Workshop outline (A full-day workshop)

(List below is not in the final sequence of presentation)

Notice for Workshop Registration

1) Conference registrants can sign up for workshops directly through the registration site at ACC 2012 Registration Site

2) For workshop-only registration (i.e., registering for a workshop without registering for the conference), please contact the Registration Chair at (gchiu (at) purdue.edu) before the workshop on June 26, 2012 with your name, e-mail address, and PaperPlaza PIN.

Part I: 8:30am - 6:00pm - Fairmont Queen Elizabeth, Montreal, Hochelaga 5 Room

Part II: 6:00pm - 6:45pm - Concordia University, 1515 St. Catherine W, EV s2.355

* Morning:

Workshop Descriptions

Introduction to Fault-tolerant Control and Cooperative Control: Motivation, Concept, History, Existing and Future Developments, and Applications to a Multiple Quadrotor UAVs Testbed (Dr. Zhang)

Unmanned systems including Unmanned Aerial Vehicles (UAVs) are gaining more and more attention during the last few years due to their important contribution and cost effective application in several tasks such as surveillance, search, rescue, military and security applications. A team of researchers at the Department of Mechanical and Industrial Engineering of Concordia University, with the support from three Canadian-based industrial partners (Quanser Inc., Opal-RT Technologies Inc., and Numerica Technologies Inc.), have been working on a Networked Fault-Tolerant Cooperative Autonomous Vehicles (NFTCAV) research project as well as for Flight Control Systems and Fault Diagnosis and Fault Tolerant Control Systems courses teaching using multiple quadrotor helicopter UAVs. The main objective of the project is to provide theoretical and experimental results on on-line and on-line UAV modeling, cooperative decision-making and tasks assignment, trajectory and path planning, formation flight, fault diagnosis and fault-tolerant control, and at the same time to transfer quickly the research outcomes to the undergraduate and graduate courses teaching. A set of unmanned vehicles testbeds with several quadrotor UAVs have been built at the Department of Mechanical and Industrial Engineering of Concordia University based on the financial support of NSERC (Natural Sciences and Engineering Research Council of Canada) since 2007, with the help of Quanser Inc. for the testbed development. In this presentation, brief introduction to the concept on fault-tolerant control and cooperative control will be given first. Historical development and new challenges in this active research area will be outlined. An overview of our past, current and future research activities and research outcomes on fault diagnosis, fault-tolerant control, path and trajectory planning/re-planning and cooperative control with applications to unmanned systems including the quadrotor helicopter UAV, NASA's GTM fixed-wing UAV and an Airbus A380 model UAV, will be presented.

A Passive Fault Tolerant Flight Control for Maximum Allowable Vertical Tail Damaged Aircraft (Dr. Liu)

It investigates a passive fault tolerant control to aircraft that suffers from vertical tail damage. A novel notion of damage degree is introduced to parameterize the damaged flight dynamics model. It is applied to seek the maximum allowable damage degree (tolerance capacity) stabilizable by the proposed passive fault tolerant and backup control under a linearized model. The design algorithms are presented and illustrated through numerical simulations on one aircraft model. Furthermore, the impact of potential control saturation is taken into account in the proposed design and a set of design parameters are tuned such that the maximum allowable damage degree is bounded, represented as the so-called critical damage degree.

Sliding Mode Schemes for Fault Detection and Fault Tolerant Control (Dr. Edwards)

Sliding mode methods have been historically studied because of their strong robustness properties to a certain class of uncertainty. This is achieved by employing nonlinear control/injection signals to force the system trajectories to attain in finite time a motion along a surface in the state-space. The associated reduced order dynamics, whilst constrained to the surface is called the sliding motion, and possess strong robustness properties. This talk will consider how these ideas can be exploited for fault detection (specifically fault signal estimation) and subsequently fault tolerant control. The talk will also describe an application of these ideas to aerospace systems. It will describe flight simulator results associated with the EL-AL 1862 Bijlmermeer scenario studied as part of the GARTEUR AG16 action group on fault tolerant control. The controller design was carried out without any knowledge of the types of faults/failures occurring on the aircraft, and employs sliding mode methods. The results demonstrate the successful real-time implementation of the proposed fault tolerant control scheme on a motion flight simulator configured to represent the EL-AL aircraft.

Fault-tolerant Control of a Fixed-wing UAV Testbed (Dr. Chen)

In order to guarantee the reliability and performance of UAV, there are some redundancies in the design of UAV. But too many redundancies will require a hard condition on the payload of UAV. This presentation aims at providing recommendation on what kind of faults in actuators are forbidden that we should make a backup in the design of UAV and what kind of faults are allowed without affecting the performance of UAV. It is common that when design a feedback controller the physical property of system are often overlooked. In this presentation, we put the 'physics' of UAV back in the design of fault tolerant controller for fixed-wing test-bed and we try to find what are the maximum faults that can be tolerated in this kind of UAV. Theory of cascaded system and under-actuated systems are used to realize the hovering of VTOL. Simulation results with different faults are also presented to validate the effectiveness of the presented fault tolerant controller.

Tools for Teaching Autonomous Unmanned Vehicle Systems (Mr. Fulford)

Unmanned Vehicle Systems (UVS) are growing in popularity across a broad spectrum of applications such as search and rescue, military, mining, and environmental surveillance. Likewise, the UVS research community is growing and there is an increasing demand for novel hardware and software platforms on which to develop and test UVS algorithms and controllers. To meet the growing demand for new technologies to teach and develop the next-generation unmanned systems, this workshop presents the latest technologies for UVS teaching and research. As part of this workshop, we will review how leading universities have integrated autonomous unmanned systems into their teaching and research programs using this state-of-the-art rapid controls prototyping framework and open-architecture data acquisition hardware designed for unmanned systems. This workshop will also demonstrate how innovative hardware-in-the-loop systems can be used to augment virtual 3D UVS missions in order to teach fundamental control concepts while motivating students with exciting, real-world UVS applications. More advanced concepts will be introduced with specific focus on tools for autonomous unmanned vehicle systems. Demonstrations will show autonomous unmanned vehicle missions planned out and executed in simulations with rendered 3D visualization.

