Dynamic performance of auxiliary hydraulic power unit based electro-hydraulic variable speed drive system

Abstract

Inability of dynamic performances, especially the acceleration response, strongly inhibits the application of electro-hydraulic variable speed drive, even though its intrinsic energy-saving potential. In contrast to variable speed drive, the valve-controlled actuator system shows the capacity of fast response and accurate control precision, but it consumes more energy. The controllable auxiliary power unit based electro-hydraulic variable speed drive system is probably a solution to enhance dynamic performance of variable speed drive on the basis of energy-saving. Except for the principal variable speed power source, there is an auxiliary power source—auxiliary power unit, which is actually a semi-active hydraulic accumulator unit. The auxiliary power unit can detect the relation between the supplied power by power source and the demanded power by actuator, and then release or absorb hydraulic power to improve actuator dynamic response. The dynamic performance of auxiliary power unit based variable speed drive system was investigated experimentally. Firstly, the set-up of proposed drive system was introduced. Dedicated to the complicated characteristics of multi-input-multi-output and strongly nonlinearity, the mathematical model was deduced, and a hierarchical control strategy was illustrated. The experimental results under two typical variable-load conditions were discussed. Furthermore, the comparisons were explained with the other three drive systems, which were valve-controlled motor drive, conventional variable speed drive, and pump-valve compound drive. Based on the experimental results, it is concluded that the auxiliary power unit based variable speed drive demonstrates an excellent dynamic performance, which can significantly improve the actuator response and control precision, as well as obtain a good energy-saving behavior.