Second order sliding mode observers for the ADDSAFE actuator benchmark problem

Abstract

This paper presents the evaluation process and results associated with two different fault detection and diagnosis (FDD) schemes applied to two different aircraft actuator fault benchmark problems. Although the schemes are different and bespoke for the problem being addressed, both are based on the concept of a second order sliding mode. Furthermore both designs are considered as 'local' in the sense that a localized actuator model is used together with local sensor measurements. The schemes do not involve the global aircraft equations of motion, and therefore have low order. The first FDD scheme is associated with the detection of oscillatory failure cases (OFC), while the second scheme is aimed at the detection of actuator jams/runaways. For the OFC benchmark problem, the idea is to estimate the OFC using a mathematical model of the actuator in which the rod speed is estimated using an adaptive second order exact differentiator. For the jam/runaway actuator benchmark problem, a more classical sliding mode observer based FDD scheme is considered in which the fault reconstruction is obtained from the equivalent output error injection signals associated with a second order sliding mode structure. The results presented in this paper summarize the design process from tuning, testing and finally industrial evaluation as part of the ADDSAFE project.

Fault estimation and adaptive fault tolerant control for dynamic systems based on the second-order sliding mode observer

“…Among the existing methods of fault estimation, the observer-based fault estimation is a prevailing approach. 5–20 To name a few, adaptive observers were proposed to achieve fault estimation. 5–7 However, only uniformly bounded fault estimation is obtained, and then adaptive observers are not easy to achieve high-accuracy fault estimation.…”

“…Particularly, sliding mode method has been applied to the European project untitled ADDSAFE. 16–20 However, the discontinuous term of the conventional sliding mode observer (CSMO) inevitably introduces chattering. It is well acknowledged that chattering not only increases energy consumption but also easily excites unmodeled dynamics of system, which may lead to instability or even collapse of the observer error dynamic system.…”

Advanced sensor fault detection and isolation for electro-mechanical flight actuators

“…The detection of faults in classical hydraulic flight actuators is an intensively studied topic in literature. Advanced methods as LPV techniques in [2] and [3], sliding mode observers in [4], nonlinear observer based approaches in [5] and H ∞ techniques in [6] have been applied to monitor hydraulic actuator systems of modern aircraft locally, i.e., by looking at the input-output dynamics of the actuator. System wide monitoring approaches using the input-output behavior of the overall aircraft dynamics are provided by [7] and [8].…”

Efficient Nonlinear Actuator Fault Reconstruction System

“…Different approaches are proposed based on the actuator model. 13,14,15 There are different actuator faults which have different influences on the aircraft. Oscillatory Failure Case (OFC) is a failure case which may be generated by the electrical flight control system.…”