JPH0314671B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is an electronic control system for power steering that controls steering force in response to vehicle speed. The present invention relates to a vehicle speed sensor abnormality determination method for an electronic power steering control system.

(Prior art) Conventionally, in steering force control that is sensitive to vehicle speed and achieved through program control using a microcomputer, hydraulic pressure is applied to the power steering mechanism according to a predetermined steering force control pattern based on the vehicle speed detected by a vehicle speed sensor. The amount or pressure of the fluid supplied by the pump is varied, and if the vehicle speed sensor breaks down due to disconnection or the like, the ability to control the steering force according to the vehicle speed will be lost.

Therefore, as shown in the flowchart in Figure 1,
After controlling the steering force based on the vehicle speed in block a, first calculate the speed difference between the previous vehicle speed and the current vehicle speed, which are detected at regular intervals, and compare it with a constant value. If an abnormality such as short occurs, the speed will suddenly change, so when the speed difference exceeds a certain value, judgment block b determines that the vehicle speed sensor is abnormal, and the process moves to fail-safe processing in block c, which changes the vehicle speed of the power steering. The control system responds to this by stopping the control, alerting the driver, and fixing the steering force to an intermediate value within the range variable by power steering control.

On the other hand, if the vehicle speed sensor fails while the vehicle is stopped, since the vehicle speed is zero from the beginning, it is not possible to determine whether the vehicle speed sensor is abnormal in the process of determination block b. Therefore, if the speed difference is below a certain value in discrimination block b, discrimination block d
Then, it is determined whether the vehicle speed is zero or not. If the vehicle speed is zero, the vehicle stopping condition of determination block e is determined.

The determination of this stopping condition differs between manual transmission vehicles (MT vehicles) and automatic transmission vehicles (AT vehicles).
If the clutch is engaged, the gear is in a position other than neutral, and the brake is not pressed, the vehicle is determined to be running. Since the vehicle speed is zero even if the vehicle speed sensor is running, it is determined that the vehicle speed sensor is abnormal and the process proceeds to block c fail-safe processing.

In addition, the stopping conditions for an AT vehicle are that the gear position is in a position other than parking or neutral, the parking brake is released, and the brake is not pressed. If the condition is not satisfied, the vehicle is determined to be in a stopped state, and since the vehicle speed is zero even though it is running, it is determined that the vehicle speed sensor is abnormal, and the system similarly moves to the fail-safe process of block c. .

This dual determination of sudden changes in vehicle speed and stopping conditions when the vehicle speed is zero makes it possible to determine any abnormality in the vehicle speed sensor and reliably execute fail-safe operation, resulting in high reliability.

However, with such conventional vehicle speed sensor abnormality determination methods, when an AT vehicle performs a so-called creep stop in which it stops on an uphill slope with a gear in the drive range, the vehicle speed is Even though it is zero, it is determined that the gear position, which is one of the driving conditions, is in a position other than neutral or parking and the vehicle is running, and the vehicle speed sensor is stopped due to creep stop even though the vehicle speed sensor is normal. There was a problem in that the steering force was determined to be abnormal and shifted to fail-safe processing, and due to the malfunction of the fail-safe processing, the steering force became much heavier than it would normally be.

(Purpose of the Invention) The present invention has been made in view of these conventional problems, and aims to improve the reliability of abnormality determination by preventing erroneous vehicle speed sensor abnormality determination during creep stop of automatic transmission vehicles. An object of the present invention is to provide a vehicle speed sensor abnormality determination method for an electronic power steering control system.

(Structure of the Invention) To achieve this object, the present invention provides a vehicle speed sensor abnormality determination method comprising the following steps.

In other words, the speed difference between the current vehicle speed detected at regular intervals and the previous vehicle speed is detected, and when this speed difference is greater than a predetermined value, it is determined that the vehicle speed sensor is abnormal and the process proceeds to fail-safe processing. If the vehicle speed is below the value, it is then determined whether the vehicle speed is zero or not. If the vehicle speed is zero, the vehicle stop condition is determined, and if it is not determined that the vehicle has stopped, the vehicle is stopped again after a certain delay time has elapsed. The stopping condition is determined, and if the stopping condition is not obtained even after this re-judgment, it is determined that the vehicle speed sensor is abnormal and the process proceeds to the above-mentioned fail-safe process.

