JP2016041536A - Electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering apparatus capable of generating optimum steering assist power even when a vehicle turns right or left and eventually achieving the improvement of steering feeling.SOLUTION: A microcomputer 29 exerts a control to increase assist power if a direction indicator 51 indicates a right turn in a vehicle travel direction and an absolute value |dτ/dt| of a steering torque differential value calculated by a differentiator 35 is not smaller than a specified steering torque differential value τ0. With this configuration, it is possible to confirm that a steering wheel is turned if the direction indicator 51 indicates the right turn in the vehicle travel direction and the absolute value |dτ/dt| of the steering torque differential value calculated by the differentiator 35 is not smaller than the specified steering torque differential value τ0. Therefore, it is possible to increase the assist power and improve steering feeling.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electric power steering apparatus.

  In a conventional electric power steering device, a steering torque generated by a driver's steering wheel operation is detected by a steering torque sensor, the detected steering torque signal is converted into a target current signal, and the actual current that flows through the target current signal and the motor is actually detected. A deviation signal from the motor current signal corresponding to the current is subjected to PI (proportional / integral) or PID (proportional / integral / derivative) compensation, and a motor control signal (for example, generated based on this signal) , PWM signal) is known to drive a motor to apply a steering assist force to a steering system.

  Many of such conventional electric power steering devices increase or decrease the steering assist force according to the vehicle speed. That is, when the vehicle is stopped or running at a low speed, the friction resistance between the tire and the road surface is large, so a large steering assist force is applied to the steering mechanism, and when the vehicle is traveling at a high speed, the friction resistance between the tire and the road surface is small. The control structure is given to the steering mechanism.

  However, when the vehicle turns right or left, it is necessary to cut the handle greatly even when the vehicle speed is relatively high. Therefore, in the above control configuration, the steering assist force is small, and the steering feeling may be hindered. As a solution to this problem, in Patent Document 1, a vehicle is provided with a direction indicator, and the steering assist force is corrected to increase while the direction indicator is operating.

JP-A-11-301509

  However, in the above control configuration, since the actual incision of the steering wheel is not confirmed, for example, when the direction indicator breaks down or malfunctions, the steering assist force is corrected to increase more than necessary, and the steering feeling is increased. There was a problem of feeling uncomfortable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering device that generates an optimal steering assist force even when the vehicle turns right and left, and thus improves the steering feeling. It is to provide.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a steering force assisting device provided to apply an assist force for assisting a steering operation to a steering system by a motor, and a steering torque detection for detecting a steering torque. Means for calculating a change in the steering torque, vehicle direction indicating means for instructing the traveling direction of the vehicle, and driving for supplying driving power to the motor as a drive source of the steering force assisting device And a control means for controlling the drive means, wherein the control means instructs the vehicle direction indicating means to turn left or right in the traveling direction of the vehicle, and the steering When the absolute value of the steering torque differential value calculated by the torque differential calculation means is greater than or equal to a predetermined steering torque differential value, it is necessary to increase the assist force. To.

  According to the above configuration, the vehicle direction instructing unit instructs to turn left or right in the traveling direction of the vehicle, and the absolute value of the steering torque differential value calculated by the steering torque differential calculating unit that calculates the change in the steering torque. Is equal to or greater than a predetermined steering torque differential value, the actual incision of the steering wheel can be confirmed, so that the assist force can be increased and the steering feeling can be improved.

  The invention according to claim 2 further includes a yaw rate detecting means for detecting a yaw rate of the vehicle, wherein the control means is such that the vehicle direction indicating means instructs a right / left turn in the traveling direction of the vehicle, and When the absolute value of the steering torque differential value calculated by the steering torque differential calculation means is smaller than the predetermined steering torque differential value, the absolute value of the yaw rate detected from the yaw rate detection means is greater than or equal to the predetermined yaw rate. The gist is to increase the assist force.

