Nonlinear dynamic inversion for redundant systems using the EKF formalism

This paper presents an allocator for over-actuated systems based on the Extended Kalman Filter (EKF). The main advantages of the proposed approach are the greater flexibility in handling the constraints and its real-time capabilities. Based on the literature, theoretic convergence results, which ensure the convergence towards the local optimal values looked for, are presented. Another formulation of the kinematic equations of redundant systems that meet some constraints is also proposed in order to go through and/or avoid singularities. The two formulations are combined and applied to an academic example (a planar redundant manipulator arm)

A Cartesian Space Approach to Teleoperate a Slave Robot with a Kinematically Dissimilar Redundant Manipulator

Due to the inability of humans to interact with certain unstructured environments,telemanipulation of robots have gained immense importance. One of the primary tasks in telemanipulating robots remotely, is the effective manipulation of the slave robot using the master manipulator. Ideally a kinematic replica of the slave manipulator is used as the master to provide a joint-to-joint control to the slave. This research uses the 7-DOF Whole Arm Manipulator© (WAM) as the master manipulator and a 6-DOF Titan as the slave manipulator. Due to the kinematic dissimilarity between the two, a Cartesian space position mapping technique is adapted in which the slave is made to follow the same trajectory as the end effector of the master with respect to its reference frame. The main criterion in undertaking this mapping approach is to provide a convenient region of operation to the human operator. Various methods like pseudo inverse, Jacobian transpose and Damped least squares have been used to perform the inverse kinematics for the Titan. Joint limit avoidance and obstacle avoidance constraints were used to perform the inverse kinematics for the WAM and thereby remove the redundancy. Finally a joint volume limitation constraint (JVLC) was adopted which aims at providing the operator, a comfortable operational space in union with the master manipulator. Each inverse methodfor the Titan was experimentally tested and the best method identified from thesimulation results and the error analysis. Various experiments were also performed for the constrained inverse kinematics for the WAM and results were simulated. RoboWorks© was used for simulation purposes

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Dynamically Feasible Trajectories of Fully-Constrained Cable-Suspended Parallel Robots

Cable-Driven Parallel Robots employ multiple cables, whose lengths are controlled by winches, to move an end-effector (EE). In addition to the advantages of other parallel robots, such as low moving inertias and the potential for high dynamics, they also provide specific advantages, such as large workspaces and lower costs. Thus, over the last 30 years, they have been the object of academic research; also, they are being employed in industrial applications. The main issue with cable actuation is its unilaterality, as cables must remain in tension: if they become slack, there is a risk of losing control of the EE's pose. This complicates the control of cable-driven robots and is among the most studied topics in this field. Most previous works resort to extra cables or rigid elements pushing on the EE to guarantee that cables remain taut, but this complicates robot design. An alternative is to use the gravitational and inertial forces acting on the EE to keep cables in tension. This thesis shows that the robot's workspace can be greatly increased, by considering two model architectures. Moreover, practical limits to the feasibility of a motion, such as singularities of the kinematic chain and interference between cables, are considered. Even if a motion is feasible, there is no guarantee that it can be performed with an acceptable precision in the end-effector's pose, due to the inevitable errors in the positioning of the actuators and the elastic deflections of the structure. Therefore, a set of indexes are evaluated to measure the sensitivity of the end-effector's pose to actuation errors. Finally, the stiffness of one of the two architectures is modeled and indexes to measure the global compliance of the robot due to the elasticity of the cables are presented.I robot paralleli a cavi impiegano cavi, la cui lunghezza è controllata da argani, per muovere un elemento terminale o end-effector (EE). Oltre ai vantaggi degli altri robot paralleli, come basse inerzie in movimento e la possibilità di raggiungere velocità e accelerazioni elevate, possono anche fornire vantaggi specifici, come ampi spazi di lavoro e costi inferiori. Pertanto, negli ultimi 30 anni, questi robot sono stati oggetto di ricerche accademiche e stanno trovando applicazione anche in campo industriale. Il problema principale dell'azionamento mediante cavi è che è unilaterale, poiché i cavi possono essere tesi ma non compressi: quando diventano laschi, si rischia di perdere il controllo della posa dell'EE. Questo complica il controllo dei robot ed è uno dei temi più studiati nel settore. Gli studi compiuti sinora ricorrono prevalentemente a cavi addizionali o a elementi rigidi che spingono sull'EE per garantire che i cavi rimangano tesi, ma questo complica la progettazione dei robot. Un'alternativa è sfruttare le forze gravitazionali e inerziali che agiscono sull'EE per mantenere i cavi in tensione. Questa tesi dimostra che, in questo caso, lo spazio di lavoro del robot può essere notevolmente aumentato, applicando questo concetto a due architetture modello. Inoltre, vengono considerati i limiti imposti all'effettiva realizzabilità di un movimento, come le singolarità della catena cinematica e l'interferenza tra i cavi. Anche se un movimento è fattibile, non è garantito che si possa eseguire con precisione accettabile, a causa degli inevitabili errori di posizionamento degli attuatori e delle deformazioni elastiche della struttura. Si valutano quindi alcuni indici per misurare la sensibilità della posizione dell'elemento terminale agli errori di azionamento. Infine, è modellata la rigidezza di una delle due architetture proposte e sono presentati indici per misurare la cedevolezza globale del robot dovuta all'elasticità dei cavi

