KR100965386B1 - Micro force sensor - Google Patents

Abstract

Micro force measuring sensor according to the present invention is a fixed end; One end is fixed to the stationary end and has four measurement planes extending in one direction from the stationary end, each adjacent measurement plane is bent at 90 degrees to each other, and at the end opposite to the stationary end is perpendicular to the four planes. Hollow-shaped deformation portion is formed end surface; At least two notches spaced apart from said fixed end at each edge of four measurement surfaces; A strain gauge disposed on the measurement surface between the notches spaced apart at the same distance from the fixed end at each edge; And a contact tip having greater rigidity than the deformation part and attached to the center of the end face of the deformation part. When a force is applied to one point of the contact tip, the magnitude of the applied force and the position of the point at which the force is applied are It is characterized by being calculated by the equation.

Force Measurement, Micro Force, Strain, Strain Concentration, Manipulator

Description

Micro Force Measuring Sensor {MICRO FORCE SENSOR}

The present invention relates to a micro force measuring sensor with improved measurement sensitivity capability in order to measure accurate contact force and contact position in accordance with the trend of ultra precision and miniaturization. The micro force measuring sensor according to the present invention can be applied to a manipulator, a measuring tool, etc. used in the process of assembling or aligning precision parts.

In keeping with current ultra-precision market trends, there is a need to improve the sensor's ability to measure more precise and accurate contact force and contact position as it continues to be miniaturized.

Subminiature components are assembled through a complex process, which requires highly precise location responsiveness and sophisticated control. In addition, when manipulating vulnerable objects, accurate force measurement is urgently needed.

In addition, when the vision system cannot be used, it is necessary to place the object on the desired position or to check whether the object is correctly positioned at the desired position. When the force or position information is acquired only by contact of the probe, Force measuring sensors are required to have more sensitive measurement sensitivity.

Conventional force measuring sensors using the measurement of the strain may be used by attaching the sensor to a simple beam. This is to calculate the magnitude of the force acting by measuring the amount of deformation generated when the force acts at a certain point through the sensor.

In order to measure small force, the length of the beam should be long and the thickness should be minimized. However, if the length of the simple beam is longer than a certain level, deformation due to its own weight may occur, resulting in an inaccurate result.

In addition, in the case of the conventional simple cantilever, when the force acts on the free end, the stress and the amount of change have the highest value near the fixed end, so that the stress and the change rate are concentrated near the fixed end. Therefore, in order to obtain a large measurement value, the attachment position of the strain measurement sensor is limited to the vicinity of the fixed end. However, the measurement of force based on the deformation concentrated at the fixed end is too narrow and the reliability of the results is difficult.

The present invention is to improve the sensitivity of the force measurement by minimizing the effects of disturbance by changing the structure of the configuration of the conventional force measurement sensor beyond the method of limiting the measurement of the strain in the above-mentioned conventional force measurement sensor near the fixed end To provide a force sensor.

The object of the present invention is a fixed end, and having a measuring surface that is fixed at one end to the fixed end and extends in one direction from the fixed end, the metal plate and the measurement of the metal plate having one or more notches formed on the measuring surface It is achieved by a micro-force measuring sensor comprising a strain gauge attached to a portion of the surface of the notch is formed.

In addition, it is preferable that the metal plate is further formed with a reinforcing surface in any one region except for the portion where the notch is formed.

In addition, it is preferable that a contact tip having a width narrower than the width of the metal plate and having a rigidity greater than that of the metal plate is further formed at the free end of the metal plate.

In addition, it is preferable to further include a cover formed with an opening formed so that the space for accommodating the fixed end, the metal plate and the contact tip is exposed to the outside of the front of the contact tip.

In addition, the distance between one side of the opening of the cover and the contact tip is preferably smaller than the maximum deflection value of the plastic deformation of the metal plate does not occur and the maximum deflection value of the metal plate does not cause damage to the strain gauge.

In addition, the fixed end is a rubber plate, it is preferable that the rubber plate is fixed to the cover.

