Otis Tichatonga Nyandoro

Neural network-based model predictive control of a servo-hydraulic vehicle suspension system

This paper presents the design of a multi-layer feedforward neural network-based model predictive controller (NNMPC) for a two degree-of-freedom (DOF), quarter-car servo-hydraulic vehicle suspension system. The nonlinear dynamics of the servo-hydraulic actuator is incorporated in the suspension model and thus a suspension travel controller is developed to indirectly improve the ride comfort and handling quality of the suspension system. A SISO feedforward multi-layer perceptron (MLP) neural network (NN) model is developed using input-output data sets obtained from the mathematical model simulation. Levenberg-Marquandt algorithm was employed in training the NN model. The NNMPC was used to predict the future responses that are optimized in a sub-loop of the plant for cost minimization. The proposed controller is compared with an optimally tuned constant-gain PID controller (based on Ziegler-Nichols tuning method) during suspension travel setpoint tracking in the presence of deterministic road input disturbance. Simulation results demonstrate the superior performance of the NNMPC over the generic PID - based in adapting to the deterministic road disturbance.

Linear Slip Control Formulation for Vehicular Anti-Lock Braking System with Suspension Effects

Abstract This paper presents the formulation of a slip-control model for purposes of performing slip tracking of target slip. System modeling is performed to develop a braking model incorporating an active suspension. Linearisation of the highly non-linear multi-input multi-output developed Anti-lock Braking System model is performed by way of input-output feedback linearisation. Feedback linearisation is shown to provide a transformed linear ABS model while ensuring a verifiable stable state transformation. Lie algebra is used to find the stability of the internal dynamics through zero dynamics analysis. Simulation results demonstrate the validity of the approach along with the development of a stabilising condition for the linearisation approach.

Adaptive Sliding Backstepping Control of Quadrotor UAV Attitude

Abstract This paper proposes an adaptive sliding backstepping control law for quadcopter attitude control. By employing adaptive elements in the sliding mode control formulation the proposed control law avoids a priori knowledge of the upper bounds on the uncertainty. The controller we propose can be used for systems that are in strict feedback form with matched uncertainties. Numerical simulations show that this control method is capable of guaranteeing global asymptotic tracking of the desired attitude trajectory.

Gain selection criterion for the swing-up control of the Acrobot using collocated partial feedback linearisation

A novel set of feedback gain selection conditions pertaining to the swing-up control of the Acrobot using collocated partial feedback linearisation is derived and presented in this research. This set of conditions, collectively known as the gain selection criterion, highlights a region of possible feedback gain combinations, known as the region of appropriate gains (RAG), that will guarantee the unstable response of the Acrobot when initialised approximately near the fully-pendant equilibrium point. The criterion is derived using the Routh-Hurwitz stability criterion applied on the characteristic equation of the system linearised about the fully-pendant equilibrium point. Only one left-column coefficient, known as the critical Routh coefficient, demonstrates the potential of influencing the stability of the system. The boundaries of the RAG are defined from the analysis of the critical Routh coefficient. The gain selection criterion will prevent the unintended selection of a combination of feedback gains that will cause a stable response about the fully-pendant equilibrium point, preventing the satisfactory execution of swing-up control on the Acrobot from the fully-pendant equilibrium point. This criterion may, more conveniently, be applied to specific types of multi-link pendulum system that approximate the behaviour of the partially linearised Acrobot.

Equivalence of Multi-Formulated Optimal Slip Control for Vehicular Anti-Lock Braking System

Abstract This paper presents the equivalence of time-optimal and optimal distance slip-control approach for purposes of performing antilock braking. A dynamic braking model is developed encorporating a slip state to facilitate slip tracking. Optimal distance braking is performed with control constraints on the dynamic slip based braking model. A similar treatment is applied for time optimal braking on the braking model. The key contribution is the demonstration of the equivalence of optimal distance and time optimal braking of a vehicle. A generalised none zero-terminal condition is utilised in the optimal formulations. Simulation results demonstrate the validity of the approach along with the development of a key optimality condition for the equivalence approach.

High performance Ash Fusion temperature measurement

Ash Fusion temperature measurement of a gasifier in a CTL plant is necessary to determine the extent of ash clinkering inside the gasifier, and ultimately to avoid unstable gasifier operation and pressure drop related problems. A suitable smart instrumentation measurement system with a minimum bandwidth of 1 kHz is proposed, which comprises of an R type thin film thermocouple sensor for temperature detection with the aid of an Resistance-to-Temperature Device, a capacitive pressure sensor for interference detection, amplifiers and filters for signal conditioning, a microcontroller for data processing and a USB device for data logging. Analysis of static and dynamic characteristics of the system limits aliasing error to 1% and determines the system error as 1.75% and the system bandwidth as 1MHz.

The Compound Police: Idea of a Noise-monitoring Device in Crowded Residences

Abstract The study conceptualised a noise-monitoring device that could be used by managers of crowded residential areas. The hypothesised noise-monitoring device which operates like compound police is envisaged to replace human presence in noise detection, monitoring, and switching off of noise-making machines that transgress set community noise standards. The device targets loud music or unwanted sound generated by radios and television sets. The intended device could work in places such as hostels, flats, townhouses, dormitories, office buildings and similar residences or workplaces in which the playing of loud music is restricted. The study attempted to demonstrate how the conceptualised device works by providing a theoretical framework on which to base the design of the noise-monitoring machine and the equipment that could be used in the manufacture of the device. Theoretically, the idea provides positive engineering indicators of the possibility of designing the intended noise-monitoring device in South Africa. Directions for future research could focus on laboratory testing of the idea in order to produce and patent such a device.