Torque-Controlled Stepping-Strategy Push Recovery: Design and Implementation on the iCub Humanoid Robot

One of the challenges for the robotics community is to deploy robots which can reliably operate in real world scenarios together with humans. A crucial requirement for legged robots is the capability to properly balance on their feet, rejecting external disturbances. iCub is a state-of-the-art humanoid robot which has only recently started to balance on its feet. While the current balancing controller has proved successful in various scenarios, it still misses the capability to properly react to strong pushes by taking steps. This paper goes in this direction. It proposes and implements a control strategy based on the Capture Point concept [1]. Instead of relying on position control, like most of Capture Point related approaches, the proposed strategy generates references for the momentum-based torque controller already implemented on the iCub, thus extending its capabilities to react to external disturbances, while retaining the advantages of torque control when interacting with the environment. Experiments in the Gazebo simulator and on the iCub humanoid robot validate the proposed strategy

Analytic Model for Quadruped Locomotion Task-Space Planning

Despite the extensive presence of the legged locomotion in animals, it is extremely challenging to be reproduced with robots. Legged locomotion is an dynamic task which benefits from a planning that takes advantage of the gravitational pull on the system. However, the computational cost of such optimization rapidly increases with the complexity of kinematic structures, rendering impossible real-time deployment in unstructured environments. This paper proposes a simplified method that can generate desired centre of mass and feet trajectory for quadrupeds. The model describes a quadruped as two bipeds connected via their centres of mass, and it is based on the extension of an algebraic bipedal model that uses the topology of the gravitational attractor to describe bipedal locomotion strategies. The results show that the model generates trajectories that agrees with previous studies. The model will be deployed in the future as seed solution for whole-body trajectory optimization in the attempt to reduce the computational cost and obtain real-time planning of complex action in challenging environments.Comment: Accepted to be Published in 2019, 41th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Berlin German

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

VARIOUS APPROACHES OF DYNAMIC MODELLING OF BIPED ROBOTIC SYSTEM-A REVIEW

Humans are the most advanced creatures of the nature. Accordingly it can be stated that humanoid robots are the most advanced creatures of human beings. Among the man-made systems such as automobile, hand-phones and multimedia devices, robots of future will hopefully be the most ideal assistants to human beings. During several decades of research, development projects aimed at building bipedal and humanoid robots has been increasing at a rapid rate. A brief review of current activities in the development of bipedal humanoid robotics is provided in this paper. The dynamic modelling of biped robotic system in the current trend is also described. The main objectives for using bipedal robots are introduced and bipedal locomotion as well as its dynamic behaviors in different fields are also considered. The use of dynamics of different kinds of mechanical systems in the field of humanoid robotics is also emphasized. Finally, a list of few projects in this field is provided

Prikaz slobodnog prostora za dvonožne hodajuće robote

Motion planning for biped walking robots is a highly demanding task because of the complex kinematics of such machines and the many degrees of freedom involved. One approach to dealing with this problem is to determine a feasible path in a reduced configuration space of the robot and then to perform the motion planning by searching for an appropriate sequence of steps which allows the locomotion along this path. In this work, a novel method for creating a free space representation for biped walking robots is presented. The method rests upon the approximation of the robot by a set of 3D hulls whose shapes allow efficient determination of feasible paths in a 3D configuration space, involving stepping over obstacles and changing the walking level. The robot’s environment is partitioned into two regions. In the first region, 2D motion planning can be performed, while the complexity of 3D motion planning in the second region can be significantly reduced by considering only a restricted set of paths sufficient for solving a wide range of locomotion tasks.Planiranje kretanja dvonožnih hodajućih robota predstavlja iznimno zahtjevan zadatak zbog složenosti kinematike takvih strojeva i velikog broja stupnjeva slobode gibanja. Jedan pristup tom problemu je da se prvo pronađe izvediva staza u reduciranom konfiguracijskom prostoru robota te da se zatim traži odgovarajući niz koraka koji omogućuje kretanje tom stazom. U ovom radu predstavljena je nova metoda stvaranja prikaza slobodnog prostora za dvonožne hodajuće robote. Metoda se temelji na aproksimaciji robota skupom jednostavnih trodimenzionalnih geometrijskih tijela čiji oblici omogućuju učinkovito određivanje izvedivih staza u 3D konfiguracijskom prostoru, koje mogu uključivati prekoračivanje prepreka te prelazak između hodnih površina različitih visina. Okolina robota dijeli se na dva područja. U prvom području može se primijeniti 2D planiranje koraka, dok se složenost 3D planiranja koraka u drugom području može značajno smanjiti tako što se pri planiranju uzima u obzir samo jedan reducirani skup staza, koji je pak dostatan za rješavanje velikog broja praktičnih zadataka

Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion

Underactuation is ubiquitous in human locomotion and should be ubiquitous in bipedal robotic locomotion as well. This chapter presents a coherent theory for the design of feedback controllers that achieve stable walking gaits in underactuated bipedal robots. Two fundamental tools are introduced, virtual constraints and hybrid zero dynamics. Virtual constraints are relations on the state variables of a mechanical model that are imposed through a time-invariant feedback controller. One of their roles is to synchronize the robot's joints to an internal gait phasing variable. A second role is to induce a low dimensional system, the zero dynamics, that captures the underactuated aspects of a robot's model, without any approximations. To enhance intuition, the relation between physical constraints and virtual constraints is first established. From here, the hybrid zero dynamics of an underactuated bipedal model is developed, and its fundamental role in the design of asymptotically stable walking motions is established. The chapter includes numerous references to robots on which the highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte