JPH0218163A - Detecting device for controlled variables in duty control system - Google Patents

Abstract

PURPOSE:To enable the actual controlled variable corresponding to the duty value at the time to be detected regardless of change in the actual value of a control object by determining the detection timing depending on the duty value at the time, and thereby detecting the actual value of the control object at the timing. CONSTITUTION:A switch-over valve 7 switching hydraulic pressure to be applied to a power cylinder 9 is provided with a reaction hydraulic pressure chamber 19 exerting reaction against the movement of a spool 8, and the magnitude of hydraulic pressure in the reaction hydraulic pressure chamber 14 is determined based on the quantity of hydraulic oil supplied through a variable throttle valve 23 driving solenoid drive means 29 and the quantity of hydraulic oil discharged out through a fixed throttle 31. The solenoid drive means 29 is controlled in duty by an electronic control circuit 32 based on the output from a vehicle speed sensor 33 and a lateral acceleration sensor 34. In this case, actual current energizing a solenoid 30 is detected by the timing determined based on the magnitude of a duty value at the time, electric energy turned onto the solenoid 30 is thereby controlled by means of a feedback operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a duty control system applied to control the excitation current of a solenoid in a power steering system for an automobile. The present invention relates to a controlled variable detection device for detecting an actual controlled variable of a controlled object such as.

(Prior Art) In order to enable stable driving in a power steering device for a vehicle, it is required that the steering force be light when driving at low speeds and appropriately heavy when driving at high speeds. In this case, it is necessary to prevent the steering force from becoming light during high-speed driving due to a failure in the control system or the like.

Therefore, the present applicant previously proposed a vehicle speed-responsive power steering device equipped with a fail-safe function (Japanese Patent Application No. 73141/1982). In the power steering device, the hydraulic pressure within the hydraulic reaction chamber that applies a steering reaction force to the steering wheel is controlled by a variable throttle. The variable diaphragm is controlled by a solenoid drive means that changes the opening degree of the diaphragm so as to increase the hydraulic pressure in the hydraulic reaction chamber as the excitation current of the solenoid becomes smaller. Then, the excitation current of the solenoid is controlled according to the vehicle speed, and
When the excitation current exceeds a set range, the solenoid is demagnetized.

In such a power steering device, when the excitation current of the solenoid becomes larger or smaller than the set current due to a failure in the control system, etc., the solenoid is demagnetized, so the oil pressure in the hydraulic reaction chamber is forcibly increased.
Steering force becomes heavier. Therefore, in the event of a failure in the control system or the like, the steering force will always be heavy regardless of the vehicle speed, and a failsafe will be activated.

In this way, in the case of this power steering device,
In order for the failsafe to work, it is necessary to detect the excitation current actually flowing through the solenoid. Furthermore, in order to perform feedback control on the excitation current supplied to the solenoid, it is necessary to detect the actual excitation current.

By the way, the power supply used in automobiles is a constant voltage power supply, so when controlling the excitation current of a solenoid in this way, the current value is not directly changed, but the energization time within a certain period, that is, the duty value. It is often controlled by changing the For example, as shown in FIG. 6(A), the duty period T is 5.
When the power is turned on for 0% of the time, that is, the duty value is set to 0.
．． 5, the current I supplied to the solenoid is approximately 50% of the constant current I0. Further, if the duty values are set to 0.7 and 0.3, as shown in FIGS. 10B and 2C, the electric current supplied to the solenoid becomes approximately 70% and 30%, respectively. By adopting such duty control, electronic control using a microcomputer or the like becomes possible.

However, when performing such duty control,
The current to be controlled does not immediately reach a predetermined value even when the duty is turned on or off. In particular, when a solenoid is energized, its self-inductance causes a large time delay in the change in current. Therefore, the current that actually flows through the solenoid becomes a sawtooth wave as shown by the thin line in FIG.

When the excitation current of a solenoid is duty-controlled in a power steering device having a fail-safe function as described above, the current that actually flows through the solenoid changes from moment to moment, so it is necessary to actually measure the current value. becomes difficult. For example, as shown by the imaginary line in Figure 6, if the actual current is detected at a certain time t0 within the duty period T, the rising waveform of the current will be almost the same in either case. , if the detection timing is within the duty-on time, the detected value i3 will always be approximately constant. As a result, the failsafe may malfunction or the current may not be accurately controlled.

Therefore, conventionally, when obtaining the actual measured value of such duty-controlled current, etc., the waveform was smoothed through a smoothing circuit, and then the current, etc. was detected.

