EP2642133A1 - Digitales Steuerungsverfahren für ein hydraulisches Ein-/Aus-Ventil - Google Patents

Digitales Steuerungsverfahren für ein hydraulisches Ein-/Aus-Ventil Download PDF

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Publication number
EP2642133A1
EP2642133A1 EP12002076.3A EP12002076A EP2642133A1 EP 2642133 A1 EP2642133 A1 EP 2642133A1 EP 12002076 A EP12002076 A EP 12002076A EP 2642133 A1 EP2642133 A1 EP 2642133A1
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EP
European Patent Office
Prior art keywords
pulse
digital control
cycle
time
switching
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.)
Withdrawn
Application number
EP12002076.3A
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English (en)
French (fr)
Inventor
Ingo Schepers
Daniel Weiler
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.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Priority to EP12002076.3A priority Critical patent/EP2642133A1/de
Priority to PCT/EP2013/000892 priority patent/WO2013139489A1/en
Publication of EP2642133A1 publication Critical patent/EP2642133A1/de
Withdrawn legal-status Critical Current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
    • F15B19/00—Testing; Calibrating; Fault detection or monitoring; Simulation or modelling of fluid-pressure systems or apparatus not otherwise provided for
    • F15B19/002—Calibrating

Definitions

  • the invention relates to a method for digitally controlling a hydraulic ON/OFF valve.
  • the invention lies in the field of digital hydraulics.
  • Digital hydraulics implies the usage of ON/OFF valves in a closed or open loop control for controlling an actuator (e.g. a piston of a main stage).
  • a method for controlling an actuator using ON/OFF valves is disclosed in WO 02/086327 A1 .
  • Typical for prior art digital control methods is the discontinuous movement of the actuator which is the result of the discontinuous volume flow which in turn is the effect of switching ON/OFF valves. It is desirable to avoid any discontinuity in the actuator movement.
  • the invention is based on the finding that the discontinuities in the movement of the actuator originate from the pauses in the control signal. This problem occurs especially with ON/OFF valves, since the switching times (time for state change) are relatively long and cannot be neglected.
  • the typical PWM cycle durations must therefore be relatively long in order to account for switching times.
  • the invention achieves to minimize the pauses. It is impossible to simply decrease the cycle duration, because the switching times of the ON/OFF valves are too high for such small PWM cycle durations.
  • the basis of the digital control method is to generate a digital control signal having a number of successive cycles, wherein each cycle consists of a pulse t i with a specific pause t p so that the valve reaches the OFF state at the end of the pause t p . If a new pulse starts at this time the pause is minimized. By minimizing the pauses between pulses, the discontinuity of the actuator movement is reduced and speed and quality of control can be improved.
  • the invention is described in relation to the ON state and the OFF state of the valve, wherein the ON state is the actuated stated caused by a pulse and the OFF state is the normal state caused by a pause.
  • the ON state is the actuated stated caused by a pulse
  • the OFF state is the normal state caused by a pause.
  • NC normally closed
  • NO normally open
  • the OFF state is the open state.
  • the switching off time of an ON/OFF valve is nearly constant. So in this case the pause t p has the length of the switching off time.
  • the pause t p When the pulses are very short so that the piston cannot reach the end stop of the ON state the pause t p must be reduced. Otherwise the pause t p is not optimized.
  • the time period of the pause is chosen so that the valve reaches the OFF state basically at the end of the pause.
  • the resulting digital control method differs from usual PWM in that the sum of pulse and pause duration is not fixed, and differs from usual PFM in that the pulse duration is not fixed.
  • t p ' t p +k r .
  • One preferred possibility to determine a pause period for a specific pulse period is based on a novel model to describe the dynamics of ON/OFF valves during fast switching control signals. This model is described under reference to figure 1 .
  • Another preferred possibility to determine a pause period for a specific pulse period is based on a measurement of the piston stroke. E.g. the time when the piston reaches the OFF position can be measured.
  • one or more ON/OFF valves can be controlled as pilot valves, which in turn operate (e.g. movement or position control) a hydraulic actuator, e.g. a piloted valve, a linear or rotational hydraulic motor, a hydraulic (single-acting or double-acting) cylinder, a variable displacement pump or motor etc.
  • a hydraulic actuator e.g. a piloted valve, a linear or rotational hydraulic motor, a hydraulic (single-acting or double-acting) cylinder, a variable displacement pump or motor etc.
  • a first group and a second group of ON/OFF valves are controlled, wherein the digital control signal for the second group has no pulse while the digital control signal for the first group has a pulse, and wherein the digital control signal for the first group has no pulse while the digital control signal for the second group has a pulse.
  • the first group controls a movement of the actuator and the second group controls an opposite movement of the actuator. This allows for an improvement of speed and quality of control.
  • Each movement of the actuator can be operated by a number of ON/OFF valves.
  • These ON/OFF valves can be controlled synchronously, i.e. having the pulses at the same time, or can be controlled with a time shift between the pulses. This allows for a reduction of discontinuities of the actuator movement and an improvement of speed and quality of control.
  • a computing unit according to the invention is, in particular programmatically, adapted to carry out an inventive method.
  • the implementation of the invention in the form of software is advantageous because it allows particularly low costs, especially when a performing computing unit is still used for other tasks and therefore is present anyway.
  • Suitable media for providing the computer program are particularly floppy disks, hard disks, flash memory, EEPROMs, CD-ROMs, and DVDs etc. A download of a program on computer networks (Internet, Intranet, etc.) is possible.
