Control engineering - Frequency domain stability criteria for mildly nonlinear feedback systems
Professor William Heath will talk on Control Engineering
This talk revisits classical frequency-based tools for assessing stability in control engineering systems and introduces new insights for saturated feedback systems. All welcome.
Engage’ is a series of lectures on a range of computing, engineering and design topics, organised by the School of Computer Science and Engineering.
Engineers often use frequency response to understand the dynamic behaviour of components and systems. For control engineers the frequency domain leads to a number of elegant graphical tools used to assess the stability and performance of feedback loops.
In this talk we revisit the Nyquist criterion for linear systems: this will be revision for anyone who has done a first course in classical control. We also revisit the circle, Popov and off-axis circle criteria, all classical tools used for systems with mild nonlinearities such as saturation.
More recently the literature has focused on analytic tools and criteria expressed as the feasibility of convex programs. These have brought back into play the so-called OZF (O’Shea-Zames-Falb) multipliers for feedback loops with saturation. These are powerful tools but have hitherto lacked any useful frequency domain interpretation. We present new frequency domain limitations on the OZF multipliers.
William Heath received a BA and MA in Mathematics from the University of Cambridge and an MSC and PhD in Systems and Control from UMIST. Since then, he has worked in both industry and academia, and in both the UK and Australia. He is a control engineer who has closed the loop for several industrial applications, including nanopositioners, high speed Diesel engines, plastic film extruders, edible oil refiners and water management systems. His research interests are focused on control systems with actuator nonlinearities. Prior to joining Bangor University he was Head of Department, Electrical and Electronic Engineering at the University of Manchester. He is currently Chair of the UK Automatic Control Council and Head of School, Computer Science and Engineering at Bangor University.
All welcome!