JP2014125036A - Electric power-steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique enabling easy setup change of control in accordance with the category of vehicle to be incorporated in, the control for suppressing a condition under which steering torque must be exerted to a steering wheel during a straight travel.SOLUTION: A power-steering device includes: an electric motor for providing an operation on a steering wheel incorporated in a vehicle with assist force; a provisional target current determination part 25 for determining a provisional value of a target current to be supplied to the motor on the basis of steering torque of the steering wheel and a vehicle speed; a steering-hold assist current calculation part 27 for calculating a steering-hold assist current that is a current for the motor to provide assist force in accordance with a steering-hold operation on the steering wheel; and a final target current determination part 28 for determining a target current on the basis of the provisional value determined by the provisional target current determination part 25 and the steering-hold assist current calculated by the steering-hold assist current calculation part 27.

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, in an electric power steering device that assists a driver's steering force with the power of an electric motor provided in a vehicle steering system, a base assist force that is the basis of the assist force by the electric motor is determined according to the steering torque. However, normally, when the steering torque is within a predetermined range, a so-called dead zone is set in which the base assist force is zero regardless of the value of the steering torque.

  On the other hand, when there is a disturbance such as an inclination (cant) in the vehicle width direction or a strong crosswind provided in the traveling path of the vehicle, a minute steering torque is continuously applied to the steering wheel even during straight traveling. It will be necessary. However, if the steering torque applied during straight running is very small and is within the dead zone, the assist force is not applied by the electric motor, and the driver must continuously apply the small steering torque. I will have to. In particular, when the road is in a cant state when driving on an expressway or when a strong crosswind is blowing, the steering torque must be applied for a long time, and the burden is extremely large.

  On the other hand, for example, the apparatus described in Patent Document 1 is configured as follows. That is, based on the detected vehicle speed, lateral acceleration, steering state, and travel environment information, and at least a teacher signal associated with the travel lane of the vehicle, the cant state of the travel path of the vehicle is learned, and the vehicle speed, lateral acceleration, The system includes a steering ECU that includes a cant state determination unit that performs a neural network calculation using the learning result based on the steering state and the travel environment information, and determines a cant state of the travel path of the vehicle. A control component for suppression is calculated.

JP 2007-22169 A

Since there are various types of vehicles on which the electric power steering apparatus is mounted, it is desirable that the control of the apparatus can be easily set and changed according to the type of the vehicle.
The present invention provides an electric power steering apparatus capable of easily changing the setting for suppressing the necessity of continuing to apply steering torque to the steering wheel during straight traveling according to the type of vehicle mounted. The purpose is to do.

  For this purpose, the present invention provides an electric motor that provides an assisting force for the operation of a steering wheel provided in a vehicle, and a target that is supplied to the electric motor based on the steering torque of the steering wheel and the vehicle speed of the vehicle. Temporary target current determining means for determining a temporary value of current, and steering auxiliary current calculation for calculating a steering auxiliary current that is an electric current for the electric motor to provide an assist force according to the steering operation of the steering wheel. Means, and a target current determining means for determining the target current based on the temporary value determined by the temporary target current determining means and the steering auxiliary current calculated by the steering auxiliary current calculating means. This is an electric power steering device.

Here, it is preferable that the steering assist current calculating means increases the absolute value of the steering assist current as the steering time of the steering wheel is longer.
The steering assist current calculation means may include a steering direction determination means for determining a steering direction, and calculate the steering maintenance current based on the steering direction determined by the steering direction determination means. .

  ADVANTAGE OF THE INVENTION According to this invention, it can make it easy to carry out the setting change of the control for suppressing that it is necessary to continue giving a steering torque to a steering wheel at the time of a straight drive according to the kind of vehicle mounted.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is a schematic block diagram of a target current calculation part. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a control part. It is a schematic block diagram of a steering auxiliary current calculation part. It is a figure which shows the relationship between the code | symbol of steering torque, and the code | symbol of the rotation direction of an electric motor. It is a figure which shows the steering auxiliary base current control map which shows a response | compatibility with the absolute value of steering torque, and the absolute value of steering auxiliary base current. (A) is a figure which shows the torque index control map which shows a response | compatibility with a steering torque and a torque index, (b) is a figure which shows the rotation speed index control map which shows a response | compatibility with a rotational speed and a rotational speed index | exponent. It is a figure which shows the correction | amendment electric current control map which shows a response | compatibility with an integrated value and correction | amendment electric current. It is a figure which shows the control map which shows a response | compatibility with a vehicle speed and a vehicle speed coefficient. (A) is a figure which shows the transition coefficient control map which shows a response | compatibility with the rotational speed and transition coefficient when a steering direction is a right direction, (b) is a rotational speed when a steering direction is a left direction, It is a figure which shows the transition coefficient control map which shows a response | compatibility with a transition coefficient.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
Electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle, and in this embodiment, an automobile as an example of the vehicle. The structure applied to is illustrated.

