Abstract: A hydraulic power control system for a work machine is provided. The system may include a hydraulic power output device selected from the group consisting of a hydraulic motor and a work implement hydraulic actuator. The system may also include a variable displacement hydraulic pump configured to supply hydraulic fluid to the hydraulic power output device. The system may further include at least one pressure sensor configured to measure pressure of the hydraulic fluid at a location between the pump and the hydraulic power output device. In addition, the system may include at least one temperature sensor configured to measure a temperature of the hydraulic fluid in the system. The system may include a controller configured to control a displacement of the pump based on a pressure measurement of the at least one pressure sensor and a temperature measurement of the at least one temperature sensor.

Abstract: A control system for a work machine having a plurality of removably attachable work tools is disclosed. The control system has a tool recognition device configured to generate a recognition signal corresponding to each of the removably attachable work tools, and at least one fluid actuator configured to move at least one of the plurality of removably attachable work tools. The control system also has at least one fluid sensor configured to generate a load signal and at least one operator interface device configured to generate a desired velocity signal. The control system further has a controller in communication with the tool recognition device, the at least one fluid actuator, the at least one fluid sensor, and the at least one input device. The controller is configured to command a velocity for the fluid actuator in response to the recognition signal, the load signal, and the desired velocity signal.

Abstract: A method is provided for controlling hydraulic flow through a valve in fluid communication with a pump and a hydraulic actuator. The method includes monitoring load pressure of the valve, and selecting a flow limit and a pressure limit of the valve. A flow-pressure relationship in the valve is determined based on the flow limit, the pressure limit, and a desired flow-pressure characteristic. A hydraulic flow rate command is computed based on the determined flow pressure relationship and the monitored load pressure of the valve.

Abstract: A method is provided for controlling hydraulic flow through a valve. The method includes determining a pressure drop across the valve and estimating a flow rate through the valve based on the pressure drop and a displacement of the valve. A command signal to actuate the valve is computed based on a desired flow rate and the estimated flow rate through the valve.

Abstract: A method is provided for controlling hydraulic flow through a valve in fluid communication with a pump and a hydraulic actuator. The method includes monitoring load pressure of the valve, and selecting a flow limit and a pressure limit of the valve. A flow-pressure relationship in the valve is determined based on the flow limit, the pressure limit, and a desired flow-pressure characteristic. A hydraulic flow rate command is computed based on the determined flow pressure relationship and the monitored load pressure of the valve.

Abstract: An apparatus for controlling an electrohydraulic system of a work machine having an engine that drives a variable displacement pump is disclosed. A pump displacement setting device produces a pump command signal indicative of a desired displacement of the variable displacement pump. An engine speed setting device produces an engine command signal indicative of a desired rotational speed of the engine. A power manager receives the pump and engine command signals, determines an efficient engine speed and pump displacement, and produces an engine control signal that decreases the engine speed to the efficient engine speed and a pump control signal that increases the pump displacement to an efficient pump displacement, while maintaining a substantially constant pump flow rate.

Abstract: In order to accomplish many tasks of a machine efficiently, a motion planning system predetermines the response of the machine to a given set of motion commands. With two or more actuators being driven by a single hydraulic pump, there may not be adequate hydraulic pressure to drive both of the actuators at the speed requested. In order to determine the non-linear response of the actuators and the optimal combination of motions of the moving parts driven by the actuators, a controller for the machine is modeled as a linear dynamic system. The non-linear response of the actuators is modeled using a look-up table that is a function of internal variables of the machine's actuators and hydraulic system. The number of input, or independent, variables that are supplied to the table look-up functions is proportional to the number of actuators being driven by a single pump. Sensors provide data regarding the internal state of each actuator including variables such as spool valve position and cylinder force.

Abstract: An apparatus for controlling an electrohydraulic system of a work machine having an engine that drives a variable displacement pump is disclosed. The apparatus includes a pump displacement setting device that produces a pump command signal, a pressure sensor that detects the fluid pressure associated with the variable displacement pump and produces a pressure signal, and an engine speed sensor that detects the speed of the engine and produce an engine speed signal. A microprocessor computes the torque demand on the engine in response to the desired pump displacement, determines a torque limit associated with the engine in response to the engine speed, and responsively modifies the pump command signal to limit the engine torque.

Abstract: A hydraulic control system has a closed center control valve disposed to control flow of pressurized fluid from a pump to an actuator and a bypass valve disposed to control fluid flow through a bypass line connecting the pump to a reservoir. A controller connected to the control valve and the bypass valve is operative to controllably move the control valve toward an open, flow communicating position and the bypass valve toward a closed flow blocking position. A pressure compensating valve is disposed in the bypass line to maintain a predetermined pressure differential across the bypass valve when the pressure upstream of the bypass valve exceeds a predetermined level so that the flow through a area opening in the bypass valve is substantially commensurate with the opening at pressures above the predetermined level.

Abstract: A hydraulic drive system for a construction machine includes a pump for delivering fluid under pressure from a fluid reservoir, at least one hydraulic actuator selectively driven by the pressurized fluid, and at least one closed-center directional control valve connected in parallel to the pump. The control valve has an "off" position which blocks fluid flow therethrough and at least one "on" position for controlling the flow of fluid to the hydraulic actuator. A control device generates a signal for actuation of the hydraulic actuator. A control unit receives the control device signal for operating the control valve associated with the hydraulic actuator. A bypass line leads from the pump back to the reservoir. A variable position bypass valve is interposed in the bypass line and controls flow through the bypass line. The control unit modulates the bypass valve for optimum operation. A hybrid control senses pressure in the actuator and modifies the control signal in response to the load pressure.

