TWI

Analytical modelling and experimental measurements were undertaken to investigate a dual-loop temperature control algorithm for friction stir processing, incorporating an inner loop to maintain constant power and an outer loop to set the power based on temperature feedback. The methodology was formulated based on block diagrams, classical control theory, PID (proportional-integral-derivative) control theory, performance metrics and the effect of PID gains. The temperature control algorithm was derived from the Mayfield-Sorensen control model, and the system transfer function was identified by numerical modelling of the heat diffusion equation and system dynamics. Welding experiments were conducted on AA 7075-T735 aluminium alloy and 1018 cold finished steel plates (thickness 6.35 mm) using a convex scrolled shoulder step spiral tool made from H13 tool steel or polycrystalline BN, respectively. The temperature response to step changes in power (2.09-2.54 kW) was used for system identification.

9th International Symposium, 15-17 May 2012, Session 5A: Process I, Paper 02