31 research outputs found
Torque Controlled Locomotion of a Biped Robot with Link Flexibility
When a big and heavy robot moves, it exerts large forces on the environment
and on its own structure, its angular momentum can varysubstantially, and even
the robot's structure can deform if there is a mechanical weakness. Under these
conditions, standard locomotion controllers can fail easily. In this article,
we propose a complete control scheme to work with heavy robots in torque
control. The full centroidal dynamics is used to generate walking gaits online,
link deflections are taken into account to estimate the robot posture and all
postural instructions are designed to avoid conflicting with each other,
improving balance. These choices reduce model and control errors, allowing our
centroidal stabilizer to compensate for the remaining residual errors. The
stabilizer and motion generator are designed together to ensure feasibility
under the assumption of bounded errors. We deploy this scheme to control the
locomotion of the humanoid robot Talos, whose hip links flex when walking. It
allows us to reach steps of 35~cm, for an average speed of 25~cm/sec, which is
among the best performances so far for torque-controlled electric robots.Comment: IEEE-RAS International Conference on Humanoid Robots (Humanoids
2022), IEEE, Nov 2022, Ginowan, Okinawa, Japa
Crocoddyl: An Efficient and Versatile Framework for Multi-Contact Optimal Control
We introduce Crocoddyl (Contact RObot COntrol by Differential DYnamic Library), an open-source framework tailored for efficient multi-contact optimal control. Crocoddyl efficiently computes the state trajectory and the control policy for a given predefined sequence of contacts. Its efficiency is due to the use of sparse analytical derivatives, exploitation of the problem structure, and data sharing. It employs differential geometry to properly describe the state of any geometrical system, e.g. floating-base systems. We have unified dynamics, costs, and constraints into a single concept-action-for greater efficiency and easy prototyping. Additionally, we propose a novel multiple-shooting method called Feasibility-prone Differential Dynamic Programming (FDDP). Our novel method shows a greater globalization strategy compared to classical Differential Dynamic Programming (DDP) algorithms, and it has similar numerical behavior to state-of-the-art multiple-shooting methods. However, our method does not increase the computational complexity typically encountered by adding extra variables to describe the gaps in the dynamics. Concretely, we propose two modifications to the classical DDP algorithm. First, the backward pass accepts infeasible state-control trajectories. Second, the rollout keeps the gaps open during the early "exploratory" iterations (as expected in multiple-shooting methods). We showcase the performance of our framework using different tasks. With our method, we can compute highly-dynamic maneuvers for legged robots (e.g. jumping, front-flip) in the order of milliseconds
Whole Body Model Predictive Control with a Memory of Motion: Experiments on a Torque-Controlled Talos
This paper presents the first successful experiment implementing whole-body model predictive control with state feedback on a torque-control humanoid robot. We demonstrate that our control scheme is able to do whole-body target tracking, control the balance in front of strong external perturbations and avoid collision with an external object. The key elements for this success are threefold. First, optimal control over a receding horizon is implemented with Crocoddyl, an optimal control library based on differential dynamics programming, providing state-feedback control in less than 10 msecs. Second, a warm start strategy based on memory of motion has been implemented to overcome the sensitivity of the optimal control solver to initial conditions. Finally, the optimal trajectories are executed by a low-level torque controller, feedbacking on direct torque measurement at high frequency. This paper provides the details of the method, along with analytical benchmarks with the real humanoid robot Talos
Génération de mouvement en robotique mobile et humanoïde
Generation of locomotion motions in mobile robotics has been studied in the academic world for several decades. The theory concerning the modeling and control of wheeled robots is largely mature. However, the actual implementation of these models in real conditions requires further studies. In this thesis, we present three projects using three different types of mobile robots. In each case, we begin with an analysis of the required qualities of a motion in a particular context, whether artistic or industrial, and end with the presentation of the algorithmic and software architectures implemented, particularly in the context of exhibitions of several months, where the public is invited to share the space of evolution of robots. The realization of these projects shows that some technological choices seem insignificant at the time of the design of the