Sensitivity of MIQP-based design of MPC towards the uncertainty in backlash non-linearity gradient values

• Main Authors: H., Zabiri, Y., Samyudia
• Format: Conference or Workshop Item
• Published: 2005
• Subjects: TP Chemical technology
• Online Access: http://eprints.utp.edu.my/3769/1/P065.pdf; http://eprints.utp.edu.my/3769/
• Institution: Universiti Teknologi Petronas

Actuator backlash, among other actuator nonlinearities, has been known to cause serious degradation in any control loop performance if not handled efficiently. Current existing techniques in compensating the backlash effect includes the utilization of backlash nonlinear inverse, which is normally inserted prior to the control valves such that the net effect is a pure input/output gain. Though this technique proved efficient, the main drawback is when the control valve is operating near its saturation limits. As such, total compensation is not possible and the backlash effect may not be eliminated. The newly developed Mixed-Integer Quadratic Programming (MIQP)-based design within the framework of Model Predictive Control (MPC) has been shown through extensive simulation on industrial case studies to be able to handle efficiently both actuator saturation and actuator backlash nonlinearities simultaneously. In most cases, superior performance is achieved by the MIQP-based MPC in comparison to other existing backlash compensation methods. The simulation studies so far, however, are based on the assumption of unity backlash gradient. This may not be necessarily true in real-life situations. In this paper, the sensitivity of the MIQP-based MPC design is evaluated against the uncertainty in the backlash gradient values. Simulation results via an industrial Fluidized Catalytic Cracking Unit (FCCU) case study are presented to show the robustness of the newly proposed method to the uncertainties in the gradient values.