Since the wheelchair's motor will have quadrature encoders nothing prevents the controller from remembering the history of its motion and being able to repeat a sequence, or to run a sequence in reverse - verbal 'macro' or 'subroutine' commands would allow the user to operate the chair more easily.

Since I will not be using the main control/feedback loop [the operator's brain and hand] that normally operates the power chair, I have to incorporate sensors to allow software to replace this control loop: a pair of proximity sensors on the chair body, and a notched disk on the inside of each wheel to act as a quadrature encoder. To allow for redundancy, I'll make that three proximity sensors on each wheel, so that one can fail and I still can get a quadrature signal back from the other two.