  According to the above configuration, the vehicle direction instructing means instructs to turn left and right in the traveling direction of the vehicle, and the absolute value of the steering torque differential value calculated by the steering torque differential calculating means for calculating the change of the steering torque is calculated. Even when the value is smaller than a predetermined steering torque differential value, there is a case where the vehicle is turning right or left. Since it is detected by the yaw rate detection means, when the absolute value of the yaw rate is equal to or higher than the predetermined yaw rate, it can be confirmed that the vehicle is turning right or left, so that the assist force can be increased and the steering feeling can be improved. .

  According to the present invention, it is possible to provide an electric power steering apparatus that can generate an optimum steering assist force even when the vehicle turns right and left, and that can improve the steering feeling.

The schematic block diagram of the electric power steering apparatus (EPS) in this embodiment. The whole control block diagram of EPS in this embodiment. The 1st, 2nd, 3rd assist map figure in this embodiment. The flowchart figure which shows the process sequence of the assist electric current determination part in this embodiment.

Hereinafter, an embodiment of the present invention embodied in a column-type electric power steering apparatus (hereinafter referred to as EPS) will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. Has been changed.

  The EPS 1 also includes an EPS actuator 24 as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system using the motor 21 as a drive source, and an ECU 27 that controls the operation of the EPS actuator 24. Yes.

  The EPS actuator 24 of the present embodiment is a column type EPS actuator, and the motor 21 that is a drive source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 23. The rotation of the motor 21 is decelerated by the speed reduction mechanism 23 and transmitted to the column shaft 8 so that the motor torque is applied to the steering system as an assist force.

  On the other hand, the ECU 27 is connected with a vehicle speed sensor 25, a torque sensor 26 as a steering torque detecting means, and a motor rotation angle sensor 22, and the ECU 27 determines the vehicle speed V, the steering torque based on the output signals of these sensors. τ and motor rotation angle θm are detected. Further, the ECU 27 is connected to a yaw rate sensor 50 as a yaw rate detecting means and a direction indicator 51 as a vehicle direction indicating means via an in-vehicle network CAN 70. The ECU 27 outputs an output signal of each of these sensors. On the basis of the yaw rate γ and the direction indicator signal Sind.

  The torque sensor 26 is a twin resolver type torque sensor. The ECU 27 calculates a steering torque τ based on output signals from a pair of resolvers provided at both ends of a torsion bar (not shown). Further, the ECU 27 calculates a target assist force based on each of the detected state quantities, and assists the operation of the EPS actuator 24 through the supply of drive power to the motor 21 that is the drive source, that is, the assist that is given to the steering system. Control the power.

Next, an electrical configuration in the EPS 1 of the present embodiment will be described.
FIG. 2 is an overall control block diagram of the EPS 1 of the present embodiment. As shown in the figure, the ECU 27 is a microcomputer 29 as a control means for outputting a motor control signal, and a drive means for supplying drive power to the motor 21 as a drive source of the EPS actuator 24 based on the motor control signal. Drive circuit 41 and an actual current value detection sensor 30 for detecting an actual current value Iq energized to the motor 21.

  The drive circuit 41 is a known PWM inverter (not shown) formed by connecting two arms in parallel with a pair of switching elements connected in series as a basic unit (arm). Further, the motor control signal output from the microcomputer 29 defines the on-duty ratio of each switching element constituting the drive circuit 41. A motor control signal is applied to the gate terminal of each switching element, and in response to the motor control signal, each switching element is turned on / off to generate motor driving power based on the power supply voltage of the battery 28, and the motor 21. It is configured to output to.

  A motor rotation angle sensor 22 for detecting the motor rotation angle θm of the motor 21 is connected to the ECU 27. The microcomputer 29 detects the actual current value Iq of the motor 21 and the motor rotation angle θm, the steering torque τ, the vehicle speed V, the yaw rate γ, and the direction indicator signal Sind detected based on the output signals of these sensors. After the motor control signal is generated by the motor control signal output unit 40, the motor control signal is output to the drive circuit 41.

