Simulation study of implementation of Direct Driven Hydraulics for swing motion of an excavator
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2022-06-13
Department
Major/Subject
Mcode
Degree programme
Master's Programme in Mechanical Engineering (MEC)
Language
en
Pages
66 + 6
Series
Abstract
Diesel motor-powered construction machines, like excavators, cause significant CO2 emissions. This is firstly because construction machinery has traditionally been driven with fossil fuels and secondly because of the low energy efficiency of the powertrain. It is traditionally operated mainly through the hydraulic system which depends on a valve-control. Studies have found that valve losses are one of the major sources of losses in hydraulic system. Displacement-controlled systems, where the actuator motion is controlled directly by controlling the rotational speed of the pump with a servo motor, also known as Direct Driven Hydraulics (DDH), have been an alternative solution to mitigate the loss. Several studies have been undertaken to study the DDH system when producing boom-arm-bucket linkage motion of excavators. This thesis was aimed at expanding the research to the machine’s swing motion application. The purpose was to design a hydraulic circuit for the application, develop a simulation model to test the system performance, and determine the size of the system components. The study focuses on a modified JCB micro excavator that is on the verge of being converted to a DDH-actuated system with an electric power supply. A DDH circuit was designed for the application and its multibody simulation model was developed in Matlab/Simscape environment. The multibody model gives visual feedback of the system performance. The simulation study showed that 6.5 cm3/rev sized pump, 200 cm3/rev hydraulic motor, and an electric synchronous servo motor-rated for 8.2 Nm of stand-still torque were required for the machine to be able to operate at its highest and lowest demand conditions. The test revealed that, for 90° swing motion, the machine consumes 1.73 to 2.42 kJ and 2.54 to 3.2 kJ energy per cycle on flat and slope surfaces respectively. This corresponds to the energy consumption of 0.11 to 0.15 kWh/h on flat surface and 0.16 to 0.2 kWh/h on slope surface. Because this is the first study of its kind on the application, the findings will serve as a benchmark for future research. The produced model can be used to continue the upgrade of the excavator with DDH actuators and to create a prototype for bench tests.Description
Supervisor
Pietola, MattiThesis advisor
Kajaste, JyrkiCalonius, Olof
Keywords
Direct Driven Hydraulics (DDH), swing motion, excavator, pump-controlled actuator, energy consumption