(Problems to be Solved by the Invention) However, in order to smooth the waveform to the extent that the detection error falls within an allowable range, it is necessary to increase the values of the capacitance and resistance of the smoothing circuit. If the capacitance and resistance are increased in this way, the rise of the measured current, etc. will be slow, and the responsiveness of the control system will be reduced. Therefore, the waveform cannot be smoothed very much, and there is a problem in that the detection error inevitably increases.

The present invention has been made in view of these problems, and its purpose is to enable accurate detection of the actual control amount of a controlled object subject to duty control without any time delay. That's true.

(Means for Solving the Problem) In order to achieve this object, in the present invention, the timing control means determines the detection timing according to the duty value at that time, and the actual value of the controlled object is detected at the detection timing. I try to do that.

Preferably, the detection timing is when the duty-on time is divided within a certain ratio when the duty value is larger than a predetermined value, and when the duty-off time is divided within a fixed ratio when the duty value is smaller than the predetermined value. Ru.

(Operation) The actual value of the duty-controlled controlled object changes monotonically within the duty-on time and the duty-off time. Therefore, for example, if the detection timing is set to 1/2 of the duty-on time and the actual value is detected at that detection timing, the detected value will be large when the duty value is large, and the detected value will be small when the duty value is small. . That is, a detected value corresponding to the control amount of the controlled object is obtained.

In that case, if the detection timing is always set within the duty-on time, the detection error may become large when the duty-on time is short, that is, when the duty value is small. Therefore, if the detection timing is set within the duty off time when the duty value is small, accurate detection values can always be obtained.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

In the drawings, FIG. 1 is a hydraulic circuit diagram showing an example of a power steering device to which the present invention is applied, and FIG. 2 is a block diagram of its electronic control circuit.

As is clear from FIG. 1, in this power steering device, the rotation of the steering handle 1 is transmitted to the pinion gear 3 via the steering shaft 2. The pinion gear 3 is supported by a pinion holder 4 whose rotation center is eccentric from the rotation center of the pinion gear 3, and is meshed with a rack portion 6 of a rack rod 5. Therefore, when the steering handle 1 is rotated, the pinion gear 3 rotates and attempts to move the rack rod 5 in the axial direction, and a reaction force in the axial direction of the rack rod 5 is applied to the pinion gear 3, causing the pinion holder 4 to rotate. It is designed to rotate around the center. As the pinion holder 4 rotates, the spool 8 of the switching valve 7 is moved in the axial direction.

A power cylinder 9 is provided on the rack rod 5 at an extension of the rack portion 6. The power cylinder 9 is
A piston 10 integrally provided to the rack rod 5 divides the hydraulic chambers into a pair of left and right hydraulic chambers 11 and 12. The hydraulic pressure introduced into these hydraulic chambers 11 and 12 is
It is designed to be switched by a switching valve 7.

The switching valve 7 includes a boat 13 communicating with one hydraulic chamber 11 of the power cylinder 9, a boat 14 communicating with the other hydraulic chamber 12 of the power cylinder 9, a refueling boat 16 communicating with a hydraulic power source 15 consisting of a hydraulic pump, and Four boats are provided: an oil drain boat 18 connected to an oil tank 17. Then, by moving the spool 8, the refueling boat 1
6 communicates with one boat 13, and the oil drain boat 1
8 communicates with the other boat 14, a position where the refueling boat 16 communicates with the other boat 14 and an oil drain boat 18 communicates with one boat 13, and a middle position in between. It has become.

In this way, when the steering handle 1 is rotated, the spool 8 moves and the switching valve 7 is switched, and the rack rod 5 is driven in the axial direction by the power cylinder 9. ) is now steered.

A reaction hydraulic chamber 19 is provided around the switching valve 7 to provide a reaction force against movement of the spool 8. The reaction hydraulic chamber 19 is formed between a pair of reaction plungers 21, 21 which are urged in directions away from each other by a spring 2°. The tip of the plunger 21.21 is adapted to engage a pin 22.22 fixed to the spool 8. In this way, the spool 8 is always urged toward the neutral position by the hydraulic pressure introduced into the reaction hydraulic chamber 19 and the spring force of the spring 20.

