KR100505718B1 - estimated vehicle speed calculation method of vehicle on ABS - Google Patents

Abstract

The present invention relates to a method for calculating an estimated vehicle body speed of an ABS vehicle which can greatly reduce its control logic while calculating an estimated vehicle body speed similar to the actual vehicle body speed.

According to an aspect of the present invention, there is provided a method for calculating an estimated vehicle body speed, comprising: (a) receiving a wheel speed detection signal from each wheel speed sensor; (b) processing the wheel speed detection signal provided in step (a) to select a maximum wheel speed; (c) low pass filtering the maximum wheel speed selected in step (b) with a predetermined cutoff frequency; and (d) calculating an estimated vehicle body speed from a waveform obtained by low pass filtering in step (c). It is made to include.

In the above-described configuration, (c) determining whether the friction coefficient of the road surface suddenly changes between the step (c) and the step (d) and (c2) the step (a) when the friction coefficient of the road surface suddenly changes. Comprising the step of calculating the estimated vehicle body speed based on the maximum wheel speed selected in may improve the stability of the braking.

Description

Estimated vehicle speed calculation method of vehicle on ABS

The present invention relates to a method for calculating the estimated vehicle body speed of an ABS vehicle, and in particular, to calculate the estimated vehicle body velocity similar to the actual vehicle body velocity, while calculating the estimated vehicle body velocity of the ABS vehicle significantly. It is about a method.

In general, a vehicle equipped with an anti-lock brake system (ABS) detects a lock tendency of a wheel from a deceleration of a wheel obtained by comparing a wheel speed with an estimated body speed, thereby adjusting a brake hydraulic pressure to thereby skid the vehicle. Is maintained near the area where the friction between the wheel and the road surface becomes a peak, and the braking distance is shortened, and the stability of the vehicle body and the steering stability are improved. For example, in this type of device, it is determined that the wheel tends to lock when wheel vibrations such as slip rate or wheel acceleration, which are decelerations to the estimated body speed of the wheel speed, reach a predetermined threshold value. Judgment is made to reduce the braking hydraulic pressure to reduce and adjust the braking hydraulic pressure.

On the other hand, when the wheel speed is handled in the frequency range while the ABS is in operation, the wheel speed has a frequency of about 15 [Hz] at most according to the adjustment of the braking hydraulic pressure and the road surface. The maximum value of the speed is taken and the body speed is estimated. Therefore, according to the conventional body speed estimation method, since a large amount of data up to 15 [Hz] has to be processed quickly, the size of the memory, that is, the ROM containing the control logic for processing it, must be large, and the computational capacity is relatively high. The problem is that a large CPU must be used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and provides an estimation method for estimating vehicle body speed of an ABS vehicle that can greatly reduce the control logic while calculating an estimated vehicle speed similar to the actual vehicle body speed. Its purpose is to.

According to an aspect of the present invention, there is provided a method for calculating an estimated vehicle body speed of an ABS vehicle, the method including: (a) receiving a wheel speed detection signal from each wheel speed sensor; (b) processing the wheel speed detection signal provided in step (a) to select a maximum wheel speed; (c) low pass filtering the maximum wheel speed selected in step (b) with a predetermined cutoff frequency; and (d) calculating an estimated vehicle body speed from a waveform obtained by low pass filtering in step (c). It is made to include.

In the above-described configuration, (c) determining whether the friction coefficient of the road surface suddenly changes between the step (c) and the step (d) and (c2) the step (a) when the friction coefficient of the road surface suddenly changes. Comprising the step of calculating the estimated vehicle body speed based on the maximum wheel speed selected in may improve the stability of the braking.

Hereinafter, with reference to the accompanying drawings will be described in detail the method for calculating the estimated vehicle body speed of the ABS vehicle according to an embodiment of the present invention.

FIG. 1 is a schematic structural diagram of an ABS control apparatus in a general AV vehicle, and FIG. 2 is a detailed structural diagram of an actuator in FIG. 1. As shown in FIG. 1, an electronic pickup type or photoelectric conversion wheel speed sensor 2a-2d for detecting the rotational speed of each wheel 1a-1d in proximity to each wheel 1a-1d of the vehicle. The wheel speed sensors 2a-2d generate signals corresponding to the rotation of the corresponding wheels 1a-1d.

The drive wheels 1a and 1b of the wheels 1a-1d are provided with an axle shaft 4 connected to the engine 6 via the differential device 5, and the differential device 5 and each drive are provided. Torque sensors 3a and 3b are provided on the axle shafts 4a and 4b connecting the wheels 1a and 1b. Here, when the vehicle to be controlled is a front wheel drive car, the drive wheels 1a and 1b become the front wheels, and in the case of the rear wheel drive, the drive wheels 1a and 1b become the rear wheels.