  Each control block shown below is realized by a computer program executed by the microcomputer 29. The microcomputer 29 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  As shown in FIG. 2, the microcomputer 29 includes a first assist force calculator 31, a second assist force calculator 32, and a third assist force calculator 33 that calculate an assist current command value Iq * for controlling the motor 21. And an assist current determination unit 34 for selecting which assist current to select. Further, the microcomputer 29 includes a motor control signal output unit 40 that generates a motor control signal from the assist current command value Iq * determined by the assist current determination unit 34.

  The microcomputer 29 executes current feedback control based on the assist current command value Iq *, the actual current value Iq detected by the actual current value detection sensor 30, and the motor rotation angle θm detected by the motor rotation angle sensor 22. To do. Then, the motor control signal output unit 40 generates a DUTY command value for determining the on / off timing of the FET constituting the drive circuit 41, and outputs a gate on / off signal based on the DUTY command value.

  The microcomputer 29 receives the vehicle speed V and the steering torque τ as inputs, outputs the first assist current command value Iq1 *, and inputs the steering torque differential value dτ / dt as a second assist current command. The second assist force calculating unit 32 that outputs the value Iq2 * and the third assist force calculating unit 33 that outputs the third assist current command value Iq3 * by using the yaw rate γ as an input.

  Further, the microcomputer 29 inputs the direction indicator signal Sind, the steering torque differential value dτ / dt, and the yaw rate γ, and selects the normal time map selection flag FLG1, the right / left turn map selection flag FLG2, and the right / left turn map selection. An assist current determination unit 34 that generates the flag FLG3 is included.

  Then, the microcomputer 29 selects the assist current command value Iq * based on the selection flag generated by the assist current determination unit 34. For example, when the normal time map selection flag FLG 1 is selected (turned on), the first assist current command value Iq 1 * is selected by the AND gate 36, and the motor control signal output unit 40 is connected via the subsequent OR gate 39. In addition, the first assist current command value Iq1 * is output as the assist current command value Iq *.

  When the right / left turn map selection flag FLG2 is selected (turned on), the second assist current command value Iq2 * is selected by the AND gate 37, and the motor control signal output unit is connected via the subsequent OR gate 39. 40, the second assist current command value Iq2 * is output as the assist current command value Iq *.

  Further, when the right / left turn map selection flag FLG3 is selected (turned on), the third assist current command value Iq3 * is selected by the AND gate 38, and the motor control signal output unit via the rear OR gate 39 is selected. 40, the third assist current command value Iq3 * is output as the assist current command value Iq *.

Next, the first assist force calculation unit 31, the second assist force calculation unit 32, and the third assist force calculation unit 33 of the present embodiment will be described based on FIGS. 3 (a), 3 (b), and 3 (c). explain.
As shown in FIG. 3A, the first assist force calculation unit 31 has a first assist force map 31a. In the first assist force map 31a, the horizontal axis represents the steering torque τ, the vertical axis represents the first assist current command value Iq1 *, and the vehicle speed V as parameters. The first assist force map 31a outputs a larger first assist current command value Iq1 * as the steering torque τ increases. However, in the case of the same steering torque τ, the first assist current command value Iq1 * is increased as the vehicle speed V decreases.

  Next, as shown in FIG. 3B, the second assist force calculation unit 32 has a second assist force map 32a. In the second assist force map 32a, the horizontal axis represents the steering torque differential value dτ / dt, and the vertical axis represents the second assist current command value Iq2 *. The second assist force map 32a is configured to greatly increase the second assist current command value Iq2 * when the absolute value of the steering torque differential value dτ / dt is larger than a predetermined steering torque differential value τ0.

  Next, as shown in FIG. 3C, the third assist force calculating unit 33 has a third assist force map 33a. In the third assist force map 33a, the horizontal axis represents the yaw rate γ, and the vertical axis represents the third assist current command value Iq3 *. The third assist force map 33a is configured to greatly increase the third assist current command value Iq3 * when the absolute value of the yaw rate γ is greater than a predetermined yaw rate γ0.

