Abstract: A ride control system includes four independent metering valves (IMVs) that are independently and selectively controlled by a controller for attenuating oscillations in a hydraulic actuator of a machine. The controller is configured to open at least one of the IMVs for supplying pressurized fluid from a tank to a head end chamber of the hydraulic actuator when a pressure of the head end chamber drops to a value less than an initially registered pressure. Additionally, when the displacement of the piston block is positive and the pressure in the head end chamber falls to a value less than the pressure of fluid in a rod end chamber of the hydraulic actuator, the controller may also open another one of the IMVs by which fluid from the rod end chamber could be supplied to the head end chamber for supplementing pump flow and attenuating oscillations in the hydraulic actuator.

Abstract: A port plate for a swashplate type axial piston pump is described herein. The port plate includes an inlet port, a discharge port, and a first metering notch in fluidic communication via a first passage with a metering notch area adjustment valve configured to adjust the effective area of the metering notch. The first metering notch is disposed at a leading edge of one of the inlet port or the discharge port.

Abstract: An energy recovery system includes cylinders that articulate a hydraulic tool in a pump mode to provide potential energy and in a motor mode to recover the potential energy. The energy recovery system includes a tank that stores a hydraulic fluid for the cylinders and an open circuit variable displacement pump that circulates the hydraulic fluid in the pump mode from the tank to the cylinders and in the motor mode from the cylinders to the tank. The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode and in the negative position the hydraulic fluid circulates in the motor mode. The open circuit variable displacement pump includes an actuator that articulates the swashplate and a bias system that maintains the swashplate in a positive position when the hydraulic fluid is not in circulation.

Abstract: An energy recovery system includes cylinders that articulate a hydraulic tool in a pump mode to provide potential energy and in a motor mode to recover the potential energy. The energy recovery system includes a tank that stores a hydraulic fluid for the cylinders and an open circuit variable displacement pump that circulates the hydraulic fluid in the pump mode from the tank to the cylinders and in the motor mode from the cylinders to the tank. The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode and in the negative position the hydraulic fluid circulates in the motor mode. The open circuit variable displacement pump includes an actuator that articulates the swashplate and a bias system that maintains the swashplate in a positive position when the hydraulic fluid is not in circulation.

Abstract: A ride control system includes four independent metering valves (IMVs) that are independently and selectively controlled by a controller for attenuating oscillations in a hydraulic actuator of a machine. The controller is configured to open at least one of the IMVs for supplying pressurized fluid from a tank to a head end chamber of the hydraulic actuator when a pressure of the head end chamber drops to a value less than an initially registered pressure. Additionally, when the displacement of the piston block is positive and the pressure in the head end chamber falls to a value less than the pressure of fluid in a rod end chamber of the hydraulic actuator, the controller may also open another one of the IMVs by which fluid from the rod end chamber could be supplied to the head end chamber for supplementing pump flow and attenuating oscillations in the hydraulic actuator.

Abstract: A system for determining an estimated displacement of a variable displacement hydraulic pump includes a control cylinder associated with the swash plate of the variable displacement hydraulic pump to control the angle of inclination of the swash plate and a valve that controls the flow of hydraulic fluid to the control cylinder and has a position that defines an effective area of an opening of the valve. A pressure sensor generates pressure signals indicative of an output pressure from the variable displacement hydraulic pump. A controller is configured to receive pressure signals from the pressure sensor and determine an estimated displacement of the variable displacement hydraulic pump based upon the pressure signals from the pressure sensor and the position of the valve.

Abstract: A sensor is disclosed for detecting aeration of a fluid passing through a conduit. The sensor may have a first electrode with a first end mountable in a wall of the conduit, and a second end configured to be exposed to the fluid passing through the conduit. The sensor may also have a second electrode with a first end mountable in the wall of the conduit adjacent the first electrode, and a second end configured to be exposed to the fluid passing through the conduit. The sensor may further have a dielectric insulator disposed between the first ends of the first and second electrodes.

Abstract: A port plate for a swashplate type axial piston pump is described herein. The port plate includes an inlet port, a discharge port, and a first metering notch in fluidic communication via a first passage with a metering notch area adjustment valve configured to adjust the effective area of the metering notch. The first metering notch is disposed at a leading edge of one of the inlet port or the discharge port.

Abstract: A system for determining an estimated output from a variable displacement hydraulic pump includes a prime mover, a torque sensor, a pressure sensor, and a displacement sensor. A controller is configured to determine the output torque from the prime mover, determine an input torque to the variable displacement hydraulic pump based upon the output torque, determine an output from one of the pressure sensor and the displacement sensor based upon the signals. The controller is further configured to determine a failure of another of the pressure sensor and the displacement sensor and determine an estimated output from the another of the pressure sensor and the displacement sensor based upon the input torque to the variable displacement hydraulic pump and the output from the one of the pressure sensor and the displacement sensor.

Abstract: A system for determining an estimated displacement of a variable displacement hydraulic pump includes a control cylinder associated with the swash plate of the variable displacement hydraulic pump to control the angle of inclination of the swash plate and a valve that controls the flow of hydraulic fluid to the control cylinder and has a position that defines an effective area of an opening of the valve. A pressure sensor generates pressure signals indicative of an output pressure from the variable displacement hydraulic pump. A controller is configured to receive pressure signals from the pressure sensor and determine an estimated displacement of the variable displacement hydraulic pump based upon the pressure signals from the pressure sensor and the position of the valve.

