RO129254A2 - Method and system for measuring forces in industrial equipments - Google Patents

Abstract

The invention relates to a method and a system for measuring static forces existing in certain elements of industrial equipments, during operation. According to the invention, the method is based on the use of a multidirectionally deformable element and on measuring the deformation thereof. The system, as claimed by the invention, comprises a base plate (1) wherethrough there pass some top part fastening screws (2), on the base plate (1) there being placed some pieces (3) upon which the forces to be measured act, the said pieces (3) being attached to the base plate (1) by some fastening screws (4) on which a technological process-related tool (5) acts, in the bottom part of the base plate (1) there being cut some grooves (6) wherein some thermocouples are placed for temperature measuring purposes, while under the base plate (1) there are placed some force-deformation multidirectional mechanical transducers (7) placed in some cases (8) stiffened by means of some screws (9) to an equipment displacement table (10), the said transducers (7) being provided with some interstices wherein some Hall transducers (11) or capacitive transducers (12) connected to voltage measuring apparatuses (13) and current measuring apparatuses (14) which communicate with a computer (15) are positioned.

Description

The invention relates to a method and a system for measuring static forces existing in certain elements of industrial equipment, during their operation. The method according to the invention is based on the use of a multidirectional deformable element, and on the measurement of its deformations. The system according to the invention consists of a base plate (1), through which screws (2) fastening on the upper part, on the base plate (1) being placed parts (3) on which the forces acting must be measured, the parts (3) being fastened to the base plate (1) with some screws (4), and a tool (5) related to the technological process acting on them, at the bottom of the base plate (1) some grooves are executed (6) for the placement of thermocouples, in order to measure the temperature, and below the base plate (1) are placed some translucents (7) mechanical force-deformation muitidirectional, located in some cases (8) reinforced with screws (9), a table (10) for translating the equipment, the transducers (7) being provided with intersections in which some Hali (11) or capacitive (12) transducers (12) are connected, connected to apparatus (13) for measuring voltage and , respectively, devices (14) for measuring currents, which communicate with a computer (15).

Claims: 3

Figures: 1

Starting from the date of publication of the patent application, the application provides, provisionally, to the applicant, the protection conferred according to the provisions of art. 32 of Law no. 64/1991, except in cases where the patent application has been rejected, withdrawn or considered to be withdrawn, the extent of the protection conferred by the patent application is determined by the claims contained in the application published in accordance with article 23 paragraph. f1) (3).

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.3 ^ ^a ) Method and system of force measurement

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DESCRIPTION

b) The invention relates to a method of measuring the static forces existing in certain elements of industrial equipment, during their operation. The method is based on the use of a multidirectional deformable element and on the measurement of its deformations with the help of magnetic transducers and of the type of electrical capacity, with standardized measuring devices, specially calibrated for force measurement.

The force measurement method refers to the verification of the operating parameters of the industrial equipment, machinery and machines, the monitoring of the real-time operating parameters and the archiving of the operating parameters, according to the requirements of the quality management system. In particular, the method is applied to positioning and actuating systems, which develop forces of 2 ... 20 kN, from mechanized and automated welding equipment, with or without computerized steering.

c) in the current situation, the forces are measured with specialized force transducers, based on an element that deforms in the elastic field, in which the deformations are proportional to the mechanical stresses applied on the element, and the deformations are transformed into an electrical signal, with the help of some resistive sensors (tensometric stamps) or inductive [1, 2], By calibration, the proportionality relation between the electrical signal, on the one hand, and the information, on the other, is established. Also, by calibration, the proportionality relation between the deformation and the realized mechanical stress is established [1 - 7], in case the modulus of elasticity E of the deformable element is not known. This is the principle of indirect force measurement methods. In essence, the deformation is actually measured, which is transformed into a signal of another nature. Although transformations from one physical size to another and changing the physical nature of the signals used require some simplifying assumptions, and these can lead to errors of lack of proportionality, it is considered that the measurement principle is correct and accurate. In this situation, one can state the hypothesis that it is possible to use any method of measuring the deformation, for the indirect measurement of the force.

The necessary conditions are:

1. the deformable element is correctly located;

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2. the element deforms in the elastic domain;

3. The entire measuring system must be properly calibrated.

The current methods of measuring forces have the following disadvantages: greater translator assembly overall and placement difficulties, difficulties in design and execution, but also a higher cost for the translator and the measuring system.

'The proposed principle for measuring forces with magnetic or capacitive sensors is described below.

