gain, (b) is an explanatory diagram of an example of a method of determining the steering state gain at the time of steering back, and (c) is a diagram showing an example of the steering state gain at the time of further steering. is an explanatory diagram of an example of a determination method of . It is a figure which shows the example of a change of a steering state gain. 4 is a flow chart showing an example of a control method for the electric power steering device of the embodiment; FIG. 11 is a block diagram showing an example of the functional configuration of a control unit according to the second embodiment; FIG. FIG. 5 is a diagram showing an example of vehicle speed gain characteristics for a basic damping compensation value calculation section to calculate a basic damping compensation value; FIG. 11 is a block diagram showing an example of the functional configuration of a correction value calculator according to the second embodiment; FIG. FIG. 11 is a block diagram showing an example of a functional configuration of a control unit according to a third embodiment; FIG. It is a figure which shows an example of the characteristic of the adjustment current by an adjustment current calculating part. FIG. 12 is a block diagram showing an example of a functional configuration of a correction value calculator according to the third embodiment; FIG.

Embodiments of the present invention will be described in detail with reference to the drawings.
The embodiments of the present invention shown below exemplify devices and methods for embodying the technical idea of the present invention. are not specific to the following: Various modifications can be made to the technical idea of the present invention within the technical scope defined by the claims.

(Configuration of electric power steering device)
FIG. 1 shows a configuration example of an electric power steering system according to an embodiment. A column shaft 2 of a steering handle 1 is connected to a tie rod 6 of a steering wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. As shown in FIG. A torque sensor 10 for detecting a steering torque Th of the steering wheel 1 is provided on the column shaft 2 , and a motor 20 for assisting the steering force of the steering wheel 1 is connected to the column shaft 2 via a reduction gear 3 . It is

A control unit (ECU) 30 that controls the power steering device is supplied with electric power from a battery 14 as a power supply and receives an ignition key signal from an ignition key 11 .
Based on the steering torque Th detected by the torque sensor 10 and the vehicle speed Vh detected by the vehicle speed sensor 12, the control unit 30 calculates a steering assist command value of the assist command using an assist map or the like. The current I supplied to the motor 20 is controlled based on the steering assist command value.

In the electric power steering apparatus having such a configuration, the torque sensor 10 detects the steering torque Th generated by the driver's steering wheel operation transmitted from the steering wheel 1, and the steering torque Th is calculated based on the detected steering torque Th and the vehicle speed Vh. The motor 20 is driven and controlled by the steering assist command value, and this drive is applied to the steering system as an assisting force (steering assisting force) for the driver's steering operation, so that the driver can operate the steering wheel with a light force. In other words, the steering assist command value is calculated from the steering torque Th and the vehicle speed Vh output by the steering wheel operation. , the performance of the electric power steering system is greatly affected.

Control unit 30 may comprise, for example, a computer including a processor and peripheral components such as storage devices. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).
The storage device may comprise any one of a semiconductor storage device, a magnetic storage device and an optical storage device. The storage device may include memories such as registers, cache memories, ROMs (Read Only Memories) used as main storages, and RAMs (Random Access Memories).
The functions of the control unit to be described below are realized, for example, by the processor of the control unit 30 executing a computer program stored in the storage device.

Note that the control unit 30 may be formed of dedicated hardware for executing each information processing described below.
For example, control unit 30 may comprise functional logic circuitry implemented in a general-purpose semiconductor integrated circuit. For example, the control unit 30 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

(First embodiment)
(Constitution)
An example of the functional configuration of the control unit 30 of the first embodiment will be described with reference to FIG. The control unit 30 includes a basic current command value calculation unit 40, a self-aligning torque (SAT) detection unit 41, a correction value calculation unit 42, an adder 43, a subtractor 44, and a proportional integral (PI). Integral) controller 45 , PWM (Pulse Width Modulation) controller 46 , and inverter (INV) 47 .

The steering torque Th detected and input by the torque sensor 10 and the vehicle speed Vh from the vehicle speed sensor 12 are input to the basic current command value calculator 40 . The basic current command value calculation unit 40 determines a basic current command value Iref1, which is a current control target value for driving the motor 20, based on the input steering torque Th and vehicle speed Vh. Basic current command value Iref1 is input to adder 43 .

The SAT detector 41 detects or estimates the self-aligning torque SAT acting on the vehicle. For example, the SAT detector 41 may estimate the self-aligning torque by the method disclosed in Japanese Patent Laid-Open No. 2002-369565.
That is, in the steering system of a vehicle, a steering torque Th is generated by a driver steering a steering wheel, and a motor generates an assist torque Tm according to the steering torque Th. SAT occurs.

