Development of a state-space water-level control for an array of cells to be employed as compensator in radiotherapy

This paper deals with the problem of water-level control for an array of cells by means of an hydraulic circuit. An on-off valve fills all the cells, while each cell is drained by a single on-off valve, so the control is intrinsically coupled. An optimal control with PWM (pulse width modulation) valves is carried out. At the end, simulation and experimental results are presented. The array of cells may find application as compensator for radiotherapy (Total Body Irradiation), by interposing the cells between the x-ray source and the patient: on-line water-level variations in the cells allow local radiation dose control