Construction machine and hydraulic system thereof

A construction machine comprising:

• a first implement function operable by a first actuator;
• a second implement function operable by a second actuator;
• and
• a hydraulic system for controlling the first and second actuators in response to operator controls, the hydraulic system comprising:
• a four-quadrant open-circuit pump;
• a solenoid configured to control a swivel plate of the pump;
• and
• a controller configured to provide displacement control of the pump by direct current command to the solenoid;
• wherein the first and second actuators are both configured for actuation by the pump in parallel first and second circuits, and
• wherein load sensing for the first actuator is provided exclusively by the controller's displacement control of the pump, and
• wherein load sensing for the second actuator is provided by a pressure compensator to adjustably throttle flow in relation to a sensed load pressure.

A method of controlling a construction machine, the method comprising:

• driving a variable displacement pump with a prime mover to charge a pressure line of a hydraulic system having a first control valve with an extend position configured to selectively connect a first actuator for a first implement function to the pressure line and a second control valve with an extend position configured to selectively connect a second actuator for a second implement function to the pressure line;
• setting the second control valve into the extend position, and providing load sensing with a pressure compensator to throttle flow through the second control valve while extending the second actuator;
• setting the first control valve into the extend position, and providing load sensing solely by control of the variable displacement pump without any pressure-compensating throttling of flow through the first control valve, while extending the first actuator;
• and
• maintaining the first control valve in the extend position in which energy is recovered by the prime mover through the pump while retracting the first actuator.