Welding Contml: Large welding mbots are used in today 's auto plants. The welding head ·is moued to different positions on the av.to body, and rapid, accurate response is requ·ired. A block diagram of a welding head positioning system is shown in the following diagram.

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R(s) +~~

Desired -

position I Controller Head dynamics K(s+a) 1

(s+ 1) s(s+2)(s+3)

Welding Robot Control System Y(s)

Dat ahead po sition It is d~Csired to determine the ranqe of K and a for which the system is stable. The characteristic equation is K(s +a)

l+C(s)=l+ s(s+l)(s+2)(s+3) =O