Salmiah Ahmad

A Modular Fuzzy Control Approach for Two-Wheeled Wheelchair.

Wheelchairs on two wheels are becoming essential part of life for disabled persons. But designing control strategies for such wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics a double inverted pendulum with three actuators, one for each wheel, and one for chair position. The system starts to work with lifting the front wheels (casters) to the upright position and further with stabilizing in the upright position. The challenge resides in the design and implementation of suitable control strategies for the two-wheeled wheelchair so as to perform comparably similar to a normal four-wheeled wheelchair. A two-level modular fuzzy logic controller is proposed in this paper. A model of the standard wheelchair is also developed as a test and verification platform using Visual Nastran software integrated with Matlab.

A new configuration of two wheeled vehicles: Towards a more workspace and motion flexibility

This work presents a novel design of two-wheeled vehicles. The proposed design provides the vehicle with more flexibility in terms of the increased degrees of freedom which enable the vehicle to enlarge its working space. The additional translational degree of freedom (DOF), offered by the linear actuator, assists any attached payload to reach higher levels as and when required. The model of the system mimics the scenario of double inverted pendulum on a moving base. However, it is further complicated due to the addition of a one more (DOF). As adding more degrees of freedom to the system increases the degree of complexity, Lagrangian dynamic formulation is used, due to its relative simplicity, to derive the system dynamics. The new developed configurations is of great importance in various applications including self balance robots, wheelchairs on two wheels, stability analysis of multi segment gaits and multi links cranes etc. In order to maintain the system nonlinear characteristics, the system model is derived with the consideration of the joints friction based on the Coulomb friction model. An investigation is carried out on the impact of the joints damping on the stability of the system.

Modelling and Control of a Wheelchair on Two Wheels

Wheelchairs on two wheels are needed for disabled persons to perform some of the essential tasks in their living and work environments. In fact it offers great advantages and efficiency for the user. Besides allowing a disabled to lead independent life, it is expected not to take much space during mobility as compared to when it is on four wheels and thus a wheelchair on two wheels has associated design and development challenges. These include modelling and controller design for the system to perform comparably similar to normal four-wheeled wheelchair. In this paper physical model of a wheelchair on two wheels that mimics double inverted pendulum is designed and a novel fuzzy logic control mechanism is developed and tested with control of the two-wheeled wheelchair.

Forward and backward motion control of wheelchair on two wheels

The challenge in designing wheelchair on two wheels involves the design and implementation of suitable control strategies for a two wheeled wheelchair to perform comparably similar to a normal four wheeled wheelchair. It is important to note that a wheelchair on two wheels is expected not to take much space during mobility as compared to when it is on four wheels. Moreover, disabled people are encouraged and expected to perform most activities that others can do and hence lead an independent life. Thus, wheelchairs on two wheels are needed for disabled persons to perform some of the essential tasks in their living and work environments. In this research a model of the standard wheelchair is developed as a test and verification platform using Visual Nastran software. Novel fuzzy logic control strategies are designed for lifting up the chair (transforming a four-wheeled wheelchair to a two-wheeled wheelchair) and maintaining stability and balance while on two wheels. Furthermore, position control for forward and backward mobility of the wheelchair on two wheels is developed using fuzzy logic control. Simulation results of the proposed control strategy are presented and discussed.

Linear Quadratic Regulator (LQR) approach for lifting and stabilizing of two-wheeled wheelchair

This paper discussed about the implementation of Linear Quadratic Regulator (LQR) on a two-wheeled wheelchair model. The state space model of the two-wheeled wheelchair that mimics double inverted pendulum has been obtained from the linearized mathematical equations of the model. The equations of motions, which are very complex, are derived from the wheels, Link1 and Link2. The goal is to have both links of the two-wheeled wheelchair to be at the upright position. To fulfill the goal, Link1 is to be lifted up from its initial position to zero degree upright position while maintaining Link2 at the upright position. This research is aimed to help disabled people who are using the wheelchair as the main transport for mobility but cannot stand on his own due to permanent injuries on the extremities. The scenario requires a suitable control strategy for the good system performance. Results show that LQR provides good response with the linearized differential equations.