Pressure oil from the hydraulic source 15 is introduced into the reaction hydraulic pressure chamber 19 via a variable throttle valve 23 . The variable throttle valve 23 is configured to throttle the space between the inlet boat 24 and the outlet boat 25 by an annular groove 27 formed on the outer peripheral surface of the spool 26, and when the spool 26 moves to the right in the figure, the throttle valve The aperture opening increases, and when moving to the left, the aperture opening decreases.

The spool 26 is always urged rightward by a spring 28. Further, the spool 26 is moved to the left by a solenoid drive means 29. The solenoid driving means 29 is configured to move the spool 26 to the left in proportion to the excitation current of the solenoid 30. Therefore, the throttle opening degree of the variable throttle valve 23 is controlled by the exciting current of the solenoid 30.

Furthermore, the reaction hydraulic pressure chamber 19 communicates with the oil tank 17 via a fixed throttle 31. therefore,
The magnitude of the oil pressure in the reaction hydraulic pressure chamber 19 is determined by the amount of oil supplied through the variable throttle valve 23 and the amount of oil discharged through the fixed throttle 31, and increases as the throttle opening of the variable throttle valve 23 increases. . Accordingly, the steering reaction force applied to the steering wheel 1 also increases.

Such a hydraulic circuit is disclosed in the above-mentioned Japanese Patent Application No. 62-73141.
It is the same as that of No.

The excitation current of the solenoid 30 in the solenoid drive means 29 is controlled by an electronic control circuit 32. As shown in FIG. 2, a vehicle speed signal detected by a vehicle speed sensor 33 and a lateral acceleration signal detected by a lateral acceleration sensor 34 are input to the control circuit 32.

In the control circuit 32, the waveform of the pulsed vehicle speed signal is shaped by a waveform shaping section 35, and then guided to a vehicle speed pulse calculation section 36, where a vehicle speed value V is calculated. and,
The vehicle speed value V is guided to a map search section 37 and a failsafe detection section 38. On the other hand, the lateral acceleration signal is converted into a digital signal in the A/D converter 39, and after being set as a lateral acceleration value G, is guided to the map search section 37 and the failsafe detection section 38.

The output signal from the map search section 37 is sent to the current value comparison section 40.
The output signal from the comparison section 40 is guided to the solenoid drive section 42 via the control current setting section 41.

Further, the output signal from the failsafe detection section 38 is guided to the failsafe drive section 43 and the solenoid drive section 42.

A power supply circuit that supplies current from a battery 45 to the solenoid 30 via an ignition switch 44 is provided with two transistors in series: a solenoid control transistor 46 and a fail-safe transistor 47. These transistors 46 and 47 are turned on and off by a solenoid drive section 42 and a failsafe drive section 43, respectively. Therefore, the solenoid 30 includes these transistors 46.4.
It is energized only when both 7 are on. The fail-safe transistor 47 is normally maintained in a conductive state.

The actual current flowing through the solenoid 30 is detected by a current detector 48 which is a detection means.

The current value 8 detected at the timing determined by the timing control section 49 is guided through the A/D conversion section 39 to the failsafe detection section 38 and the current value comparison section 40, respectively. A signal from the control current setting section 41 is input to the timing control section 49 .

In the map search unit 37, a target current value I as shown by a solid line in FIG. 3 is set in advance for each vehicle speed value V and lateral acceleration value G, and the vehicle speed value input at that time is
According to the lateral acceleration value G, the target current value ■ is searched on a map and output. The target current I is
The larger the vehicle speed V, the smaller the value, and the larger the lateral acceleration G, the smaller the value.

On the other hand, the fail-safe current value (■) is set in advance in the fail-safe detection section 38. As shown in FIG. 3, when the vehicle speed V is greater than the predetermined vehicle speed Vt, the current value is a value that is α much larger than the upper limit value of the target current value at that time; , when α2 is smaller than the upper limit value of target current I at that time.
The value is set to be α larger than the lower limit value of the target current {circle over (2)} at that time. And at that time A
When the measured current 1 of the solenoid 30 inputted through the /D converter 39 exceeds the fail-safe signal 2, that is, when it falls within the shaded area in FIG. 3, it is determined that there is a failure in the control system. A fail-safe signal is output from the fail-safe detection section 38.

Here, α,.

α2. The value of α3 is determined in consideration of noise margin and the like.

In the control current setting section 41, depending on the difference between the target current value I at that time and the actual solenoid current value ■8,
A time T for energizing the solenoid 30 within a certain duty cycle T. Hl, that is, the duty value is determined.

Then, the time T is determined by the solenoid drive unit 42. H
only when the solenoid control transistor 46 is turned on. That is, the excitation current of the solenoid 30 is duty-controlled.

