TW201947185A - Linear displacement sensing device capable of accurately obtaining a position of a magnetic test object in a measurement section - Google Patents

Abstract

The present invention discloses a linear displacement sensing device including a first sensing set and a second sensing set, which are arranged in parallel at two ends of the same side of a measurement section in a displacement path of a magnetic test object. The first sensing set includes a first permanent magnet and a first magnetic sensing unit. The second sensing set includes a second permanent magnet and a second magnetic sensing unit. With the composition of the aforementioned components, the first and second permanent magnets respectively have a first variable magnetic field and a second variable magnetic field which partially overlap at the measurement section. The first and second variable magnetic fields will be changed by the displacement of the magnetic test object. The first and second magnetic sensing units sense the aforementioned changes and output first and second variable magneto-electric signals. Through the cross-comparison of the first and second variable magneto-electric signals, the position of the magnetic test object in the measurement section can be accurately obtained.

Description

   Linear displacement sensing device   

The present invention relates to the technical field related to a measuring device, and particularly to a linear displacement sensing device.

Position measurement is an important task in industrial automation. Devices such as computed numerically controlled (CNC) machines, drill bits, robot arms, laser cutters, etc. all require precise position measurement For feedback control. It is desirable to perform position measurement at a high sampling rate so that feedback control can be performed.

For example, common optical encoders are used to measure absolute or relative positions. Typically, a scale with regularly spaced marks is used with a sensor to measure the relative position between two scales. Common optical encoders can be roughly distinguished according to their functions: Incremental linear encoders only measure the relative position of the energy within the marks on the scale.

The relative position encoder continuously tracks the number of traversed marks to determine the relative position.

The absolute position encoder can determine the absolute position, and the absolute position encoder does not require memory and power to store the last position, so it is suitable for some applications. In addition, the absolute position encoder can provide an absolute position at startup, while the relative position encoder typically needs to locate the start point, which may not be practical in some applications.

Knowing the absolute position encoder requires using a unique encoding style to measure each position. Although this encoder uses a ruler, only when the style is changed, it is determined that there is a position change. In this case, the resolution of the position estimate is limited by the resolution of the pattern.

Similarly, the conventional relatively linear encoder uses a mark on an optical detection ruler to measure a linear position, and the mark is fixed at a preset position parallel to the readhead. However, the obtained position resolution is also limited by the mark resolution on the scale. For example, the marks on the scale may be printed at a resolution of 40 micrometers (micron), so the accuracy is limited to 40 micrometers or less, and cannot be higher than 40 micrometers.

In order to improve the resolution, there have been proposals from industry players to use two scales, each of which is aligned in the detection direction and has a periodic scale style, such as white and black marks. The ruler is illuminated from one side, and a photodiode system senses the light that penetrates the two rulers to the other side. As the rulers move relative to each other, the signal of the photodiode is between a maximum And a minimum intensity value. A demodulation process is used to determine the phase of the signal, which is transformed into a relative position that can be restored at a resolution higher than the resolution of the scale.

However, this design only provides relative positions. In order to have the ability to determine the absolute position, some composite encoders use additional scales, which in turn increases the cost and complexity of the system. This composite encoder uses separate scales to measure the incremental position and absolute position, but the composite encoder requires two read heads, the first read head is used to read the incremental position, and The second reading head is used to read the absolute position.

It can be known from the structure and limitations of the above-mentioned conventional encoders that they all need to be equipped with a scale. That is, the magnetic encoder must also be used with a magnetic scale, and they cannot solve the single sensing signal obtained by a single encoder and output at the same time Relative and absolute information needs. In addition, the above-mentioned optical or magnetic encoders are very susceptible to environmental cleanliness, temperature, etc., resulting in loss of accuracy.

In addition, it is known to use a magnetic field change as a method of displacement sensing, which is commonly achieved using a Hall element, such as China CN100376872C (hereinafter referred to as Document 1). The structural feature of Document 1 requires a magnetic element on the object to be measured, and the Hall element response is triggered by the magnetic field generated by the magnetic element. The defects include:

1. Whether the test object can be allowed to install additional magnetic components, if not, reference 1 cannot be implemented.

