Method and Hydraulic Control System Having Swing Motor Energy Recovery

A control circuit comprising:

• a swing motor, the swing motor having a first chamber and a second chamber, the swing motor moving in a first direction when fluid flows into the swing motor through the first chamber, the swing motor moving in a second direction when fluid flows into the swing motor through the second chamber;
• first and second conduits, the first conduit connected to the first chamber of the swing motor, the second conduit connected to the second chamber of the swing motor;
• a pump adapted to selectively provide fluid to the swing motor through the first and second conduits;
• an accumulator;
• at least one electrically-operated selector valve, the first selector valve being hydraulically connected to the first and second chambers and to the accumulator and being movable between a closed position wherein the accumulator is hydraulically blocked from the swing motor, a first open position wherein a flow path between the first chamber of the swing motor and the accumulator is defined, and a second open position wherein a flow path between the second chamber of the swing motor and the accumulator is defined;
• at least one pressure sensor disposed to detect a pressure differential between the accumulator and at least one of the first chamber and the second chamber;
• at least one swing control valve, the swing control valve hydraulically connected to the pump and to the first and second chamber conduits, the swing control valve movable between a first open position wherein a flow path between the pump and the first chamber conduit is defined, a second open position wherein a flow path between the pump and the second chamber conduit is defined, and at least one closed position wherein the pump and the swing motor are hydraulically blocked from each other;
• and
• a controller in communication with the swing control valve and the selector valve, the controller being configured to:
• receive input indicative of a pressure differential between the accumulator and at least one of the first chamber and the second chamber;
• receive a swing motor command input;
• calculate a target swing motor flow based on the swing motor command input;
• and
• modulate operation of the swing control valve and the selector valve to regulate a swing speed.