WO2009111265A1 - Procédé et dispositif de surveillance et de contrôle d'un processus à commande hydraulique - Google Patents

Procédé et dispositif de surveillance et de contrôle d'un processus à commande hydraulique Download PDF

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Publication number
WO2009111265A1
WO2009111265A1 PCT/US2009/035290 US2009035290W WO2009111265A1 WO 2009111265 A1 WO2009111265 A1 WO 2009111265A1 US 2009035290 W US2009035290 W US 2009035290W WO 2009111265 A1 WO2009111265 A1 WO 2009111265A1
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Prior art keywords
pump
hydraulic
torque
output
pressure
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Application number
PCT/US2009/035290
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English (en)
Inventor
Peter T. Carstensen
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Kadant Inc.
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Application filed by Kadant Inc. filed Critical Kadant Inc.
Publication of WO2009111265A1 publication Critical patent/WO2009111265A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
    • F04B17/03—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/06—Control using electricity
    • F04B49/065—Control using electricity and making use of computers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2201/00—Pump parameters
    • F04B2201/12—Parameters of driving or driven means
    • F04B2201/1202—Torque on the axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2201/00—Pump parameters
    • F04B2201/12—Parameters of driving or driven means
    • F04B2201/1208—Angular position of the shaft
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2203/00—Motor parameters
    • F04B2203/02—Motor parameters of rotating electric motors
    • F04B2203/0201—Current
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2203/00—Motor parameters
    • F04B2203/02—Motor parameters of rotating electric motors
    • F04B2203/0207—Torque
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2203/00—Motor parameters
    • F04B2203/02—Motor parameters of rotating electric motors
    • F04B2203/0209—Rotational speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/05—Pressure after the pump outlet
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/09—Flow through the pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/13—Pressure pulsations after the pump

Definitions

  • the present invention relates to a method for monitoring and controlling a hydraulic pump. More specifically, the invention relates to a method and device for monitoring and controlling a hydraulic actuated process indirectly by monitoring and controlling an electric motor driving a positive displacement hydraulic pump.
  • This invention also relates to a precision hydraulic energy delivery system.
  • Direct coupling of the pump to a primary mover (motor) and related motor control allows for complete motion control of a hydraulically driven machine without the use of any downstream devices.
  • motion control algorithms in the motor control the hydraulic output at the pump head is controlled in a feed forward method.
  • a positive displacement pump is usually a variation of a reciprocating piston and a cylinder, of which the flow is controlled by some sort of valving. Reciprocal machinery, however can be less attractive to use than rotary machinery because the output of a reciprocal machine is cyclic, where the cylinder alternatively pumps or fills, therefore there are breaks in the output. This disadvantage can be overcome to a certain extent by: using multiple cylinders; bypassing the pump output through flow accumulators, attenuators, dampers; or waste gating the excess pressure thereby removing the high pressure output of the flow.
  • reciprocating pumps In addition to uneven pressure and flow output, reciprocating pumps have the disadvantage of uneven power input proportional to their output. This causes excessive wear and tear on the apparatus, and is inefficient because the pump drive must be sized for the high torque required when the position of the pump connecting rod or cam, in the case of an axial (wobble plate) pump, is at an angular displacement versus the crankarm dimension during the compression stroke that would result in the highest required input shaft torque.
  • an eccentric transmission transmits a torque demand from a reciprocating pump, which varies with time, to the drive motor such that the torque demand on the drive motor is substantially constant.
  • the result is the leveling of torque variation required to drive a positive displacement pump at the transmission input shaft with the effect of constant pump output pressure. This is accomplished by means of eccentric pitch circle sprocket sets with gear belts or eccentric pitch circle matched gear sets.
  • a position sensor outputs a signal by sensing the position of a piston in a linear compressor.
  • a controller receives the position signal and sends a control signal to control directional motion output from a linear motor.
  • eighteen or nineteen torque leads are measured along the main shaft in order to maintain constant shaft velocity revolution and are translated to a required motor torque for particular angles of the main shaft.
  • U.S. Patent No. 4,971,522 uses a cyclic lead transducer input and tachometer signal input to a controller to signal varied cyclic motor input controls to provide the required motor torque output.
  • a flywheel is coupled to the motor in order to maintain shaft velocity. However, the speed of the motor is widely varied and the torque is varied to a smaller extent.
