Modelling and control of a high redundancy actuator

The high redundancy actuation concept is a completely new approach to fault tolerance, and it is important to appreciate that it provides a transformation of the characteristics of actuators so that the actuation performance (capability) degrades slowly rather than suddenly failing, even though individual elements themselves fail. This paper aims to demonstrate the viability of the concept by showing that a highly redundant actuator, comprising a relatively large number of actuation elements, can be controlled in such a way that faults in individual elements are inherently accommodated, although some degradation in overall performance will inevitably be found. The paper introduces the notion of fault-tolerant systems and the highly redundant actuator concept. Then a model for a two by two configuration with electro-mechanical actuation elements is derived. Two classical control approaches are then considered based on frequency domain techniques. Finally simulation results under a number of faults show the viability of the approach for fault accommodation without re-configuratio

HRA - Intrinsically fault tolerant actuation through high redundancy

The aim of this paper is to summarise on-going research into a new method of providing fault tolerant actuators for high-integrity and/or safety-critical applications. The High Redundancy Actuator (HRA) project aims to exploit a large number of very small actuation elements to make up a single large actuator. This is in contrast to current technology where a relatively low level of functional redundancy is used. The HRA elements are configured and controlled in such a way that faults in individual elements are inherently accommodated without resulting in a failure of the complete actuation system. The HRA project research challenges are outlined and progress to-date is discussed

DECISIVE: Designing Critical Systems With Iterative Automated Safety Analysis

Systems safety is becoming increasingly challenging due to the presence of ever-more complex applications. Safety analysis is an important aspect of Safety-Critical Systems Engineering (SCSE) to discover problems in system design that can potentially lead to hazards with risks that may lead to accidents. Performing safety analysis requires significant manual effort — its automation has become the research focus in the critical system domain due to the increasing complexity of systems and the emergence of open adaptive systems. In this paper, we propose a novel methodology in which automated safety analysis drives the design of safety-critical systems. We delve into the specifics of our approach and the supporting tools. Additionally, we discuss the method to integrate our approach into the current practice of SCSE. The experimental results reveal that the proposed approach with its supporting tool promotes the efficiency of safety analysis significantly, whilst maintaining high degrees of correctness, coverage and scalability

LQG control of a high redundancy actuator

A high redundancy actuator, comprising a relatively large number of actuation elements, is being developed for safety critical applications. Some classical control results have previously been reported and this paper will focus on evaluation of the LQG control design. Three different design approaches will be presented and compared under different types of typical faults in the sub-actuation elements. Overall a LQG design using a physically motivated reduced order model appears to be the best approach

HRA - Intrinsically Fault Tolerant Actuation through High Redundancy

The aim of this paper is to summarise on-going research into a new method of providing fault tolerant actuators for high-integrity and/or safety-critical applications. The High Redundancy Actuator (HRA) project aims to exploit a large number of very small actuation elements to make up a single large actuator. This is in contrast to current technology where a relatively low level of functional redundancy is used. The HRA elements are configured and controlled in such a way that faults in individual elements are inherently accommodated without resulting in a failure of the complete actuation system. The HRA project research challenges are outlined and progress to-date is discussed

HRA - Intrinsically fault tolerant actuation through high redundancy

The aim of this paper is to summarise on-going research into a new method of providing fault tolerant actuators for high-integrity and/or safety-critical applications. The High Redundancy Actuator (HRA) project aims to exploit a large number of very small actuation elements to make up a single large actuator. This is in contrast to current technology where a relatively low level of functional redundancy is used. The HRA elements are configured and controlled in such a way that faults in individual elements are inherently accommodated without resulting in a failure of the complete actuation system. The HRA project research challenges are outlined and progress to-date is discussed