robots are decisive in the final stages of production. One can extrapolate this remark from these mobile robots with two or three degrees of freedom towards humanoid robots which can have several tens. The classical strategy of first designing the mechatronic architecture of humanoid robots and then raising the question of their control has reached its limits, as illustrated, for example, by their energy consumption and the difficulty to obtain dynamic walking motions on these robots, yet designed for the purpose of walking. From a global perspective of robot design, we propose a system of codesign, where it is possible to simultaneously optimize the mechanical design and the controllers of a robot. This system is firstly tested by various examples as proof of concept. It is then applied to the comparison of rigid and elastic actuators on different biped robots, then to the study of the impact of the stabilization of the head on the general stabilization of the body and finally to the design of a prototype of semi-passive walker.La gĂ©nĂ©ration de mouvements de locomotion en robotique mobile est Ă©tudiĂ©e dans le monde acadĂ©mique depuis plusieurs dĂ©cennies. La thĂ©orie concernant la modĂ©lisation et le contrĂŽle des robots Ă roues est largement mature. Cependant, la mise en Ćuvre effective de ces modĂšles dans des conditions rĂ©elles demande des Ă©tudes complĂ©mentaires. Dans cette thĂšse, nous prĂ©sentons trois projets mettant en Ćuvre trois diffĂ©rents types de robots mobiles. Nous dĂ©butons dans chaque cas par une analyse sur les qualitĂ©s recherchĂ©es dâun mouvement dans un contexte particulier, quâil soit artistique ou industriel, et terminons par la prĂ©sentation des architectures algorithmiques et logicielles mises en Ćuvre, notamment dans le cadre dâexpositions de plusieurs mois, oĂč le public est invitĂ© Ă partager lâespace dâĂ©volution de robots. La rĂ©alisation de ces projets montre que certains choix technologiques semblant insignifiants au moment de la conception des robots sont dĂ©terminants dans les derniĂšres Ă©tapes de la production. On peut extrapoler cette remarque depuis ces robots mobile Ă deux ou trois degrĂ©s de libertĂ© vers des robots humanoĂŻdes pouvant en avoir plusieurs dizaines. La stratĂ©gie classique qui consiste Ă concevoir, dans un premier temps, lâarchitecture mĂ©catronique des robots humanoĂŻdes, pour se poser ensuite la question de leur contrĂŽle, atteint ses limites, comme le montrent par exemple la consommation Ă©nergĂ©tique et la difficultĂ© dâobtenir des mouvements de marche dynamique sur ces robots, pourtant conçus dans le but de marcher. Dans une perspective globale de conception des robots marcheurs, nous proposons un systĂšme de codesign, oĂč il est possible dâoptimiser simultanĂ©ment la conception mĂ©canique et les contrĂŽleurs dâun robot.
Generation of motion in mobile and humanoid robotics
La gĂ©nĂ©ration de mouvements de locomotion en robotique mobile est Ă©tudiĂ©e dans le monde acadĂ©mique depuis plusieurs dĂ©cennies. La thĂ©orie concernant la modĂ©lisation et le contrĂŽle des robots Ă roues est largement mature. Cependant, la mise en Ćuvre effective de ces modĂšles dans des conditions rĂ©elles demande des Ă©tudes complĂ©mentaires. Dans cette thĂšse, nous prĂ©sentons trois projets mettant en Ćuvre trois diffĂ©rents types de robots mobiles. Nous dĂ©butons dans chaque cas par une analyse sur les qualitĂ©s recherchĂ©es dâun mouvement dans un contexte particulier, quâil soit artistique ou industriel, et terminons par la prĂ©sentation des architectures algorithmiques et logicielles mises en Ćuvre, notamment dans le cadre dâexpositions de plusieurs mois, oĂč le public est invitĂ© Ă partager lâespace dâĂ©volution de robots. La rĂ©alisation de ces projets montre que certains choix technologiques semblant insignifiants au moment de la conception des robots sont dĂ©terminants dans les derniĂšres Ă©tapes de la production. On peut extrapoler cette remarque depuis ces robots mobile Ă deux ou trois degrĂ©s de libertĂ© vers des robots humanoĂŻdes pouvant en avoir plusieurs dizaines. La stratĂ©gie classique qui consiste Ă concevoir, dans un premier temps, lâarchitecture mĂ©catronique des robots humanoĂŻdes, pour se poser ensuite la question de leur contrĂŽle, atteint ses limites, comme le montrent par exemple la consommation Ă©nergĂ©tique et la difficultĂ© dâobtenir des mouvements de marche dynamique sur ces robots, pourtant conçus dans le but de marcher. Dans une perspective globale de conception des robots marcheurs, nous proposons un systĂšme de codesign, oĂč il est possible dâoptimiser simultanĂ©ment la conception mĂ©canique et les contrĂŽleurs dâun robot..Generation of locomotion motions in mobile robotics has been studied in the academic world for several decades. The theory concerning the modeling and control of wheeled robots is largely mature. However, the actual implementation of these models in real conditions requires further studies. In this thesis, we present three projects using three different types of mobile robots. In each case, we begin with an