Now I’ve got a machine, the mjbots quad A1, which is capable of dynamic motions, but the only gait which takes advantage of these capabilities is the pronking one. That gait has the benefit that the dynamics are very simple. The entire time that that robot is in contact with the ground, it is in contact with all 4 legs, so in that regime it is fully controllable. Since it is fully controllable up to the point of lift-off, we can ensure that there is basically zero rotational rate while the machine is mid-flight, which means that it lands with all four legs largely at the same time. Of course, pronking isn’t a very fast or efficient way of getting anywhere, so I wanted to make the first steps… I guess pun intended, towards improving the more general walking algorithm to make the machine move faster in a more robust manner.

After getting all the legs swapped out, I ran my existing software to validate that all the pieces worked together.  Here’s a quick video showing basically what I’ve shown before, but with all new hardware:

While not perfect, now that I have flux braking in place, I have now succesfully pronked around for a while without faulting!  There are a number of outstanding problems that still need to be addressed:

• Sometimes the landing phase is erroneously cut short
• There is occasionally a grinding like noise that sounds like some controller is unstable
• I think the lateral movement is not working correctly
• The gait needs to be smarter about moving the legs past the center point when in mid-flight, and changing the gait period to achieve different speeds
• And probably a bunch of other problems I haven’t even identified yet

That said, it is still fun to watch it romp around!

Now that I can do controlled jumps, and have a UI which allows me to use the joystick, I finally started actually working towards pronking gaits.  Too bad for you, this post doesn’t have any details, merely a video snapshot of my learning and debugging process…