New approach for hydraulic force control based on hydraulic compliance

This paper presents an approach of force control with hydraulic cylinders based on the modification of hydraulic compliance. The force control is one of the most studied topics in hydraulic control systems and previous researches showed that the inclusion of flexible components, such as a spring, between the actuator and the external environment results very useful to obtain a stable force control. Demonstrate the possibility of removing the spring and get a similar effect by increasing the hydraulic compliance through the use of high volumetric expansion hoses is the main objective of this paper. The use of only hydraulic components in the system ensures saving physical space in axial direction, allowing a direct contact between the actuator and the environment. A variation in the hydraulic stiffness value is mandatory to modify the compliance of the system. The sizing and selection of the hydraulic hoses depends of this controlled variation. In order to demonstrate the applicability of this approach, this study shows force responses based on simulations using a classical PID controller. Additionally, performance indices show the advantage of using hydraulic compliant elements to improve the force control in hydraulic actuation systems.