The sensor array

There has to be a multitude of sensors. They can be classed as analog or digital devices. Up to now, I have planned

external (interaction) sensors to allow the robot to perceive its surroundings
- Four mercury switch tilt sensors to sense critical pitch and roll levels
- Four bumper switches to detect collisions
- A magnetic compass, or hall detector to establish the robot's heading
internal (status) sensors to give feedback about the proper working of components
- rotational encoders on each of the drive trains to measure the distance and direction of travel
- two ampere meters to read the power generated by each of the motors
- a volt meter to monitor the battery status
auxiliary sensors
- a (stereo) video camera
- (stereo) microphone(s)
  which will be radio linked to a base station for analysis

The problem with most, if not all, sensors is the possible deviation of virtual (perceived) and real values. Through slip or blocking, the real distance may differ from the perceived values. Also, the tilt values might be influenced by acceleration. Switches may hang. This is a rather philosophical question: How far can I trust my sensors?