EP0091018B1 - Position control for a double acting hydraulic motor - Google Patents

Position control for a double acting hydraulic motor Download PDF

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Publication number
EP0091018B1
EP0091018B1 EP83102914A EP83102914A EP0091018B1 EP 0091018 B1 EP0091018 B1 EP 0091018B1 EP 83102914 A EP83102914 A EP 83102914A EP 83102914 A EP83102914 A EP 83102914A EP 0091018 B1 EP0091018 B1 EP 0091018B1
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EP
European Patent Office
Prior art keywords
signal
error signal
valves
inverted
driver circuits
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83102914A
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German (de)
French (fr)
Other versions
EP0091018A1 (en
Inventor
Kenneth Dee Kramer
Edward Horton Fletcher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deere and Co
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Deere and Co
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Publication date
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Priority to AT83102914T priority Critical patent/ATE20690T1/en
Publication of EP0091018A1 publication Critical patent/EP0091018A1/en
Application granted granted Critical
Publication of EP0091018B1 publication Critical patent/EP0091018B1/en
Expired legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
    • F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/006—Hydraulic "Wheatstone bridge" circuits, i.e. with four nodes, P-A-T-B, and on-off or proportional valves in each link
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/03—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type with electrical control means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/30575—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve in a Wheatstone Bridge arrangement (also half bridges)
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • F15B2211/328—Directional control characterised by the type of actuation electrically or electronically with signal modulation, e.g. pulse width modulation [PWM]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6346—Electronic controllers using input signals representing a state of input means, e.g. joystick position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6653—Pressure control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6654—Flow rate control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/665—Methods of control using electronic components
    • F15B2211/6656—Closed loop control, i.e. control using feedback
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/77—Control of direction of movement of the output member
    • F15B2211/7733—Control of direction of movement of the output member providing vibrating movement, e.g. dither control for emptying a bucket
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/77—Control of direction of movement of the output member
    • F15B2211/7741—Control of direction of movement of the output member with floating mode, e.g. using a direct connection between both lines of a double-acting cylinder