The proposed method of measuring the forces, according to the invention, aims to measure the deformations of a specially designed deformable element, by using a Hali transducer for the intensity of the magnetic field in certain spacings of the deformable element, respectively by using a capacitive transducer for certain intersections of deformable element. . The signals given by the respective translators are measured with certain standardized devices, having the precision class given by the manufacturer. Calibration of the entire force measurement system is performed, based on the proportionality relations between the deformation-force electrical signal. This eliminates the mentioned disadvantages regarding the current systems.

e) The electrical signal given by the Hali transducer is an electromotive voltage U _eH proportional to the intensity of the magnetic field H:

(1) where k _H is the constant of the Hali effect specific to the transducer used.

To determine the intensity of the magnetic field, the Ohm's law is applied for the magnetic circuit in which a permanent magnet is included:

(2) where: Φ [Wb] is the magnetic flux in the considered magnetic circuit; M [A] is the magnetization of the permanent magnet; R _m [Η ^_ι ] is the magnetic reluctance of the magnetic circuit in which the Hali transducer is located.

Neglecting the magnetic tension in the ferromagnetic circuit, compared to the magnetic tension in the air gap, the above relation obtains the following form:

where: μ ₀ [Hm ¹ ] is the magnetic permeability of the air gap; S [m ² ] is the surface of the air gap; d [m] is the length of the air gap.

From this results the value of the intensity of the magnetic field in the air gap, where the Hali translator is:

^ -2012-00530-1 6 -07- 2012 p ₀ S (3)

d (4)

The electromotive voltage given by the Hali transducer, indicated by a typical voltage measuring device, has the following expression:

It is found that the measured voltage is inversely proportional to the air gap, respectively the deformation and the force.

In the case of the flat capacitive transducer, the electrical capacity is given by the relation:

_ __ £,. £ ₀ S k, d (6) where: F [dimensionless] is the relative dielectric permittivity of the material from which the capacitive transducer is made; ⁰ [Movie ¹ ] is the dielectric permittivity of the vacuum; S [m ² ] is the surface of the planar capacitor transducer surface; Ld [m] is the distance between the reinforcements, which represents part k _; of the intersection d, where the capacitive transducer is located.

This capacitance can be measured in an alternating current circuit, powered by voltage U, low or high frequency, having capacitive impedance Zc, in which a current I is determined, defined by the relation:

Z _c (7)

The expression of capacitive impedance is taken into account:

mc (8)

ev 2 O 1 2 - O o 5 3 O - - 33 ί 6 -07- 2012

Thus the relationship becomes:

I = U (oC (9) where ω [Hz] is the pulse of the internal operating voltage of the capacitance measuring circuit.

= (10)

Explaining the capacity definition relationship, the current that is measured is:

_I _ 2nUfs _r e ₀ S ^k ' ^d (11)

It is found that in this case the signal given by the translator is inversely proportional to the intersection where the translator is, respectively inversely proportional to the deformation and the force. This can be an advantage to small variations of the intersection, which correspond to high values of force. In this area, the sensitivity of the translator is relatively higher.

For comparison, the defining relationships of an inductive translator are presented.

The inductance of the inductive transducer coil is given by the relation:

_T _ N ² S ~ ¹ (12) where N is the coil number of the coil; S [m ² ] is the surface of the coil's ferromagnetic core; 1 [m] is the opening of the coil's ferromagnetic circuit air gap.

By inserting the transducer coil into an alternating current circuit at U, low or high frequency voltage, whose inductive impedance is Z _L , the current I is determined, having the expression:

(13)

The relationship of defining the inductive impedance is considered:

Z ₇ = ojL (14)

The expression of the current becomes as follows:

a> L (15)

Taking into account the above expressions, the relation of the measured current is:

UI aN ² S (16)

52 It is found that the value of the measured current is directly proportional to the length / gap of the magnetic circuit of the transducer, respectively to the deformation and to the force.

Also for comparison, the defining relationships of a resistive transducer, such as the tensometric stamp type, are presented.

The resistance of the translator is given by the relation:

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^d (17) where ρ [Ωηι] is the electrical resistivity of the transducer material; 1 [m] is the length of the electrical conductor of the transducer; S [m ² ] is the section of the conductor of the transducer.

