For the motor drive I have done experiments with two circuit
configurations: single supply H-bridge and dual supply Half-bridge.
An interesting option shown above was using a control IC used in
radio-control servos: NE544. It was possible to add simple H-bridge buffer to the IC
motor drive output via opto-couplers, which also fulfilled my requirement
for isolation. Normally these IC's are driven by 1 - 2msec pulse width
variation, but by giving it a fixed pulse via a timer, drive was also
possible by inserting a voltage to the reference as shown. As output
transistors I used 10A / 100V NPN and PNP types. Power was via two 12V 7Ah
The circuit worked reasonably well for driving the platform, but had one big
drawback: The switching frequency was limited to about 120Hz max. The
platform sounded like I was drilling in a concrete wall!