Genetic Algorithm Optimisation for Fuzzy Control of Wheelchair Lifting and Balancing

In this paper, an optimisation technique is adopted to manipulate the input and output scaling of a fuzzy logic controller for lifting the front wheels of a wheelchair and stabilizing the wheelchair in two-wheeled mode. A virtual wheelchair (WC) model is developed within Visual Nastran (VN) software environment where the model is further linked with Matlab/Simulink for control purposes. The lifting of the chair is done by transforming the first link, attached to the front wheels (casters) to the upright position while maintaining stability of the second link where the payload is attached. General rules of thumb allow heuristic tuning of the parameters but a proper optimisation mechanism will perform better. Genetic Algorithm is used to control the two-wheeled wheelchair and results show that the optimised parameters give better system performance.

Modelling and simulation of double-link scenario in a two-wheeled wheelchair

Wheelchairs on two wheels are essential part of life for disabled persons. But designing control strategies for these wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics the inverted pendulum with a double-link scenario. This forms an example of multi degree of freedom system where there are three actuators, one on each wheel, and one for position between the two links. The system starts to work with lifting the front wheels casters to the upright position and further on stabilizing in the upright position. The challenge resides in the design, modelling and control of the two-wheeled wheelchair to perform comparably similar to normal four-wheeled wheelchair. This paper is aimed to model the highly nonlinear and complex two-wheeled wheelchair system using two different approaches. A state-space model is obtained from the linearised mathematical model as an initial attempt for control design investigation. Then a complex visualized mathematical model is developed, which proves as a good technique for prediction and simulation of the two-wheeled wheelchair.

Simulation analysis of different strength levels of EOG signals

This paper described the signal from the eye muscles that is called electrooculogram which is generated at different eye movements directions and levels. The eye movement signal data is captured by using Al/AgCl electrodes and passed through the g.USBamp from G.TEC Medical Engineering GMBH eye movement data collection. The eye movement data is passed to the Matlab/Simulink software for data analysis. The electrooculography (EOG) signals are obtained from four (4) different places around eye (right, left, up, and down) with different level of strengths will produce different strength of EOG signal. The EOG data obtained could be very helpful in many applications such as in the field of rehabilitation for example as a communication tool to operate a wheelchair among tetraplegia.

Effect of Inclined Rowing Machine on FES-Assisted Indoor Rowing Exercise Performance

This paper describes the effect of inclined track in an indoor rowing machine on the rowing exercise for paraplegics. The indoor rowing exercise is introduced as a total body exercise for rehabilitation of function of lower extremities through the application of functional electrical stimulation (FES). A model of the machine is developed using the Visual Nastran (Vn4D) software environment. Nine different degrees of inclination are set. Fuzzy logic control is implemented to control the knee and elbow trajectories for each of the inclination angle. The generated level of electrical stimulations for activation of quadriceps and hamstrings muscles are recorded and analysed. The results show that the highest efficiency is achieved at 7° of inclination. In view of good results obtained, it is concluded that different angles of track inclination significantly affect the level of electrical stimulation required to assist paraplegics’ indoor rowing exercise.

PID-Ant Colony Optimization (ACO) control for Electric Power Assist Steering system for electric vehicle

Electric Power Assist Steering (EPAS) system offers a significant potential in enhancing the driving performance of a vehicle where the energy conserving issue is important. In this paper, Ant Colony Optimization (ACO) algorithm is implemented as tuning mechanism for PID controller. The aim of this hybrid controller is to minimize energy consumption of the EPAS system in Electric Vehicle (EV) by minimizing the assist current supplied to the assist motor. The ACO algorithm searching technique is applied to search for the best gain parameters of the PID controller. The fast tuning feature of ACO algorithm is the factor that distinguish this hybrid method as compared to conventional trial and error method PID controller tuning. Simulation results shows the performance and effectiveness of using ACO algorithm for PID tuning.