  The steering apparatus 100 includes a wheel-like steering wheel 101 that is operated by a driver to change the traveling direction of the automobile, and a steering shaft 102 that is provided integrally with the steering wheel 101. . The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via a torsion bar (not shown) in the steering gear box 107. A torque sensor 109 that detects the steering torque T of the steering wheel 101 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106 is provided inside the steering gear box 107.

  The steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a speed reducing mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106. Electric motor 110 according to the present embodiment is a three-phase brushless motor. The speed reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) fixed to the output shaft of the electric motor 110, and the like.

  In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. An output signal from the torque sensor 109 described above is input to the control device 10. In addition, the control device 10 includes a vehicle speed sensor 170 that detects a vehicle speed Vc, which is a moving speed of the vehicle, via a network (CAN) that performs communication for sending signals for controlling various devices mounted on the vehicle. The output signal from is input.

  The steering device 100 configured as described above detects the steering torque T applied to the steering wheel 101 by the torque sensor 109, drives the electric motor 110 in accordance with the detected torque, and generates torque generated by the electric motor 110. Is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 includes a torque signal Td obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. v or the like is input.

Then, the control device 10 calculates a target auxiliary torque based on the torque signal Td and the vehicle speed signal v, and calculates a target current It necessary for the electric motor 110 to supply the target auxiliary torque. 20 and a control unit 30 that performs feedback control or the like based on the target current It calculated by the target current calculation unit 20.
In addition, the control device 10 includes a motor rotation speed calculation unit 70 that calculates the rotation speed Nm of the electric motor 110. The motor rotation speed calculation unit 70 calculates the rotation speed Nm of the electric motor 110 based on the output signal from the resolver that detects the rotation position of the rotor (rotor) of the electric motor 110 that is a three-phase brushless motor, and the rotation thereof. A rotation speed signal Nms in which the speed Nm is converted into an output signal is output.

Next, the target current calculation unit 20 will be described in detail.
FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current Ib that serves as a reference for setting the target current, and an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110. And a damper compensation current calculation unit 23 for calculating a current for limiting the rotation of the motor. Further, the target current calculation unit 20 determines a temporary target current Itf that is a temporary target current based on the values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. A temporary target current determination unit 25 is provided as an example of a temporary target current determination unit. Further, the target current calculation unit 20 is a steering auxiliary current calculating unit that calculates a steering auxiliary current Ir that is an electric current for the electric motor 110 to give an assist force corresponding to the steering time (situation) of the steering wheel 101. As an example, the steering auxiliary current calculating unit 27, the temporary target current Itf determined by the temporary target current determining unit 25, and the steering auxiliary current Ir calculated by the steering auxiliary current calculating unit 27 are finally used. And a final target current determining unit 28 as an example of target current determining means for determining the target current It.
The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, a rotation speed signal Nms output from the motor rotation speed calculation unit 70, and the like.

FIG. 4 is a schematic diagram of a control map showing the correspondence between the steering torque T, the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 calculates the base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 (see FIG. 3) and the vehicle speed signal v from the vehicle speed sensor 170. That is, the base current calculation unit 21 calculates the base current Ib according to the phase-compensated steering torque T and the vehicle speed Vc. The base current calculation unit 21 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current that are created in advance based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map illustrated in FIG. 4 showing the correspondence with Ib.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current Is for canceling the moment of inertia of the electric motor 110 and the system based on the torque signal Ts and the vehicle speed signal v. That is, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v). Note that the inertia compensation current calculation unit 22 generates, for example, the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the inertia compensation current Is, which are previously created based on empirical rules and stored in the ROM. The inertia compensation current Is is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map indicating the correspondence between the two.

  The damper compensation current calculation unit 23 calculates a damper compensation current Id for limiting the rotation of the electric motor 110 based on the torque signal Ts, the vehicle speed signal v, and the rotation speed signal Nms of the electric motor 110. That is, the damper compensation current calculation unit 23 calculates the damper compensation current Id according to the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotational speed Nm (rotational speed signal Nms) of the electric motor 110. calculate. For example, the damper compensation current calculation unit 23 is prepared based on an empirical rule and stored in the ROM in advance, such as steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and rotation speed Nm (rotation). By substituting steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and rotational speed Nm (rotational speed signal Nms) into a control map indicating the correspondence between speed signal Nms) and damper compensation current Id. A damper compensation current Id is calculated.

The temporary target current determination unit 25 includes a base current Ib calculated by the base current calculation unit 21, an inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and a damper calculated by the damper compensation current calculation unit 23. A temporary target current Itf is determined based on the compensation current Id. For example, the temporary target current determination unit 25 determines the current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id as the temporary target current Itf.
The steering auxiliary current calculation unit 27 will be described in detail later.