At this time, the inertia J and friction (static friction) Fr of the motor and mechanism generate a torque that acts as a resistance to steering the steering wheel.
J·dωm/dt+Fr·sign(ωm)+SAT=Tm+Th (1)

Here, the above equation (1) is Laplace-transformed with an initial value of zero, and the SAT is solved to obtain the following equation (2).
SAT(s)=Tm(s)+Th(s)-J*s*ωm(s)−Fr*sign(ωm(s)) (2)
As can be seen from the above equation (2), by obtaining the inertia J and static friction Fr of the motor and the mechanism as constants in advance, the column axis converted rotational angular velocity ωm of the motor, the rotational angular acceleration dωm/dt, and the steering assist force And the self-aligning torque SAT can be estimated from the steering signal.

The correction value calculator 42 acquires the steering angle (that is, the steering position) θ from a rotation angle sensor such as a resolver 48 connected to the motor 20 . Alternatively, a steering angle sensor for detecting the steering angle θ of the steering wheel 1 may be provided on the column shaft 2 .
A correction value calculation unit 42 calculates a SAT compensation value Cs for compensating the self-aligning torque in the electric power steering device based on the steering angle θ, the steering torque Th, the vehicle speed Vh, and the self-aligning torque SAT. The correction value calculator 42 inputs the SAT compensation value Cs to the adder 43 .

The adder 43 calculates the current command value Iref by adding the SAT compensation value Cs to the basic current command value Iref1.
The current command value Iref is input to the subtractor 44, and the deviation (Iref-Im) from the motor current value Im being fed back is calculated. It is input to the part 45 .

The steering assist command value Vref whose characteristics are improved by the PI control unit 45 is input to the PWM control unit 46, and the motor 20 is PWM-driven via the inverter 47 as a driving unit. A current value Im of the motor 20 is detected by a motor current detector 49 and fed back to the subtractor 44 . The inverter 47 uses an FET (Field Effect Transistor) as a driving element and is configured by an FET bridge circuit.

Next, the correction value calculator 42 will be described with reference to FIG. The correction value calculation unit 42 sets the above SAT compensation value Cs as a correction value for correcting the current command value for driving the motor 20 depending on whether the steering state of the steering mechanism is the additional steering state or the reverse steering state. to calculate.
The correction value calculator 42 includes a vehicle speed steering angle gain calculator 50 , a multiplier 51 , a steering state gain calculator 52 and a multiplier 53 .

A vehicle speed steering angle gain calculator 50 calculates a vehicle speed steering angle gain Gva that changes in response to the vehicle speed Vh and the steering angle θ. For example, the vehicle speed steering angle gain calculator 50 calculates the product of the vehicle speed sensitive gain Gv and the steering angle sensitive gain Ga as shown in FIGS. It may be calculated as Ga. A multiplier 51 calculates the product Gva×SAT of the vehicle speed steering angle gain Gva and the self-aligning torque SAT.

A steering state gain calculator 52 calculates a steering state gain Gs that changes in response to the steering state of the steering mechanism. The steering state gain calculation section 52 includes a steering state determination section 54 , a steering angle change amount calculation section 55 and a gain calculation section 56 .
The steering state determination unit 54 determines whether the steering state of the steering mechanism is in the additional steering state or in the reverse steering state. Hereinafter, "determining whether the steering state is the additional steering state or the steering back state" may be simply expressed as "determining the steering state".

The steering angle θ and the steering torque Th are input to the steering state determination unit 54 for determining the steering state. A steering state determination unit 54 determines the steering direction based on the change in the steering angle θ. The steering state determination unit 54 determines the steering state based on the sign of the steering angle (steering position) θ, the sign of the steering direction, and the sign of the steering torque Th.

In this example, the sign of the steering angle θ displaced clockwise from the neutral position of the steering mechanism is defined as "positive", and the sign of the steering angle θ displaced counterclockwise from the neutral position is defined as "negative". The sign of the clockwise steering direction and the sign of the steering torque Th are defined as "positive", and the sign of the counterclockwise steering direction and the steering torque Th are defined as "negative".
The steering state determination unit 54 determines the steering state of the steering mechanism according to the table shown in FIG. 5, for example.

