JERK LIMITED TRACKING MODE FOR SOFIA CAVITY DOOR DRIVE SYSTEM

Abstract

A 5th order polynomial spline function is applied to the position command generation of the SOFIA cavity door drive system in order to limit jerk. By limiting the door jerk, a smooth acceleration profile is achieved and less current demand is required to provide door actuation. The existing drive system suffers from unanticipated high current demand during tracking mode,specifically over very frequent, short door trajectories. The high current demand is inherent to the aggressive trapezoidal acceleration profile. The 5th order polynomial spline function is chosen for not only its smooth velocity and acceleration profile, but more importantly, for its manipulation into closed-form expressions for predicting door drive dynamics and motor terminal behavior. It is shown that from the 5th order polynomial position function, one can derive closedform expressions for velocity, acceleration, and jerk. These expressions are applied to the wellknown electromechanical differential equation and the DC motor voltage equation to develop closed-form current and power expressions that includes the jerk limited track mode behavior and the door dynamics. The performance of the door drive system is then predicted under this jerk limited track mode and verified in the Matlab/Simulink environment. The simulation results of the jerk limited track mode show that while door response slightly decreases, current demand is vastly reduced.