Health Management for Persistent Surveillance: Theory and Practical Results (Dr. Rabbath)

We present the problem of coverage of an area with a team of aerial robotic drones. The drones self-position themselves to maintain coverage, thus removing the burden of multi-vehicle control and management from the human operator. The drones have the ability to adapt their position in case adverse events take place during the course of an operation. Adverse events include the loss of one or more robots, inter-vehicle communication problems, intruders entering the area being monitored, and loss of effectiveness of one or more robots. We present the step-by-step design of such intelligent system, and importantly illustrate the performances obtained by means of indoor, controlled experiments with a small team of quadrotor drones. Videos are an integral part of the presentation. Hardcopy notes will be given to the audience. In this presentation, the concept of health management is defined, and current systems enabling team coordination in case of health problems are discussed. Part of the presentation relates to the first book on safety and reliability for teams of robotic drones recently published by the speaker, and entitled Safety and Reliability in Cooperating Unmanned Aerial Systems.

Design of Fault-tolerant Control Methods Based on Reliability (Dr. Theilliol & Dr. Zhang)

Faults or failures such as defects in components, instruments, controllers and/or control loop can cause undesired reactions and consequences such as damages to technical parts of the plant, to human life or to the environment. Traditionally, the objective of Fault Tolerant Control System (FTCS) is to maintain its current performance close to the desired one and preserve its stability conditions despite of component and/or instrument faults; in some circumstances a reduced performances may have to be accepted as a trade-off leading to a sub-optimal outcome. Design of control systems to achieve fault-tolerance for closed-loop control of safety-critical systems has been an active area of investigation for many years. It becomes more and more clear that there are certain trades-offs between achievable normal performance and fault-tolerance capability. However, despite of the many efforts in control community, most of the contributions did not consider or take into account the reliability of components, algorithms or soft computing structures to guarantee such performance and to reduce the gap between nominal and faulty case. This contribution aims at presenting new and innovative research results on how to design Fault Tolerant Control Systems with particular attention to consider and combine reliability analysis in the design procedure and/or real-time control synthesis. Current and future research is presented in order to solve the above challenging research problems devoted to safety-critical systems such as flying vehicles, unmanned aerial vehicles (UAVs), missiles, airships etc.

Multiple UAS Operations: Toward Verifiable Autonomy (Dr. Tsourdos)

There are many applications using autonomous systems such as unmanned aerial vehicles: surveillance/attacking, traffic monitoring, search and rescue, and so on. Nowadays the applications and missions become so various and complex that the systems become more complicated. Those missions are related not only with civil purpose but also with military one so usually safety-critical. Diverse sensors are equipped in the systems for safety and redundancy, furthermore, a group of autonomous systems has been recently considered for more effective mission performance. As the systems are complicated, reliability of systems must be verified at the design level. There are some methods to verify the reliability of systems at the design level such as a simulation in a virtual environment, a test with a mock-up, and formal methods. Firstly, test with a mock-up costs a lot of money and time to perform and doesn’t always guarantee the safety during it processes. Simulation costs less money and time than for the test, but it is not always easy to consider all the possible scenarios and situations. In contrast formal methods are based on solid mathematical techniques and offer quantifiable answers to questions related with reliability of systems, and thus they are widely used to verify the safety-critical or high-autonomy systems. Model-checking is an automatic technique based on formal methods for verifying finite state system. It checks whether the system satisfy the properties or not automatically. There are three parts of process in model-checking: modeling, specification, and verification. This contribution aims at presenting new and innovative research results on how to model multiple UAS systems as multi-agent systems using formal methods to captures their specifications that would enable to validate their performance and finally how to verify their performance in the presence of faults.

References (Author with bold face is one of the speakers at this workshop):

- Halim Alwi, Christopher Edwards, and Chee Pin Tan, Fault Detection and Fault Tolerant Control using Sliding Modes, Springer, 2011.

- Antonios Tsourdos, Brian White, and Madhavan Shanmugavel, Cooperative Path Planning of Unmanned Aerial Vehicles, Wiley, 2011.

- Christopher Edwards, Thomas Lombaerts, and Hafid Smaili (Eds.) Fault Tolerant Flight Control: A Benchmark Challenge, Springer, 2010.

- Camille-Alain Rabbath and Nicolas Lechevin, Safety and Reliability in Cooperating Unmanned Aerial Systems, World Scientific Publishing, 2010.

- Hassan Noura, Didier Theilliol, Jean-Christophe Ponsart, and Abbas Chamseddine, Fault-tolerant Control Systems: Design and Practical Applications, Springer, 2009.

- Mufeed Mahmoud, Jin Jiang, and - Youmin Zhang-, Active Fault Tolerant Control Systems: Stochastic Analysis and Synthesis, Springer, 2003.

- Youmin Zhang and Jin Jiang, Bibliographical Review on Reconfigurable Fault-tolerant Control Systems, Annual Reviews in Control, vol. 32, no. 2, Dec. 2008, pp. 229-252 (Ranked No. 1 in the "Top 10 Cited" and No. 6 in "Most Downloaded" articles published in the last five years at the journal).

- Other references will be provided during the workshop to participants.