Hydraulic control system having swing motor energy recovery

A hydraulic system, comprising:

• a tank;
• a pump configured to draw fluid from the tank and pressurize the fluid;
• a swing motor, having a first chamber and a second chamber, wherein the swing motor is driven by a flow of pressurized fluid from the pump;
• a means for sensing pressure of each of the first and second chambers of the swing motor;
• an accumulator configured to selectively receive pressurized fluid discharged from the swing motor and selectively supply pressurized fluid to the swing motor;
• a means for sensing an accumulator pressure;
• a first valve coupled between the accumulator and the first and second chambers of the swing motor, and a second valve coupled between the accumulator and the first valve;
• and
• wherein at least one of the first and second valves is a three-way valve movable between a first position, a second position, and a third position, at the first position flow of the fluid between the swing motor and the accumulator is inhibited, at the second position one of the first and second chambers of the swing motor is fluidly coupled to the accumulator and the other of the first and second chambers of the swing motor is fluidly coupled to the second valve, at the third position the other of the first and second chambers of the swing motor is fluidly coupled to the accumulator and the one of the first and second chambers of the swing motor is fluidly coupled to the second valve;
• and
• a controller in electrical communication with the first valve and the second valve and the means for sensing pressure of the chambers and the means for sensing accumulator pressure;
• the controller configured to command movement of at least one of the first valve and the second valve based on the pressure of the chambers and the accumulator.

A hydraulic system, comprising:

• a tank;
• a pump configured to draw fluid from the tank and pressurize the fluid;
• a swing motor, having a first chamber and a second chamber, wherein the swing motor is driven by a flow of pressurized fluid from the pump;
• port pressure sensors associated with each of the first and second chambers of the swing motor;
• an accumulator configured to selectively receive pressurized fluid discharged from the swing motor and selectively supply pressurized fluid to the swing motor;
• an accumulator pressure sensor associated with the accumulator;
• a first check valve coupled between the accumulator and the first chamber of the swing motor, and a second check valve coupled between the accumulator and the second chamber of the swing motor;
• a first valve coupled between the accumulator and the first and second chambers of the swing motor, and a second valve coupled between the accumulator and the first and second check valves;
• and
• wherein the first valve is a three-way valve movable between a first position, a second position, and a third position, at the first position flow of the fluid between the swing motor and the accumulator is inhibited, at the second position one of the first and second chambers of the swing motor is fluidly coupled to the accumulator and the other of the first and second chambers of the swing motor is blocked from fluid communication with the accumulator, at the third position the other of the first and second chambers of the swing motor is fluidly coupled to the accumulator and the one of the first and second chambers of the swing motor is blocked from fluid communication with the accumulator;
• wherein the second valve is a two-way valve movable between a first position and a second position, at the first position flow of the fluid between the swing motor and the accumulator is inhibited, at the second position a higher pressure one of the first and second chambers of the swing motor is fluidly coupled to the accumulator;
• and
• a controller in electrical communication with the first valve and the second valve and the port and accumulator pressure sensors;
• the controller configured to command movement of at least one of the first valve and the second valve based on the pressure of the chambers and the accumulator.