Multi-actuator Switch-mode Hydraulic System a Major Qualifying Project Report
Current hydraulic systems involving multiple actuators and a single hydraulic power supply generally have poor efficiency. Using throttling valves to control multiple actuators requires meeting the highest pressure requirement and the total flow of all of actuators. When there is a large difference in the pressure requirement of the actuators, fluid throttling results in significant energy losses. The purpose of this project is to implement switch-mode control in a multi-actuator circuit and demonstrate the improvement in efficiency over a traditional hydraulic system with throttling valve control. To accomplish this task a hydraulic crane arm powered by two actuators was designed and constructed. One actuator provides a pivoting motion utilizing low pressure and high flow, while the other provides a lifting motion utilizing high pressure and low flow. Using a simple feedback control loop, the crane arm lifts, rotates, and lower a load. After designing and testing the hydraulic crane, the team concluded that high-speed switch technology with multiple actuators is feasible. This new technology, once implemented on a larger scale in realistic applications, will reduce losses in hydraulic systems that depend on multiple actuators to function.
Design of a High-Speed On-Off Valve
On-off control of hydraulic circuits enables significant improvements in efficiency compared with throttling valve control. A key enabling technology to on-off control is an efficient high-speed on-off valve. This paper documents the design of an on-off hydraulic valve that minimizes input power requirements and increases operating frequency over existing technology by utilizing a continuously rotating valve design. This is accomplished through use of spinning port discs, which divides the flow into pulses, with the relative phase between these discs determining the pulse duration. A mathematical model for determining system efficiency is developed with a focus on the throttling, leakage, compressibility, and viscous friction power losses of the valve. Parameters affecting these losses were optimized to produce the most efficient design under the chosen disc-style architecture. Using these optimum parameter values, a first generation prototype valve was developed and experimental data collected. The experimental valve matched predicted output pressure and flows well, but suffered from larger than expected torque requirements and leakage. In addition, due to motor limitations, the valve was only able to achieve a 64Hz switching frequency versus the designed 100Hz frequency. Future research will focus on improving the prototype valve and improving the analytical model based on the experimental results.Copyright © 2009 by ASME
A new power measuring circuit using a bridge-connected magnetic circuit and another magnetic core
The authors describe the operating characteristics of an oscillating circuit using a bridge-connected magnetic circuit and another magnetic core. A square-shape output voltage is obtained in the oscillating circuit. The pulsewidth in positive and negative half cycles of output voltage changes with the current of the U-form core windings and with the signal voltage applied to the exciting windings. The mean value of the output voltage varies in proportion to the product of the current and the signal voltage. Utilizing this feature, an application of the oscillating circuit to a novel power measuring circuit of simple construction is presented. >