Abstract: A control system is typically used for controlling the implements of a machine. The control system includes a operator control section and a electronic control section having a module for sensing a pair of control signals from the operator control section. When a lift signal and a dump signal is sensed the module will modify the electronic control section in response to the sensed signals.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal. Boom and bucket angle sensors sense the position of the work implement and responsively produces an boom angle signal and a bucket angle signal respectively. A microprocessor based controller receives the boom angle, bucket angle, and operator command signals, modifies the operator command signal, and produces an electrical valve signal in response to the modified operator command signal. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical valve signal.

Abstract: The present invention relates to a control system for hydraulic power units, in particular hydraulic cylinder-piston-assemblies comprising a valve to be controlled by an electronic controller, the valve controlling the fluid path between the power unit, a pressure source and a reservoir. A pressure sensor and a circuit for differentiating the sensed pressure quantity in response to time is provided for sensing a respective output variable of the power unit. The pressure variation signal is utilized to assist operating the valve to improve the control operation, i.e. to dampen fluid vibrations or to decrease the hammering noise produced in the operation of stamping, nibbling or shearing machines.

Abstract: A fluid operated machine is monitored and regulated by providing a logic with a memory for storing the timings of properly operating functions, and detectors the outputs of which are used to calculate the actual operating timings of the functions. The actual operating timings are compared to the timings in the memory, and if they deviate beyond acceptable tolerances a warning signal is given. In addition to monitoring the timings, the device will also open or close control flow valves to bring the operating speeds of functions within acceptable tolerances.

Abstract: A device and method for suppressing vibration of a working machine in which residual vibration produced immediately after an operation is completed can be suppressed well without degrading the response. The device comprises a working machine acceleration detecting means (11H, 11B), a lever turning degree coefficient calculating means (17) for calculating coefficient in accordance with a lever turning degree, an acceleration compensating value operating means (13) for performing an operation from the acting force calculated from the acceleration of the working machine and a lever turning degree coefficient, and a feedback command means (18) for calculating an acceleration feedback command value from an acceleration compensating value and a lever operation command value and for outputting the acceleration feedback command value to electromagnetic proportional pressure control valves (22, 23).

Abstract: A positioning system uses a position feedback signal to position and damp a platform. The position feedback signal is input to an electronic controller that provides a plurality of control signal that are used to position the platform and dampen the platform motion.

Abstract: In hydraulic heavy equipment, a working device has a boom, an arm and a bucket. An operating device has the same link structure as in the working device. By operating the working device, control valves are operated and the working device functions in a similar manner to the operating device. The movement of the working device is transmitted, and the control valves are brought back to the neutral position. Therefore, the working device follows up the operating device, and functions in the same manner as the operating device.

Abstract: A pneumatic actuating arrangement with a plurality of consumers (1) having working areas (7,8), a plurality of feed air/signal distributors (13) connected to a common pressure source and a common control unit (19), a plurality of electrically-actuated switching devices respectively arranged directly at the consumers (1) forming separate consumer units (9), and a combination line (12) extending between each consumer unit (9) and a feed air/signal distributor (13), each combination line including a supply pressure line for supplying air to the working areas of a respective consumer and electrical signal lines for connecting the electrically-actuated switching devices of a respective consumer unit to said common control unit.

Abstract: A control scheme is provided that controls the maximum pressure level in desired locations of a hydraulic system. This control scheme eliminates the need of separate line relief valves that many times create pressure spikes in the hydraulic system. In one example, the control scheme functions to sense the operating pressure at the desired location and compares it to a differential pressure and a desired input command during one step or loop to establish a predicted pressure level. The predicted pressure level is compared to the pressure necessary to initiate movement of the valving element in an electrically actuated control valve mechanism. The result is used to move the valving element to a predetermined position if the predicted pressure level is less than cracking pressure level and the differential pressure is greater than zero.

Abstract: An engine/pump control device for loaders is disclosed. The control device controllably distributes the output power (rotating force) of an engine to the travelling and working units of a loader in accordance with operational conditions of the loader, thus remarkably improving work efficiency of the loader. When the loader performs an operation requiring a high tractive force prior to the driving force of the working members, the control device opens the unloading valve thereby partially returning the output fluid of a hydraulic pump to a return tank while transmitting the surplus output power of the engine to the traveling unit. Meanwhile, when the loader performs an operation requiring a high driving force of the working members prior to the tractive force, the control device closes the unloading valve, thereby totally supplying the output fluid of the hydraulic pump to the actuators in order to generate a high moving speed of the working members.