Definitions

  • the invention relates to a position control for a double-acting hydraulic motor with the features of the preamble of claim 1.
  • Such a position control is known from Figure 1 on page 5, volume 2 of the contributions to the hydraulic field of the 3rd Aachen Fluid Technology Colloquium (March 14-16, 1978).
  • the control device provided for this purpose provides a feedback of hydraulic and mechanical variables as well as the recording of external control signals in order to generate the usual error signals, via which the pilot valves are controlled.
  • the values fed back into the control device can also include the speed of the movable working member of the hydraulic motor, as well as a signal representing the position of this working member.
  • a position control for hydraulic motors in which a hydraulic bridge circuit is provided, which has a pressure-side and an outlet-side connection and whose diagonal points are connected to a pressure chamber of the piston of the hydraulic motor.
  • the bridge valves in the four branches of the bridge circuit can be controlled hydraulically with the help of two solenoid valves. These are each assigned to a common control pressure line for opposing bridge valves (cf. DD-A-131 870).
  • This known arrangement also has a position actual value sensor and a position target value sensor for the working element of the hydraulic motor.
  • Driver circuits which are controlled via a comparator circuit, are assigned to the electromagnetic valves.
  • each 2-way poppet valve is assigned its own driver circuit, the driver circuits of the two pairs of poppet valves can be controlled particularly reliably and precisely using the different signals specified, so that despite the high flow speed for the hydraulic fluid, no undesirable high pressures and thus instabilities can arise .
  • the target positions can thus be controlled with high accuracy and extremely quickly and flexibly, even with slow mechanical systems.
  • the double-acting cylinder 10 according to FIG. 1 is assigned the valve device 12, via which the cylinder is connected to a pressure medium source (pump 14) and a sump 16.
  • the hydraulic working cylinder is assigned a sensor 18 which reports its position and which can be designed as described in US Pat. No. 3,726,191.
  • the valve device 12 for the two actuators Delivery directions of the hydraulic cylinder 10 comprises a plurality of 2-way seat valves 20a-20d biased by spring 110 and controllable pressure in the closed position. Of these, a seat valve is assigned to the feed line coming from the pressure source 14 and another to the drain line leading to the sump 16 for each actuation direction.
  • the two working chambers of the hydraulic cylinder 10 are designated 11 and 13, respectively.
  • the seat valve 20a lies between the pressure medium source 14 and the working chamber 11, the seat valve 20b between the sump 16 and the working chamber 11, the seat valve 20c between the working chamber 13 and the sump 16 and the seat valve 20d between the pressure medium source 14 and the chamber 13
  • first check valve 22 prevents flow between the working chamber 11 towards the seat valve 20a.
  • a second check valve 24 prevents flow from the working chamber 13 to the seat valve 20d.
  • Pilot valves 100, 102 are assigned to each of the seat valves, each of which has an electromagnetic actuation coil 21a to 21d.
  • the two 2-way seat valve pairs 20a, 20b and 20c, 20d are each directly connected to one of the working chambers 11, 13 of the hydraulic cylinder 10. The arrangement is such that each poppet valve works proportionally.
  • Closing springs 102 are assigned to the pilot valves, which act in the direction of blocking the opening 104. If the opening 104 is exposed, a pressure difference occurs over the channel 106 of the valve body 108. This thus moves against the bias of the spring 110 from its valve seat 112 in proportion to the energy applied to the electromagnetic winding.
  • a control device 30 for controlling the variable preload pressure for the 2-way seat valve pairs is provided. This is associated with the actual position sensor 18 and a setpoint position transmitter 28, a comparator circuit and driver circuits 80a-80d for the electromagnetic coils 21a-21d of the pilot valves 100, 102.
  • the actual position value signal is designated by X in FIG. 2, the desired position value signal by C.
  • the actual value signal of the position of the working member of the hydraulic cylinder is fed to the control device 30 via a isolating amplifier 32 with a unit gain factor.
  • the actual value signal reaches a differentiator 34 and is amplified by the inverter 36 with an amplification factor of approximately -0.6.
  • the signal from the isolating amplifier 32 and the signal from the setpoint position transmitter 28 reach the arithmetic element 38.
  • the error signal E at the output of this element is amplified by the amplifier 40 with an amplification factor of approximately 2.0 and by the inverter 42 (a Reverse amplifier with unit gain factor) reversed.
  • the resulting signal - E arrives at the + input of the arithmetic element 44.
  • At its - input there is a signal from the inverter 36 which represents the speed of the working element of the hydraulic cylinder.
  • the arithmetic element 44 thus supplies an inverted and speed-compensated error signal -E '.
  • This signal is also present at the input of the inverter 46 (reversing amplifier with unit amplification factor), which delivers a non-reversed but speed-compensated error signal + E 'at its output.
  • the two speed-compensated error signals - E 'and E' are fed to the - inputs of the arithmetic elements 48 and 52 or 50 and 54, the outputs of which are each connected to a driver circuit 80a, 80b, 80c, and 80d.
  • Each of these driver circuits is assigned to the electromagnetic coil 21a-21d of one of the pilot valves of the four 2-way seat valve pairs.
  • Each driver circuit 80a can in the feed circuit of the electromagnetic coil a current change of z. B. generate 300 mA. This actuation current is designated Ic. This current change occurs with a voltage change of z. B. 2.5 volts at the output of arithmetic element 44.
  • the circuit of FIG. 2 shows a bistable device controlled by the operator in the form of a switch 56, which is also connected to the negative input of the arithmetic elements 48 to 54.
  • a low output level of the signal of the switch 56 leads to the switching off of all electromagnetic coils, with the result that all seat valves 20a-20d close.
  • the circuit includes another. bistable device controlled by the operator in the form of a switch 58 which is connected to + inputs of the arithmetic elements 48 and 54 or to - inputs of the arithmetic elements 50 and 52.
  • a switch 58 By actuating the switch 58, the seat valves 20a and 20d can be brought to close and the seat valves 20b and 20c can be kept in the open state. As a result, the piston of the hydraulic cylinder 10 comes into a freely floating state.
  • the output of amplifier 40 is connected via resistor R1 to the + input of a comparator 60 and the output of inverter 42 is connected via resistor R2 to the + input of a comparator 62.
  • the inputs of the two comparators are acted upon by the variable signal Vdb from an adjustable device 64 in the form of a setting potentiometer.
  • the output of the comparator 62 is connected to the + input of the comparator 60.
  • a signal of high value is available at the output of the comparator 60, with the exception of the moment when this occurs Error signal E or the reverse error signal - E are within the response value range, the response width is determined by the reference signal Vdb.
  • the output of the comparator 60 is connected via resistor R3 to a voltage source of 8 volts and to the input of an integration device 66, which has a reverse gain factor of -0.3.
  • the integrator 66 changes the output signal between voltage limits in response to abrupt changes in the output of the comparator 60.
  • the integrator 66 performs a reverse operation and provides an inverted reference signal Vdb ', which is normally low unless the error signals E and - E within of the mentioned response value range.
  • the inverted reference signal Vdb ' is present at the + inputs of the arithmetic elements 50, 52 of the driver circuits 80b and 80c, whereby the seat valves 20b and 20c close when the error signals E or - E are in the response value range.
  • a sensor 68 which detects the output pressure of the pressure medium source 14 is provided, the output signal of which is proportional to the output pressure of the pressure medium source.
  • This signal is combined with the inverted reference signal Vdb 'in the arithmetic element 70.
  • the combined signal is present at the + inputs of the arithmetic elements 48, 54 of the driver circuits 80a and 80d. If the output pressure of the pressure medium source 14 decreases, the output signal of the sensor 68 increases, with the result of a proportional reduction in the supply to the electromagnetic coils 21a and 21d. As a result, the seat valves 20a and 20d move in the direction of the closed position. This process increases the pressure drop across these poppet valves, which compensates for the increase in pressure from the pressure source 14 accordingly. When this pressure is reduced, the compensation takes place in the opposite direction.
  • the output signals of the arithmetic elements 48 to 54 serve as input signals for the four driver circuits 80a-80d of the circuit according to FIG. 2.
  • the signals reach the input of an input amplifier 82a-82d, each of which has an amplification factor of approximately 0.8.
  • the amplified input signals each arrive at the negative input of an arithmetic element 84a-84d.
  • an oscillator 72 which generates an oscillation signal of a predetermined frequency.
  • the output of this oscillator is connected on the one hand directly to negative inputs of the arithmetic elements 84b and 84d of the driver circuits 80b and 80d and on the other hand via an inverter 74 to a negative input of the arithmetic elements 84a and 84c of the driver circuits 80a and 80c.
  • the frequency of the vibration signal is 200 Hz and the signal has a triangular waveform.
  • the output signal V3 of the arithmetic elements 84a to 84d is sent to an amplifier 86a to 86d with an amplification factor of approximately 20. Its output signal V4 is sent to a modulator 88a to 88d in which the pulse width of the signal V4 is modulated.
  • An oscillator 76 is connected directly to the modulation devices 88a, 88b of the driver circuits 80a and 80b and via an amplifier 78 to the modulation devices 88c and 88d of the driver circuits 80c and 80d.
  • the oscillator 76 generates a signal with a frequency of 300 Hz and a triangular waveform.
  • the output signal Vc of the modulation devices 88 is a square-wave voltage signal of 3,000 Hz.
  • the result is a duty cycle which is calculated as follows: 100 x ((V4-1.26) / (3.93-1.26)), where 3.93 and 1.26 are the upper and lower peaks of the oscillator 72 signal, respectively.
  • the output signal Vc is supplied to one end of the electromagnetic coils 21a-21d. The other end is grounded through a resistor R4a to R4d and is also connected to the input of a feedback amplifier 90a to 90d. Its output is connected to the input of an integration device 92a to 92d, which applies an output signal V2 to the + input of the associated arithmetic elements 84a to 84d.
  • the amplifier 90a has a gain factor of approximately 2.84.
  • the input signal of the integration device 92 has a value of approximately 3.43 volts.
  • each driver circuit 80a to 80d supplies an actuation current Ic for the electromagnetic coil 21a to 21d which is proportional to the combined signal from the arithmetic element 84 to 84d.
  • the feedback through the amplifier 90 and the integration device 92 reduces the influence of disturbance variables and provides an improved frequency response sensitivity of the control device 30.
  • the direct supply of the oscillation signal of the oscillator 72 on the one hand and the supply via the inverter 74 on the other hand ensures that the outputs of the two driver circuit pairs 80a, 80c on the one hand and 80b, 80d on the other hand are phase-shifted by 180 °. This prevents simultaneous opening of the seat valves 20a and 20b or the seat valves 20d and 20c and prevents a short-circuit flow.
  • the oscillation signal of the oscillator 76 is reversed by the inverter 78. This means that the seat valves 20a, 20b located in front of the inverter 78 and the seat valves 20c, 20d located behind the inverter are alternatively actuated in a pulsed manner. This reduces the peak demand in terms of power supply.
  • the position control works so that a differential pressure drop across the seat valves 20a to 20d occurs, which is inversely proportional to the size of the feed current Ic.
  • the hydraulic pressure medium flow between the working chambers 11 and 13 and the pressure medium source 14 and the sump 16 is controlled accordingly.
  • a positive and not reversed error signal E occurs.
  • the reverse error signal - E is then negative and there is no feed current to the electromagnetic coils 21a and 21c, so that the associated seat valves 20a and 20c remain closed.
  • actuation currents Ic are generated in the driver circuits 80b and 80d by this signal, so that the seat valves 20b and 20d open.
  • the working piston of the hydraulic cylinder 10 is extended to a position that corresponds to the desired position signal C.
  • the setpoint position transmitter 28 is actuated so that the working piston is to be retracted, the reverse error signal becomes positive and the non-inverted error signal becomes negative.
  • the seat valves take on opposite states. The information about the speed of the working piston supplied by the differentiator 34 increases the overall stability of the position control.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Servomotors (AREA)
  • Valve Device For Special Equipments (AREA)
  • Fluid-Driven Valves (AREA)
  • Vehicle Body Suspensions (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Transplanting Machines (AREA)
  • Actuator (AREA)

Abstract

A control system for controlling a double-acting cylinder includes four pilot-operated, proportional-type poppet valves for controlling fluid flow between the cylinder, a pump and a reservoir. Four solenoid-controlled pilot valves operate the poppet valves in response to error signals generated by a control circuit. The control circuit receives a cylinder position feedback signal and an operator-generated command signal. The control circuit provides for float, shutdown, variable deadband and pressure adjustment operation.

