JPH0348079A - Control device for hydraulic actuator - Google Patents

Abstract

PURPOSE:To set control of a control valve to a given value by providing means which varies the control characteristics of a control means based on respective results produced by sampling a signal value from a converting means when a pulse current is fed to a solenoid and the voltage value of a power source for feeding a pulse current to the solenoid at a given period. CONSTITUTION:The voltage value of a power source 16 is sampled an intervals of a given period, and a sampling value is set to a source voltage value. In forced rising of a plowing device, a current value available when a pulse current having a given pulse width is fed to a solenoid 12a is inputted through a converting means C, and from the current value and a determined source voltage value, the value of an impedance is determined. Thereafter, from the value of the impedance, the characteristics of a flow rate, i.e. control characteristics, in relation to a duty cycle is selected.

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.

[Prior Art] Conventionally, as a device that uses an electromagnetic proportional control fill valve as a control means, there is a device shown in Japanese Patent Application Laid-Open No. 63-308225, and in this reference, the pressure of hydraulic oil is controlled by this control valve. The hydraulic clutch is configured to soften the shock when the hydraulic clutch is engaged and operated.

[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 hydraulic oil pressure is adjusted by adjusting the current value is that, as shown in the above cited example, the electromagnetic proportional control valve adjusts the pressure in proportion to the value of the electromagnetic force generated in the solenoid. This is because since the degree of opening is determined, it was necessary to adjust the current value (not the voltage value) 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
Supply current in the form of pulses without controlling the current value, and adjust the relationship between period and pulse width (e.g. PWM, PFM, etc.)
It is also possible to adjust the voltage value of the current supplied to the solenoid by using fdl? With wholesale products, the current value changes due to fluctuations in either the solenoid impedance (AC resistance value) or the voltage value of the power supply. If the impedance of the solenoid changes, or if the power supply voltage value drops, the current value corresponding to the predetermined pulse width or pulse period will change.
There is room for improvement in this type of current control system.

Incidentally, recent control devices are often equipped with microprocessors, and in particular, in control devices equipped with microprocessors like this, it is easy to change the pulse width or pulse period of the pulse signal simply by changing the software (program). Since it is possible to construct a system that can be adjusted to the desired value, controlling the control valve with a pulsed current leads to further reduction in cost, as described above.

An object of the present invention is to rationally configure a system that controls the current value by adjusting the relationship between the period and pulse width of the pulse current supplied to the electromagnetic proportional control valve, even when the impedance of the solenoid changes. Another object of the present invention is to provide a device that can accurately set the opening degree of the electromagnetic proportional control valve to a required value even if the power supply voltage changes.

[Means to solve the problem]

The features of the present invention include a driving means for supplying a pulse current to a solenoid of electromagnetic proportional control, a conversion means for converting the pulse current supplied to the solenoid into a voltage value proportional to the current value of the pulse current, A solenoid drive system includes a control means for adjusting the relationship between the period and pulse width of the pulse current in order to maintain the current value of the pulse current supplied to the solenoid at a predetermined value based on the voltage signal of the conversion means. and the signal value from the conversion means when the pulse current is supplied to the solenoid, and the voltage value of the power supply that supplies the pulse current to the solenoid are sampled at a predetermined period. The present invention includes a correction means for changing the control characteristics of the control means, and its functions and effects are as follows.

[For production]

If the above characteristics are configured as shown in FIGS. 1 and 2, and the operation is set as shown in the flowchart of FIG. 5, the power supply (16) voltage value is sampled at every predetermined period, The sampling value is set to the power supply voltage value (E) (steps 1112 and 1113), and in this configuration, when forcibly raising the tiller (8), a pulse current with a predetermined pulse width is supplied to the solenoid (12a). The current value (1) is inputted via the conversion means (C), and this current value (1) and the voltage value (E) obtained as described above are
The value of impedance (Z) is calculated from (#5, #
From the value of this impedance (Z), it is possible to select the flow rate characteristics for the duty cycle, that is, the control characteristics (steps #I4 and #15).

The characteristics of this flow rate are as shown in Figure 3, when the duty cycle (in %) is set on the horizontal axis and the flow rate (in cc/5ec) is set on the fir axis. (a)
, (b), (c)... It is possible to draw multiple types of graphs, and when the current voltage is lower,
Alternatively, if the solenoid (12a) has a higher impedance, the right side of the graph is selected.

[Effect of the invention] Therefore, regardless of whether the valve is driven by pulse current, even if the impedance of the solenoid of the electromagnetic proportional control valve changes,
Even if the power supply voltage changes, a device has been constructed that can set the opening degree of the electromagnetic proportional control valve to the required value and drive the actuator to the desired pressure and speed.

〔Example] Embodiments of the present invention will be described below based on 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) It has a rolling control system consisting of a solenoid valve for rolling control (4) and a hydraulic cylinder for rolling (5), and the surplus flow from the flow priority valve (3) is controlled by an electromagnetic proportional ff1lJ control valve (1/). This lift hydraulic cylinder (6) (an example of a hydraulic actuator) drives a pair of left and right lift arms (7), and this lift arm (7), a pair of left and right links (9) that connect and support the tilling device (8) are supported in a suspended state via a pair of left and right lift rods (10), and the pair of lift rods (
The rolling hydraulic cylinder (5) is interposed in one of the IQ).

Further, the electromagnetic proportional control valve (V) is a first valve for upward control (
11), a second valve (12) 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 current to the solenoid (12a) of the valve (12) and adjusting the current value, the second valve (
12) changes the pilot pressure in accordance with this current value, and as a result, the opening degree of the first valve (11) changes in proportion to the pilot pressure, controlling the flow rate of pressure oil from the hydraulic pump (2). In addition, when controlling the lift arm (7) in the downward direction, the solenoid t" of the fourth valve (14)
By supplying current to (14a) and adjusting the current value of this current in the same manner as described above, the fourth valve (14)
The opening degree of the third valve (13) changes in response to changes in the pilot pressure from the hydraulic cylinder (6), making it possible to control the flow rate of hydraulic oil flowing out from the hydraulic cylinder (6).

Further, in this agricultural tractor, the solenoid (12a)
, (14a) is configured as shown in FIG.
It is configured to supply a pulse current to the solenoids (12a) and (14a), and to adjust the current value supplied to the solenoids (12a) and (14a) by adjusting the duty cycle of this pulse current. Furthermore, in the control system of the hydraulic actuator installed in agricultural tractors,
The voltage value of the power source (16) fluctuates depending on the driving speed of the dynamo (not shown), and the voltage value of the solenoid (12a)
.

This change occurs because the impedance of (14a) changes due to the influence of the oil temperature of the hydraulic oil, causing a phenomenon in which the current value of 2A flowing through the solenoids (12a) and (14a) changes in response to a predetermined duty cycle. Means for correcting is also provided.

That is, this control system includes a control device (17) equipped with a microprocessor (not shown), and a first potentiometer (18) that sets the level of the tiller (8) relative to the vehicle body during position control. ) and the lift arm (7) to determine the level of the tillage device (8) relative to the vehicle body.
a second potentiometer (19) that detects the swing angle of the
A third potentiometer (20) for setting the ground level of the tilling device (8) during automatic plowing depth control, and a grounding body provided on the tilling device (8) for determining the ground level of the tilling device (8). a fourth potentiometer (21) that detects the swing angle of the vehicle (not shown), and a lift switch (22) that raises the tilling device (8) to the upper limit when the vehicle reaches a headland during work, etc. The signal from this input system is sent to an A/D converter (23).
or directly input to the control device (17).

The control device (17) also includes the solenoid (12a).
Power transistor (24a) that supplies current to (14a)
) and (24), and a pulse signal is output to this output system.

In addition, in order to obtain the current value of the current supplied to the solenoids (12a) and (14a), the solenoid (12aL(
A resistor (26) (an example of a conversion means) is interposed in the path (25) through which the current from 14a) flows, and the voltage signal obtained by the resistor (26) is transmitted to the resistor (27) and the capacitor ( After smoothing with 28), it is configured to be manually inputted to the control device (17) via the A/D converter (29), and similarly, in order to obtain the voltage value of the power source (16), the voltage of the power source is The voltage signal from the path (30) applied by
The configuration is such that the signal is input via a /D converter (29).