Introducing the transducer into a DC or AC circuit, fed to voltage U, determines current I, having the expression:

^Λ (18)

Taking into account the above expression, the relation of the measured current is:

/ = 55 ^pl (19)

It is found that the value of the measured current is inversely proportional to the length l of the electrical conductor of the transducer, respectively to the deformation and the force. For the resistive translator the length is considered to vary under the effect of the applied force. But it is a mechanical elongation made by means of the adhesive with which the transducer is fixed by a metallic element subjected to deformations. The properties of this adhesive can deteriorate over time, which can negatively affect the calibration feature of the translator. It should be checked periodically and possibly recalibrated.

f) The proposed method of measuring forces, according to the invention, has the following advantages;

• It allows the realization of deformable elements with the role of mechanical translator force deformation, with linear dependence function, in the field of elastic deformations. These elements can be designed and executed according to the dimensions and characteristics of the parts of the equipment where they are assembled for the purpose of measuring forces.

• It makes it possible to use certain types of measuring devices, having a certain precision class, for determining electrical signals directly or inversely proportional to the intensity of the magnetic field or to the electrical capacity, as intermediate sizes for measuring the deformation and force.

• Allows the calibration and calibration of the force measurement system assembly, for (V-2 0 1 2 - 0 0 5 3 0 - 1 6 -87- ΐβκ a certain field of forces, depending on the specific demands existing in the component elements of the equipment Calibration is performed on a mechanical testing machine, having a higher precision class. Calibration is performed for each direction of request of the deformation element as mechanical translator.

• Ensures the acquisition of the measurement results on the computer of the automatic system of the industrial equipment to which the force measurements are made, by means of the specialized software for the acquisition of data and by the own facilities of the typical measuring devices used.

• It has a relatively low cost, due to the fact that the measurement method is mostly based on standardized devices.

• The value of the performance / cost ratio is very advantageous, as the performance can be high, and the costs are relatively low, compared to the measurement methods based on multidimensional translators for forces and systems for general-purpose data acquisition, which are too large for purpose.

g) Figure 1 represents the general drawing of a system of force measurement for an industrial equipment, to which the proposed method is applied.

h) The following is an example of embodiment of the invention in relation to figure 1:

The method of measuring the forces is applied on a system consisting of a base plate (1), through which the fastening screws on the top (2) pass, on the base plate being placed the parts (3) related to the technological process, on to which the forces to be measured act, and the parts of the technological process are fastened by the base plate with the fixing screws (4) and on the parts the tool (5) of the technological process acts, at the bottom of the base plate the grooves are executed (6) for the placement of thermocouples in order to measure the temperature, which is another parameter of the technological process, and under the base plate are located the specially designed force-deformation multidirectional mechanical transducers (7), which constitute an original element of the invention, the transducers, located in the housings ( 8), being reinforced with the lower mounting screws (9), relative to the translation table (10) of the industrial equipment Therefore, according to the invention, in certain intersections executed in the body of mechanical force-deformation multidirectional transducers, Hali (11) or capacitive (12) transducers are positioned, connected to standard voltage measuring devices (13), respectively to standardized devices. for measuring currents (14), in circuits ^ -2012-00550 “1 6 -07- 2012 of Hali or capacitive transducers, the devices being provided with facilities and own software for data acquisition on the computer (15) of the industrial equipment, and the system the actual measurement consisting of the components mentioned in items (7), (11), (12), (13), (14) and (15) is calibrated and calibrated beforehand on a machine for mechanical tensile and traction tests. compression, in order to determine the characteristics of the force - deformation - electrical signal, for all the directions of application of the forces to be measured, so that the mode of functions Acceptance of the whole system consisting of the mentioned components is a method of measuring forces, as the original principle of the invention.

i) the invention can be applied industrially to friction welding, friction welding with rotary active element (friction welding, FSW), pressure welding, ultrasonic welding, bolt welding, welding of plastic pipes (polyethylene). high density, polypropylene, vinyl polychloride etc.), positioning and handling systems, positioning and rotating tables, roller blocks, movable columns with console, etc.

Bibliography

1. Dally J. W.; Riley W. F.: Experimental Stress Analysis. 3rd ed. McGraw-Hill, New York, 1991.

2. Dally J. W.; Riley W. E; McConnell; K. G.: Instrumentation for Engineering Measurements. 2nd ed. Wiley, New York, 1993.

3. Hung Y. Y: Shearography: A new optical method for foreign measurement and nondestructive testing. In: Optical Engineering. May / June, 1982, pp. 391-395.