Description

Die Erfindung betrifft eine Positionsregelung für einen doppeltwirkenden hydraulischen Motor mit den Merkmalen des Oberbegriffs des Anspruchs 1.The invention relates to a position control for a double-acting hydraulic motor with the features of the preamble of claim 1.

Eine solche Positionsregelung ist bekannt aus Bild 1 auf Seite 5 Band 2 der Beiträge zum Fachgebiet Hydraulik des 3. Aachener fluidtechnischen Kolloquiums (14.-16.3.78). Die dafür vorgesehene Steuereinrichtung sieht eine Rückführung von hydraulischen und mechanischen Größen sowie die Aufnahme von äußeren Steuersignalen vor, um die üblichen Fehlersignale zu erzeugen, über die die Vorsteuerventile gesteuert werden. Zu den in die Steuereinrichtung zurückgeführten Werten kann auch die Geschwindigkeit des beweglichen Arbeitsgliedes des hydraulischen Motors, ebenso wie ein die Stellung dieses Arbeitsgliedes repräsentierendes Signaol gehören.Such a position control is known from Figure 1 on page 5, volume 2 of the contributions to the hydraulic field of the 3rd Aachen Fluid Technology Colloquium (March 14-16, 1978). The control device provided for this purpose provides a feedback of hydraulic and mechanical variables as well as the recording of external control signals in order to generate the usual error signals, via which the pilot valves are controlled. The values fed back into the control device can also include the speed of the movable working member of the hydraulic motor, as well as a signal representing the position of this working member.

Ferner ist eine Positionsregelung für hydraulische Motoren bekannt, bei der eine hydraulische Brückenschaltung vorgesehen ist, die einen druckseitigen und einen Ablaufseitigen Anschluß besitzt und deren Diagonalpunkte mit je einem Druckraum des Kolbens des hydraulischen Motors verbunden sind. Die in den vier Zweigen der Brückenschaltung vorhandenen Brückenventile sind hydraulisch ansteuerbar, und zwar mit Hilfe von zwei Magnetventilen. Diese sind jeweils einer gemeinsamen Steuerdruckleitung für einander gegenüberliegende Brückenventile zugeordnet (vgl. DD-A-131 870). Auch diese bekannte Anordnung weist einen Stellungs-Ist-Wert-Fühler und einen Stellungs-Soll-Wert-Fühler für das Arbeitsglied des hydraulischen Motors auf. Den elektromagnetischen Ventilen sind Treiberkreise zugeordnet, die über einen Komparatorkreis gesteuert werden. Solche Positionsregelungen mit Hilfe von durch Feder und durch steuerbaren Druck in die Schließstellung vorgespannte 2-Wege-SitzVentile besitzen über Positionsregelungen mit Schieberventilen den Vorteil, daß sie wesentlich weniger empfindlich gegenüber Verunreinigungen im hydraulischen Druckmittel sind. Auch ist ein stoßfreier Regelungsbetrieb mit solchen Schieberventilen sehr schwierig insb. dann, wenn der doppelwirkende hydraulische Motor gegen große Lasten arbeiten muß. Dabei tritt zusätzlich das Problem auf, daß eine großen Lasten genügende Anordnung zu träge arbeitet. Diese Nachteile hat eine Positionsregelung mit 2-Wege-Sitzventilen nicht. Allerdings besteht hier die Gefahr, daß bei hohen Strömungsgeschwindigkeiten beim Ein- und Ausschalten der Sitzventile unerwünscht hohe Drücke entstehen. Bei mechanischem System mit hoher Trägheit können Instabilitäten in der Positionsregelung auftreten, so daß die gewünschten Positionen nicht mit der ausreichenden Genauigkeit angefahren werden können.Furthermore, a position control for hydraulic motors is known, in which a hydraulic bridge circuit is provided, which has a pressure-side and an outlet-side connection and whose diagonal points are connected to a pressure chamber of the piston of the hydraulic motor. The bridge valves in the four branches of the bridge circuit can be controlled hydraulically with the help of two solenoid valves. These are each assigned to a common control pressure line for opposing bridge valves (cf. DD-A-131 870). This known arrangement also has a position actual value sensor and a position target value sensor for the working element of the hydraulic motor. Driver circuits, which are controlled via a comparator circuit, are assigned to the electromagnetic valves. Such position controls with the aid of spring-loaded and controllable pressure in the closed position biased two-way valves have over position controls with slide valves the advantage that they are much less sensitive to contamination in the hydraulic pressure medium. Bumpless control operation with such slide valves is also very difficult, especially when the double-acting hydraulic motor has to work against large loads. In addition, there is the problem that a large enough arrangement works too sluggishly. Position control with 2-way seat valves does not have these disadvantages. However, there is a risk here that undesirably high pressures occur when the seat valves are switched on and off at high flow speeds. In the case of a mechanical system with high inertia, instabilities can occur in the position control, so that the desired positions cannot be approached with sufficient accuracy.

Es ist Aufgabe der Erfindung die Positionsregelung mit den Merkmalen des Oberbegriffs des Anspruchs 1 so weiterzubilden, daß auch bei hohen Strömungsgeschwindigkeiten des hydraulischen Fluids und hoher Trägheit der bewegten Massen ein instabiles Verhalten der Positionsregelung ausgeschlossen und so eine besonders hohe Regelungsgenauigkeit erzielt wird, so daß die Regelung auch für einen geschlossenen Strömungsmittelkreislauf mit außerordentlich flexiblen Funktionen geeignet ist.It is an object of the invention to improve the position control with the features of the preamble of claim 1 so that an unstable behavior of the position control is excluded even at high flow velocities of the hydraulic fluid and high inertia of the moving masses, and a particularly high control accuracy is achieved so that the Regulation is also suitable for a closed fluid circuit with extremely flexible functions.

Diese Aufgabe wird durch die Maßnahmen des Anspruchs 1 gelöst. Da jedem 2-Wege-Sitzventil ein eigener Treiberkreis zugeordnet ist, lassen sich die Treiberkreise der beiden Sitzventil-Paare über die angegebenen unterschiedlichen Signale besonders zuverlässig und exakt ansteuern, so daß trotz hoher Strömungsgeschwindigkeit für das Hydraulikfluid keine unerwünscht hohen Drücke und damit Instabilitäten entstehen können. Die Soll-Positionen lassen sich damit auch bei trägen mechanischen Systemen mit hoher Genauigkeit und außerordentlich rasch und flexibel ansteuern.This object is achieved by the measures of claim 1. Since each 2-way poppet valve is assigned its own driver circuit, the driver circuits of the two pairs of poppet valves can be controlled particularly reliably and precisely using the different signals specified, so that despite the high flow speed for the hydraulic fluid, no undesirable high pressures and thus instabilities can arise . The target positions can thus be controlled with high accuracy and extremely quickly and flexibly, even with slow mechanical systems.

Das Auftreten von Strömungskurzschlüssen innerhalb des Systems wird durch die weiteren Maßnahmen nach Anspruch 2 zuverlässig ausgeschaltet. Eine weitere Steigerung der Regelungsgenauigkeit und eine völlig stoßfreie Ansteuerung der gewünschten Positionen läßt sich durch die Maßnahmen nach Anspruch 3 erreichen. Insbesondere läßt sich durch die Modulierung erreichen, daß die Treiberkreispaare nicht gleichzeitig, sondern nacheinander angesteuert werden (Anspruch 4). Hierdurch wird zuverlässig ein gleichzeitiges Öffnen von Sitzventilen, die unterschiedlichen Sitzventil-Paaren zugeordnet sind, vermieden. Dadurch vereinfacht sich auch die erforderliche Druckregelung. Durch das phasenverschobene Arbeiten der Treiberkreispaare wird außerdem der Spitzenbedarf für die Kraftzuspeisung verringert. Einzelheiten hierzu enthält der Anspruch 5.The occurrence of flow short circuits within the system is reliably eliminated by the further measures according to claim 2. A further increase in control accuracy and a completely bumpless control of the desired positions can be achieved by the measures according to claim 3. In particular, it can be achieved by the modulation that the driver circuit pairs are not controlled simultaneously, but in succession (claim 4). This reliably prevents simultaneous opening of seat valves that are assigned to different pairs of seat valves. This also simplifies the pressure control required. The phase shifted operation of the driver circuit pairs also reduces the peak demand for the power supply. Details of this are contained in claim 5.

Maßnahmen zur weiteren Beeinflussung von außen der jeweiligen korrigierten Fehlersignale beinhalten die Ansprüche 6 bis 10.Measures for further influencing from the outside of the respective corrected error signals are contained in claims 6 to 10.

Die Erfindung wird nachfolgend anhand schematischer Zeichnungen an einem Ausführungsbeispiel näher erläutert.The invention is explained in more detail below with the aid of schematic drawings using an exemplary embodiment.

Es zeigen :

  • Figur 1 ein vereinfachtes schematisches Diagramm der Positionsregelung gemäß der Erfindung und
  • Figur 2 ein schematisches Schaltblockdiagramm der zugehörigen Steuereinrichtung.
Show it :
  • Figure 1 is a simplified schematic diagram of the position control according to the invention and
  • Figure 2 is a schematic circuit block diagram of the associated control device.

Dem doppeltwirkenden Zylinder 10 nach Fig. 1 ist die Ventileinrichtung 12 zugeordnet, über die der Zylinder mit einer Druckmittelquelle (Pumpe 14) und einem Sumpf 16 verbunden ist. Dem hydraulischen Arbeitszylinder ist ein seine Position rückmeldender Fühler 18 zugeordnet, der gemäß den Angaben in der US-A-3 726 191 ausgebildet sein kann.The double-acting cylinder 10 according to FIG. 1 is assigned the valve device 12, via which the cylinder is connected to a pressure medium source (pump 14) and a sump 16. The hydraulic working cylinder is assigned a sensor 18 which reports its position and which can be designed as described in US Pat. No. 3,726,191.

Die Ventileinrichtung 12 für die beiden Betätigungs-Richtungen des Hydraulikzylinders 10 umfaßt mehrere durch Feder 110 und steuerbaren Druck in die Schließs.tellung vorgespannte 2-Wege-Sitz-Ventile 20a-20d. Von diesen sind für jede Betätigungsrichtung jeweils ein Sitzventil der von der Druckquelle 14 kommenden Speiseleitung und ein anderes der zum Sumpf 16 führenden Ablaufleitung zugeordnet. Die beiden Arbeitskammern des hydraulischen Zylinders 10 sind mit 11 bzw. 13 bezeichnet. Das Sitzventil 20a liegt zwischen der Druckmittelquelle 14 und der Arbeitskammer 11, das Sitzventil 20b zwischen dem Sumpf 16 und der Arbeitskammer 11, das Sitzventil 20c zwischen der Arbeitskammer 13 und dem Sumpf 16 und das Sitzventil 20d zwischen der Druckmittelquelle 14 und der Kammer 13. Ein erstes Rückschlagventil 22 verhindert eine Strömung zwischen der Arbeitskammer 11 in Richtung auf das Sitzventil 20a. Ein zweites Rückschlagventil 24 verhindert eine Strömung von der Arbeitskammer 13 zu dem Sitzventil 20d.The valve device 12 for the two actuators Delivery directions of the hydraulic cylinder 10 comprises a plurality of 2-way seat valves 20a-20d biased by spring 110 and controllable pressure in the closed position. Of these, a seat valve is assigned to the feed line coming from the pressure source 14 and another to the drain line leading to the sump 16 for each actuation direction. The two working chambers of the hydraulic cylinder 10 are designated 11 and 13, respectively. The seat valve 20a lies between the pressure medium source 14 and the working chamber 11, the seat valve 20b between the sump 16 and the working chamber 11, the seat valve 20c between the working chamber 13 and the sump 16 and the seat valve 20d between the pressure medium source 14 and the chamber 13 first check valve 22 prevents flow between the working chamber 11 towards the seat valve 20a. A second check valve 24 prevents flow from the working chamber 13 to the seat valve 20d.

Jedem der Sitzventile sind Vorsteuerventile 100, 102 zugeordnet, die jeweils eine elektromagnetische Betätigungsspule 21a bis 21d aufweisen. Die beiden 2-Wege-Sitzventil-Paare 20a, 20b bzw. 20c, 20d sind jeweils direkt mit einer der Arbeitskammern 11, 13 des hydraulischen Zylinders 10 verbunden. Die Anordnung ist so getroffen, daß jedes Sitzventil eine proportionale Arbeitsweise zeigt. Den Vorsteuerventilen sind Schließfedern 102 zugeordnet, welche in Richtung auf ein Sperren der Öffnung 104 wirksam sind. Wird die Öffnung 104 freigelegt tritt über dem Kanal 106 des Ventilkörpers 108 eine Druckdifferenz auf. Dieser verschiebt sich somit gegen die Vorspannung der Feder 110 von seinem Ventilsitz 112 und zwar proportional der an der elektromagnetischen Wicklung angelegten Energie.Pilot valves 100, 102 are assigned to each of the seat valves, each of which has an electromagnetic actuation coil 21a to 21d. The two 2-way seat valve pairs 20a, 20b and 20c, 20d are each directly connected to one of the working chambers 11, 13 of the hydraulic cylinder 10. The arrangement is such that each poppet valve works proportionally. Closing springs 102 are assigned to the pilot valves, which act in the direction of blocking the opening 104. If the opening 104 is exposed, a pressure difference occurs over the channel 106 of the valve body 108. This thus moves against the bias of the spring 110 from its valve seat 112 in proportion to the energy applied to the electromagnetic winding.

