High integrity actuation system with embedded intelligence

(TSB Technology Programme Grant, 04/2007-09/2010. PI – Professor T X Mei, in collaboration with Intelligent Motion Control, Stored Energy Technology and Total Motion Systems)

The provision of actuation in safety critical control systems normally demands a high level of hardware redundancies with the use of multiple actuators, sensors and electronics in order to meet the strict system integrity requirement. The actuators tend to be far more expensive in control systems than the sensors and electronics and are more difficult to tackle with conventional analytical redundant approaches. In many cases, the prospect of the much increased cost often delays or even prohibits practical applications of advanced technologies which would otherwise provide much needed performance gains, efficiency improvement and other savings.

The key research of this project is to develop a practical solution that will provide the necessary control actions (i.e. actuation) and in the mean time satisfy the expected safety and reliability requirements, but minimize the use of hardware redundancies to reduce the component count in the use of actuators and associated controls. The project aims to meet the difficult challenges through the intelligent exploitation of the inherent properties of electric actuators and integrated FDI and control methods.
The Principle Investigator at Salford University was the initiator of the project and has provided the original ideas which the project is based on. The University of Salford is the only academic partner, responsible for driving the technology and for providing critical research input.

The project is funded by TSB (Technology Strategy Board, UK) through their Technology Programme Grant and supported by industrial partners.

Principle of steer-by-wire

Fault Tolerant Actuator Test-Rig

Enhanced safety and reliability for trains through fault tolerant control

EPSRC/RRUK grant, 10/2009 -09/2012. Principle Investigator – Professor T X Mei

Active controls for railway vehicles can provide much better performance, improve operation efficiency and reduce track damages. However the introduction of additional control system and associated electronics into the traditional mechanical system will have to meet the demanding requirements for safety and reliability in rail industry.

This project seeks to investigate fault tolerant control methods that will be able to ensure the safety and improve the overall reliability of rail vehicles, paving the way for an increased industrial acceptance and a wider application of advanced active systems. A key research objective is to develop practical solutions that do not demand a high level of redundancy and hence reduce the system costs.

The project is a natural extension of the leading research work at Salford University in the areas of high-integrity actuation and fault detection methods.

This project is funded by EPSRC (UK) via Rail Research UK grant.

System integration for rail wheelset steering and traction control

EPSRC grant, 02/2002-08/2003. Principle Investigator – Professor T X Mei

The suspension and guidance systems for the control of vehicle dynamics deal with issues such as vehicle stability, running behaviour and passenger ride comfort. These have been traditionally achieved through the use of passive components. However, active controls via mechatronic and electronic components can push the boundaries and achieve far beyond what is possible with mechanical suspensions. More recent research has shown that wheelsets can be controlled actively in a manner that the adverse forces at the wheel-rail contact which exist with passive or mechanical solutions are significantly reduced. Extensive studies have concentrated upon individual active components to provide particular functions and their development has been focussed on issues at the sub-system level, e.g. the design conflict between ride quality improvement and actuation requirement for the secondary active suspensions.

This project carries out a feasibility study of a systems approach that will bring together the active steering of wheelset and traction control which interact at the wheel-rail contact points, and it is based upon a long term prospect where active wheelset control will be used for rail vehicles and an integrated control for the two sub-systems will then become inevitable in order to ensure the stability and performance of the system. As the dynamics of a railway vehicle is known to be highly interactive, it is essential to understand properly how the structure dynamics and active functions will affect one another; and what adverse effect the interactions will have on the overall performance of the vehicle. The research has helped to establish a rigorous design methodology for the development of active control for railway wheelsets that are also equipped with traction motors.

This project is funded by UK Research Council EPSRC.

Re-adhesion control for AC traction systems, PhD project, 2003-06

Supervisor – Professor T X Mei

Wheel slip is a difficult problem in traction control systems which occurs when applied tractive effort exceeds the level of maximum adhesion (friction) available at the wheel-rail interface, e.g. in poor weather conditions or with contaminated tracks. Apart from the potential impact on normal operations of a rail network, the wheel slip/slide causes undesirable wear to both wheel/track surfaces and increases the cost of maintenance. Most conventional wheel slip protection (or re-adhesion control) schemes detect and control the slip ratio (relative speed between a wheel and the train) to be below a pre-tuned limit and in more extremely cases to control the wheel rotational acceleration below a threshold as an additional measure, but there are a number of known performance constraints.

This project investigates a novel mechatronic solution for the slip detection and re-adhesion control of traction systems in railway vehicles, which explores the changes in dynamic behaviour of railway wheelsets as an indirect indicator of contact conditions. The proposed approach offers a simple and effective method to maximise the use of adhesion available at the wheel-rail contact interface which is essential for the safe and reliable railway operations.

The project is funded by UK ORS Award and Tetley & Lipton award

Condition monitoring of nonlinear systems via multiple Kalman filters, PhD project, 2008-11

Supervisor – Professor T X Mei

Model-based methods are widely studied for applications in FDI and general condition monitoring, but are more suited to tackle linear time invariant systems and can be problematic for systems with very complex and non-linear properties. This project studies a multiple Kalman filters approach that divide a non-linear problem into a number of linearised models that represent an approximation of different conditions. A selected number of Kalman filters are then used to assess the likelihood of a ‘best’ match of the condition of the system is operating at any particular instance to achieve the desired condition monitoring.

This project is supported financially by Pakistani Government through a postgraduate scholarship programme.

Intelligent fault detection for dynamic systems, PhD project, 2005-09

Supervisor – Professor T X Mei

On line fault detection and condition monitoring for dynamic systems are becoming increasingly important because of the potential benefits to detect component failures at their early stages, to prevent further deterioration in performance as well as to ensure timely repair/replacement of faulty components. In the long term, the availability of reliable condition monitoring systems can replace scheduled regular services with maintenance on demand - leading to substantial savings in the total life cycle costs.

This project carries out a fundamental study into a completely new approach, originally proposed by the principle investigator, which offers a simple but very effective means for condition monitoring. The principle is highly innovative which focuses on the comparison of dynamic behaviours between different parts of a system where a symmetry exists in structure and/or in the components used (under the normal condition) and explores changes in dynamic interactions caused by the occurrence of an abnormal condition or component failure. Using a railway vehicle as a case study, the study shows that the proposed condition monitoring technique provides a much improved sensitivity to fault(s), compared to more conventional methods, and is much more robust against uncertainties of external condition changes. The principle is now being studied for condition monitoring for other applications.

The project is financially supported by the Centenary Award (for excellent overseas student)