JP3803226B2 - Electric power steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an electric power steering apparatus using an electric motor as a drive source.
[0002]
[Prior art]
Conventionally, an electric power steering device that assists steering by transmitting torque (steering assisting force) generated by an electric motor to a steering mechanism of a vehicle has been used. The electric motor is controlled by an electronic control unit (ECU) for the electric power steering device based on the steering torque applied to the steering wheel, the vehicle speed, and the like. Specifically, the torque signal output from the torque sensor that detects the steering torque and the vehicle speed signal output from the vehicle speed sensor that detects the vehicle speed are input to the electronic control unit. A current command value is calculated based on a signal input from each sensor, and the electric motor is feedback-controlled based on the current command value.
[0003]
[Problems to be solved by the invention]
However, when external noise is mixed into the torque signal and the like and is input to the electronic control unit, the current command value is erroneously calculated based on the torque signal mixed with the noise signal. There was a case where slight vibration occurred and the steering feeling deteriorated. This slight vibration of the steering wheel is particularly noticeable when the steering wheel is being held.
[0004]
Therefore, in order to prevent a slight vibration of the steering wheel in the steered state, it is determined whether the steering wheel is in the steered state or the steered state. It is conceivable to set the current command value low. Whether the steering wheel is in the steering-holding state or the steering state can be determined by detecting the rotational speed of the electric motor. That is, if the rotation speed of the electric motor is equal to or lower than a predetermined speed, it can be determined that the steering state is maintained, and if it is higher than the predetermined speed, it can be determined that the steering state is established.
[0005]
However, if the steering state is determined based on only the rotation speed of the electric motor, the steering wheel is maintained in the neutral position (the position of the steering wheel when the vehicle is traveling straight). When the motor is cut from one side to the other, the rise of the rotational speed of the electric motor is slow, so that there is a delay in detecting that the steering state has been switched to the steering state, which may cause a delay in the steering assist. .
[0006]
The present invention has been made under the background as described above, and an object of the present invention is to improve the steering feeling in a state in which a steering means such as a steering wheel is held, and at the start of steering. It is an object of the present invention to provide an electric power steering control device that can improve the response of steering assistance.
[0008]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, an invention according to claim 1 is directed to an electric power for controlling an electric motor (M) that applies a steering assist force to a steering mechanism (3) of a vehicle based on steering of a steering means (1). A steering control device, motor rotational acceleration detecting means (8, 66, E2, Q1) for detecting a motor rotational acceleration which is a time change amount of the rotational speed (R) of the electric motor, and the motor rotational acceleration detecting means State discriminating means (66, E2, Q1) for discriminating whether the steering means is in the steering holding state or the steering state based on the motor rotational acceleration (dR / ds) detected by the motor, and this state discriminating means An electric power steering control device including control gain setting means (67, 68) for setting a control gain of the electric motor based on the determination result of
[0009]
In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. Hereinafter, this is the same in this section.
According to the present invention, it is determined whether the steering means is in the steering holding state or the steering state, and the control gain is set based on the determination result.
For example, as described in claim 4, when the control gain setting means determines that the steering means is in the holding state by the state determination means, the control gain of the electric motor is set to a first value. When the steering means is set to be gradually reduced to a constant value (Kph, Kih) and it is determined that the steering means is in a steering state, the control gain of the electric motor is set to a second constant larger than the first constant value. If the value is set so as to gradually increase to the value (Kps, Kis), the amount of current flowing through the electric motor in the steered state can be suppressed, so that undesired vibration due to noise or the like can be prevented. Therefore, the steering feeling in the steered state can be improved.
[0010]
Further, when the configuration of claim 4 is adopted, the control gain is set to gradually decrease or increase, so that the steering assist force suddenly decreases or increases when the steering means is held or started to steer. the can be prevented, Ru can be further improved feeling the driver receives from the steering means.
[0011]
Further , according to the configuration of the first aspect, the determination as to whether the steering is maintained or the steering is performed based on the motor rotational acceleration. Since the motor rotation acceleration, which is a differential value of the motor rotation speed, changes faster than the motor rotation speed at the start of the rotation of the electric motor, it is determined whether the steering is maintained or the steering state based on the motor rotation acceleration. The switching from the steered state to the steered state can be quickly detected. Therefore, it is possible to improve the responsiveness of the steering assist at steering rudder start.
