Quasi Optimal Gait of a Biped Robot with a Rolling Knee Kinematic

In this paper, we address the problem of optimization of trajectories for a new class of biped robot. The knees of this biped are similar as the anthropomorphic one and have a rolling contact between the femur and the tibia. The robot has seven mechanical links and six actuators. The walking gait considered is a succession of single support phase (SSP) and impact of the mobile foot with the ground. Cubic uniform spline functions defined on a time interval express the gait for one step. An energy consumption function and a torques quadratic function are used to compare the new robot with anthropomorphic knees to a conventional robot with revolute joint knees. The minimization of the criteria is made with simplex algorithm. The physical constraints concerning the ZMP and the mobile foot behavior are respectively checked to make a step. Simulation results show that the energy consumption of the new biped with rolling knee contact is less than that of the robot with revolute joint knees.ANR R2A

Optimal Walking of an Underactuated Planar Biped with Segmented Torso

Recently, underactuated bipeds with pointed feet have been studied to achieve dynamic and energy efficient robot walking patterns. However, these studies usually simplify a robot torso as one link, which is different from a human torsos containing 33 vertebrae. In this paper, therefore, we study the optimal walking of a 6-link planar biped with a segmented torso derived from its 5-link counterpart while ensuring that two models are equivalent when the additional torso joint is locked. For the walking, we suppose that each step is composed of a single support phase and an instantaneous double support phase, and two phases are connected by a plastic impact mapping. In addition, the controlled outputs named symmetry outputs capable of generating exponentially stable orbits using hybrid zero dynamics, are adopted to improve physical interpretation. The desired outputs are parameterized by B´ezier functions, with 5-link robot having 16 parameters to optimize and 6-link robot having 19 parameters. According to our energy criterion, the segmented torso structure may reduce energy consumption up to 8% in bipedal walking, and the maximum energy saving is achieved at high walking speeds, while leaving the criteria at low walking speeds remain similar for both robots.China CSC LCF

Influence of frictions on gait optimization of a biped robot with an anthropomorphic knee

This paper presents the energy consumption of a biped robot with a new modelled structure of knees which is called rolling knee (RK). The dynamic model, the actuators and the friction coefficients of the gear box are known. The optimal energy consumption can also be calculated. The first part of the paper is to validate the new kinematic knee on a biped robot by comparing the energy consumption during a walking step of the identical biped but with revolute joint knees. The cyclic gait is given by a succession of Single Support Phase (SSP) followed by an impact. The gait trajectories are parameterized by cubic spline functions. The energetic criterion is minimized through optimization while using the simplex algorithm and Lagrange penalty functions to meet the constraints of stability and deflection of the mobile foot. An analysis of the friction coefficients is done by simulation to compare the human characteristics to the robot with RK. The simulation results show an energy consumption reduction through the biped with rolling knee configuration. The influence of friction coefficients shows the energy consumption of biped robot is close to that of the human.ANR-09-SEGI-011-R2A2; French National Research Agenc

Quasi optimal sagittal gait of a biped robot with a new structure of knee joint

The design of humanoid robots has been a tricky challenge for several years. Due to the kinematic complexity of human joints, their movements are notoriously difficult to be reproduced by a mechanism. The human knees allow movements including rolling and sliding, and therefore the design of new bioinspired knees is of utmost importance for the reproduction of anthropomorphic walking in the sagittal plane. In this article, the kinematic characteristics of knees were analyzed and a mechanical solution for reproducing them is proposed. The geometrical, kinematic and dynamic models are built together with an impact model for a biped robot with the new knee kinematic. The walking gait is studied as a problem of parametric optimization under constraints. The trajectories of walking are approximated by mathematical functions for a gait composed of single support phases with impacts. Energy criteria allow comparing the robot provided with the new rolling knee mechanism and a robot equipped with revolute knee joints. The results of the optimizations show that the rolling knee brings a decrease of the sthenic criterion. The comparisons of torques are also observed to show the difference of energy distribution between the actuators. For the same actuator selection, these results prove that the robot with rolling knees can walk longer than the robot with revolute joint knees.ANR R2A