  • U.S. Patent No. 5,141,402 discloses an electrical current and frequency applied to the motor which are varied according to fluid pressure and flow signals from the pump.
  • U.S. Patent No. 5,295,737 discloses a motor output which is varied by a current regulator according to a predetermined cyclic pressure output requirement.
  • the motor speed is set to be proportional to the volume consumed and inversely proportional to the pressure.
  • a pump can produce constant pressure and therefore constant flow without the typically associated ripple common to power pumps for the full range of the designed volumetric delivery, by driving them in a feed forward method.
  • the prime mover in such systems is typically a constant speed induction motor.
  • a processor be it mechanically balanced or electronic
  • hydraulic servo valves must be placed into the hydraulic stream for flow and pressure regulation.
  • This treatment of hydraulic delivery places the "smarts" of the system in the hydraulic output portion of the system.
  • these systems require many hydraulically driven devices, are mechanically (geometry) limited, are energy inefficient when total system performance is scrutinized and have a small range of dynamic response (typically 10-1).
  • Typical examples of a command-response curve of a small servo valve and a large servo valve are shown in Figures 9 and 10, respectively.
  • An example of another hydraulic process, also to which one embodiment of the present invention is directed to, would be presses (such a metal forging presses and laminating presses) driven by hydraulic cylinders.
  • presses such a metal forging presses and laminating presses
  • valves and feedback controls are used to control the critical process variables of applied force and the rate of actuation.
  • transducers are employed both to facilitate control and to monitor the process.
  • level switches, pressure transducers and flow switches are often employed to monitor system conditions such as low oil levels, plugged pump inlet filters and burst hoses. Use of such transducers adds to the system cost and complexity and is prone to failure particularly in hostile environments.
  • Figure 13 shows an experimental and simulated result for the ram load as derived from the ram pressure measurement.
  • the plot reveals that approximately 88.96 kN are needed to overcome the counter-balance and frictional forces.
  • the load increases rapidly beginning at approximately 3.5 seconds. This corresponds to impact with the workpiece. Beginning at approximately 4 seconds, elastic deformation of the workpiece and tooling ceases and plastic deformation of the workpiece begins. It is clear from the data that the press was able to maintain the desired velocity under load, as long as the load did not increase too rapidly, but as soon there was a sudden increase in load, the desired velocity is lost.
  • Control laws need to be designed to be robust so that different loading conditions and velocity profiles can be handled successfully without the need for customized tuning.
  • a further objective of the invention is to provide controllers that maintain coordination for all operating conditions without expensive and complicated feedback devices and control loops.
  • Another object of the present invention is to provide a method for electronic attenuation of pump torque variation requirements in order to produce a matched motor torque output that will result in constant output pressure from a pump.
  • Yet another object of the present invention is to provide monitoring and control factors which vary the power and torque output of a pump motor based on calculated torque variation requirements.
  • Yet another object of the present invention is to increase the energy efficiency of a pump system, by providing a force balanced relationship between the motor output and the application's hydraulic requirement, thus allowing the use of energy saving torque drives without incurring the pressure variations associated with their use.
  • Yet another object of the invention is to create precise hydraulic output from the pump utilizing an algorithm programmed into the drive control that systematically measures and corrects for three key physical parameters of the motor, pump and hydraulic fluid combination.
  • the three parameters being windage torque, viscous torque and coulomb torque.
  • the invention also provides for development of an empirical understanding of the positive displacement pump in regards to slippage (variation from theoretical displacement) throughout the full pressure/flow delivery range of the pump. This understanding combined with the drive controller's precise measurement of motor rpm gives an extremely precise measurement and control of hydraulic fluid flow rate.
  • knowing the displacement volumes of the cylinder being actuated and mathematically correcting for elasticity of the piping system allows for very precise control and or measurement of press-ram position, and/or ram velocity than may be achieved with prior art.
  • the invention employs the feed forward torque control aspects of the drive system to precisely monitor and/or control hydraulic pressures created by the pump which after mathematical correction for line losses at various flow rates, mimics load at the press ram.
  • the invention also provides both a more precise and a more robust method than does the prior art.
  • a method for obtaining a polar map for process control within the electronic drive of a targeted pump This polar map is calculated by a processor or is externally calculated then input into a processor. Once the torque profile of the pump is obtained and translated into a polar map, the processor can compare the shaft displacement angle of the pump input shaft to the reference polar map.
