In each of the following examples, indicate at least one (unknown) input, which should be measured and used for feed forward control to improve the accuracy of the system.
(a) A servo system for positioning a mechanical load. The servo motor is a fi eldcontrolled dc motor with position feedback using a potentiometer and velocity feedback using a tachometer.
(b) An electric heating system for a pipeline carrying a liquid. The exit temperature of the liquid is measured using a thermocouple and is used to adjust the power of the heater.
(c) A room heating system. Room temperature is measured and compared with the set point. If it is low, a valve of a steam radiator is opened; if it is high, the valve is shut.
(d) An assembly robot, which grips a delicate part to pick it up without damaging the part.
(e) A welding robot, which tracks the seam of a part to be welded.