The steering state determination unit 54 determines that "state 1" in which the sign of the steering angle θ, the sign of the steering direction, and the sign of the steering torque Th are all "negative" is the "state of further turning counterclockwise". judge.
The "state 2" in which the sign of the steering angle θ and the sign of the steering direction are "negative" and the sign of the steering torque Th is "positive" is determined to be the "state of further steering counterclockwise".
"State 3" in which the sign of the steering angle θ and the sign of the steering torque Th are "negative" and the sign of the steering direction is "positive" is determined to be the "state of turning back clockwise".
The "state 4" in which the sign of the steering angle θ is "negative" and the signs of the steering direction and the steering torque Th are "positive" is determined to be the "state of further turning clockwise".

Further, "state 5" in which the sign of the steering angle θ is "positive" and the signs of the steering direction and the steering torque Th are "negative" is determined to be the "counterclockwise additional steering state".
The sign of the steering angle θ and the sign of the steering torque Th are positive, and the sign of the steering direction is negative.
"State 7" in which the sign of the steering angle θ and the sign of the steering direction are "positive" and the sign of the steering torque Th is "negative" is determined to be the "state of further turning clockwise".
"State 8" in which the sign of the steering angle .theta., the sign of the steering direction, and the sign of the steering torque Th are all "positive" is determined to be the "state of further turning clockwise."

In this manner, the steering state determination unit 54 determines that the steering state is in the additional steering state when the sign of the steering angle θ is equal to the sign of the steering direction or when the sign of the steering angle θ and the sign of the steering torque Th are different. I judge. Further, when the sign of the steering angle θ and the sign of the steering torque Th are the same and the sign of the steering angle θ and the sign of the steering direction are different (that is, the sign of the steering torque Th and the sign of the steering direction are also different), the steering state is in the switchback state.

Referring to FIG. 6, the ranges of states 1 to 8 will be described with reference to a characteristic diagram of steering angle θ and steering torque Th.
In the state where the vehicle is steered in the direction of the arrow 70 within the range of the solid line 60, the sign of the steering angle θ, the sign of the steering direction, and the sign of the steering torque Th are all "negative". Therefore, such a state becomes "state 1" (counterclockwise rounding state).

Next, in the state of steering in the direction of the arrow 71 within the range of the dashed line 61, the sign of the steering angle θ is "negative" and the sign of the steering direction is "positive". Also, since the driver returns the steering wheel 1 to the neutral position against the self-aligning torque, the sign of the steering torque Th becomes "negative". Therefore, such a state becomes "state 3" (clockwise switchback state).
As shown in State 1 and State 3, the trajectories of the characteristic line in the additional steering state and the characteristic line in the reverse steering state do not match, and the steering angle θ and the steering torque Th have hysteresis characteristics.

This is because there is a difference (hysteresis width Wh) in the steering torque required for steering between the additional steering in which the direction of the self-aligning torque is steered and the reverse steering in which the steering is steered in the same direction as the direction of the self-aligning torque. This is because
Further, when the vehicle is steered in the direction of the arrow 72 within the range of the dashed line 62, the sign of the steering angle θ is "negative" and the sign of the steering direction and the steering torque Th are "positive". Therefore, such a state becomes "state 4" (clockwise rounding state).

When the vehicle is steered in the direction of the arrow 73 within the range of the solid line 63, the sign of the steering angle θ, the sign of the steering direction, and the sign of the steering torque Th are all "positive". Therefore, such a state becomes "state 8" (clockwise rounding state).
In the state of steering in the direction of the arrow 74 within the range of the dashed line 64, the sign of the steering angle θ and the sign of the steering torque Th are "positive", and the sign of the steering direction is "negative". Therefore, such a state becomes "state 6" (counterclockwise switch-back state).

In the state of steering in the direction of the arrow 75 within the range of the dashed line 65, the sign of the steering angle θ is "positive" and the sign of the steering direction and the sign of the steering torque Th are "negative". Therefore, such a state is determined to be "state 5" (counterclockwise rounding state).
Further, the additional steering (arrow 78) in the middle of the return in state 3 (returned clockwise) is also changed to state 1 (returned counterclockwise). The additional steering state (arrow 79) during the return of the steering in state 6 (counterclockwise steering return state) also changes to state 8 (clockwise additional steering state).

Furthermore, in a state where the steering direction changes in the middle of "state 4" before the sign of the steering angle θ changes from "negative" to "positive" as indicated by arrow 76, the sign of the steering angle θ and the steering direction is "negative" and the sign of the steering torque Th is "positive". Therefore, such a state becomes "state 2" (counterclockwise rounding state).
Similarly, in a state where the steering direction changes in the middle of "state 5" before the sign of the steering angle θ changes from "positive" to "negative" as indicated by an arrow 77, the sign of the steering angle θ and the steering The sign of the direction is "positive" and the sign of the steering torque Th is "negative". Therefore, such a state becomes "state 7" (clockwise rounding state).
By detecting state 2 and state 7 in this way, it is possible to determine more quickly whether the driver is steering further.