[0012]
The invention according to claim 2 further includes torque differential value detection means (5, 66, S1, E1) for detecting a torque differential value which is a time change amount of the steering torque applied to the steering means, and the state The determining means determines whether the steering means is in a steering holding state or a steering state based on the torque differential value detected by the torque differential value detecting means and the motor rotational acceleration detected by the motor rotational acceleration detecting means. 2. The electric power steering control device according to claim 1 , wherein the electric power steering control device is discriminated .
According to the present invention, it is possible to more quickly detect a change from the steered state to the steering state, and it is possible to further improve the steering assist response at the start of steering.
Further, when the electric power steering control device performs proportional-integral control of the electric motor, the control gain setting means is configured to determine the proportional control gain of the electric motor based on the determination result of the state determination means. Alternatively, an integral control gain may be set.
[0013]
According to a third aspect of the present invention, the electric power steering control device further includes motor rotation speed detection means (8, 66, S2, Q2) for detecting a rotation speed of the electric motor, and the state determination means includes: 3. The system according to claim 1, further comprising referring to a motor rotation speed detected by the motor rotation speed detection means to determine whether the steering means is in a steering holding state or a steering state. This is an electric power steering control device.
[0014]
According to the present invention, since the motor rotational acceleration or the torque differential value and the motor rotational speed in addition to this are referred to determine whether the steering state is the steering holding state or the steering state, the switching from the steering holding state to the steering state is further performed. can be detected quickly, Ru can improve the responsiveness of the steering assist at the steering start.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention. The steering torque applied to the steering wheel 1 is mechanically transmitted to the steering mechanism 3 via the steering shaft 2, and at this time, the steering mechanism 3 is steered by applying torque (steering assisting force) from the electric motor M. Assistance is to be achieved.
[0016]
The steering shaft 2 is divided into an input shaft 2A coupled to the steering wheel 1 side and an output shaft 2B coupled to the steering mechanism 3 side. The input shaft 2A and the output shaft 2B are connected to the torsion bar 4. Are connected to each other. The torsion bar 4 is twisted according to the steering torque, and the direction and amount of the twist are detected by the torque sensor 5.
[0017]
For example, the torque sensor 5 is configured by a magnetic sensor that detects a magnetic resistance that changes in accordance with a change in the positional relationship between the input shaft 2A and the output shaft 2B in the rotational direction. The torque signal T output from the torque sensor 5 is input to the controller 6 (ECU). The controller 6 is further input with a vehicle speed V detected by the vehicle speed sensor 7 and a rotational speed R of the electric motor M detected by the motor rotational speed sensor 8.
[0018]
The controller 6 includes a current command value setting unit 61 that sets a current command value that is a current value to be supplied to the electric motor M based on the torque signal T and the vehicle speed V, and a current command value that is set by the current command value setting unit 61. And a subtractor 63 for obtaining a deviation between the motor current detected by the current detection circuit 62 (current actually flowing through the electric motor M) and a PI (Proportional-Integral: A PI control unit 64 that calculates a control value of the electric motor M by proportional integration control, and a motor drive circuit 65 that drives the electric motor M based on the control value output by the PI control unit 64 are provided.
[0019]
The controller 6 further sets a steering state determination unit 66 that determines whether the steering wheel 1 is in a steering holding state or a steering state, and a P gain Kp that is a gain of proportional control performed by the PI control unit 64. A P gain setting unit 67 and an I gain setting unit 68 for setting an I gain Ki that is a gain of integral control performed by the PI control unit 64 are provided.
A torque signal T output from the torque sensor 5 and a motor rotation speed R detected by the motor rotation speed sensor 8 are input to the steering state determination unit 66. Based on the torque signal T and the motor rotational speed R, the steering state determination unit 66 determines whether the steering wheel 1 is in the steering holding state or the steering state, and the determination result is used as the P gain setting unit 67 and the I gain. Input to the setting unit 68. P gain setting unit 67 and I gain setting unit 68 set P gain Kp and I gain Ki, respectively, based on the determination result input from steering state determination unit 66. The set P gain Kp and I gain Ki are input to the PI control unit 64, and the PI control unit 64 calculates the control value of the electric motor M using the P gain Kp and the I gain Ki.
