JP2014151829A - Control device for power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a power steering device which allows a driver to recognize abnormality of tire pressure easily.SOLUTION: An ECU executes normal assist control when the ECU determines that a tire pressure is not abnormal (Step 104). Also, when the ECU determines that the tire pressure is abnormal, and when the basic assist control amount Ib is not zero (trying to turn), the ECU executes first abnormality notification assist control (Step 106). On the other hand, when the ECU determines that the tire pressure is abnormal, and when the basic assist control amount Ib is zero (trying to advance straight), only when an absolute value of acceleration α is predetermined acceleration α0 or greater, the ECU executes second abnormality notification assist control (Step 108), and when the absolute value of the acceleration α is below the predetermined acceleration α0, the ECU executes the normal assist control.

Description

  The present invention relates to a control device for a power steering device.

  Some recent vehicles are provided with an air pressure detector that detects the tire air pressure of each wheel, and when the tire air pressure is out of the proper range and becomes abnormal, it is possible to notify the driver to that effect. It is like that. As a method of notifying abnormalities in tire air pressure, when the tire air pressure abnormality is detected, the assist force of the power steering device is made different from that when the tire air pressure is normal, thereby prompting the driver to recognize the abnormality. (For example, Patent Document 1).

  Specifically, in the control device for a power steering device described in Patent Literature 1, when an abnormality in tire air pressure is detected, a change in drivability due to the air pressure difference is emphasized according to the tire air pressure difference between the left and right. By differentiating the assist force at the time of left turning and right turning, the driver is informed of the tire pressure abnormality. Further, the patent document 1 proposes to offset a preset assist force map (basic steering force map) characteristic in accordance with a difference between left and right tire air pressures when an abnormality in tire air pressure is detected. Has been. Thus, even in a state where the steering wheel is in the neutral position, that is, in a state where the driver tries to move the vehicle straight, the assisting force is applied to the steering system to deflect the vehicle in either the left or right direction, thereby Informs the air pressure abnormality.

JP 2006-7969 A

  By the way, even if the tire pressure of the rear wheels deviates from the appropriate range and becomes abnormal, the influence is unlikely to appear in the behavior of the vehicle or the steering feeling. In particular, when there is almost no difference in tire air pressure between the left and right rear wheels, the tendency becomes remarkable. Therefore, when the tire pressure of the rear wheels is abnormal, if the assist force is applied so as to emphasize the influence on the steering feeling due to the abnormality, the steering feeling may become unnatural. As a result, it becomes difficult for the driver to perceive that the tire pressure is abnormal from the steering feeling. In particular, when the assist force is applied in a state where the steering wheel is in the neutral position as in Patent Document 1, the steering feeling tends to be unnatural.

  Such a problem is not limited to the case where the tire pressure of the rear wheel is abnormal, and can occur even when the tire pressure of the front wheel is abnormal. Therefore, the abnormality of the tire pressure is notified as naturally as possible. It was desirable and improvement was desired.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a control device for a power steering device that allows a driver to easily recognize an abnormality in tire air pressure.

  A control device for a power steering device that solves the above problem is a control device for a power steering device that controls the operation of a steering force assist device that applies assist force to a steering system. If the tire pressure is determined to be abnormal based on the signal, assist force is applied so that the vehicle deflects in either the left or right direction only when the vehicle is accelerating or decelerating. The gist is to execute the abnormality notification assist control.

  Here, at the time of acceleration / deceleration of the vehicle, an external force (road reaction force or the like) applied to each wheel increases, so that the influence of the tire air pressure is likely to appear on the behavior of the vehicle, and the steering feeling is likely to change. Accordingly, the abnormality notification assist control is executed only when the tire air pressure is abnormal and at least one of the acceleration and deceleration of the vehicle as in the above configuration, so that the steering due to the abnormality of the tire air pressure is naturally performed. The effect on feeling is emphasized. As a result, it becomes easy to perceive that the tire air pressure is abnormal, so that the driver can easily recognize the tire air pressure abnormality.

  In the power steering apparatus control device, the magnitude of the assist force applied to the steering system may be changed by executing the abnormality notification assist control in accordance with the magnitude of vehicle acceleration detected by the acceleration detector. preferable.

  According to the above configuration, since the magnitude of the assist force is changed in accordance with the magnitude of the acceleration of the vehicle, the influence on the steering feeling due to abnormal tire pressure is emphasized in a more natural manner, and the driver Abnormal air pressure can be recognized more easily.

  According to the present invention, a driver can easily recognize an abnormality in tire air pressure.

