JP2013018381A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of optimizing control corresponding to a steering quantity from the midpoint of a steering wheel, by accurately setting the midpoint.SOLUTION: A variation detecting part learns the fact that an absolute value of a detecting value of a plurality of variation detecting parts including a yaw rate sensor falls within a predetermined range and an absolute value of this time value of the detecting value of the yaw rate sensor is smaller than an absolute value of the last rime value, as a learning condition. When satisfying the learning condition, a detecting steering quantity at that time is set as the set midpoint.

Description

  The present invention relates to an electric power steering apparatus that controls a steering assist torque generating actuator according to a steering amount from a middle point of a steering wheel.

When the steering assist torque generating actuator is controlled according to the steering amount from the middle point of the steering wheel, if the middle point is inaccurate, the traveling direction of the vehicle may be biased.
Therefore, the relative detected steering amount of the steering wheel when the detected steering torque by the torque sensor is zero is set as the midpoint.

  However, when the vehicle is driving on a bank road, if the driver releases his hand from the steering wheel, the steering torque is zero, but the vehicle cannot go straight. The midpoint cannot be determined accurately. Therefore, based on the detected values of the yaw rate and lateral acceleration of the vehicle, when they are within the straight travel determination range, it is determined that the vehicle is in the straight travel state, and the relative detected steering angle when the vehicle is in the straight travel state It has been proposed to set the position as a midpoint (see Patent Document 1).

JP 2003-118616 A

However, if it is determined that the vehicle is in the straight traveling state when the plurality of vehicle straight traveling state detection values are within the straight traveling determination range, the straight traveling determination value is used even after the plurality of vehicle straight traveling state detection values become zero. The detected rudder angle position is set as the midpoint until it is out of range.
As a result, an error occurs at the midpoint of the steering wheel, and the optimization of the control according to the steering amount from the midpoint may be reduced. In this respect, there was still room for improvement.

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to control the control according to the steering amount from the middle point, particularly by setting the middle point of the steering wheel accurately. An object is to provide an electric power steering device that can be optimized.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a torque sensor (11) for detecting a steering torque of the steering wheel (1) and an actuator (10) for generating a steering assist torque corresponding to the detected steering torque. ), A steering amount sensor (12) that detects a relative steering amount of the steering wheel (1) with respect to the setting midpoint, a midpoint storage unit (20) that stores the setting midpoint of the steering amount, and a vehicle A plurality of variable detectors (20) including a yaw rate sensor (13) that detects a variable that changes in accordance with the traveling direction of the motor at a predetermined cycle, and a controller (20) that controls the actuator, the control The unit (20) has an absolute value of the detection values of the plurality of variable detection units (20) within a predetermined range, and an absolute value of the current value of the detection value of the yaw rate sensor (13) is the previous value. When the learning condition of less than the pair value is satisfied, the detected steering amount at that time is stored as a setting midpoint in the midpoint storage unit (20), and according to the detected steering amount from the set setting midpoint The gist is to control the actuator (10).

  According to the present invention, the absolute values of the detected values of the plurality of variable detectors including the yaw rate sensor are within a predetermined range, and the absolute value of the current value of the detected value of the yaw rate sensor is smaller than the absolute value of the previous value. When the learning condition is satisfied, the detected steering amount at that time is stored as a setting midpoint. That is, since the absolute values of the detection values of the plurality of variable detection units including the yaw rate sensor are within a predetermined range, it is determined that the vehicle is in a substantially straight traveling state.

Furthermore, among the plurality of variable quantity detection units, the yaw rate sensor performs zero point correction each time the vehicle stops, so that the variable detection accuracy is particularly high. Focusing on the yaw rate sensor with high variable detection accuracy, and further when the learning condition that the absolute value of the current value of the detected value of the yaw rate sensor is smaller than the absolute value of the previous value is satisfied, the detected steering amount at that time is The set midpoint is stored in the midpoint storage unit. Therefore, it is possible to prevent the midpoint of the steering wheel from being specified incorrectly.
As a result, it is possible to optimize the control according to the steering amount from the midpoint.

