A Bypass Flow Control System to Improve the Transient Response of an Energy Efficient Hydraulic Pump-Motor System

In this paper a hydraulic circuit that demonstrates both high dynamic performance and high energy efficiency is presented. The system uses a variable displacement pump which represents an energy efficient choice but can display poor transient response characteristics due to slow response of the pump. In this study, a DC motor is used to control the pump swashplate directly to increase the dynamic response of the pump. The problem with this arrangement is that the overshoot of the hydraulic motor is substantially increased. To reduce the effect of the overshoot, a bypass flow control system is utilized to bypass part of the pump flow during the transient. This allows the system to converge to steady state conditions more rapidly while maintaining an energy efficient system.