JP2012144111A - Steer-by-wire system - Google Patents

Abstract

An object of the present invention is to optimally adjust the responsiveness of a steering wheel in a steer-by-wire system.
A reaction force generation motor control means 24 includes an abnormality detection means 24B, and communicates with operation angle detection means 10 and 12 for detecting an operation angle of a steering wheel 7 to generate reaction force by the abnormality detection means 24B. When an abnormal state to be stopped is detected, the terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited based on the steering wheel operation angle detected by the operation angle detection means 10 and 12.
[Selection] Figure 4

Description

  The present invention relates to a steer-by-wire system, and more particularly to a steer-by-wire system that controls a reaction force generated in a steering wheel.

Some vehicles are equipped with a steer-by-wire system in which a steering wheel and a steering wheel are mechanically separated from each other and a reaction force generation motor that generates a reaction force corresponding to a road surface reaction force is provided on the steering wheel.
In this steer-by-wire system, the reaction force to the steering wheel is stopped when an abnormality occurs, and mechanical backup is achieved by engaging the clutch, and the reaction force stops between the occurrence of the abnormality and the engagement of the clutch. If this happens, the steering wheel may be overcut and the vehicle may become unstable.For this reason, the terminals of the reaction force generation motor are short-circuited by a dedicated relay to establish an electromagnetic brake state, and the steering wheel suddenly In order to prevent lightening and to adjust the weight of the electromagnetic brake, some brakes are adjusted by PWM control of the short state.

JP 2006-44378 A

  The vehicle steering device according to Patent Document 1 has a backup device that mechanically connects the steering mechanism and the steering wheel when the system is abnormal, and the steering reaction force is rapidly reduced until the backup device is activated. Depending on the driver's power, excessive steering is prevented. Therefore, control is performed so that the terminals of the reaction force generating motor are short-circuited for the time until the backup device is operated, and the reaction force generated by short-circuiting the terminals of the reaction force generating motor is constant and maintained. This is about 1/2 of the steering reaction torque at the time of steering.

  However, conventionally, in Patent Document 1 described above, since a relay switch that is used only when the system malfunctions is mounted, the cost is increased and the weight (feeling of steering wheel response) can be adjusted. In the circuit configuration, the adjustment is not sufficient, and the steering reaction torque may change suddenly when the system is abnormal.

  Accordingly, an object of the present invention is to provide a steer-by-wire system that optimally adjusts the responsiveness of the steering wheel.

  In this invention, the steering wheel and the steering wheel are mechanically separated, and the steering wheel is provided with a reaction force generation motor that generates a reaction force corresponding to the road surface reaction force. A steer-by-wire system provided with reaction force generation motor control means for short-circuiting the terminals of the reaction force generation motor when an abnormality state in which reaction force generation stops is detected by the abnormality detection means The operation angle detection means for detecting the operation angle of the steering wheel is provided, and the reaction force generation motor control means is configured to detect the operation angle detection means when an abnormal state in which reaction force generation is stopped is detected by the abnormality detection means. Characterized in that the terminals of the reaction force generation motor are intermittently short-circuited based on the steering wheel operation angle detected by That.

  The steer-by-wire system of the present invention can optimally adjust the responsiveness of the steering wheel.

FIG. 1 is a flowchart of the reaction force control of the steering wheel. (Example) FIG. 2 is a configuration diagram of a drive circuit (H bridge circuit) of the reaction force generation motor. (Example) FIG. 3 is a diagram of a drive duty (Duty) map. (Example) FIG. 4 is a block diagram of the steer-by system. (Example)

  The present invention achieves the purpose of optimally adjusting the responsiveness of the steering wheel by intermittently short-circuiting the terminals of the reaction force generating motor according to the steering wheel steering angle.

  1 to 4 show an embodiment of the present invention. In FIG. 4, 1 is a vehicle and 2 is a steer-by-wire system. This steer-by-wire system 2 includes an operation mechanism 3 and a steering mechanism 4 that are not mechanically connected, and electrically drives the steering mechanism 4 to freely change the gear ratio.

