Patent Document ID: 6064029
Application ID: 09090088
Patent Flag: 1

Claim One:
1. A resistance spot welding apparatus having a primary circuit, a secondary circuit and a transformer for controlling the quality of a resistance spot weld, wherein an electric voltage is applied to the primary circuit to thereby generate a welding current, the welding apparatus comprising: means for sensing the weld current from the primary circuit; means for calculating power factors based on the welding current; means for obtaining a dynamic resistance curve based on the calculated power factors; and means for generating a gate signal for controlling the weld current wherein the gate signal is obtained by using the dynamic resistance curve, wherein the generating means includes means for estimating a nugget size and a nugget penetration based on the dynamic resistance curve and means for generating the gate signal based on the nugget size and the nugget penetration, and wherein the estimating means includes: means for converting the dynamic resistance curve to a discrete observation symbol sequence; a HMM block having n.omega. number of groups .mu.i's for calculating the discrete observation symbol sequence at each of the groups .mu.i's to calculate a corresponding probability P(O.mu.i), wherein i.epsilon.{1, 2, n.omega.} and n.omega. is a predetermined positive integer; means for estimating the nugget size and the nugget penetration by selecting a group having a maximum probability value among the groups .mu.i's; and means for outputting the nugget size and the nugget penetration.