In addition, it is preferable that two notches spaced apart from each other in the one direction are formed on the measurement surface of the metal plate.

The object of the present invention described above has a fixed end and a plurality of measuring surfaces having one end fixed to the fixed end and extending in one direction from the fixed end and interconnected to each other to form a predetermined angle, both sides of each measuring surface A deformation portion formed with a notch in the strain portion, a strain gauge attached adjacent to the notch to two or more measurement surfaces of the plurality of measurement surfaces of the deformation portion, and fixed to a free end opposite to one end of the deformation portion; It is also achieved by a micro force measuring sensor comprising a contact tip with greater stiffness.

The micro-force measuring sensor according to the present invention forms a notch at the strain measuring point of the metal plate so that the deformation is concentrated at the no-forming point so that a large strain measurement value is obtained to find the magnitude of the force and the point of action of the force. The height is effective.

In addition, by increasing the rigidity in parts other than the notch point, it minimizes the occurrence of errors due to disturbance and brings the effect that the deformation is concentrated in the notch point.

In addition, by attaching a contact tip to the free end of the metal plate, a large strain value was obtained by increasing the moment arm length without increasing the weight of the metal plate.

In addition, the cover minimizes the influence of disturbance on the micro-force measuring sensor and properly limits the width of the opening of the cover to prevent plastic deformation of the metal plate and damage of the strain gauge.

Hereinafter, with reference to the accompanying drawings will be described the configuration of the micro force measuring sensor according to a preferred embodiment of the present invention.

1 is an exploded perspective view showing the configuration of a micro force measuring sensor according to a preferred embodiment of the present invention, Figure 2 is a perspective view of a micro force measuring sensor according to a preferred embodiment of the present invention, Figure 3 is a preferred embodiment of the present invention A perspective view of a measuring unit of the micro force measuring sensor according to the embodiment. As shown in Figures 1 to 3, the micro force measuring sensor according to a preferred embodiment of the present invention comprises a fixed end 1, a metal plate 10, a contact tip 30 and a cover 20 do. The whole of the metal plate 10, the fixed end 1 and the contact tip 30 is called a measuring unit.

The metal plate 10 has a fixed portion 11 formed in a planar shape at one end thereof, and a deformation portion 15 extending in one direction from the fixed portion 11 is formed. The fixing part 11 is formed with bolt holes 12 for bolting. The deformable portion 15 includes a measuring surface 16 formed in parallel with the fixing portion 11 and a reinforcing surface 19 bent perpendicularly to the measuring surface 16 at both edges of the measuring surface 16. Thus, the deformable portion 15 has a 'c' shaped cross section. The measurement surface 16 of the deformable portion 15 has a V-shaped notch 17 formed at both edges of each of the two points located apart from each other along the extending direction. A strain gauge 50 is attached to each point where the V-shaped notch 17 of the measurement surface 16 is formed. The reinforcing surface 19 of the deformable portion 15 is formed only in a portion where the V-shaped notch 17 is not formed among the edges of both sides of the measuring surface 16. In this embodiment, a copper plate was used as the metal plate 10.

The fixed end 1 is for fixing one end of the metal plate 10. In this embodiment, the fixed end 1 is formed of a pair of rubber plates, and each rubber plate has a bolt hole 3 for bolting with the metal plate 10. Are formed. A pair of rubber plates are overlapped with the fixing part 11 of the metal plate 10 on both sides of the fixing part 11 of the metal plate 10, the metal plate 10 with the fixing end 1 is described later It is fixed to the cover 20 to be bolted through.

The contact tip 30 is joined to the measurement surface 16 to extend by a certain length from the measurement surface 16 of the deformation part 15. The contact tip 30 uses a material having rigidity greater than that of the metal plate 10 as a structure that is relatively rigid with respect to the metal plate 10. In this embodiment, the contact tip 30 has a diameter of about 0.1 mm. Use tungsten tips. Therefore, the contact tip 30 is not deformed even if the metal plate 10 is deformed below a certain force.

The cover 20 is composed of a left case 21 and a right case 26 which are mutually coupled to protect the measurement unit.