2. The magnetic field of the magnetic component on the test object is easy to be pulled by the magnetically permeable structure of the mechanism itself, and cannot reach the magnetic quantity sufficient to trigger the Hall element. As a result, the local structure of the test object must be additionally performed during the setting process. Design and improvement to ensure the magnetic quantity of magnetic components.

3. The test object is provided with magnetic components, which is easy to magnetically attract iron filings when applied to metal processing.

4. Hall elements are easily distorted by environmental interference, such as to compensate for non-linear temperature drift.

5. The Hall element has a limited bandwidth; when measuring a small range of current, a large bias voltage is required, which will cause errors; it is susceptible to external magnetic fields.

In view of the problems and deficiencies of the above-mentioned conventional techniques, the main purpose of the present invention is to provide a linear displacement sensing device, which, by the design of the structure, provides the demand for the micro motion sensing of the magnetically permeable object.

Another object of the present invention is to provide a linear displacement sensing device, which overcomes the defects in the structure of conventional optical encoders or magnetic encoders and the limitation in the provision of measurement information through the design of the structure.

According to the above object of the present invention, a linear displacement sensing device is provided. The linear displacement sensing device includes a first sensing group and a second sensing group, which are arranged in parallel in a displacement path of a magnetically permeable measuring object, and the two ends of the measurement section on the same side. The first sensing group includes a first permanent magnet and a first magnetic sensing unit. The second sensing group includes a second permanent magnet and a second magnetic sensing unit. With the composition of the above components, the first and second permanent magnets are respectively located in the measurement section, and have one of the first and second changing magnetic fields that partially overlap, and the first and second changing magnetic fields are subject to the displacement of the magnetically measured object When it changes, the first and second magnetic sensing units sense the change and output a first and second variable magnetic-electrical signal. Through the cross-comparison of the first and second variable magnetic-electrical signals, the magnetically permeable object is accurately measured. Test the position in the segment.

100‧‧‧ linear displacement sensing device

10‧‧‧The first sensing group

12‧‧‧The first permanent magnet

122‧‧‧The first changing magnetic field

124‧‧‧first reference magnetic field

20‧‧‧Second sensing group

22‧‧‧Second permanent magnet

222‧‧‧Second Variable Magnetic Field

224‧‧‧second reference magnetic field

M‧‧‧ Magnetically Measured Object

P‧‧‧Displacement path

PS‧‧‧Measurement Section

V1‧‧‧The first magnetic sensing unit

V2‧‧‧Second magnetic sensing unit

CS1‧‧‧First change magnetic signal

CS2‧‧‧Second Change Magnetic Signal

0‧‧‧ origin

FIG. 1 is a schematic diagram of an embodiment of the present invention.

Figure 2 is a schematic diagram of the first and second variable magnetic-electric signals of the present invention.

The following further describes the embodiments of the linear displacement sensing device of the present invention with reference to related drawings. In order to facilitate understanding of the embodiments of the present invention, the same components are denoted by the same symbols in the following description.

Please refer to FIG. 1 and FIG. 2. The linear displacement sensing device 100 of the present invention includes a first and a second sensing group 10 and 20, which are arranged in parallel in a displacement path P of a magnetically permeable measurement object M. Both ends of the measurement section PS on the same side are used to measure the displacement of the magnetically-measured object M at the same time.

The first sensing group 10 includes a first permanent magnet 12 and a first magnetic sensing unit V1, and the second sensing group 20 also includes a second permanent magnet 22 and a second magnetic sensing Unit V2.

In the first permanent magnet 12, the N extreme and the S extreme concentrically intersect with the displacement path P of the magnetically permeable measurement object M, and the N permanent pole of the first permanent magnet 12 is adjacent to the displacement path of the magnetically permeable measurement object M. P. The first magnetic field lines of the first permanent magnet 12 moving along the S extreme to the N extreme form a first variable magnetic field 122 and a first reference magnetic field 124 at opposite positions on the outer peripheral side of the first permanent magnet 12 respectively. The magnetic field 12 partially overlaps the measurement section PS in the displacement path P of the magnetically permeable measurement object M. During implementation, it is preferable that the overlapping portion of the first variable magnetic field 12 and the measurement section PS is not less than 50% of the total length of the measurement section PS.

