Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A control valve includes a main poppet that moves in response to pressure in a primary control chamber and thereby controls the flow of fluid through a valve seat between first and second ports. A passageway extends between the second port and the primary control chamber and includes a variable flow restriction that decreases as the main poppet moves away from the valve seat. An electrohydraulic pilot valve has a pilot poppet which controls fluid flow from the primary control chamber to the first port in response to pressure in a pilot control chamber. A sub-pilot valve selectively releases pressure in the pilot control chamber to operate the pilot poppet to open and close a path between the inlet and the outlet. Using an electrohydraulic pilot valve enables the main poppet to operate quickly in controlling large fluid flow rates. Unidirectional and bidirectional versions of the control valve are described.

Abstract: A machine, such as a backhoe, has a series of components connected in series and moved by separate hydraulic actuators. A position estimator determines the present position of each component from the load acting on the associated hydraulic actuator and a velocity command for the component. For each component, a function parameter estimator uses the present positions of the components to derive a set of parameters that include a static structure load that the components exert on the associated hydraulic actuator, acceleration and deceleration limits for both directions of component motion, and a control bandwidth for the associated hydraulic actuator. The set of parameters for a given component is used to control the associated hydraulic actuator.

Abstract: A pilot-operated valve has a main poppet controlling fluid flow between inlet and outlet ports in response to pressure in a control chamber. Fluid flow through a pilot passage, linking the control chamber and the outlet port, moves an exhaust spool between first and second positions to control fluid flow through passages in the main poppet. The first position blocks flow between the control chamber and the outlet port and provides a path between the control chamber and the inlet port. In the second position, flow between the control chamber and the outlet port is enabled, and a second path, that is more restricted than the first path, is provided between the control chamber and the inlet port. When the valve closes, flow through the first path allows movement of the main poppet at a faster rate than during opening when flow occurs through the more restricted second path.

Abstract: A hydraulic circuit controls flow of fluid between first and second ports of a hydraulic actuator, such as a cylinder/piston arrangement and each of a supply conduit and a tank return conduit. The hydraulic circuit operates in standard powered operating modes as well as powered and unpowered regeneration modes. In a powered operating mode, a conventional pressure compensated spool valve determines the velocity of the hydraulic actuator. A workport blocking valve connects one workport of the spool valve to the first port and the other workport is connected to the second port. A regeneration shunt valve is directly connected between the first and second ports of the hydraulic actuator. In a regeneration operating mode or a mix of powered and regeneration modes, a combination of the spool valve, the workport blocking valve, and the regeneration shunt valve determines the velocity of the hydraulic actuator.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A hydraulic system has an electrohydraulic valve that controls flow of fluid to operate a hydraulic actuator, such as a cylinder or motor. A set of characterization data is provided which describes performance of the electrohydraulic valve as a function of changes in differential pressure across that valve. The hydraulic system is operated by specifying desired movement of the hydraulic actuator and in response deriving a desired valve flow coefficient which designates a level of fluid flow through the electrohydraulic valve. A compensated control signal is produced from the desired valve flow coefficient and the characterization data, to counter act effects that changes in differential pressure have on flow of fluid. The electrohydraulic valve is activated in response to the compensated control signal.

Abstract: The flow of fluid to a hydraulic actuator is controlled by a valve assembly which operates in different metering modes at various points in time for energy conservation. The metering mode to use is selected in response to the hydraulic load acting on the hydraulic actuator. Specifically, the present magnitude of hydraulic load is determined and compared to first and second thresholds. Below the first threshold only a first metering mode is activated, and only a second metering mode is activated above the second threshold. A combination of the first and second metering modes is utilized when the hydraulic load is between those thresholds, wherein the metering modes are used in proportion to a proportional relationship of the hydraulic load to the first and second thresholds. Using a metering mode combination in this manner smoothes transitions between the first and second metering modes.

Abstract: A servomechanism includes a controller which dynamically estimates the resistance of the solenoid coil in an electrohydraulic valve as part of determining a level of electric voltage to apply to open the valve. The servomechanism receives a current setpoint designating a desired electric current level and senses the actual level of current flowing through the coil. A proportional term is derived from the current setpoint and the actual level of current. Creation of a derivative term is based on the difference between the current setpoint and the actual level of current. A feedforward term is produced by estimating the resistance of the electrohydraulic valve and limiting the feedforward term to a predefined range of acceptable values. The proportional term, derivative term, and the feedforward term are summed to define a desired voltage level, and a PWM signal for driving the electrohydraulic valve is generated based on the desired voltage level.

