JPH0351590A - Controller for hydraulic actuator - Google Patents

Abstract

PURPOSE:To set the opening degree to a necessary value with high precision by converting the pulse electric current supplied into a solenoid to the smoothed voltage value and further digitizing the voltage value through the A/D conversion and adjusting the pulse width so that the pulse electric current is maintained to a prescribed value. CONSTITUTION:A control means E supplies the pulse electric current into solenoids 12a and 14a from a driving means A and drives a hydraulic actuator. The pulse electric current is converted to the voltage value which is smoothed and proportional to the electric current value by a conversion means B, and converted to the digital signal by an A/D conversion means C, and feedback- operated to the control means E. The control means E adjusts the pulse width, etc., of the pulse electric current on the basis of the data of the feedback signal. Therefore, even if the impedance of the solenoid varies, the opening degree of an electromagnetic proportional control valve can be set to a necessary value with high precision only by installing a microprocessor onto the control means.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a hydraulic actuator, and more particularly to a device for controlling a hydraulic actuator using an electromagnetic proportional control valve.

[Conventional technology]

Conventionally, there is a device that performs control using an electromagnetic proportional control valve, as shown in Japanese Patent Application Laid-open No. 63-308225.
In this reference, the control valve is configured to control the pressure of hydraulic oil to soften the shock when the hydraulic clutch is engaged.

[Problem to be solved by the invention]

Now, considering the device cited above, while it is possible to extremely precisely control the pressure of the hydraulic fluid supplied to the hydraulic actuator, in order to perform this control, the pressure of the hydraulic fluid supplied to the solenoid of the electromagnetic proportional control valve is Since the current value of the current must be controlled with high precision, a constant current power supply circuit or the like has conventionally been required to control the current value.

Incidentally, the reason why the pressure of hydraulic oil is adjusted by adjusting the current value is that, as shown in the above cited example, this electromagnetic proportional control valve operates in proportion to the value of the electromagnetic force generated in the solenoid. This is because the current value (not the voltage value) had to be adjusted in order to adjust this electromagnetic force.

However, the circuit for obtaining a constant current has a relatively large number of parts and requires highly accurate adjustment, which is disadvantageous in that it tends to increase the cost of the control device.

Therefore, from the perspective of suppressing the rise in costs, the current from the power supply to the solenoid of the electromagnetic proportional control valve is
It is also conceivable to supply the current in the form of a pulse without controlling the current value, and adjust the current value of the current supplied to the solenoid by adjusting the pulse width (for example, PWM, PFM, etc.). In the case where the current value is controlled by adjusting the pulse width, the impedance of the solenoid (
If the AC resistance (AC resistance value) changes, the current value of the current flowing through the solenoid will change even when a pulse current with a constant pulse width is supplied at a constant cycle, so there is room for improvement.

In addition, in the electromagnetic proportional control valve that controls hydraulic oil in this way,
An increase in oil temperature is an unavoidable phenomenon during work.
As the oil temperature rises, the temperature of the solenoid also rises, and as a result, the impedance of the solenoid changes according to the temperature characteristics of the conductor that makes up the solenoid.

Furthermore, recent control devices are often equipped with a microprocessor, and in particular, in such a control device equipped with a microprocessor, the pulse width of a pulse signal, etc. can be easily adjusted by simply changing the software (program). Since it is possible to construct a system, as mentioned above,
Controlling the control valve with pulsed current leads to lower costs.

An object of the present invention is to rationally construct a device that sets the opening degree of a proportional electromagnetic control valve to a required value by adjusting the relationship between the period and pulse width of a pulse current supplied to the valve. be.

