This paper presents a lightly weighted hydraulic actuator that is designed mainly for robotic applications. This hydraulic cylinder will be used as the main actuator for the hydraulic humanoid robot HYDROïD. For implementation, the knee joint is taken as an example in order to execute the necessary steps to build the actuator from carbon fiber composite material. An optimization process is used to minimize the total weight of the actuator and satisfy its constraints. Meanwhile, the mechanical design with the integrated sensors is shown. In addition, results are discussed on the spot of the weight minimization and actuator performance. Finally, experimental testing is carried out to monitor the pressure and the position readings of the hydraulic cylinder.

This paper deals with a research work that aims to develop a new three degrees-of-freedom (DoF) hybrid mechanism for humanoid robotics application. The proposed hybrid mechanism can be used as a solution not only for several modules in humanoid robots but also for other legged robots such as quadrupeds and hexapods. Hip and shoulder mechanisms are taken as examples in this paper; torso and spine mechanisms, too, can be based on the proposed solutions. In this paper, a detailed analysis of the required performances of the hip and shoulder mechanisms is first carried out. Then, using a kinematic synthesis, a novel solution for the hip mechanism is proposed based on one rotary and two linear actuators. Improving this solution allows us to fulfill the requirements induced by the large motion ranges of the shoulder module, leading to a new management of the linear actuators contributions in the motion/force achievement process. Kinematic and geometrical models of a generic hybrid mechanism are achieved and used to get the optimized solutions of both hybrid mechanisms addressed in this paper.