Next, the processing procedure of the assist current determination part 34 by the microcomputer 29 of this embodiment is demonstrated based on FIG.
First, the microcomputer 29 reads the direction indicator signal Sind (step S101). Next, the microcomputer 29 reads the steering torque τ (step S102). Then, the microcomputer 29 calculates the steering torque differential value dτ / dt by performing the differential calculation of the steering torque τ by the differentiator 35 which is a steering torque differential calculation means for calculating the change of the steering torque (step S103). Further, the microcomputer 29 reads the yaw rate γ (step S104).

  Next, the microcomputer 29 determines whether or not the direction indicator signal Sind is on (step S105). When the direction indicator signal Sind is on (step S105: YES), the microcomputer 29 determines whether or not the absolute value of the steering torque differential value dτ / dt is equal to or greater than a predetermined steering torque differential value τ0. (Step S106).

  If the absolute value of the steering torque differential value dτ / dt is greater than or equal to the predetermined steering torque differential value τ0 (step S106: YES), the microcomputer 29 sets the right / left turn map selection flag FLG2 (FLG2 = “1”, step S107). Then, the microcomputer 29 sets the second assist current command value Iq2 * to the assist current command value Iq * (Iq * ← Iq2 *, step S108). Then, the microcomputer 29 outputs the assist current command value Iq * to the motor control signal output unit 40 (step S109), and ends the process.

  On the other hand, when the absolute value of the steering torque differential value dτ / dt is smaller than the predetermined steering torque differential value τ0 (step S106: NO), the microcomputer 29 determines whether the absolute value of the yaw rate γ is equal to or greater than the predetermined yaw rate γ0. Is determined (step S110). When the absolute value of the yaw rate γ is equal to or greater than the predetermined yaw rate γ0 (step S110: YES), the microcomputer 29 sets the map selection flag FLG3 when turning right or left (FLG3 = “1”, step S111).

  Then, the microcomputer 29 sets the third assist current command value Iq3 * to the assist current command value Iq * (Iq * ← Iq3 *, step S112). Then, the microcomputer 29 outputs the assist current command value Iq * to the motor control signal output unit 40 (step S109), and ends the process.

  On the other hand, when the absolute value of the yaw rate γ is smaller than the predetermined yaw rate γ0 (step S110: NO), the microcomputer 29 sets the normal time map selection flag FLG1 (FLG1 = “1”, step S113). Then, the microcomputer 29 sets the first assist current command value Iq1 * to the assist current command value Iq * (Iq * ← Iq1 *, step S114).

  Then, the microcomputer 29 outputs the assist current command value Iq * to the motor control signal output unit 40 (step S109), and ends the process. Further, when the direction indicator signal Sind is not on (step S105: NO), the microcomputer 29 proceeds to step S113.

Next, the operation and effect of the EPS 1 of the present embodiment configured as described above will be described.
The microcomputer 29 instructs the direction indicator 51 to turn left or right in the vehicle traveling direction, and the absolute value | dτ / dt | of the steering torque differential value calculated by the differentiator 35 is a predetermined steering torque differential. When the value τ0 or more, the assist force is increased.

  According to the above configuration, the direction indicator 51 instructs to turn left and right in the vehicle traveling direction, and the absolute value | dτ / dt | of the steering torque differential value calculated by the differentiator 35 is a predetermined steering. When the torque differential value τ0 or more, since the steering of the steering wheel can be confirmed, the assist force can be increased and the steering feeling can be improved.

  The microcomputer 29 further includes a yaw rate sensor 50 for detecting the yaw rate γ of the vehicle. The microcomputer 29 instructs the direction indicator 51 to turn left or right in the vehicle traveling direction, and the steering torque calculated by the differentiator 35. When the absolute value | dτ / dt | of the differential value is smaller than the predetermined steering torque differential value τ0, the assist force is applied when the absolute value of the yaw rate γ detected from the yaw rate sensor 50 is equal to or greater than the predetermined yaw rate γ0. Increased configuration.

