The high-redundancy actuator (HRA) is a linear displacement actuation system, which consists of a large number of small electromechanical actuation elements arranged in a series and parallel configuration. The performance of a HRA with 9 direct-driven linear electromechanical actuators was analyzed under different fault conditions with the aid of the MATLAB simulation model. The results showed that the HRA has the capability to provide inherent fault-tolerance. Hence, the sudden failure of the system in the presence of fault was avoided. However, the capability of the actuator was found to be reduced gradually depending upon the number of faults.

Introduction

Faulty elements in any engineering system can be a huge hassle. Sometimes, they might cause irrevocable damage to the industries. Particularly, a fault in the safety-critical system can lead to disasters of unimaginable magnitude. So, designing modern engineering systems with a high level of reliability is of utmost importance to avoid any unexpected failures [1]. One important way this can be prevented is by having a fault-tolerance design that can tolerate any malfunctions of the individual components of the system. In general, fault-tolerance can be achieved by adopting a redundancy technique which includes the addition of resources, time or information beyond the normal requirements of the system being operated. In recent years, fault-tolerance has become one of the greatest tools for providing safety to any mechatronic system. The aircraft actuation and nuclear power systems are some of the most important systems that need redundancy to ensure reliability [2]. More recently, the aerospace field significantly increased the use of multi redundant electrical actuation systems to avoid unexpected failures [3,4]. However, in the case of nuclear power systems, hardware redundancy is introduced to confirm a high level of reliability of the control system [5]. Traditionally, the fault-tolerance for the actuation system is attained by connecting two or more identical actuators in parallel and the task to be completed by this group of actuators in parallel, is carried out by any one of the individual actuators from the same group. The fact that each of these actuators has the capability to perform the required task alone enables them to override any faulty actuators [6]. However, these actuators in parallel increases the weight and cost of the system and eventually, reduces the efficiency of the system. Moreover, the use of pure parallel configuration holds no value in the event of jamming/lock-up of an actuator within it.