Feedback Control of Impact Dynamnics of a Moving-Coli Actuator

A tracking feedback control method is used to enhance the throughput of a moving-coil print actuator (MovAcc). A ``double-pulse'' test is conducted to study the effect of initial conditions on actuator performance as measured by the repeatability of flight time and impact force. Experimental data presented as a family of normalized histograms show significant reduction in the flight-time and impact-force variation when feedback control is used. The controller realized using analog electronic components is a lead-lag compensator. The inputs to the controller are the actual position measurement of the MovAcc derived from an inexpensive optical sensor and a reference signal obtained from a waveform generator. The output of the controller drives a power op amp configured as a current-mode amplifier which in turn drives the MovAcc. The measured transfer function of the actuator shows the presence of higher order modes that may lead to an unstable closed-loop system. By limiting the frequency bandwidth of the closed-loop system, a Wellbehaved time response is obtained. Finally, a modified controller that allows ballistic dynamics of the MovAcc to dominate during the impact phase of the motion is shown to provide the best compromise between conventional operation and closed-loop control.