Weiterhin ist eine Steuereinrichtung 30 zur Steuerung des veränderbaren Vorspanndruckes für die 2-Wege-Sitz-Ventil-Paare vorgesehen. Dieser ist der Ist-Stellungsfühler 18 sowie ein Soll-Wert-Stellungsgeber 28, ein Komparatorkreis sowie Treiberkreise 80a-80d für die elektromagnetischen Spulen 21a-21d der Vorsteuerventile 100, 102 zugeordnet. Das Stellungs-Ist-Wert-Signal ist in Fig. 2 mit X, das Stellungs-Soll-Wert-Signal mit C bezeichnet. Das Ist-Wert-Signal der Stellung des Arbeitsgliedes des hydraulischen Zylinders wird der Steuereinrichtung 30 über einen Trennverstärker 32 mit Einheitsverstärkungsfaktor zugeführt. Das Ist-Wert-Signal gelangt zu einem Differentiator 34 und wird durch den Inverter 36 mit einem Verstärkungsfaktor von etwa -0,6 verstärkt. Das Signal vom Trennverstärker 32 und das Signal vom Soll-Wert-Stellungsgeber 28 gelangen zu dem arithmetischen Glied 38. Das Fehlersignal E am Ausgang dieses Gliedes wird von dem Verstärker 40 mit einem Verstärkungsfaktor von annähernd 2,0 verstärkt und durch den Inverter 42 (ein Umkehrverstärker mit Einheitsverstärkungsfaktor) umgekehrt. Das entstehende Signal - E gelangt zu dem + Eingang des arithmetischen Gliedes 44. An dessen - Eingang liegt ein die Geschwindigkeit des Arbeitsgliedes des hydraulischen Zylinders wiedergebendes Signal vom dem Inverter 36 an. Das arithmetische Glied 44 liefert somit ein umgekehrtes und geschwindigkeitskompensiertes Fehlersignal -E'. Dieses Signal liegt auch am Eingang des Inverters 46 (Umkehrverstärker mit Einheitsverstärkungsfaktor) an, der an seinem Ausgang ein nicht umgekehrtes aber geschwindigkeitskompensiertes Fehlersignal + E' liefert.Furthermore, a control device 30 for controlling the variable preload pressure for the 2-way seat valve pairs is provided. This is associated with the actual position sensor 18 and a setpoint position transmitter 28, a comparator circuit and driver circuits 80a-80d for the electromagnetic coils 21a-21d of the pilot valves 100, 102. The actual position value signal is designated by X in FIG. 2, the desired position value signal by C. The actual value signal of the position of the working member of the hydraulic cylinder is fed to the control device 30 via a isolating amplifier 32 with a unit gain factor. The actual value signal reaches a differentiator 34 and is amplified by the inverter 36 with an amplification factor of approximately -0.6. The signal from the isolating amplifier 32 and the signal from the setpoint position transmitter 28 reach the arithmetic element 38. The error signal E at the output of this element is amplified by the amplifier 40 with an amplification factor of approximately 2.0 and by the inverter 42 (a Reverse amplifier with unit gain factor) reversed. The resulting signal - E arrives at the + input of the arithmetic element 44. At its - input there is a signal from the inverter 36 which represents the speed of the working element of the hydraulic cylinder. The arithmetic element 44 thus supplies an inverted and speed-compensated error signal -E '. This signal is also present at the input of the inverter 46 (reversing amplifier with unit amplification factor), which delivers a non-reversed but speed-compensated error signal + E 'at its output.

Die beiden geschwindigkeitskompensierten Fehlersignale - E' bzw. E' werden jeweils den -Eingängen der arithmetischen Glieder 48 und 52 bzw. 50 und 54 zugeführt, deren Ausgänge jeweils mit einem Treiberkreis 80a, 80b, 80c, und 80d verbunden sind. Jeder dieser Treiberkreise ist der elektromagnetischen Spule 21a-21d eines der Vorsteuerventile der vier 2-Wege-Sitzventil-Paare zugeordnet. Jeder Treiberkreis 80a kann im Speisekreis der elektromagnetischen Spule eine Stromänderung von z. B. 300 mA erzeugen. Dieser Betätigungsstrom ist mit Ic bezeichnet. Diese Stromänderung tritt auf bei einer Spannungsänderung von z. B. 2,5 Volt am Ausgang des arithmetischen Gliedes 44. Es ist ersichtlich, daß das geschwindigkeitskompensierte Fehlersignal - E' den arithmetischen Gliedern 48 und 52 der Treiberkreise 80a und 80c und das geschwindigkeitskompensierte Fehlersignal + E' den arithmetischen Gliedern 50 und 54 der Treiberkreise 80b und 80d zugeführt wird.The two speed-compensated error signals - E 'and E' are fed to the - inputs of the arithmetic elements 48 and 52 or 50 and 54, the outputs of which are each connected to a driver circuit 80a, 80b, 80c, and 80d. Each of these driver circuits is assigned to the electromagnetic coil 21a-21d of one of the pilot valves of the four 2-way seat valve pairs. Each driver circuit 80a can in the feed circuit of the electromagnetic coil a current change of z. B. generate 300 mA. This actuation current is designated Ic. This current change occurs with a voltage change of z. B. 2.5 volts at the output of arithmetic element 44. It can be seen that the speed-compensated error signal - E 'the arithmetic elements 48 and 52 of the driver circuits 80a and 80c and the speed-compensated error signal + E' the arithmetic elements 50 and 54 of the driver circuits 80b and 80d is supplied.

Die Schaltung nach Fig. 2 zeigt eine durch die Bedienungsperson gesteuerte bistabile Einrichtung in Form eines Schalters 56, der ebenfalls mit dem negativen Eingang der arithmetischen Glieder 48 bis 54 verbunden ist. Ein niedriges Ausgangsniveau des Signals des Schalters 56 führt zur Abschaltung aller elektromagnetischen Spulen mit der Folge, daß alle Sitzventile 20a-20d schließen.The circuit of FIG. 2 shows a bistable device controlled by the operator in the form of a switch 56, which is also connected to the negative input of the arithmetic elements 48 to 54. A low output level of the signal of the switch 56 leads to the switching off of all electromagnetic coils, with the result that all seat valves 20a-20d close.

Die Schaltung umfaßt eine weitere. durch die Bedienungsperson gesteuerte bistabile Einrichtung in Form eines Schalters 58, der an + Eingänge der arithmetischen Glieder 48 und 54 bzw. an - Eingänge der arithmetischen Glieder 50 und 52 angeschlossen ist. Durch Betätigung des Schalters 58 können die Sitzventile 20a und 20d zum Schließen gebracht und die Sitzventile 20b und 20c im offenen Zustand gehalten werden. Hierdurch gelangt der Kolben des hydraulischen Zylinders 10 in einen frei schwimmenden Zustand.The circuit includes another. bistable device controlled by the operator in the form of a switch 58 which is connected to + inputs of the arithmetic elements 48 and 54 or to - inputs of the arithmetic elements 50 and 52. By actuating the switch 58, the seat valves 20a and 20d can be brought to close and the seat valves 20b and 20c can be kept in the open state. As a result, the piston of the hydraulic cylinder 10 comes into a freely floating state.

Der Ausgang des Verstärkers 40 ist über Widerstand R1 mit dem + Eingang eines Komparators 60 und der Ausgang des Inverters 42 über Widerstand R2 mit dem + Eingang eines Komparators 62 verbunden. Die - Eingänge der beiden Komparatoren werden durch das variable Signal Vdb einer einstellbaren Einrichtung 64 in Form eines Stellpotentiometers beaufschlagt. Ferner ist der Ausgang des Komparators 62 mit dem + Eingang des Komparators 60 verbunden.The output of amplifier 40 is connected via resistor R1 to the + input of a comparator 60 and the output of inverter 42 is connected via resistor R2 to the + input of a comparator 62. The inputs of the two comparators are acted upon by the variable signal Vdb from an adjustable device 64 in the form of a setting potentiometer. Furthermore, the output of the comparator 62 is connected to the + input of the comparator 60.

