JP2013237316A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device with good steering feeling by accurately detecting the degree of accumulation of fatigue of a driver.SOLUTION: When a steering state determination means determines that a steering state is in a state other than a holding steering state, the absolute value of the steering torque of a vehicle is integrated, and an integration time is measured. When the measured integration time is equal to or longer than a predetermined time, and the integration value of the absolute values of the steering torque is equal to or higher than a predetermined value, the steering torque is increased by a predetermined amount. When it is determined that a signal from the steering state determination means is in a holding steering state, a holding steering time is measured. When the measured holding steering time is equal to or longer than a predetermined time, the steering torque increased by a predetermined time is decreased by a predetermined amount.

Description

  The present invention relates to an electric power steering apparatus.

  Conventionally, an electric power steering apparatus generates a motor current command value from a steering torque and a vehicle speed, and a current deviation value between the motor current command value and a motor actual current value flowing through an assist motor is controlled by PID control (proportional / integral / An assist force is generated by configuring a current feedback control system that performs differential compensation. This assist force reduces the driver's labor for steering and achieves a comfortable steering feeling.

In the electric power steering device described in Patent Document 1, it is proposed to detect the continuous running time of the vehicle and change the assist force according to the detected continuous running time.
Therefore, it is possible to perform steering assist in consideration of driver fatigue caused by driving the vehicle continuously for a long time, and to achieve comfortable steering without giving the driver a sense of incongruity. ing.

Japanese Patent Laid-Open No. 2004-217047

  However, in the above-described method, the continuous running time of the vehicle is simply detected, and the assist force is changed according to the detected continuous running time, so the driver's steering state is not taken into consideration. For example, when the driver frequently cuts and returns repeatedly, the driver's fatigue accumulation is large. If this point is not taken into account, there are cases in which it is not possible to sufficiently achieve comfortable steering without giving the driver a sense of incongruity.

  An object of the present invention is to provide an electric power steering device that accurately captures the accumulated degree of driver fatigue and has a good steering feeling.

  In order to solve the above problem, the invention according to claim 1 detects a steering state determining means for determining a steering state of the vehicle, a motor for generating an assist force for assisting a steering operation, and a steering torque. Steering torque detection means, and control means for controlling the operation of the motor. The control means determines the absolute value of the steering torque of the vehicle when the steering state determination means determines that the vehicle is not in the steered state. Summing up, measuring the integration time, and increasing the steering torque by a predetermined amount when the integration measurement time exceeds a predetermined time and the integrated value of the absolute value of the steering torque exceeds a predetermined value And

  In the electric power steering apparatus according to the present invention, when the steering state determining means determines that the vehicle is not in the steered state, the absolute value of the steering torque of the vehicle is integrated, the integrated time is measured, and the integrated measurement time is a predetermined time. As described above, when the integrated value of the absolute value of the steering torque becomes a predetermined value or more, the steering torque is increased by a predetermined amount.

As a result, when the turning or turning back steering is continued, the integrated value of the absolute value of the steering torque of the vehicle becomes large, and it can be determined that the driver has accumulated much fatigue.
When the integrated value of the absolute value of the steering torque of the vehicle is large, a predetermined amount of steering torque is added to the steering torque detected by the steering torque sensor, so that the assist amount increases and the driver's fatigue is increased. The steering feeling can be improved.

  According to a second aspect of the present invention, the control means measures the holding time when the signal from the steering state determination means is determined to be the holding state, and the holding measurement time becomes a predetermined time or more. In this case, the gist is that the steering torque increased by the predetermined amount is decreased by the predetermined amount.

  According to the above configuration, when the signal from the steering state determination means is determined to be the steered state, the steered time is measured, and when the steered measured time exceeds the predetermined time, the predetermined amount is increased. The steering torque is reduced by a predetermined amount.

  As a result, if the steering state is maintained sufficiently and the driver's fatigue is reduced, the amount of assist is reduced, resulting in a slightly heavier steering feeling, and the slipping when turning or turning back is performed. The feeling is lost and the steering feeling can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the accumulation degree of a driver | operator's fatigue | exhaustion can be caught exactly and the electric power steering apparatus with a favorable steering feeling can be provided.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. The flowchart which shows the process sequence of a steering state determination part. The flowchart which shows the process sequence of an assist torque calculating part.

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, a vehicle speed sensor 25, a torque sensor 26, and a motor rotation angle sensor 22 are connected to the ECU 27. The ECU 27 is based on the output signals of these sensors, and the vehicle speed V, the steering torque τ, and the motor rotation angle. θm is detected.

  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 a control block diagram of the EPS 1 of the present embodiment. As shown in the figure, the ECU 27 includes a microcomputer 29 that outputs a motor control signal, a motor drive circuit 40 that supplies drive power to the motor 21 that is a drive source of the EPS actuator 24 based on the motor control signal, and And a motor current detector 41 for detecting a motor actual current value Im supplied to the motor 21.