The inner side of the left case 21 is formed by projecting the measuring unit settlement portion 22 in which the measurement unit can be located, and the metal plate 10 and the fixed end 1 in one region of the measuring unit settlement 22. The bolt holes 24 corresponding to the bolt holes 12 and 3 formed in Fig. 2 are formed. Bolting holes 25 for bolting to the right case 26 are formed at each corner of the left case 21.

The right case 26 is coupled to the left case 21 to accommodate the measurement unit therein, the inner surface of the right case 26 is formed with a measuring part accommodating groove 27 which is a space in which the metal plate 10 is accommodated. It is. An opening 28 is formed at the front end of the right side case 26, which is connected to the measuring part receiving groove 27 and is a hole penetrated by the front end of the right side case 26. A wiring hole 29 is formed at a rear end of the right case 26 to be connected to the measuring part receiving groove 27 and penetrates to the rear end of the right case 26 to form a path of a wiring (not shown).

When the left case 21 and the right case 26 are coupled to each other by the measuring unit, the contact tip 30 of the measuring unit is exposed to the outside through the opening 28.

Figure 4 is a perspective view showing that the outer cover is mounted on the micro force measuring sensor according to an embodiment of the present invention. As shown in FIG. 4, the micro force measuring sensor according to the preferred embodiment of the present invention is mounted inside the outer cover 40 having the outer opening hole 42 so that the contact tip 30 is exposed. At this time, the outer cover 40 protects the micro force measuring sensor from the outside and minimizes the influence of the temperature change.

5 is a side view schematically showing the state of the opening and the contact tip of the cover when the measurement of the micro force measuring sensor according to a preferred embodiment of the present invention deforms to the elastic limit point. As shown in FIG. 5, the width of the opening 28 formed in the cover 20 needs to be limited. The contact tip 30 is positioned at the maximum deflection position of the smaller value of the maximum deflection position where the plastic deformation of the metal plate 10 does not occur and the maximum deflection position of the metal plate 10 where the damage of the strain gauge 50 does not occur. It should not touch the opening 28 of the cover 20. As a result, the width of the opening portion 28 of the cover 20 limits the moving range of the contact tip 30, thereby preventing plastic deformation of the metal plate 10 and also preventing damage to the strain gauge 50. have.

Hereinafter will be described the operation and effect of the micro-force measurement sensor according to a preferred embodiment of the present invention.

6 is a plan view of the measuring part of the micro force measuring sensor according to an embodiment of the present invention from the top down. As shown in FIG. 6, when a force acts on a point of the contact tip 30 of the measuring unit, the magnitude of the force and the position at which the force acts are determined by the following equation.

σ: stress

ε _a : strain at point a

M: Moment

I: Moment of Inertia

y is the distance from the neutral surface

E: Young's modulus

x: position of force

x ₁ : Position of strain gauge 1

x ₂ : Position of strain gauge 2

F: working force

Combining the equation for ε ₁ and the equation for ε ₂ in Equation 1 calculates the magnitude of the force (F) and the position (x) of the force action point as shown in Equation (2).

V-shaped notches 17 are formed on the metal plate 10, which is a portion for measuring strain in the micro-force measuring sensor according to the preferred embodiment of the present invention, and at the same time, strain gauges 50 are formed in the V-shaped notches 17. ) Is attached. Therefore, when a certain magnitude of force is applied to the contact tip 30 of the measuring part, the section of the measurement surface 16 of the metal plate 10 adjacent to the V-shaped notch 17 is determined by the V-shaped notch 17. Becomes smaller. As a result of the deformation being concentrated around the notch point, the strain measured by the strain gauge 50 in the portion adjacent to the V-shaped notch 17 becomes relatively large as compared with the case where the V-shaped notch 17 is not formed. do. As a result, larger results can be obtained, thereby reducing the influence of errors that may occur in the measurement, thereby making it possible to more accurately measure the magnitude and force of the force.

