Experimental Estimation of Friction and Friction Coefficient of a Lightweight Hydraulic Cylinder Intended for Robotics Applications

Abstract

Recently, hydraulic actuator has been used in several engineering applications such as: aeronautics, construction and robotics. This is due to the need of high torque and power density in such engineering applications. Despite these advantages, hydraulic actuators are fabricated from metallic materials, which provoke their heavy weight, which necessitate the development of a lightweight hydraulic actuator, fabricated of composite materials. Using composite materials in hydraulic cylinders, it is important to study the friction force characteristics and to estimate the friction coefficient between composites and O-rings, which is presented in this paper. This paper deals with the estimation of Coulomb friction and friction coefficient in the lightweight hydraulic cylinder fabricated mainly of composite materials. The actuator is presented by its dynamic equation of motion, where each term is discussed including the stiffness coefficient, the viscous damping coefficient, the kinematics and the pressure parameters. Meanwhile, these coefficients and parameters are obtained according to data recorded from conducted experiments. As a result, the new methodology which uses the experimental measurements combined the dynamic model has succeeded to evaluate the friction inside the hydraulic cylinder which has been estimated and found to be around 166[Formula: see text]N, while the corresponding coefficient of friction is computed (about 0.61 as average value). These results will be important for further optimization of the material choice and actuator design, which will help in the amelioration of the hydraulic cylinder.