  The final target current determination unit 28 finally determines the target current It based on the temporary target current Itf determined by the temporary target current determination unit 25 and the steering auxiliary current Ir calculated by the steering auxiliary current calculation unit 27. To decide. The final target current determining unit 28 according to the present embodiment adds the temporary target current Itf determined by the temporary target current determining unit 25 and the steering auxiliary current Ir calculated by the steering auxiliary current calculating unit 27. The current obtained in this way is determined as the target current It.

Next, the control unit 30 will be described in detail.
FIG. 5 is a schematic configuration diagram of the control unit 30.
As shown in FIG. 5, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 for detection.
The motor drive control unit 31 is based on a deviation between the target current It finally determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 that performs feedback control, and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

  The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current It finally determined by the target current calculating unit 20 and the actual current Im detected by the motor current detecting unit 33, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.

The feedback (F / B) processing unit 42 performs feedback control so that the target current It and the actual current Im match. For example, the feedback (F / B) processing unit 42 is proportional to the deviation calculated by the deviation calculating unit 41. Is proportionally processed, integrated by an integral element, and these values are added by an addition operation unit.
The PWM signal generation unit 60 generates a PWM signal for driving the electric motor 110 by PWM (pulse width modulation) based on the output value from the feedback control unit 40, and outputs the generated PWM signal.

The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.

Next, the steering auxiliary current calculation unit 27 will be described in detail.
FIG. 6 is a schematic configuration diagram of the steering assist current calculating unit 27.
The steering assist current calculation unit 27 includes a torque noise cut unit 310 that cuts noise of the torque signal Td, a steering condition determination unit 320 that determines the steering condition of the steering wheel 101, and a maintenance assist base Ir. A steering auxiliary base current calculation unit 330 that calculates the steering auxiliary base current Irb. In addition, the steering auxiliary current calculation unit 27 calculates the steering integrated time correction current calculation unit 340 that calculates the correction current Ic according to the time during which the steering wheel 101 is held, and the steering auxiliary base current calculation unit 330 calculates. And an addition unit 350 that adds the corrected auxiliary current Ic calculated by the integrated steering time correction current calculation unit 340. Further, the steering auxiliary current calculation unit 27 is added by the vehicle speed coefficient calculation unit 360 that calculates the vehicle speed coefficient Kv corresponding to the vehicle speed Vc, the transition coefficient calculation unit 370 that calculates the transition coefficient Ks, and the addition unit 350. This is obtained by multiplying the total value of the steering assist base current Irb and the correction current Ic by the vehicle speed coefficient Kv calculated by the vehicle speed coefficient calculation unit 360 and the transition coefficient Ks calculated by the transition coefficient calculation unit 370. And a multiplication unit 380 that sets the steering assist current Ir as a value.

  The torque noise cut unit 310 sets the steering torque T to zero when the torque signal Td is within a predetermined minute region centered on a predetermined output value indicating that the steering torque T is zero. In addition, the noise of the torque signal Td is cut. Then, the torque noise cut unit 310 outputs a noise signal Td ′ from which noise has been cut.

Next, the steering situation determination unit 320 will be described in detail.
The steering situation determination unit 320 determines the steering situation based on the torque signal Td ′ from which noise has been cut by the torque noise cut unit 310 and the rotational speed signal Nms of the electric motor 110.
Here, the state in which the torsion bar twist is zero is defined as the neutral state (neutral position), and the steering wheel 101 (lower connection shaft 108) and the pinion shaft 106 when the steering wheel 101 rotates clockwise from the neutral state (neutral position). The direction in which the relative rotation angle changes (the direction in which the relative rotation angle occurs) is positive (the steering torque T is positive). On the other hand, the direction in which the relative rotation angle between the steering wheel 101 (lower connection shaft 108) and the pinion shaft 106 changes when the steering wheel 101 rotates counterclockwise from the neutral state (the direction in which the relative rotation angle occurs) is negative (steering). Torque T is negative). At this time, it is an output value from the torque sensor 109 when the relative rotation angle between the steering wheel 101 and the pinion shaft 106 is twisted in the clockwise direction from the neutral state (the torsion bar is twisted in the clockwise direction). Torque signal from the torque sensor 109 when the sign of the torque signal Td (torque signal Td ′) is plus and the relative rotation angle is twisted counterclockwise from the neutral state (the torsion bar is twisted counterclockwise) The sign of Td (torque signal Td ′) is negative.

  When the sign of the torque signal Td (torque signal Td ′) from the torque sensor 109 is positive, the base current calculation unit 21 calculates the base current Ib so as to rotate the electric motor 110 in one rotation direction. The direction in which the base current Ib flows is positive. That is, as shown in FIG. 4, when the sign of the torque signal Td (torque signal Td ′) from the torque sensor 109 is positive and the steering torque T is positive, the base current calculation unit 21 calculates a positive base current Ib. Then, torque is generated in a direction that causes the electric motor 110 to rotate in one rotation direction. On the other hand, when the sign of the torque signal Td (torque signal Td ′) from the torque sensor 109 is negative, the base current calculation unit 21 calculates a negative base current Ib and rotates the electric motor 110 in the other rotation direction. Torque is generated.