  The gist of the invention described in claim 2 is that the control unit sets a further learning condition that the absolute value of the current value of the steering amount sensor is smaller than the absolute value of the previous value.

According to the above configuration, the control unit sets the further learning condition that the absolute value of the current value of the steering amount sensor is smaller than the absolute value of the previous value. Therefore, since the midpoint learning is performed only when the variable amount detection unit and the steering amount sensor satisfy a plurality of conditions, midpoint learning with higher accuracy and higher accuracy is possible.
As a result, it is possible to more strictly optimize the control according to the steering amount from the midpoint.

  According to the electric power steering apparatus of the present invention, by appropriately setting the middle point of the steering wheel, it is possible to optimize the control according to the steering amount from the middle point.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing of the electric power steering apparatus of embodiment of this invention. The flowchart which shows the control procedure of the actuator in the electric power steering apparatus of embodiment of this invention. An example of the shift state of the yaw rate in the electric power steering device of the embodiment of the present invention. An example of the shift state of the lateral acceleration in the electric power steering device of the embodiment of the present invention. An example of the shift state of the left-right wheel speed difference at the time of front-wheel drive in the electric power steering apparatus of embodiment of this invention. An example of the shift state of the right-and-left wheel speed difference at the time of the rear-wheel drive in the electric power steering device of embodiment of this invention. An example of the shift state of the steering angle in the electric power steering apparatus of the embodiment of the present invention. The flowchart which shows the midpoint setting procedure in the electric power steering apparatus of embodiment of this invention.

In the electric power steering apparatus A of the vehicle 100 shown in FIG. 1, a pinion 4 is connected to a steering shaft 2 coupled to a steering wheel 1 via a universal joint 3, and left and right at each end of a rack 5 meshing with the pinion 4. A front wheel 6f is connected via a tie rod 7, a knuckle arm 8, and the like. Thereby, the rotation of the steering wheel 1 by steering is transmitted to the pinion 4, the rack 5 moves in the vehicle width direction, and the movement of the rack 5 is transmitted to the wheels 6 f, thereby changing the steering angle. .
Further, a steering assist torque generating actuator 10 constituted by an electric motor is connected to the steering shaft 2 via a reduction gear mechanism 9. The output of the actuator 10 is transmitted to the steering shaft 2 via the reduction gear mechanism 9 so that steering assist torque is applied.

  A braking mechanism is provided for the left and right rear wheels 6r driven by the left and right front wheels 6f and the engine 40 via a transmission gear mechanism, a differential gear mechanism, and the like. That is, the braking mechanism includes a master cylinder 52 that generates a braking pressure for each wheel 6f and 6r according to the depressing force of the brake pedal 51, a braking pressure control unit 50 that amplifies the braking pressure, and a brake for each wheel 6f and 6r. A braking force is applied to each of the wheels 6f and 6r by being distributed as wheel cylinder pressure that presses the brake shoe in the device 54 against the brake drum.

The steering assist torque generating actuator 10, an engine control device such as an electric valve for controlling the engine 40, and the braking pressure control unit 50 are connected to a control device 20 configured by a computer. The control device 20 includes a torque sensor 11 that detects a steering torque τ of the steering shaft 2, a steering amount sensor 12 that detects a steering angle θ corresponding to the rotation angle of the steering shaft 2 as a relative steering amount of the steering wheel 1, and a yaw rate. A yaw rate sensor 13 for detecting γ, a lateral acceleration sensor 14 for detecting lateral acceleration Gy, a wheel speed sensor 15 for detecting the respective wheel speeds 6f and 6r, and a vehicle speed sensor 16 for detecting the vehicle speed V are connected.
Since the yaw rate γ, the lateral acceleration Gy, and the left and right wheel speed difference are variables that change when the traveling direction of the vehicle 100 changes, they are detected by the yaw rate sensor 13, the lateral acceleration sensor 14, the wheel speed sensors 15, and the wheel speed sensor 15. The control device 20 that calculates the difference between the left and right wheel speeds from the wheel speeds of the respective wheels 6f constitutes a variable amount detection unit of the present invention.