Please refer to FIG. The steering state determination unit 54 outputs the steering state determination result to the steering angle change amount calculation unit 55 and the gain calculation unit 56 .
The steering angle change amount calculation unit 55 determines whether or not the steering state of the steering mechanism has switched between the additional steering state and the steering back state based on the determination result of the steering state determination unit 54 . Hereinafter, "switching of the steering state between the additional steering state and the return state" may be simply referred to as "switching of the steering state".

A steering angle change amount calculation unit 55 calculates a steering angle change amount Δθ based on the steering angle θ at the time when the steering state is switched. For example, the steering angle change amount calculator 55 resets the value of the steering angle change amount Δθ to 0 when the steering state is switched, and calculates the steering angle change amount Δθ by integrating the subsequent change amounts of the steering angle θ. may be updated. The steering angle change amount calculator 55 outputs the steering angle change amount Δθ to the gain calculator 56 .

A gain calculation unit 56 calculates a steering state gain Gs corresponding to the steering angle change amount Δθ. The gain calculator 56 may calculate the steering state gain Gs according to the steering angle change amount Δθ, for example, according to the characteristic diagram shown in FIG. 7(a).
A solid line C1 in FIG. 7(a) is a characteristic line of the steering state gain Gs when the steering angle change amount Δθ that changes the steering state gain Gs from the lower limit value G1 to the upper limit value G2 occurs due to the return steering. A dashed-dotted line C2 is a characteristic line of the steering state gain Gs when the steering angle change amount Δθ that changes the steering state gain Gs from the upper limit value G2 to the lower limit value G1 occurs due to additional steering.

As shown in (a) of FIG. 7, the characteristic line C1 during the return steering monotonously increases as the steering angle change amount Δθ increases, and the characteristic line C2 during the additional steering increases in the steering angle change amount Δθ. decreases monotonically with respect to These characteristic lines C1 and C2 may change nonlinearly or linearly with respect to the change in the steering angle change amount Δθ. For example, as shown in FIG. 7A, the change rate of the steering state gain Gs with respect to the steering angle change amount .DELTA..theta. may be decreased as the steering angle change amount .DELTA..theta.

When the steering state is switched, the gain calculator 56 may change the steering state gain Gs so that the steering state gain Gs is continuous before and after the steering state is switched.
An example of a method for changing the steering state gain Gs by the gain calculator 56 will be described with reference to FIGS. 7(b) and 7(c).
When the steering state is switched, for example, the gain calculator 56 temporarily holds the steering state gain Gss at the time of the switching.

When switching from additional steering to steering back steering occurs, the gain calculation unit 56 temporarily holds the value (Gss1) at the time of switching as the steering state gain Gss, as shown in FIG. 7B. , the steering angle change amount corresponding to the steering state gain Gss (=Gss1) on the characteristic line C1 is stored as the offset Δθoff. Note that the offset Δθoff is 0 when the value of the steering state gain Gss is the lower limit value G1.
After the steering state is switched, the gain calculation unit 56 calculates a value (Δθ+Δθoff) by adding the offset Δθoff to the steering angle change amount Δθ calculated by the steering angle change amount calculation unit 55. The corresponding gain G3 is assumed to be the steering state gain Gs.

On the other hand, when switching from steering back to steering to further steering occurs, the value (Gss2) at the time of occurrence of the switching is temporarily held as the steering state gain Gss, and the characteristic line as shown in (c) of FIG. On C2, the steering angle change amount corresponding to the steering state gain Gss (=Gss2) is stored as the offset Δθoff. Note that the offset Δθoff is 0 when the value of the steering state gain Gss is the upper limit value G2.
After the steering state is switched, the gain calculation unit 56 calculates a value (Δθ+Δθoff) by adding the offset Δθoff to the steering angle change amount Δθ calculated by the steering angle change amount calculation unit 55. The corresponding gain G4 is assumed to be the steering state gain Gs.

In this way, when the steering state is switched, the gain calculation unit 56 increases or decreases the steering state gain Gss at the time of the switching by a change amount according to the steering angle change amount Δθ from the time of the switching. Change the steering state gain Gs. Thereby, the gain calculation unit 56 can change the steering state gain Gs so that the steering state gain Gs is continuous before and after the steering state is switched.