Abstract: A control method and a device to control construction equipment attachments include during manual operation, the pilot pressure discharged from a pilot pump is fed from a manual operation valve through an electromagnetic change valve to a main control valve. During automatic operation, the pilot pressure from an automatic-mode selecting valve is fed through an electromagnetic proportional control valve as well as the electromagnetic change valve, all of which are controlled by a controller, to a main control valve. When the operation range is restrictively set during manual operation, the pilot pressure output from the manual operation valve is fed through the electromagnetic proportional control valve as well as the electromagnetic change valve to the main control valve. Both the main control valve and the electromagnetic proportional control valve are controlled by control signals from the controller.

Abstract: The invention is an apparatus for determining a valve transform curve in a fluid system. The fluid system has a valve and a fluid actuator arranged to initiate movement of a load. The invention includes a desired velocity manager, a load responsive device, and a valve transform curve manager. The desired velocity manager determines a desired velocity of the load. The load responsive device determines a characteristic of the load, such as weight or position. The valve transform curve manager receives responsively determine a valve transform curve based on the desired velocity and load characteristic.

Abstract: The ability to be able to identify, distinguish and verify a lock onto harmonic frequency signals in the oil of a hydraulic cylinder using a ratio between consecutively detected harmonics. The identification is useful in providing early and reliable harmonic resonance "lock on" and the ability to "lock on" to a particular order harmonic resonance.

Abstract: A control and safety system for coordinating movement of multiple hydraulic cylinders to reciprocally rotate a truck-mounted refuse compacting arm. The system includes a logic board controller in communication with a cam and switch arrangement mechanically linked to the rotating arm. Signals from the switches indicate the position of the arm to the logic board which responds by operating directional control valves to regulate movement of the cylinders. A pressure switch is activated to rotate the arm in the opposite direction if the arm is prevented from reaching a limit switch.

Abstract: A packaging system includes a stacking apparatus which utilizes a supplemental stacking member on a transfer mechanism for receiving at least one article from a conveying mechanism while the transfer mechanism is transferring a stack, such that a new stack is begun prior to completing the transfer of the first stack. This permits a substantially constant supply of articles to be provided continuously to the stacking apparatus without having to interrupt or slow down the flow of articles to the apparatus. The packaging system also includes a boxing apparatus which relies on pneumatically-actuated positioning mechanisms to move stacks of articles to discrete positions within boxes. Both the position and the velocity of the pneumatic mechanisms are utilized as feedback to provide increased speed without compromising positioning accuracy.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal, which is indicative of a desired velocity. A velocity sensor senses the velocity of the lift cylinder and tilt cylinders and responsively producing respective cylinder velocity signals. A microprocessor receives the cylinder velocity and operator command signals, determines the difference between the actual and desired cylinder velocity, and responsively produces an electrical valve signal in response to the velocity difference. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical value signal.

Abstract: This invention pertains to a hydrostatic actuation system based on a digitally commutated, piston pump. Typically the pump is a fixed displacement axial piston pump with the hydromechanical commutator (which consists of either check valves or a rotated portplate) replaced by electromagnetically activated switches. The activation of the switches coincides with the extreme position of the pistons. The actual switching events are selected by a digital controller to effect an incremental flow rate to a hydraulic actuator. The flow rate consists of minute volumes of fluid displaced at a frequency and polarity dependent on the magnitude and sign of the rate binary applied to the controller.

Abstract: Method for controlling a pressurized fluid-actuated double acting cylinder in an assembly such as a hydraulic tightening spanner (1) with a control unit therefor, wherein a piston (5) may be reciprocated repeatedly, firstly with an active stroke providing a desired maximum force, and then with an opposed passive stroke returning the piston (5) to its starting point to enable repetition, and wherein said method comprises selecting a set fluid pressure corresponding to the desired maximum force (Fr) and measuring the time elapsed (Te) between the beginning and the end of the passive return stroke to determine that the force has been achieved. A device for implementing the force is also disclosed.

Abstract: An apparatus for controllably moving an implement is provided. The implement is connected to a work machine and is movable between first and second implement positions in response to operation of a hydraulic actuator. The apparatus includes a joystick with first and second positions and a neutral position. The joystick is normally biased in a neutral position and is movable between the first and second positions. The apparatus senses the position of the joystick and responsively generates a joystick position signal. The joystick maintained at the first and second detent positions in response to manual movement of the joystick to the respective first and second detent positions. The joystick is released from the detent position in response to receiving a release detent signal. The apparatus senses the position of the work implement with respect to the work machine. The apparatus provides hydraulic fluid flow to the hydraulic actuator in response to a magnitude of an electrical valve signal.

Abstract: A decelerating air circuit having an air cylinder is disclosed. The decelerating air circuit includes a driving solenoid valve having an advance mode and a withdrawal mode. A decelerating solenoid valve having a high speed mode and a low speed mode has an outlet port connected to the decelerating solenoid valve. A constant speed flow control valve is attached to a low speed port of the decelerating solenoid valve. Limit switches are located respectively at an advance end and a withdrawal end of a piston rod of the air cylinder. Decelerating sensors are located respectively between the limit switches. The piston rod advances past a point of a decelerating sensor, triggers the sensor, and causes the decelerating solenoid valve's operating mode to change from a high speed mode to a low speed mode. The change in mode is accomplished by outgoing air being introduced so that it passes through the flow control valve thereby reducing the speed of the piston rod.

Abstract: The apparatus is an oscillator for a showerhead to keep the forming fabric of a papermaking machine clean and open. A hydraulic cylinder is formed with a piston cup assembly dividing the cylinder into first and second fluid chambers. The piston cup assembly is coupled to a magnet and a driveshaft, the driveshaft being coupled, in turn, to the showerhead to be oscillated. A four-way valve is used to direct fluid from a pressurized external source alternately into said first and second fluid chambers thereby causing reciprocation of the driveshaft. The position of the magnet, and hence the driveshaft and showerhead, is monitored by a transducer which sends position and rate signals to a microprocessor-based controller. The microprocessor-based controller sends a signal to the four-way valve to direct which of said first and second fluid chambers receives fluid from the pressurized source in order to achieve the desired parameters of reciprocation.

Abstract: An apparatus for controllably moving a work implement is disclosed. The implement is connected to a work machine and is moveable in response to operation of a hydraulic cylinder. The apparatus includes an operator controlled joystick. A joystick position sensor senses the position of the joystick and responsively generates an operator command signal. An implement position sensor senses the position of the work implement and responsively produces an implement position signal. A microprocessor based controller receives the implement position and operator command signals, modifies the operator command signal, and produces an electrical valve signal in response to the modified operator command signal. An electrohydraulic valve receives the electrical valve signal, and controllably provides hydraulic fluid flow to the hydraulic cylinder in response to a magnitude of the electrical valve signal.

Abstract: A cylinder positioning control apparatus designed to effect positioning of a cylinder by learning control that uses not only an overrun distance but also a cylinder speed as input data for control. The apparatus has a device for taking in a displacement x and speed V of a cylinder, a device for calculating a predicted overrun distance y.sub.i for the present drive from a predicted overrun distance y.sub.i-1 in the preceding drive, a cylinder speed V.sub.i-1 at the time of outputting a braking signal during the preceding drive, and a speed V.sub.i of the cylinder being driven, a device for judging whether or not a condition to be satisfied to output a braking signal is satisfied, and for outputting a braking signal when the condition is satisfied, a device for taking in a displacement x.sub.bp and speed V.sub.bp of the cylinder when the braking signal is output, a device for taking in a displacement x.sub.stop of the cylinder when it has stopped, and a device for calculating a predicted overrun distance y.sub.

Abstract: Apparatus and method for controlling at least one hydraulic cylinder by the hydraulic fluid discharged by a hydraulic pump through a control valve. The hydraulic control system includes sensors to sense the conditions of the system and produce responsive signals. In the first stage, a controller determines an initial pump displacement output value and an initial spool displacement output value as a function of the system condition signals according to a plurality of feedback linearization control laws. In the second stage, a second controller produces an output signal for the hydraulic pump and an output signal for the control valve as a function of the initial pump displacement output value, the initial spool displacement value and an input command signal according to linear control laws.

Abstract: An improved control system for a movement actuator is disclosed for moving a member between a retracted position and an extended position. The movement actuator comprises a cylinder having a piston with a fluid supply providing pressure to a first and a second side of the piston. A control applies a first and a second fluid pressure on the first and second sides of the piston for moving the member from the retracted position toward the extended position with a force related to a difference between the first fluid pressure and second fluid pressure for reducing the possibility of damage to an unintended object in the path of the member. The control applies the first fluid pressure on the first side of the piston upon the member being in proximity to the extended position for moving the member into the extended position with a force related to the first fluid pressure for insuring proper positioning of the member.