Am Ausgang des Komparators 60 steht ein Signal von hohem Wert zur Verfügung mit Ausnahme des Augenblickes, an dem sich das Fehlersignal E oder das umgekehrte Fehlersignal - E innerhalb des Ansprechwertbereiches befinden, dessen Ansprechbreite durch das Bezugssignal Vdb bestimmt wird. Ferner ist der Ausgang des Komparators 60 über Widerstand R3 mit einer Spannungsquelle von 8 Volt verbunden sowie mit dem Eingang einer Integrationseinrichtung 66, die einen Umkehrverstärkungsfaktor von -0,3 aufweist. Die Integrationseinrichtung 66 verändert das Ausgangssignal zwischen Spannungsgrenzen in Abhängigkeit von abrupten Änderungen des Ausgangssignals des Komparators 60. Außerdem führt die Integrationseinrichtung 66 eine Umkehroperation aus und liefert ein umgekehrtes Bezugssignal Vdb', das normalerweise einen niedrigen Wert aufweist sofern nicht die Fehlersignale E und - E innerhalb des erwähnten Ansprechwertbereiches liegen. Das umgekehrte Bezugssignal Vdb' liegt an den + Eingängen der arithmetischen Glieder 50, 52 der Treiberkreise 80b und 80c an wodurch die Sitzventile 20b und 20c schließen wenn sich die Fehlersignale E oder - E in dem Ansprechwertbereich befinden.A signal of high value is available at the output of the comparator 60, with the exception of the moment when this occurs Error signal E or the reverse error signal - E are within the response value range, the response width is determined by the reference signal Vdb. Furthermore, the output of the comparator 60 is connected via resistor R3 to a voltage source of 8 volts and to the input of an integration device 66, which has a reverse gain factor of -0.3. The integrator 66 changes the output signal between voltage limits in response to abrupt changes in the output of the comparator 60. In addition, the integrator 66 performs a reverse operation and provides an inverted reference signal Vdb ', which is normally low unless the error signals E and - E within of the mentioned response value range. The inverted reference signal Vdb 'is present at the + inputs of the arithmetic elements 50, 52 of the driver circuits 80b and 80c, whereby the seat valves 20b and 20c close when the error signals E or - E are in the response value range.

Ferner ist in der dargestellten Schaltung nach Fig. 2 ein den Ausgangsdruck der Druckmittelquelle 14 erfassender Fühler 68 vorgesehen dessen Ausgangssignal proportional dem Ausgangsdruck der Druckmittelquelle ist. Dieses Signal wird mit dem umgekehrten Bezugssignal Vdb' in dem arithmetischen Glied 70 kombiniert. Das kombinierte Signal liegt an den + Eingängen der arithmetischen Glieder 48, 54 der Treiberkreise 80a und 80d an. Nimmt der Ausgangsdruck der Druckmittelquelle 14 ab steigt das Ausgangssignal des Fühlers 68 mit der Folge einer proportionalen Verringerung der Speisung an den elektromagnetischen Spulen 21a und 21d. Dadurch bewegen sich die Sitzventile 20a und 20d in Richtung auf die Schließstellung. Durch diesen Vorgang wird der Druckabfall über diese Sitzventile vergrößert, wodurch die Zunahme des Druckes von der Druckquelle 14 entsprechend kompensiert wird. Bei Abnahme dieses Druckes erfolgt die Kompensation in umgekehrter Richtung.Furthermore, in the circuit shown in FIG. 2, a sensor 68 which detects the output pressure of the pressure medium source 14 is provided, the output signal of which is proportional to the output pressure of the pressure medium source. This signal is combined with the inverted reference signal Vdb 'in the arithmetic element 70. The combined signal is present at the + inputs of the arithmetic elements 48, 54 of the driver circuits 80a and 80d. If the output pressure of the pressure medium source 14 decreases, the output signal of the sensor 68 increases, with the result of a proportional reduction in the supply to the electromagnetic coils 21a and 21d. As a result, the seat valves 20a and 20d move in the direction of the closed position. This process increases the pressure drop across these poppet valves, which compensates for the increase in pressure from the pressure source 14 accordingly. When this pressure is reduced, the compensation takes place in the opposite direction.

Die Ausgangssignale der arithmetischen Glieder 48 bis 54 dienen als Eingangssignale für die vier Treiberkreise 80a-80d der Schaltung nach Fig. 2. Die Signale gelangen an den Eingang eines Eingangsverstärkers 82a-82d, die jeweils einen Verstärkungsfaktor von etwa 0,8 aufweisen. Die verstärkten Eingangssignale gelangen jeweils zu dem negativen Eingang eines arithmetischen Gliedes 84a-84d.The output signals of the arithmetic elements 48 to 54 serve as input signals for the four driver circuits 80a-80d of the circuit according to FIG. 2. The signals reach the input of an input amplifier 82a-82d, each of which has an amplification factor of approximately 0.8. The amplified input signals each arrive at the negative input of an arithmetic element 84a-84d.

Gemäß Fig. 2 ist ein Oszilator 72 vorgesehen, der ein Schwingungssignal von vorbestimmter Frequenz erzeugt. Der Ausgang dieses Oszilators ist einerseits direkt mit negativen Eingängen der arithmetischen Glieder 84b und 84d der Treiberkreise 80b und 80d und andererseits über einen Inverter 74 mit einem negativen Eingang der arithmetischen Glieder 84a und 84c der Treiberkreise 80a und 80c verbunden. Die Frequenz des Schwingungssignals beträgt 200 Hz und das Signal weist eine dreieckige Wellenform auf.2, an oscillator 72 is provided which generates an oscillation signal of a predetermined frequency. The output of this oscillator is connected on the one hand directly to negative inputs of the arithmetic elements 84b and 84d of the driver circuits 80b and 80d and on the other hand via an inverter 74 to a negative input of the arithmetic elements 84a and 84c of the driver circuits 80a and 80c. The frequency of the vibration signal is 200 Hz and the signal has a triangular waveform.