Abstract: A system for determining an estimated output from a variable displacement hydraulic pump includes a prime mover, and torque, pressure, and displacement sensors. A controller determines the output torque from the prime mover, determines an input torque to the variable displacement hydraulic pump based upon the output torque, determines an output from one of the pressure sensor and the displacement sensor, and determines an inertia torque loss based upon the angular acceleration of the prime mover. The controller further determines a failure of another of the pressure sensor and the displacement sensor and determines an estimated output from the another of the pressure sensor and the displacement sensor based upon the input torque to the variable displacement hydraulic pump, the output from the one of the pressure sensor and the displacement sensor, and the inertia torque loss.

Abstract: A system for determining an estimated output from a variable displacement hydraulic pump includes a prime mover, a torque sensor, a pressure sensor, and a displacement sensor. A controller is configured to determine the output torque from the prime mover, determine an input torque to the variable displacement hydraulic pump based upon the output torque, determine an output from one of the pressure sensor and the displacement sensor based upon the signals. The controller is further configured to determine a failure of another of the pressure sensor and the displacement sensor and determine an estimated output from the another of the pressure sensor and the displacement sensor based upon the input torque to the variable displacement hydraulic pump and the output from the one of the pressure sensor and the displacement sensor.

Abstract: A system for determining an estimated output from a variable displacement hydraulic pump includes a prime mover, and torque, pressure, and displacement sensors. A controller determines the output torque from the prime mover, determines an input torque to the variable displacement hydraulic pump based upon the output torque, determines an output from one of the pressure sensor and the displacement sensor, and determines an inertia torque loss based upon the angular acceleration of the prime mover. The controller further determines a failure of another of the pressure sensor and the displacement sensor and determines an estimated output from the another of the pressure sensor and the displacement sensor based upon the input torque to the variable displacement hydraulic pump, the output from the one of the pressure sensor and the displacement sensor, and the inertia torque loss.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may include a pump configured to pressurize fluid, a displacement control valve configured to affect displacement of the pump, and a solenoid configured to bias the displacement control valve to a zero position. The hydraulic control system may also include a controller in communication with the solenoid. The controller may be configured to estimate a bias current that biases the displacement control valve to the zero position, and to control the displacement control valve based on the bias current. The controller also be further configured to monitor a pump parameter of the pump, and to determine a control error associated with the pump parameter. The controller may further be configured to selectively adjust the bias current based on the control error.

Abstract: A method and apparatus for controlling discharge pressure and pump displacement of a plurality of variable displacement hydraulic pumps having connected discharge ports is provided. Each pump includes a swashplate and a control valve for controlling an angle of inclination of the swashplate. A desired first pump displacement control law is determined for a first pump and determined a desired second pump discharge pressure control law for a second pump. The first control law is used to determine a first intermediate control variable. The second control law is used to determine a second intermediate control variable. The control of the first and second pumps are combined using the first and second intermediate control variables. A desired first control valve setting for the control valve of the first pump is determined using the combined first and second intermediate control variables and the first control law.

Abstract: Methods, apparatuses, and computer program products for controlling the torque load of multiple variable displacement hydraulic pumps are described herein. A pump displacement limit for each variable displacement hydraulic pump is determined using a nonlinear control law to limit the total pump torque load of the variable displacement hydraulic pumps on the engine. The value of the actual pump displacement of each variable displacement hydraulic pump is controlled based upon the respective determined pump displacement limit.

Abstract: A pump is disclosed. The pump may have a housing, a body rotatably disposed within the housing and at least partially defining a plurality of barrels, a plurality of plungers associated with the plurality of barrels, and a swashplate tiltable by a swivel torque to vary a displacement of the plurality of plungers relative to the plurality of barrels. The pump may also have a port plate with an inlet port, a discharge port, and a protrusion. The port plate may be configured to engage an end of the rotatable body. The pump may further have at least one piston disposed within the housing and configured to selectively engage the protrusion of the port plate to rotate the port plate and adjust the swivel torque.

Abstract: Swashplate angle sensing arrangement for a variable displacement pump a nonrotating swashplate and a rotating pump barrel includes a dielectric sensor in a swashplate angle sensing arrangement. The arrangement includes a sensing probe coupled to the casing, a sensor target coupled to the swashplate, and a controller configured to direct an alternating current through the sensing probe to establish an impedance between the probe and the target, and to determine voltage across the probe. The controller is further adapted to determine the angle of the swashplate relative to the casing based on the determined voltage.

Abstract: An electro-hydraulic control system manages speed of a hydraulic fan by using a solenoid to bias a three position pool of a control valve coupled to a hydraulic pump driving the fan. In a first position, the spool releases pressure on a de-stroke actuator of the pump and allows an on-stroke actuator to increase output pressure corresponding to a speed of an engine driving the pump. In a second position, the spool isolates the de-stroke actuator and fixes the pressure output of the pump. In a third position, the spool couples the de-stroke actuator to the pump output and causes a reduction in the pressure output of the pump. The solenoid coupled to the spool sets the output pressure at which the spool is in the second position.

Abstract: An electro-hydraulic control system for pump control is disclosed. The hydraulic actuator is configured to control the inclination of a swashplate. The position of the hydraulic actuator is controlled by controlling the flow of pressurized fluid into and out of two pressure chambers, one on either side of the actuator. A fluid passageway is provided that selectively connects the passageway to tank. The passageway has an orifice for each pressure chamber, and the actuator is configured to selectively block all or a portion of one or more of the orifices, depending on the position of the actuator. The components of the control system are configured such that the actuator will return to a neutral or near-neutral position upon loss of electric power.