  The worm gear mounted on the output shaft of the electric motor 110 and the worm wheel rotating together with the pinion shaft 106 are meshed with each other, and the rack teeth formed on the pinion 106 a and the rack shaft 105 formed on the lower end portion of the pinion shaft 106. 105a constitutes a rack and pinion mechanism. Further, the rack shaft 105 is connected to the tie rod 104 connected to the front wheel 150.

  Therefore, when no load is generated on the front wheel 150, when the electric motor 110 rotates in one rotation direction, the pinion shaft 106 moves the rack shaft 105 in the lateral direction as viewed in FIG. Rotates to the right. Hereinafter, the movement direction of the rack shaft 105 when the front wheel 150 rotates in the right direction is referred to as “one movement direction”. On the other hand, when the electric motor 110 rotates in the other rotation direction, the pinion shaft 106 moves the rack shaft 105 in the lateral direction, and the front wheel 150 rotates in the left direction. Hereinafter, the movement direction of the rack shaft 105 when the front wheel 150 rotates in the left direction is referred to as “the other movement direction”.

Further, even if the sign of the torque signal Td (torque signal Td ′) from the torque sensor 109 is positive and the electric motor 110 generates torque in the direction of rotation in one rotation direction, the external force received by the front wheels 150 and the like. When the front wheel 150 rotates leftward and the rack shaft 105 moves in the other moving direction, the electric motor 110 rotates in the other rotating direction.
On the other hand, even if the sign of the torque signal Td (torque signal Td ′) from the torque sensor 109 is negative and the electric motor 110 generates torque in the direction of rotation in the other rotation direction, the external force received by the front wheels 150 and the like. Thus, when the front wheel 150 rotates rightward and the rack shaft 105 moves in one movement direction, the electric motor 110 rotates in one rotation direction.

  Hereinafter, the sign of the rotation direction of the electric motor 110 is positive when rotating in one rotation direction, and negative when rotating in the other rotation direction. Further, when the electric motor 110 rotates in one rotation direction, the sign of the rotation speed signal Nms of the electric motor 110 becomes plus, and when the electric motor 110 rotates in the other rotation direction, the sign of the rotation speed signal Nms of the electric motor 110. Is negative.

Next, the relationship between the sign of the steering torque T (sign of the torque signal Td from the torque sensor 109) and the sign of the rotation direction of the electric motor 110 (sign of the rotation speed signal Nms) will be described.
FIG. 7 is a diagram showing the relationship between the sign of the steering torque T (torque signal Td (torque signal Td ′)) and the sign of the rotation direction of the electric motor 110 (rotation speed signal Nms). (A) is the figure which showed the code | symbol of the torque signal Td (torque signal Td ') from the torque sensor 109, and the code | symbol of the rotation direction of the electric motor 110 in time series. (B) shows the steering torque T (torque signal Td (torque signal Td ′) from the torque sensor 109) on the vertical axis and the rotational direction (rotational speed signal Nms) of the electric motor 110 on the horizontal axis. FIG. 6 is a diagram showing a relationship between the steering wheel 101 and the steering state of the steering wheel 101.

  When the steering wheel 101 is rotated rightward from the neutral state (the steering torque T is zero), the amount of twisting of the torsion bar in the rightward rotation direction increases. As a result, the torque signal Td (torque signal Td ′) from the torque sensor 109 increases in the positive direction, and the electric motor 110 rotates in the positive direction. This state is shown in the first region of FIG. 7A. In this state, the steering torque T (torque signal Td (torque signal Td ′)) and the rotation direction of the electric motor 110 (rotation speed signal Nms) are shown. Both are positive.

  Thereafter, when the steering wheel 101 is rotated to the left (when the steering torque T is weakened), the torsion bar torsion is alleviated, and the torque signal Td (torque signal Td ′) from the torque sensor 109 decreases. Then, even if the front wheel 150 rotates to the left due to the external force received by the front wheel 150 and the like and the electric motor 110 generates torque in the direction of rotation in one rotation direction, the rack shaft 105 moves in the other movement direction. . As a result, the electric motor 110 rotates in the other rotation direction. This state is shown in the second region of FIG. 7A. In this state, the sign of the steering torque T (torque signal Td (torque signal Td ′)) is positive, but the rotation of the electric motor 110 The sign of the direction is negative.