Abstract: A control system for controlling the movement of the ram of a press or press brake of the type having one or two main cylinders with pistons operatively attach to the ram. The control system comprises a programmable processor with inputs from a pressure transducer indicating the pressure applied to the one or two pistons and a linear potentiometer for each side of the ram to indicate ram position and levelness. The control system further includes a hydraulic circuit operated by outputs from the processor. The hydraulic circuit comprises a variable volume load sense-controlled pump supplying hydraulic fluid through a speed control assembly to a solenoid-actuated directional valve determining upward and downward movement of the ram. The speed control assembly comprises at least two lines connected to the output line of the pump and to the speed control assembly output line to the directional valve. At least one of the at least two speed control assembly lines is provided with a restricting orifice.

Abstract: The invention relates to a large manipulator, especially for truck mounted concrete pumps. A chassis bears a mast base rotatable about a vertical pivot and an articulated mast consisting of at least three arms. The arms can be pivoted to a limited extent about horizontal, mutually parallel axes in pairs in relation to the adjacent base or arm by means of a drive system. The articulated mast is actuated via a remote control device with control levers.

Abstract: A method for controlling an apparatus (100) for controllably moving an implement (102) is provided. The implement (102) is connected to a work machine (104) and is movable between first and second implement positions in response to operation of a hydraulic actuator (106). The apparatus (100) includes a joystick (306) with first and second positions and a neutral position. The joystick (306) is normally biased in a neutral position and is movable between the first and second positions. The apparatus senses the position of the joystick (306) and responsively generates a joystick position signal. The joystick (306) maintained at the first and second detent positions in response to manual movement of the joystick to the respective first and second detent positions. The joystick (306) is released from the detent position in response to receiving a release detent signal. The apparatus (100) senses the position of the work implement (102) with respect to the work machine (104).

Abstract: Improvement of the ability to detect selected resonant frequencies associated with the position of the piston in a piston position sensing system using electromagnetic waves in the fluid in a hydraulic cylinder is achieved by positioning the electric signal input and output probes with 90 degree separation around the circumferential periphery of the cylinder to suppress coupling into unwanted modes that diminish detectability of particular resonant frequency signals, In a coaxial sensing system "dummy" probes at 90 degree separation to each other and 90 degree separation to the input and output probes operate to improve symmetry and resonance shape and to suppress unwanted modes.

Abstract: A load balancing arm is shown and described as having improved control including a programmable control element and electronic air regulation to provide precise and controllable lifting force on a load. The disclosed load balancing arm responds to slight operator applied force to aid in movement of the load in overcoming system hysteresis, friction and load inertia without requiring the operator to apply a sufficiently large magnitude force to overcome such counteracting forces in the system. The disclosed load balancing arm further includes automatic load weight detection sensors for accommodating variation in load weights while applying a lifting force to the load which substantially equals the weight of the load. This allows the operator to move the load freely throughout a work space.

Abstract: An hydraulic lift system has an actuator connected to an hydraulic circuit, having a pump, via a supply line. A balanced seated valve is connected between the supply line and a reservoir, the valve being controlled by a solenoid and an electric drive unit. The drive unit supplies a gradually increasing or decreasing voltage to the solenoid to open or close the valve gradually. The valve has a valve member that is displaceable along its length and has a valve head of frusto-conical shape. A passage along the valve member balances fluid pressure across the valve member. The solenoid has an armature with a pole face that can be displaced towards a fixed pole face to unseat the valve member. The pole faces have complementary frusto-conical surfaces and there is a non-magnetic washer between them.

Abstract: The present invention relates to a drive of the fluid or electric type having a device for controlling an element for transmitting a driving force to a reciprocating or otherwise moveable or displaceable element and an arrangement for damping the driving force at at least one end of the element's travel. The driving force element is at least single-acting, and the drive may also include mechanical shock absorbers and sensors arranged in the area of the ends of travel. In order to achieve an especially soft striking or contact at the end of travel position of the driving force element, the control device includes a counter-pulse module which, via a pre-positioning sensor associated with at least one movement direction, causes a chronologically settable changeover from a previously flowed-through or activated first switching element associated with a first end of travel position to a previously unactivated second switching element associated with a second end of travel position.

Abstract: A method for controllably moving an implement is provided. The implement is connected to a work machine and is movable between first and second implement positions in response to operation of a hydraulic actuator. The method includes a joystick with first and second positions and a neutral position. The joystick is normally biased in a neutral position and is movable between the first and second positions. The method senses the position of the joystick and responsively generates a joystick position signals The joystick maintained at the first and second detent positions in response to manual movement of the joystick to the respective first and second detent positions. The joystick is released from the detent position in response to receiving a release detent signal. The method senses the position of the work implement with respect to the work machine. The method provides hydraulic fluid flow to the hydraulic actuator in response to a magnitude of an electrical valve signal.