  • FIG. 1 a relation between a piston stroke s of an ON/OFF valve and a digital control signal v according to a model underlying the invention is shown.
  • the control signal v and the resulting stroke s are shown over time t.
  • the control signal v has two successive cycles T j , T j+1 .
  • the first cycle T j has a pulse duration t i and a pause duration t p .
  • the dynamics of the valve stroke from different kinds of ON/OFF valves basically show similar characteristics.
  • One main effect of the valve dynamics is a time lag between the rising and falling edge of the control signal v and the beginning of the valve stroke s. In general this lag is not symmetrical but different for activation and deactivation. Short pulses or pauses of the control signal are completely suppressed by the valve, thus, the lag is no simple time delay.
  • the time lags which occur whenever the valve was fully activated or deactivated are independent from the width of the pulses and pauses of the control signal and therewith independent from the time the valve was in the activated (ON) or deactivated (OFF) state.
  • the time lag will be much smaller than in the case described above.
  • the effects are mainly influenced by design parameters like spool or poppet mass, spring constant and spring preload or the orifice which controls the damping of the valve stroke but also by parameters which result in different solenoid forces like electric resistance, inductivity or voltage.
  • the cycle start is referenced by T j .
  • the valve piston does not move for a constant time lag. This time lag is called ' switching on delay ' t i,min .
  • the duration t i,min the piston motion starts sharply.
  • the observations of switching valves show that the period of acceleration is in many cases very short, so that this period is neglected in the model.
  • the velocity of the piston during the period of activating the valve is modeled to be constant.
  • the following pulse should start at T j+1 when the valve is in the OFF state.
  • the model parameters P ( t i,min , t on , t v,on , t p,min , t off , t v,off ) which are needed for the model can be identified in different ways, for example by measurements. With the identification of the parameters by measurements a model validation is done in the same iteration. One possibility is to measure the piston stroke. With these measurements the parameters can be identified easily. The parameters can be identified not only by measurements but also by simulations of a more complex and validated existing CFD/FEM-model, for example.
  • An ON/OFF valve according to the model only opens when the pulse period t i exceeds t i , min .
  • a valve lag exists, i.e. if a movement of the piston does not immediately results in a hydraulic opening of the valve, operating the valve within the lag should be avoided.
  • a minimum pulse period defined by t i,min + t lag is preferably provided which substitutes t i , min .
  • each control output of the closed loop control is converted into a pulse having at least a pulse period t i,min + t lag .
  • a minimized pause period t p ( t i ) depending on the preceding pulse period t i can be calculated according the following method:
  • the actually used pause period could comprise the determined pause period t pj ( t ij ) and a robust parameter k r .
  • a minimum pause period ⁇ t is defined to avoid that a cycle period becomes zero.
  • control loop 200 is shown schematically to illustrate a preferred embodiment of the invention.
  • the control loop 200 includes four ON/OFF valves V 1 - V 4 for operating an actuator 210.
  • the actuator 210 may be for example, a piston or a main stage valve of a pilot-operated valve assembly.
  • a set-point value x soll is compared with a feedback actual value x ist and a control error e is calculated therefrom.
  • the control error e is transmitted to a control element 220, e.g. a proportional controller.
  • the control element 220 calculates a control output u based on the control error e.
  • the control output u is transmitted to a calculating block 300 which is shown in more detail in Figure 3 .
  • a digital control signal v is generated according to a preferred embodiment of the invention.
  • the digital control signal v is used to control the valves V 1 - V 4 .
  • valves are connected in pairs, so either the valves V 1 and V 2 are open, while the valves V 3 and V 4 are closed, or vice versa.
  • the actual position of the actuator is detected at 240 and feed back as the actual value.
  • a block 320 the calculated pulse period t ij (u) is quantized to t ij * and transferred to a model block 330.
  • the model block 330 includes the above described relation t pj ( t ij ). Further, the mentioned parameters P are transferred to the model block 330.
  • Such calculated pause period t pj is combined with the robust parameter k r to t prj at 340 and quantized at 350.
  • Quantized pulse period t ij * and quantized pause period t prj * are combined in 360 for generating a digital control signal v.
  • a new pulse t ij+1 * starts immediately after the preceding pause period t prj *.
  • the digital control signal v and the control output u are transmitted to block 370, in which the control signals for the ON/OFF valves V 1 - V 4 are calculated. Which of the two pairs of valves is opened can be decided based on the sign of u. The chosen pair is then controlled with the digital control signal v. E.g. in case u is larger than zero, valves V 1 and V 2 are controlled, and in case u is less than zero, valves V 3 and V 4 are controlled.
  • an alternative embodiment 400 to the calculation of the pause period is based on a measurement of the piston stroke.
  • the time when the valve reaches the OFF position is measured and the following pulse is started when each valve V 1 -V 4 is OFF.
  • Signals S1-S4 representative of the piston strokes are transferred to a determination block 430.
  • a trigger signal is transferred to digital control signal generating block 460. This trigger signal defines the start of the pulse defined by pulse period t ij *.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Magnetically Actuated Valves (AREA)
EP12002076.3A 2012-03-23 2012-03-23 Digitales Steuerungsverfahren für ein hydraulisches Ein-/Aus-Ventil Withdrawn EP2642133A1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP12002076.3A EP2642133A1 (de) 2012-03-23 2012-03-23 Digitales Steuerungsverfahren für ein hydraulisches Ein-/Aus-Ventil
PCT/EP2013/000892 WO2013139489A1 (en) 2012-03-23 2013-03-25 Digital control method for a hydraulic on/off valve

