Position-based kinematics for 7-DoF serial manipulators with global configuration control, joint limit and singularity avoidance

This paper presents a novel analytic method to uniquely solve inverse kinematics of 7 degrees-of-freedom manipulators while avoiding joint limits and singularities. Two auxiliary parameters are introduced to deal with the self-motion manifolds: the global configuration (GC), which specifies the branch of inverse kinematics solutions; and the arm angle (ψ) that parametrizes the elbow redundancy within the specified branch. The relations between the joint angles and the arm angle are derived, in order to map the joint limits and singularities to arm angle values. Then, intervals of feasible arm angles for the specified target pose and global configuration are determined, taking joint limits and singularities into account. A simple metric is proposed to compute the elbow position according to the feasible intervals. When the arm angle is determined, the joint angles can be uniquely calculated from the position-based inverse kinematics algorithm. The presented method does not exhibit the disadvantages inherent to the use of the Jacobian matrix and can be implemented in real-time control systems. This novel algorithm is the first position-based inverse kinematics algorithm to solve both global and local manifolds, using a redundancy resolution strategy to avoid singularities and joint limits.This work was partially supported by the NETT Project [FP7-PEOPLE-2011-ITN-289146]; and Foundation for Science and Technology, Portugal [grant number SFRH/BD/86499/2012].info:eu-repo/semantics/publishedVersio

Autonomy Infused Teleoperation with Application to BCI Manipulation

Robot teleoperation systems face a common set of challenges including latency, low-dimensional user commands, and asymmetric control inputs. User control with Brain-Computer Interfaces (BCIs) exacerbates these problems through especially noisy and erratic low-dimensional motion commands due to the difficulty in decoding neural activity. We introduce a general framework to address these challenges through a combination of computer vision, user intent inference, and arbitration between the human input and autonomous control schemes. Adjustable levels of assistance allow the system to balance the operator's capabilities and feelings of comfort and control while compensating for a task's difficulty. We present experimental results demonstrating significant performance improvement using the shared-control assistance framework on adapted rehabilitation benchmarks with two subjects implanted with intracortical brain-computer interfaces controlling a seven degree-of-freedom robotic manipulator as a prosthetic. Our results further indicate that shared assistance mitigates perceived user difficulty and even enables successful performance on previously infeasible tasks. We showcase the extensibility of our architecture with applications to quality-of-life tasks such as opening a door, pouring liquids from containers, and manipulation with novel objects in densely cluttered environments

Automated sequence and motion planning for robotic spatial extrusion of 3D trusses

While robotic spatial extrusion has demonstrated a new and efficient means to fabricate 3D truss structures in architectural scale, a major challenge remains in automatically planning extrusion sequence and robotic motion for trusses with unconstrained topologies. This paper presents the first attempt in the field to rigorously formulate the extrusion sequence and motion planning (SAMP) problem, using a CSP encoding. Furthermore, this research proposes a new hierarchical planning framework to solve the extrusion SAMP problems that usually have a long planning horizon and 3D configuration complexity. By decoupling sequence and motion planning, the planning framework is able to efficiently solve the extrusion sequence, end-effector poses, joint configurations, and transition trajectories for spatial trusses with nonstandard topologies. This paper also presents the first detailed computation data to reveal the runtime bottleneck on solving SAMP problems, which provides insight and comparing baseline for future algorithmic development. Together with the algorithmic results, this paper also presents an open-source and modularized software implementation called Choreo that is machine-agnostic. To demonstrate the power of this algorithmic framework, three case studies, including real fabrication and simulation results, are presented.Comment: 24 pages, 16 figure

Workspace and singularity determination of a 7-DoF wrist-partitioned serial manipulator towards graffiti painting

