Abstract :
In many cases the precise control of motion for point to point positioning demands not only accuracy in the final position but also that the states of acceleration and its rate of change are accurately controlled. Severe acceleration can overstress mechanical systems and drives whilst demand for excessive rates of change of acceleration may confound drive dynamics or excite severe modes of structural vibration. In these instances acceleration and its rate of change must be restricted whilst at the same time the motion cycles must be completed as fast as possible. Traditional “optimum time” systems accept the limitations of drive dynamics but solutions are usually piecewise linear with implied inherent departures below constrained values of acceleration and its rate of change. Absolute minimum time travel demands motion that is always at a constrained value, though it is to be accepted that some margin of departure must be allowed for control to accommodate effects forced by load disturbance or transducer “noise” errors
