HYDRAULIC DRIVE SYSTEM AND METHOD OF OPERATING A HYDRAULIC DRIVE SYSTEM

摘要

A hydraulic drive system (100) comprises a hydraulic actuator (110) comprising a piston (118) reciprocable between two cylinder heads (114, 116) for actuating a machine. A flow switching device (130) reverses the direction of hydraulic fluid flow to and from chambers (120, 122) on opposite sides of the piston (118). The piston (118) stops at the end of each piston stroke when a shuttle valve (124) associated with the piston (118) opens to allow hydraulic fluid to flow between the chambers (120, 122) cancelling the differential pressure that acts on the piston (118) to cause reciprocal movement. A controller (170) is programmed to determine when the piston (118) reaches the end of each stroke based upon at least one of hydraulic pump (140) speed, hydraulic fluid pressure, or elapsed time, with each of these measured during each stroke. The controller (170) then sends an electronic signal to command the flow switching device (130) to reverse the direction of hydraulic fluid flow.