Gimpy’s First Controlled Movements

Ladies, gentlemen, undecided, and robots,

First I am pleased to announce that the Leg Cart has a name. It is now known as Gimpy.

We have been working hard trying to move Gimpy in a controlled way. “Controlled” here has a specific meaning… we mean we are controlling the joint with electronic feedback through a computer. If you’re new to control theory, the image below should give you an overview of what we’re trying to do.

Overall we are making progress and have demonstrated good closed-loop position control of our joints. We also exposed some system-level problems and snapped an actuator mount…

We have done additional tests since filming the video, but a combination of hardware problems (see our last post about ) has eaten most of our development time.

The knee joint in particular is prone to accumulating air and developing massive levels of uncontrollable backlash. We hypothesize that one of the reasons for this is that the knee actuator is the highest point in our hydraulic system, so when our system is unpowered bubbles will try to rise in to the knee. We are going to experiment with raising the pressure on the return lines and co-locating the knee control valve with the actuator, both of which could help with the air problems.

The whole reason we built the test leg was to learn the ‘gotchas’ of our component selection. These setbacks are expected and welcome, because now we can avoid them on the hexapod proper.

Long live Stompy.

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