  • the processor can also take into account selected factors such as the response time of the pump drive, the motor inductive reactance, system inertia, application characteristics of the pump, and regenerative energy during deceleration of the pump. Using selected factors and the comparison results, the processor signals the motor controller to vary the amperage, voltage, and frequency applied to the motor in order to regulate the torque output of the pump motor. With an accurately modulated motor torque output in concert with the established polar map (for the targeted pump), the pump output pressure will remain constant regardless of the pump's crank arm location or the velocity of fluid flow.
  • Figure 1 is a block diagram of the steps required for a method of electronic attenuation of torque profile and the resulting control of the pump
  • Figure 2 is a graph depicting individual input torque variation for each node of a triplex pump based upon pump input shaft rotational degrees
  • Figure 3 is a graph depicting a percentile summation of input torque variation compared to angular displacement of the input shaft of a triplex pump
  • Figure 4 is a table depicting variations of input torque above and below the mean for triplex pumps in relation to the linear distance between the plunger/piston pivot point and the throw pivot point multiplied by the throw radius;
  • Figure 5 is a graph depicting a plotting of geometric distance variation points based upon the summation of total torque variation for a triplex pump
  • Figure 6 is a polar map depicting the torque profile versus angular displacement of a pump input shaft
  • Figure 7 is a diagram illustrating a precision hydraulic delivery system according to the present invention
  • Figure 8 is a graph depicting a profile of torque vs. velocity for an exemplary hydraulic system in accordance with the present invention
  • Figure 9 is a graph depicting command, response curves of a small servo valve
  • Figure 10 is a graph depicting command, response curves of a large servo valve
  • Figure 11 is a schematic of a hydraulic press system according to one embodiment of the invention
  • Figure 12 is a graph depicting commanded, simulated and experimental ram velocity profiles not within normal boundaries
  • Figure 13 is a graph depicting simulated and experimental ram load profiles not within normal boundaries
  • Figure 14 is a diagram of "electronic line-shafting" with a master/slave configuration of multi-drop positive displacement hydraulic pumps, according to one embodiment of the invention
  • Figure 15 is a schematic of a typical non-compensated electronic line- shafting in a multi-axis hydraulic machinery; and Figure 16 is a diagram of a system incorporating the Learn TQ items:
  • the output characteristic of volumetric displacement would directly relate to the input torque variations above 10 and below 12 the comparative mean 14.
  • the processor identifies the output discharge characteristics such as the number of plungers, pistons in a piston pump, or vane/gear in a rotary pump.
  • the processor also utilizes a comparative mean where, the comparative mean is representative of the basic torque requirement of the pump input shaft rated at a specific output pressure of the pump.
  • a pulsation pattern 16 would be repeated at the same rate per revolution as the number of the pump's volumetric displacement cavities.
  • a triplex positive displacement pump would repeat a pulsation pattern 16 every 120 degree rotation of the pump input shaft.
  • a pulsation pattern would be produced five times per revolution of the pump input shaft, repeating every 72 degrees if the output pressure is to remain constant; and for a rotary vane pump with nine vanes selected, the pulsation pattern would repeat every 40 degree rotation of the pump input shaft if the output pressure is to remain constant.
  • the torque profile versus displacement angle of the targeted pumping system is the summation of the torque requirement for each volumetric displacement component, depicting a percentage above mean 18 and the percentage below mean 20.
  • the magnitude of the input torque variation for the power pump is determined by the processor, where the magnitude of the torque variation is the number of volumetric displacement cavities activated in one revolution and the relationship "Q".
  • Figure 4 in table form depicts the percentile variations of input torque above and below the mean for triplex pumps with various "Q".
  • Figure 5 graphically depicts the total torque variation to show a torque profile for a triplex pump (three volumetric displacements per revolution) with a "Q" at 4: 1 with variations shown above and below the mean.
  • the mean is representative of the basic rms (root mean squared) torque requirement of the pump input shaft rated at a specific output pressure of the pump versus the angular displacement of the pump crank shaft.
  • the relationship of "Q" and the effect it has on torque variation would also apply to rotary pumps.
  • a plotted geometric distance variation using tl-tl5 (as plotting points) is then imposed on the torque profile.
  • a pump polar map is determined based on the torque profile and the input shaft angular displacement of the pump.
  • the center 34 of the polar map is to represent zero torque.
  • the incremental lines 36 depicted orbitally are the angular displacement of the targeted pump's input shaft.
  • the plotted pump torque variation curve 38 that occurs above and below the mean 40 is to be considered a geometric percentage of the summation of the torque requirement of each of the volumetric displacement components of the targeted pump.
  • the distance of each point plotted on the polar map's center from the base diameter's center is the geometric distance variation (over or under) of the base radii percentile established from torque versus the pump input shaft displacement angle (tl thru tl5).
  • the geometric distance variations are the plotting points determined in Figure 5.
  • the torque versus angular displacement profile of the pump system selected is to become the reference polar guide for the comparitor algorithm in the processor in Block 5 of Figure 1.
  • the reference polar guide determined by the processor in Blocks 1-5 can also be determined externally from the processor and then input into the processor.
  • Blocks 6-10 of Figure 1 are the operating steps from electronic attenuation of the torque profile to provide a constant output pressure at the pump, wherein Block 6 indicates the transmission of the angular displacement of the input shaft of a pump in operation.
  • a pulse transmitter mounted on the input shaft relays to a counter — which is part of the processor — the angular position of the pump drive.
  • an electronic processor gathers this output shaft orientation feedback information, and processes the angular displacement data.
  • the processor then attenuates from the peak requirement of the pump, the output torque of the drive compared to the predetermined reference polar map of Block 5. A corresponding torque command value is then selected.
  • Block 9 of Figure 1 based upon the inputs of Blocks 7 and 8, the processor of the electronic drive signals the motor controller to apply the correct amperage, voltage, and frequency to the motor which then provides the correct torque according to the angular displacement of the pump input shaft.
  • Block 11 of Figure 1 depicts the use of this method in future systems where information gathered from pump operation by this method can be used to design more responsive components such as transmissions and electronic drives. More responsive components would decrease the time increments between
  • Fig. 7 depicts a precision hydraulic delivery system 71 according to the present invention.
  • this system provides direct coupling of a positive displacement pump 72 to a prime mover 73 and related motor drive control 74.
  • the prime mover 73 in the pump system shown is, for example, a constant speed induction motor.
  • the motor has, for example, a 1000-1 (torque) turn down ratio.
  • the motor control 74 may be, for example, an electronic servo or hydraulic type motor control. Direct coupling of the pump 72 to the motor 73 and motor control 74 allows for complete motion control of the pump 72 without requiring any of the downstream flow control devices, feedback devices, hydraulic energy storage devices (accumulators) or energy dissipation devices normally used in conventional pump systems.
  • the system in Figure 7 employs motion control algorithms in the electronic motor control so that the hydraulic output at the pump head will simultaneously follow the control signals generated by the algorithms and sent to the motor.
  • This ability allows a large dynamic range of hydraulic energy to be delivered by placing the "smarts" of the system directly into the electrical handling capabilities of the prime mover circuit.
  • the modulation of torque (resulting in hydraulic pressure) and velocity (resulting in hydraulic flow) are most efficiently handled within the electronic servo or hydraulic type control of the primary mover.
  • Patent No. 5,971,721 which are hereby incorporated by reference, may be incorporated into the macro motion control capabilities described herein to provide improved system response, "keypad” tuning of a hydraulic application, very high systemic efficiency characteristics and simplified hydraulic circuitry.
  • keypad tuning of a hydraulic application
  • very high systemic efficiency characteristics and simplified hydraulic circuitry.
  • Several exemplary control features of the present invention are described in greater detail below. These features represent only a fraction of the possible features that may be electronically integrated into a hydraulic delivery system by control algorithms and subroutines for a prime mover servo control system coupled to a pump.
  • the "SLAM” subroutine is an energy absorbing function that provides hydraulic component protection by eliminating pressure spikes.
  • a “spike” in pressure occurs when flow volume is rapidly reduced. This normally occurs when, for example, a directional control valve is shut, and is typically followed by the pressure relief valve waste-gating the excess flow to a tank until the system flow returns to normal.
  • the present invention has a discrete input that activates the "SLAM” function when such an event occurs. A determination as to the likelihood of such an event is made during commissioning.
  • Use of the "Position Sensing” feature allows the "SLAM” subroutine to be invoked when necessary.
  • the "SLAM” feature causes the electronic drive to capture the inertial energy of the system via the regenerating capabilities of the prime mover (turning the motor into a generator), and to store this captured electrical energy in the electronic drive (see “energy storage system” below). The normally waste-gated energy is thus captured by the drive during this function, thereby saving energy and reducing wear on the hoses and hydraulic system.
  • the "JAB” feature eliminates pressure "droop" by invoking a rapid pump acceleration feature of user defined time and amplitude, that is applied over and above the normal flow or pressure input commands. In some instances, a rapid increase in flow volume required by the application will cause the pressure to droop until high inertia components in the pumping system are accelerated to the required delivery velocity. If this droop is undesirable in a specific application, a discrete input can be used to activate this "JAB" rapid acceleration feature that is applied over and above the normal flow or pressure input commands that are controlling the pump. Dual Function Pump/Motor feature
  • This feature provides for single unit hydraulic motor/pump functions from the same hydraulic device for energy delivery and reclamation (regeneration and storage).
  • This feature provides a constant horse power electrical drive system for maintaining an energy ceiling regardless of the delivered flow volume.
  • This feature provides an electrical energy storage device in the drive system for reclamation of energy from regeneration (see “Dual function pump/motor” and “SLAM” function), or for high output energy spikes typically provided by a hydraulic accumulator.
  • “Position Sensing” feature provides an electrical energy storage device in the drive system for reclamation of energy from regeneration (see “Dual function pump/motor” and “SLAM” function), or for high output energy spikes typically provided by a hydraulic accumulator.
  • a volumetric pulse correlates to a pump output volume that will cause an incremental pulse to occur.
  • This volumetric pulse (output by the electronic drive module inclusive of compensation factors Pump TQ Learn and application items REDUX V and REDUX P) is used for the positioning of known hydraulic cylinders and their corresponding volumetric displacements.
  • Gain Zero For "pressure delivered” vs. "zero velocity" (the RPM of this point is always anchored at zero RPM), the Gain Zero corrects the pressure reference command as the velocity decreases to "0" to compensate for systemic "sticktion".
  • Gain Low For "pressure delivered” vs. "velocity," the Gain Low corrects the pressure reference command as the velocity increases/decreases to compensate for system losses.
  • Gain Low RPM Applies the "GAIN LOW" value when the pump system is operating within a user defined RPM range (typically, 0 to 50 RPM). The gain is applied as a tapered offset beginning with the "GAIN ZERO” value at 0 RPM, and ending with the “GAIN LOW” value at the “GAIN LOW RPM.” Any operation above this speed is ramped to the "GAIN MID" point.
  • Gain Mid For "pressure delivered” vs. "velocity,” the Gain Mid corrects the pressure reference command as the velocity increases/decreases to compensate for system losses.
  • Gain Mid RPM Applies the "GAIN MID” value when the pump system is operating within a user defined RPM range (typically, 50 to 700 RPM). The gain is applied as a continued offset beginning with the "GAIN LO” value at the “GAIN LO RPM” and ending with the “GAIN MID” value at the “GAIN MID RPM.” Any operation above this speed is ramped to the "GAIN HI” point. 4. Gain High: For "pressure delivered” vs. "velocity,” the Gain High corrects the pressure reference command as the velocity increases/decreases to compensate for system losses.
  • Gain High RPM Applies the "GAIN HIGH” value when the pump system is operating within a user defined RPM range (typically, 701 to the maximum RPM). The gain is applied as a continued offset beginning with the "GAIN MID” value at the “GAIN MID RPM” and ending with the "GAIN HIGH” value at the “GAIN HIGH RPM.” Any operation above this speed is ramped to the GAIN MAX RPM point. 5.
  • Gain Max For pressure delivered vs. DRIVE SPEED MAX velocity
  • the Gain Max attenuates the pressure reference command as the velocity increases/decreases to compensate for system losses.
  • the invention is a method for monitoring and controlling a hydraulic pump driving a metal forging press.
  • a simplified block diagram of a hydraulic press system 110 for example a metal forging press, is shown in Figure 11.
  • the system 110 is powered by an electric motor that drives a hydraulic pump 118. Transient demands for high ram speeds are met by an accumulator system 120.
  • a counter-balance is employed to support and return the main ram 112 to the top of its stroke after the completion of a forging operation.
  • the hydraulic manifold 114 controls the flow of fluid to the main ram cylinder 116 and to the tank 122.