  The control device 20 functions as a control unit that controls the actuator 10 and controls the actuator 10 so as to generate a steering assist torque corresponding to the detected steering torque τ. Further, in the present embodiment, the control device 20 also responds to the detected vehicle speed V. The steering assist torque is changed, and the steering assist torque is increased as the magnitude of the steering torque τ increases and the vehicle speed V decreases.

  In addition, the control device 20 that functions as a control unit of the actuator 10 controls the actuator 10 according to the detected steering angle θh from the set middle point of the steering wheel 1. For example, when the magnitude of the detected steering angle θh from the middle point is equal to or smaller than the set value, the straight line travel stability is controlled by controlling the actuator 10 so that the steering assist torque is not generated even if the steering torque τ increases. When the steering angle θh from the midpoint decreases or the steering angle θh from the midpoint decreases, the steering assist torque is changed according to the steering angle θh from the midpoint, thereby converging to the midpoint position of the steering wheel 1. Control to improve the performance.

  Such control may not be performed until the midpoint is set. Until the midpoint is set, for example, the control is performed with the first detected steering angle θh as the temporary midpoint. May be. The control device 20 functions as a midpoint storage unit for setting the midpoint of the steering wheel 1.

  In the present embodiment, when the detected yaw rate γ is greater than or equal to the set value, when the lateral acceleration Gy is greater than or equal to the set value, or when the difference between the left and right wheel speeds is greater than or equal to the set value. It is determined that vehicle 100 is not in a straight traveling state. Further, depending on whether the stabilization control of the vehicle 100 is not performed, the determination of whether the vehicle 100 is in the straight traveling state may be assisted.

  As the stabilization control, for example, ABS control for controlling the braking pressure control unit 50 to prevent the wheels 6f and 6r from being locked based on the wheel speed, and the braking pressure control unit 50 and the engine to prevent the wheels 6f and 6r from idling. When the traction control for controlling the vehicle 40, the posture stabilization control for controlling the braking pressure control unit 50 and the engine 40 so as to prevent the understeer state and the oversteer state, etc. are performed, the vehicle 100 is determined not to be in the straight traveling state. The

  Further, it may be possible to assist in determining whether the vehicle 100 is in a straight traveling state according to the vehicle speed, acceleration, and front / rear wheel speed difference of the vehicle 100. For example, when the magnitude of acceleration of the vehicle 100 is greater than or equal to a set value, when the magnitude of the front and rear wheel speed difference is greater than or equal to the set value, or when the magnitude of the vehicle speed V is less than or equal to the set value, the vehicle 100 is Since the vehicle is not traveling straight in a stable manner, it is determined that the vehicle is not traveling straight. The midpoint storage unit stores the detected steering amount at the time when the vehicle 100 is determined to be in the straight traveling state as the set midpoint.

The flowchart of FIG. 2 shows a control procedure of the actuator 10 by the control device 20. First, the detection value of each sensor is read (step S1), and the midpoint of the steering wheel 1 is set (step S2). At the beginning of the control, the initial relative detected steering angle θh is stored as a temporary midpoint until the midpoint is set.

  Next, the steering assist force torque τa is calculated (step S3). In this calculation, the relationship between the steering torque τ, the vehicle speed V, and the steering assist force torque τa is determined and stored in advance, and the steering assist force torque τa is obtained from the relationship and the detected steering torque τ and the vehicle speed V. Can be done.

  Next, the steering assist torque τa is corrected according to the detected steering angle θh from the middle point of the steering wheel 1 (step S4). For example, when the magnitude of the detected steering angle θh from the middle point is equal to or smaller than the set value, the steering assist force torque τa is set to zero, or increases when the magnitude of the steering angle θh from the middle point decreases. The steering assist torque is changed by a preset value in accordance with the steering angle θh from the middle point. Next, the actuator 10 is driven so as to generate the obtained steering assist force torque τa (step S5). Thereafter, it is determined whether or not to end the control, for example, depending on whether or not the ignition switch is off (step S6), and if not, return to (step S1).