  Thereafter, when the steering wheel 101 is rotated counterclockwise beyond the neutral state (neutral position), the amount of twist in the counterclockwise direction of the torsion bar increases, and the steering torque T (torque signal Td (torque signal Td ′)). Increases in the negative direction. The rack shaft 105 continues to move in the other movement direction as it is, but even if the electric motor 110 generates torque in the direction in which the electric motor 110 rotates in the other rotation direction, the external force received by the front wheels 150 or the like causes the movement in the other movement direction. Movement is suppressed. As a result, the electric motor 110 continues to rotate in the minus direction, but the rotational force gradually decreases. This state is shown in the third region of FIG. 7A. In this state, both the steering torque T (torque signal Td (torque signal Td ′)) and the rotation direction of the electric motor 110 are negative.

  Thereafter, when the steering wheel 101 is rotated in the right direction (when the steering torque T is weakened), the torsion bar twist is alleviated and the steering torque T (torque signal Td (torque signal Td ′)) approaches zero. Then, even if the front wheel 150 rotates rightward due to the external force received by the front wheel 150 and the like, and the electric motor 110 generates torque in the direction of rotation in the other rotation direction, the rack shaft 105 moves in one movement direction. . As a result, the electric motor 110 rotates in one rotation direction. This state is shown in the fourth region of FIG. 7A. In this state, the sign of the steering torque T (torque signal Td (torque signal Td ′)) is negative, but the rotation of the electric motor 110 The direction sign is positive.

  Due to the above, the region where the steering torque T (torque signal Td (torque signal Td ′)) and the rotation direction of the electric motor 110 (rotational speed signal Nms) are both positive (the first region in FIG. 7A) is As the steering state of the steering wheel 101, the steering wheel 101 is turned rightward. A region where the steering torque T (torque signal Td (torque signal Td ′)) is positive and the rotation direction of the electric motor 110 (rotational speed signal Nms) is negative (second region in FIG. 7A) is as follows. The steering state of the steering wheel 101 is a state in which the steering wheel 101 is turned back to the left after being turned to the right.

  Further, a region where the steering torque T (torque signal Td (torque signal Td ′)) and the rotation direction of the electric motor 110 (rotational speed signal Nms) are both negative (third region in FIG. 7A) is a steering wheel. The steering state 101 is a state in which the steering wheel 101 is turned leftward. A region where the steering torque T (torque signal Td (torque signal Td ′)) is negative and the rotation direction of the electric motor 110 (rotational speed signal Nms) is positive (fourth region in FIG. 7A) is: As a steering state of the steering wheel 101, the steering wheel 101 is turned back to the right after being turned to the left.

  Thus, as shown in FIG. 7B, the sign of the steering torque T (torque signal Td (torque signal Td ′)) and the sign of the rotation direction of the electric motor 110 (rotation speed signal Nms) are the same. In this situation, the steering wheel 101 is increased in the right direction or the left direction. On the other hand, when the sign of the steering torque T (torque signal Td (torque signal Td ′)) and the sign of the rotation direction of the electric motor 110 (rotational speed signal Nms) are different, the steering wheel 101 is switched back. It is in.

  However, in the present embodiment, the steering state called “steering” is not limited to the state in which the rotation of the steering wheel 101 is completely stopped, but has a certain range in the steering speed and steering torque T. In view of the state including the state of the steering wheel, the absolute value of the rotational speed Nm (rotational speed signal Nms) of the electric motor 110 is less than the predetermined value Nm0 (−Nm0 <Nm (Nms) <Nm0). And When the steering torque T (torque signal Td (torque signal Td ′)) is positive and the absolute value of the rotational speed Nm (rotational speed signal Nms) of the electric motor 110 is less than a predetermined value Nm0 (−Nm0 <Nm ( Nms) <Nm0) in the right steering state, the steering torque T (torque signal Td) is negative, and the absolute value of the rotational speed Nm (rotational speed signal Nms) of the electric motor 110 is less than the predetermined value Nm0 (−Nm0). <Nm (Nms) <Nm0) is set to the left steering state.

  In view of such matters, the steering situation determination unit 320 performs steering based on the torque signal Td ′ from which noise has been cut by the torque noise cut unit 310 and the rotation speed signal Nms output from the motor rotation speed calculation unit 70. It is determined whether the wheel 101 is being turned up, turned back, or in a steered state, and whether they are in the right direction or left direction is determined. Then, information including the determination result is output to the steering auxiliary base current calculation unit 330, the steering integration time correction current calculation unit 340, and the transition coefficient calculation unit 370. Thus, the steering situation determination unit 320 functions as an example of a steering direction determination unit that determines the direction of steering.

  The steering assist base current calculation unit 330 calculates the base of the steering assist current Ir based on the torque signal Td ′ from which the noise has been cut by the torque noise cut unit 310 and the steering situation determined by the steering situation determination unit 320. A steering auxiliary base current Irb is calculated. That is, the steering assist base current calculation unit 330 has a value corresponding to the absolute value (| T |) of the steering torque T, and the sign of the operation direction of the steering wheel 101 determined by the steering situation determination unit 320. A steering auxiliary base current Irb is calculated.

