Velocity control of unbalanced hydraulic actuator subjected to over-center load conditions

摘要

An electro-hydraulic actuation system (901) includes an unbalanced hydraulic actuator (902) capable of motion in retraction and extension directions during movement of a load (904). A pump (204) provides a flow of fluid to the actuator. A displacement of the pump controls a velocity of the actuator during motion in the retraction and extension directions. An electric motor (202) drives the pump. Speed and direction of the electric motor affects the displacement of the pump. A controller (802) controls the speed and direction of the electric motor. A feedback device (228,248) is operable for sensing a system condition and for providing a feedback signal indicative of the sensed system condition to the controller. The controller is responsive to the feedback signal for determining an occurrence of an over-center load condition and for modifying the speed of the electric motor in response to the occurrence in an attempt to maintain the velocity of the actuator.

主权项

1. An electro-hydraulic actuation system comprising:
an unbalanced hydraulic actuator capable of motion in retraction and extension directions during movement of a load; a pump for providing a flow of fluid to the actuator, a fluid volume output of the pump controlling a velocity of the actuator during motion in the retraction and extension directions; an electric motor for driving the pump, speed and direction of the electric motor affecting the fluid volume output of the pump; a controller for controlling the speed and direction of the electric motor; and a feedback device operable for sensing a system condition and for providing a feedback signal indicative of the sensed system condition to the controller, the controller being responsive to the feedback signal for determining an occurrence of an over-center load condition and for modifying the speed of the electric motor in response to the occurrence in an attempt to maintain the velocity of the actuator; wherein the feedback device is adapted to sense current and direction of rotation of the electric motor; and wherein the controller determines the occurrence of an over-center load condition when a sign of the current changes while a direction of rotation of the electric motor remains unchanged.