In addition, in the micro-force measuring sensor according to the present invention, since the strain has a large value at the point of the V-shaped notch 17, the attachment point of the strain gauge 50 does not need to be limited to the vicinity of the fixed end 1 and two strains. The gauges 50 do not need to be located close to each other. Therefore, since the strain gauges 50 are attached to two points spaced apart from each other, the values measured at each strain gauge 50 may have a difference of a predetermined size or more.

In contrast, when the notch is not formed in the metal plate 10, two strain gauges 50 should be attached to the portion adjacent to the fixed end 1 in order to obtain a strain having a value greater than or equal to a predetermined size. When the two strain gauges 50 are attached to the portion adjacent to (1), the values of the strains measured are difficult to have a large difference because the distance of each strain gauge 50 is short. If the difference between the measured strain values is small, the effect of the error is large and an incorrect result is obtained.

In addition, since the reinforcing surface 19 is formed in addition to the formation point of the V-shaped notch 17 among the measuring surfaces 16 of the metal plate 10, the reinforcing surface 19 is not formed. It has a large cross section modulus. As the reinforcement surface 19 which increases the rigidity is formed on the metal plate 10, when a constant force is applied to the contact tip 30 of the measurement unit, the deformation is concentrated to the formation point of the V-shaped notch 17 so that the V-shaped notch ( The strain at the formation point of 17) has a larger value. As a result, larger results can be obtained, thereby reducing the influence of errors that may occur in the measurement, thereby making the measurement of the magnitude of the force and the point of action of the force more accurate. In addition, since the rigidity of the metal plate 10 is increased by forming a reinforcing surface 19 on the metal plate 10 to have a 'c'-shaped cross section, vibrations caused by disturbance are minimized, thereby enabling more accurate measurement.

In addition, since the magnitude of the force input to the micro force measuring sensor according to the preferred embodiment of the present invention is a unit of micronewtons (μN) or millinewtons (mN), the strain of the metal plate 10 generated by such microforces is greatly increased. To do this, the arm length of the moment is lengthened and the value of the moment must be increased. However, when the arm length is increased, deflection occurs due to an increase in the weight of the metal plate 10 due to an increase in the length of the metal plate 10, thereby causing an error in measurement. This is because the metal plate 10 used in the micro force measuring sensor has a very thin thickness due to the nature of measuring the micro force, so that sagging occurs easily. Therefore, in this embodiment, the contact tip 30 was used to extend the arm length while minimizing the increase of the weight. The contact tip 30 was made of tungsten, a material having a large rigidity, and had a very small width compared to the width of the metal plate 10. Thus, increasing the length of the moment arm while minimizing the increase of its own weight.

In addition, the micro force measuring sensor according to the present invention can be applied to a manipulator for manipulating the micro components, the micro force measuring sensor according to the present invention formed a fine contact tip 30 at the end of the metal plate 10 Therefore, it is possible to smoothly perform the precision work of manipulating fine parts.

It was confirmed through two experiments whether the magnitude of the force calculated by the signal value output through the micro-force measuring sensor according to the present invention accurately follows the magnitude of the force actually acted on.

FIG. 7 is a graph illustrating a correlation between a signal value of a strain gauge and an operating force output when a force having a known magnitude is applied to a micro force measuring sensor according to a preferred embodiment of the present invention. When the micro force measuring sensor according to the preferred embodiment of the present invention is given a displacement corresponding to a force of a known magnitude through a laser displacement, the correlation between the signal value of the strain gauge outputted and the acting force corresponding to the displacement is shown. It is a graph.

First, the signal value of the strain gauge 50 that is output by applying a force of a known magnitude through the load cell to the micro force measuring sensor according to the present invention was confirmed. As a result, as shown in the graph of Figure 7, it can be seen that there is a linear relationship between the applied force and the signal value.

Secondly, the signal value of the strain gauge 50 outputted when giving a displacement corresponding to a force of a known magnitude through the laser transducer to the micro force measuring sensor according to the present invention was examined. As a result, as shown in the graph of Figure 8 it can be seen that there is a linear relationship between the applied force and the signal value.

