JPH0419066B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power steering control device,
In particular, the present invention relates to a power steering control device that performs feedback control so that an actual steering assist force approaches a target steering assist force.

[Prior art] The power steering control device as described above is
For example, it is disclosed in Japanese Patent Application Laid-Open No. 146473/1983.

In this power steering control device, the current supplied to the linear solenoid that adjusts the auxiliary steering force is feedback-controlled so that the auxiliary steering force has a value that corresponds to the vehicle speed. That is, an error signal is output from the vehicle speed signal and the linear solenoid energization current detection signal, and the linear solenoid is energized so that the error signal becomes zero, that is, the vehicle speed signal and the energization current detection signal match. Control the current.
Also, when the above error signal exceeds the set value,
It is assumed that an abnormality has occurred, such as the wiring to the linear solenoid being grounded, and an abnormality has occurred in the energizing current detection signal, and the power supply circuit that controls the energizing current to the linear solenoid is prevented from being damaged due to excessive current. , cut off the power to the linear isolenoid. By cutting off the current to the linear solenoid, the steering assist force is maintained at a low speed state when an abnormality occurs in the energized current detection signal.

[Problem to be solved by the invention]

In such a known device, when an abnormality occurs such as the wiring to the linear solenoid being grounded,
Although damage to the power supply circuit can be prevented, as soon as an abnormality occurs, the steering assist force is set to the state at low speeds, so if an abnormality occurs while driving at high speed, for example, the steering assist force will fluctuate rapidly. There's a problem.

[Means to solve the problem]

The present invention has been made in view of the above points, and prevents the adjustment means from being damaged by the abnormal control signal when an abnormality occurs in the detection signal, and also prevents the steering assist force from being suddenly applied. An object of the present invention is to provide a power steering control device that can prevent such fluctuations.

In order to achieve the above object, a power steering control device according to the present invention includes: an adjusting means for adjusting the steering assist force of the steering; and outputting a detection signal corresponding to the actual steering assist force adjusted by the adjusting means. a detection means for outputting a target signal corresponding to a target steering assist force of the steering wheel according to a running state of the vehicle, and detecting an actual assist steering force based on the target signal and the detection signal; a control means for outputting a control signal to the adjustment means so as to approach a target auxiliary steering force; a determination means for detecting an abnormality in the detection signal output from the detection means; The apparatus is characterized by comprising a backup means for outputting the control signal to the adjustment means based only on the target signal, regardless of the detection signal, when the detection signal is determined to be abnormal.

[Effect]

According to the above configuration, the actual auxiliary steering force is normally determined based on the detection signal corresponding to the actual auxiliary steering force and the target signal corresponding to the target auxiliary steering force output according to the vehicle running state. The auxiliary steering force is feedback-controlled so that the auxiliary steering force approaches the target auxiliary steering force. If an abnormality occurs in the detection signal during this feedback control, open loop control is executed to control the auxiliary steering force based only on the target signal, regardless of this detection signal. In this open-loop control, control is performed based only on the target signal, so control continues based on the same target signal as the feedback control that was being performed until the abnormality occurred, and sudden changes in the auxiliary steering force are avoided. It becomes possible to prevent this.

〔Example〕

Examples of the present invention will be described in detail below.

According to one embodiment of the present invention, the adjusting means for adjusting the steering assist force of the steering includes a linear solenoid that adjusts the assist steering force in accordance with an energized current, and a power supply circuit that supplies current to the linear solenoid. configured.

The control means inputs the detection signal and the target signal,
It has an error extraction means for extracting the error, and creates a control signal based on the error signal. This control signal is output to the power supply circuit, and the power supply circuit supplies the linear solenoid with a current having a magnitude corresponding to the control signal.

The linear solenoid may be one in which the energizing current is changed continuously or in multiple stages,
It may be of a duty ratio control type in which the average current is changed continuously or in multiple stages. The configuration of the power supply circuit and control means for adjusting the current flowing to the linear solenoid can be selected from known configurations depending on the type of linear solenoid.

As the detection means, a voltage drop element for current-voltage conversion can be used, which is inserted into and connected to a power supply circuit that connects the power supply circuit, the linear solenoid, and the power source.

In one embodiment, the discrimination means shares the error extraction means constituting the control means, for example, an error amplification circuit composed of an analog circuit, and includes comparison means for comparing the error signal obtained therewith with a preset reference signal. configured using However, a comparison means for comparing the detection signal and the target signal may be provided separately from the error extraction means.

In one embodiment, the backup means includes:
The control signal is configured to be obtained based only on the target signal. However, instead of using the target signal as it is, a correction signal (for example, a constant value) related to the relative difference with the detection signal may be subtracted from the target signal. Further, when the backup means is activated, it is free to provide a means for displaying this to the driver.

