JPH0536252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a constant speed traveling device for automobiles, commonly called autodrive or speed control.

A constant-speed vehicle is a device that automatically controls the vehicle speed and maintains it at a constant speed without having to press the accelerator pedal when the desired vehicle speed is set during driving. Alternatively, the control valve coil of the negative pressure actuator that drives the accelerator link using vacuum pump negative pressure, etc. as a power source is set to A device is known that is driven by a pulse signal with a corresponding duty ratio.

[Conventional technology]

Conventionally, the calculation of the duty ratio DU (%) according to the difference between the detected vehicle speed and the target vehicle speed described above is calculated using the following formula, where the detected vehicle speed is XN, the target vehicle speed is XA, the set duty ratio is SD, and the control speed width is VB. was required by.

DU=[(XA-XN)/VB]+SD...(1) However, 0≦DU≦100 Here, the set duty ratio SD is set at the design stage as a duty ratio that allows constant speed driving at a certain vehicle speed, for example, 80 km/h. The control speed width VB refers to the width of the vehicle speed difference in which the output duty ratio changes, and is also a fixed value determined at the design stage.

The solid line in FIG. 8 is a diagram showing an example of the vehicle speed difference vs. output duty ratio characteristic defined by the above equation (1), and the control speed width VB and set duty ratio SD are expressed as shown.

[Problem that the invention seeks to solve]

Incidentally, the set duty ratio SD is determined at the design stage as described above, but due to the characteristics of the actuator, variations in the driving force of the vehicle, etc., it is not possible for each vehicle to always obtain the desired actual vehicle speed with the set duty ratio SD. There is no guarantee that it will be possible. The same applies when the running resistance varies due to changes in the road surface. In such a case, the vehicle is driven at a speed where the vehicle speed difference and the output duty ratio DU are balanced. That is, for example, if the set duty ratio SD is too small, the vehicle will run at a constant speed with a deviation of ΔXN as shown at point P in FIG.

As a method to reduce such steady-state deviation, the control speed width is changed to VB as shown by the dotted line in Figure 8.
Therefore, the control gain can be increased by increasing the control gain by decreasing VB', or by increasing the differential correction coefficient in a system that incorporates differential correction of vehicle speed into the control. In this way, the balance point becomes P as shown in the figure.
to P′, and the steady-state error becomes small to ΔNX′.
However, increasing the control gain in this way causes the following problems.

That is, under normal conditions, the output of a vehicle speed sensor used in a constant speed vehicle running system changes smoothly as shown in characteristic 70 in FIG. 9, and therefore the output duty ratio also changes as shown in characteristic 71 in the same figure. Although the range of change is small as shown in Figure 10, if the mounting part of the vehicle speed sensor is loose, the output of the vehicle speed sensor will be modulated as shown in characteristic 80 in Figure 10, and accordingly. As shown in characteristic 81 in the same figure, the output duty ratio also has a variation range (maximum value).
DUMAX−minimum value DUMIN) becomes large and control stability is impaired.

The present invention has been made in view of these circumstances, and its purpose is to increase the control gain to increase control accuracy when it is considered that the vehicle speed sensor is maintained within normal accuracy. It is an object of the present invention to provide a constant speed traveling device for an automobile that can switch to control that emphasizes stability in rare cases where a vehicle speed sensor becomes abnormal.

[Means for solving problems]

In order to achieve the above object, the present invention includes an output duty ratio calculation means 1 which calculates an output duty ratio according to the difference between a detected traveling vehicle speed and a preset set vehicle speed, as shown in FIG. 1, for example. , generates a pulse signal having a duty ratio corresponding to the output duty ratio calculated by the output duty ratio calculating means 1 to drive the control valve coil 2a in the throttle valve driving actuator 2 which uses engine negative pressure as a power source. In the constant speed driving device for an automobile, the driving means 3 includes: a change range calculation means 4 for calculating a change range of the output duty ratio calculated by the output duty ratio calculation means 1;
and a control gain modification means 5 for modifying the control gain in the output duty ratio calculation of the output duty ratio calculation means 1 according to the change width of the output duty ratio calculated by the change width calculation means 4.

