Editorial - IET special issue on implementation of feedback controllers

Feedback controllers were originally implemented using special-purpose hardware - whether as special-purpose circuits in electronic amplifiers and radio receivers, or as electronic/pneumatic/mechanical devices for process control. Over the last 30 years or so they have increasingly been implemented as software algorithms in general-purpose processors or microcontrollers. Today the increasing availability and programmability of specialpurpose electronic hardware, in particular field-programmable gate arrays (FPGA) and graphical processing units (GPU), offer the possibility of a return to special-purpose hardware for the implementation of controllers. Model predictive control (MPC) in particular has been a very successful class of algorithms for process control, and there is much current interest in applying it more widely, in particular to high-bandwidth systems which require very short control update intervals. However, MPC relies on solving numerical optimisation problems online and in real time, so the computation time is often the main bottleneck preventing the adoption of MPC. Most of the papers in this Special Issue are devoted to speeding up MPC computations, mostly by using special-purpose hardware.