Mathew Walter Dunnigan

A comparison of vector control and direct torque control of an induction machine

This paper provides a comprehensive comparison of the two main high performance induction machine torque control methods, viz., vector control and direct torque control. A series of tests conducted on a common hardware platform highlight the relative advantages and disadvantages of each method.

A novel rotor resistance identification method for an indirect rotor flux-orientated controlled induction machine system

This paper proposes a novel rotor resistance identification method for an indirect rotor flux-orientated controlled induction machine drive. The method is effectively integrated with the intermediate current control loop of the system. A decoupled synchronous voltage control scheme is used to achieve a fast, accurate current control response and indicates the relative thermal change of the rotor resistance. A model reference adaptive control scheme is then used to track the variation of the rotor resistance. Other issues, such as the nonideal characteristics of the power devices, stator resistance variation and comparison with two other parameter identification methods, are included. This method is less complex and more effective than others, and this is supported by theoretical analysis, and verified by simulation and experimental results.

Nonlinear robust control of a vector-controlled synchronous reluctance machine

This paper presents the implementation of Slotines approach of sliding mode control for position control of a vector-controlled synchronous reluctance machine. A comparison is undertaken between the performance of a fixed gain controller and two sliding mode controllers for both the regulator and servo cases. Invariant performance is obtained using Slotines approach of sliding mode control compared to a fixed gain controller. Robustness to parameter variation is an important feature of this technique. This can be achieved through the control law design, assuming parameter variation bounds are known. These improvements are demonstrated for variations in the load inertia. Machine inductance ripple affects the quality of achievable position control. A state-space model for the machine to incorporate this effect yields drive simulation results that agree with presented experimental results.

Passive Compensator Load Variation for Deep-Water Drilling

This paper explores the dynamic behavior of a passive drill string compensator being used for deep-water drilling in moderate seas using a detailed dynamic simulation. Vessel heave, even moderate, gives rise to a disturbance; the purpose of the compensator is to mitigate this effect and to maintain a near-steady load on the drill bit; any variation is termed ldquoload variationrdquo; the compensator is imperfect with various friction elements and viscous losses affecting the compensator performance; the simulation set out in this paper illustrates the load variation in a manner consistent with that experienced during actual drilling. Significant load variation is demonstrated by the simulation, with the main contribution arising from the nonlinear friction in the compensator seals; in addition, significant contact instability occurs when drilling on a very hard bottom formation resulting in bit bounce; this effect is commonly observed.

Derivation and analysis of a dynamic model of a robotic manipulator on a moving base

Abstract A dynamic model of a robotic manipulator mounted on a moving base is derived using the Euler–Lagrange approach. It is assumed that the base inertia is large enough not to be influenced by the manipulator motion and therefore can be treated as a time-varying parameter in the dynamic equations. The presented derivation is applied to a Mitsubishi PA10-6CE robotic manipulator mounted on a 2-DOF platform. The model is analysed by comparing simple closed-loop control results of the simulated model with experimental data from the manipulator mounted on the platform.

Development and Comparison of an Improved Incremental Conductance Algorithm for Tracking the MPP of a Solar PV Panel

This paper proposes an adaptive and optimal control strategy for a solar photovoltaic (PV) system. The control strategy ensures that the solar PV panel is always perpendicular to sunlight and simultaneously operated at its maximum power point (MPP) for continuously harvesting maximum power. The proposed control strategy is the control combination between the solar tracker (ST) and MPP tracker that can greatly improve the generated electricity from solar PV systems. Regarding the ST system, the paper presents two drive approaches including open- and closed-loop drives. Additionally, the paper also proposes an improved incremental conductance algorithm for enhancing the speed of the MPP tracking of a solar PV panel under various atmospheric conditions as well as guaranteeing that the operating point always moves toward the MPP using this proposed algorithm. The simulation and experimental results obtained validate the effectiveness of the proposal under various atmospheric conditions.

Heave Compensation Simulation for Non-Contact Operations in Deep Water

This paper uses a detailed dynamic model to simulate the landing operation from a floating drilling vessel, which uses a passive drill string compensator in an attempt to mitigate the effects of vessel heave. The simulation shows that the passive compensator on its own can reduce the effects of heave in deep water but only to a limited extent

Redundancy resolution for underwater vehicle-manipulator systems with congruent gravity and buoyancy loading optimization

In this paper, a new redundancy resolution scheme is proposed for an underwater vehicle manipulator system (UVMS). Using the proposed resolution technique, the systems redundancy is exploited so as to minimize gravity and buoyancy loading of the UVMS which is composed of subsystems with different dynamic responses. The generalized velocity components (GVC) approach is considered in order to obtain a congruent gravitational expression which consists not only of vehicle pose but also the onboard manipulator configuration. During end-effector motion, the overall systems control effort is reduced if gravity and buoyancy loading of both subsystems are small values. A new performance index is applied using the local redundancy resolution. Results from simulations are presented to demonstrate the benefits of the proposed performance index.

Active Heave Crown Compensation Sub-System

This paper outlines an active heave compensation system used in conjunction with a crown mounted compensator. The objective is to reduce the heave disturbance at the suspended load above sea floor using an active sub-system comprising controller, sensors and a suitable hydraulic power unit driving an actuator attached to the compensator. In this case the compensator system behaves much like a spring mass system and is described by a second order differential equation.

Parameter estimation of an induction machine using a dynamic particle swarm optimization algorithm

This paper proposes a new application of a dynamic particle swarm optimization (PSO) algorithm for parameter estimation of an induction machine. The dynamic PSO is one of the PSO variants, which modifies the acceleration coefficients of the cognitive and social components in the velocity update equation of the PSO as linear time-varying parameters. The acceleration coefficients are varied during the evolution process of the PSO to improve the global search capability of particles in the early stage of the optimization process and direct the global optima at the end stage. The algorithm uses the measurements of the three-phase stator currents, voltages, and the speed of the induction machine as the inputs to the parameter estimator. The experimental results obtained compare the estimated parameters with the induction machine parameters achieved using traditional tests such as the dc, no-load, and locked-rotor tests. There is also a comparison of the solution quality between a genetic algorithm (GA), standard PSO, and dynamic PSO. The results show that the dynamic PSO is better than the standard PSO and GA for parameter estimation of the induction machine.