Further, the control device (17) is programmed to operate according to the flowchart shown in FIG.

In other words, when control is started, the power supply voltage value (E), the impedance of the solenoids (12a) and (14a) (
Z) and flow rate characteristics (Q/D) are set to initial values (
Next, the state of the rise switch (22) is determined, and if it is turned ON, a pulse current of a preset duty cycle is supplied to the solenoid (12a) of the second valve (12) 112, #3 step), 0.5
After seconds have elapsed, the current value (1) of the current supplied to the solenoid (12a) via the A/D converter (29) is input to the control device (17) (#5, #6 steno knobs), and then Solenoid (
The impedance (Z) of 12a) is determined (1I6 step), and when the tilling device (8) reaches the upper limit, the lifting operation is stopped (117 step).

In addition, if it is determined that the rise switch (22) is in the OFF state in step #2, and next to the 117 step knob, the work mode is determined, and according to the result of this determination, automatic plowing depth control, Perform either position control or rolling control (118, #9.1110 step), and when performing either automatic plowing depth control or position control among these modes, the flow rate characteristics (Q/D)
Based on this, the solenoids (12a) and (14a) are driven.

Next, the current and voltage values are sampled, and this sampled value is set as the power supply voltage value (E) (#12.
113 steps).

Next, based on the impedance (Z) obtained in step #6, the flow rate characteristics (Q/D) for the duty cycle are calculated.
), that is, the graphs (a) and (b) shown in FIG.
, (c)..., and set this selection result to the flow rate characteristic (Q/D) (steps #14 and #15), and the above operation is reset. The process is repeated until (1116 steps).

As described above, this program samples the voltage value of the power supply (16), which tends to cause relatively large fluctuations, in short cycles, and also samples the impedance value of the solenoid (12a), whose impedance value changes relatively slowly. is sampled each time the tiller (8) is raised by operating the raise switch (22), and the flow characteristics are determined from each result to ensure smooth raising and lowering of the tiller (8). .

The features of the present invention can be expressed as shown in FIG. 1, and the control means (A) adjusts the pulse width by adjusting the duty cycle. The driving means (B) is included in the program of #9 and #110 steps, and the power transistors (24) and (2).
4), the conversion means (C) is the above-mentioned resistor (26), and the correction means (D) is #14 and #15 in the flowchart.
It consists of steps.

[Another example]

4 In addition to the above-mentioned embodiments, the present invention can also use methods such as PWM and PFM to adjust the relationship between the pulse current period and pulse width, and the control means and correction means can be implemented using logic. It is also possible to configure it with hardware such as gates and comparators, and the control operation can also be performed using PI, PID.
Various methods can be adopted, such as using a hydraulic clutch as a hydraulic actuator.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[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 configuration of the device;
Figure 2 is an electrical circuit diagram of the device, Figure 3 is a graph showing flow rate versus duty cycle, Figure 4 is a hydraulic circuit diagram,
FIG. 5 is a flowchart showing the operation of the control device. (12a), (14a)...Solenoid,
(16)...TitX, (A)...control means, (B)...drive means, (C)...
・・Conversion means, (D) ・・Correction means, (V)・
...Solenoid proportional control valve.

Claims (1)

[Claims] Electromagnetic proportional control (V) solenoids (12a), (14a)
), and a conversion means (C) 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 the period and pulse width of the pulse current are adjusted based on the voltage signal of the conversion means (C) in order to maintain the current value of the pulse current supplied to the solenoids (12a) and (14a) at a predetermined value. A solenoid drive system is configured with a control means (A) that adjusts the relationship between the solenoid (12a) and the signal value from the conversion means (C) when a pulse current is supplied to the solenoid (12a)
A correction means (D) for changing the control characteristics of the control means (A) based on the respective results obtained by sampling the voltage value of the power supply (16) that supplies a pulse current to the power supply (14a) at a predetermined period; A hydraulic actuator control device comprising: