| 摘要 |
A system for controlling an operation of a cylinder comprises: a hoist cylinder displacing a member to be driven such as vessel of a dump truck in a vertical direction; a directional control valve for switching the cylinder so as to take a first position performing an expansion motion of the hoist cylinder and a second position performing a contraction motion thereof; an electromagnetic proportional pressure control valve for throttling a meter-out area at a time when the directional control valve takes the second position; a potentiometer for outputting a signal in response to the vertical displacement of the vessel; and a controller. When the controller detects that the vessel is just before the descending end position, the controller controls to reduce the output pressure as optimum current from the electromagnetic proportional pressure control valve to thereby make slow the descending speed by throttling the meter-out area of a hoist valve of the hoist cylinder. Thereafter, the vessel descending speed is detected by the controller, and in the case where this descending speed differs from the set descending speed, the current from the electromagnetic proportional pressure control valve is amended to thereby amend the descending speed through the control of the meter-out area of the hoist valve.
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