[Means to solve the problem]

The present invention is characterized by a driving means that supplies a pulse current to a solenoid of an electromagnetic proportional control valve, and a drive means that supplies a pulse current to the solenoid, and a voltage value that is proportional to the current value of the pulse current and that is smoothed. a converting means for converting, an A/D converting means for converting the voltage signal of the converting means into a digital signal, and a pulse current that is digitally processed based on the signal from the A/D converting means and supplied to the solenoid. In order to maintain the current value at a predetermined value, the control means is provided for adjusting the pulse width of the pulse current, and its functions and effects are as follows.

[For production]

If the above characteristics are configured as shown in FIGS. 1 and 2, for example, when driving the hydraulic actuator (6), a pulse current from the driving means is supplied to the solenoids (12a) and (14a). Although this pulse current is in a pulsating state, it is converted by the conversion means (B) into a smoothed voltage proportional to the value of the current flowing through the solenoids (12a) and (14a). The converted digital signal is fed back to the control means (E) by the A/D conversion means (C), and the control means (B) adjusts the pulse width of the pulse current, etc. based on the data of this feedback signal. I can do it.

In other words, solenoid (12a). Since the current value of the pulse current supplied to (14a) is averaged, digitized, and fed back to the control means (E),
For example, simply by providing the control means (E) with a microprocessor, it becomes possible to easily perform calculations based on the signals fed back in this way and obtain a desired current value.

〔Effect of the invention〕

Therefore, even though the valve is driven by a pulse current, a device has been developed that sets the opening degree of the electromagnetic proportional control valve to a required value even if the impedance of the solenoid changes.

In particular, in the present invention, it is possible to include a microprocessor in the control means, and by providing the microphone port processor in this manner, the cost of the device can be reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 4 shows a hydraulic system installed in an agricultural tractor. This hydraulic system includes a hydraulic pump (2) driven by an engine (1), a flow priority valve (
3) has a rolling control system consisting of a solenoid valve for rolling control (4) and a hydraulic cylinder for rolling (5), and also directs the surplus flow from the flow priority valve (3) through a solenoid proportional control valve (v). The lift hydraulic cylinder (6) (an example of a hydraulic actuator) drives a pair of left and right lift arms (7). ) has a pair of left and right links (
9) is supported in a suspended state via a pair of left and right lift rods (■0), and the hydraulic cylinder (5) for the mouth ring is interposed in one of the pair of lift rods (IO). There is.

Further, the electromagnetic proportional control valve (V) is a first valve for upward control (
l1), a second valve (l2) that controls the pilot pressure for this first valve (11), and a third valve (13) for downward control.
), a fourth valve (14) that controls the pilot pressure for this third valve (13), and a relief valve (15). When controlling the lift arm (7) to the upward side, the second valve By supplying a current to the solenoid (12a) of the valve (12) and adjusting the current value of this current, the second valve (l2) changes the pilot pressure in accordance with this current value. The opening degree of the first valve (1l) changes in proportion to the pilot pressure, making it possible to control the flow rate of pressure oil from the hydraulic pump (2).
) to the downward side, by supplying current to the solenoid (14a) of the fourth valve (14) and adjusting the current value of this current in the same manner as described above, the fourth valve (
The third valve (l3) responds to changes in pilot pressure from the
) changes in the opening degree of the hydraulic cylinder (6).
This makes it possible to control the flow rate of hydraulic oil flowing out from the valve.

Further, in this agricultural tractor, the solenoid (12a),
The control system for the electric power supplied to the solenoids (12a) and (14a) is configured as shown in Figure 2, and this configuration does not use a constant current power source that would increase the cost.
a) by supplying a pulsed current to the solenoid (1) and adjusting the duty cycle of this pulsed current.
2a) and (14a).