FIG. 8 is a diagram showing a steering assist base current control map showing the correspondence between the absolute value (| T |) of the steering torque T and the absolute value of the steering assist base current Irb.
The steering assist base current calculation unit 330 first creates an absolute value (| T | (| Td ′ |) of the steering torque T (torque signal Td ′), which is previously created based on an empirical rule and stored in the ROM. ) And the absolute value of the steering auxiliary base current Irb, the absolute value (| T | (| Td) of the steering torque T (torque signal Td ′) is shown in the steering auxiliary base current control map as illustrated in FIG. '|)) Is substituted to calculate the absolute value of the steering auxiliary base current Irb. After that, the absolute value of the steering assist base current Irb is multiplied by the sign of the operation direction of the steering wheel 101 determined by the steering situation determination unit 320 (plus in the right direction, minus in the left direction) to thereby obtain the steering assist base current. Irb is calculated.

  As shown in FIG. 6, the steering integrated time correction current calculation unit 340 includes a steering index calculation unit 341 that calculates a steering index α that is an index corresponding to the degree (intensity) of steering, and a steering index calculation. The steering index integration unit 342 that integrates the integrated value Σα of the steering index α calculated by the unit 341, and the correction current calculation unit 343 that calculates the correction current Ic based on the integration value Σα integrated by the steering index integration unit 342. And.

  The steering index calculating unit 341 performs the steering maintenance based on the torque signal Td ′ from which noise is cut by the torque noise cutting unit 310 periodically (for example, every 1 ms) and the rotational speed signal Nms of the electric motor 110. The steering index α, which is an index corresponding to the degree (strength), is calculated. In other words, the steering index calculating unit 341 calculates the steering index α according to the steering torque T and the rotational speed Nm. More specifically, the steering index calculating unit 341 calculates a torque index αt corresponding to the steering torque T (torque signal Td ′) and a rotation speed index αn corresponding to the rotation speed Nm (rotation speed signal Nms). Then, the steering index α (= αt × αn) is calculated by multiplying the torque index αt and the rotation speed index αn. Note that the steering index calculation unit 341 is, for example, a torque index control map that indicates the correspondence between the steering torque T (torque signal Td ′) and the torque index αt that is created in advance based on empirical rules and stored in the ROM. The torque index αt is calculated by substituting the steering torque T (torque signal Td ′). Further, the steering index calculating unit 341, for example, is a rotational speed index that indicates the correspondence between the rotational speed Nm (rotational speed signal Nms) and the rotational speed index αn that is created based on an empirical rule and stored in the ROM in advance. The rotational speed index αn is calculated by substituting the rotational speed Nm (rotational speed signal Nms) into the control map.

FIG. 9A is a diagram showing a torque index control map showing the correspondence between the steering torque T (torque signal Td ′) and the torque index αt, and FIG. 9B shows the rotation speed Nm (rotation speed signal Nms). ) And a rotation speed index αn. FIG.
In the torque index control map according to the present embodiment, the torque index αt is zero when the absolute value of the steering torque T is equal to or less than a predetermined first threshold value T1 (−T1 ≦ T ≦ T1), When it is equal to or greater than 2 threshold value T2 (T ≦ −T2 or T ≧ T2), it is set to be 1. When the absolute value of the steering torque T is in the range from the first threshold value T1 to the second threshold value T2 (−T2 <T <−T1 or T1 <T <T2), the torque index αt is determined by the steering It is set to increase from zero to 1 as the absolute value of the torque T increases.

  In the rotational speed index control map according to the present embodiment, the rotational speed index αn is 1 when the absolute value of the rotational speed Nm is equal to or less than a predetermined first threshold value Nm1 (−Nm1 ≦ Nm ≦ Nm1). When it is equal to or more than a predetermined second threshold value Nm2 (Nm ≦ −Nm2 or Nm ≧ Nm2), it is set to be zero. When the absolute value of the rotational speed Nm is in the range from the first threshold value Nm1 to the second threshold value Nm2 (−Nm2 <Nm <−Nm1 or Nm1 <Nm <Nm2), the rotational speed index αn is It is set to decrease from 1 to zero as the absolute value of the rotational speed Nm increases.

  The steering index integration unit 342 periodically (eg, every 1 ms) integrates the steering index α calculated by the steering index calculation unit 341 during the period in which the steering condition determination unit 320 determines that the steering state is maintained. Then, the integrated value Σα is output. That is, the steering index integration unit 342 acquires the steering index α calculated by the steering index calculation unit 341 when the steering status determination unit 320 acquires a signal indicating that the steering state in the right direction or the left direction has started. Then, the integrated value Σα is periodically output to the correction current calculation unit 343. And the steering index integration | stacking part 342 complete | finishes the integration, when the signal to the effect that the steering maintenance state was complete | finished from the steering condition determination part 320 was acquired. The steering index integrating unit 342 may periodically output zero as the integrated value Σα after the completion of the integration, or output a value obtained by gradually decreasing the integrated value Σα at the end as time elapses. May be.