(Embodiment) FIG. 2 is an explanatory diagram showing the device configuration of an electronic power steering control system in which the vehicle speed sensor abnormality determination method of the present invention is implemented, taking an automatic transmission vehicle as an example.

First, to explain the configuration, 1 is a controller with a built-in microcomputer that executes control based on a power steering control program that applies light steering force at low speeds based on the detected vehicle speed and increases steering force as the vehicle speed increases. do. For the controller 1, there is a vehicle speed sensor 2 that detects the vehicle speed.
The vehicle speed sensor 2 is a non-contact type sensor that combines a magnet rotated by a speedometer cable and a reed switch, and a pulse signal with a frequency proportional to the vehicle speed is sent to the controller 1. Enter. Therefore, in the controller 1, the gate is opened by the pulse signal from the vehicle speed sensor 2, and the clock pulses are counted.
This count value is detected as the vehicle speed.

Furthermore, an inhibitor switch 3, a stop lamp switch 4, and a parking brake switch 5 are connected to the controller 1 in order to detect vehicle stop conditions. The switch contact closes when it is in the position, and turns off when it is in a position other than neutral or parking. The stop lamp switch 4 closes the switch contact when the brake pedal is depressed, and lights up the stop lamp 6. Furthermore, the parking brake switch 5 is turned on by operating the parking brake.

7 is a battery and fusible link 8
A battery voltage is supplied through an ignition switch 9, and the output side of the ignition switch 9 is divided into two systems with power fuses 10 and 11. Battery voltage is supplied from the power fuse 10 side to the controller 1, and battery voltage is supplied from the power fuse 11 side to an alarm lamp 12 that lights up when the controller 1 detects an abnormality in the system. Further, the ground side of the controller 1 is connected to the negative side of the battery 7, and is further provided with a self-diagnosis switch 13 for opening a switch contact in order to externally display the diagnosis result of the self-diagnosis function of the controller 1. The self-diagnosis switch 13 consists of a removable connector that connects the controller 1 and the ground side of the battery 7, and the self-diagnosis switch 13 can be activated by manually disconnecting the connector.
I am trying to get the function as.

Next, a power steering drive system driven by the controller 1 will be explained. 14 is a hydraulic pump, 15 is a tank, and 16 is a power steering drive unit incorporated in a steering mechanism using a steering wheel 17. The hydraulic pump 14 and the power steering drive unit 16
A flow control section 18 is further provided in parallel with the power steering drive section 16, and the flow control section 18 includes a linear solenoid 19 driven by the output of the controller 1.
A flow rate control valve 20 whose opening degree is varied by the flow rate control valve 20 and a constant flow rate control valve 21 which controls the pressure difference between the front and rear of the flow rate control valve 20 to be kept constant are provided. The flow rate from the hydraulic pump 14 to the drive unit 16 is bypassed, and the steering force in the power steering drive unit 16 is variably controlled.

Next, refer to the flowchart in Figure 3 and proceed to the second step.
An embodiment of a method for determining abnormality of a vehicle speed sensor in the system configuration shown in the figure will be described.

First, as is clear from the flowchart in FIG. 3, the program processing of the vehicle speed sensor abnormality determination method of the present invention includes a first determination routine 30 for determining a sudden change in vehicle speed, and a first determination routine 30 for determining a sudden change in vehicle speed. a second determination routine 40 that determines the condition; a delay processing routine 50 that determines the stop condition again after a certain period of time delay when an abnormality of the vehicle speed sensor is determined in the determination routine 40; and a first determination routine 30. Alternatively, the fail-safe processing routine 60 is executed based on abnormality determination in the delay processing routine 50.

Next, the abnormality determination method will be explained in detail according to the flowchart shown in FIG.

