A ROBUST PARTICLE POSITION CONTROLLER FOR AN ELECTRODYNAMIC CHAMBER

A novel scheme for robust feedback control of a charged particle in an electrodynamic chamber has been designed and applied. The determinati on of the particle position is based on photodiode array (PDA) shadowg raphy. A 128 linear PDA is used to measure the trace of the particle. The PDA trace is transferred to a PC computer by a special purpose dig itizer. Analog-to-digital conversion is realized by feeding the signal through a hard limiter and measuring the time that corresponds to the shadow and light zones. The designed hardware allows a high sampling rate (7.8 kHz). The obtained position value is used by a PID algorithm to control the particle position. The one-to-one correspondence betwe en the calculated and experimental trajectories allows one to study th e system performance by simulation rather than by experiments and to a ssign the proper controller to the specific application. It is shown t hat the system is insensitive to extreme variations in particle size.