[Effect]

When the vehicle speed sensor that calculates the detected vehicle speed maintains normal accuracy, the range of change in the output duty ratio is small as shown in FIG. The control gain for ratio calculation is corrected to a larger side to improve control accuracy, and when the vehicle speed sensor becomes abnormal and the range of change in the output duty ratio increases as shown in Figure 10, the control gain is corrected to a smaller side. Ensure control stability.

〔Example〕

FIG. 2 is a block diagram of essential parts of an embodiment of the present invention.

In the figure, 10 is a reed switch for detecting the speed of an automobile, and 11 is a permanent magnet rotated by a speedometer cable. The reed switch 10 turns on and off as the permanent magnet 11 rotates, and generates a pulse signal having a frequency proportional to the vehicle speed. This pulse signal is converted into a DC voltage having a level proportional to the vehicle speed in a frequency-voltage conversion circuit (F/V conversion circuit) 12. F/V conversion circuit 1
The output voltage of 2 is held in the memory circuit 14 when the analog switch 13 is on. The set voltage held in the memory circuit 14 is input to the differential amplifier 15, where the difference between it and the output voltage of the F/V conversion circuit 12, that is, the running vehicle speed is determined. This difference signal is converted into a digital quantity by the A/D converter 16 and then input to the input port of the microcomputer 17. The microcomputer 17 generates a pulse signal having an output duty ratio according to the difference signal, and when the AND circuit 26 is open, the pulse signal passes through the AND circuit 26 and controls the actuator 19 via the amplifier 20. It is added to the valve coil 19i.

The actuator 19 includes a control valve 19a and a release valve 19b, and the control valve 19a is connected to the amplifier 2.
Opening/closing is controlled by a control valve coil 19i that is excited with an output of 0. When the control valve coil 19i is energized, the atmospheric pressure from the port 19c is cut off and the intake pipe negative pressure from the port 19d is introduced into the chamber 19e, and when the energization is cut off, the negative pressure from the port 19d is introduced. is shut off and atmospheric pressure is supplied to chamber 19e from port 19c.
to be introduced. The release valve 19b is controlled to open and close by a release valve coil 19j driven by the output of the self-holding circuit 22 via the amplifier 21. When energized, the release valve 19b shuts off atmospheric pressure from the port 19f, and when energization continues, this shuts off. Atmospheric pressure is introduced into chamber 19e. By controlling the pressure in the chamber 19e as described above, the diaphragm 19g moves, which causes the rod 19 connected to the accelerator link (not shown) to move.
h is moved in its axial direction, and as a result, the opening degree of the throttle valve is controlled.

Further, an AND circuit 25 is provided which receives the output of the set switch 23 and the output of the high-speed limiter circuit 24, and the output of the AND circuit 25 closes the analog switch 13 and presets the self-holding circuit 22. When the self-holding circuit 22 is preset, the AND circuit 26 is opened and the release valve coil 19b is energized through the amplifier 21, so that traveling control becomes possible. The high-speed limiter circuit 24 closes the AND circuit 25 when it receives a chime signal indicating that the vehicle has reached a high speed of, for example, 100 km or more, thereby preventing the set vehicle speed from being memorized. Further, the cancel switch 28 is
This is a switch that resets the self-holding circuit 22, and when reset, the self-holding circuit 22 stops energizing through the amplifier 21. Residence switch 27
is used to restart the constant speed driving control that was interrupted by the cancel switch 28. When this button is pressed, the constant speed driving control is performed using the originally set vehicle speed as the target value. In addition, the constant speed limiter circuit 29
is for forcibly resetting the self-holding circuit 22 when the vehicle speed drops to 30 km or less, for example.

