HYDRAULIC DRIVE SYSTEM AND METHOD OF OPERATING A HYDRAULIC DRIVE SYSTEM

摘要

A hydraulic drive system comprises a hydraulic actuator comprising a pist on that is reciprocable between two cylinder heads for actuating a machine. A flow switching device reverses the direction of hydraulic fluid flow to and from chambers an opposite sides of the piston. The piston stops at the end o f each piston stroke when a shuttle valve associated with the piston opens to allow hydraulic fluid to flow between the piston chambers cancelling the differential pressure that acts on the piston to cause reciprocal movement. In preferred embodiments, a controller is programmed to determine when the piston has reached the end of each piston stroke based upon at least one of hydraulic pump speed, hydraulic fluid pressure, or elapsed time, with each o f these measured during each piston stroke. When the controller determines that the piston has reached the end of a piston stroke, it sends an electron ic signal to command the flow switching device to reverse the direction of hydraulic fluid flow.