1 is a schematic configuration diagram of a vehicle equipped with an electric power steering device. The block diagram of ECU. The graph which shows the relationship between compensation assist control amount and the acceleration of a vehicle. The flowchart which shows the transfer procedure of the control mode by ECU.

Hereinafter, an embodiment of a control device for an electric power steering device (EPS) using a motor as a drive source will be described with reference to the drawings.
The vehicle 1 shown in FIG. 1 is equipped with an EPS 3 that steers the wheels 2a and 2b as front wheels. In the EPS 3, the steering shaft 5 to which the steering wheel 4 is fixed is connected to the rack shaft 7 via a rack and pinion mechanism 6. Thereby, the rotation of the steering shaft 5 accompanying the steering operation is converted into the reciprocating linear motion of the rack shaft 7 by the rack and pinion mechanism 6. The steering shaft 5 is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, the reciprocating linear motion of the rack shaft 7 accompanying the rotation of the steering shaft 5 is transmitted to the knuckle (not shown) via the tie rods 11 connected to both ends of the rack shaft 7, whereby the steering angles of the wheels 2a and 2b That is, the traveling direction of the vehicle 1 is changed.

  The EPS 3 also includes a steering force assisting device 22 that applies an assist force to the steering system using the motor 21 as a drive source, and an ECU 23 as a power steering device control device that controls the operation of the steering force assisting device 22. .

  In the steering force assisting device 22, the motor 21 is drivingly connected to the column shaft 8 via a speed reduction mechanism 25 such as a worm and wheel. The steering force assisting device 22 applies the motor torque as an assist force to the steering system by decelerating the rotation of the motor 21 and transmitting it to the column shaft 8.

  On the other hand, a vehicle speed sensor 31 for detecting the vehicle speed SPD of the vehicle 1 and a torque sensor 32 for detecting the steering torque T applied to the steering shaft 5 are connected to the ECU 23. The ECU 23 controls the operation of the steering force assisting device 22, that is, the assist force applied to the steering system, by supplying driving power to the motor 21 based on the vehicle speed SPD and the steering torque T.

Next, the electrical configuration of the EPS of this embodiment will be described.
As shown in FIG. 2, the ECU 23 includes a microcomputer 41 that outputs a motor control signal, and a drive circuit 42 that supplies drive power to the motor 21 based on the motor control signal. The microcomputer 41 receives the vehicle speed SPD and the steering torque T, and the microcomputer 41 outputs a motor control signal based on these state quantities. The microcomputer 41 detects each state quantity at a predetermined sampling period (detection period), and generates a motor control signal by executing each arithmetic processing shown in the following control blocks at every predetermined period.

  More specifically, the microcomputer 41 is calculated by a current command value calculation unit 43 that calculates a current command value I * corresponding to a target value of power supply to the motor 21, that is, a target assist force, and a current command value calculation unit 43. And a motor control signal output unit 44 that outputs a motor control signal based on the current command value I *.

  The current command value calculation unit 43 is provided with a basic assist calculation unit 51, and the vehicle speed SPD and the steering torque T are input to the basic assist calculation unit 51. The basic assist calculation unit 51 calculates a basic assist control amount Ib as a basic control component corresponding to the target assist force based on the steering torque T and the vehicle speed SPD. Specifically, the basic assist calculation unit 51 calculates the basic assist control amount Ib having a larger value (absolute value) as the absolute value of the steering torque T is larger and the vehicle speed SPD is slower. The basic assist control amount Ib calculated in this way is input to the adder 53 together with the compensation assist control amount Ic calculated by the compensation assist calculation unit 52 described later. Then, the current command value calculation unit 43 outputs a value obtained by adding these control amounts by the adder 53 to the motor control signal output unit 44 as a current command value I *.

  The motor control signal output unit 44 executes the current feedback control calculation so as to cause the current command value I * calculated by the current command value calculation unit 43 to follow the actual current value supplied to the motor 21. The motor control signal output to the drive circuit 42 is calculated. The motor control signal calculated in this way is output from the microcomputer 41 to the drive circuit 42, and the drive power based on the motor control signal is supplied to the motor 21 by the drive circuit 42. A motor torque corresponding to (amount of energization current) is applied to the steering system as an assist force.

  Here, as shown in FIG. 1, each of the wheels 2 a to 2 d of the vehicle 1 is provided with an air pressure detector 61 that detects tire air pressure. Each air pressure detector 61 outputs signals indicating the tire air pressure values Pa to Pd of the wheels 2a to 2d to which the air pressure detector 61 is attached to the ECU 23 by wireless communication. Further, the ECU 23 is lit when a steering sensor (steering angle sensor) 62 for detecting the steering angle θs of the steering wheel 4 and at least one of the tire pressure values Pa to Pd is out of the proper range and becomes abnormal. A lamp 63 is connected. Then, the ECU 23 changes the steering characteristics by changing the assist force applied according to the tire pressure.