Abstract: The present invention describes an apparatus for achieving power amplification in general press and elevating systems with enhanced control and without the disadvantages of the pneumatic and angle-linked devices. A motor is coupled to a screw and nut for delivering force to at least one transfer piston within a fixed volume at the base of a larger piston. Amplification of power is attained when transfer piston displaces the fluid within the fixed volume. A pressure sensor in the fixed volume and coupled to the motor provides the closed loop feedback required of the control of power amplification. The change in force exerted by the transfer piston has linear relationship with the change in power output of the larger piston.

Abstract: An apparatus (102) is adapted to detect the linear extension (position), velocity and acceleration of a hydraulic cylinder (108). The hydraulic cylinder (108) defines a variable length coaxial resonant cavity (112). Under the control of a controller (228), an RF transmitting section (114) and an RF receiving section (116) are used to determine the resonant frequency of the cavity. The resonant frequency of the cavity (112) is determined by comparing a received signal with a threshold and detecting slope intercept conditions.

Abstract: An automatic cushioning control apparatus for a cylinder of a working machine provides a quiet cylinder cushioning effect, causing little shaking of a vehicle body, without using a mechanical cylinder cushion.

Abstract: A hydraulic lift device for battery operated industrial trucks comprising a hydraulic ram, a hydraulic machine operating as a pump in a load raising cycle and as a motor in a load lowering cycle, a separately excited DC machine operating as a motor in the load raising cycle and as a generator in the load lowering cycle, and energy recovering circuitry which is fed by the DC machine in the load lowering cycle. A load holding valve is disposed in the fluid path between the hydraulic ram and the hydraulic machine. Speed of the DC machine is set by a speed control. A separate field current control includes a desired value setting circuit for determining a desired value for the field current (I.sub.FSoll) from a predetermined relationship between the speed (n.sub.Ist) and the armature current (I.sub.ASoll). Power switches are associated with the field winding and the armature, and are actuated by the current control.

Abstract: An apparatus (102) is for detecting the linear extension (position), velocity and acceleration of a hydraulic cylinder (108). The hydraulic cylinder (108) defines a variable length coaxial resonant cavity (112). Under the control of a controller (228), an RF transmitting section (114) and an RF receiving section (116) are used to determine the resonant frequency of the cavity. The resonant frequency of the cavity (112) is determined by comparing a received signal with a threshold and detecting slope intercept conditions.

Abstract: The present invention provides a method for pressure control of an adjustable pump for a hydraulic system including at least a load. Depending on the size of the system, i.e. the servo cylinder, hydrostatic machine and the line tubing, the fluid volume contained in the system between the adjustable pump and the low pressure side of the load is largely different. In controlling the load pressure in such a system, for example a press or a molding machine for plastic material, a pressure controller adaptively and automatically adjusts the damping factor of the controller and thus the controlling quality independent of the fluid volume of the system to a constant value. It is a benefit of the invention that all adjusting operations of the pressure controller are eliminated which have been necessary heretofore to obtain an appropriate control of the fluid system.

Abstract: An automatic air balancer system capable of maintaining various kinds of load at a predetermined position and then moving the load at a desired speed, or applying a desired mechanical force to various kinds of object. The system includes a device for controlling the pressure at one end side of a balance cylinder to a desired level by a first pressure control valve and for controlling the pressure at the other end side of the balance cylinder to a predetermined level by a second pressure control valve, and a device for obtaining a balance pressure signal for the balance cylinder. Another signal is added to or subtracted from the balance pressure signal, and the resulting signal is input to the first pressure control valve.

Abstract: A hydraulic control system for controlling a flow control valve to drive a hydraulic actuator in response to operation of a control device. This system includes a position detecting sensor for detecting a displacement of the control device, an operation detecting sensor for detecting an operating state of the flow control valve, and a hydraulic control unit for receiving detection signals from the position detecting sensor and the operation detecting sensor.

Abstract: A hydraulic damper for a high speed actuator is provided to bring the actuator to rest with minimum oscillation around a target position. The hydraulic damper comprises a hydraulic circuit to communicate with the actuator over its entire positional range for the purpose of dampening a sudden stop of the actuator about a target position. The actuator is connected by a cable to a reel, the reel being connected to a shaft movement of the actuator produces rotation of the shaft. The shaft is also connected to a hydraulic motor which pumps hydraulic fluid through a hydraulic damper too, in effect, dampen the movement of the actuator.