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP12002076.3A EP2642133A1 (de) 2012-03-23 2012-03-23 Digitales Steuerungsverfahren für ein hydraulisches Ein-/Aus-Ventil

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EP2642133A1 true EP2642133A1 (de) 2013-09-25

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016092150A1 (en) * 2014-12-09 2016-06-16 Hydroline Oy Monitoring device and method for determining operating health of pressure medium operated device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4230376A (en) * 1977-04-05 1980-10-28 Girling Limited Anti-lock brake control system II
US20020135229A1 (en) * 2001-03-23 2002-09-26 Unisia Jecs Corporation Anti-skid control system for automotive vehicle
WO2002086327A1 (en) 2001-04-23 2002-10-31 Matti Linjama A control system and a method for controlling an actuator and for optimizing the control by means of sets of valves coupled in parallel

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4230376A (en) * 1977-04-05 1980-10-28 Girling Limited Anti-lock brake control system II
US20020135229A1 (en) * 2001-03-23 2002-09-26 Unisia Jecs Corporation Anti-skid control system for automotive vehicle
WO2002086327A1 (en) 2001-04-23 2002-10-31 Matti Linjama A control system and a method for controlling an actuator and for optimizing the control by means of sets of valves coupled in parallel

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016092150A1 (en) * 2014-12-09 2016-06-16 Hydroline Oy Monitoring device and method for determining operating health of pressure medium operated device
SE541429C2 (en) * 2014-12-09 2019-10-01 Hydroline Oy Monitoring device and method for determining operating health of pressure medium operated device
AU2015359243B2 (en) * 2014-12-09 2019-11-28 Hydroline Oy Monitoring device and method for determining operating health of pressure medium operated device
US11428248B2 (en) 2014-12-09 2022-08-30 Hydroline Oy Monitoring device and method for determining operating health of pressure medium operated device

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