Actuation of robotic systems is still an open question and represents a big challenge. Demanding performances including high power to mass ratio, capability of producing high power at low speed within a small-occupied volume are some of the key issues that required careful consideration. These criteria aimed to increase autonomy of humanoid robots. In this paper, a novel hydrostatic transmission actuator is proposed. The proposed actuator is controlled by displacement and has capacities for energy storage. This leads to an optimal solution in terms of power consumption. First, the proposed hydrostatic actuation principle is explained. A simplified hydraulic scheme to illustrate the energy storage capability is then provided. A mathematical model of the proposed solution is detailed showing our ability to access to the payload “jerk”. The built prototype is presented and its properties are outlined. Finally, a prototype of the actuator and the preliminary results of the actuator performance are presented, demonstrating the novelty of our solution.

Designing and control of biped robot are still open questions. Design of ankle joint which is considered one of the more compact with high power capacity and low weight is a big challenge. The very important role played by this joint during walking, makes its design and control the first step of having a robust walking biped. In this paper, a novel three dof hybrid mechanisms has been proposed. This mechanism is actuated hydraulically and uses cable technology for power transmission. The proposed solution fulfils the requirements induced by both geometrical and biomechanical constraints. At first, the geometrical and kinematics properties of the proposed solution have been developed. A simulation tool has been built using ADAMS software and used to carry out early design dimensioning of the several components. Singularity study is detailed showing the advantage of this new solution. Control method has been proposed and tested. Finally manufactured prototype of this solution is presented with preliminary results showing the performances of the mechanism. This mechanism is a part of an International patent accepted at INPI- France.

This paper deals with a research work aimed to develop a new three degrees of freedom (DOF) mechanism for humanoid robots. The main idea is to build hybrid (3DOF) mechanism, which avoids the drawbacks of the serial and parallel mechanisms. The new solution has to merge the advantages of both classical (serial and parallel) structures in order to achieve optimal performances. The proposed mechanism can be used as a solution for several modules in humanoid robot. The hip mechanism is taken as an example to illustrate the contribution of this paper. To evaluate the performances of the system, simulation of this new mechanism is carried out with Adams software. Geometrical and Kinematic models are developed and included in the simulation tool. Based on biomechanical data, analysis of the new kinematic structure is carried out. The design of the proposed solution is then described. Finally the first prototype developed for the HYDROi¿D robot's hip is presented. This mechanism is a part of an International patent accepted at INPI- France.

The purpose of the research addressed in this paper concerns a comparative study of two expressions of the time scale parameter for continuous time recurrent neural network (CTRNN): a classical time constant expression, and a sigmoid one. Their influence on the stability, the convergence speed and the generalization ability of a Backpropagation through time (BPTT) learning algorithm, will be discussed. Firstly, three mathematical conclusions related to the propagation and learning equations are deduced. Then these conclusions are validated on experiments carried out on a real biped robot. Through the identification of the balancing behavior under different robot torso motions, the sigmoid expression will be shown to get the best learning results.