The Principle of Electro – hydraulic Proportional PWM Control

February 7, 2017 · Posted in Uncategorised 

Electro-hydraulic proportional control of the core is to control the current. Analog control power output stage to the proportional valve coil current is continuous, power device power consumption, the need to install cooling devices. And PWM control power output stage is switch-type CNC Busbar structure, power consumption is small; PWM signal contains the same frequency pulse volume, without additional chatter signal, anti-interference and anti-pollution ability, short lag time, high precision; Adopt the numerical control, and the computer connection is convenient, may realize the procedure control.
Proportional electromagnet according to the size of the current to produce the corresponding electromagnetic force, which can be controlled in proportion.

busbar machine busbar machine

The use of advanced controllable PWM technology, the output circuit to produce a variable switching voltage, the power amplifier tube is only in the saturated conduction and cut-off state, so the power is low, no additional heat sink, which can increase the amplifier output switching voltage U And shorten the current rise time, so that the output response to speed up and improve the anti-jamming capability, on the other hand, the power amplifier voltage U is added to the proportional solenoid coil, the inductance of the coil to the current I into small amplitude charge and discharge fluctuations Of the alternating current signal of the DC current, play a flutter effect, can effectively reduce friction, reduce hysteresis and dead zone phenomenon, improve the sensitivity of the electromagnet. The effect of flutter busbar bending machine action depends on the frequency and amplitude of the current fluctuation. The effect is obvious when the frequency is low and the amplitude is large, but the frequency is too low and the system will be unstable when the amplitude is too large. Usually the square wave frequency is selected in the electromagnetic core without damping natural frequency of 1.2 to 2 times.
Proportional valve coil voltage waveform for a certain period, the pulse width of the rectangular wave controllable. Since the pulse period is much smaller than the spool’s response period, the spool’s motion responds only to the average of the PWM signal. The basic form of the PWM circuit is shown in Fig. The PWM signal controls the turn-on and turn-off of the switch. When the duty cycle changes from 0 to 100%, the average current I can change from 0 to the steady-state current U / RL.


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