Next, the operation of the electronic control circuit 32 configured as described above will be explained according to the flowchart shown in FIG.

When the ignition switch 44 is turned on, the control flow starts. First, in step S1, the control circuit 32 is initialized.Next, in step s2, the vehicle speed value V is calculated by counting and averaging the vehicle speed pulse signals from the vehicle speed sensor 33. This calculation is performed by the vehicle speed pulse calculation section 36. Further, in step S3, the lateral acceleration sensor 3
4, the lateral acceleration value G is measured.

In step S4, the map search unit 37 performs a map search for the target electrical work based on the values of the vehicle speed V and lateral acceleration G obtained in this way.

On the other hand, in step S, the energization time TON set in the control current setting section 41 at that time is the predetermined value 71,
For example, a comparison is made to see if it is greater than 0.5T. When the energization time ToN is larger than the predetermined value T, the current actually flowing through the solenoid 3o is read at the timing of ToNX a / b in step s6. Further, when the energization time ToN is smaller than the predetermined value T1, in step St, the current (3) actually flowing through the solenoid 30 is To-s+ (T Tos) X a ' / b
' will be loaded at the timing of '. Here, a/b and a'/b' are positive constants smaller than 1 that are appropriately windowed by the rising waveform of the solenoid current I3. In this way, the energization time T. N, that is, when the duty value is larger than the predetermined value Tr, the solenoid current I3 is detected at the time when the energization time T'os is internally divided by a fixed ratio a/b, and when the duty value is smaller than the predetermined value Tl, the solenoid current I3 is detected. The solenoid current (3) is detected at the time when the energization time T-ToN is internally divided by a fixed ratio a'/b'. Such determination of detection timing is performed by the timing control section 49.

Next, in step S8, the control current setting unit 41 sets the next solenoid energization time T based on the difference between the actual solenoid current value I8 and the target current value I detected in this manner. N is determined. And step S
At step 9, the solenoid control transistor 46 is turned on by the solenoid driving section 42 for the energization time TON determined in this way.

In the fail-safe detection unit 38, first, in step S+o, the vehicle speed V at that time is compared with a predetermined vehicle speed vI. Then, the vehicle speed ■ is the predetermined vehicle speed V! When the actual solenoid current Is is larger than the current fail-safe current IP in step S1□
A comparison is made to see if it is smaller than =I+α1.

If ≦I+01, it is determined to be in the normal range, so
In step 812 the Nl register is set to zero. If Is>I+α1, the area is a fail-safe area, so the Nl register is incremented in step 513.

On the other hand, when the vehicle speed V at that time is smaller than the predetermined vehicle speed vl, fail-safe areas are set above and below the target current I, so in step S14, it is determined whether the actual solenoid current 6 is in the normal area or not. That is, it is determined whether or not the range is I-α3≦15≦1+02. If it is within that range, the N2 register is set to zero in step srs.

Further, when Is>I+α2 or Is<I−as, the N2 register is incremented in step SIR.

Further, in step S17, the value of the Nl register is compared with the constant m, and in step 818, the value of the N2 register is compared with the constant n.

When the values of the Nl register and the N2 register are smaller than m and n, respectively, the process returns to step s2 and the following control flow is repeated. Further, the abnormality detection in step 813 is repeated m times in succession,
When the value of the Nl register becomes m or more, or when the abnormality detection in step 15111 is repeated once and the value of the N2 register becomes n or more, it is determined that there is a failure in the control system, and the process proceeds to step 819. A failsafe signal is output. This fail-safe signal is guided to the fail-safe drive unit 43, whereby the fail-safe transistor 47 is cut off. At the same time, a failsafe signal is sent to the solenoid drive unit 42.
The solenoid control transistor 46 is also cut off. Therefore, the solenoid 30 is demagnetized at that time. The values of the constants m and n are determined as margins for noise, time delay of the solenoid current I3, and the like.

In this way, in this control system, the solenoid 3
The control current that excites 0 is the conduction time of the solenoid control transistor 46, that is, the conduction time T of the solenoid 30. Controlled by N. Therefore, the current that actually flows through the solenoid 30 becomes a sawtooth wave as shown by the thin line in FIG. And that solenoid 3
The actual current value I3 flowing through o is the energization time T. When N is larger than the predetermined value T1, the energization time T. The point in time when N is internally divided by a certain ratio a/b, i.e. T. Nxa
Detected at timing /b. As a result, Figure 5 (A
), (B), the detected current value Is
becomes larger as the energization time TON becomes longer. Therefore, a current value corresponding to the current actually supplied to the solenoid 30 is detected.

Also, the energization time T. When N is shorter than the predetermined value T,
As shown in FIG. 5(C), the non-energizing time, that is, the duty-off time T-TON, is set at a constant ratio a'/b.
The detection timing is determined at the time of internal division by '. Even during the duty-off time, a gradually decreasing current flows through the solenoid 30, and the current value remains constant during the energization time Tos.
Since the current value changes according to the current value, even in this case, the current value 8 corresponding to the current actually supplied to the solenoid 30 will be detected.

By doing so, the detection timing is set within the longer duty-off time, which facilitates the setting and allows accurate detection values to be obtained. In this case, the energization time is T. If N becomes even shorter, the detected current value at the set detection timing becomes almost zero, but when the energization time TON is short, the current actually flowing through the solenoid 30 becomes almost zero, so there is no problem at all.

In this way, the actual solenoid current I is always accurately detected, and the current 3 is fed back to the current value comparison section 40 to perform feedback control of the solenoid excitation current. At 38, abnormality diagnosis of the control system is performed. As a result, the excitation current of the solenoid 30 is accurately controlled according to the vehicle speed V and the lateral acceleration G, and the optimum steering force for the current driving is applied to the steering wheel 1. When it flows, the solenoid 30 is demagnetized due to a failure in the control system, etc.
Failsafe will work reliably.

Furthermore, since the actual current value Is flowing through the solenoid 30 is accurately detected, it is possible to prevent the failsafe from operating during normal operation.

In the above embodiment, the coefficients a/b and a'/b' that determine the detection timing are constant, but they may be changed depending on the energization time TON, that is, the duty value. can. Moreover, it can also be changed according to other conditions such as the temperature of the solenoid 30.

Furthermore, although the application to the control system of a power steering device has been described, the present invention is not limited to this, and can be applied to any case where the actual control amount of a controlled object subject to duty control is detected. can do. In such a case, the object to be controlled is not limited to current, but may be voltage, the amount of movement of an object, or the like.

(Effects of the Invention) As is clear from the above description, according to the present invention, the detection timing is determined according to the duty value at that time,
Since the actual value of the controlled object is detected at that detection timing, even though the actual value of the controlled object changes from moment to moment, it is possible to detect the actual controlled amount according to the duty value at that time. It becomes possible. Furthermore, when the control amount changes, the corresponding detected value is immediately obtained, so there is no time delay. therefore,
Accurate control becomes possible.

In addition, by setting the detection timing within the duty-on time when the duty value is large, and setting the detection timing within the duty-off time when the duty value is small, it is easier to set the detection timing, and the control amount is more accurate. detection becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an example of a power steering device to which the present invention is applied, FIG. 2 is a block diagram of an electronic control circuit in the power steering device, and FIG. 3 is a hydraulic circuit diagram showing an example of an electronic control circuit in the power steering device. Figure 4 is a flowchart showing the control flow of the control circuit, and Figure 5 shows the current that actually flows through the solenoid under the control of the control circuit and its detected value. FIG. 6 is an explanatory diagram for explaining problems in detecting the actual value of duty-controlled current. ■... Target current ■,... Solenoid current (actual value) T... Duty cycle Tos... Energization time (duty value) T,... Predetermined value 23... Variable throttle valve 32...・Electronic control circuit 34...Lateral acceleration sensor 9...Reaction hydraulic chamber O...Solenoid 3...Vehicle speed sensor 7...Map search section 8...Fail safe detection section 1...Control current Calibration section 6... Solenoid control transistor 7... Fail-safe transistor 8... Current detector (detection means) 9... Timing control section (timing control means) Patent applicant Honda Motor Co., Ltd.

Claims (2)

[Claims] (1) A controlled variable detection device used in a duty control system that controls a controlled object by changing the duty value within a certain period; the timing for determining the detection timing according to the magnitude of the duty value at that time. A controlled variable detection device in a duty control system, comprising: a control means; and a detection means for detecting an actual value of the controlled object at a detection timing determined by the timing control means. (2) When the duty value is larger than a predetermined value, the timing control means divides the duty-on time at a fixed ratio, and when the duty value is smaller than the predetermined value, the duty-off time is divided at a fixed ratio. The controlled variable detection device according to claim 1, wherein the control amount detection device determines a detection timing.