[0020]
The current command value setting unit 61, the subtracting unit 63, the PI control unit 64, the steering state determination unit 66, the P gain setting unit 67, and the I gain setting unit 68 are, for example, a predetermined program process performed by a microcomputer built in the controller 6. By executing the above, each function may be realized by software.
FIG. 2 is a flowchart for explaining the processing by the steering state determination unit 66. The process shown in FIG. 2 is started in response to the ignition switch of the vehicle being turned on, and thereafter repeatedly performed until the ignition switch is turned off.
[0021]
The steering state discriminating unit 66 first calculates a torque differential value dT / ds by obtaining a time change of the torque signal T input from the torque sensor 5. Then, it is determined whether or not the torque differential value dT / ds is equal to or less than a certain value A (for example, 1 (Nm / sec)) (step S1). In a state in which the steering wheel 1 is being steered by the driver, the force applied to the steering wheel 1 hardly fluctuates, so that the torque differential value dT / ds is a constant value A or less.
[0022]
If the torque differential value dT / ds is equal to or less than the constant value A, the steering state determination unit 66 next refers to the motor rotation speed R detected by the motor rotation speed sensor 8. Then, it is determined whether or not the motor rotation speed R is a predetermined value B (for example, 1 (rad / sec)) or less (step S2). For example, when the steering wheel 1 is being held near the neutral position (the position of the steering wheel 1 when the vehicle is traveling straight), the electric motor M stops or rotates at a very low speed. The determination of whether or not it is below a certain value B is affirmed.
[0023]
Therefore, when the torque differential value dT / ds is equal to or less than the constant value A and the motor rotation speed R is equal to or less than the constant value B, the steering state determination unit 66 determines that the steering wheel 1 is in the steering holding state. Judgment is made (step S3). On the other hand, when the torque differential value dT / ds is larger than the constant value A or the motor rotational speed R is larger than the constant value B, it is determined that the steering wheel 1 is in a steering state (step S4). The determination result of the steering state determination unit 66 is given to the P gain setting unit 67 and the I gain setting unit 68.
[0024]
The P gain setting unit 67 and the I gain setting unit 68 set the P gain Kp and the I gain Ki according to the characteristic lines α and β shown in FIG. 3 based on the determination result of the steering state determination unit 66, respectively.
That is, when it is determined that the steering wheel 1 is in the steering state, the P gain Kp and the I gain Ki are generated from the electric motor M with sufficient steering assisting force according to the steering torque and the vehicle speed, respectively. Are set to the steering-time P gain Kps and the steering-time I gain Kis that are appropriately determined as follows. On the other hand, when it is determined that the steering wheel 1 is in the holding state, the P gain Kp and the I gain Ki are respectively set to the holding time P gain Kph and the holding time I gain Kih. The The steering holding P gain Kph and the steering holding I gain Kih are set to values smaller than the steering P gain Kps and the steering I gain Kis, respectively.
[0025]
Thereby, when the steering wheel 1 is in the holding state, the control value of the electric motor M calculated using the holding P gain Kph and the holding I gain Kih becomes a relatively small value. Since the amount of flowing current is suppressed, the steering wheel 1 can be prevented from being vibrated slightly. Therefore, the steering feeling in the steered state can be improved.
In this embodiment, when the steering wheel 1 is changed from the steering state to the steered state, the P gain Kp and the I gain Ki are changed from the steered P gain Kps and the steered I gain Kis, respectively. Instead of instantaneously changing to Kph and holding I gain Kih, a certain time Δt is applied from the steering P gain Kps and steering I gain Kis to the holding P gain Kph and holding I gain Kih. Is set to decrease linearly. Further, when the steering wheel 1 is changed from the holding state to the steering state, the P gain Kp and the I gain Ki are respectively changed from the holding P gain Kph and the holding I gain Kih to the steering P gain Kps and the steering. It is not changed instantaneously to the hour I gain Kis, but linearly taking a certain time Δt from the steering holding P gain Kph and the steering holding I gain Kih to the steering P gain Kps and steering I gain Kis. Set to increase.