  The correction current calculation unit 343 calculates the correction current Ic based on the integrated value Σα integrated by the steering index integration unit 342 and the steering situation determined by the steering situation determination unit 320. That is, the correction current calculation unit 343 has a value corresponding to the integrated value Σα integrated by the steering index integration unit 342, and the correction current of the sign of the operation direction of the steering wheel 101 determined by the steering situation determination unit 320. Ic is calculated.

FIG. 10 is a diagram showing a correction current control map showing the correspondence between the integrated value Σα and the correction current Ic.
First, the correction current calculation unit 343 is a correction current control map that indicates the correspondence between the integrated value Σα and the absolute value of the correction current Ic for each steering direction, which is previously created based on an empirical rule and stored in the ROM. Then, the absolute value of the correction current Ic is calculated by substituting the integrated value Σα. Thereafter, the correction current Ic is calculated by multiplying the absolute value of the correction current Ic by the sign of the operation direction of the steering wheel 101 determined by the steering situation determination unit 320 (plus in the right direction and minus in the left direction). In the correction current control map according to the present embodiment, as shown in FIG. 10, the absolute value of the correction current Ic is obtained when the integrated value Σα is equal to or less than a predetermined first time Σα1 (Σα ≦ Σα1). Is set to be the first predetermined amount Ic1 when zero is equal to or longer than the predetermined second time Σα2 (Σα ≧ Σα2). When the integrated value Σα is in the range from the first time Σα1 to the second time Σα2 (Σα1 <Σα <Σα2), the correction current Ic increases from zero to the first predetermined amount as the integrated value Σα increases. It is set so as to increase toward Ic1.

The vehicle speed coefficient calculation unit 360 calculates a vehicle speed coefficient Kv based on the vehicle speed signal v from the vehicle speed sensor 170. That is, the vehicle speed coefficient calculation unit 360 calculates the vehicle speed coefficient Kv corresponding to the vehicle speed Vc. For example, the vehicle speed coefficient calculation unit 360 creates a vehicle speed Vc (vehicle speed signal) on a control map that indicates the correspondence between the vehicle speed Vc (vehicle speed signal v) and the vehicle speed coefficient Kv, which is created in advance based on empirical rules and stored in the ROM. The vehicle speed coefficient Kv is calculated by substituting v).
FIG. 11 is a diagram showing a control map showing the correspondence between the vehicle speed Vc (vehicle speed signal v) and the vehicle speed coefficient Kv according to the present embodiment.
In the control map shown in FIG. 11, when the vehicle speed Vc is equal to or higher than the predetermined vehicle speed V1, the vehicle speed coefficient Kv is set to a constant vehicle speed coefficient Kv1, and the vehicle speed Vc is less than the predetermined vehicle speed V1. In this case, the vehicle speed coefficient Kv is set to gradually increase from zero to a constant vehicle speed coefficient Kv1 as the vehicle speed Vc increases.

  The transition coefficient calculation unit 370 calculates the transition coefficient Ks based on the rotation speed signal Nms of the electric motor 110 and the steering direction determined by the steering situation determination unit 320. That is, the transition coefficient calculation unit 370 calculates the transition coefficient Ks according to the rotation speed Nm and the steering direction. For example, the transition coefficient calculation unit 370 generates a rotation speed Nm in a transition coefficient control map that indicates the correspondence between the rotation speed Nm for each steering direction and the transition coefficient Ks, which is previously created based on an empirical rule and stored in the ROM. The transition coefficient Ks is calculated by substituting.

FIG. 12A is a diagram showing a transition coefficient control map showing the correspondence between the rotational speed Nm and the transition coefficient Ks when the steering direction is the right direction, and FIG. It is a figure which shows the transition coefficient control map which shows a response | compatibility with the rotational speed Nm in case of a direction, and the transition coefficient Ks.
In the transition coefficient control map according to the present embodiment, when the steering direction is the right direction, the transition coefficient Ks is −Nm0 or less, which is a value obtained by multiplying the rotation speed Nm by a predetermined value Nm0 by −1. It is set to 1 in the case (Nm ≦ −Nm0) and zero in the case of the predetermined value Nm0 or more (Nm ≧ Nm0). When the rotational speed Nm is in a range from −Nm0, which is a value obtained by multiplying the predetermined value Nm0 by −1 to a predetermined value Nm0 (−Nm0 <Nm <Nm0), the transition coefficient Ks is determined by the rotational speed Nm. It is set to gradually decrease from 1 to zero as becomes larger. On the other hand, when the steering direction is the left direction, the transition coefficient Ks is zero when the rotational speed Nm is equal to or less than −Nm0 (Nm ≦ −Nm0), which is a value obtained by multiplying the predetermined value Nm0 by −1. When it is equal to or greater than a predetermined value Nm0 (Nm ≧ Nm0), it is set to be 1. When the rotational speed Nm is in a range from −Nm0, which is a value obtained by multiplying the predetermined value Nm0 by −1 to a predetermined value Nm0 (−Nm0 <Nm <Nm0), the transition coefficient Ks is determined by the rotational speed Nm. It is set to gradually increase from zero to 1 as becomes larger.

