Abstract
A charged sample levitates statically in a modified two dimensional quadrupole electrostatic levitation apparatus under low gravity such as 1 x 10 -3 - 1 x 10 -4 G This report describes sample motion which the disturbance assumed to be a Gaussian distribution varied with time acts on it only to the gravitational direction Simulation showed graphically that motion is nearly a simple harmonic motion with small logarithmic decrement. Furthermore, it was cleared that (1) period of oscillation (2) the relation between an applied voltage and maximum tolerable disturbance. (3) logarithmic decrement under disturbance or no disturbance. In addition, the necessity of position control was pointed out to obtain stable levitation. PID (Proportional Integral and Derivative) control was tried for this purpose. It was able to give the excellent position control, where the motion by PID control was compared with that of non-PID control. Further, the relation between recovery time, which the time until the sample levitates statically after the disappearance of the disturbance, and the three constants contained within PID equation. The results are also reported.
