[Al Skierkiewicz]

When observing robots turning, I look first to see if the robot "jumps" or "hops" in the turn. This to me is a good indication that the tires need to break friction with the floor in order to turn. From an electrical standpoint, that operation puts the drive motors at nearly full stall current. For four CIM drivetrains that is over 400 amps. In multiwheel drives, this is a definite problem if the wheels are not set at different heights and are adjustable for tread wear. A good multiwheel design effectively reduces the wheelbase (and subsequent currents) without compromising stability. In crab designs, it will be hard to tell if the team has made any compensation for turning in the driving software without asking the people who would know. Typical crab designs, will experience the same turning frictions as other four wheels designs unless there is some speed modification made to allow one side of the robot to drive faster than the other. What makes the crab design more complex is the normal side forces encountered by the crab modules during the turns are transferred to the bearing surfaces at the top of the module. If there is no design plan for these forces, not only do drivetrain currents skyrocket, but steering motor currents also rise. As such, most crab designs will not be able to have tight turning radii without excessive currents encountered in standard four wheel designs. Robot designs that use a descending mechanism, foot or omni wheel, will be capable of tight turning (zero point turns) and low current. Excessive currents lead to power supply problems known to affect Crio, Radio and camera.