Next, learning conditions satisfied by the variable amount detection unit will be described with reference to FIGS. 3 to 6, and learning conditions satisfied by the steering amount sensor will be described with reference to FIG. 7.
FIG. 3 shows the behavior of the yaw rate γ detected by the yaw rate sensor 13 as the variable amount detection unit (L1). When the vehicle is almost straight, the yaw rate γ approaches the zero point. A slightly larger value from the zero point of the yaw rate γ is set to a predetermined range γ0. The predetermined range γ0 is determined from experimental values. Then, when the absolute value of the yaw rate γ falls below the predetermined range γ0, it is determined that the vehicle is almost straight. Furthermore, if the absolute value of the current value (γ (n)) P1 of the yaw rate γ is smaller than the absolute value of the previous value (γ (n-1)) Q1 of the yaw rate γ, the vehicle is further in a straight ahead state. I can judge. This condition is a learning condition for setting the midpoint of the steering amount in the yaw rate sensor 13. Further, since the yaw rate sensor performs zero point correction every time the vehicle stops, the detection accuracy is particularly high among the plurality of variable amount detection units.

  FIG. 4 shows the behavior of the lateral acceleration Gy detected by the lateral acceleration sensor 14 as the variable amount detection unit (L2). When the vehicle is almost straight, the lateral acceleration Gy approaches the zero point. A slightly larger value from the zero point of the lateral acceleration Gy is set to a predetermined range Gy0. The predetermined range Gy0 is determined from experimental values. Then, when the absolute value of the lateral acceleration Gy falls below the predetermined range Gy0, it is determined that the vehicle is almost straight. Specifically, when the absolute value of the current value (Gy (n)) P2 of the lateral acceleration Gy is equal to or less than a predetermined range Gy0, it is determined that the vehicle is in a straight traveling state. This condition is a learning condition for setting the midpoint of the steering amount in the lateral acceleration sensor 14.

  FIG. 5 shows the behavior of the absolute value | W1−W2 | of the left and right wheel speed difference when driving the front wheels, which is detected by the left and right wheel speed sensor 15 when driving the front wheels as the variable amount detection unit (L3). When the vehicle is almost straight, the absolute value | W1-W2 | of the left and right wheel speed difference approaches the zero point. A value slightly larger than the zero point of the absolute value | W1-W2 | of the left and right wheel speed difference is set as a predetermined range W01. The predetermined range W01 is determined from experimental values. When the absolute value | W1-W2 | of the left and right wheel speed difference falls below the predetermined range W01, it is determined that the vehicle is almost straight. Specifically, when the absolute value | W1 (n) −W2 (n) | P3 of the current value of the absolute value | W1−W2 | of the left and right wheel speed difference falls below a predetermined range W01, the vehicle is in a straight traveling state. Judge that it became. This condition is used as a learning condition for setting the midpoint of the steering amount in the left and right wheel speed sensor 15 when driving the front wheels.

  FIG. 6 shows the behavior of the absolute value | W3−W4 | of the difference between the left and right wheel speeds when driving the rear wheels, which is detected by the left and right wheel speed sensor 15 when driving the rear wheels as the variable amount detection unit (L4). When the vehicle is almost straight, the absolute value | W3-W4 | of the left and right wheel speed difference approaches the zero point. A value slightly larger than the zero point of the absolute value | W3-W4 | of the left and right wheel speed difference is set as a predetermined range W02. The predetermined range W02 is determined from experimental values. When the absolute value | W3−W4 | of the left and right wheel speed difference falls below the predetermined range W02, it is determined that the vehicle is almost straight. Specifically, when the absolute value | W3 (n) −W4 (n) | P4 of the current value of the absolute value | W3−W4 | of the left and right wheel speed difference falls below a predetermined range W02, the vehicle is in a straight traveling state. Judge that it became. This condition is used as a learning condition for setting the middle point of the steering amount in the left and right wheel speed sensor 15 when driving the rear wheels.

