PhD Thesis Slides

My Ph.D. thesis titled “Design of Adjustable Mechanisms for Variable Displacement Linkage Pumps and Motors” makes the following contributions to the fields of fluid power and mechanism design: 

1. A kinematic formulation for adjustable cam-linkage mechanisms for variable displacement linkage pumps/motors, allowing for modifications in the Top Dead Center (TDC) and Bottom Dead Center (BDC) positions. This formulation enables shifts in the TDC and BDC positions along the piston axis of slide, allowing them to be advanced or delayed during  the cycle.

2. A comparison between the forward and inverse cam design methods applied to the design of cam-linkage mechanisms for function generation is conducted. This comparison is demonstrated with a case study of a hydraulic motor, which includes the corresponding  procedures for cam generation, as well as models for cam-linkage kinematics and cylinder pressure dynamics. The two methods are compared based on ease of implementation and a thorough evaluation of both kinematic and dynamic results.

3. Dynamic modeling, experimental validation, and analysis of the adjustable cam-linkage mechanism for a low-speed high-torque hydraulic motor. The mathematical model incorporates the kinematics and dynamics of the adjustable mechanism, coupled with cylinder pressure dynamics. The analysis explores the impact of motor speeds, operating pressures, and various displacement adjustment times on actuation forces.

4. The use of model-driven design for the design and development of variable displacement linkage motors including adjustment dynamics. The synthesis of the main linkage mechanism and the adjustable linkage mechanism are performed simultaneously using multi-objective optimization techniques. The proposed approach enables the automatic sizing of mechanism components to withstand working loads. Moreover, optimization penalties ensure that candidate motors exhibit solely unidirectional adjustment forces under certain operating conditions. The optimal motor selected has a displacement of 300cc/rev, a weighted mechanical efficiency of 95.7%, a diameter of 296 mm, and a peak actuation force of 4.95 kN for a displacement adjustment time of 30 milliseconds.