As shown in FIG. 4, the operation mechanism 3 includes a steering shaft 6 that is pivotally supported with respect to the steering column 5, and a steering wheel 7 that is integrally provided at an upper end portion of the steering shaft 6 and can be manually operated. A reaction force generation mechanism 8 and a rotation stopper mechanism 9 attached to the lower end portion of the steering shaft 6 are provided. The reaction force generation mechanism 8 applies a reaction force to the steering wheel 7. The rotation stopper mechanism 9 limits the number of rotations of the steering wheel 7.
In addition, a first operating angle detecting means 10 for detecting the steering wheel operating angle at the upper end of the steering column 5 is provided between the lower end of the steering column 5 and the reaction force generating mechanism 8. A torque sensor 11 that detects rotational torque and a second operation angle detection means 12 that detects a steering wheel operation angle are attached.
A reaction force generation motor (steering motor) 13, which is an electric motor connected to a built-in gear, is attached to the steering column 5. The reaction force generation motor 13 is provided along with the steering shaft 6 and generates a reaction force corresponding to the road surface reaction force on the steering wheel 7.

The steering mechanism 4 is connected to the left front wheel 14L and the right front wheel 14R as steering wheels, the left tie rod 15L and the right tie rod 15R for driving the left front wheel 14L and the right front wheel 14R, and the left tie rod 15L and the right tie rod 15R. A steering box 16 incorporating a rack shaft, a pinion shaft 17 connected to the rack shaft of the steering box 16, and a steering motor gear box 18 attached to the pinion shaft 17 and incorporating a gear are provided.
Further, a first rotation angle sensor 19 and a second rotation angle sensor 20 that detect the rotation angle of the pinion shaft 17 on the upper side of the steering motor gear box 18 are attached to the pinion shaft 17.
Two first steering motors 21 and 22 are attached to the steering motor gear box 18 as actuators so as to be connected to the built-in gear. The first steering motor 21 and the second steering motor 22 perform steering control of the left front wheel 14L and the right front wheel 14R.
Therefore, the steer-by-wire system 2 mechanically separates the steering wheel 7 from the left front wheel 14L and the right front wheel 14R as steering wheels.

The steer-by-wire system 2 is driven by the control device 23. The control device 23 includes a reaction force generation motor control means 24, a first steering control means 25, and a second steering control means 26, and also includes a reaction force generation mechanism 8, a rotation stopper mechanism 9, and a first steering mechanism. Operation angle detection means 10, torque sensor 11, second operation angle detection means 12, reaction force generation motor 13, first rotation angle sensor 19, second rotation angle sensor 20, first steering motor 21, and second steering motor 22 Have contacted.
The reaction force generation motor control means 24 includes a CPU 24 </ b> A and directly communicates with the reaction force generation motor 13, the vehicle information detection means 27, and the display alarm device 28, and commands the reaction force and assist force of the reaction force generation motor 13.
The first steering control means 25 includes a CPU 25 </ b> A, communicates directly with the first steering motor 21, and drives and controls the first steering motor 21.
The second steering control means 26 includes a CPU 26 </ b> A, communicates directly with the second steering motor 22, and drives and controls the second steering motor 22.
The vehicle information detection means 27 detects various vehicle information such as the vehicle speed, the engine speed, the ignition switch state, and the shift position, and outputs them to the reaction force generation motor control means 24.
The display alarm device 28 warns by a warning light display or a buzzer.
In this steer-by-wire system 2, the first steering motor 21 and the second steering motor 22 are driven in accordance with the steering wheel operation angles from the first operation angle detection means 10 and the second operation angle detection means 12, and the left front wheel 14L, Control is performed to turn the right front wheel 14R left and right.
Further, the road surface reaction force to the steering wheel 7 is applied by the reaction force generation motor 13 being controlled by the reaction force generation motor control means 24.

As shown in FIG. 2, the drive circuit 29 of the reaction force generation motor 13 is a conventional H-bridge circuit, a fail-safe relay 30 that communicates with the reaction force generation motor control means 24, and the reaction force generation motor control means. Four first motor driving elements (Tr1) 31A to fourth motor driving elements (Tr4) 31D as motor driving elements (switching elements) communicated with 24 and a terminal 13A on one side are driven by the first motor. The other side terminal 13B is connected to the third motor driving element (Tr3) 31C and the fourth motor driving element (Tr4) 31D while communicating with the driving element (Tr1) 31A and the second motor driving element (Tr2) 31B. The reaction force generation motor 13 is provided. In this case, the fail safe relay 30 communicates with the motor drive power source P. The first motor driving element (Tr1) 31A and the third motor driving element (Tr3) 31C are in communication with each other and also in contact with the fail-safe relay 30. Further, the second motor driving element (Tr2) 31B and the fourth motor driving element (Tr4) 31C are in communication with each other, and are also in contact with the ground (GND) E.
The reaction force generation motor 13 is rotated forward and backward by duty-controlling the four first motor driving elements (Tr1) 31A to the fourth motor driving element (Tr4) 31D.
Further, the power for driving the reaction force generation motor 13 is supplied and stopped by the fail safe relay 30.
Furthermore, by turning on the second motor driving element (Tr2) 31B and the fourth motor driving element (Tr4) 31D, the electromagnetic brake can be applied as in the prior art.

The reaction force generation motor control means 24 includes an abnormality detection means 24B that detects whether or not the reaction force generation is in an abnormal state. When the abnormality detection means 24B detects an abnormal state in which the reaction force generation stops, the reaction force generation motor control means 24 The terminals 13A and 13B of the force generation motor 13 are short-circuited.
The reaction force generation motor control means 24 is detected by the first operation angle detection means 10 and the second operation angle detection means 12 when the abnormality detection means 24B detects an abnormal state where reaction force generation stops. The terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited based on the steering wheel operation angle.
Further, the reaction force generation motor control unit 24 includes a storage unit 24C that stores a reaction force value immediately before the abnormality detection unit 24B detects an abnormal state in which reaction force generation is stopped, and the abnormality detection unit 24B generates reaction force. When an abnormal state occurs, the terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited so that the reaction force torque value stored in the storage unit 24C is obtained.
Furthermore, the drive circuit 29 of the reaction force generation motor 13 is a conventional H bridge circuit. The reaction force generation motor control unit 24 controls the four motor drive elements 31A to 31D of the drive circuit 29 that is an H bridge circuit when the abnormality detection unit 24B does not detect an abnormal state in which the reaction force generation stops. Thus, the rotation of the reaction force generation motor 13 is controlled, and when an abnormal state in which the reaction force generation stops is detected by the abnormality detection means 24B, the first to fourth motor driving elements 31A to 31D are set to duty ( (Duty) is controlled to intermittently short-circuit the terminals 13A and 13B of the reaction force generation motor 13.

  Therefore, the reaction force generation motor control means 24 includes a drive duty map 24D as shown in FIG. 3, and obtains a drive duty value (duty_v) corresponding to the rotational angular velocity θv ([deg / s]) of the steering wheel 7. . In FIG. 3, for example, the drive duty value (duty_v) decreases as the rotational angular velocity θv of the steering wheel increases.

