Digital Control of a Process Using On-Line Auto-Tuning

Summary An on-line real time hill climb is used to tune the parameters in an incremental three term direct digital controller. Th is procedure is carried out by taking the plant through a cycle comprised of a step upwards, a pause, a step down and then a pause. During this time an integral time weighted absolute error cost function is computed. At the end of the cycle this function provides information from which a hill climb program can evaluate improved settings. Results of the on-line hill climb are compared with off-line optimisation methods. The uses and limitations of on-line tuning applied to industrial plant are examined in the light of the experience gained.