4. Lee Y. L.; Lu M. W.; Breiner R. W.: Load acquisition and damage assessment of a vehicle bracket component. In: International Journal of Materials and Product Technology. Vol. 12, No. 4-6, 1997, pp. 447-460.

5. Kobayashi A. S.: Handbook on Experimental Mechanics. 2nd rev. ed. VCH Publishers. New York, 1993.

6. Perry C. C.; Lissner H. R.: The Foreign Gage Primer. 2nd ed. McGraw-Hill. New York, 1962.

7. Brophy J. J.: Basic Electronics for Scientists. 3rd ed. McGraw-Hill. New York, 1997.

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Claims (3)

claims 1. Method of measuring the forces for industrial equipment, characterized in that it is applied on a system consisting of a base plate (1), through which the fastening screws on the upper part (2) pass, on the base plate being placed the parts (3) related to the technological process, on which the forces that need to be measured act, and the parts of the technological process are attached to the base plate with the fixing screws (4) and on the parts the forces Fx, Fy and Fz produced by the tool (5) act. ) of the technological process, and under the base plate there are grooves for thermocouples (6) and the mechanical force-deformation (7) mechanical transducers (7) are mounted, mounted in the housings (8), the transducers being stiffened with the lower mounting screws (9). ), relative to the translation table (10) of the industrial equipment, so that, according to the invention, in certain intersections executed in the body of the mechanical translators force-deformation multidirectionals are positioned Hali transducers (11) or capacitive transducers (12), connected to typical voltage measuring devices (13), respectively to typical currents measuring devices (14), from the Hali or capacitive transducer circuits, the devices being provided with facilities and own software for data acquisition on the computer (15) of the industrial equipment, and the measuring system itself consisting of the components mentioned in the positions (7), (11), (12), (13), ( 14) and (15) is calibrated and calibrated beforehand on a mechanical test machine for traction and compression, in order to determine the characteristics of force - deformation - electrical signal, for all directions of application of the forces to be measured, so that the functioning of the whole system consisting of the mentioned components is a method of measuring the forces, as the original principle of invention. 2. System of force measurement for industrial equipment, characterized in that it consists of a base plate (1), through which the fastening screws on the upper part (2) pass, on the base plate being placed the parts ( 3) related to the technological process, on which the forces to be measured act, and the parts of the technological process are fastened by the base plate with the fixing screws (4) and on the parts the forces Fx, Fy and Fz produced by the tool (5) of the technological process act , and under the base plate there are grooves for thermocouples (6) and the force-deformation multidirectional mechanical transducers (7) are located, Α-'2Ο 1 2 - 0 0 5 3 0 - - 71 • ί -07- 20C mounted in the housings (8), the transducers being stiffened with the lower mounting screws (9), relative to the translation table (10) of the industrial equipment, so that according to the invention, in certain intersections executed in the body of the mechanical force-deformation multidirectional transducers, Hali (11) or capacitive (12) transducers are positioned, connected to typical voltage measuring devices (13), respectively to Typical currents measuring devices (14), from the Hali or capacitive transducer circuits, the devices being provided with facilities and software for data acquisition on the computer (15) of the industrial equipment, and the measuring system itself consisting of the components mentioned at positions (7), (11), (12), (13), (14) and (15) are calibrated and pre-calibrated on a mechanical tensile and compression testing machine, in The purpose of determining the characteristics of force deformation - electrical signal, for all the directions of application of the forces to be measured, so that the whole system consisting of the mentioned components represents the original material entity of principle of the invention. 3. Specially designed force-deformation (7) multidirectional mechanical transducers, which are original elements of the invention, characterized in that they are stiffened with the upper mounting screws (2) relative to a base plate (1), on which are the parts (3) of the technological process, which act on the forces Fx, Fy and Fz produced by the tool (5) of the technological process, respectively the transducers are stiffened with the lower mounting screws (9), relative to the translation mass (10) of the industrial equipment, so that according to the invention, in certain intersections executed in the body of the mechanical force-deformation multidirectional transducers, Hali (11) or capacitive (12) transducers are connected, connected to standard voltage measuring devices (13) , respectively to typical devices for measuring currents (14), from Hali or capacitive transducer circuits, the devices being pre viewed with facilities and own software for data acquisition on the computer (15) of industrial equipment, and the actual measurement system consisting of the components mentioned in items (7), (11), (12), (13), (14 ) and (15) it is calibrated and calibrated beforehand on a mechanical test machine for traction and compression, in order to determine the characteristics of force deformation - electrical signal, for all directions of application of the forces to be measured.