Arc welding is one of the most irnpoT'tant areas of application for indnstTial robots. In most manufacturing welding sitnations, WI certainties in dimensions of the part, geometry of the joint, and the welding process itself TequiTe the use of sensors for maintaining the weld quality.

Se·ueTcLl systems use a vision system to measure the geometTy of the vuddle of melted metal as shown in the following diagram, whe-re the system uses a constant rate of feeding the wire to be melted.

Desired + ~ J:-!TOr _ diameter~

Error :E Wire-melting Controller Arc process K current 1 --

s+2 (0.5s+l)(s+l)

Vision system 1

0.005s+l A·rc Welding Control System Puddle diameter

(a) Calculate the nu1:rimum value of K for the system. that will result in a stable system.

(b) For 1/2 of the maximum value found ·in part (a), deteTmine the roots of the characteristic equation.

(c) Estimate the overshoot of the system of part

(b) when it is subjected to a step input.

Problem