School of Informatics and Computing

Figure 1. Inverted Pendulum Device Overview

The device was constructed from a Panasonic (KX-P1123) dot matrix printer. The printer was stripped down to just the
minimum needed to drive the carriage.  A fan and heatsink were added to the stepper motor drivers to deal with the
thermal issues surrounding driving the motor at a much higher frequency than the original design point.  The control system
for the inverted pendulum has been implemented on a Xilinx XC4003E prototype board. A PIC16F877 microcontroller
has been used to implement the compensator.

Figure 2. Inverted Pendulum Right Side View

The print head was stripped from the carriage and replaced by a bearing mounted rod (wooden arrow shaft). The rod is bolted to a metal disk. The metal disk and the bearing was salvaged from an old harddrive (the disk was the flywheel from the drive). The metal disk has a large O-ring around it's circumference.  This contacts a roller from a salvaged Sun mouse (non-optical) position encoder.  The encoder provides pendulum relative position and angular velocity.  There is also a small hole drilled in the metal disk that is sensed with an infrared sensor. This provides absolute pendulum position needed to calibrate the position encoder).

Figure 3. Inverted Pendulum Left Side View