  FIG. 7 shows the behavior of the steering angle θh detected by the steering amount sensor 12 (L5). The vehicle is almost linearly driven by the yaw rate γ, the lateral acceleration Gy, and the absolute value of the left and right wheel speed difference when driving the front wheels | W1-W2 | If the current value P5 (θh (n)) of the steering angle is smaller than the previous value Q5 (θh (n-1)) of the steering angle, it can be determined that the vehicle has gone straight ahead. This condition is used as a learning condition for setting the midpoint of the steering amount in the steering amount sensor 12.

The flowchart of FIG. 8 shows the midpoint setting procedure by the control device 20.
First, the absolute value of the previous value (γ (n−1)) of the yaw rate γ is smaller than the predetermined range γ0, and the current value (γ (n)) of the yaw rate γ is smaller than the predetermined range γ0. It is determined whether it is small (step S101). It is determined that the absolute value of the current value (γ (n)) of the yaw rate γ is smaller than the predetermined range γ0 and the absolute value of the current value (γ (n)) of the yaw rate γ is smaller than the predetermined range γ0. If this is the case (step S101: YES), it is determined whether the absolute value of the current value (γ (n)) of the yaw rate γ is smaller than the absolute value of the previous value of the yaw rate γ (γ (n-1)) ( Step S102). The set value γ0 may be set to a maximum value when the vehicle 100 is traveling substantially straight, and a specific value may be obtained experimentally.

  Next, when it is determined that the absolute value of the current value (γ (n)) of the yaw rate γ is smaller than the absolute value of the previous value (γ (n−1)) of the yaw rate γ (step S102: YES), It is determined whether or not the absolute value of the current value (Gy (n)) of the acceleration Gy is smaller than a predetermined range Gy0 (step S103). The set value Gy0 may be set to a maximum value when the vehicle 100 is traveling substantially straight, and a specific value may be obtained experimentally.

  Next, when it is determined that the absolute value of the current value (Gy (n)) of the lateral acceleration Gy is smaller than the predetermined range Gy0 (step S103: YES), the difference between the left and right wheel speeds when driving the front wheels (W1-W2). ) Current value | W1 (n) −W2 (n) | is determined whether or not the absolute value is smaller than a predetermined range W01 (step S104). If it is determined that the absolute value of the current value | W1 (n) −W2 (n) | of the left and right wheel speed difference (W1−W2) is smaller than the predetermined range W01 (step S104: YES), the current steering angle It is determined whether or not the absolute value of the value θh (n) is smaller than the absolute value of the previous value θh (n−1) of the steering angle (step S105). When it is determined that the absolute value of the current value θh (n) of the steering angle is smaller than the absolute value of the previous value θh (n-1) of the steering angle (step S105: YES), the relative value detected at that time The current steering angle current value θh (n) is stored as a set midpoint (step S106), and the process returns to the control routine of the actuator 10.

If step S104 is NO, the process proceeds to step S107.
In step S107, it is determined whether or not the absolute value of the current value | W3 (n) −W4 (n) | of the left and right wheel speed difference (W3−W4) during rear wheel drive is smaller than a predetermined range W02. If it is determined that the absolute value of the current value | W3 (n) −W4 (n) | of the left and right wheel speed difference (W3−W4) is smaller than the predetermined range W02 (step S107: YES), step S105 is performed. Proceed to
If the determinations in steps S101 to S104, step S105, and step S107 are NO, the process returns to the control routine for the actuator 10.

As described above, according to the present embodiment, the following operations and effects can be obtained.
As described above, when the detection values of the plurality of vehicle straight-ahead state variable detection units are within the straight-ahead determination range and it is determined that the vehicle is in a straight-ahead state, the detection values of the plurality of vehicle straight-ahead state variable detection units are zero. Even after becoming, the detected rudder angle position is set as a midpoint until it is out of the straight traveling determination range.

