Interval model control of human welder’s movement in machine-assisted manual GTAW torch operation

Torch maneuver skills possessed by a skilled welder typically require a long time to develop. A machine-assisted feedback control system that can stabilize the welder movement would thus be of interest in the manufacturing industry. In this paper, an interval model-based feedback control system is designed to assist the welder to adjust the torch movement for tracking desired speed in manual gas tungsten arc welding (GTAW) process. To this end, an innovative helmet-based manual welding platform is utilized. In this system, vibrators are installed on the helmet to generate vibration sounds to instruct the welder to speed up or slow down the torch movement. The torch movement is monitored by a leap motion sensor. The torch speed is used as the feedback for the control algorithm to determine how to change the vibrations. To design the control algorithm, dynamic experiments are conducted to correlate the arm movement (torch speed) to the vibration control signal. Linear models are first identified and the corresponding linear parameter intervals are obtained. Interval model control algorithm is then implemented. Simulation results reveal that the proposed interval model control algorithm outperforms traditional Proportion Integration Differentiation (PID) controller. Experiments further verified that the welder’s speed is controlled with acceptable accuracy.