  The motor drive circuit 40 is a known H bridge circuit (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 motor drive circuit 40. 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. Then, the microcomputer 29 determines the motor based on the motor rotation angle θm of the motor 21 detected based on the output signals of these sensors, the motor actual current value Im supplied to the motor 21, and the steering torque τ and the vehicle speed V. A motor control signal is output to the drive circuit 40.

  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 current command value calculation unit 30 that calculates a motor current command value I * for controlling the motor 21, and a motor control signal that generates a motor control signal for controlling the motor drive circuit 40. A generation unit 44, a steering state determination unit 38 that generates a steering-holding confirmation flag FLG, and an assist torque calculation unit 39 that generates an assist torque τasist are provided.

  The steering torque τ detected by the torque sensor 26 is added to the assist torque τasist output from the assist torque calculator 39 and added to the adder 32 and then input to the current command value calculator 30 as a combined steering torque τg. . Further, the vehicle speed V detected by the vehicle speed sensor 25 is also input to the current command value calculation unit 30. The current command value calculation unit 30 is a map (not shown) configured with the combined steering torque τg on the horizontal axis and the motor current command value I * on the vertical axis. In the above map, when the vehicle speed V is a parameter and the same combined steering torque τg, the motor current command value I * increases as the vehicle speed V decreases.

  The motor control signal generation unit 44 inputs the motor current command value I * calculated by the current command value calculation unit 30 and the motor actual current value Im detected from the motor current detector 41. The motor control signal generation unit 44 includes the input state quantities (I *, Im), a subtractor 35, a PID control unit (proportional / integral / differential compensation) 33, and a PWM output unit 37. A feedback control unit is configured.

The steering state determination unit 38 that generates the steering holding confirmation flag FLG includes the state quantity after the motor rotation angle θm of the motor 21 is differentiated by the differentiator 31, the motor rotation angular velocity ωm, the motor actual current value Im, the steering Torque τ is input. The steering state determination unit 38 determines whether the steering state is the steering holding state or other than the steering holding state based on the input state quantities (ωm, Im, τ).
When the steering state is determined to be the steering holding state, the steering holding confirmation flag FLG is set (FLG = “1”), and when the steering state is determined to be other than the steering holding state, the steering is being held. The confirmation flag FLG is reset (FLG = “0”), and the steering-holding confirmation flag FLG is output to the assist torque calculator 39 at the subsequent stage.

  A steering hold confirmation flag FLG and a steering torque τ are input to the assist torque calculator 39 that generates the assist torque τasist. When the steering holding confirmation flag FLG is reset (FLG = “0”), the assist torque calculating unit 39 determines that the steering state is other than the steering holding state, that is, turning and turning back, and is input. The steering torque τ is accumulated. If the integrated value is equal to or greater than the predetermined torque integrated value τmax after the predetermined time has elapsed, it is determined that the driver's fatigue has accumulated significantly, and the assist torque τasist is calculated.

  The assist torque τasist is added to the steering torque τ by the adder 32 to generate a combined steering torque τg, which is input to the current command value calculation unit 30. As described above, the current command value calculation unit 30 is a map (not shown) composed of the combined steering torque τg on the horizontal axis and the motor current command value I * on the vertical axis, so the combined steering torque τg is large. As the motor current command value I * increases, the driver's fatigue accumulation is reduced.

Next, a processing procedure of the steering state determination unit 38 by the microcomputer 29 of the present embodiment will be described based on FIG.
First, the microcomputer 29 reads the motor rotation angle θm (step S101). The microcomputer 29 calculates the motor rotation angular velocity ωm by differentiating the read motor rotation angle θm (ωm = dθm / dt, step S102). Next, the microcomputer 29 reads the motor current command value I * (step S103). Further, the microcomputer 29 reads the steering torque τ (step S104).

  Next, the microcomputer 29 determines whether or not the absolute value of the motor current command value I * is equal to or less than a predetermined motor current value I0 (step S105). When the absolute value of the motor current command value I * is equal to or less than the predetermined motor current value I0 (I * ≦ I0, step S105: YES), the microcomputer 29 determines that the absolute value of the steering torque τ is Then, it is determined whether or not the steering torque is equal to or less than a predetermined value τ0 (step S106). When the absolute value of the steering torque τ is equal to or smaller than the steering torque predetermined value τ0 (τ ≦ τ0, step S106: YES), the microcomputer 29 determines that the absolute value of the motor rotation angular velocity ωm is the motor rotation. It is determined whether or not the angular velocity is a predetermined value ωm0 or less (step S107).