  In this respect, in the present embodiment, the absolute value of the detection values of the plurality of vehicle straight-ahead state variable detection units is within a predetermined range, and zero correction is performed every time the vehicle stops, and the yaw rate with high variable detection accuracy Focusing on the sensor, when the learning condition that the current value of the detected value of the yaw rate sensor is smaller than the absolute value of the previous value is satisfied, the detected steering amount at that time is stored as a setting midpoint. It was.

Furthermore, in addition to the above conditions, the fact that the absolute value of the current value of the steering amount sensor is smaller than the absolute value of the previous value is considered as a further learning condition. With this configuration, since the midpoint learning is performed only when the variable amount detection unit and the steering amount sensor satisfy a plurality of conditions, there is no error in the midpoint of the steering wheel, and a more reliable and accurate midpoint. Learning is possible.
As a result, it is possible to optimize the control according to the steering amount from the midpoint.

In addition, you may change this embodiment as follows.
In the above embodiment, the present invention is embodied in a so-called column type EPSA, but the present invention may be applied to a so-called pinion type or rack assist type EPS.

In the above embodiment, the variable point detection unit is set to the midpoint learning condition when the difference between the left and right wheel speeds when driving the front wheels or the difference between the left and right wheel speeds when driving the rear wheels falls within a predetermined range. However, the present invention is not limited to this, and the midpoint learning condition may be used when the difference between the average of the front and rear wheel left wheel speeds and the average of the front and rear wheel right wheel speeds falls within a predetermined range.

In the above embodiment, the steering torque value is not used as the variable detection means. However, when the steering torque value is used as the variable detection means and the steering torque value falls within a predetermined range, the midpoint learning condition is also used. Good.

In the above embodiment, when the learning condition is satisfied for each sampling of the variable detection unit, the midpoint is set, but a predetermined time is set, and when the learning condition has passed the predetermined time, the midpoint is set. May be.

1: Steering wheel, 2: Steering shaft,
3: Universal joint, 4: Pinion, 5: Rack,
7: Tie rod, 8: Knuckle arm, 9: Reduction gear mechanism,
10: Actuator, 11: Torque sensor, 12: Steering amount sensor,
13: Yaw rate sensor (variable detector), 14: Lateral acceleration sensor (variable detector),
15: Wheel speed sensor (variable detector), 16: Vehicle speed sensor,
20: Control device (midpoint storage unit, control unit, variable amount detection unit),
40: engine, 50: braking pressure control unit, 51: brake pedal,
52: Master cylinder, 54: Brake device, 100: Vehicle,
6f: left and right front wheels, 6r: left and right rear wheels,
θh: steering angle, γ: yaw rate, Gy: lateral acceleration, V: vehicle speed,
τ: steering torque, τa: steering assist torque,
γ0: predetermined range of yaw rate γ, Gy0: predetermined range of lateral acceleration Gy,
W01: a predetermined range of the absolute value | W1-W2 | of the left and right wheel speed difference when driving the front wheels,
W02: A predetermined range of the absolute value | W3−W4 |

Claims (2)

A torque sensor for detecting the steering torque of the steering wheel;
An actuator that generates a steering assist torque according to the detected steering torque;
A steering amount sensor that detects a relative steering amount of the steering wheel with respect to a setting midpoint;
A midpoint storage unit for storing a set midpoint of the steering amount;
A plurality of variable detectors including a yaw rate sensor that detects a variable that changes according to the traveling direction of the vehicle at a predetermined period;
A control unit for controlling the actuator,
The controller is
When the absolute value of the detection values of the plurality of variable detection units is within a predetermined range, and the learning condition that the absolute value of the current value of the detection value of the yaw rate sensor is smaller than the absolute value of the previous value, The electric power steering apparatus characterized in that the detected steering amount at that time is stored as a setting midpoint in the midpoint storage unit, and the actuator is controlled in accordance with the detected steering amount from the set midpoint. . The controller is
The electric power steering apparatus according to claim 1, wherein a further learning condition is that the absolute value of the current value of the steering amount sensor is smaller than the absolute value of the previous value.

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