18 research outputs found
Safe Supervisory Control of Soft Robot Actuators
Although soft robots show safer interactions with their environment than
traditional robots, soft mechanisms and actuators still have significant
potential for damage or degradation particularly during unmodeled contact. This
article introduces a feedback strategy for safe soft actuator operation during
control of a soft robot. To do so, a supervisory controller monitors actuator
state and dynamically saturates control inputs to avoid conditions that could
lead to physical damage. We prove that, under certain conditions, the
supervisory controller is stable and verifiably safe. We then demonstrate
completely onboard operation of the supervisory controller using a soft
thermally-actuated robot limb with embedded shape memory alloy (SMA) actuators
and sensing. Tests performed with the supervisor verify its theoretical
properties and show stabilization of the robot limb's pose in free space.
Finally, experiments show that our approach prevents overheating during contact
(including environmental constraints and human contact) or when infeasible
motions are commanded. This supervisory controller, and its ability to be
executed with completely onboard sensing, has the potential to make soft robot
actuators reliable enough for practical use
Advanced Mobile Robotics: Volume 3
Mobile robotics is a challenging field with great potential. It covers disciplines including electrical engineering, mechanical engineering, computer science, cognitive science, and social science. It is essential to the design of automated robots, in combination with artificial intelligence, vision, and sensor technologies. Mobile robots are widely used for surveillance, guidance, transportation and entertainment tasks, as well as medical applications. This Special Issue intends to concentrate on recent developments concerning mobile robots and the research surrounding them to enhance studies on the fundamental problems observed in the robots. Various multidisciplinary approaches and integrative contributions including navigation, learning and adaptation, networked system, biologically inspired robots and cognitive methods are welcome contributions to this Special Issue, both from a research and an application perspective
Fabrication and Model Based Position Estimation of Novel Laser Processed Shape Memory Alloy Actuator with an Embedded Strain Gauge Sensor
Shape Memory Alloys have sparked great amount of interest in the eld of actuation
over the past decades. Until now, sensorless position estimation of SMA actuators under
dynamic unknown applied stresses has not been feasible due to the complexity of the system
and the number of unknown parameters which the proposed extra information obtained
from the embedded sensor solves. In this thesis, a novel laser processed NiTi Shape Memory
Alloy (SMA) actuator is proposed containing two di erent material compositions in one
monolithic piece of actuator wire. Each of these compositions behaves di erently at room
temperature, one exhibits a shape memory e ect (SME) for actuation, and the other is
pseudo-elastic (PE) which is used to enable an embedded sensor. Fabrication of the wire
included laser processing, heat-treatment, and cold-working procedures. The actuator
wire was subsequently trained to stabilize its properties using iso-stress thermal cycling.
Additionally, a novel model-based sensorless position estimation algorithm is presented.
Proposed model can estimate the position of the actuator under varying applied stresses
with an approximate accuracy of 95% only using dual resistance measurements across the
two di erent material compositions. The proposed actuator has signi cant application in
robotics, wearables, haptics, automotive, and any other application which the mechanical
load is not known in advance. Two simple position and force controller schemes using the
proposed dual-resistance measurement position (and force) estimation are discussed and
the control results presented. The proposed position estimation algorithm is used for the
feedback-signal of a simple PID position and force controller scheme. Moreover, another
novel sensorless position estimation of SMA actuator wires are presented using the power
measurement of the standing wave cause by the re
ection of a high-frequency signal at an
un-terminated end
Bio-inspired robotic control in underactuation: principles for energy efficacy, dynamic compliance interactions and adaptability.
Biological systems achieve energy efficient and adaptive behaviours through extensive autologous and exogenous compliant interactions. Active dynamic compliances are created and enhanced from musculoskeletal system (joint-space) to external environment (task-space) amongst the underactuated motions. Underactuated systems with viscoelastic property are similar to these biological systems, in that their self-organisation and overall tasks must be achieved by coordinating the subsystems and dynamically interacting with the environment. One important question to raise is: How can we design control systems to achieve efficient locomotion, while adapt to dynamic conditions as the living systems do? In this thesis, a trajectory planning algorithm is developed for underactuated microrobotic systems with bio-inspired self-propulsion and viscoelastic property to achieve synchronized motion in an energy efficient, adaptive and analysable manner. The geometry of the state space of the systems is explicitly utilized, such that a synchronization of the generalized coordinates is achieved in terms of geometric relations along the desired motion trajectory. As a result, the internal dynamics complexity is sufficiently reduced, the dynamic couplings are explicitly characterised, and then the underactuated dynamics are projected onto a hyper-manifold. Following such a reduction and characterization, we arrive at mappings of system compliance and integrable second-order dynamics with the passive degrees of freedom. As such, the issue of trajectory planning is converted into convenient nonlinear geometric analysis and optimal trajectory parameterization. Solutions of the reduced dynamics and the geometric relations can be obtained through an optimal motion trajectory generator. Theoretical background of the proposed approach is presented with rigorous analysis and developed in detail for a particular example. Experimental studies are conducted to verify the effectiveness of the proposed method. Towards compliance interactions with the environment, accurate modelling or prediction of nonlinear friction forces is a nontrivial whilst challenging task. Frictional instabilities are typically required to be eliminated or compensated through efficiently designed controllers. In this work, a prediction and analysis framework is designed for the self-propelled vibro-driven system, whose locomotion greatly relies on the dynamic interactions with the nonlinear frictions. This thesis proposes a combined physics-based and analytical-based approach, in a manner that non-reversible characteristic for static friction, presliding as well as pure sliding regimes are revealed, and the frictional limit boundaries are identified. Nonlinear dynamic analysis and simulation results demonstrate good captions of experimentally observed frictional characteristics, quenching of friction-induced vibrations and satisfaction of energy requirements. The thesis also performs elaborative studies on trajectory tracking. Control schemes are designed and extended for a class of underactuated systems with concrete considerations on uncertainties and disturbances. They include a collocated partial feedback control scheme, and an adaptive variable structure control scheme with an elaborately designed auxiliary control variable. Generically, adaptive control schemes using neural networks are designed to ensure trajectory tracking. Theoretical background of these methods is presented with rigorous analysis and developed in detail for particular examples. The schemes promote the utilization of linear filters in the control input to improve the system robustness. Asymptotic stability and convergence of time-varying reference trajectories for the system dynamics are shown by means of Lyapunov synthesis
Volume 3 – Conference
We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics
Group 9 | 11: Mobile applications
Group 10: Special domains
Group 12: Novel system architectures
Group 13 | 15: Actuators & sensors
Group 14: Safety & reliabilit
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 2018 Canadian Society for Mechanical Engineering (CSME) International Congress
Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018
Fundamental concepts and models for the direct problem
This book series is an initiative of the Post Graduate Program in Integrity of Engineering Materials from UnB, organized as a collaborative work involving researchers, engineers, scholars, from several institutions, universities, industry, recognized both nationally and internationally. The book chapters discuss several direct methods, inverse methods and uncertainty models available for model-based and signal based inverse problems, including discrete numerical methods for continuum mechanics (Finite Element Method, Boundary Element Method, Mesh-Free Method, Wavelet Method). The different topics covered include aspects related to multiscale modeling, multiphysics modeling, inverse methods (Optimization, Identification, Artificial Intelligence and Data Science), Uncertainty Modeling (Probabilistic Methods, Uncertainty Quantification, Risk & Reliability), Model Validation and Verification. Each book includes an initial chapter with a presentation of the book chapters included in the volume, and their connection and relationship with regard to the whole setting of methods and models