Quasi Optimal Gait of a Biped Robot with a Rolling Knee Kinematic

In this paper, we address the problem of optimization of trajectories for a new class of biped robot. The knees of this biped are similar as the anthropomorphic one and have a rolling contact between the femur and the tibia. The robot has seven mechanical links and six actuators. The walking gait considered is a succession of single support phase (SSP) and impact of the mobile foot with the ground. Cubic uniform spline functions defined on a time interval express the gait for one step. An energy consumption function and a torques quadratic function are used to compare the new robot with anthropomorphic knees to a conventional robot with revolute joint knees. The minimization of the criteria is made with simplex algorithm. The physical constraints concerning the ZMP and the mobile foot behavior are respectively checked to make a step. Simulation results show that the energy consumption of the new biped with rolling knee contact is less than that of the robot with revolute joint knees.ANR R2A

Quasi optimal walking of a biped robot with anthropomorphic knee

L’article présente la méthodologie d’obtention de trajectoires optimales de marche pour une nouvelle classe de robot bipède. Le robot bipède est constitué de sept corps et possède des genoux anthropomorphes avec un contact roulant entre le fémur et le tibia. La marche est considérée comme une succession de phases de simple support suivi d’un impact. Une optimisation avec un critère énergétique ou sthénique est utilisé et le problème de recherche de trajectoires est transformé en une optimisation paramétrique. Les premiers résultats montrent que le robot étudié consomme moins d’énergie qu’un bipède conventionnel.This article presents the methodology to obtain optimal trajectories of gait for a new class of biped robot. The new robot has seven links and has anthropomorphic knees with a rolling contact between the femur and the tibia. The gait is described like a succession of simple support phase followed by an impact. An optimization with an energetic or sthenic criterion is used and the problem of finding gait is changed in a parametric optimisation. Early results show that the robot studied using less energy than conventional robot.ANR R2A

Marche quasi-optimale d'un robot bipède avec contact roulant au niveau des genoux

L'article présente la méthodologie d'obtention de trajectoires optimales de marche pour une nouvelle classe de robot bipède. Le robot bipède est constitué de sept corps et possède des genoux anthropomorphes avec un contact roulant entre le fémur et le tibia. La marche est considérée comme une succession de phase de simple support suivi d'un impact. Une optimisation utilisant un critère énergétique ou sthénique est utilisé et le problème est transformé en un problème paramétrique. Les premiers résultats montrent que la nouvelle structure consomme moins d'énergie qu'un bipède conventionnel

Study of actuation and energy reduction with an anthropomorphic knee on biped robot

The knee of biped robots has usually one degree of freedom which one is a revolute joint. This work focuses on the study of rolling contact knee. The knee is composed of a cylinder in the extremity of the femur, rolling on another cylindrical surface which is the tibia. Studies have shown that this structure allows to reduce the torque during the gait. Energetic optimization series were made with this structure and for different cylinder radii. The angular trajectories describing the gait are generated by cubic splines functions. The gait is composed of single support phase followed by an impact. The minimization of energetic criterion is realized using the Simplex algorithm of Nelder-Mead. The results show that higher radii of the tibia permit to reduce energy consumption during the gait. The study of new contact surfaces is a way to decrease the energy consumption

Modeling of Rolling Knee Biped Robot

This report presents the dynamic modeling of a planar biped robot. The robot has seven bodies and 9 DOF. Two kinematic configurations are investigated. The first has only revolute joints on all articulation. The second differs by the presence of rolling contact on the knees. All matrices involved in the model are given in explicit form. All the possibilities of contact between the feet and the ground are considered

Quasi optimal walking of a biped robot with anthropomorphic knee

L’article présente la méthodologie d’obtention de trajectoires optimales de marche pour une nouvelle classe de robot bipède. Le robot bipède est constitué de sept corps et possède des genoux anthropomorphes avec un contact roulant entre le fémur et le tibia. La marche est considérée comme une succession de phases de simple support suivi d’un impact. Une optimisation avec un critère énergétique ou sthénique est utilisé et le problème de recherche de trajectoires est transformé en une optimisation paramétrique. Les premiers résultats montrent que le robot étudié consomme moins d’énergie qu’un bipède conventionnel.This article presents the methodology to obtain optimal trajectories of gait for a new class of biped robot. The new robot has seven links and has anthropomorphic knees with a rolling contact between the femur and the tibia. The gait is described like a succession of simple support phase followed by an impact. An optimization with an energetic or sthenic criterion is used and the problem of finding gait is changed in a parametric optimisation. Early results show that the robot studied using less energy than conventional robot.ANR R2A