Dynamic Analysis of an Adjustable Linkage Mechanism for a Low-Speed, High-Torque Hydraulic Motor

Adjustment of hydraulic motor displacement plays a critical role in regulating hydraulic circuits across a wide range of applications. However, the absence of commercially available continuously variable low-speed high-torque (LSHT) motor architectures poses a challenge. To evaluate a potential solution, this paper presents the dynamic analysis of an adjustable low-speed high-torque motor, the variable displacement linkage motor, with an emphasis on understanding the dynamics at different operating conditions. The hydraulic motor studied consists of five phase-shifted cam-linkage mechanisms that can be dynamically adjusted to change the displacement within certain limits. The primary contribution of this paper is the mathematical modelling of the kinematics and dynamics of the adjustable linkage mechanism to explore the relative impact of the inertial, friction, and pressure-based forces. The results of the dynamic analysis reveal that inertial forces are higher when decreasing the displacement vs. increasing the displacement. Furthermore, at an operating pressure of ∆p = 22 MPa, there is a notable 47.1% increase in actuation force when the settling time is reduced from 150 to 25 ms. Additional analyses cover the influence of inertial forces on actuator force at various operating pressures, and the adjustment actuator flow rate requirements associated with different adjustment times.