In addition, the first variable magnetic field 122 will form a magnetic traction on the first variable magnetic field 122 due to the distance between the magnetically permeable object M and the first permanent magnet 12, thereby changing the magnetic force change of the first variable magnetic field 122.

In addition, the first reference magnetic field 124 is normally in a stable state relative to the first fluctuating magnetic field 122, and is not easily changed by the magnetically-measuring object M, and the first reference can also be made by the structure design of the magnetic convergence The magnetic field 124 converges to reduce the range of the first reference magnetic field 124 (intensify the strength of the first reference magnetic field 124), avoid being changed by being pulled by the magnetically guided measurement object M, and ensure the stability of the first reference magnetic field 124. (The first reference magnetic field 124 and its application are not the focus of this case, so I will not repeat them here)

In the second permanent magnet 22, the N extreme and the S extreme concentrically intersect with the displacement path P of the magnetically permeable test object M, and the second permanent magnet 22 is adjacent to the displacement path P of the magnetically permeable measurement object M . The second magnetic field line of the second permanent magnet member 22 moving along the S extreme end toward the N extreme end forms a second variable magnetic field 222 and a second reference magnetic field 224 at opposite positions on the outer peripheral side of the second permanent magnet part 22, respectively. The fluctuating magnetic field 222 partially overlaps the measurement section PS in the displacement path P of the magnetically permeable measurement object M. During implementation, the overlapping part of the second variable magnetic field 222 and the measurement section PS is preferably not less than 50% of the total length of the measurement section PS.

In addition, the second variable magnetic field 222 will form a magnetic traction on the second variable magnetic field 222 due to the distance between the magnetically permeable measurement object M and the second permanent magnet 22, thereby changing the magnetic force change of the second variable magnetic field 222.

In addition, compared with the second variable magnetic field 222, the second reference magnetic field 224 is in a stable state and is not easily changed by the magnetically-measuring object M, and the second reference magnetic field can also be made by the structural design of magnetic convergence 224 converges to reduce the range of the second reference magnetic field 224 (intensify the intensity of the second reference magnetic field 224), to avoid being changed by being pulled by the magnetically permeable measurement object M, and to ensure the stability of the second reference magnetic field 224. (The second reference magnetic field 224 and its application are not the focus of this case, so I will not repeat them here.)

The first and second magnetic sensing units V1 and V2 are the same components and include a magnetic induction circuit composed of at least one magnetoresistive element. When implemented, this case excludes the use of Hall elements.

The first magnetic sensing unit V1 is disposed between the displacement path P of the magnetically permeable measuring object M and the N extreme end of the first permanent magnet piece 12 so as to apply a first variable magnetic field to the first permanent magnet piece 12. The magnetic change of 122 (or the first reference magnetic field 124) is used for the sensing group, and a first variable magnetic signal CS1 (or the first reference magnetic signal, not shown in the figure) is output according to the sensing.

The second magnetic sensing unit V2 is disposed between the displacement path P of the magnetically permeable measurement object M and the N extreme end of the second permanent magnet member 22, so as to meet the second changing magnetic field of the second permanent magnet member 22. The magnetic change of 222 (or the second reference magnetic field 224) is used for the sensing group, and a second variable magnetic signal CS2 (or the second reference magnetic signal, not shown in the figure) is output according to the sensing.

Therefore, the above is an introduction to the components and assembly methods of a linear displacement sensing device according to a preferred embodiment of the present invention, and the operating characteristics of the embodiments of the present invention are described below.

First, please refer to Figs. 1 and 2. As shown in Figs. 1 and 2, the position of the magnetically susceptible object M being displaced at each point of the measurement section PS will change the first formed by the first and second permanent magnets 12, 24. The second and second variable magnetic fields 122 and 222 form different degrees of magnetic traction, and the changes in the first and second variable magnetic fields 122 and 222 will be sensed by the first and second magnetic sensing units V1 and V2, respectively. The measuring units V1 and V2 convert the changes of the first and second variable magnetic fields 122 and 222 into electrical signals respectively to output the first and second variable magnetic and electrical signals CS1 and CS2.