FIG. 3 is a flowchart showing an example of the output duty ratio calculation/output processing executed by the microcomputer 17, and FIG. 4 is a flowchart showing an example of the control width changing processing executed by the microcomputer 17.
The operation will be explained below.

The microcomputer 17 executes steps S2 to S10 for calculating the output duty ratio shown in FIG. 3 at predetermined intervals (S1). This process is
First, read the difference (vehicle speed difference) between the output of the A/D converter 16, that is, the detected vehicle speed XN, and the target vehicle speed XA stored in the memory circuit 14 (S2), and then calculate the current output duty ratio DU using the following formula. (S3).

DU = [(XA - It is variable and defined as VB'=VB+ΔVB. In addition,
VB is a fixed control speed width set in advance, and is, for example, 10 km/h.

After calculating the current output duty ratio DU in step S3, the microcomputer 17 sends a pulse signal having a duty ratio equal to the calculated duty ratio from the output port to the AND circuit 26 (S4).

Next, the microcomputer 17
Maximum value of output duty ratio DU in S5 to S7
DUMAX is updated, and the minimum value DUMIN of the output duty ratio DU is corrected in steps S8 to S10.

In addition, the microcomputer 17 may, for example,
By executing the process shown in FIG. 4 each time, the control speed width VB' used for calculating the output duty ratio is corrected. That is, each time a correction period arrives,
First, change width of output duty ratio DUB (DUMAX
-DUMIN) is a predetermined value, for example, 10% or more (S20), and if it is above, add a predetermined value α, for example, 1 Km/h to ΔVB (S24), and if it is less than the predetermined value α. Subtract (S21). Also, the updated ΔVB is 0≦ΔVB≦MAX (MAX is, for example, 10Km/
h) (S22, S23, S25,
S26). Then, the ΔVB obtained this time is a fixed value.
The speed control width used to calculate the output duty ratio in step S3 in Figure 3 by adding it to VB.
Find VB′ (S27). Further, for the next calculation of ΔVB, a new DUB is obtained using the formula DUMAX-DUMIN (S28), and DUMAX and DUMIN are initialized to 0 (S29).

In this embodiment, as described above, the speed control width VB' for calculating the output duty ratio is corrected every predetermined period based on the change width DUB of the output duty ratio, and in the normal state where DUB is smaller than the predetermined value, the speed Since the control width VB' is reduced and the control gain is increased, control accuracy can be improved, and the vehicle speed may be reduced due to loosening of the mounting part of the vehicle speed sensor consisting of the permanent magnet 11 and reed switch 10 shown in FIG. When an abnormal situation occurs, such as when the signal is modulated, DUB increases, so a correction is made to increase VB', and the control gain is lowered, making stable control possible although the control accuracy is somewhat degraded.

In the above embodiment, the control gain was changed by making the speed control width variable, but in a system that incorporates differential correction of vehicle speed into control, the control gain can be changed by making the differential correction coefficient variable. can.

The hardware configuration of the embodiment for correcting the control gain using this differential correction coefficient can be almost the same as the configuration shown in FIG. 2, but the F/V The difference is that the output of the conversion circuit 12 is input to the microcomputer 17 via the A/D converter 16.

The software processing of the microcomputer 17 includes the processing shown in Fig. 5 as the processing corresponding to Fig. 3, the processing shown in Fig. 6 as the processing corresponding to Fig. 4, and the processing shown in Fig. 7 as the processing corresponding to Fig. 4. Add processing.

The difference between the processing in Fig. 5 and Fig. 3 is that, before calculating the output duty ratio DU in step S3, the detected vehicle speed XN' is calculated using the following equation (S11 ).

XN _' = XN _i + K' ₍ XN _{i −} This is a correction coefficient. Note that the calculation of XN _i -XN _i-1 in the above equation (3) is performed, for example, every 200 mssc by the process shown in FIG.

