Hexapod tripod gait is bumping too much!

if the forces could be transmitted hydraulically in horrizontal directions.

Since they can't modify the hardware there is no way to tell the foot position other than "guessing" where it should be at given the instantaneous pulse position sent to the servo, and waiting X for the servo to travel there (and hoping it does).

I don't think this solution gives them much more than they had to begin with for their particular problem, frankly, and at the cost of more coding for what they programmed their robot to have (one gait).

-- Gordon

I think you guy's insistance on feedback is a little over done for this application. If the bot were moving over uneven ground then leg position feedback might be of use, but probably not in this case. Perhaps you could desribe the benefits that would make it worth while in this instance. As for the $700 bot without sensors, start making one for $700 that is laden with sensors and get rich! ;)

Don't underestimate the benefits of force-based (as opposed to position-based) control. A couple classic examples where force-feedback dominates are writing and drilling/grinding.

With force feedback, this guy could have moved the legs into position and then lowered them under force control, thus setting an upper bound for the acceleration. Instead, he had to lower them "slowly enough" that it "usually worked".

That said, heavily-geared motors (e.g. hobby servos) are horrible for force control due to (a) friction (b) backlash and (c) the large downconversion of the geartrain. Real torque motors run nearly direct-drive, but they're big, heavy, pricey, and use high voltages. So we make due with hobby servos instead.

- Daniel

This is why I suggested a simple feedback via the serial servo controller. It's a coarse guide, but in my experience it at least can be used for determining if a bot is trapped against a wall and otherwise not able to sense this because of its sensor arrangement. The NetMedia controller is the only commercial one I've seen with this feature built-in, but there might be others. With this type of device force feedback is basically free, except for the cost of programming.

-- Gordon