Please refer to FIG. The gain calculator 56 inputs the steering state gain Gs to the multiplier 53 .
A multiplier 53 multiplies the product Gva*SAT of the vehicle speed steering angle gain Gva and the self-aligning torque SAT calculated by the multiplier 51 by the steering state gain Gs to calculate the SAT compensation value Cs.
As described above, the SAT compensation value Cs is input to the adder 43, and the adder 43 adds the SAT compensation value Cs to the basic current command value Iref1 to calculate the current command value Iref.
In this way, the steering state gain calculation unit 52 and the multiplier 53 calculate the current command based on the steering angle change amount (steering position change amount) Δθ based on the steering angle (steering position) at the time when the steering state is switched. It has a function as a correction value adjuster that adjusts the SAT compensation value Cs, which is a correction value for correcting the value.

(action)
Next, an example of a change in the steering state gain Gs due to the return steering and the additional steering will be described. Please refer to FIG. When the additional steering is started at time t1, the steering state gain Gs starts decreasing from the upper limit value G2 and reaches the lower limit value G1 at time t2. If the additional steering is continued until time t3, the absolute value of the steering angle θ increases, but the steering state gain Gs maintains the lower limit value G1.

When the return steering is started at time t3, the steering state gain Gs starts increasing from the lower limit value G1 and reaches the upper limit value G2 at time t4. If the return steering is continued until time t5, the absolute value of the steering angle θ decreases, but the steering state gain Gs maintains the upper limit value G2.
When the sign of the steering torque changes from positive to negative at time t5, the steering state changes from the return steering to the further steering. When the state changes to additional steering, the steering state gain Gs starts decreasing from the upper limit value G2 and reaches the lower limit value G1 at time t6. If the additional steering is continued until time t7, the steering state gain Gs maintains the lower limit value G1.

When the return steering is started at time t7, the steering state gain Gs starts increasing from the lower limit value G1. At time t8, additional steering starts before the steering state gain Gs reaches the upper limit value G2. That is, the steering state is switched from the return steering to the additional steering.
As described above, the gain calculator 56 changes the steering state gain Gs so that the steering state gain Gs continues before and after the steering state is switched, so the steering state gain Gs starts decreasing from the value at time t8. .

After that, it reaches the lower limit value G1 at time t9. Thereafter, further steering is continued, and at time t10, steering back is started, and the steering starts to increase from the lower limit value G1 and reaches the upper limit value G2 at time t11.
Thus, according to the present embodiment, the SAT compensation value Cs for correcting the basic current command value Iref1 can be obtained from the steering state gain Gs that continuously changes with respect to the steering operation. Therefore, it is possible to suppress a sudden change in the steering feeling when the steering state is switched.
Both the upper limit value G2 and the lower limit value G1 may be positive values or negative values. Furthermore, the upper limit value G2 and the lower limit value G1 may be a combination of a positive value and zero (0), or a combination of a positive value and a negative value.
In addition, in FIGS. 7A to 7C and 8, the steering state gain Gs is a monotonically increasing function of the steering angle change amount Δθ during the return steering, and Although an example of a monotonically decreasing function has been shown, the steering state gain Gs is a monotonically decreasing function of the steering angle change amount Δθ during the return steering, and is a monotonically decreasing function during the additional steering. It may be an increasing function. In other words, the property of the correction value input to the correction value calculation unit 42 and the correction direction of the assist force may be taken into account to appropriately set.

(motion)
Next, an example of a control method for the electric power steering system according to the embodiment will be described with reference to FIG.
At step S1, the torque sensor 10 detects the steering torque Th.
In step S2, a steering angle (steering position) θ is detected using a rotation angle sensor such as the resolver 48 or a steering angle sensor.

In step S<b>3 , the basic current command value calculation section 40 calculates a basic current command value Iref<b>1 for driving the motor 20 .
In step S4, the steering state determining section 54 determines the steering state of the steering mechanism.
In step S5, the steering angle change amount calculator 55 and the gain calculator 56 determine whether or not the steering state has been switched. If the steering state is switched (step S5: Y), the process proceeds to step S6. If the steering state is not switched (step S5: N), the process proceeds to step S7.

In step S6, the steering angle change amount calculator 55 reduces the steering angle change amount Δθ that has been calculated to 0 in order to calculate the steering angle change amount Δθ based on the steering angle θ at the time when the steering state is switched. reset to
Further, the gain calculation unit 56 stores the steering angle change amount corresponding to the steering state gain Gss at the time of occurrence of switching as the offset Δθoff. After that, the process proceeds to step S8.

