Abstract: A hydraulic system and method for using the same are provided. The hydraulic system includes a pump, a first actuator having a first head chamber and a first rod chamber, and a second actuator having a second head chamber and a second rod chamber. The hydraulic system further includes a first control valve and a second control valve. The second control valve to selectively provide regeneration fluid flow from the first rod chamber to the first head chamber in response to a first function command is less than a first function command limit, a second function command is greater than a second function command limit, and a second function load is greater than a second function load limit.

Abstract: A hydraulic system and method for using the same are provided. The hydraulic system includes a pump, a first actuator having a first head chamber and a first rod chamber, and a second actuator having a second head chamber and a second rod chamber. The hydraulic system further includes a first control valve and a second control valve. The second control valve to selectively provide regeneration fluid flow from the first rod chamber to the first head chamber in response to a first function command is less than a first function command limit, a second function command is greater than a second function command limit, and a second function load is greater than a second function load limit.

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: 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 hydraulic valve has a main poppet that engages and disengages a valve seat to control the flow of fluid between an inlet and an outlet. Movement of the main poppet is governed by a pilot valve element the opens and closes a pilot passage in the main poppet. The pilot valve element is slideably received in a bore in an armature. The armature is biased toward the main poppet by a first spring and a second spring biases the pilot valve element outward from armature bore and toward the main poppet. The second spring has a lesser spring rate than the first spring. Upon engagement of the pilot valve element with the main poppet continued application of the engaging force causes the second spring to collapse and the pilot valve element to slide within the armature, thereby absorbing some of the force that could otherwise adversely affect the 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: An apparatus is provided which has sensors that detect pressure on opposite sides of a control valve which controls the flow of hydraulic fluid from a source to a hydraulic actuator. The sensors produce electrical signals indicating those pressures. In response to the sensor signals, a controller produces an output signal the operates a proportional control valve to thereby regulate pressure at a node of the hydraulic circuit. Several mechanisms are described that react to the pressure at the node by varying the pressure of the fluid being supplied to the main valve so that a controlled pressure level is achieved.

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.

Abstract: A plurality of hydraulic actuators are connected by valve assemblies to fluid supply and return conduits. Desired operating velocities are specified for the hydraulic actuators and used to define the amounts of fluid flow required by each actuator to move at the respective velocity. Provide the requisite flow amounts, fluid at related pressures must be provided at the different hydraulic actuators. In order for those pressures to occur, a pump has to furnish fluid at a greater pressure to allow for supply conduit losses. A process is provided for determining the pressure that the pump must provide to satisfy the greatest pressure that is necessary for the desired operation of all the hydraulic actuators.

Abstract: A machine has a boom, that is pivotally raised and lowered by a first cylinder, and has a load carrier that is pivoted at the end of the boom by a second cylinder. As a machine operator commands movement of the boom, the position of the load carrier is automatically altered by a controller to prevent a load from falling off the load carrier. The load carrier position with respect to the boom is altered in response to the amount of boom motion to maintain a constant position relationship between the load carrier and a chassis of the machine. Although the boom and load carrier move through different angular positions, the machine control is expressed in terms of the linear motion of the first and second cylinders.

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: 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: A take-up chamber for receiving an elongated filmstrip having a predetermined width between the longitudinal edges thereof and an image area less than the width. The take-up chamber has a chamber housing for accommodating the filmstrip within the chamber. The housing has first and second side walls spaced apart to accommodate the width of the filmstrip, a lateral wall extending between the first and second side walls, and a slit extending through the lateral wall and between the first and second side walls through which the filmstrip may be introduced or withdrawn from the chamber. Two parallel laterally spaced generally circular guides extend the inside of said chamber from adjacent one side of the slit to the other side of the slit. Each guide has a substantially continuous inner surface, to contact only respective longitudinal edges of a filmstrip and cause the filmstrip to wind into a roll within the chamber as the filmstrip is advanced through the slit.

Abstract: Filmstrip receiving apparatus for receiving an elongated filmstrip, comprising:a) a housing defining a stationary exit chamber to receive the filmstrip therein, the housing having: two opposed side walls spaced apart to accommodate the width of the filmstrip; a transverse wall extending between the side walls from an upper front end of the chamber to a lower rear end of the chamber; and an upper opening and a rear opening;b) a deflector mounted to reciprocate between forward and backward positions within the upper opening to define between said deflector and a front end of the upper opening, a filmstrip passage of variable length through which a filmstrip can lengthwise pass downwardly into the exit chamber.A scanner apparatus for scanning image frames of a filmstrip advanced into a scanning station is also provided. Such a scanner has a scanner in the scanning station to scan the image frames of the filmstrip and derive image data related to the scanned image frame.