Das Ausgangssignal V3 der arithmetischen Glieder 84a bis 84d gelangt jeweils an einen Verstärker 86a bis 86d mit einem Verstärkungsfaktor von etwa 20. Dessen Ausgangssignal V4 gelangt zu einem Modulator 88a bis 88d in dem die Impulsweite des Signals V4 moduliert wird. Ein Oszilator 76 ist direkt mit den Modulationseinrichtungen 88a, 88b der Treiberkreise 80a und 80b und über einen Verstärker 78 mit den Modulationseinrichtungen 88c und 88d der Treiberkreise 80c und 80d verbunden. Der Oszilator 76 erzeugt ein Signal mit einer Frequenz von 300 Hz und einer dreieckigen Wellenform. Das Ausgangssignal Vc der Modulationseinrichtungen 88 ist ein Rechteckspannungssignal von 3 000 Hz. Die Folge ist ein Arbeitszyklus, der sich wie folgt berechnet : 100 x ((V4-1,26)/(3,93-1.26)), worin 3,93 und 1,26 jeweils die oberen und unteren Spitzenwerte des Signals des Oszilators 72 sind. Das Ausgangssignal Vc wird einem Ende der elektromagnetischen Spulen 21a-21d zugeführt. Das andere Ende ist jeweils durch einen Widerstand R4a bis R4d geerdet und außerdem mit dem Eingang eines Rückkoppelungsverstärkers 90a bis 90d verbunden. Dessen Ausgang ist mit dem Eingang einer Integrationseinrichtung 92a bis 92d verbunden, die ein Ausgangssignal V2 an den + Eingang der zugehörigen arithmetischen Glieder 84a bis 84d legt. Der Verstärker 90a weist einen Verstärkungsfaktor von etwa 2,84 auf. Das Eingangssignal der Integrationseinrichtung 92 weist einen Wert von etwa 3,43 Volt auf. Das Ausgangssignal V2 bestimmt sich nach der LaPiace-Transformationsgieichung V2 = 2Vref - Vl (6250/(S + 6250)), in der V1 die Spannung am Eingang des Verstärkers 90 ist.The output signal V3 of the arithmetic elements 84a to 84d is sent to an amplifier 86a to 86d with an amplification factor of approximately 20. Its output signal V4 is sent to a modulator 88a to 88d in which the pulse width of the signal V4 is modulated. An oscillator 76 is connected directly to the modulation devices 88a, 88b of the driver circuits 80a and 80b and via an amplifier 78 to the modulation devices 88c and 88d of the driver circuits 80c and 80d. The oscillator 76 generates a signal with a frequency of 300 Hz and a triangular waveform. The output signal Vc of the modulation devices 88 is a square-wave voltage signal of 3,000 Hz. The result is a duty cycle which is calculated as follows: 100 x ((V4-1.26) / (3.93-1.26)), where 3.93 and 1.26 are the upper and lower peaks of the oscillator 72 signal, respectively. The output signal Vc is supplied to one end of the electromagnetic coils 21a-21d. The other end is grounded through a resistor R4a to R4d and is also connected to the input of a feedback amplifier 90a to 90d. Its output is connected to the input of an integration device 92a to 92d, which applies an output signal V2 to the + input of the associated arithmetic elements 84a to 84d. The amplifier 90a has a gain factor of approximately 2.84. The input signal of the integration device 92 has a value of approximately 3.43 volts. The output signal V2 is determined according to the LaPiace transformation equation V2 = 2Vref - Vl (6250 / (S + 6250)), in which V1 is the voltage at the input of the amplifier 90.

Auf diese Weise liefert jeder Treiberkreis 80a bis 80d einen Betätigungsstrom Ic für die elektromagnetische Spule 21a bis 21d, der dem kombinierten Signal aus dem arithmetischen Glied 84 bis 84d proportional ist. Die Rückführung durch den Verstärker 90 und die Integrationseinrichtung 92 vermindert den Einfluß von Störgrößen und liefert eine verbesserte Frequenzansprechempfindlichkeit der Steuereinrichtung 30.In this way, each driver circuit 80a to 80d supplies an actuation current Ic for the electromagnetic coil 21a to 21d which is proportional to the combined signal from the arithmetic element 84 to 84d. The feedback through the amplifier 90 and the integration device 92 reduces the influence of disturbance variables and provides an improved frequency response sensitivity of the control device 30.

Durch die direkte Zuführung des Schwingungssignals des Oszilators 72 einerseits und durch die Zuführung über den Inverter 74 andererseits wird erreicht, daß die Ausgänge der beiden Treiberkreispaare 80a, 80c einerseits und 80b, 80d andererseits um 180° phasenverschoben sind. Dadurch wird ein gleichzeitiges Öffnen der Sitzventile 20a und 20b bzw. der Sitzventile 20d und 20c verhindert und eine Kurzschlußströmung ausgeschlossen. Das Schwingungssignal des Oszilators 76 wird durch den Inverter 78 umgekehrt. Das bedeutet, daß die vor dem Inverter 78 liegenden Sitzventile 20a, 20b und die hinter dem Inverter liegenden Sitzventile 20c, 20d alternativ impulsartig betätigt werden. Dadurch wird der Spitzenbedarf bezüglich der Kraftzuspeisung verringert.The direct supply of the oscillation signal of the oscillator 72 on the one hand and the supply via the inverter 74 on the other hand ensures that the outputs of the two driver circuit pairs 80a, 80c on the one hand and 80b, 80d on the other hand are phase-shifted by 180 °. This prevents simultaneous opening of the seat valves 20a and 20b or the seat valves 20d and 20c and prevents a short-circuit flow. The oscillation signal of the oscillator 76 is reversed by the inverter 78. This means that the seat valves 20a, 20b located in front of the inverter 78 and the seat valves 20c, 20d located behind the inverter are alternatively actuated in a pulsed manner. This reduces the peak demand in terms of power supply.

Die Positionsregelung arbeitet so, daß ein Differentialdruckabfall an den Sitzventilen 20a bis 20d auftritt, der umgekehrt proportional der Größe des Speisestroms Ic ist. Entsprechend wird der hydraulische Druckmittelstrom zwischen den Arbeitskammern 11 und 13 und der Druckmittelquelle 14 und dem Sumpf 16 gesteuert.The position control works so that a differential pressure drop across the seat valves 20a to 20d occurs, which is inversely proportional to the size of the feed current Ic. The hydraulic pressure medium flow between the working chambers 11 and 13 and the pressure medium source 14 and the sump 16 is controlled accordingly.

Wird der Soll-Wert-Stellungsgeber 28 betätigt, tritt ein positives und nicht umgekehrtes Fehlersignal E auf. Das umgekehrte Fehlersignal - E ist dann negativ und an den elektromagnetischen Spulen 21a und 21c liegt kein Speisestrom an, so daß die zugehörigen Sitzventile 20a und 20c geschlossen bleiben. In den Treiberkreisen 80b und 80d werden dagegen durch dieses Signal Betätigungsströme Ic erzeugt, so daß die Sitzventile 20b und 20d öffnen. Damit wird der Arbeitskolben des hydraulischen Zylinders 10 ausgefahren und zwar bis in eine Stellung die dem Stellungs-Soll-Signal C entspricht. Wird der Soll-Wert-Stellungsgeber 28 so betätigt, daß der Arbeitskolben eingefahren werden soll, wird das umgekehrte Fehlersignal positiv und das nicht umgekehrte Fehlersignal negativ. Die Sitzventile nehmen damit entgegengesetzte Zustände ein. Die durch den Differentiator 34 zugeführte Information über die Geschwindigkeit des Arbeitskolbens verstärkt die Gesamtstabilität der Positionsregelung.If the setpoint position transmitter 28 is actuated, a positive and not reversed error signal E occurs. The reverse error signal - E is then negative and there is no feed current to the electromagnetic coils 21a and 21c, so that the associated seat valves 20a and 20c remain closed. In contrast, actuation currents Ic are generated in the driver circuits 80b and 80d by this signal, so that the seat valves 20b and 20d open. In this way, the working piston of the hydraulic cylinder 10 is extended to a position that corresponds to the desired position signal C. If the setpoint position transmitter 28 is actuated so that the working piston is to be retracted, the reverse error signal becomes positive and the non-inverted error signal becomes negative. The seat valves take on opposite states. The information about the speed of the working piston supplied by the differentiator 34 increases the overall stability of the position control.

