On the first job while standing behind the polisher for hours on end, I decided to automate the process. The drives are two Parvalux DC planetary geared motors about 10W each. The jocky wheel out the back is connected to a waterproof direction pot, while the wheel itself is connected to a sinusoid rotary encoder to measure forward movement. The amount of sweep is set by two pots on the control box as is the forward travel rate. see

the video. The program monitors the sweep rate and adjusts the differental voltage between the two motors, and it monitors the forward movement rate per cycle and makes adjustemnt to the common voltage to the motors. Every 8ms the interupt routine reads the AD channels, and responds to the "bumper bars". In thecircuit diagram you can see I've used a MC9S08QG8 MCU, reading the pots, linear position, Angular position, and the two bump switches on the bumper bars. The MCU also drives two LMD18201T H-bridge motor drivers.