Torque sensors 3a and 3b are provided on the drive wheel side. Specifically, each torque sensor 3a, 3b is comprised as follows. That is, a strain gauge configured as a bridge circuit is provided on the corresponding axle shafts 4a and 4b so as to be skewed by an amount corresponding to the torsional torque of the axle shafts 4a and 4b, and this change is detected and amplified by the voltage across the bridge circuit. Then, a signal is transmitted from the torque sensors 3a and 3b on the axle shafts 4a and 4b which are being rotated through slip rings (not shown) or replaced by electromagnetic waves to the controller 11 described later.

On the other hand, brakes 7a-7d are provided on each wheel 1a-1d, and master cylinder 9 is connected to brake pedal 8 via a transmission member such as a rod. Therefore, when the brake pedal 8 is pressed with a foot, a braking pressure corresponding to the force for pressing the brake pedal 8 is generated in the master cylinder 9. Then, the braking pressure from the master cylinder 9 is adjusted by the actuator means 10 in accordance with the output from the controller 11 described later and transferred to the brake device 7. The actuator means 10 is comprised from four actuator means 10a-10d corresponding to the four wheels 1a-1d, respectively.

The controller 11 receives signals from the wheel speed sensors 2a-2d and the torque sensors 3a, 3b and performs calculation and control processing for anti skid control to generate an output signal for driving the actuator means 10. .

Next, the actuator means 10 is comprised as shown in FIG. That is, the actuator means 10 is composed of a total of four actuators 10a-10d corresponding to the brake devices 7a-7d. However, only one actuator 10a will be described here because each actuator has the same configuration. do.

A holding solenoid valve 12 is mounted in the path from the master cylinder 9 to the brake device 7a with respect to the actuator 10a, and the reservoir tank 14 and the hydraulic pressure recovery device are mounted on the brake device 7a. The pressure reducing solenoid valve 13 is mounted in the hydraulic return path from the pump 15 to the master cylinder 9. The holding solenoid valve 12 and the pressure reducing solenoid valve 13 are connected to the controller 11. The switching is performed by being energized or interrupted by the control. Reference numeral 16 denotes a motor relay for switching the connection between the motor of the pump 15 and the power supply source in accordance with the output of the controller 11.

In the above-described configuration, pressure is supplied to the master cylinder 9 by pressing the brake pedal 8 with the foot, and the braking fluid is supplied from the master cylinder 9 through the solenoid 13 for holding the actuators 10a-10d. The brake pressure flows into the brake stand 7a-7d and rises.

Here, when the decompression signal is output from the controller 11, the holding solenoid valve 12 and the depressurizing solenoid valve 13 are energized, so that the solenoid is driven. As a result, the path between the master cylinder 9 and the brake devices 7a-7d is blocked, and instead, the path between the brake device 7a-7d and the reservoir tank 14 is connected. For this reason, the braking fluid pressure in the brake devices 7a-7d flows out into the reservoir tank 14, and the braking pressure decreases accordingly. At the same time, the pump 15 is operated by driving the motor relay 16, the braking liquid flowing out to the reservoir tank 14 is returned to the master cylinder 9 at high pressure, and ready for the next control.

On the other hand, when the sustain signal is output from the controller 11 afterwards, only the solenoid valve 12 is energized, and all paths are blocked to maintain the braking pressure. In addition, when the booster signal is output from the controller 11, the power supply to the holding solenoid valve 12 and the pressure reducing solenoid valve 13 is cut off, and between the master cylinder 9 and the brake device 7a-7d. The path is connected again, so that the high pressure braking liquid returned to the master cylinder 9 and the braking liquid discharged from the pump 15 flow back into the brake devices 7a-7d, thereby increasing the braking pressure. As described above, in order to prevent the lock of the wheel, the braking pressure is adjusted by repeating the depressurization, holding and increasing pressure in accordance with the command output from the controller 11.

3 is an electrical block diagram of the control device shown in FIG. 1. As shown in FIG. 3, the controller 11 includes a microcomputer 23 having a CPU 23a, a RAM 23b, a ROM 23c, an I / O interface 23d, a wheel speed sensor 2a, and the like. Each signal from the waveform shaping circuits 20a-20d and the torque sensors 3a, 3b for outputting the output signal of -2d) into a pulse signal suitable for processing by the microcomputer 23 is output to the microcomputer 23. Power supply circuits 22 and microcomputers 23 for supplying a constant voltage to the microcomputers 23 and the like at the time of turning on the ignition switch 27, the amplifying circuits 21a and 21b as analog signals suitable for the processing of? A motor having an actuator driving circuit 24a-24d and a normally open contact 16a for supplying an output signal according to a control signal from the actuator to the actuators 10a-10d and driving the respective solenoids of the actuators 10a-10d. As a drive circuit 25 for energizing the coil 16b of the relay 16 to turn on the normally open contact 16a. It is sex.

