a joining equipment in which a neural network is employed for controlling a joining process . a dynamic analog model is used for neuron elements configuring the network . the equipment includes a detector , a controller , and a neural network . the detector detects a joining state of a joining portion when work pieces are joined with each other . the controller controls the output of the joining equipment . in response to output signals from the detector , the neural network transmits signals to the controller . such a structure allows the joining equipment to flexibly respond to complicated changes in joining states . besides , using similarity with a thermal conduction equation enables to minimize the number of input items fed into the neural network . furthermore , using an approximate solution to the thermal conduction equation realizes to accelerate the time for numerical calculation without loss of accuracy .