analysis of the required qualities of a motion in a particular context, whether artistic or industrial, and end with the presentation of the algorithmic and software architectures implemented, particularly in the context of exhibitions of several months, where the public is invited to share the space of evolution of robots. The realization of these projects shows that some technological choices seem insignificant at the time of the design of the robots are decisive in the final stages of production. One can extrapolate this remark from these mobile robots with two or three degrees of freedom towards humanoid robots which can have several tens. The classical strategy of first designing the mechatronic architecture of humanoid robots and then raising the question of their control has reached its limits, as illustrated, for example, by their energy consumption and the difficulty to obtain dynamic walking motions on these robots, yet designed for the purpose of walking. From a global perspective of robot design, we propose a system of codesign, where it is possible to simultaneously optimize the mechanical design and the controllers of a robot. This system is firstly tested by various examples as proof of concept. It is then applied to the comparison of rigid and elastic actuators on different biped robots, then to the study of the impact of the stabilization of the head on the general stabilization of the body and finally to the design of a prototype of semi-passive walker
transHumUs: A poetic experience in mobile robotics
International audiencetransHumUs is an artistic work recently exhibited at the 56th Venice Biennale. The work aims at freeing trees from their roots. How to translate this poetic ambition into technological terms? This paper reports on the setup and the implementation of the project. It shows how state of the art mobile robotics technology can contribute to contemporary art development. The challenge has been to design original mobile platforms carrying charges of three tones, while moving noiseless according to tree metabolism, in operational spaces populated by visitors
A Simulation Framework for Simultaneous Design and Control of Passivity Based Walkers
International audienceIn this paper, we propose a simulation framework which simultaneously computes both the design and the control of bipedal walkers. The problem of computing a design and a control is formulated as a single large-scale parametric optimal control problem on hybrid dynamics with path constraints (e.g. non sliding and non slipping contact constraints). Our framework relies on state-of-the-art numerical optimal control techniques and efficient computation of the multi-body rigid dynamics. It allows to compute both the parametrized model and the control of passive walkers on different scenarios, in only few seconds on a standard computer. The framework is illustrated by several examples which highlight the interest of the approach
Introducing Force Feedback in Model Predictive Control
International audienceIn the literature about model predictive control (MPC), contact forces are planned rather than controlled. In this paper, we propose a novel paradigm to incorporate effort measurements into a predictive controller, hence allowing to control them by direct measurement feedback. We first demonstrate why the classical optimal control formulation, based on position and velocity state feedback, cannot handle direct feedback on force information. Following previous approaches in force control, we then propose to augment the classical formulations with a model of the robot actuation, which naturally allows to generate online trajectories that adapt to sensed position, velocity and torques. We propose a complete implementation of this idea on the upper part of a real humanoid robot, and show through hardware experiments that this new formulation incorporating effort feedback outperforms classical MPC in challenging tasks where physical interaction with the environment is crucial
Introducing Force Feedback in Model Predictive Control
International audienceIn the literature about model predictive control (MPC), contact forces are planned rather than controlled. In this paper, we propose a novel paradigm to incorporate effort measurements into a predictive controller, hence allowing to control them by direct measurement feedback. We first demonstrate why the classical optimal control formulation, based on position and velocity state feedback, cannot handle direct feedback on force information. Following previous approaches in force control, we then propose to augment the classical formulations with a model of the robot actuation, which naturally allows to generate online trajectories that adapt to sensed position, velocity and torques. We propose a complete implementation of this idea on the upper part of a real humanoid robot, and show through hardware experiments that this new formulation incorporating effort feedback outperforms classical MPC in challenging tasks where physical interaction with the environment is crucial