[0026]
As a result, when the steering wheel 1 is held or started to be steered, the steering wheel 1 can be prevented from suddenly becoming heavy or light, and the feeling received by the driver from the steering wheel 1 can be improved. . As described above, according to this embodiment, it is determined whether the steering wheel 1 is in the steering holding state or the steering state, and the P gain Kp and the I gain Ki are appropriately determined based on the determination result. Thus, a good steering feeling can be realized.
[0027]
In this embodiment, since it is determined whether the steering state is the steering state or the steering state based on both the torque differential value dT / ds and the motor rotational speed R, the steering state is determined based on only the motor rotational speed R. Compared with the configuration for determining whether or not the steering wheel 1 is in a state, the steering wheel 1 is more responsive in determining the state of the steering wheel 1 when steering is started from a state where the steering wheel 1 is held near the neutral position. The possibility of delays can be eliminated.
[0028]
FIG. 4 is a flowchart for explaining a second embodiment of the present invention. In the first embodiment described above, based on the torque differential value dT / ds and the motor rotation speed R, it is determined whether or not the steering wheel 1 is in the steered state or the steered state. Based on the differential value dT / ds and the motor rotation acceleration dR / ds, which is the amount of time change of the motor rotation speed R, it is determined whether the steering wheel 1 is in the steering holding state or the steering state.
[0029]
That is, it is determined whether or not the torque differential value dT / ds is equal to or less than a certain value A (step E1). If the torque differential value dT / ds is equal to or less than a certain value A, then the motor rotational acceleration dR / ds is calculated by obtaining the derivative of the motor rotational speed R detected by the motor rotational speed sensor 8. Then, it is determined whether or not the motor rotational acceleration dR / ds is below a certain value C (for example, 20 (rad / sec ² )) (step E2). In the state where the steering wheel 1 is being held, the electric motor M is almost stopped, and the determination of whether or not the motor rotational acceleration dR / ds is equal to or less than a certain value C is affirmed. Then, when the steering wheel 1 is steered from the state where the steering is maintained, the value of the motor rotational acceleration dR / ds becomes large and becomes larger than the constant value C at the moment when the steering is started.
[0030]
Accordingly, when the torque differential value dT / ds is equal to or less than the constant value A and the motor rotational acceleration dR / ds is equal to or less than the constant value C, it is determined that the steering wheel 1 is in the steering holding state (step E3). On the other hand, if the torque differential value dT / ds is greater than the constant value A or the motor rotational acceleration dR / ds is greater than the constant value C, it is determined that the steering wheel 1 is in the steering state (step E4). ).
[0031]
Even in the determination method according to the second embodiment, as in the case of the first embodiment, the determination method is determined based on only the motor rotation speed R to determine whether the steering is held or the steering state. Particularly, when the steering is started from the state where the steering wheel 1 is held near the neutral position, the responsiveness of the state determination of the steering wheel 1 is improved, and it is possible to eliminate the possibility of delay in steering assistance.
FIG. 5 is a flowchart for explaining a third embodiment of the present invention. In the third embodiment, based on the motor rotation acceleration dR / ds and the motor rotation speed R, it is determined whether the steering wheel 1 is in the steering holding state or the steering state.
[0032]
That is, when the motor rotational acceleration dR / ds is equal to or less than a certain value C (YES in step Q1) and the motor rotation speed R is equal to or less than a certain value B (YES in step Q2), the steering wheel 1 is maintained. It is determined that the vehicle is in the rudder state (step Q3). On the other hand, when the motor rotational acceleration dR / ds is larger than the constant value C or the motor rotational speed R is larger than the constant value B, it is determined that the steering wheel 1 is in the steering state (step Q4).
[0033]
Even in the determination method according to the third embodiment, as in the case of the first and second embodiments, a determination is made as to whether the steering is maintained or the steering state based only on the motor rotational speed R. In comparison, in particular, when the steering is started from a state where the steering wheel 1 is held near the neutral position, the responsiveness of the state determination of the steering wheel 1 is improved, and there is no possibility of delay in steering assistance. it can.
