The impact of peak-and-hold and reverse current solenoid driving strategies on the dynamic performance of commercial cartridge valves in a digital pump/motor
Keywords:Digital hydraulics, High speed on/off valves, Pump/ Motor, Peak and Hold, Valve driving strategies
Valve dynamics play an important role in existing fluid power systems and are key enablers to a wide range of digital hydraulic systems. Varying the electrical input signal to the solenoids is used to improve the dynamic performance and response times of on–off valves by reducing the eddy currents and coil inductance. This work examines the effects of the peak-and-hold and reverse current driving strategies on the performance of two commercially available direct actuated valves, and the resulting impact on the efficiency of a digital pump/motor. An electric circuit was designed to execute the driving strategies and a single valve hydraulic test stand was assembled to perform the valve timing studies. The differential pressure across the valves was found by installing the valves between two high frequency pressure transducers, allowing the calculation of the transition and delay time of the valves. The durations of the peak and reverse voltage signals were varied over a range of 0–10 ms with a 1 ms increment. Peak voltages were between 50 and 55 V, followed by a holding voltage of 12 V. The optimum response was found at peak duration of 6–8 ms. A reverse current strategy was used to increase the decay rate of the eddy currents during a turn-off response, improving the response time. The modified peak-andhold input signal was able to improve the turn-on response time of a commercially available valve from a range of 33–55 ms to a range of 7–9 ms, while the reverse current signal was able to improve the turn-off response time from around 130 ms to a range of 16–50 ms. These valves were then tested both in simulation and experimentally on a three-piston digital pump/motor to examine the improvement of the pump/motors efficiency resulting from the improvement of the valves switching times. The improvement in valve performance resulted in significant energy savings; up to 15 and 12% in the simulation model and digital pump/motor test stand respectively.
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