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Philip Maynard: Robot Update
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Robot Update · Oct 11, 01:13 PM by Philip Maynard

It’s alive!

An off-the-shelf chassis from Budget Robotics was used, complete with servo motors. These motors are used in all sorts of hobby devices, and take a pulse width modulated (PWM) signal as an input. The PWM capabilites of the HC12 make this easy. By defining our clock and changing the duty cycle, we can very accurately modulate the pulse width to control motor speed. It now accelerates, cruises, and stops on demand.

Next up for locomotion are wheel encoders. Once we know how far the wheels are turning we can use a control program to accurately position the robot on the board.

Since the robot will need to do more than just perform basic motion, we’ll be using some IR range sensors. These are around ten dollars, made by Sharp, and fairly accurate. They give a voltage related to the distance of an object in front of the sensor, and work from about 1.5 inches to 60 inches. Once we get motion accurate, we will implement PID control using both encoders and rangers to position the robot with relation to the environment. I think we’ll be using the compass chip as well, to help the robot figure out where it’s pointing when powered up. At that point the problem solving algorithm will be all that’s left – but that’s the big one.

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