When the ignition switch 9 is turned on, power is supplied to the system and the system becomes operational. First, in block a, the linear solenoid 19 is driven so as to obtain a steering force based on the vehicle speed Vn detected at that time by the vehicle speed sensor 2, and the flow control valve 20
The flow rate to the power steering drive section 16 is determined by adjusting the amount of bypass, and then, in block b, a timer used in the delay processing routine 50 is initialized, and the flow proceeds to the first determination routine 30.

In this determination routine 30, the current vehicle speed Vn is first read in block c, and since the previously detected vehicle speed V _o-1 has already been obtained, the current vehicle speed Vn and the previous vehicle speed V _o are determined in determination block d. _-1
The absolute value of the difference |Vn−V _o-1 | is calculated, and the calculated speed difference is compared with a predetermined value ΔV.

At this time, if the vehicle speed sensor 2 is normal, there is no rapid change in speed exceeding the predetermined value ΔV, so the process proceeds to block e of the second determination routine 40, and since the vehicle has started traveling and the vehicle speed Vn is not zero, Then, the process returns to block f, replaces the current vehicle speed Vn with the previous vehicle speed Vo _-1 , and returns to the process of block a again. Thereafter, the above-described process is repeated at every fixed program cycle.

Next, if the vehicle speed sensor has a failure such as disconnection or shot while the vehicle is running, the vehicle speed becomes zero and a speed difference exceeding the predetermined value ΔV occurs in the determination block d. Then, proceed to block g to check whether the stop lamp switch 4 is on or off, and if the stop lamp switch 4 is off, it is determined that the vehicle speed sensor 2 is abnormal because there is no sudden change in speed due to sudden braking. The process then proceeds to the failsafe processing routine 60.

In the fail-safe processing routine 60, first, control by the controller 1 is stopped at block h, and
Next, in block i, the warning lamp 12 is turned on to notify the driver of a system failure, and then the process proceeds to block j, where the linear solenoid 19 is turned on so that the steering force is at the middle value within the range of the steering force varied by the controller 1. A fail-safe operation is performed so that a constant current is applied and a constant steering force, which is an intermediate value, is obtained regardless of the vehicle speed.

Next, if the vehicle speed sensor 2 fails while the vehicle is stopped, the vehicle speed will always be zero regardless of whether the vehicle is stopped or running, and the first determination routine 30 cannot determine whether the vehicle speed sensor is abnormal. I can't do it,
The process proceeds from the judgment block d to a judgment block e of the second judgment routine 40, where it is judged that the vehicle speed Vn=0.
Next, in decision blocks k, l, and m, the states of the stop lamp switch 4, inhibitor switch 3, and parking brake switch 5 are checked in sequence, and since all switches are off while the vehicle is running, delay processing is performed. Proceed to routine 50.

In the delay processing routine 50, first, in block n, a time delay of a certain period of time, for example, about 30 seconds, is executed by counting by a timer, and when the certain period of time has elapsed, in the judgment block o, the inhibitor switch 3 is switched on as in the second judgment routine 40. , the stop lamp switch 4, and the parking brake switch 5 are determined again, and if there is no change in the switch status and it is determined that the vehicle is still running,
It is determined that the vehicle speed sensor is abnormal, and the process moves to a fail-safe processing routine 60, in which control of the controller 1 is stopped, an alarm is issued by the warning lamp 12, and a fail-safe operation is performed in which the steering force is fixedly set at an intermediate value.

Next, a description will be given of a determination process when a so-called creep stop is performed, in which the vehicle is stopped while the vehicle is in the drive range on an uphill slope.

In this creep stop, vehicle speed Vn=
Since it is 0, the routine proceeds to the second determination routine 40, where Vn=0 is determined in determination block e, and presence or absence of a stop condition is determined in determination blocks k, l, and m.
At this time, since it is a creep stop, the brake is not pressed, the stop lamp switch 4 is off, and since the vehicle is in the drive range, the inhibitor switch 3 is also off, and since the parking brake is not operated, the parking brake switch 5 is turned off. is also off. As a result, it was determined that the car was running even though it was creep-stopped.
The process moves to a delay processing routine 50.