  The multiplier 380 adds the steering auxiliary base current Irb and the correction current Ic added by the adder 350 to the vehicle speed coefficient Kv calculated by the vehicle speed coefficient calculator 360 and the transition coefficient calculator 370. And the value obtained by the multiplication is set as a steering auxiliary current Ir (= (Irb + Ic) × Kv × Ks).

  In the steering device 100 configured as described above, there is a disturbance such as an inclination (cant) in the vehicle width direction or a strong crosswind provided in the traveling path of the vehicle, and the maintenance according to the present embodiment. When the steering assist current calculation unit 27 is not provided, the temporary target current Itf determined by the temporary target current determination unit 25 of the target current calculation unit 20 becomes zero, and the steering must be maintained with a small steering torque T. In addition, an assist force is applied to the rudder by the electric motor 110. The assist force for the steering is increased as the time during which the steering is continued and / or as the steering torque T during the steering is increased. For example, a highway provided with a cant Steering load is reduced even when traveling for a long time.

  In the target current calculation unit 20 according to the present embodiment, the steering auxiliary current calculation unit 27 sets the temporary target current Itf determined by the temporary target current determination unit 25 based on the steering torque T, the vehicle speed Vc, and the like. The target current It is finally determined by adding the calculated steering assist current Ir. Therefore, even in the case where the magnitude of the steering auxiliary current Ir that gives the assist force in the steering holding state differs depending on the type of the vehicle on which the steering device 100 is mounted, the base current calculation unit 21, the inertia compensation current The configuration and / or control map of the steering auxiliary current calculation unit 27 is changed without changing the configuration of the calculation unit 22, the damper compensation current calculation unit 23, and the temporary target current determination unit 25 and / or the control map used by these. It can be handled only by Thereby, it is realized that the control for applying the assist force to the steering by the electric motor 110 can be easily changed according to the type of the vehicle on which the steering device 100 is mounted.

In addition, the steering assist current calculation unit 27 according to the present embodiment includes a steering situation determination unit 320 that determines the steering situation of the steering wheel 101, for example, whether the steering situation determination unit 320 determines, for example, right steering. The steering assist base current Irb and the correction current Ic are calculated based on whether the steering is left or the transition coefficient Ks is calculated. Therefore, the steering assist current Ir can be easily changed for each vehicle type by freely setting the predetermined value Nm0 defining the steering state for each vehicle type. As a result, it is possible to easily change the setting of the control for applying the assisting force to the rudder according to the type of the vehicle on which the steering device 100 is mounted.
Further, the steering assist current calculation unit 27 according to the present embodiment includes a torque noise cut unit 310, and uses the torque signal Td ′ from which noise is cut by the torque noise cut unit 310, and the steering assist base current Irb and Since the correction current Ic and the transition coefficient Ks are calculated, the steering auxiliary current Ir can be calculated with higher accuracy.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 21 ... Base current calculation part, 22 ... Inertia compensation current calculation part, 23 ... Damper compensation current calculation part, 25 ... Temporary target current determination part, 27 ... Steering auxiliary current calculation , 28 ... Final target current determination unit, 30 ... Control unit, 70 ... Motor rotation speed calculation unit, 100 ... Electric power steering device, 110 ... Electric motor

Claims (3)

An electric motor for providing an assisting force for an operation of a steering wheel provided in the vehicle;
Temporary target current determining means for determining a temporary value of a target current to be supplied to the electric motor based on a steering torque of the steering wheel and a vehicle speed of the vehicle;
A steering auxiliary current calculating means for calculating a steering auxiliary current which is an electric current for the electric motor to give an assist force according to a steering operation of the steering wheel;
Target current determining means for determining the target current based on the temporary value determined by the temporary target current determining means and the steering auxiliary current calculated by the steering auxiliary current calculating means;
An electric power steering apparatus comprising:   2. The electric power steering apparatus according to claim 1, wherein the steering auxiliary current calculating unit increases the absolute value of the steering auxiliary electric current as the steering time of the steering wheel is longer.   The steered auxiliary current calculating unit includes a steered direction determining unit that determines a steered direction, and calculates the steered auxiliary current based on the steered direction determined by the steered direction determining unit. The electric power steering apparatus according to claim 1 or 2.

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