At the end of the semester, we partially assembled and programmed a small robot to fulfill the laboratory requirements:
- When the robot is switched on, it uses the pulse width modulation (PWM) drivers to move forward
- If the robot strikes a surface, it backs up, turns, and then moves forward again
However, we had enjoyed working together so much that we decided to add several additional features to compete in the Calbot competition.
- The robot can produce a warning sound via a D/A converter and analog power amplifier
- The robot can shoot a projectile using an inductor-actuator
- A microphone measures an audio signal
- The signal is amplified and the dynamics are compressed via several OP amps and an opto-isolator
- The bipolar power supply for the circuit is provided using a trick with a voltage divider and a pseudo-ground
- The signal is converted from analog to digital form at regular intervals
- The program reads the digital data and uses a noise-gate algorithm to decide if the signal is loud enough to be interpreted as an instruction. If the signal is loud enough:
- The amplitude of the DFT of the recorded samples is computed via a proprietary algorithm
- The highest peak within a certain frequency range is assumed to correspond to the pitch of the signal
- The pitch is converted to a MIDI note
- Depending on the note, the following actions are possible:
- Move forward
- Move backward
- Turn left
- Turn right
- Produce the warning sound and fire the projectile a few seconds later
For the competition, we used a keyboard, which had an instrument producing few overtones. We were also asked by the professor to sing pitches in order to control the robot. This technique also worked. As a result, we won first prize: two Kodak digital cameras. Here is a picture of the final product which now stands in Cory Hall next to other winning robots. Many of the pictures on this web site were taken with one of the cameras.