In addition, the above-mentioned power supply circuit, detection means, control means,
The determining means and the backup means are all constructed using analog electric circuits. However, it is also possible to have a digital computer such as a microcomputer process at least part of the content processed by these analog circuits.

Examples of the present invention will be described in more detail below.

In FIG. 1 showing a first embodiment of the present invention, reference numeral 1 is a sensor, 2 is a reference voltage characteristic generator, and the sensor 1 and the reference voltage characteristic generating circuit 2 constitute adjustment signal generating means. The sensor 1 is, for example, a vehicle speed sensor, and the reference voltage characteristic generating circuit 2 generates an adjustment voltage that changes depending on the vehicle speed. Note that it is possible to combine the reference voltage characteristic generating circuit 2 with, for example, a steering angle sensor other than the vehicle speed sensor so that the adjustment voltage can also be changed depending on the steering angle or the like.

3 is an error amplification circuit, 4 is a comparison circuit, and 5 is a triangular wave oscillation circuit, and these circuits 3 to 5 constitute a control means.

The control signal appearing at the output of the comparator circuit 4 is applied via the selection circuit 12 to the load drive circuit 6 as a power supply circuit. The load drive circuit 6 is connected to the on-vehicle battery, and the selection circuit 1 is connected to the linear solenoid 7.
A current of a magnitude corresponding to the control signal from 2 is supplied. The linear solenoid 7, like a known type, changes the opening degree of the valve by bypassing the supply flow rate from a pump (not shown) to the power steering gear box in accordance with the magnitude of the supply current. and thereby adjust the steering assist force.

The ground side of the linear solenoid 7 is connected to the car body ground via a current cable, and in that line there is a resistance (voltage effect element) 8 for changing the current and voltage.
is inserted and connected, and the voltage signal generated at the resistor 8 is amplified via the amplifier circuit 9 and given to the error amplifier circuit 3 as a measurement voltage. The resistor 8 and the amplifier circuit 9 constitute a detection means.

The selection circuit 12 is normally in a state of selecting an input so that the output signal of the comparison circuit 4 is applied to the load drive circuit 6. At this time, the error amplifier circuit 3, the comparison circuit 4, the oscillation circuit 5, the load drive circuit 6, the resistor 8, and the amplifier circuit 9 reduce the supply current of the linear solenoid 7 in order to reduce the auxiliary force in response to the increase in vehicle speed. reduce Feedback control is then performed so that the supplied current becomes a value corresponding to the vehicle speed (such that the supplied current is decreased by increasing the measured supplied current, and the supplied current is decreased by decreasing the measured supplied current).

Specifically, the output voltage of the error amplification circuit 3 changes in a manner that increases the relative difference between the adjustment signal and the measurement signal (for example, to a larger value) as the vehicle speed increases, and accordingly When the power supply current increases and the measurement signal increases, the output voltage of the error amplifier circuit 3 changes in a direction in which the relative difference decreases, and stabilizes in an appropriate balanced state.

In the comparison circuit 4, the output voltage of the error amplifier circuit 3 and the triangular wave voltage of the oscillation circuit 5 are compared. The triangular wave voltage has a constant period and a constant wave height, and a pulse train signal with a duty ratio corresponding to the magnitude of the output voltage of the error amplifier circuit 3 appears at the output of the comparator circuit 4.

When this pulse train signal is applied to the load drive circuit 6 via the selection circuit 12, the load drive circuit 6 turns on and off the power to the linear solenoid 7 in accordance with the on/off states of the pulse train signal. The linear solenoid 7 is intermittently energized, but since the period of the triangular wave voltage is selected to be sufficiently short, the opening degree of the valve is adjusted to correspond to the average value of the supplied current. In this way, the steering assist force is accurately controlled in response to adjustment signals such as vehicle speed.

According to the invention, the selection circuit 12 has the reference numeral 10,1
When an abnormality is detected, the input is cut off from the comparator circuit 4 and connected to the backup circuit means shown at 13.

Reference numeral 10 denotes a reference voltage generation circuit that generates a reference voltage for the output voltage of the error amplification circuit 3, and is composed of voltage dividing resistors and the like. The magnitude of the reference voltage is set in advance so that the relative difference between the adjustment signal and the measurement signal represented by the output voltage corresponds to the lowest value representing an abnormal state. In the embodiment, the magnitude of the reference voltage is set to a value that matches the peak value of the triangular wave voltage generated by the triangular wave oscillation circuit 5.

The reference voltage is compared with the actual output voltage of the error amplification circuit 3 in the comparison circuit 11, and when the output voltage exceeds the reference voltage, a command signal is given to the selection circuit 12 to connect the backup circuit 13 to its input. For this reason, the selection circuit 12 has two gates 12 that are opened complementary to each other, as shown in FIG.
It is composed of A and 12B.