Abstract: Pressure trapped in an inactive hydraulic actuator can result in the actuator moving in a direction which is opposite to that desired upon subsequent activation. The present method detects a trapped pressure condition and takes remedial action before activating the hydraulic actuator for motion. The pressure differentials across valves that control the fluid flow to and from the hydraulic actuator are used to detect a trapped pressure condition. In response to that detection, a selected valve is initially opened in a manner that releases the trapped pressure while producing motion in the desired direction. After the trapped pressure condition has been resolved, one or more other valves are operated to produce the desired motion of the hydraulic actuator.

Abstract: A method provides several modes for recovering hydraulic energy produced by an overrunning load acting on cylinders connected in parallel to a machine component. In one mode, fluid from first chambers in both cylinders is routed into the accumulator, while other fluid is directed into second chambers of those cylinders. In a different mode, fluid is routed from the first chamber of only one cylinder into the accumulator, and fluid from the first chamber of the other cylinder goes into the second chambers of both cylinders. Yet another mode comprises routing fluid from the first chambers of both cylinders into the second chambers of both cylinders. In still another mode, fluid from the first chambers of both cylinders goes into the return conduit while the second chambers of both cylinders receive fluid from a supply conduit. Several modes of reusing the recovered energy are described.

Abstract: A hydraulic system has a valve assembly with two workports coupled to chambers of first and second cylinders which are connected mechanically in parallel to a machine component. A separation control valve is connected between first chambers of both cylinders, and a shunt control valve is connected between the workports. A recovery control valve couples an accumulator to the first chamber of the second cylinder. Opening and closing the valves in different combinations routes fluid from one or both cylinders into the accumulator where the fluid is stored under pressure, and thereafter enables stored fluid to be used to power one or both cylinders. The shunt control valve is used to route fluid exhausting from one chamber of each cylinder to the other chambers of those cylinders. Thus the hydraulic system recovers and reuses energy in various manners.

Abstract: A hydraulic circuit controls flow of fluid between first and second ports of a hydraulic actuator, such as a cylinder/piston arrangement and each of a supply conduit and a tank return conduit. The hydraulic circuit operates in standard powered operating modes as well as powered and unpowered regeneration modes. In a powered operating mode, a conventional pressure compensated spool valve determines the velocity of the hydraulic actuator. A workport blocking valve connects one workport of the spool valve to the first port and the other workport is connected to the second port. A regeneration shunt valve is directly connected between the first and second ports of the hydraulic actuator. In a regeneration operating mode or a mix of powered and regeneration modes, a combination of the spool valve, the workport blocking valve, and the regeneration shunt valve determines the velocity of the hydraulic actuator.

Abstract: A method for operating an electrohydraulic valve initially derives a characterization value that denotes how magnetic hysteresis affects valve operation. Upon receiving a command that designates a desired magnitude of electric current to be applied to the electrohydraulic valve, that command is modified based on the characterization value to compensate for the magnetic hysteresis. The modified command then is employed to apply electric current to the electrohydraulic valve.

Abstract: A valve assembly controls fluid flow between first and second ports of a hydraulic actuator and each of a supply line and a return line. A first electrohydraulic proportional valve is connected between the supply line and the first port, and second electrohydraulic proportional valve is connected between the supply line and the second port. A first counterbalance valve couples the second port to the return line and operates in response to pressure created by the first electrohydraulic proportional valve and the first port. A second counterbalance valve couples the first port to the return line and operates in response to pressure created by the second electrohydraulic proportional valve and the second port. Thus operation of the first counterbalance valve is slaved to the first electrohydraulic proportional valve, and the second counterbalance valve is slaved to the second electrohydraulic proportional valve.

Abstract: A machine member driven by a hydraulic actuator may oscillate, or wag, when the hydraulic actuator decelerates or stops. The degree of oscillation is a function of the machine member's ability to track a deceleration command, which ability varies with changes in the position of the machine member and the load force acting thereon. To reduce the oscillation, a command that controls operation of the hydraulic actuator is filtered using a filter function that changes with the machine member's load. The load force exerted on the hydraulic actuator which in turn can be designated by fluid pressure that results from the hydraulic actuator. Preferably, the frequency of the filter function is varied inversely with the magnitude of the actuator load force.

Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.

Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.