METHOD FOR CONTROLLING A RECIPROCATING PISTON PUMP AND DEVICE FOR CARRYING OUT THE METHOD

Abstract

A controller of an electromagnetically driven reciprocating pump influences velocity of the magnetic armature by switching voltage applied to the electromagnet depending on the position of the magnetic armature, its position determined from state variables of the electromagnet. A processor calculates electrical resistance of the magnetic coil from the voltage and current measured by the measuring device, and calculates the temporal change of the linked magnetic flux in the electromagnet from the electrical voltage, the current and the resistance of the magnetic coil, and calculates the linked magnetic flux in the electromagnet from an earlier magnetic flux and from the temporal change, and determines the position of the magnetic armature from the linked magnetic flux in the electromagnet and the electrical current through the magnetic coil, and switches the voltage at the magnetic coil by the switching device depending on the position of the magnetic armature.

Claims

1. A method for the control of a reciprocating pump having an electromagnet and a displacement unit loaded by a spring, wherein the electromagnet is built of a magnetic coil, an iron return path and a magnetic armature, by an electrical controller that comprises a memory-programmable processor, a switching device and a measuring device, the method comprising: calculating with the processor the electrical resistance of the magnetic coil from the values of the electrical voltage and of the electrical current measured by the measuring device; calculating with the processor the temporal change of the linked magnetic flux in the electromagnet from the electrical voltage, the electrical current and the electrical resistance of the magnetic coil; calculating with the processor the linked magnetic flux in the electromagnet from a previously calculated or estimated magnetic flux and the temporal change; determining the present position of the magnetic armature using an estimation process performed by the processor in the controller from a table determined by measurements and/or calculations prior to intended operation of the controller and stored in the processor with associated values of the electrical current, the linked magnetic flux and the position of the magnetic armature, wherein the estimation of the position of the magnetic armature is improved in that, with different effective voltages at the magnetic coil, previously determined tables corresponding to the voltage and/or the voltage change with respectively assigned values of the electrical current, the linked magnetic flux and the position of the magnetic armature are used; and the effective electrical voltage at the magnetic coil by adjusting the switching device depending on the position of the magnetic armature.

2. The method for the control of a reciprocating pump according to claim 1, wherein the calculation of the linked magnetic flux is improved in that the initial magnetization of the magnetic armature and of the iron return path from the previous history of the temporal progression of the linked magnetic flux is taken into account during the calculation of the linked magnetic flux in the numerical integration by a starting value.

3. The method for the control of a reciprocating pump according to claim 1, wherein the calculation of the linked magnetic flux in the electromagnet is performed by a numerical integration of electrical and magnetic state variables of the electromagnet carried out in real time.

4. The method for the control of a reciprocating pump according to claim 1, wherein the effective electrical voltage at the magnetic coil is simply switched off, or is switched off and on a plurality of times by the switching device, depending on the position of the magnetic armature so that, through a modulation effected by switching, its effect as a time-average is reduced in comparison to the voltage of a voltage supply.

5. The method for the control of a reciprocating pump according to claim 1, wherein during the return of the magnetic armature by the spring an electrical current through the magnetic coil, decaying slowly due to the coil inductance, is measured by the measuring device and is used through the calculation of the linked magnetic flux to determine the position of the magnetic armature, wherein a previously calculated table with associated values of the electrical current, the linked magnetic flux and the position of the magnetic armature, said table being selected according to a low effective voltage and a negative voltage change, is used.

6. The method for the control of a reciprocating pump according to claim 5, wherein during the return of the magnetic armature by the spring, the information relating to the position of the magnetic armature is used in the electrical controller in order to increase the effective voltage at the magnetic coil depending on the position of the magnetic armature, and thus to brake the movement of the magnetic armature.

7. An apparatus for performing the method according to claim 1, wherein the apparatus consists of a reciprocating pump and an electrical controller and wherein the reciprocating pump consists of an electromagnet and of a displacement unit loaded by a spring, wherein the electromagnet is built of a magnetic coil, an iron return path and a magnetic armature, and wherein the electrical controller comprises a memory-programmable processor, a switching device and a measuring device, wherein the memory-programmable processor contains at least one table calculated prior to intended operation of the controller, with associated values of the electrical current through the magnetic coil, the linked magnetic flux in the electromagnet and the position of the magnetic armature, wherein this table or these tables allow the processor, on the basis of a plurality of measurements of the electrical current by a measuring device, to determine the position of the magnetic armature by an estimation procedure.