The backup circuit 13 is configured as a comparison circuit that compares the adjusted voltage of the reference voltage characteristic generating circuit 2 and the triangular wave voltage of the triangular wave oscillation circuit 5.
Therefore, a pulse signal appears at the output of the backup circuit 13, the duty ratio of which corresponds only to the adjustment voltage and does not depend on the measurement voltage.

Thus, when the backup circuit 13 is selected in the selection circuit 12, the current supplied to the linear solenoid 7 changes in accordance with the adjustment voltage.

To summarize the function of this device, first,
If the current flowing through the linear solenoid 7 is feedback-controlled to a normal value in accordance with the vehicle speed,
Since the output voltage of the error amplification circuit 3 does not indicate an abnormality in the relative difference between the adjustment signal and the measurement signal, the selection circuit 12 maintains the state in which the output of the comparison circuit 4 is selected as an input by the comparison circuit 11. do.

During feedback control, if the ground line of the linear solenoid 7 falls to the ground without passing through the resistor 8, the measured voltage generated by the amplifier circuit 9 will have the same value as when the current supplied to the linear solenoid 7 is zero. Therefore, the output voltage of the error amplifier circuit 3 is
The supply current changes in the direction of increasing it, and as a result, the maximum current tends to continue being supplied to the linear solenoid 7.

Since the comparison circuit 11 according to the present invention switches the selection circuit 12 to the input from the backup circuit 13 at this time, the feedback control is stopped at this point. Instead, the backup circuit 13
functions to determine the current supplied to the linear isolenoid 7 in response to the adjusted voltage from the reference voltage characteristic generating circuit 2. Thus, the system is switched from closed-loop control to open-loop control, and the steering assist force continues to be controlled according to conditions such as vehicle speed without sudden fluctuations.

In the apparatus of the embodiment described above, it is easy to modify the details of the circuit means within the scope of the gist of the present invention.

For example, in the second embodiment shown in FIGS. 3 and 4, the details of the location and role of the selection circuit 12 are changed. That is, the selection circuit 12 is arranged between the output of the error amplification circuit 3 and the input of the comparison circuit 4, and selects the output voltage of the error amplification circuit 3 and the adjustment voltage of the reference voltage characteristic generation circuit 2. For this reason, the circuit includes, for example, two analog gates 12C,
12D.

Furthermore, in the first and second embodiments, a signal representing the detection of an abnormality in the comparator circuit 11 is additionally guided to the reference voltage characteristic generating circuit 2 to correct the adjusted voltage when an abnormality is detected. It's okay.

For example, as shown in FIG. 5, by connecting a normally closed switch that responds to the detection signal from the comparator circuit 11 in parallel with one of the voltage dividing resistors, the regulated voltage is corrected to decrease at a constant rate. be able to.

Note that when carrying out the present invention, the embodiments are not limited to those described in the explanation of the above-mentioned embodiments, and the suggestions mentioned in the explanation of the outline of the structure of the invention may be used as necessary within the scope of the scope of the claims. It is possible to modify the embodiment with reference to the following points.

〔Effect of the invention〕

As explained above, according to the present invention, when an abnormality occurs in the detection signal, regardless of the detection signal,
Open-loop control is performed that controls the auxiliary steering force based only on the target signal. Therefore, it is possible to prevent a control signal based on an abnormal detection signal from being output to the adjustment means, and damage to the adjustment means can be prevented.

In addition, in this open loop control, control is performed based only on the target signal, so control continues based on the same target signal as the feedback control that was being performed until the abnormality occurred.
It becomes possible to prevent sudden changes in the auxiliary steering force.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a first embodiment of the invention, Fig. 2 is an electrical wiring diagram showing details of the main parts of Fig. 1, and Fig. 3 shows a second embodiment of the invention. FIG. 4 is an electrical wiring diagram showing details of the main part of FIG. 3, and FIG. 5 is an electrical wiring diagram of the main part showing an additional modification of the first or second embodiment. DESCRIPTION OF SYMBOLS 1...Vehicle speed sensor, 2...Reference voltage characteristic generation circuit, 3, 4, 5...Error amplification circuit, comparison circuit, and triangular wave oscillation circuit forming control means, 6, 7...Load drive circuit forming adjustment means. linear solenoid, 8,
9...Resistor and amplifier circuit forming detection means, 12,1
3... A selection circuit and a backup circuit that constitute backup means.

Claims (1)

[Scope of Claims] 1. An adjusting means for adjusting the steering assist force of the steering wheel; a detecting means for outputting a detection signal corresponding to the actual steering assist force adjusted by the adjusting means; Accordingly, a target signal corresponding to the target steering assist force of the steering is output, and based on this target signal and the detection signal, the actual assist steering force approaches the target assist steering force. , a control means for outputting a control signal to the adjustment means; a determination means for determining whether the detection signal output from the detection means is abnormal; and when the determination means determines that the detection signal is abnormal; and backup means for outputting the control signal to the adjustment means based only on the target signal, regardless of the detection signal.