Performance comparison of optimal fractional order hybrid fuzzy PID controllers for handling oscillatory fractional order processes with dead time

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Fuzzy logic based PID controllers have been studied in this paper, considering several combinations of hybrid controllers by grouping the proportional, integral and derivative actions with fuzzy inferencing in different forms. Fractional order (FO) rate of error signal and FO integral of control signal have been used in the design of a family of decomposed hybrid FO fuzzy PID controllers. The input and output scaling factors (SF) along with the integro-differential operators are tuned with real coded genetic algorithm (GA) to produce optimum closed loop performance by simultaneous consideration of the control loop error index and the control signal. Three different classes of fractional order oscillatory processes with various levels of relative dominance between time constant and time delay have been used to test the comparative merits of the proposed family of hybrid fractional order fuzzy PID controllers. Performance comparison of the different FO fuzzy PID controller structures has been done in terms of optimal set-point tracking, load disturbance rejection and minimal variation of manipulated variable or smaller actuator requirement etc. In addition, multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-II) has been used to study the Pareto optimal trade-offs between the set point tracking and control signal, and the set point tracking and load disturbance performance for each of the controller structure to handle the three different types of processes

Novel control of a high performance rotary wood planing machine

Rotary planing, and moulding, machining operations have been employed within the woodworking industry for a number of years. Due to the rotational nature of the machining process, cuttermarks, in the form of waves, are created on the machined timber surface. It is the nature of these cuttermarks that determine the surface quality of the machined timber. It has been established that cutting tool inaccuracies and vibrations are a prime factor in the form of the cuttermarks on the timber surface. A principal aim of this thesis is to create a control architecture that is suitable for the adaptive operation of a wood planing machine in order to improve the surface quality of the machined timber. In order to improve the surface quality, a thorough understanding of the principals of wood planing is required. These principals are stated within this thesis and the ability to manipulate the rotary wood planing process, in order to achieve a higher surface quality, is shown. An existing test rig facility is utilised within this thesis, however upgrades to facilitate higher cutting and feed speeds, as well as possible future implementations such as extended cutting regimes, the test rig has been modified and enlarged. This test rig allows for the dynamic positioning of the centre of rotation of the cutterhead during a cutting operation through the use of piezo electric actuators, with a displacement range of ±15μm. A new controller for the system has been generated. Within this controller are a number of tuneable parameters. It was found that these parameters were dependant on a high number external factors, such as operating speeds and run‐out of the cutting knives. A novel approach to the generation of these parameters has been developed and implemented within the overall system. Both cutterhead inaccuracies and vibrations can be overcome, to some degree, by the vertical displacement of the cutterhead. However a crucial information element is not known, the particular displacement profile. Therefore a novel approach, consisting of a subtle change to the displacement profile and then a pattern matching approach, has been implemented onto the test rig. Within the pattern matching approach the surface profiles are simplified to a basic form. This basic form allows for a much simplified approach to the pattern matching whilst producing a result suitable for the subtle change approach. In order to compress the data levels a Principal Component Analysis was performed on the measured surface data. Patterns were found to be present in the resultant data matrix and so investigations into defect classification techniques have been carried out using both K‐Nearest Neighbour techniques and Neural Networks. The application of these novel approaches has yielded a higher system performance, for no additional cost to the mechanical components of the wood planing machine, both in terms of wood throughput and machined timber surface quality

Microcontroller based data acquisition and control of a solar thermal energy system.

Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.A solar thermal energy system is being rebuilt at University of KwaZulu-Natal School of Physics. A similar system is also being built in the University Eduardo Mondlane – Maputo Mozambique, in a team development work. The system is composed mainly of the following subsystems: (i) An Energy capture subsystem: paraboloidal dish concentrator with a heat receiver, mounted on a dual axis polar mount sun tracking assembly; (ii) An Energy storage subsystem: rock-bed thermal energy storage (TES) system; (iii) An Energy utilization subsystem: any user heat utilization (like a cooking or water boiling appliance); and (iv) A monitoring and control subsystem. The subsystem (iv) for performing a controlled charging of the Thermal Energy Storage from a hot plate simulated solar heat, was formerly developed and it was based on 2 conventional data loggers (HP/Agilent) and programs running on 2 PCs. The present work is aimed at performing the same plus additional monitoring and control tasks, based on a low cost microcontroller design. The monitoring and control subsystem based on the Atmel ATmega 32 MCU has been designed and built, capable of performing data acquisition, data logging and control of relevant system variables such as, hour and declination angles of the tracking concentrator; to cite some of the main variables. Besides a huge work of designing, building, programming and testing the microcontroller system itself, a special focus was given to the monitoring and control of the solar heat concentrator, to perform a dual axis sun tracking, so as to get as much as possible of the available solar radiation. Measurements of various system parameters such as, the sun tracking actual hour and declination angles, the inlet and outlet temperatures of both the heat receiver and the rock bed heat storage, etc., for the system under consideration have been carried out