In the delay processing routine 50, a fixed time delay is performed at block n, and after, for example, 30 seconds have elapsed, the second determination routine 4 is executed again at determination block o.
The state change of the discrimination blocks e and k to m at 0 is determined.

At this time, if the vehicle that has not stopped due to creep stop starts before the fixed delay time of block n has elapsed, then the vehicle speed sensor 2
Since is normal, the vehicle speed Vn is greater than zero,
Since there is a change in the state, the process returns to the first determination routine 30 again, reads the vehicle speed Vn when starting from the creep stop, compares the difference between the previous vehicle speed and the current vehicle speed in determination block d, and determines a predetermined value. Since Vn is greater than or equal to ΔV, the process proceeds to determination block e, and since Vn is greater than or equal to zero in determination block e, the current vehicle speed Vn is changed to the previous vehicle speed V _o-1 in block f.
, and returns to the power steering control of block a again.

In this way, even if the second determination routine 40 determines that the vehicle speed sensor is abnormal due to creep stop, as long as the vehicle restarts within a certain delay time in the delay processing rune 50, the process can proceed to fail-safe processing. Instead, by setting the delay time in the delay processing routine 50 to an appropriate time that exceeds the creep stop time during normal driving, such as when waiting at a traffic light, fail-safe operation can be performed by erroneously determining that the vehicle speed sensor is abnormal due to the creep stop. This will definitely prevent it from being put away.

(Effects of the Invention) As described above, according to the present invention, there is a process for determining an abnormality in the vehicle speed sensor based on a sudden change in vehicle speed, and a process for determining an abnormality in the vehicle speed sensor by detecting the running state when the vehicle speed is zero. In addition to the double determination process with Even if a vehicle speed sensor is incorrectly determined to be abnormal during a creep stop, the same determination is made again after a certain period of time has elapsed since the creep stop, so if the vehicle starts during this delay time, the fault may be detected due to a faulty vehicle speed sensor. Abnormality determination is prevented, the erroneous recognition rate of vehicle speed sensor abnormality determination processing for transitioning to fail-safe operation is significantly reduced, and highly reliable vehicle speed sensor abnormality determination can be performed.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a conventional method, FIG. 2 is an explanatory diagram showing the device configuration of an electronic power steering control system in which the present invention is used, and FIG.
The figure is a flowchart showing an embodiment of the abnormality determination method according to the present invention. 1: Controller, 2: Vehicle speed sensor, 3: Inhibitor switch, 4: Stop lamp switch,
5: Parking brake switch, 6: Stop lamp, 7: Battery, 8: Fusible link, 9: Ignition switch, 10, 11:
Power fuse, 12: Alarm lamp, 13: Self-diagnosis switch, 14: Hydraulic pump, 15: Tank,
16: Power steering drive unit, 17: Steering wheel, 18: Flow rate control unit, 19: Linear solenoid, 20: Flow rate control valve, 21: Body flow rate control valve, 3
0: first discrimination routine, 40: second discrimination routine, 50: delay processing routine, 60: failsafe processing routine.

Claims (1)

[Claims] 1. The vehicle speed is detected at regular intervals by a vehicle speed sensor, the speed difference is calculated from the current and previous vehicle speeds, and when the speed difference is greater than a predetermined value, fail-safe processing is performed, and the speed difference is When the vehicle speed is below the predetermined value, it is determined whether the vehicle speed is zero, and when it is determined that the vehicle speed is zero, a predetermined stopping condition for the vehicle is determined, and the stopping condition is obtained by determining the stopping condition. If the stopping condition is not obtained again after a certain delay time, the stopping condition of the vehicle is determined again, and if the stopping condition is not obtained again in the re-judgment of the stopping condition of the vehicle, the electronic device is characterized in that the electronic apparatus moves to the fail-safe process. A method for determining vehicle speed sensor abnormality in a power steering control system.