"A Hydraulic Control Valve for PWM Actuation at 400 Hz"
, in D N Johnston, K A Edge: Power Transmission and Motion Control - PTMC 2006, Seite(n) 373-385, 9-2006, ISBN: 08-6197-135-3
A Hydraulic Control Valve for PWM Actuation at 400 Hz
Sprache des Titels:
Power Transmission and Motion Control - PTMC 2006
The concept of switching converters known from the control of electrical drives can also be applied to hydraulic control systems. A number of such concepts relies upon the pulse width modulation (PWM) of an actuator pressure by a periodically switching valve. In order to keep the good dynamic properties of valve controlled drives, the PWM frequency has to be much higher than the typical eigenfrequency of the driven mechanical system. Therefore, two major problems arise.
Firstly, the pressure variations induced by the periodic switching of the consumer ports between the high and the low system pressure port have to be decoupled both at the supply side and at the consumer side to prevent excessive noise propagation and high frequency actuation of the driven mechanical system.
And secondly, the switching valve has to be very fast compared to commercially available products. Furthermore, the power available for the actuation of this valve
is limited in order to keep the energetic benefits provided by the switching control.
In this paper, a novel valve design is presented. A prototype with a flow rating of 100 l/min at 5 bar pressure drop has been built and successfully tested. The basic design is that of a 3/3 directional control valve, with a constant high pressure supply port and a constant low pressure supply port both equipped with hydraulic
accumulators. The third port is pulse width modulated between the low and the high pressure port at a frequency of approximately 400 Hz. The so called duty-cycle, i. e. the relative connection time to high pressure within one PWM period is controllable between 0 and 100 % during the PWM operation allowing for the control of a connected consumer. Besides some details on the design of this valve, the paper shows simulation results regarding the use of the prototype in a hydraulic switching converter.