Treads, Tracks, Tank system Talk/Help

[Al Skierkiewicz]

Some of the issues you are asking about are typical of tank tread systems. One that you have not mentioned is the bane of tank drive using treads or locked wheels, i.e.stalled motors.
When using treads on carpet, the side friction (during turns) with the carpet is so high that robot has to hop to break free from the carpet surface. Since the motor/transmission is usually capable of enough torque to overcome the friction, the robot hops when turning. However, during these moves the motors are at, or very near, stall. In a four motor drive using the CIMs, that is potentially over 400 amps. In the IFI control system, this causes the battery voltage to temporarily fall below the drop out voltage of 8 volts, and the controller goes into protect mode disabling all outputs and switching to the backup battery. (We don't have any data yet on what the new controllers might do under these conditions.) A wheeled robot in the same kind of drive could have a little less side friction but the problem remains and they also will hop to some extent in turns. Drivers can minimize the hopping by turning in conjunction with forward or backward motion. The AndyMark style wheels that have no side friction were developed for this reason. Everyone tries tank treads from time to time, but the tradeoffs are usually significant enough that teams go back to wheeled drive systems. Any game in which turning is required will have a minimum number of robots with treads. This year's game is a good example.