In step S7, the steering angle change amount calculator 55 updates the steering angle change amount Δθ by adding the change amount of the steering angle θ that occurred after the steering angle change amount Δθ was last updated to the steering angle change amount Δθ. After that, the process proceeds to step S8.
In step S8, the gain calculator 56 and the multiplier 53 adjust the correction amount for correcting the current command value based on the steering angle change amount Δθ. In the example of the first embodiment, the SAT compensation value Cs is adjusted as the correction amount.

Specifically, the gain calculation unit 56 calculates a steering state gain Gs corresponding to the steering angle change amount Δθ based on the steering angle change amount Δθ and the offset Δθoff. A multiplier 53 multiplies the product Gva*SAT of the vehicle speed steering angle gain Gva and the self-aligning torque SAT by the steering state gain Gs to calculate the SAT compensation value Cs.

In step S9, the adder 43 corrects the current command value based on the correction value adjusted in step S8. In the example of the first embodiment, the SAT compensation value Cs is added to the basic current command value Iref1 calculated by the basic current command value calculator 40 to calculate the current command value Iref.
At step S10, the subtractor 44, the PI controller 45, the PWM controller 46, and the inverter 47 control the motor 20 based on the current command value Iref.

(Effect of the first embodiment)
(1) The torque sensor 10 detects steering torque Th applied to the steering mechanism. The steering angle θ of the steering mechanism is detected using the motor rotation angle from the resolver 48 or the signal from the steering angle sensor. A basic current command value calculation unit 40 calculates a basic current command value Iref1 for driving an actuator that drives the column shaft 2, which is a steering shaft, based on at least the steering torque Th. A correction value calculation unit 42 calculates a correction value for correcting the basic current command value Iref1 depending on whether the steering state of the steering mechanism is the additional steering state or the reverse steering state. The steering state gain calculation unit 52 and the multiplier 53 adjust the correction value based on the steering angle change amount Δθ based on the steering position at the time when the steering state switches between the additional steering state and the steering back state.

In this manner, the steering state is determined without using the steering speed, and the correction value is adjusted according to the steering angle change amount Δθ from the occurrence of the steering state switching. The driving current command value can be corrected.
Further, by adjusting the correction value according to the steering angle change amount Δθ from the time the steering state is switched, the current command value can be continuously corrected, and the hysteresis width of the steering torque Th at the time of switching the steering state The steering feeling can be changed by adjusting Wh.

(2) When the sign of the steering position is equal to the sign of the steering direction, or when the sign of the steering position and the sign of the steering torque are different, the correction value calculation unit 42 determines that the steering state is in the additional steering state, When the sign of the steering position and the sign of the steering torque are the same and the sign of the steering position and the sign of the steering direction are different, it is determined that the steering state is the return state. Here, it is defined that the sign of the steering position displaced clockwise from the neutral position of the steering mechanism, the sign of the clockwise steering torque, and the sign of the clockwise steering direction are the same. The sign of the steering position displaced counterclockwise from the neutral position, the sign of the steering torque in the counterclockwise direction, and the sign of the steering direction in the counterclockwise direction are defined to be equal. This makes it possible to accurately determine the steering state of the driver.

(3) The SAT detector 41 detects self-aligning torque. A correction value calculation unit 42 calculates a SAT compensation value Cs based on the self-aligning torque SAT as a correction value for correcting the basic current command value Iref1.
The steering state gain calculator 52 calculates different steering state gains Gs according to the steering angle change amount Δθ. A multiplier 53 adjusts the SAT compensation value Cs with the steering state gain Gs.
Thereby, it is possible to design the SAT compensation value Cs that continuously changes with respect to the steering angle change amount Δθ and has a high degree of freedom.

(4) The steering state gain calculator 52 changes the steering state gain Gs so as to be continuous before and after the steering state is switched between the additional steering state and the return steering state. As a result, the steering state gain Gs changes continuously with the switching of the steering state, so that the sudden change in the current command value can be reduced and the sudden change in the steering feeling can be suppressed.

(Second embodiment)
Next, a second embodiment will be described. The control unit 30 of the second embodiment uses, as a correction value for correcting the current command value for driving the motor 20, a damping compensation value that gives the steering mechanism a damping characteristic corresponding to the steering speed.
Please refer to FIG. The functional configuration of the control unit 30 of the second embodiment has the same functional configuration as that of the first embodiment shown in FIG. 2, and the same reference numerals indicate the same components.