Next, reaction force control of the steering wheel 7 according to this embodiment will be described based on the flowchart of FIG. In this control, the reaction force generation motor 13 is driven to provide a feeling of response of the steering wheel 7 even when a problem that causes the reaction force control to stop occurs.
As shown in FIG. 1, when the program of the control device 23 is started (step A01), the current reaction force output value (trq0) is acquired and set as the initial torque (step A02), and F = 1 (output inconsistency flag = 1) (step A03).
Then, it is determined whether or not a failure motor drive condition is satisfied (step A04).
The failure motor drive conditions include the condition that the CPU 24A of the reaction force generation motor control means 24 is normal, the condition that the reaction force generation motor 13 is normal, and all the first to fourth motor driving conditions. This is satisfied when the conditions that the elements 31A to 31D are normal and all the conditions when the reaction force control continuation impossible condition is satisfied are satisfied.
If this step A04 is YES, the first motor driving element 31A and the third motor driving element 31C are turned off (step A05).
Then, it is determined whether or not a duty value corresponding to the initial torque (trq0) has been set (step A06).
When this step A06 is NO, it is set as the duty value corresponding to the final output reaction force torque value duty_out = trq0 (step A07).
If this step A06 is YES, the rotational angular velocity θv of the steering wheel 7 is calculated (step A08), and the rotational angular velocity θv ([deg / s] of the steering wheel 7 is calculated from the drive duty map as shown in FIG. ] Is determined (step A09).
Then, it is determined whether F = 1, that is, whether output matching is necessary (step A10).
When this step A10 is YES, the output difference duty_diff is calculated by duty_diff = duty_out−duty_v (step A11).
Next, it is determined whether or not duty_diff = 0 (step A12).
If this step A12 is YES, F = 0 (alignment completion) is set (step A13).
After step A13 or when step A10 is NO, duty_out = duty_v is set (step A14).
When step A12 is NO, 20% of the output difference is corrected by duty_out = duty_out-duty_diff * 0.2 (step A15). That is, the drive duty value duty_v obtained from the drive duty map of FIG.
After the process of step A15, after the process of step A14 or after the process of step A07, the second motor driving element 31B and the fourth motor driving element 31D are set to the final output reaction force torque value. Then, it is driven with duty_out (step A16), and the process returns to step A04.
On the other hand, when step A04 is NO, all the first motor driving elements 31A to fourth motor driving elements 31D are turned off (step A17), and the program is ended (step A18).

Although the embodiments of the present invention have been described above, the configuration of the above-described embodiments will be described for each claim.
First, in the invention according to claim 1, the reaction force generation motor control means 24 is configured to detect the first operation angle detection means 10 and the second operation when the abnormality detection means 24B detects an abnormal state where reaction force generation stops. Based on the steering wheel operation angle detected by the angle detection means 12, the terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited.
As a result, the responsiveness of the steering wheel 7 can be optimally adjusted according to the steering wheel operating angle from the occurrence of an abnormality that stops the reaction force generation to the stop of the system power supply.
In the invention according to claim 2, the reaction force generation motor control means 24 includes a storage means 24C for storing a reaction force value immediately before the abnormality detection means 24B detects an abnormal state in which reaction force generation is stopped, and detects abnormality. When an abnormal state occurs in which reaction force generation is stopped by the means 24B, the terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited so that the reaction force torque value stored in the storage means 24C is obtained.
As a result, even when the reaction force control cannot be continued during sudden steering, it is possible to prevent a sudden change in the feeling of response of the steering wheel 7 and to steer while preventing the steering wheel 7 from being overcut. .
In the invention according to claim 3, the drive circuit 29 of the reaction force generation motor 13 is an H-bridge circuit. The reaction force generation motor control unit 24 controls the four motor drive elements 31A to 31D of the drive circuit 29 that is an H bridge circuit when the abnormality detection unit 24B does not detect an abnormal state in which the reaction force generation stops. Thus, the rotation of the reaction force generation motor 13 is controlled. On the other hand, when the abnormality detection unit 24B detects an abnormal state in which the reaction force generation stops, the motor driving elements 31A to 31D are duty controlled. The terminals 13A and 13B of the reaction force generation motor 13 are intermittently short-circuited.
As a result, it is possible to give the driver a sense of responsiveness to the steering wheel 7 at the time of an abnormality in which the reaction force generation stops with the motor drive circuit 29 used conventionally.

