Muhammad Aizzat Zakaria

Dynamic Curvature Steering Control for Autonomous Vehicle: Performance Analysis

This paper discusses the design of dynamic curvature steering control for autonomous vehicle. The lateral control and longitudinal control are discussed in this paper. The controller is designed based on the dynamic curvature calculation to estimate the path condition and modify the vehicle speed and steering wheel angle accordingly. In this paper, the simulation results are presented to show the capability of the controller to track the reference path. The controller is able to predict the path and modify the vehicle speed to suit the path condition. The effectiveness of the controller is shown in this paper whereby identical performance is achieved with the benchmark but with extra curvature adaptation capabilites.

Piecewise Trajectory Replanner for Highway Collision Avoidance Systems with Safe-Distance Based Threat Assessment Strategy and Nonlinear Model Predictive Control

This paper proposes an emergency Trajectory Replanner (TR) for collision avoidance (CA) which works based on a Safe-Distance Based Threat Assessment Strategy (SDTA). The contribution of this work is the design of a piecewise-kinematic based TR, where it replans the path by avoiding the invisible rectangular region created by SDTA. The TR performance is measured by assessing its ability to yield a maneuverable path for lane change and lane keeping navigations of the host vehicle. The reliability of the TR is evaluated in multi-scenario computational simulations. In addition, the TR is expected to provide a reliable replanned path during the increased nonlinearity of high-speed collisions. For this reason, Nonlinear Model Predictive Control (NMPC) is adopted into the design to track the replanned trajectory via an active front steering and braking actuations. For path tracking strategy, comparisons with benchmark controllers are done to analyze NMPC’s reliability as multi-actuators nonlinear controller of the architecture to the CA performance in high-speed scenario. To reduce the complexity of the NMPC formulation, Move Blocking strategy is incorporated into the control design. Results show that the CA system performed well in emergency situations, where the vehicle successfully replanned the obstacle avoidance trajectory, produced dependable lane change and lane keeping navigations, and at the same time no side-collision with the obstacle’s edges occurred. Moreover, the multi-actuators and nonlinear features of NMPC as the PT strategy gave a better tracking performance in high-speed CA scenario. Assimilation of Move Blocking strategy into NMPC formulation lessened the computational burden of NMPC. The system is proven to provide reliable replanned trajectories and preventing multi-scenario collision risks while maintaining the safe distance and time constraints.

Kinematics Analysis of a 3DoF Lower Limb Exoskeleton for Gait Rehabilitation: A Preliminary Investigation

Robotics have been engaged to address the shortcomings of conventional rehabilitation therapy as well as the ever increasing demand for rehabilitation services. This paper presents the kinematics of a 3DoF lower limb exoskeleton restricted to the sagittal plane. The Denavit-Hartenberg representation, as well as the geometrical solution approach, are employed to obtain the forward and inverse kinematics of the exoskeleton, respectively. A simulation study is performed to validate the proposed model.

The Identification and Control of a Finger Exoskeleton for Grasping Rehabilitation

This paper evaluates the efficacy of different classical control architectures in performing grasping motion. The exoskeleton system was obtained via system identification method in which the input and output data was measured by means of current sensor (ACS712) and encoder attached to a DC geared motor (SPG30e-270k). The data obtained is split with a ratio of 70:30 for estimation and validation, respectively. The transfer function of the system is evaluated by varying the number of poles and zeros that are able to fit well with validation data. The performance of the classical P, PI, PD and PID control techniques were then evaluated in its ability to track the desired trajectory. It was demonstrated from the study that the PID controller provides the least steady state error as well as a reasonably fast settling time.

An Investigation on the Effect of Lateral Motion on Normal Forces Acting on Each Tires for Nonholonomic Vehicle

Stability of vehicle has been the topic of interest among researchers for decades. Research conducted on vehicle stability relies on the vehicle’s lateral and longitudinal dynamics. In order to determine the longitudinal and lateral force acting on tires, the normal force that acts on the tire is required. Furthermore, the forces generated to move the vehicle are dependent on the vehicle’s mass. Smaller force is generated if the mass is low and vice versa. Therefore, in this paper, the vehicle modelling is conducted to determine the effect of lateral motion on the normal force generated. Dugoff’s tire model and combined vehicle dynamics are used to determine the characteristic of the vehicle. The lateral and longitudinal acceleration generated is used to calculate the normal force generated on each tire. Based on the result, a significant change in normal forces can be observed on each tire when a steering input of 0.05 rad is given. This shows a significant correlation between the lateral motion and normal tire force. Results obtained shows that normal force acting on the left and right side of the tires is affected by the direction of the lateral motion of the vehicle.

Trajectory tracking analysis of planar end-effector upper limb rehabilitation device

Rehabilitation devices have become one of the more sought-after focus areas among researchers in the robotics field, where it could be used to assist patients in the process of stroke recovery. Therefore, the motivation of this thesis is to further investigate the planar end-effector upper limb rehabilitation device as a viable solution for patients with movement disorders, instead of the more expensive alternative of exoskeleton robots. This paper illustrates the mathematical modelling and simulation of a planar end-effector rehabilitation device for the upper limb. The rehabilitation device is of two degrees of freedom, and is used in this research due to its cost effectiveness and practicality. The derivation of the forward and inverse kinematics of the robotic system is established by using the Denavit-Hartenberg algorithm, which is proceeded to be used in the trajectory tracking of the end-effector of the device, as well as the programming of the feedback control system to control the actuators used in the system. The results of the simulation suggest that the mathematical modelling of the system is able to predict the behaviour of the system, which is to be implemented in this robotic device for upper limb rehabilitation.

A Study on the Exposure of Vertical Vibration Towards the Brain on Seated Human Driver Model

Human experiences low-frequency excitation through driving which affect the human’s health. Research had been conducted over the years by using biodynamic model of seated human body to analyze and observe the effect of vehicle vertical vibration towards the subject. However, previous study only focuses on the effect of vertical vibration up to head segment without taking the brain effect into account. In this study, biodynamic model is modelled including the brain to study the impact of vibration on the brain. Spring-mass-damper system are used in this model to represent the biodynamic model of seated human body and compared with previous study. From the model, it shows that the proposed model able to show the significant impact that happen on the skull and brain when vibration is exerted to the human body.

The Control of an Upper Extremity Exoskeleton for Stroke Rehabilitation by Means of a Hybrid Active Force Control

This paper evaluates the efficacy of a hybrid active force control in performing a joint based trajectory tracking of an upper limb exoskeleton in rehabilitating the elbow joint. The plant of the exoskeleton system is obtained via system identification method whilst the PD gains were tuned heuristically. The estimated inertial parameter that enables the AFC disturbance rejection effect is attained by means of a non-nature based metaheuristic optimisation technique known as simulated Kalman filter (SKF). It was demonstrated that the proposed PDAFC scheme outperformed the classical PD algorithm in tracking the prescribed trajectory in the presence of disturbance attributed by the limb weight.