The control unit 30 of the second embodiment includes at least a basic damping compensation value calculator 80 that calculates a basic damping compensation value Cd1 corresponding to the steering speed of the steering mechanism. The angular velocity converter 81 inputs the steering angular velocity obtained by differentiating the steering angle θ to the basic damping compensation value calculator 80 as the steering velocity ω.
A basic damping compensation value calculator 80 calculates a basic damping compensation value Cd1 corresponding to the vehicle speed Vh and the steering speed ω.
For example, the basic damping compensation value calculator 80 may calculate the basic damping compensation value Cd1=Gv×(-ω) by multiplying the vehicle speed sensitive gain Gv shown in FIG. 11 by the inverse value of the steering speed ω.

Please refer to FIG. The basic damping compensation value calculator 80 inputs the calculated basic damping compensation value Cd1 to the correction value calculator 42 . The correction value calculator 42 calculates the damping compensation value Cd by correcting the basic damping compensation value Cd1 based on the steering angle θ and the steering torque Th. The adder 43 calculates the current command value Iref by adding the damping compensation value Cd to the basic current command value Iref1.

Please refer to FIG. The correction value calculator 42 calculates the damping compensation value Cd by multiplying the basic damping compensation value Cd1 by the steering state gain Gs calculated by the steering state gain calculator 52 in the multiplier 53 . The configuration and function of the steering state gain calculator 52 are the same as in the case of the first embodiment.
Thus, even if the basic current command value Iref1 is corrected with the damping compensation value Cd adjusted by the steering state gain Gs to calculate the current command value Iref, the same effect as in the first embodiment is obtained.

(Effect of Second Embodiment)
A basic damping compensation value calculator 80 calculates a basic damping compensation value Cd1 corresponding to the steering speed ω of the steering mechanism. The steering state gain calculator 52 calculates different steering state gains Gs according to the steering angle change amount Δθ. The multiplier 53 calculates a damping compensation value Cd obtained by multiplying the basic damping compensation value Cd1 by the steering state gain Gs as a correction value for correcting the current command value for driving the motor 20 .
As a result, the damping compensation value Cd that continuously changes with respect to the steering angle change amount Δθ and has a high degree of freedom can be designed.

(Third embodiment)
Next, a third embodiment will be described. The control unit 30 of the third embodiment uses an adjustment current for adjusting the current command value according to the steering torque Th as a correction value for correcting the current command value for driving the motor 20 .
Please refer to FIG. The functional configuration of the control unit 30 of the third embodiment has the same functional configuration as that of the first embodiment shown in FIG. 2, and the same reference numerals indicate the same components.

The control unit 30 of the third embodiment includes an adjustment current calculator 82 that calculates the basic adjustment current Ia1 corresponding to the steering torque Th.
For example, the adjustment current calculator 82 may calculate a basic adjustment current Ia1 that changes in response to the steering torque Th as shown in FIG.
Please refer to FIG. The adjustment current calculator 82 inputs the calculated basic adjustment current Ia1 to the correction value calculator 42 . The correction value calculator 42 calculates the adjustment current Ia by correcting the basic adjustment current Ia1 based on the steering angle θ and the steering torque Th. The adder 43 calculates the current command value Iref by adding the adjustment current Ia to the basic current command value Iref1.

Please refer to FIG. The correction value calculation unit 42 multiplies the basic adjustment current Ia1 by the steering state gain Gs calculated by the steering state gain calculation unit 52 in the multiplier 53 to calculate the adjustment current Ia. The configuration and function of the steering state gain calculator 52 are the same as in the case of the first embodiment.
Thus, even if the current command value Iref is calculated by correcting the basic current command value Iref1 with the adjusted current Ia adjusted by the steering state gain Gs, the same effect as in the first embodiment is obtained.
Further, even if the correction value calculation unit 42 outputs the steering state gain Gs as the adjustment current Ia to the adder 43 and corrects the basic current command value Iref1 with the steering state gain Gs to calculate the current command value Iref, It has the same effect as the first embodiment.

(Effect of the third embodiment)
(1) The adjustment current calculator 82 calculates a basic adjustment current Ia1 for adjusting the current command value Iref according to the steering torque Th. The steering state gain calculator 52 calculates different steering state gains Gs according to the steering angle change amount Δθ. Multiplier 53 calculates adjustment current Ia obtained by multiplying basic adjustment current Ia1 by steering state gain Gs as a correction value for correcting a current command value for driving motor 20 .
Alternatively, the correction value calculator 42 calculates the steering state gain Gs as the adjustment current Ia for adjusting the current command value Iref. The steering state gain calculator 52 changes the steering state gain Gs according to the steering angle change amount Δθ.
As a result, it is possible to design the adjustment current Ia that continuously changes with respect to the steering angle change amount Δθ and has a high degree of freedom.