  • the metal forging can be a cylindrical upsetting of, for example, plain carbon steel.
  • the press can be programmed to forge at any constant velocity, for example at 1.27 cm/sec.
  • One embodiment of the invention is an application of an "electronic line-shafting" control technique which serves to replicate and even improve the historical, hydraulic multi-axis coordinated motion control techniques.
  • This technique incorporates a method of servo-driven hydraulic prime-mover control on multi-axis hydraulic applications with the Learn TQ, Redux V, and Redux P compensation factors incorporated for direct feed forward precise hydraulic output without the need for external feedback devices.
  • Redux P relates to the compensation or reduction or compression of a fluid or system capacitance
  • Redux V relates to the restrictive flow of the pump.
  • the invention utilizes an algorithm programmed into the drive control named Pump Torque Learn (abbreviated Learn TQ) that systematically measures and corrects for three key physical parameters of the motor, pump and hydraulic fluid combination. These three factors are accounted for to understand the relationship between applied torque and resultant pump pressure; a relationship that changes over the range of operating speeds of the pump. These parameters are windage torque, viscous torque and coulomb torque, respectively.
  • Pump Torque Learn abbreviated Learn TQ
  • a separate advantage provided by this aspect of the invention is that the resultant precision allows multiple (two or more) drive, motor and pump combinations 125 to be electronically “line-shafted” together while providing precise and stable control of pressure and flow being fed to a common output header 130 regardless of individual pump characteristics or fluid condition variations.
  • a multi-drop set-up for positive displacement hydraulic pumps used in "line- shafting" hydraulic supplies, according to one embodiment of the invention is shown in Figure 14.
  • a further example of a system 150 incorporating the Learn TQ, Redux P, Redux V feed forward compensation algorithm according to one embodiment of the invention is shown in Figure 16.
  • the invention also incorporates development of an empirical understanding of the positive displacement pump in regards to slippage (variation from theoretical displacement) throughout the full pressure/flow delivery range of the pump.
  • This understanding combined with the drive controller's precise measurement of motor rpm gives an extremely precise measurement and control of hydraulic fluid flow rate.
  • knowing the displacement volumes of the cylinder being actuated and mathematically correcting for elasticity of the piping system allows for very precise control and or measurement of press-ram position, and/or ram velocity than may be achieved with prior art.
  • one embodiment of the invention employs the feed forward torque control aspects of the drive system to precisely monitor and/or control hydraulic pressures created by the pump which after mathematical correction for line losses at various flow rates, mimics load at the press ram.
  • the invention therefore provides both a more precise and a more robust method than does prior art.
  • the drive controller may be taught to recognize, report, and/or take action against process anomalies.
  • anomalies would show themselves as velocity (flow rates), current draws and torques (pressures) that are deemed to be outside normal process parameters. Examples include: a) A plugged inlet filter would cause a low current signature combined with a high velocity (motor rpm) than would be expected for the flow and pressure being delivered. b) A burst hydraulic hose would result in an abrupt shift to an abnormally high flow rate. c) Metal being forged that was not within proper metallurgy specifications or a billet not heated to the desired temperature would produce ram speed, displacement and force characteristics that the computer could recognize or simply log as being not within normal boundaries (such as shown in Figures 12 and 13).

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Control Of Electric Motors In General (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

Cette invention se rapporte à un procédé et à un système de surveillance et de contrôle d'un état de pompe hydraulique. Plus précisément, l'invention se rapporte à un procédé et à un dispositif de surveillance et de contrôle indirect d'un processus à commande hydraulique par la surveillance et le contrôle d'un moteur électrique entraînant une pompe hydraulique à déplacement positif. La présente invention se rapporte également à un système de distribution d'énergie hydraulique de précision. Le couplage direct de la pompe à un moteur d'entraînement et à la commande de moteur associée permet une commande de mouvement complète d'une machine à entraînement hydraulique sans l'utilisation d'aucun dispositif en aval. En utilisant des algorithmes de commande de mouvement dans la commande de moteur, la sortie hydraulique au niveau de la tête de pompe est commandée dans un procédé prédictif.
PCT/US2009/035290 2008-02-29 2009-02-26 Procédé et dispositif de surveillance et de contrôle d'un processus à commande hydraulique WO2009111265A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US12/040,444 2008-02-29
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