Another difference is that the output duty ratio DU is calculated in step S3 of FIG. 5 using the following equation.

DU=[(XA-XN')/VB]+SD...(4) Furthermore, in the process of Figure 6 which corresponds to Figure 4, the above
K' in equation (3) is corrected as follows. That is, the microcomputer 17 first changes the output duty ratio change width DUB every 1 second, for example.
It is determined whether (DUMAX−DUMIN) is a predetermined value, for example, 10% or more (S30), and if it is, ΔK
A predetermined value α, for example, 0.7 is added to (S34), and if it is less than, the predetermined value α is subtracted (S31). Further, the updated ΔK is limited so that 0≦ΔK≦MAX (MAX is, for example, 4) (S32, S33, S35, S36). Then, by subtracting the ΔK obtained this time from the fixed value K (for example, 7), the steps in Fig. 5 can be performed.
Determine the differential correction coefficient K′ used in S11 (S37). Also, for the next ΔK calculation, DUMAX−DUMIN
Find a new DUB using the formula (S38),
Initialize DUMAX and DUMIN to 0 (S39).

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various other additions and changes are possible. For example, the present invention is also applicable to a system in which a plurality of pre-fixed set duty ratios are provided for each target vehicle speed.

〔Effect of the invention〕

As explained above, according to the present invention, the control gain is modified according to the range of change in the output duty ratio calculated by the output duty ratio calculating means, and when the range of change in the output duty ratio is less than or equal to a predetermined range. If the vehicle speed sensor is considered to be maintained within normal accuracy, the control gain is increased to improve control accuracy, and a vehicle speed sensor whose output duty ratio change range exceeds a predetermined range becomes abnormal. In this case, the control gain is lowered and the control is switched to one that emphasizes stability, which has the effect of providing a high-performance constant-speed vehicle traveling device.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of the present invention, FIG. 2 is a block diagram of main parts of an embodiment of the present invention, and FIG. 3 is a flowchart showing an example of output duty ratio calculation/output processing executed by the microcomputer 17. 4 is a flowchart showing an example of speed control width processing executed by the microcomputer 17, FIG. 5 is a flowchart showing another example of output duty ratio calculation/output processing executed by the microcomputer 17, and FIG. 6 is a flowchart showing another example of the output duty ratio calculation/output processing executed by the microcomputer 17. 7 is a flowchart showing an example of the differential correction coefficient changing process executed by the microcomputer 17, FIG. 8 is a flowchart showing an example of the detected speed difference calculation process executed by the microcomputer 17, FIG. 1 is a diagram showing an example of the state of the output duty ratio when the vehicle speed sensor is normal, and FIG. 10 is a diagram showing an example of the state of the output duty ratio when the vehicle speed sensor is abnormal. In the figure, 1 is an output duty ratio calculation means;
2 is an actuator, 2a is a control valve coil, 3 is a driving means, 4 is a variation width calculation means,
5 is a control gain correction means, 10 is a reed switch, 11 is a permanent magnet, 12 is a frequency-voltage conversion circuit, 13 is an analog switch, 14 is a memory circuit,
15 is a differential amplifier, 16 is an A/D converter, 17 is a microcomputer, 19 is an actuator,
19a is a control valve, and 19i is a control valve coil.

Claims (1)

[Claims] 1. Output duty ratio calculation means for calculating an output duty ratio according to the difference between the detected traveling vehicle speed and a preset set vehicle speed; and an output duty ratio calculated by the output duty ratio calculation means. and a driving means for driving a control valve coil in a throttle valve driving actuator using engine negative pressure as a power source by generating a pulse signal having a duty ratio according to the output. a change width calculation means for calculating a change width of the output duty ratio calculated by the duty ratio calculation means; and an output duty ratio of the output duty ratio calculation means according to the change width of the output duty ratio calculated by the change width calculation means. 1. A constant speed traveling device for an automobile, comprising: control gain correction means for correcting a control gain in calculation.