(Modification)
So far, the embodiment in which the present invention is applied to the electric power steering system has been described. However, the present invention is not limited to the electric power steering device, and can be applied to, for example, a steer-by-wire steering control device in which the steering wheel 1 and the steered wheels are mechanically separated.
A current command value for driving an actuator that applies a steering reaction force to the steering wheel 1 is calculated based on the steering torque detected by the reaction force sensor. In this case, for example, the correction value calculation section 42 may calculate a correction value for correcting the current command value for driving the actuator that applies the steering reaction force to the steering wheel 1 .

Reference Signs List 1 Steering handle 2 Column shaft 3 Reduction gear 4A, 4B Universal joint 5 Pinion rack mechanism 6 Tie rod 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 14 Battery 20 Motor 30 Control unit 40 Basic current command value calculator 41 Self-aligning torque detector 42 Correction value calculator 43 Adder 44 Subtractor 45 Proportional integral Control part 46... PWM control part 47... Inverter 48... Resolver 49... Motor current detector 50... Vehicle speed steering angle gain calculation part 51, 53... Multiplier 52... Steering state gain calculation part 54... Steering state determination unit 55 Steering angle change amount calculation unit 56 Gain calculation unit 80 Basic damping compensation value calculation unit 81 Angular velocity conversion unit 82 Adjustment current calculation unit

Claims (8)

a steering mechanism having an actuator that drives a steering shaft;
a steering torque detection unit that detects a steering torque applied to the steering mechanism;
a steering position detection unit that detects a steering position of the steering mechanism;
a current command value calculation unit that calculates a current command value for driving the actuator based on at least the steering torque;
a correction value calculation unit that calculates a correction value for correcting the current command value according to whether the steering state of the steering mechanism is an additional steering state or a steering back state;
The correction value calculation unit adjusts the correction value based on the amount of change in the steering position based on the steering position at the time when the steering state is switched between the additional steering state and the return steering state. An electric power steering device comprising an adjustment section. The correction value calculation unit determines that the steering state is an additional steering state when the sign of the steering position is equal to the sign of the steering direction or when the sign of the steering position and the sign of the steering torque are different. determining that the steering state is the steering-back state when the sign of the steering position and the sign of the steering torque are equal and the sign of the steering position and the sign of the steering direction are different;
The sign of the steering position displaced in the clockwise direction from the neutral position of the steering mechanism, the sign of the steering torque in the clockwise direction, and the sign of the steering direction in the clockwise direction are equal, and counterclockwise from the neutral position. the sign of the steering position displaced in the turning direction, the sign of the steering torque in the counterclockwise direction, and the sign of the steering direction in the counterclockwise direction are equal;
The electric power steering system according to claim 1, characterized in that: Equipped with a self-aligning torque detector that detects self-aligning torque,
The correction value calculation unit calculates a self-aligning torque compensation value based on the self-aligning torque as the correction value,
The correction value adjustment unit calculates a different gain according to the amount of change in the steering position, and multiplies the gain to adjust the self-aligning torque compensation value.
The electric power steering system according to claim 1 or 2, characterized in that: a damping compensation value calculation unit that calculates a basic damping compensation value corresponding to the steering speed of the steering mechanism;
The correction value adjustment unit calculates different gains according to the amount of change in the steering position,
The correction value calculation unit calculates the correction value by multiplying the basic damping compensation value by the gain.
The electric power steering system according to claim 1 or 2, characterized in that: an adjustment current calculation unit that calculates an adjustment current for adjusting the current command value according to the steering torque;
The correction value adjustment unit calculates different gains according to the amount of change in the steering position,
The correction value calculation unit multiplies the adjustment current by the gain to calculate the correction value.
The electric power steering system according to claim 1 or 2, characterized in that: 6. The correction value adjustment unit changes the gain so as to be continuous before and after the steering state is switched between the additional steering state and the steering back state. The electric power steering device described in . The correction value calculation unit calculates an adjustment current for adjusting the current command value as the correction value,
The correction value adjustment unit changes the correction value according to the amount of change in the steering position.
The electric power steering system according to claim 1 or 2, characterized in that: 8. The electric power steering according to claim 7, wherein the correction value adjusting unit changes the correction value so as to be continuous before and after the steering state is switched between the additional steering state and the steering back state. Device.

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