RC08Sensors

The 2007 robots had no on-board sensing and while using the camera to do most of the sensing worked the process is improved by adding sensor to the robots themselves. There are three new sensors for the robots in 2008: an IR LED ball sensor array, an encoder, and an accelerometer.

Ball Sensor

The ball sensor operates by illuminating the ball with modulated IR light in a region just in front of the robot. Reflected light from the ball is then picked up the IR transistor. The output of that transistor is fed into a bandpass filter with a pass-band centered on the center frequency of the modulated light and a passband that includes reflected light that has been doppler-shifted. At the end of the band-pass stage the modulated signal is integrated and then fed to a schmitt trigger. The threshold of the schimtt trigger is adjustable via a pot. One of the issues with this system is setting the modulation frequency. In the environment the only interference should be from lighting at 60Hz, but there are concerns that there will be interference from flourescent lighting or even other teams, though the latter is unlikely.

Tasks

IR LED Ball sensor

• [ ] Find an IR LED and a IR transistor
• [ ] Design the bandwidth filter and the Schmitt trigger circuits
• [ ] Build and test
  • [ ] Create a test-stand to test and verify ball sensor array performance
  • [ ] Build a prototype ball sensor system

Encoders

• [ ] Get final speed and wheel specs from ME team
• [ ] Find an optimal resolution versus frequency
• [ ] Select several parts and evaluate designs
• [ ] Write firmware to interface
• [ ] Integrate into velocity controller

Accelerometers

• [ ] Search for a cheap part
• [ ] Write firmware to interface
• [ ] Integrate into velocity controller

Specifications

IR Ball Sensor

• The entire circuit needs to have adjustable sensitivity
• The IR LED will illuminate the ball and the IR transistor will recieve the reflected signal
• The IR light needs to be modulated at a frequency of
• Matrix of Potential Ball Sensor Components

Encoders

• Need final specs from ME to get maximum encoding rate
• Matrix of Potential Encoders

Accelerometers

• Still defining specification
• Matrix of Accelerometers

Schematics

Schematics

Links

• Electrical System