8. The apparatus according to claim 7, wherein, by a memory-programmable processor and a switching device, the electrical controller lowers the effective mean electrical voltage at the magnetic coil depending on the armature travel relative to the voltage of a voltage supply such that the curve of the velocity of the magnetic armature is influenced in a manner specified in the processor, wherein the voltage supply feeds electrical power to the switching device and also to the measuring device and furthermore to the magnetic coil.

Description

DRAWINGS

[0035] FIG. 1 shows the apparatus consisting of the reciprocating pump and electrical controller.

DETAILED DESCRIPTION

Exemplary Embodiment

[0036] The apparatus according to FIG. 1 consists of a reciprocating pump (1) and an electrical controller (10), wherein the reciprocating pump consists of an electromagnet (2) and of a displacement unit (3) loaded by a spring (4).

[0037] The electromagnet is built from a magnetic coil (5), an iron return path (6) and a magnetic armature (7).

[0038] An electrical power supply (9) makes electrical power available to the apparatus, wherein the voltage can vary over a specified range, for example between 9 V and 16 V.

[0039] In an electrical controller (10), the electrical voltage is switched by means of a switching device (12), and the effective voltage and the resulting current are measured in a measuring device (13).

[0040] The magnetic coil is supplied with pulsed electrical power by the electrical controller (10), said electrical controller (10) also containing a processor (11) with programmable memory.

[0041] The processor (11) calculates [0042] the electrical resistance of the magnetic coil (5) from the values of the electrical voltage and the electrical current measured by the measuring device (13) [0043] the temporal change of the linked magnetic flux in the electromagnet (2) from the electrical voltage, the electrical current and the electrical resistance of the magnetic coil (5) [0044] the linked magnetic flux in the electromagnet (2) from a previously calculated or estimated magnetic flux and the temporal change

[0045] The position of the magnetic armature (7) is determined by means of the calculated value of the linked magnetic flux and the measured electrical current through the magnetic coil (5).

[0046] The electrical voltage at the magnetic coil (5) is switched by means of the switching device (12) depending on the position of the magnetic armature (7).

[0047] The present position of the magnetic armature is determined using an estimation process in the controller (11) from at least one table calculated prior to intended operation of the controller (10) and stored in the controller (11) with associated values of the electrical current, the linked magnetic flux and the position of the magnetic armature (7).

[0048] Advantageously the calculation of the linked magnetic flux is improved in that the calculation of the linked magnetic flux takes into account the initial magnetization of the magnetic armature (7) and of the iron return path (6) from the previous history of the temporal progression of the linked magnetic flux by means of the starting value.

[0049] A further improvement in the estimation of the position of the magnetic armature (7) is achieved in that, with different effective voltages and voltage changes at the magnetic coil (5), corresponding previously determined tables for different voltages and voltage changes, with respectively assigned values of the electrical current, the linked magnetic flux, and the position of the magnetic armature (7), are used. The effects of the non-linearity of the material properties, the magnetic hysteresis and the eddy currents are thus included in the estimation method.

[0050] The determination of the linked magnetic flux in the electromagnet (2) is advantageously carried out in the memory-programmable processor (11) through a calculation of the electrical and magnetic state variables of the electromagnet using a numerical integration running in real time.

[0051] Depending on the position of the magnetic armature (7) the electrical voltage at the magnetic coil (5) is if necessary switched off, or switched off and on a plurality of times, in the electrical controller (10) by means of the switching device (12), so that the effective voltage in the sense of a pulse-width modulation or of a pulse-length modulation has a time-average whose effect is reduced in comparison with the voltage of a voltage supply (9). When the magnetic armature (7) is moving forward against the force of the spring (4), the movement of the magnetic armature can in this way be braked to the extent that the magnetic armature only runs against its front stop at a very low residual velocity.

[0052] As the magnetic armature (7) is returned by the spring (4), the current through the magnetic coil only decays very slowly due to the inductance of the coil. Here again the current through the magnetic coil is measured by the measuring device (13) and is used in the calculation of the linked magnetic flux for determination of the position of the magnetic armature, wherein a previously calculated table for small voltages and negative voltage changes, also containing the coil current and the linked magnetic flux, is selected for the magnetic armature travel.

[0053] In this type of operation the information about the position of the magnetic armature is used in the electrical controller (10) in order to increase the effective mean voltage at the magnetic coil (5) depending on the position of the magnetic armature, and thus to brake the movement of the magnetic armature.

LIST OF REFERENCE SIGNS

[0054] 1. Reciprocating pump [0055] 2. Electromagnet [0056] 3. Displacement unit [0057] 4. Spring [0058] 5. Magnetic coil [0059] 6. Iron return path [0060] 7. Magnetic armature [0061] 9. Voltage supply [0062] 10. Electrical controller [0063] 11. Memory-programmable processor [0064] 12. Switching device [0065] 13. Measuring device