Abstract: A control system is provided for a hydraulic circuit having first and second hydraulic valves, a valve spool position sensor, and first and second input devices for producing first and second operation signals. A controller receives a signal from the valve spool position sensor and the second operation signal and responsively modifies the value of the second operation signal in response to the valve spool position signal.

Abstract: Apparatus and method for controlling at least one hydraulic actuator by the hydraulic fluid discharged by a variable displacement hydraulic pump through a closed-center valve and a separate bypass valve. The apparatus receives a mode signal and a stroke signal and responsively controls the output of the variable flow hydraulic pump with either velocity or force modulation control.

Abstract: A hydraulic system for a construction machine includes a pump for delivering fluid under pressure from a fluid reservoir to at least first and second main valves. First and second input devices are included for producing first and second control signals that are indicative of a desired operation of the hydraulic system. A controller responsive to at least the first and second control signals is provided and produces a compensating signal in response to the first and second control signals. The second main valve is operated in response to both the second control signal and the compensating signal.

Abstract: A displacement controlled hydraulic proportional valve is provided with a dashpot disposed between a main valve spool and a pilot valve spool to stabilize the proportional valve. The dashpot includes a bore in a spring retainer engaging the main valve spool and a plunger axially extending from a spring retainer engaging the pilot valve spool with the plunger extending into the bore to define a dashpot chamber. The plunger is sized to permit restricted fluid flow thereby when the spools move relative to each other thereby dampening relative movement between the valve spools. Dampening the relative movement between the valve spools drastically reduces the amount of overshoot by the main valve spool.

Abstract: An apparatus is provided for use in a vehicle having a source of pressurized fluid and a pair of hydraulic drive motors connected to the pressurized fluid source and powered thereby. First and second ground engaging devices are connected to and driven by the first and second motors, respectively. The apparatus includes first and second control members, each being positionable at a plurality of locations for indicating a desired speed and direction for a respective drive motor. First and second actuators are adapted to sense the position of the first and second control members, respectively, and responsively control the direction and rate of fluid flow to the first and second drive motors. A set switch is movable between first and second positions and is adapted to produce a set speed signal in the second position.

Abstract: An apparatus for controllably actuating a hydraulic actuator is provided. The apparatus is connected between a source of pressurized hydraulic fluid and the hydraulic actuator. The apparatus controllably provides pressurized hydraulic fluid to the hydraulic actuator. The apparatus includes a controller for receiving an operating signal and a load pressure signal and responsively actuating the hydraulic actuator.

Abstract: A control system is provided for use with a hydraulic system which includes a source of pressurized fluid, a plurality of flow regulator means, and a plurality of fluidly powered components. Each flow regulator means is adapted to receive the pressurized fluid and is responsive to a respective control signal for regulating the flow of pressurized fluid to respective fluidly powered components. The control system includes a plurality of control members, each being movable to a plurality of locations for indicating a desired fluid output for a respective flow regulator means. A plurality of sensors are provided for sensing the position of respective control members and responsively producing respective position signals. A primary controller is adapted to receive the position signals, process the received signals to responsively produce the control signals, and deliver the control signals to the flow regulator means.

Abstract: An apparatus for limiting the power output of a hydraulic system is disclosed. The hydraulic system has a variable displacement pump. The variable displacement pump has a movable swashplate and is driven by a source of motive power. The apparatus includes a memory device for storing a set of power modes. Each power mode has a predetermined power level associated with the hydraulic system and is defined by a plurality of set points. Each set point corresponds to a predetermined flow rate and discharge pressure of the pump. A device senses the speed of the source of motive power and producing a signal representative of the actual speed in response to the sensed speed. A device senses the pressure of the variable displacement pump and produces a signal representative of the actual pressure in response to the sensed pressure. A device senses the swashplate angle of the variable displacement pump and delivers a signal representative of the actual swashplate angle in response to the sensed swashplate angle.

Abstract: An apparatus for controllably actuating at least two hydraulic actuator is provided. The apparatus controllably provides pressurized hydraulic fluid to the hydraulic actuators through closed center spool valves. The apparatus receives operating signals and a pump pressure signal and responsively controls the output of a variable flow pump. In a first mode, the output flow of the pump is a function of the operating signals and the pump pressure signal. In a second mode, the output flow of the pump is a function of the operating signals alone.

Abstract: High pressure cutoff controls are useful for variable displacement hydraulic pumps for reducing power losses at high pressure levels. Some operators, however, believe that they get more work from pumps not having the high pressure cutoff control. The subject on-off high pressure cutoff control includes an on-off valve disposed in a pilot passage connected to an output port of a pump and to an end of a high pressure cutoff valve. The on-off valve is selectively movable between a first position at which pressurized fluid passes through the pilot passage to the end of the high pressure cutoff valve to prevent it from functioning as a high pressure cutoff valve. Thus, an operator has the option of operating the hydraulic pump with or without the high pressure cutoff control.