Modeling and control of a hydraulic system with multi actuators
Abstract
Though displacement controlled hydraulic systems have proven to be an efficient way to minimize the valve metering losses to valve controlled actuators, the pump requirement for each actuator makes the multi actuators system more expensive and need more space than the other. Other hydraulic systems with individual metering valves and low side pressure maintain line enable the regeneration mode, but only under assistive loads. Topography with Integrated Energy Recovery (TIER) system is used to control the swing, boom, stick and bucket motion of an excavator. The TIER system often has several operating modes available for completing tasks, and some modes involve multiple actuators supplied by a single pump. The objective of this work is to evaluate and characterize a new control mode taking advantage of displacement control and individual metering control, where two actuators are supplied by a single pump. This operating mode is within the capabilities of the TIER system. It can also be generalized for other multi-actuator systems served by one pump, including more than two actuators. In support of the control mode development, a hydraulic system simulation model was developed to predict and characterize the performance of the system. The system schematic is a subset of TIER, with one pump, two actuators and eight high speed electrically-actuated proportional valves. A two-level controller including supervisory mode selection and local controller was developed and applied to the hydraulic system model. The hybrid displacement control mode has been simulated using flow control and pressure control algorithms to test the stability of the controller. A loading cycle derived using experimental data from a 5-ton compact excavator was used as input to the model. From the simulation study with the specific loading cycle, the proposed control mode can work in both assistive and resistive load conditions. The hybrid displacement control reduced fuel consumption for the loading cycle by 14.8% compared to the same loading cycle with individual metering control.
Degree
M.S.E.
Advisors
Meckl, Purdue University.
Subject Area
Mechanical engineering
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