https://users.encs.concordia.ca/~ymzhang/publications/ARC32-2-98Zhang_pp.229-252.pdf

Bibliographical review on reconfigurable fault-tolerant control systems

With the continuous increase in complexity and expense of industrial systems, there is less tolerance for performance degradation, productivity decrease, and safety hazards, which greatly necessitates to detect and identify any kinds of potential abnormalities and faults as early as possible and implement real-time fault-tolerant operation for minimizing performance degradation and avoiding dangerous situations. During the last four decades, fruitful results have been reported about fault diagnosis and fault-tolerant control methods and their applications in a variety of engineering systems. The three-part survey paper aims to give a comprehensive review of real-time fault diagnosis and fault-tolerant control, with particular attention on the results reported in the last decade. In this paper, fault diagnosis approaches and their applications are comprehensively reviewed from model- and signal-based perspectives, respectively.

/pdf/a-survey-of-fault-diagnosis-and-fault-tolerant-techniques-9uuf1uqysf.pdf

A Survey of Fault Diagnosis and Fault-Tolerant Techniques—Part I: Fault Diagnosis With Model-Based and Signal-Based Approaches

This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Adaptive Control

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1065&context=usafresearch

A review of space robotics technologies for on-orbit servicing

Animals sustain the ability to operate after injury by creating qualitatively different compensatory behaviors. Although such robustness would be desirable in engineered systems, most machines fail in the face of unexpected damage. We describe a robot that can recover from such change autonomously, through continuous self-modeling. A four-legged machine uses actuation-sensation relationships to indirectly infer its own structure, and it then uses this self-model to generate forward locomotion. When a leg part is removed, it adapts the self-models, leading to the generation of alternative gaits. This concept may help develop more robust machines and shed light on self-modeling in animals.

https://science.sciencemag.org/content/sci/314/5802/1118.full.pdf

Resilient machines through continuous self-modeling.

In this paper, the problem of impedance control of dual-arm cooperative manipulators is studied. A general impedance control scheme is adopted, which encompasses a centralized impedance control strategy, aimed at conferring a compliant behavior at the object level, and a decentralized impedance control, enforced at the end-effector level, aimed at avoiding large internal loading of the object. Remarkably, the mechanical impedance behavior is defined in terms of geometrically consistent stiffness. The overall control scheme is based on a two-loop arrangement, where a simple proportional integral derivative inner motion loop is adopted for each manipulator, while an outer loop, using force and moment measurements at the robots wrists, is aimed at imposing the desired impedance behaviors. The developed control scheme is experimentally tested on a dual-arm setup composed of two 6-DOF industrial manipulators carrying a common object. The experimental investigation concerns the four different controller configurations that can be achieved by activating/deactivating the single impedance controllers.

/pdf/six-dof-impedance-control-of-dual-arm-cooperative-41vzye06mf.pdf

Six-DOF Impedance Control of Dual-Arm Cooperative Manipulators

A new approach to 6-DOF impedance control is proposed, where the end-effector orientation displacement is derived from the rotation matrix expressing the mutual orientation between the compliant frame and the desired frame. An alternative Euler angles-based description is proposed which mitigates the effects of representation singularities. Then, a class of angle/axis representations are considered to derive the dynamic equation for the rotational part of a 6-DOF impedance at the end effector, using an energy-based argument. The unit quaternion representation is selected to further analyze the properties of the rotational impedance. The resulting impedance controllers are designed according to an inverse dynamics strategy with contact force and moment measurements, where an inner loop acting on the end-effector position and orientation error is adopted to confer robustness to unmodeled dynamics and external disturbances. Experiments on an industrial robot were carried out, and the results of case studies are discussed.

Six-DOF impedance control based on angle/axis representations

This paper presents the design, control, and experimental validation of a novel fully-actuated aerial robot for physically interactive tasks, named Tilt-Hex. We show how the Tilt-Hex, a tilted-propeller hexarotor is able to control the full pose (position and orientation independently) using a geometric control, and to exert a full-wrench (force and torque independently) with a rigidly attached end-effector using an admittance control paradigm. An outer loop control governs the desired admittance behavior and an inner loop based on geometric control ensures pose tracking. The interaction forces are estimated by a momentum based observer. Control and observation are made possible by a precise control and measurement of the speed of each propeller. An extensive experimental campaign shows that the Tilt-Hex is able to outperform the classical underactuated multi-rotors in terms of stability, accuracy and dexterity and represent one of the best choice at date for tasks requiring aerial physical interaction.

/pdf/6d-physical-interaction-with-a-fully-actuated-aerial-robot-3jyrotqb79.pdf

6D physical interaction with a fully actuated aerial robot

In this paper, a distributed controller-observer schema for tracking control of the centroid and of the relative formation of a multi-robot system with first-order dynamics is presented. Each robot of the team uses a distributed observer to estimate the overall system state and a motion control strategy for tracking control of time-varying centroid and formation. Proof of the overall convergence of the controller-observer schema for different kinds of connection topologies, as well as for the cases of unsaturated and saturated control inputs is presented. In particular, the solution is proven to work in the case of strongly connected non-switching topologies and in the case of balanced strongly connected switching topologies. In order to complete the work, the approach is validated by experimental tests with a team of five wheeled mobile robots.

/pdf/decentralized-time-varying-formation-control-for-multi-robot-3n7yr1mc9w.pdf

Decentralized time-varying formation control for multi-robot systems

This paper proposes an approach to the design of control laws for underwater vehicles that takes into account the hydrodynamic effects affecting the tracking performance. To this aim, a suitable adaptive action based on appropriate kinematic transformations between the earth-fixed frame and the vehicle-fixed frame is developed. The proposed control law adopts quaternions to represent attitude errors, thus avoiding representation singularities that occur when using instead Euler angles. The stability of the designed control law is demonstrated by means of a Lyapunov-based argument. In view of practical implementation, a simplified version of the developed control law is also proposed that compensates only the persistent hydrodynamic terms, namely, the restoring generalized forces and the ocean current. Finally, the tracking performance of the proposed control law is analyzed in comparison to that of other existing control laws available in the literature. The obtained simulation results confirm the effectiveness of the proposed technique.

Fabrizio Caccavale

Papers

Six-DOF Impedance Control of Dual-Arm Cooperative Manipulators

Six-DOF impedance control based on angle/axis representations

6D physical interaction with a fully actuated aerial robot

Decentralized time-varying formation control for multi-robot systems

A novel adaptive control law for underwater vehicles