  When the motor rotation angular velocity ωm is equal to or smaller than the motor rotation angular velocity predetermined value ωm0 (ωm ≦ ωm0, step S107: YES), the microcomputer 29 determines that the steering state is the steering holding state, The steered state time measurement timer Th is incremented (Th = Th + 1, step S108). Further, the microcomputer 29 determines whether or not the steered state time measurement timer Th is equal to or greater than the steered state time fixed value Th0 (Th ≧ Th0, step S109).

  Then, the microcomputer 29 sets the steering-holding confirmation flag FLG when the steering-holding state time measurement timer Th is equal to or larger than the steering-holding state time fixed value Th0 (Th ≧ Th0, step S109: YES) (FLG = “1”, step S110). Then, the microcomputer 29 outputs a steering hold confirmation flag FLG to the assist torque calculation unit 39 (step S111), and the process ends. Furthermore, the microcomputer 29 returns to Step 101 when the steered state time measurement timer Th is smaller than the steered state time fixed value Th0 (Th <Th0, Step S109: NO).

  On the other hand, the microcomputer 29 determines that the absolute value of the motor current command value I * is larger than the predetermined motor current value I0 (| I * |> I0, step S105: NO), or the absolute value of the steering torque τ is the predetermined steering torque. When the value is larger than τ0 (| τ |> τ0, step S106: NO), or when the absolute value of the motor rotational angular velocity ωm is larger than the predetermined motor rotational angular velocity ωm0 (| ωm |> ωm0, step S107: NO). Moves to step S112.

  In step S112, the microcomputer 29 determines that the steering state is other than the steered state, and increments the time measurement timer Td other than the steered state (Td = Td + 1, step S112). Further, the microcomputer 29 determines whether or not the time measurement timer Td other than the steered state is equal to or greater than the time determined value Td0 other than the steered state (Td ≧ Td0, step S113).

  Then, when the time measurement timer Td other than the steered state is equal to or greater than the time determined value Td0 other than the steered state (Td ≧ Td0, step S113: YES), the microcomputer 29 resets the steered confirmation flag FLG ( FLG = "0", step S114). Then, the microcomputer 29 outputs a steering hold confirmation flag FLG to the assist torque calculation unit 39 (step S111), and the process ends. Further, the microcomputer 29 returns to Step 101 when the time measurement timer Td other than the steered state is smaller than the time fixed value Td0 other than the steered state (Td <Td0, Step S113: NO).

Next, a processing procedure of the assist torque calculation unit 39 by the microcomputer 29 of the present embodiment will be described based on FIG.
First, the microcomputer 29 determines whether or not the steering holding confirmation flag FLG is “1” (step S201). When the steering holding confirmation flag FLG is not “1” (FLG = “0”, step S201: NO), the microcomputer 29 reads the steering torque τ (step S202). Next, the microcomputer 29 reads the accumulated torque τsum (step S203). Then, the microcomputer 29 adds the absolute value of the steering torque τ to the integrated torque τsum (τsum = τsum + | τ |, step S204). Further, the microcomputer 29 increments the steering torque integration time measurement timer Ts (Ts = Ts + 1, step S205). Further, the microcomputer 29 determines whether or not the steering torque integration time measurement timer Ts is equal to or greater than the steering torque integration time fixed value Ts0 (Ts ≧ Ts0, step S206).

When the steering torque integration time measurement timer Ts is equal to or greater than the steering torque integration time fixed value Ts0 (Ts ≧ Ts0, Step S206: YES), the microcomputer 29 determines whether the integration torque τsum is equal to or greater than the predetermined torque integration value τmax. Is determined (step S207).
When the integrated torque τsum is equal to or greater than the predetermined torque integrated value τmax (τsum ≧ τmax, step S207: YES), the microcomputer 29 calculates the assist torque τasist by dividing the integrated torque τsum by the constant α ( Step S208). The constant α is obtained from experimental values of actual vehicles. Then, the microcomputer 29 outputs the assist torque τasist to the adder 32 (step S209) and finishes the process.

  On the other hand, when the integrated torque τsum is smaller than the predetermined torque integrated value τmax (τsum <τmax, step S207: NO), the microcomputer 29 resets the steering torque integrated time measurement timer Ts (Ts ← “0”, step S212). Then, the holding state time measurement timer Tr is reset (Tr ← “0”, Step S213), the accumulated torque τsum is zero (τsum ← “0”, Step S214), and the assist torque τasist is zero (τasist ← “0”). Step S215). Then, the microcomputer 29 outputs the assist torque τasist to the adder 32 (step S209) and finishes the process.

  On the other hand, when the steering holding confirmation flag FLG is “1” (FLG = “1”, step S201: YES), the microcomputer 29 increments the steering holding state time measurement timer Tr (Tr = Tr + 1, Step S210). Furthermore, the microcomputer 29 determines whether or not the steered state time measurement timer Tr is equal to or greater than the steered state time fixed value Tr0 (step S211).