As shown in the above two experiments, the signal value output from the micro force measuring sensor according to the present invention has a linear proportionality to the applied force. Therefore, when an appropriate calibration equation is applied, the micro force measuring sensor according to the present invention provides the correct force. It is confirmed that the value can be calculated.

The above experimental result is the final value in the form of GUI finally through the algorithm implemented by transferring the signal value measured from the strain gauge 50 of the micro-force measuring sensor according to the present invention through amplification, filtering, etc. The result is confirmed.

9 is a perspective view schematically illustrating a configuration of a measuring unit of a micro force measuring sensor according to another exemplary embodiment of the present invention. As shown in Figure 9, the micro-force measuring sensor according to another embodiment of the present invention in the other configuration is the same as or similar to the configuration of the micro-force measuring sensor shown in Figures 1 to 3 and in the configuration of the measuring unit There is a difference. Therefore, in the present embodiment, the description of the configuration other than the measurement unit will be omitted, and the description will be mainly focused on the configuration of the measurement unit.

The measuring unit of the micro force measuring sensor according to the present embodiment includes a deformation unit 100. The deformable part 100 is fixed to the fixed end 110 and has four measuring surfaces 116 extending in one direction from the fixed end. Each of the adjacent measuring surfaces 116 is bent to form an angle of 90 degrees. An end surface 117 is formed at an end portion opposite to the end 110 in a direction perpendicular to the four measurement front surfaces 116. The deformation part 100 is a hollow structure surrounded by four measurement surfaces 116 and an end surface 117.

A V-shaped notch 17 is formed at each edge of the four measuring surfaces 116, and each of the two measuring surfaces 116 adjacent to each other has a strain gauge 50 at a portion adjacent to the V-shaped notch 17. ) Is attached.

A tungsten contact tip 30 is attached to the center of the end surface 117 of the deformable portion 100.

Therefore, the micro-force measuring sensor according to another embodiment of the present invention can measure the force in a direction horizontal to the end surface because the strain gauge is attached to the two measuring surfaces perpendicular to the deformation portion.

That is, the micro-force measuring sensor according to the preferred embodiment of the present invention shown in Figures 1 to 3 is provided with a strain gauge only on one measurement surface, but can measure only the force in the direction perpendicular to the one measurement surface. Since the micro-force measuring sensor according to another embodiment of the present invention shown in FIG. 9 can measure the forces in two mutually perpendicular directions by the strain gauges respectively attached to the two measuring surfaces disposed perpendicular to each other, By combining the measured forces in the two directions it is possible to measure the force acting in the direction horizontal to the end surface of the deformation portion. In conclusion, the micro-force measuring sensor of the embodiment shown in Figures 1 to 3 can measure the force in the one-dimensional direction, but the micro-force measuring sensor of the embodiment shown in Figure 9 can measure the force in the two-dimensional direction do.

In the preferred embodiment of the present invention, the shape of the notch formed on the metal plate 10 of the micro force measuring sensor has been described using the V-shaped notch 17 as an example, but the present invention is limited to the shape of the notch formed on the metal plate 10. It is also possible to form a round notch, a square notch, and the like on the metal plate 10.

In the micro force measuring sensor according to the preferred embodiment of the present invention, since the metal plate 10 is covered by the cover 20 and only the thin contact tip 30 is exposed to the outside through the opening, measurement by disturbance such as wind. Error is minimized.

In the preferred embodiment of the present invention, for example, two notches are formed on the metal plate 10 of the micro force measuring sensor, but the present invention is not limited thereto, and the notch is formed on the metal plate 10 of the micro force measuring sensor. It is also possible to form one. If only one notch is formed, knowing one of the magnitude of the force and the location of the force action enables the measurement of the rest of the magnitude of the force and the location of the force action.

In the preferred embodiment of the present invention, a metal plate, in particular, a copper plate of metal plate is exemplified as the plate of the micro force measuring sensor. And it is not limited to a specific material as long as it shows a material deforming the force of the nanonewton force.

