Comparative Analysis of Energy Efficiency: Knuckle Boom Crane Driven by Motor-Controlled Cylinders Versus Valve-Controlled Cylinders

When a hydraulic differential cylinder is directly connected to fixed-displacement hydraulic pumps driven by independent electric servo motors, the cylinder motion is manipulated by controlling the velocities of the electric servo motors. This configuration is called a motor-controlled hydraulic cylinder (MCC) in this study. In contrast to valve-controlled hydraulic cylinders (VCCs), MCCs theoretically offer enhanced energy efficiency due to the absence of valve throttling. However, the energy efficiency performance of MCCs in multi-cylinder applications still needs to be explored in the existing research. This paper seeks to bridge this gap by comparing a knuckle boom crane driven by proposed two-motor-two-pump MCCs with a passive load-holding function and VCCs on the crane in energy efficiency. To achieve this, non-linear dynamic models of a knuckle boom crane driven by two-motor-two-pump MCCs and the original VCCs on the crane are created in MATLAB/Simulink. A realistic operation path for lifting a payload is designed, and three load cases are tested. Simulation results demonstrate better performance of the proposed MCCs in energy efficiency than VCCs. In conclusion, this study showcases the viability of the proposed MCCs for practical applications, highlighting their enhanced energy efficiency compared to traditional VCCs.