A Detumbling Strategy for an Orbital Manipulator in the Post-Grasp Phase

In this paper, we propose a detumbling strategy that stabilizes the motion of a tumbling client satellite using an orbital servicing manipulator, which is the goal of the post-grasp phase. One of the critical aspects in this phase is ensuring that excessive contact forces are not generated at the grasp interface. In addition, space mission requirements might demand a nominal manipulator configuration that is suitable for further manipulation/servicing activities. The proposed strategy allows the detumbling of the client motion while ensuring that the contact forces developed at the grasp interface do not violate a safety threshold. Further, it allows the reconfiguration of the manipulator arm by exploiting the full actuation capability of the manipulator-equipped servicing spacecraft. The controller guarantees joint task convergence in the nullspace of the manipulator's end-effector, and is also valid for kinematically singular configurations of the manipulator. It is further augmented using a quadratic programming based approach to optimally constrain the contact forces. Finally, simulation results for a post-grasp detumbling scenario are shown to validate the effectiveness of the proposed method

Passive Decoupled Multi-Task Controller for Redundant Robots

Kinematic redundancy in robots makes it possible to execute several control tasks simultaneously. As some tasks are usually more important than others, it is reasonable to dynamically decouple them in order to ensure their execution in a hierarchical way or even without any interference at all. The most widely used technique is to decouple the system by feedback linearization. However, that requires actively shaping the inertia and consequently modifying the natural dynamics of the robot. Here we propose a passivity-based multi-task tracking controller that preserves these inertial properties but fully compensates for task-space cross-couplings using external force feedback. Additionally, three formal proofs are provided: uniform exponential stability for trajectory tracking, passivity during physical interaction, and input-to-state-stability. The controller is validated in simulations and experiments and directly compared with the hierarchical PD+ approach and the feedback linearization. The proposed approach is well suited for safe physical human-robot interaction and dynamic trajectory tracking if measurements or estimations of the external forces are available

Design and validation of a system for controlling a robot for 3D ultrasound scanning of the lower limbs

Peripheral arterial disease (PAD) is a common circulatory problem featured by arterial narrowing or stenosis, usually in the lower limbs (i.e. legs). Without sufficient blood supply, in the case of PAD, the patient may suffer from intermittent claudication, or even require an amputation. Due to the PAD’s high prevalence yet low public awareness in the early stages, its diagnosis becomes very important. Among the most common medical imaging technologies in PAD diagnosis, the ultrasound probe has the advantages of lower cost and non-radiation. Traditional ultrasound scanning is conducted by sonographers and it causes musculoskeletal disorders in the operators. In addition, the data obtained from the manual operation are unable for the three-dimensional reconstruction of the artery needed for further study. Medical ultrasound robots release sonographers from routine lifting strain and provide accurate data for three-dimensional reconstruction. However, most existing medical ultrasound robots are designed for other purposes, and are unsuited to PAD diagnosis in the lower limbs. In this study, we present a novel medical ultrasound robot designed for PAD diagnosis in the lower limbs. The robot platform and the system setup are illustrated. Its forward and inverse kinematic models are solved by decomposing a complex parallel robot into several simple assemblies. Singularity issues and workspace are also discussed. Robots need to meet certain accuracy requirements to perform dedicated tasks. Our robot is calibrated by direct measurement with a laser tracker. The calibration method used is easy to implement without requiring knowledge of advanced calibration or heavy computation. The calibration result shows that, as an early prototype, the robot has noticeable errors in manufacturing and assembling. The implemented calibration method greatly improves the robot's accuracy. A force control design is essential when the robot needs to interact with an object/environment. Variable admittance controllers are implemented to adapt the variable stiffness encountered in human-robot interaction. An intuitive implementation of the passivity theory is proposed to ensure that the admittance model possesses a passivity property. Finally, experiments involving human interaction demonstrate the effectiveness of the proposed control design

14th Conference on Dynamical Systems Theory and Applications DSTA 2017 ABSTRACTS

From Preface: This is the fourteen time when the conference “Dynamical Systems – Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and the Ministry of Science and Higher Education. It is a great pleasure that our invitation has been accepted by so many people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcome nearly 250 persons from 38 countries all over the world. They decided to share the results of their research and many years experiences in the discipline of dynamical systems by submitting many very interesting papers. This booklet contains a collection of 375 abstracts, which have gained the acceptance of referees and have been qualified for publication in the conference proceedings [...]

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version