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 determination of the particle position is based on photodiode array (PDA) shadowgraphy. 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 digitizer. 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 between the calculated and experimental trajectories allows one to study the system performance by simulation rather than by experiments and to assign the proper controller to the specific application. It is shown that the system is insensitive to extreme variations in particle size.