  According to the above configuration, the direction indicator 51 instructs to turn left and right in the vehicle traveling direction, and the absolute value | dτ / dt | of the steering torque differential value calculated by the differentiator 35 is a predetermined steering. Even if it is smaller than the torque differential value τ0, there is a case where the vehicle is turning right or left, and this is detected by the yaw rate sensor 50. That is, when the absolute value of the yaw rate γ is equal to or greater than the predetermined yaw rate γ0, it can be confirmed that the vehicle is turning right or left, so that the assist force can be increased and the steering feeling can be improved.

In addition, you may change this embodiment as follows.
In the present embodiment, the first assist force calculation unit 31, the second assist force calculation unit 32, and the third assist force calculation unit 33 are each configured with a map, but each is configured with a function related to an element on the horizontal axis. May be.

In the present embodiment, the yaw rate sensor is used to confirm that the vehicle is turning right or left, but the steering status of the vehicle may be grasped by GPS.

In the present embodiment, the motor that assists the assist force is a DC motor, but the present invention may be applied to a brushless DC motor or a VR motor.

In the present embodiment, the present invention is embodied in the column assist EPS, but the present invention may be applied to a rack assist EPS, a pinion assist EPS, a rack parallel EPS, and the like.

1: Electric power steering device (EPS), 2: Steering,
3: Steering shaft, 4: Rack and pinion mechanism, 5: Rack shaft,
8: column shaft, 9: intermediate shaft, 10: pinion shaft, 11: tie rod, 12: steered wheel, 21: motor, 22: motor rotation angle sensor,
23: Deceleration mechanism, 24: EPS actuator (steering force assist device),
25: Vehicle speed sensor, 26: Torque sensor (steering torque detection means), 27: ECU,
28: battery, 29: microcomputer (control means), 30: actual current value detection sensor,
31: 1st assist force calculating part, 31a: 1st assist force map,
32: second assist force calculation unit, 32a: second assist force map,
33: third assist force calculation unit, 33a: third assist force map,
34: assist current determination unit, 35: differentiator (steering torque differential calculation means),
36, 37, 38: AND GATE, 39: OR GATE,
40: motor control signal output unit, 41: drive circuit (drive means),
50: Yaw rate sensor (yaw rate detection means),
51: Direction indicator (vehicle direction indication means),
70: In-vehicle network (CAN),
V: vehicle speed, τ: steering torque, τ0: predetermined steering torque differential value,
dτ / dt: Steering torque differential value, θm: Motor rotation angle,
γ: yaw rate, γ0: predetermined yaw rate,
Iq *: assist current command value,
Iq1 *: first assist current command value,
Iq2 *: second assist current command value,
Iq3 *: third assist current command value,
Iq: actual current value,
Sind: Direction indicator signal,
FLG1: normal time map selection flag,
FLG2: Map selection flag when turning left or right,
FLG3: Map selection flag when turning left or right,

Claims (2)

A steering force assisting device provided to apply an assisting force to assist the steering operation to the steering system by the motor;
Steering torque detection means for detecting steering torque;
Steering torque differential calculation means for calculating a change in the steering torque;
Vehicle direction indicating means for instructing the traveling direction of the vehicle;
Drive means for supplying drive power to the motor which is a drive source of the steering force assisting device;
In an electric power steering apparatus comprising control means for controlling the drive means,
The control means instructs the vehicle direction indicating means to turn left or right in the traveling direction of the vehicle, and the absolute value of the steering torque differential value calculated by the steering torque differential calculation means is a predetermined steering torque. If it is greater than or equal to the differential value, increasing the assist force;
An electric power steering device. A yaw rate detecting means for detecting the yaw rate of the vehicle;
The control means instructs the vehicle direction indicating means to turn left or right in the traveling direction of the vehicle, and the absolute value of the steering torque differential value calculated by the steering torque differential calculation means is a predetermined steering torque. If the differential value is smaller than the differential value, if the absolute value of the yaw rate detected by the yaw rate detection means is greater than or equal to a predetermined yaw rate, increasing the assist force;
The electric power steering apparatus according to claim 1.

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