The electronic control systems were designed to be small and simple. The robot's control algorithms are executed on a Cyrix 233 MHz embedded computer that sends commands via a PC-104 digital I/O board to a custom circuit board. This board holds a digital-to-analog converter that sends signals to the brushless motor amplifiers. The amplifiers provide control of motor current and commutation (via hall-effect sensors mounted on the motors).

Each degree of freedom is equipped with an optical encoder that provides precise position information. The translation of the robot body can be measured with a resolution of 10 microns. The body’s rotation can be measured with a resolution of 0.045 degrees. During fast motion, these encoders produce high frequency signals, which require the use of dedicated processing hardware. The custom PCB includes five 16-bit encoder counter ICs, which are periodically polled by the Cyrix processor, via the PC-104 I/O board.

To attain high-speed charging and discharging, the robot’s on-board 6-kilowatt power supply consists of two parallel sets of nickel-cadmium batteries. The batteries provide 60 volts to the motor amplifiers and to a pair of DC-to-DC converters. The volta ge converters supply power to the computer, brakes, and fans. The power system includes a solid-state relay, a voltage shunt, filtering capacitors, and fly-back diodes.

(A) The PC-104 digital I/O board, (B) relays that control the vertical translation brakes, (C) power supply monitor, (D) embedded computer, (E) custom circuit board, (F) wireless ethernet module, and (G) DC-to-DC voltage converters.