KINEMATICS OF AN ADJUSTABLE CAM-LINKAGE MECHANISM FOR A VARIABLE DISPLACEMENT HYDRAULIC MOTOR

Displacement adjustment is a key method for controlling hydraulic circuits in practical applications that use pumps and motors. However, the currently available low-speed high-torque (LSHT) motor designs do not provide continuous variable displacement capability. For this reason, this research work introduces a novel kinematic formulation of an adjustable cam-linkage mechanism, which is used to design a variable displacement linkage motor (VDLM). This paper presents a general description of the cam-linkage mechanism formulated with a system of kinematic equations. Next, the process to calculate the linkage limits of motion for different displacements is described, followed by the procedure to adjust the linkage mechanism. Subsequently, the synthesis process of the cam-linkage mechanism applied in a variable displacement hydraulic motor is presented. A physical prototype is designed and built using the selected mechanism and is used for validation purposes. Finally, the paper discusses the model development results, the experimental validation of the linkage mechanism, and draws conclusions. The experimental results show that the linkage kinematics model is accurate, with only minor differences found in experimental piston trajectories which are thoroughly analyzed. The models and concepts presented here have the potential to be used for the design and synthesis of adjustable cam-linkage mechanisms with various topologies.