As mentioned above, although some embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, It can also be implemented with another form. For example, based on the torque differential value dT / ds, the motor rotation acceleration dR / ds, and the motor rotation speed R, it may be determined whether the steering wheel 1 is in the steered state or the steering state.
[0034]
Further, based on either the torque differential value dT / ds or the motor rotational acceleration dR / ds, it may be determined whether the steering wheel 1 is in the steered state or the steered state. Since the torque differential value dT / ds is a value unrelated to the rotation state of the electric motor M, even if the steering wheel 1 is turned to one side from the state where the steering wheel 1 is held at the neutral position, Switching to the steering state can be detected instantaneously. Further, since the motor rotational acceleration dR / ds, which is a differential value of the motor rotational speed R, changes faster than the motor rotational speed R at the start of the rotation of the electric motor, the steering state is maintained based on the motor rotational acceleration dR / ds. Also, by determining whether the vehicle is in the steering state, it is possible to quickly detect the change from the steered state to the steering state. Accordingly, when it is determined whether the steering state is the steering state or the steering state based on one of the torque differential value dT / ds or the motor rotational acceleration dR / ds, whether the steering state is the steering state or the steering state based only on the motor rotational speed R. Compared with the case of performing the determination, the response of the state determination of the steering wheel 1 is improved, and the response of the steering assist at the start of steering can be improved.
[0035]
Further, when the steering wheel 1 is changed from the steering state to the steered state or from the steered state to the steered state, the P gain Kp and the I gain Ki according to the linear portions of the characteristic lines α and β shown in FIG. However, the P gain Kp and the I gain Ki may be gradually decreased or gradually increased, for example, according to nonlinear characteristic lines α ′ and β ′ as indicated by two-dot chain lines in FIG.
In the above-described embodiment, the P gain Kp and the I gain Ki are set so as to linearly decrease or increase over a certain time Δt. The length of the fixed time Δt may be varied within a range where there is no risk of damage.
[0036]
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining steering state determination processing;
FIG. 3 is a diagram for explaining a setting example of P gain and I gain;
FIG. 4 is a flowchart for explaining a second embodiment of the present invention.
FIG. 5 is a flowchart for explaining a third embodiment of the present invention;
[Explanation of symbols]
1 Steering wheel (steering means)
3 Steering mechanism 5 Torque sensor 6 Controller 61 Current command value setting unit 62 Current detection circuit 63 Subtraction unit 64 PI control unit 65 Motor drive circuit 66 Steering state determination unit (torque differential value detection unit, motor rotation acceleration detection unit, motor rotation speed Detection means, state discrimination means)
67 P gain setting section (control gain setting means)
68 I gain setting section (control gain setting means)
8 Motor rotation speed sensor (Motor rotation speed detection means)
M Electric motor

Claims (4)

An electric power steering control device for controlling an electric motor that gives a steering assist force to a steering mechanism of a vehicle based on steering of a steering means,
Motor rotation acceleration detecting means for detecting motor rotation acceleration which is a time change amount of the rotation speed of the electric motor;
Based on the motor rotational acceleration detected by the motor rotational acceleration detecting means, state discriminating means for discriminating whether the steering means is in a steering holding state or a steering state;
An electric power steering control device comprising: control gain setting means for setting a control gain of the electric motor based on a determination result of the state determination means.   A torque differential value detection means for detecting a torque differential value that is a time change amount of the steering torque applied to the steering means;
  The state determination means is based on the torque differential value detected by the torque differential value detection means and the motor rotational acceleration detected by the motor rotational acceleration detection means, or the steering means is in a steering holding state or in a steering state. And determining whether or not 1 The electric power steering control device described. The electric power steering control device further includes motor rotation speed detection means for detecting the rotation speed of the electric motor,
The state determining means further refers to the motor rotation speed detected by the motor rotation speed detection means, and determines whether the steering means is in a steered state or a steering state. The electric power steering control device according to claim 1 or 2.   The control gain setting means sets the control gain of the electric motor so as to gradually decrease to a first constant value when the state determination means determines that the steering means is in a steered state, When it is determined that the steering means is in a steering state, the control gain of the electric motor is set so as to gradually increase to a second constant value larger than the first constant value. The electric power steering control device according to any one of claims 1 to 3.

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