Masri Baharom

Design of full electric power steering with enhanced performance over that of hydraulic power-assisted steering

This paper presents a method of designing a full electrical power steering system to replace a hydraulic power-assisted steering system with improved performance and benefits including energy saving, improved steering ‘feel’, simpler construction and environmental gain. The designed performance of the electrical power steering system represented an ideal hydraulic power-assisted steering power boost curve which was mathematically modelled to provide the required control characteristic for the electrical power steering system, including variation in the perceived power assistance with the vehicle’s forward speed. A full electrical power steering system provides all the torque necessary to steer the wheels, and the steering feel is artificially generated by an electric ‘feedback’ motor which provides resistance to the driver’s input. The performance of the electrical power steering system described in this paper was enhanced by manipulating the reactive torque to the driver’s input at the steering wheel so that it depended upon the driving conditions. Full-vehicle software models were generated using ADAMS/car software based on an actual car fitted with hydraulic power-assisted steering and full electrical power steering. The simulation results from both models were compared, and it is concluded that the steering performances of both systems were similar but the steering feel of the full electrical power steering system could be tuned to provide improved feedback to the driver in use. The performance of the full electrical power steering system could be further improved with the introduction of a controller to manipulate the steering feel during undesired conditions.

Design concepts and analysis of a semi-active steering system for a passenger car

Abstract The fundamentals and preliminary analyses of an innovative future technology referred to as ‘semi-active steering’ (SAS) are presented in this article. The proposed steering system configuration is similar to a conventional electrical power-assisted steering with the replacement of the rigid steering shaft with a low stiffness resilient shaft (LSRS), the presence of which allows ‘active control’ to be performed on vehicles similar to the concept of full steer-by-wire (SBW). But, unlike SBW, the LSRS is an integral part of the system characteristics. The advantages of the semi-active system in comparison with SBW and other conventional systems are demonstrated. A mathematical model to predict the mechanical properties of the LSRS has been developed, and experiments were conducted on a medium-sized car fitted with an LSRS to verify that vehicle stability and drivability can be ensured in the event of active system failure. The results have indicated that the vehicle was stable and safe to be driven at low speeds, and is predicted to be driveable and safe at higher speeds. It is concluded that an SAS system of this type has the potential to improve the safety of SBW systems.

Analysis of the properties of a steering shaft used as a back-up for a steer-by-wire system during system failure

Abstract An analysis is presented to determine the best selection criteria for the properties of a steering shaft to be used as a back-up apparatus for a steer-by-wire (SBW) system during system failure. The properties of interest are the steering-shaft stiffness and its damping coefficient. A mathematical model representing the failed state of an SBW system is derived, and a set of experiments to validate the model is presented. Once the model had been validated, further predictions of the cars handling behaviour for a range of steering-shaft properties and different road speeds were completed by simulations in MATLAB/Simulink. A minimum stiffness which did not cause the car to become unstable owing to overshoot was determined, and the minimum acceptable damping coefficient value was derived. It is concluded that the suggested stiffness and damping coefficient values increased the steering ratio, and the results of further investigations are presented, which confirm that the vehicle is safe to be driven in the event of SBW system failure if the recommended shaft properties are used.

Development of force feedback in steering systems for virtual driving simulator

In steer-by-wire (SBW) vehicles, the elimination of the rigid mechanical column shaft would require the system to generate an artificial feedback torque which should produce similar driving feeling and behavior as to the conventional steering system. The objective of this study is to evaluate the characteristics of force feedback inside SBW vehicle for driving simulator utilizing Logitech G27 steering wheel. The model of the system is developed in Matlab/Simulink/3D Animation. A J-turn test is performed to see the resulting handwheel torque and its effect on the vehicle dynamic. The evaluation shows that the results are reasonable such that the driver of the simulator can feel the similar forces coming from the real road.

Underwater gliders control strategies: A review

Underwater Gliders (UGs) are a type of Autonomous Underwater Vehicle (AUV) that uses buoyancy engines, an energy efficient locomotion, primarily for oceanography. In this paper, control strategies for existing underwater gliders are reviewed. A total of 50 papers indexed by Scopus with keywords control and underwater gliders were reviewed from 1989 to 2014. The majority of gliders use classical controllers, which cannot dynamically compensate for un-modeled hydrodynamic forces and unknown variations in water current and wind. With increasing operational depths and larger payloads, control strategies will become an increasingly important aspect for these gliders. Control strategies implemented in underwater gliders were reviewed and alternative control strategies are proposed.