Claims (10)

1. A positional control for a double-acting hydraulic motor (10) which is connected by way of a valve arrangement (12) to a hydraulic pressure source (14) and a tank (16), wherein the valve arrangement (12), for each of the two directions of actuation of the motor (10) respectively, has two 2-way seat valves (20a, 20b and 20c, 20d respectively) which are biased into the closing position by means of a spring (110) and a controllable pressure, a respective one of each said two valves being associated with the supply line coming from the pressure source (14) and the other being associated with the discharge line going to the tank (16), and wherein a control means (30) is provided for controlling the variable biasing pressure for the pairs of 2-way seat valves, which means has an actual position sensor (18) and a reference position value generator (18), a comparator circuit and driver circuits (80a-80d) for the electromagnetic coils (21a-21d) of pilot control valves (100, 102), the two pairs of 2- way seat valves (20a, 20b and 20c, 20d) being respectively connected directly to one of the working chambers (11, 13) of the hydraulic motor (10), characterised in that an independently operating driver circuit (80a-80d) is associated with each of the four pilot control valves (100, 102) each associated with a respective 2-way seat valve (20a-20d), that there is provided an arithmetic means (38) which supplies an error signal (E) reproducing the difference between a position actual value (X) and a position reference value (C) of the movable working member of the hydraulic motor (10), that an inverter (42) which is supplied with the error signal delivers an error signal (- E) which is inverted in sign, that a differentiator (34) and an inverter (36) deliver a speed signal which is inverted in sign and which reproduces the speed of the movable working member of the hydraulic motor (10), that an arithmetic means (44) delivers a speed-compensated error signal (- E') which is inverted in sign and which reproduces a difference between the inverted error signal (-E) and the inverted speed signal, that an inverter (46) delivers a speed-compensated error signal (+ E') and that the inverted speed-compensated error signal (- E') actuates the driver circuit (80a) of the 2-way seat valve (20a) of the one pair (20a, 20b), which is associated with the feed line, and the driver circuit (80c) of the 2- way seat valve (20c) of the other pair (20c, 20d), which is associated with the discharge line, while the speed-compensated error signal (+ E') is fed to the driver circuits (80b, 80d) of the other two 2- way seat valves (20b, 20d).
2. A positional control according to claim 1 characterised in that disposed between each working chamber (11, 13) and the 2-way seat valve (20a, 20d) of each pair, which is connected to the feed line, is a respective check valve (22 and 24 respectively) which opens only in a direction towards the working chamber.
3. A positional control according to claim 1 characterised in that each driver circuit (80a to 80d) has a modulation means (88a-88d) for conversion of the applied speed-compensated error signal (- E', + E') into an output signal which is modulated in respect of its pulse width and whose duty cycle corresponds to the magnitude of the applied error signal.
4. A positional control according to claim 3 characterised in that an inverted oscillation signal is supplied to two (80a, 80c) of the driver circuits (80a-80d) and an oscillation signal without inversion is supplied to the other two driver circuits (80b, 80d), whereby the outputs of the two pairs of driver circuits (80a, 80c and 80b, 80d) are phase- shifted through 180°.
5. A positional control according to claim 4 characterised in that an oscillator (72) is provided for generating an oscillation signal of predetermined frequency, the output thereof being connected on the one hand directly to arithmetic means (84b, 84d) of the driver circuits (80b, 80d) for the 2-way seat valves (20b, 20d) associated with the discharge line, and on the other hand by way of an inverter (74) to arithmetic means (84a, 84c) which belong to the driver circuits (80a, 80c) for the 2-way seat valves (20a, 20c) associated with the feed line.
6. A positional control according to claim 1 characterised in that connected to the input side of each driver circuit (80a-80d) is an arithmetic means (48-50) to which the respective speed-compensated error signals (- E', + E') are applied and to which further signals for varying the respective error signals can be applied independently of each other.
7. A positional control according to claim 6 characterised in that a means (64) which can be adjusted by an operator is provided for generating a variable response threshold reference signal which with the error signal (+ E) and the error signal (- E) with inverted sign can be supplied to a comparator means (60, 62) whose output signal can be supplied by way of an integration means (66) to the arithmetic means (50, 52) of the driver circuits for those 2-way seat valves (20b, 20c) which are associated with the discharge line in order to close same when the error signal or the error signal with inverted sign respectively are within the adjustable response threshold value range.
8. A positional control according to claim 7 characterised in that the comparator means comprises two comparators (60, 62) with bistable output, a respective input of each thereof being connected to the adjustable means (64) for the response threshold reference signal and the respective other input of each thereof receiving respectively the error signal with inverted sign (- E) and the error signal (E) together with the output signal of the other comparator (62).
9. A positional control according to claim 7 characterised in that there is provided a sensor (68) which detects the pressure in the feed line and whose pressure sensor signal together with the output signal of the integration means (66) can be fed to the arithmetic means (48, 54) of the driver circuits (80a, 80d) for those 2-way seat valves (20a, 20d) which are associated with the feed line.
10. A positional control according to claim 6 characterised in that there are provided signal generators (56, 58) which can be selectively actuated by the operator and which are selectively connected to subtraction and addition inputs respectively of the arithmetic means (48-54) at the input side of the driver circuits (80a-80d) in order simultaneously to close all four 2-way seat valves (20a-20d) or selectively to close the valves (20a-20d) associated with the feed line and simultaneously to open the valves (20b, 20c) associated with the discharge line.
EP83102914A 1982-04-01 1983-03-24 Position control for a double acting hydraulic motor Expired EP0091018B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83102914T ATE20690T1 (en) 1982-04-01 1983-03-24 POSITION CONTROL FOR A DOUBLE ACTING HYDRAULIC MOTOR.

Applications Claiming Priority (2)

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US06/364,373 US4437385A (en) 1982-04-01 1982-04-01 Electrohydraulic valve system
US364373 1989-06-12

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EP0091018A1 EP0091018A1 (en) 1983-10-12
EP0091018B1 true EP0091018B1 (en) 1986-07-09

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JP (1) JPH0610481B2 (en)
AT (1) ATE20690T1 (en)
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CA (1) CA1202100A (en)
DE (1) DE3364410D1 (en)
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DE3364410D1 (en) 1986-08-14
JPS58180803A (en) 1983-10-22
JPH0610481B2 (en) 1994-02-09
AU550989B2 (en) 1986-04-10
ATE20690T1 (en) 1986-07-15
CA1202100A (en) 1986-03-18
BR8301657A (en) 1983-12-13
ES8404021A1 (en) 1984-04-01
ZA832274B (en) 1984-11-28
US4437385A (en) 1984-03-20
DK137783A (en) 1983-10-02
AU1292383A (en) 1983-10-06
EP0091018A1 (en) 1983-10-12
DK137783D0 (en) 1983-03-25
MX155212A (en) 1988-01-29
ES520993A0 (en) 1984-04-01

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