  More specifically, the ECU 23 executes normal assist control in which the basic assist control amount Ib is directly used as the current command value I * when all the tire air pressure values Pa to Pd are normal and within the appropriate range. . On the other hand, when at least one of the tire air pressure values Pa to Pd is out of the appropriate range and the basic assist control amount Ib is not zero (turning to turn), the vehicle 1 is deflected in either the left or right direction. 1st abnormality alerting | reporting assist control which provides assist force to is performed. On the other hand, when at least one of the tire air pressure values Pa to Pd is out of the appropriate range and the basic assist control amount Ib is zero (going straight), the absolute value of the acceleration α is equal to or greater than the predetermined acceleration α0. Only, the second abnormality notification assist control is executed as the abnormality notification assist control for applying the assist force so that the vehicle 1 is deflected in any of the left and right directions. On the other hand, if the basic assist control amount Ib is zero and the absolute value of the acceleration α is less than the predetermined acceleration α0 even if at least one of the tire air pressure values Pa to Pd is out of the appropriate range, the normal assist is performed. Execute control.

  More specifically, as shown in FIG. 2, the current command value calculation unit 43 of the microcomputer 41 is provided with a compensation assist calculation unit 52 in addition to the basic assist calculation unit 51. The compensation assist calculation unit 52 is inputted with the longitudinal acceleration α of the vehicle 1 and the basic assist control amount Ib obtained by differentiating the tire air pressure values Pa to Pd, the steering angle θs, and the vehicle speed SPD. That is, in this embodiment, the vehicle speed sensor 31 and the microcomputer 41 constitute an acceleration detector. The compensation assist calculation unit 52 calculates a compensation assist control amount Ic as a compensation control component based on the tire air pressure values Pa to Pd, the steering angle θs, the acceleration α, and the basic assist control amount Ib. For convenience of explanation, the warning lamp 63 is not shown in FIG.

  The compensation assist calculation unit 52 sets the compensation assist control amount Ic to zero when all the tire air pressure values Pa to Pd are within an appropriate range and the tire air pressure is normal. As a result, the current command value calculation unit 43 calculates the current command value I * as it is without changing the value of the basic assist control amount Ib, and the control mode of the ECU 23 becomes the normal assist control.

  Further, the compensation assist calculation unit 52 deflects the vehicle 1 caused by an abnormality in the tire air pressure when at least one of the tire air pressure values Pa to Pd is out of the appropriate range and the basic assist control amount Ib is not zero. The compensation assist control amount Ic is calculated so as to emphasize. Thereby, in the current command value calculation unit 43, the value obtained by changing the non-zero basic assist control amount Ib by the compensation assist control amount Ic is calculated as the current command value I *, and the control mode of the ECU 23 is the first abnormality notification assist control. It becomes.

  Specifically, the compensation assist calculation unit 52 allows the driver to reduce the tire air pressure based on the steering angle θs based on the fact that the vehicle 1 is deflected in a direction in which the air pressure is small in accordance with the magnitude relationship between the tire air pressures in the left-right direction. When it is determined that the vehicle is steered in the direction, the compensation assist control amount Ic is calculated so that the basic assist control amount Ib is increased. On the other hand, when it is determined that the driver is steering in the direction in which the tire air pressure is large based on the steering angle θs, the compensation assist control amount Ic is calculated so that the basic assist control amount Ib becomes small. It should be noted that the compensation assist calculation unit 52 of the present embodiment determines the relationship between the tire air pressure values in the left-right direction, the sum of the tire air pressure values Pa, Pc of the left wheels 2a, 2c, and the tire air pressure values of the left wheels 2b, 2d. Judgment is based on the magnitude relationship with the sum of Pb and Pd. As shown in FIG. 3, the compensation assist calculation unit 52 calculates the absolute value of the compensation assist control amount Ic so as to increase linearly as the absolute value of the acceleration α increases.

  On the other hand, when at least one of the tire air pressure values Pa to Pd is out of the proper range, the current command value I * is zero, and the absolute value of the acceleration α is equal to or greater than the predetermined acceleration α0, the compensation assist calculating unit 52 The compensation assist control amount Ic is calculated so as to emphasize the deflection of the vehicle 1 caused by the abnormality in the tire air pressure values Pa to Pd. Thereby, in the current command value calculation unit 43, the value of the compensation assist control amount Ic is calculated as it is as the current command value I *, and the control mode of the ECU 23 becomes the second abnormality notification assist control. Specifically, a compensation assist control amount Ic that turns the wheels 2a and 2b in a direction in which the tire air pressure is small is calculated in accordance with the magnitude relationship between the tire air pressures in the left-right direction. Further, the compensation assist calculation unit 52 calculates the absolute value of the compensation assist control amount Ic so as to increase linearly as the absolute value of the acceleration α increases.

