Sensor and actuator fault detection in small autonomous helicopters
G. Heredia
a,
*
, A. Ollero
a
, M. Bejar
b
, R. Mahtani
a
a
Robotics, Vision and Control Group,
1
Engineering School, University of Seville, Camino de los Descubrimientos s/n, 41092 Seville, Spain
b
Robotics, Vision and Control Group, Pablo de Olavide University, Spain
Received 1 March 2007; accepted 19 September 2007
Abstract
The use of autonomous helicopters in civilian applications requires the improvement of safety conditions to avoid potential accidents.
Fault detection and isolation (FDI) plays an important role in this context. This paper presents an actuator and sensor FDI system for
small autonomous helicopters. Fault detection is accomplished by evaluating any significant change in the behaviour of the vehicle with
respect to the fault-free behaviour, which is estimated by using observers. Several types of faults have been considered. The effectiveness
of the proposed approach is demonstrated by means of experimental results and simulations.
2007 Elsevier Ltd. All rights reserved.
Keywords: Fault detection and identification; Autonomous helicopters; UAV; Actuators; Sensors
1. Introduction
Unmanned aerial vehicles are increasingly used in many
applications in which ground vehicles cannot access to the
desired locations due to the characteristics of the terrain
and the presence of obstacles. In many cases the use of aer-
ial vehicles is the best way to approach the objective to get
information or to deploy instrumentation.
Helicopters have high manoeuvrability and hovering
ability. Then, they are well suited to agile target tracking
tasks, as well as to inspect ion and monitoring tasks that
require to maintain a position and to obtain detailed views.
Furthermore, the vertical take-off and landing capabilities
of helicopters is very desirable in many applications.
Remotely piloted helicopters are inherently unstable and
dynamically fast. Even with improved stability augmenta-
tion devices, a skilled, experienced pilot is required to con-
trol them during flight. Autonomous helicopter control is a
challenging task involving a multivariable non-linear open-
loop unstable system with actuator saturations.
Moreover, helicopters do not have the graceful degrada-
tion properties of fixed wing aircrafts or airships in case of
failures. Thus, a failure in any part of the autonomous heli-
copter (actuators, sensors, control system, etc.) can be cat-
astrophic. If the failure is not detected and accounted for,
the helicopter may crash.
Fault detection and isolation (FDI) techniques have
been widely used in process industry to detect faults in
actuators and sensors. If a fault is detected, the structure
of the controller can be changed to get the best possible
response of the system, or even the system can be brought
to an emergency stop.
Fault detection approaches can be classified as model-
free and model-based paradigms. Model-free fault diagno-
sis includes all the techniques that do not rely upon models
of the underlying system, while model-based methods try
to diagnose faults using the redundancy of some mathe-
matical description of the dynamic s.
From the beginning of the seventies, there have been
numerous theoretical advancements in fault diagnostics
based on analytical redundancy (see, for example [1] for a
recent survey). According to this approach, all the informa-
tion on the system can be used to monitor the behaviour of
the plant, including the knowledge about the dynamics.
0957-4158/$ - see front matter 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.mechatronics.2007.09.007
*
Corresponding author. Tel.: +34 954486035; fax: +34 954487340.
E-mail address: guiller@cartuja.us.es (G. Heredia).
1
http://grvc.us.es.
Available online at www.sciencedirect.com
Mechatronics 18 (2008) 90–99