Els robots estan sent utilitzats, cada cop més, en la realització de tasques en la indústria. Molts d'ells també són dissenyats pensats per a realitzar les tasques de la llar. En general, els robots són dissenyats per a facilitar el dia a dia del éssers humans. Però quan es tracta d'obres artístiques, és menys comú trobar-se robots realitzant-les. Nosaltres pretenem sortir de la norma mitjançant l'ús d'un robot per a pintar un grafiti. La motivació per a aconseguir-ho convergeix en la formulació de dues preguntes: "Quin és el volum de treball d'un robot, quan l'orientació del seu efector final està fixada?" i "Donat un pla arbitrari, quina és la major àrea de treball lliure de singularitats en aquest?" Aquesta tesi proposa un mètode per a l'obtenció de les singularitats de posició en un pla qualsevol d'un manipulador serial amb un canell esfèric. El mètode s'ha obtingut mitjançant la combinació d'un mètode de determinació de singularitats de posició, el qual està basat en una tècnica per al decoplat de manipuladors que presenten un canell esfèric, i un algorisme branch-and-prune per a la resolució de sistemes d'equacions. S'ha obtingut el volum de treball d'un manipulador serial de 7 graus de llibertat a través d'un enfocament de cinemàtica directa. Es presenta una metodologia per a obtenir el volum de treball del manipulador serial quan el seu efector final té l'orientació constant i s'aplica per a obtenir aproximacions per al cas de certes orientacions. Es mostra com les singularitats poden ser analitades a través de separar-les en singularitats de posició i d'orientació. el mètode proposat formula i resol les equacions que determinen les singularitats de posició. Pel que fa a les singularitats d'orientació, es mostra que poden ser evitades sense perdre una quantitat significant de volum de treball, des del punt de vista de la posició.Los robots estén siendo utilizados, cada vez más, en la realización de tareas en la industria. Muchos de ellos también son diseñados pensados para realizar las tareas del hogar. En general, los robots son diseñados para facilitar el día a día de los seres humanos. Pero cuando se trata de obras artíticas, es menos común encontrarse a robots realizándolas. Nosotros pretendemos salirnos de lo común mediante el uso de un robot para pintar un grafiti. La motivación por lograrlo converge en la formulación de dos preguntas: "¿Cuál es el volumen de trabajo de un robot, cuando la orientación de su efector final está fijada?" y "Dado un plano arbitrario, ¿cuál es la mayor área de trabajo libre de singularidades en éste?" Esta tesis propone un método para la obtención de las singularidades de posición en un plano cualquiera de un manipulador serial con una muñeca esférica. El método ha sido obtenido mediante la combinación de un método de determinación de singularidades de posición, el cual está basado en una técnica para el decoplado de manipuladores que presentan una muñeca esférica, y un algoritmo branch-and-prune para la resolución de sistemas de ecuaciones. Se ha obtenido el volumen de trabajo de un manipulador serial de 7 grados de libertad a través de un enfoque de cinemática directa. Se presenta la metodología para obtener el volumen de trabajo del manipulador serial cuando su efector final tiene una orientación constante y se aplica para obtener aproximaciones para el caso de ciertas orientaciones. Se muestra cómo las singularidades pueden ser analizadas a través de separarlas en singularidades de posición y de orientación. El método propuesto formula y resuelve las ecuaciones que determinan las singularidades de posición. En cuanto a las singularidades de orientación, se muestra que pueden ser evitadas sin perder una cantidad significante de volumen de trabajo, desde el punto de vista de la posición.Robots are overtaking every day more tasks in the industry. A lot of them are even designed for performing household chores. In general, robots are designed to facilitate the day-to-day of human beings. But when it comes to artistic tasks, it is less usual to see robots performing them. We pretend to stay out of the crowd by using a robot to paint a graffiti. The motivation to achieve this task converges into the statement of two questions: "What is the workspace of a robot, when the orientation of its end-effector is fixed?" and "For a given plane, what is the largest singularity free surface on it?". This thesis proposes a method for the computation of the position singularities of a wrist-partitioned serial manipulator for a given plane. The method is obtained from the combination of a position singularity determination method, which is based on the decoupling technique of a wrist-partitioned manipulator, and a branch-and-prune algorithm for the resolution of systems of equations. The workspace of a 7-DoF serial manipulator is obtained by a forward kinematics approach. A methodology to obtain the constant orientation workspace of a serial manipulator is presented and applied to get approximations for some specific orientations. It is shown how singularities can be analyzed by decoupling them into position singularities and orientation singularities. The proposed method formulates and solves the equation that determines the position singularities. In the case of the orientation singularities, it is shown that they can be avoided without losing a significant amount of the workspace's volume, from the point of view of the position.Outgoin

Bio-Inspired Motion Strategies for a Bimanual Manipulation Task

Steffen JF, Elbrechter C, Haschke R, Ritter H. Bio-Inspired Motion Strategies for a Bimanual Manipulation Task. In: International Conference on Humanoid Robots (Humanoids). 2010