Budget Linear Actuator from James Bruton

Hacker extraordinaire James Bruton has been working on a robot known as “Open Dog.” While it looks fantastic, he’s quick to note that he has yet to get it walking correctly, and that working with ball screws and hefty brushless DC motors on the scale he is attempting would be out of most people’s budgets.

On the other hand, if you want to build a walking robot, or device powered by linear actuators, there are cheaper alternatives. First, if it’s a walker, you might try scaling your robot down, as changes in dimensions affect the weight, not just linearly, but in a cubic fashion. Once you don’t have to deal with as much weight, you can use a cheaper linear actuator design, which forms the bulk of his video.

His new actuator consists of a length of aluminum extrusion, with an attached lead screw that makes a carriage in the middle traverse from side to side. An Arduino Uno reads output from the DC motor’s quadrature encoder, allowing him to accurately position things via a serial input. PID control is used to facilitate proper positioning, and another PID loop helps maintain a proper velocity even under different loads. Whatever your robotics goal, it’s an instructive video that gives a good idea of how linear actuators actually work. CAD and code for his build is available on GitHub.