  Then, the microcomputer 29 sets the steering torque integration time measurement timer Ts when the steered state time measurement timer Tr is equal to or greater than the steered state time determination value Tr0 (Tr ≧ Tr0, step S211: YES). Reset (Ts ← “0”, step S212), reset the holding state time measurement timer Tr (Tr ← “0”, step S213), zero the accumulated torque τsum (τsum ← “0”, step S214), and assist The torque τasist is set to zero (τasist ← “0”, step S215).

  Then, the microcomputer 29 outputs the assist torque τasist to the adder 32 (step S209) and finishes the process. On the other hand, the microcomputer 29 returns to step S201 when the steered state time measurement timer Tr is smaller than the steered state time fixed value Tr0 (Tr <Tr0, step S211: NO).

Next, the operation and effect of the EPS 1 of the present embodiment configured as described above will be described.
In the EPS 1 of the present embodiment, when the steering state determination unit determines that the vehicle is not in the steered state, the absolute value of the steering torque of the vehicle is integrated, the integrated time is measured, and the integrated measurement time is equal to or longer than a predetermined time. When the integrated value of the absolute value of the steering torque exceeds a predetermined value, the steering torque is increased by a predetermined amount.

  As a result, when the infeed or the inversion steering is continuously performed, the integrated value of the absolute value of the steering torque of the vehicle becomes large, and it can be determined that the driver has accumulated much fatigue. When the integrated value of the absolute value of the steering torque of the vehicle is large, a predetermined amount of steering torque is added to the steering torque detected by the steering torque sensor, so that the assist amount increases and the driver's fatigue is increased. The steering feeling can be improved.

  Further, in the EPS 1 of the present embodiment, when the signal from the steering state determining means is determined to be the steered state, the steered time is measured, and when the steered measured time exceeds a predetermined time, The steering torque increased by a fixed amount is reduced by a predetermined amount.

  As a result, when the steering holding state continues for a predetermined time and the driver's fatigue is reduced, the amount of assist is reduced, so there is no sense of slipping when turning or turning back, and the steering feeling is reduced. Improvements can be made.

In addition, you may change this embodiment as follows.
In the present embodiment, the absolute value of the steering torque of the vehicle is integrated by determining whether the steering is in the holding state or other than the holding state, and the steering torque is increased by a predetermined amount. However, the vehicle speed is high or low. Moreover, the determination may be made in addition to the steering conditions.

-In this embodiment, the absolute value of the steering torque of the vehicle is integrated by determining whether it is in the steered state or not in the steered state, and the steering torque is increased by a predetermined amount. It may be increased.

In the present embodiment, the motor is described as a DC motor, but the motor may be a brushless DC 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 or a pinion assist EPS.

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, 25: Vehicle speed sensor,
26: torque sensor (steering torque detection means), 27: ECU, 28: battery,
29: Microcomputer (control means), 30: Current command value calculation unit, 31: Differentiator,
32: Adder, 33: PID control unit (proportional / integral / derivative compensation), 35: Subtractor,
37: PWM output unit, 38: Steering state determination unit (steering state determination unit),
39: Assist torque calculation unit, 40: Motor drive circuit, 41: Motor current detection unit,
44: Motor control signal generator,
V: vehicle speed, τ: steering torque, τasist: assist torque, τg: combined steering torque,
τmax: predetermined torque integrated value, τsum: integrated torque,
θm: Motor rotation angle, ωm: Motor rotation angular velocity,
I *: Motor current command value, Im: Motor actual current value,
I0: motor current predetermined value, τ0: steering torque predetermined value, ωm0: motor rotation angular velocity predetermined value,
FLG: Steering check flag,
Th: Steering state time measurement timer, Th0: Steering state time fixed value,
Td: Time measurement timer other than the steered state, Td0: Time determined value other than the steered state
Ts: Steering torque integration time measurement timer, Ts0: Steering torque integration time fixed value,
Tr: Steering state time measurement timer, Tr0: Steering state time fixed value,
α: Constant

Claims (2)

Steering state determination means for determining the steering state of the vehicle;
A motor for generating assist force to assist steering operation;
Steering torque detection means for detecting steering torque;
Control means for controlling the operation of the motor,
The control means integrates the absolute value of the steering torque of the vehicle and measures the accumulated time when the steering state determining means determines that the vehicle is not in the steered state, and the accumulated measurement time is not less than a predetermined time, and When the integrated value of the absolute value of the steering torque is equal to or greater than a predetermined value, the steering torque is increased by a predetermined amount;
Electric power steering device characterized by The control means measures the holding time when the signal from the steering state determination means is determined to be in the steered state, and increases the predetermined amount when the steered measurement time exceeds a predetermined time. Reducing the predetermined steering torque by the predetermined amount,
The electric power steering apparatus according to claim 1.

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