A novel linear pneumatic actuator with tunable-compliance constraint

This paper introduces a novel pneumatic linear actuator that features variable stiffness/compliance along constrained directions. Specifically, the proposed system is a pneumatically driven linear actuator that is implemented according to a common piston-cylinder architecture. The system employs two long-stroke rolling diaphragms that assume both the functions of sealing the pressurized cylinder chamber and constraining the motion of piston. The control of stiffness along non-actuated directions is achieved through the regulations of the pre-pressurization of an air chamber that is enclosed by the two rolling diaphragms. A theoretical model able to explain and describe the variation stiffness for the proposed architecture is presented. A preliminary prototype of the system is designed and built, and a set of experiments are implemented to demonstrate the concept, to verify the modelling approach and to validate the theoretical analysis.