Advanced Strategies for Robot Manipulators

Amongst the robotic systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. Modern manipulators are designed complicatedly and need to do more precise, crucial and critical tasks. So, the simple traditional control methods cannot be efficient, and advanced control strategies with considering special constraints are needed to establish. In spite of the fact that groundbreaking researches have been carried out in this realm until now, there are still many novel aspects which have to be explored

Proceedings of the NASA Conference on Space Telerobotics, volume 1

The theme of the Conference was man-machine collaboration in space. Topics addressed include: redundant manipulators; man-machine systems; telerobot architecture; remote sensing and planning; navigation; neural networks; fundamental AI research; and reasoning under uncertainty

Sensing Methods for Soft Robotics

Soft robots exhibit complex behaviors that emerge from deliberate compliance in the actuators and structure. This compliance allows soft robots to passively conform to the constraints of their environment and to the objects they are manipulating. Many soft robots are actuated by the flexible expansion of hermetically sealed volumes. Systems based on these principles are lightweight, flexible and have low reflected inertia. This makes them inherently safe in physical human robot interaction. Moreover, the sealed actuators and flexible joints are well-suited to work in harsh environments where external contaminates could breach the dynamic seals of rotating or sliding shafts. Accurate motion control remains a highly challenging task for soft robotic systems. Precise models of the actuation dynamics and environmental interactions are often unavailable. This renders open-loop control impossible, while closed-loop control suffers from a lack of suitable feedback. Conventional motion sensors, such as linear or rotary encoders, are difficult to adapt to robots that lack discrete mechanical joints. The rigid nature of these sensors runs contrary to the aspirational benefits of soft systems. Other proposed soft sensor solutions are still in their infancy and have only recently been used for motion-control of soft robots. This dissertation explores the design and use of inductance-based sensors for the estimation and control of soft robotic systems. These sensors are low-cost, lightweight, easy-to-fabricate and well-suited for the conditions that soft systems can best exploit. The inquiry of this dissertation is conducted both theoretically and experimentally for Fiber-Reinforced Elastomeric Enclosures (including McKibben muscles) and bellows actuators. The sensing of each actuator type is explored through models, design analyses and experimental evaluations. The results demonstrate that inductance-based sensing is a promising technology for these otherwise difficult-to-measure actuators. By combining sensing and actuation into a single component, the ideas presented in this work provide a simple, compact and lightweight way to create and control motion in soft robotic systems. This will enable soft systems that can interactively engage with their environment and their human counterparts.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138590/1/wfelt_1.pd

Heterojen robotlarla dinamik formasyon kontrolü.

Formation control in robotics is a growing topic where research works are mainly geared towards heterogeneous swarm colonies under either decentralized control or limited centralization. Swarm robotics where decentralization is applied, nevertheless assume that the agents are capable of getting global information about the whole swarm.Moreoverintheliterature,formationcontrolisgenerallydoneforknownfixed shapesthatcanbedefinedmathematically. Howevernodynamicallychangingshapes areenvisagedandnoshapetransitionsareclearlyhandledinthoseworks. Weattempt to bring a clear impact to the literature by focusing on tracking and realising formation shapes under dynamically changing formation shape demands. Furthermore,in our thesis work, we focus on robot colonies composed of heterogeneous robots of differentdynamicsandsensorcapabilitiesunderdecentralizeddynamicallychanging formation control. These robots are able furthermore, to just possess local mutual interactions only with their close-by neighboring agents. In our approach communications of each agent with its neighbors converges to information about the whole colony based on graph theory. Simulations in our work are generated using the Gazebo environment by modelling a rough territory. Hardware applications which implements the methods discussed in this thesis work are also developed. These applications are evaluated as proof of concept work which illustrates that the methods can be implemented in real time applications.M.S. - Master of Scienc

Proceedings of the NASA Conference on Space Telerobotics, volume 4

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotic technology to the space systems planned for the 1990's and beyond. Volume 4 contains papers related to the following subject areas: manipulator control; telemanipulation; flight experiments (systems and simulators); sensor-based planning; robot kinematics, dynamics, and control; robot task planning and assembly; and research activities at the NASA Langley Research Center

MATLAB

This excellent book represents the final part of three-volumes regarding MATLAB-based applications in almost every branch of science. The book consists of 19 excellent, insightful articles and the readers will find the results very useful to their work. In particular, the book consists of three parts, the first one is devoted to mathematical methods in the applied sciences by using MATLAB, the second is devoted to MATLAB applications of general interest and the third one discusses MATLAB for educational purposes. This collection of high quality articles, refers to a large range of professional fields and can be used for science as well as for various educational purposes