4 is a flowchart for explaining a method for calculating an estimated vehicle body speed of an ABS vehicle according to the present invention. It is to be understood that the microcomputer 23 performs the subject unless otherwise described. As shown in Fig. 4, in step S10, the speed signal value detected from each wheel speed sensor 2a-2d is received. Next, the wheel speed is calculated by processing the speed signal values provided from the respective wheel speed sensors 2a-2d in step S14, and the maximum wheel speed is selected from the wheel speeds thus calculated. Next, in step S14, the digital low pass filtering is performed with a cutoff frequency of x, for example, a value within 1-5 [Hz], preferably 2 [Hz], and in step S16, the maximum value is obtained from the data thus obtained. The value is taken to calculate the estimated vehicle body speed.

5 is a graph showing the relationship between each wheel speed, the actual body speed and the estimated body speed calculated according to the method of the present invention during the ABS operation. First, when the microcomputer 23 performs step S10, a total of four wheel speed waveforms denoted as a, b, c and d is obtained. When step S14 is performed, the low pass filtered wheel speed waveform as indicated by e is obtained. Is obtained.

On the other hand, the waveform shown by the dotted line in Fig. 5 (waveform f) represents the actual vehicle speed, a large difference from the wheel speed waveform obtained by the method of the present invention in the state that the friction coefficient (μ) of the road surface does not change suddenly I can see that it does not.

6 is a graph showing the relationship between the wheel speed, the actual body speed and the estimated body speed calculated according to the method of the present invention when the friction coefficient of the road surface suddenly changes. As shown in Fig. 6, in a state in which the frictional coefficient mu of the road surface suddenly changes, the wheel speed (waveform e) obtained by low pass filtering does not follow the actual body speed (waveform f). As a result, although the slip becomes larger than the actual one, the braking distance may be longer due to unnecessary decompression.

Therefore, it is necessary to appropriately correct the estimated vehicle body speed, and step S18 of FIG. 4 is given for this. That is, in step S18, it is determined whether the friction coefficient mu of the road surface is suddenly changed, and the judgment in this step S18 is, for example, whether the pressure increase or decrease time of the hydraulic pressure exceeds a predetermined reference time value or wheel acceleration. It can be achieved by whether or not the value exceeds a predetermined reference value.

As a result of the determination in step S18, when the frictional coefficient mu of the road surface suddenly changes, the flow advances to step S20 to calculate the estimated vehicle body speed based on the maximum wheel speed without the low pass filtering.

The method for calculating the estimated vehicle body speed of the ABS vehicle of the present invention is not limited to the above-described embodiments, and can be modified in various ways within the range permitted by the technical idea of the present invention.

According to the method for calculating the estimated body speed of the ABS vehicle of the present invention as described above, since the body speed similar to the actual body speed can be estimated while processing a small amount of data, the size of the control logic such as the ROM and the A lower speed CPU may be employed to reduce manufacturing costs.

1 is a structural diagram of an apparatus for controlling an ABS in a general vehicle equipped with an ABS;

FIG. 2 is a detailed configuration diagram of the actuator in FIG. 1;

3 is an electrical block diagram of the control device shown in FIG. 1;

4 is a flowchart for explaining a method for calculating an estimated vehicle body speed of an ABS vehicle of the present invention;

5 is a graph showing the relationship between each wheel speed, the actual body speed and the estimated body speed calculated according to the method of the present invention during the ABS operation;

6 is a graph showing the relationship between the wheel speed, the actual body speed and the estimated body speed calculated according to the method of the present invention when the friction coefficient of the road surface suddenly changes.

Claims (2)

delete (a) receiving a wheel speed detection signal from each wheel speed sensor; (b) processing the wheel speed detection signal provided in step (a) to select a maximum wheel speed; (c) low pass filtering the maximum wheel speed selected in step (b) with a predetermined cutoff frequency; (c1) determining whether the coefficient of friction of the road surface changes suddenly; and (d) If the friction coefficient of the road surface does not change suddenly as a result of the determination in the step (c1), the estimated vehicle body speed is calculated from the waveform obtained by low pass filtering in the step (c); and calculating the estimated vehicle body speed based on the maximum wheel speed selected in b).