Tuesday, July 1, 2014

The long road to an Autonomous Vehicle.

Some people play tennis, some try to build autonomous wheeled robots. I do the later and the result has come to be known as “Terry”. In the long road toward that goal what started as a direct drive, “give the motor a PWM of X% of the total power”, lead to having encoder feedback so that the wheel could be turned an exact amount over a given time.  This has meant that the control interface no longer uses a direct power and direction slider but has buttons to perform specific motion tasks. The button with the road icon and a 1 will move the wheels forward a single rotation to advance Terry 6π inches forwards (6 inch wheels).

The red tinted buttons use the wheel encoders to provide precision movement. Enc left and Enc right turn Terry in place (one wheel forward, one wheel backwards). The Circus and Oval perform patrol like maneuvers. Circus moves forward, turns in place, returns back, and turns around again. It's like a strafing patrol. On the other hand, the Oval turns move like a regular car, with both wheels going forward but one wheel moving slower than the other to create the turning effect. The pan and tilt control the on board camera for a good Terry eye view of the world.

I added two way web socket communications to Terry this week. So now the main battery voltage is updated and the current, err, current for each motor is shown at the bottom of the page. The two white boxes there give version information so you can see if the data is stale or not. I suspect a little async javascript on some model value will be coming so that items on the page will darken as they become stale due to lag on Terry or communications loss.

I've been researching proximity detection and will be integrating a Kinect for longer distance measures soon. Having good reliable distance measurements from Terry to objects is the first step in getting him to create maps of the environment for autonomous navigation.

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