1 is an exploded perspective view showing the configuration of a micro force measuring sensor according to a preferred embodiment of the present invention,

2 is a perspective view of a micro force measuring sensor according to a preferred embodiment of the present invention,

3 is a perspective view of a measuring unit of the micro force measuring sensor according to an embodiment of the present invention,

Figure 4 is a perspective view showing that the outer cover is mounted on the micro force measuring sensor according to a preferred embodiment of the present invention,

5 is a side view schematically showing the state of the opening and the contact tip of the cover when the measurement of the micro force measuring sensor according to a preferred embodiment of the present invention deforms to an elastic limit point,

6 is a plan view of the micro-force measuring sensor according to a preferred embodiment of the present invention looking down from the top,

FIG. 7 is a graph showing a correlation between a signal value of a strain gauge and an operating force output when a force having a known magnitude is applied to a micro force measuring sensor according to a preferred embodiment of the present invention.

8 is a correlation between a signal value of a strain gauge output when a force corresponding to a force of a known magnitude is applied to a micro force measuring sensor according to a preferred embodiment of the present invention and an acting force corresponding to the displacement. Is a graph.

9 is a perspective view schematically illustrating a configuration of a measuring unit of a micro force measuring sensor according to another exemplary embodiment of the present invention.

Explanation of the Main References

1: fixed end 10: metal plate

16: measuring surface 17: V-shaped notch

19: reinforcement surface 20: cover

30: contact tip 40: outer cover

50: strain gauge

Claims (8)

A fixed end; One end is fixed to the fixed end and has a measuring surface extending in parallel in one direction from the fixed end, wherein the measuring surface is formed with two or more notches spaced apart from each other in the one direction, except for the portion where the notch is formed A plate having a reinforcing surface bent in one region; A strain gauge attached adjacent to a portion in which the notch is formed in the measurement surface of the plate; And A contact tip formed at a free end of the plate to have a width narrower than the width of the plate and to have a rigidity greater than that of the plate, When a force is applied to one point of the contact tip, the magnitude of the force applied and the position of the point where the force is applied to the micro-force measuring sensor, characterized in that calculated by the following equation. [Equation]

σ: stress ε1: strain at point 1 ε2: strain at 2 points M: Moment I: Moment of Inertia y is the distance from the neutral surface E: Young's modulus x: location of force point x1: Position of strain gauge 1 x2: Position of strain gauge 2 F: magnitude of applied force The method of claim 1, The micro-force measuring sensor further comprises a cover formed with an opening formed in the space for accommodating the fixed end and the plate and the contact tip and the front portion of the contact tip is exposed to the outside. The method of claim 2, The distance between one side of the opening of the cover and the contact tip is smaller than the maximum deflection value of the plastic deformation of the plate does not occur and the maximum deflection value of the plate does not cause damage to the strain gauge. The method of claim 2, The fixed end is a rubber plate, the fine force measuring sensor, characterized in that the rubber plate is fixed to the cover. The method of claim 1, The reinforcement surface is a fine force sensor, characterized in that bent perpendicular to the measurement surface at both edges of the measurement surface. A fixed end; One end is fixed to the fixed end and has four measurement surfaces extending in one direction from the fixed end, each adjacent measurement surface is formed to be bent 90 degrees to each other, and the four measurement at the end located in the opposite direction of the fixed end A hollow deformation portion having an end surface perpendicular to the surfaces; Two or more notches spaced apart from the fixed end at each edge of the four measurement surfaces; A strain gauge disposed on the measurement surface between the notches spaced apart at the same distance from the fixed end at each edge; And It has a greater rigidity than the deformation portion, and includes a contact tip attached to the center of the end surface of the deformation portion, When a force is applied to one point of the contact tip, the magnitude of the force applied and the position of the point where the force is applied to the micro-force measuring sensor, characterized in that calculated by the following equation. [Equation]

σ: stress ε1: strain at point 1 ε2: strain at 2 points M: Moment I: Moment of Inertia y is the distance from the neutral surface E: Young's modulus x: location of force point x1: Position of strain gauge 1 x2: Position of strain gauge 2 F: magnitude of applied force delete delete

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