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.