Further, in this embodiment, there are the following specific effects as compared with the conventional cited document 1.
First, since a mechanical backup device is not required, the terminal 13A of the reaction force generation motor 13 is provided to give the driver a feeling of response corresponding to the steering wheel operation angle from the occurrence of an abnormality that stops reaction force generation until the system power supply is stopped. , 13B can be duty-controlled for each motor driving element (switching element) of the drive circuit 29 so as to intermittently short-circuit between 13B.
Further, the reaction force torque value at the normal time is stored, and when an abnormality occurs, the reaction force torque value immediately before the occurrence of the abnormality is controlled to prevent a sudden change in the feeling of response of the steering wheel 7.
Further, the relay switch is not required, the configuration can be simplified and the cost can be reduced.
Furthermore, as in the case of the conventional cited document 1, it is effective because the abnormality can be detected by monitoring the drive current value of the power supply circuit and the like.
Further, since the first motor driving element 31A and the third motor driving element 31C are turned off when the fail motor driving condition is satisfied, the steering wheel 7 is controlled regardless of the state of the fail safe relay 30. Make it executable.
Furthermore, it is possible to compensate for the sudden torque reduction of the steering wheel 7 using only the normal fail-safe relay 30 and the drive circuit 29 using the H bridge, and from the occurrence of abnormality to the mechanical backup operation as in the past. It can be used not only during the period until it moves, but also between the occurrence of an abnormality and the system power supply stop (system stop).

  The steer-by-wire system according to the present invention can be applied to various vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Steer-by-wire system 3 Operation mechanism 4 Steering mechanism 5 Steering column 6 Steering shaft 7 Steering wheel 10 First operation angle detection means 11 Torque sensor 12 Second operation angle detection means 13 Reaction force generation motor 14L Left front wheel (steering wheel)
14R Right front wheel (steering wheel)
DESCRIPTION OF SYMBOLS 21 1st steering motor 22 2nd steering motor 23 Control apparatus 24 Reaction force generation motor control means 26 1st steering control means 27 2nd steering control means 29 Drive circuit (H bridge circuit)
30 Fail-safe relay 31A-31D Motor drive element

Claims (3)

  An abnormality that detects whether or not the reaction force generation is stopped by providing a reaction force generation motor that generates a reaction force corresponding to the road surface reaction force on the steering wheel when the steering wheel and the steering wheel are mechanically separated. In the steer-by-wire system provided with a detection means, and provided with a reaction force generation motor control means for short-circuiting between the terminals of the reaction force generation motor when an abnormal state where reaction force generation stops is detected by the abnormality detection means, Operation angle detection means for detecting an operation angle of the wheel is provided, and the reaction force generation motor control means is detected by the operation angle detection means when an abnormal state in which reaction force generation is stopped is detected by the abnormality detection means. A steering bar characterized in that the terminals of the reaction force generation motor are intermittently short-circuited based on a steering wheel operating angle. Wire system.   The reaction force generation motor control means includes storage means for storing a reaction force value immediately before an abnormal state in which reaction force generation is stopped by the abnormality detection means is detected, and reaction force generation is stopped by the abnormality detection means. 2. The steer-by-wire system according to claim 1, wherein when an abnormal state occurs, the terminals of the reaction force generation motor are intermittently short-circuited so as to have a reaction force torque value stored in the storage unit.   The drive circuit of the reaction force generation motor is an H bridge circuit, and the reaction force generation motor control means is configured to detect four abnormal states of the H bridge circuit when an abnormality state where reaction force generation stops is not detected by the abnormality detection means. The rotation of the reaction force generating motor is controlled by controlling the motor driving element, and when the abnormal state where the reaction force generation stops is detected by the abnormality detecting means, the motor driving element is duty controlled to control the rotation of the reaction force generating motor. The steer-by-wire system according to claim 1 or 2, wherein the terminals of the reaction force generation motor are intermittently short-circuited.

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