Convegni ATI - Accesso riservato soci CTI

Autore: R. Amirante, A. Innone, L.A. Catalano

Collana: CA - 63 - Palermo 2008

Note:
This paper presents an innovative open-loop control technique for direct single-stage hydraulic proportional valves, whose response rate is significantly higher than that obtained by standard open loop control techniques, and even comparable to more
costly commercial closed-loop systems. Differently from standard open loop techniques, which provide the coil with a constant current, proportional to the target position, the control strategy proposed in this paper employs the Peak and Hold (P&H) technique, widely used in Diesel engine modern supply systems, to boost the duty cycle value of the Pulse Width Modulation (PWM) signal for a short time, namely during the spool displacement, while maintaining a lower duty cycle for holding the spool in the required opening position. The developed “boosted PWM” technique only requires a low cost microcontroller, such as a Peripheral Interface Controller (PIC), equipped with a Metal Oxide Semiconductor (MOS) power driver. The PWM parameters are calibrated as function of the spool displacement so as to maximize the response rate without introducing overshoots: the collected data are stored in the PIC.