That is, this power control system includes a control device (16) equipped with a microprocessor (not shown), and a first potentiometer (17) that sets the level of the tilling device (8) relative to the vehicle body during position control. ), a second potentiometer (18) that detects the swing angle of the lift arm to feed back the level of the tillage device (8) relative to the vehicle body, and the signals from these are digitized and input to the control device (16). An input system is constituted by the A/D converter (19), and the control device (16) includes power transistors (20) and (20) that supply power to the solenoids (12a) and (14a). This device has a pair of output systems, and further includes the solenoid (12
In order to find the current value of the pulsed current supplied to a) and (14a), a resistor (22) is interposed in the path (21) through which the current from the solenoids (12a) and (14a) flows. After the voltage signal obtained by the resistor (22) is smoothed by the resistor (23) and the capacitor (24) and converted into a digital signal by the A/D converter (19), the control device ( 16).

Moreover, this control device (16) operates according to the flowchart shown in FIG. 5, and when performing position control, it first performs initial setting (#1 step) and then controls the first and second potentiometers (17), (18). ) signal from (px),
(py) and calculate the deviation (ΔP) based on this signal (Steps #2 and #3).

Next, only when the absolute value of this deviation (ΔP) is larger than the value (M) set as the dead zone, the driving speed of the hydraulic cylinder (6) is calculated based on the deviation (ΔP>) (#4,
#5 step).

This driving speed is determined by the opening degree of the electromagnetic proportional control valve ff), and the current value (Io) to be supplied to any solenoid to obtain the current value and the duty cycle to obtain this current value (IO). (D) is determined and set from the duty/current characteristic (1/D), and a pulse signal is output with this duty cycle (D) (#6
, #7 step).

Next, input the current value (IR) flowing through either solenoid at this output time, calculate I0 1R = ΔI (steps #8 and #9), and use the absolute value of this (Δ■) as the dead band. From the duty cycle where ΔI=0 only when it is larger than the set value (N), the duty
Calculate the current characteristic (1/D) and set the calculation result to (1/D) (steps #10, #l1, #12).

This control continues until it is reset (step #13).

Furthermore, in this embodiment, the features of the invention can be expressed in a block diagram as shown in FIG.
) consists of the power transistors (20), (20) and step #7 of the flowchart, and is a converting means (B).
is two resistors (22), (23) and a capacitor (2
4), and the A/D conversion means (C) is an A/D converter (
19), and the control means (B) is the control device (16)
and steps 111 and #12 in the flowchart.

The driving signals at points (a), (b), and (c) of the electric circuit in Figure 3 are as shown in (a) and (b) in Figure 3, respectively.
, (c).

[Another example]

In addition to the above-described embodiments, the present invention may also use a PFM method to adjust the pulse width of the pulse current, and
The order in which the control is performed does not need to follow the flowchart described above, and the operation may be either a PI operation or a PID operation, and various implementations are possible, such as using a hydraulic clutch as a hydraulic actuator.

Incidentally, although reference numerals are written in the claims section for convenience of comparison with the drawings, the present invention is not limited to the structure of the attached drawings by such entry.

[Brief explanation of drawings]

The drawings show an embodiment of a hydraulic actuator control device according to the present invention, and FIG. 1 is a block diagram showing the structure of the device;
FIG. 2 is an electric circuit diagram of the device, FIG. 3 is a timing chart for paths a, b, and c in FIG. 2, respectively.
FIG. 4 is a hydraulic circuit diagram, and FIG. 5 is a flow chart showing the operation of the control device. (12a), (14a)...Solenoid,
(A)... Drive means, (B)... Conversion means, (C)... A/D conversion means, (E)...
...control means, ff) ...electromagnetic proportional control valve.

Claims (1)

[Claims] Solenoid (12a) of electromagnetic proportional control valve (V), (1
4a) a driving means (A) for supplying a pulsed current;
A conversion means (B) that converts the pulse current supplied to the solenoids (12a) and (14a) into a voltage value proportional to the current value of the pulse current and smoothed; An A/D conversion means (C) converts a voltage signal into a digital signal, and digital processing is performed based on the signal from this A/D conversion means (C), and the solenoid (12a
), (14a) and control means (E) for adjusting the pulse width of the pulse current in order to maintain the current value of the pulse current at a predetermined value.