Abstract: Disclosed is a process for operating a pressure-operated positioning tool or gripping and clamping tool and a tool itself, in which the position of at least one adjusting member is determined and the valve-actuated supply of pressure medium to the adjusting member is regulated depending on position. To take into account the elasticity of the contact elements in the target position and to exert influence after the target position has been reached in a process and in a tool of the generic type, the regulating of the valve-actuated supply of pressure medium is not only effected in a position-dependent manner, but also takes into account the pressure of the pressure medium.

Abstract: The device according to the invention includes at least one rotational actuator fitted with a return spring and a connecting rod connected to the rotational actuator to transmit a linear movement to a mechanical part. The rotational actuator is moved by a rotational electromagnet whose angular position is controlled by a pulsed, periodic current. The device also includes apparatus for removal of the magnetizing energy stored in the electromagnet.

Abstract: An apparatus (102) is adapted to detect the linear extension (position), velocity and acceleration of a hydraulic cylinder (108). The hydraulic cylinder (108) defines a variable length coaxial resonant cavity (112). Under the control of a controller (228), an RF transmitting section (114) and an RF receiving section (116) are used to determine the resonant frequency of the cavity. The resonant frequency of the cavity (112) is determined by comparing a received signal with a threshold and detecting slope intercept conditions.

Abstract: A method of controlling a cylinder apparatus includes the steps of supplying compressed air of a first high pressure to one chamber of a cylinder which is divided into two chambers by a piston, and exhausting air from the other chamber so as to move the piston from the start position at an end portion of one chamber toward an end position at an end portion of the other chamber along the extending direction of the cylinder, and detecting if the position has passed the position of a sensor. In addition, a moving speed of the piston is decreased by supplying air of a second high pressure lower than the first high pressure to the other chamber after an elapse of a predetermined wait time from when the piston has passed the position of the sensor, so that the piston reaches the end position in a shock-free state.

Abstract: A closed loop control system for a pneumatic actuator using position and pressure feedback signals. The feedback signals are supplied to a microprocessor which successively generates a desired acceleration, a desired actuator force, a desired gas pressure, and a gas mass flow rate command for a gas flow controlling valve. The use of the gas flow rate as a control variable decouples pneumatic ronlinearities from the control loop. Nonlinear viscous friction, coulomb friction and load effects are decoupled from the control loop prior to the calculation of the desired pressure. An improved trajectory is achieved by employing a plurality of trajectory phases, including a velocity control phase.

Abstract: In a stability compensating mechanism of an electro-hydraulic servo system which includes a load-displacement detecting unit for detecting a displacement of a piston of actuator or a displacement of a load connected to the piston, and a control valve for supplying a hadraulic oil to the actuator to drive the load and in which a piston-displacement detection signal of the load-displacement detecting unit is fed as a feedback signal back to a forward circuit and the control valve is operated by a deviation signal between the feedback signal and a command signal, the stability compensating mechanism comprising a valve-displacement detecting unit for detecting a valve displacement of the control valve and outputting a valve-displacement detection signal representative of the valve displacement, and a load-pressure computing unit for computing a load pressure that is acted on the actuator due to the load, on the basis of the piston-displacement detection signal of the load-displacement detecting unit and the valve

Abstract: The present invention provides an apparatus for controllably actuating a work implement. The work implement includes at least a first linkage and a second linkage. The apparatus produces a control signal, senses the position and velocity of the first and second linkages and responsively produces position and velocity signals. The apparatus responsively produces a command signal as a function of the control signal and the position and velocity signals. The command signal controls actuation of the first linkage such that dynamic coupling between the first and second linkages is minimized.

Abstract: An apparatus for operating feed bars to move a workpiece between stages of a pressing machine includes cylinder devices. Each of the cylinder devices serves to move the feed bars linearly and each has a respective absolute encoder. The cylinder devices include a feed cylinder device which is responsive to hydraulic pressure to linearly advance and return the feed bars. First and second clamp cylinder devices are responsive to hydraulic pressure to move the feed bars linearly so as to clamp and unclamp the workpiece between the feed bars A hydraulic pressure supply circuit is connected commonly to each of the cylinder devices. Hydraulic pressure is applied to the cylinder devices through respective servo valves of a hydraulic valve arrangement.