  On the other hand, when at least one of the tire pressure values Pa to Pd is out of the appropriate range, the current command value I * is zero, and the absolute value of the acceleration α is less than the predetermined acceleration α0, the compensation assist calculating unit 52 The compensation assist control amount Ic is set to zero. Thereby, the control mode of the ECU 23 becomes the normal assist control.

Next, the procedure for shifting the control mode by the ECU according to the present embodiment will be described with reference to the flowchart shown in FIG.
When the ECU 23 acquires various state quantities such as the tire pressure values Pa to Pd, the steering angle θs, and the acceleration α (step 101), whether or not the tire pressure is abnormal (at least one of the tire pressure values Pa to Pd is appropriate). Whether or not out of range) and the tire pressure relationship in the left-right direction are determined (step 102). Subsequently, when the tire air pressure is not abnormal based on the determination result in step 102 (step 103: NO), normal assist control is executed (step 104).

  On the other hand, when the tire air pressure is abnormal (step 103: YES), the ECU 23 determines whether or not the basic assist control amount Ib is zero (step 105). Subsequently, when the basic assist control amount Ib is not zero (step 105: NO), the first abnormality notification assist control is executed (step 106).

  On the other hand, when the basic assist control amount Ib is zero (step 105: YES), the ECU 23 determines whether or not the absolute value of the acceleration α of the vehicle 1 is equal to or greater than a predetermined acceleration α0 (step 107). When the absolute value of the acceleration α is equal to or greater than the predetermined acceleration α0 (step 107: YES), the second abnormality notification assist control is executed (step 108). On the other hand, when the absolute value of the acceleration α is less than the predetermined acceleration α0 (step 107: NO), the routine proceeds to step 104 and normal assist control is executed.

Next, the operation of this embodiment will be described.
For example, when one of the tire air pressure values Pa to Pd gradually decreases during driving and an abnormality occurs, if the driver steers the steering wheel 4 and the vehicle 1 turns, the control mode is normally set. The assist control shifts to the first abnormality notification assist control. As a result, the influence on the steering feeling due to the abnormality in the tire air pressure is emphasized, and the driver can recognize from the steering feeling that the tire air pressure is abnormal.

  On the other hand, when the tire pressure abnormality occurs, and the vehicle 1 is traveling straight, the driver operates the accelerator pedal, the brake pedal (both not shown), etc., and the vehicle 1 accelerates or decelerates at a predetermined acceleration α0 or more. The control mode shifts to the second abnormality notification assist control. Here, when the vehicle 1 is accelerated / decelerated, the external force (road reaction force, etc.) applied to the wheels 2a to 2d is increased. Therefore, the behavior of the vehicle 1 is likely to be affected by the abnormality of the tire air pressure, and the steering feeling changes. easy. Therefore, when the absolute value of the acceleration α of the vehicle 1 is equal to or greater than the predetermined acceleration α0, the second abnormality notification assist control is executed, so that the influence of the abnormality in the tire air pressure is emphasized naturally, and the vehicle is going straight ahead. Even in this case, the driver can easily recognize that the tire pressure is abnormal from the steering feeling. On the other hand, if the driver does not operate the accelerator pedal or the brake pedal (both not shown) and the vehicle 1 does not accelerate or decelerate at a predetermined acceleration α0 or more, the control mode shifts to the normal assist control. As a result, the steering feeling is prevented from becoming unnatural, and for example, it is suppressed that the driver misunderstands that there is an abnormality other than an abnormality in tire air pressure.

Next, the effect of this embodiment will be described.
(1) When the tire pressure is abnormal, the second abnormality notification assist control is executed only when the vehicle 1 is accelerated or decelerated, so that the influence on the steering feeling due to the abnormal tire pressure is naturally emphasized. This makes it easier for the driver to easily recognize that the tire pressure is abnormal, so that the driver can easily recognize the abnormality in the tire pressure.

  (2) Since the magnitude of the assist force applied to the steering system is changed by executing the first and second abnormality notification assist control according to the magnitude of the acceleration α of the vehicle 1, the tire pressure of the tire 1 is more natural. The influence on the steering feeling due to the abnormality is emphasized, and the driver can more easily recognize the abnormality of the tire pressure.

