Closed Loop Velocity Control of H-Bridge Driven Valves

摘要

The present invention is a methodology that is used by H-bridge driven valves to dynamically control the valve velocity and duty cycle. The algorithm combines the feedforward and closed loop control methodology lo move the valve to desired position by controlling valve velocity. Based on how far the valve is from desired position, desired velocity is calculated (1). Open loop feedforward duty cycle of the valve is determined based on the desired velocity. Stiction duty cycle is added to the feedforward duty cycle which determines the open loop velocity correction (2). Valve velocity is measured to determine the velocity error, and proportional and integral duty cycles react to eliminate that error in the system. Integral term is limited and reset when the valve reaches the desired position to prevent any windup (3). Total duty cycle applied to the valve is the sum of open and closed loop velocity correction, i.e. stiction, feedforward, proportional and integral duty cycles (4). With dynamic voltage control, the system can overcome mechanical friction more easily, and thus, can also tolerate greater part to part variations. Furthermore, since the valve duty cycle is dynamically adjusted, it eliminates the need for voltage compensation caused by fluctuations in motor voltage.