ROBOTMAK3RS Blog

A week ago I posted the NXT Dog Sled Team project, which (appeared to...) have a traction problem due to a severe weight balance issue. Now having some fun with the other extreme, this NXT Spinner Bot project has six wheels, but nearly all of the weight is balanced over the two drive wheels in the center, with the four castor wheels barely touching the ground for balance. This gives it a very quick turning ability for break-dancing-like spin turns. The program provided with this project demonstrates a way to detect collisions by using the rotation sensors in the drive motors to detect when the motors have stalled, which allows the robot to bounce around your room without using any other sensors.

A design issue that I mention several times in the projects on www.nxtprograms.com is that of weight balance. To get a mobile robot to perform well, you need to get a good percentage of the total robot weight over the driven parts (powered wheels, legs, whatever), and keep weight over other parts that are just rolling or dragging to a minumum. Well, this Dog Sled Team project appears to set the record for the worst weight balance of any of my projects so far, with only about 10% of the total weight over the front legs of the dogs, which are trying to do all the work to drag the heavy sled. So how does it work? How do real dogs do it? Hmm, maybe there's a trick to it...