In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, the tire air pressure relationship in the left-right direction is expressed as the sum of the tire air pressure values Pa, Pc of the left wheels 2a, 2c and the sum of the tire air pressure values Pb, Pd of the left wheels 2b, 2d. Judgment was made based on the magnitude relationship. However, the present invention is not limited to this. For example, the tire air pressure values Pa and Pb of the wheels 2a and 2b as the front wheels may be multiplied by a predetermined coefficient to increase the influence of the tire air pressure values Pa and Pb on the magnitude relationship. Further, for example, the wheel side showing the smallest value among the tire air pressure values Pa to Pd may be set to the smaller tire air pressure, and the determination of the relationship between the tire air pressures can be changed as appropriate.

  In the above embodiment, even if the tire air pressure is abnormal, when the basic assist control amount Ib is zero, the second abnormality notification assist control is performed only when the absolute value of the acceleration α is equal to or greater than the predetermined acceleration α0. Was executed. However, regardless of the magnitude of the acceleration α, for example, a sensor for detecting whether or not the brake pedal or the accelerator pedal is operated is provided, and when the brake pedal or the accelerator pedal is operated based on a signal from this sensor, (2) Anomaly notification assist control may be executed. That is, it may be determined whether or not the vehicle 1 is in acceleration / deceleration based on the operation of the brake pedal or the accelerator pedal.

In the above-described embodiment, a value obtained by differentiating the vehicle speed SPD is used as the vehicle acceleration α. However, the present invention is not limited to this, and for example, an acceleration detected by a longitudinal G sensor or the like may be used.
In the above embodiment, the absolute value of the compensation assist control amount Ic may be calculated so as to increase nonlinearly as the absolute value of the acceleration α increases. Also. The compensation assist control amount Ic may be constant regardless of the magnitude of the acceleration α of the vehicle 1.

  In the above embodiment, the first abnormality notification assist control is executed when the tire air pressure is abnormal and the basic assist control amount Ib is not zero. However, the present invention is not limited to this. For example, the absolute value of the acceleration α is the predetermined acceleration α0. Otherwise, the first abnormality notification assist control may not be executed. In this case, both the first and second abnormality notification assist controls correspond to the abnormality notification assist control.

  In the above embodiment, when it is determined that the tire air pressure is abnormal, the second abnormality notification assist control is executed at the time of acceleration / deceleration of the vehicle 1. However, the present invention is not limited to this. Only the second abnormality notification assist control may be executed.

  In the above embodiment, the assist force is applied so that the vehicle 1 is deflected in either the left or right direction when the first abnormality notification assist control is executed. However, the present invention is not limited to this. For example, when the first abnormality notification assist control is executed, the compensation assist control amount Ic that periodically changes with a small amplitude is superimposed on the basic assist control amount Ib to finely adjust the steering wheel 4. The assist force may be applied while generating vibration. The point is that the assist to be applied at the time of execution of the first abnormality notification assist control can be appropriately changed as long as it is different from the assist force to be applied at the time of execution of the normal assist control.

  In the above embodiment, when there is almost no difference between the tire air pressures in the left and right directions, compensation assist control such as turning the wheels 2a and 2b in a predetermined direction, for example, when executing the second abnormality notification assist control. The amount Ic may be calculated.

  In the above embodiment, the ECU 23 controls the operation of the steering force assisting device 22 (EPS3) that applies assist force using the motor 21 as a drive source. However, the present invention is not limited to this, and for example, steering that applies assist force based on hydraulic pressure. The operation of the force assist device may be controlled.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2a-2d ... Wheel, 3 ... EPS, 4 ... Steering wheel, 21 ... Motor, 22 ... Steering force auxiliary device, 23 ... ECU, 31 ... Vehicle speed sensor, 41 ... Microcomputer, 42 ... Drive circuit, 43 ... Current command value calculation unit, 44: motor control signal output unit, 51: basic assist calculation unit, 52: compensation assist calculation unit, 61: air pressure detector, Pa to Pd: tire air pressure value, α: acceleration.

Claims (2)

In a control device for a power steering device that controls the operation of a steering force assist device that applies assist force to a steering system,
If it is determined that the tire air pressure is abnormal based on a signal from an air pressure detector that detects the tire air pressure of the wheel, the vehicle is moved in the left-right direction only when the vehicle is accelerating or decelerating. A control apparatus for a power steering apparatus, which performs abnormality notification assist control for applying an assist force so as to be deflected to any of the above. The control device for a power steering device according to claim 1,
A control device for a power steering apparatus, wherein the magnitude of assist force applied to the steering system is changed by executing the abnormality notification assist control in accordance with the magnitude of vehicle acceleration detected by an acceleration detector. .