Please refer to Figure 2. We use the following graph to explain the displacement of the magnetically susceptible measurement object M at each point of the measurement section PS, which has a magnetic traction effect on the first and second variable magnetic fields 122 and 222, resulting in the first Second, the change of the relationship between the change of the magnetic and electrical signals CS1 and CS2.

The X axis in Fig. 2 is regarded as the coordinate of several axes (also can be regarded as the measurement section PS), which has an origin of 0, and the positive or negative value in the coordinate value depends on the magnetically measured object. Decide on which side of M the origin is. Through such a definition, we can express the coordinates of the movement through the origin 0 in the direction of the first permanent magnet 12 as a positive value (the larger the number, the closer it is). On the contrary, the coordinates of the movement toward the second permanent magnet 22 after passing through the origin 0 are represented by a negative value (the larger the number, the closer it is). In addition, the Y-axis system in the second figure indicates the strength of the first and second variable magneto-electric signals CS1 and CS2 (the larger the number, the stronger it is).

The definition of the origin 0 means that when the magnetically susceptible object M is displaced in the middle of the measurement section PS, the magnetic traction force of the magnetically susceptible object M to the first and second variable magnetic fields 122 and 222 is the same ( As shown in the figure, the Y axis is at position 5), so the first and second variable magnetic and electrical signals CS1 and CS2 output by the first and second magnetic sensing units V1 and V2 are approaching the same.

If the magnetically-measuring object M approaches the first variable magnetic field 122 of the first permanent magnet 12, the first variable magnetic-electrical signal CS1 will have a gradually increasing curve, and the magnetic traction of the second variable magnetic field 222 gradually Weakening, so the second change magnetic signal CS2 will show a gradually weakening curve. On the contrary, if the magnetically permeable test object M moves toward the second permanent magnet 22, the related first and second variable magnetic and electrical signals CS1 and SC2 appear, which is opposite to the above result.

Using the combination of the first and second variable magnetic and electrical signals CS1 and CS2 (continuous curves) of the magnetically susceptible object M located at each point in the measurement section PS, it can be defined (encoded) at the back end as required, and the guide can be clearly obtained The absolute position of the magnetic measurement object M in the measurement section PS, or the relative position of the magnetic measurement object M with respect to the first and second magnetic sensing units V1 and V2. Also, because each point or displacement can be coded, the back end can take each point as feedback for control, instead of just being used for switching.

Furthermore, the cross-comparison of the first and second variable magneto-electric signals CS1 and CS2 is further used to more accurately obtain the displacement and position of the magnetically permeable measurement object M.

In the embodiment of the present invention, the magnetically permeable test object M can be defined (encoded) at each position in the measurement section PS. Therefore, when the power is interrupted and re-replyed, the magnetically permeable test object M need not return to the original At 0, the back-end device can still determine whether the magnetically permeable object M is in any position in the measurement section PS through the first and second variable magneto-electric signals CS1 and CS2.

The above description is only a preferred embodiment of the present invention, and is intended to clarify the features of the present invention, and is not intended to limit the scope of the embodiments of the present invention. Equal changes made by those skilled in the art based on the present invention , And changes well known to those skilled in the art, should still fall within the scope of the present invention.

Claims (4)

    A linear displacement sensing device includes a first and a second sensing group arranged in parallel on one end of a measurement section in a displacement path, and is used for displacement measurement of a magnetically permeable object. Wherein, the first sensing group includes a first permanent magnet and a first magnetic sensing unit; the first permanent magnet whose N extreme and S extremes are concentric to the displacement path, and the first permanent The N extreme of a permanent magnet piece is adjacent to the displacement path, and the first permanent magnetic piece forms a first magnetic field on the outer peripheral side of the first permanent magnet piece with the first magnetic field line moving along the S extreme toward the N extreme, so that the A fluctuating magnetic field partially overlaps the measurement section, and the first fluctuating magnetic field will be magnetically pulled by the distance between the magnetically permeable measurement object M; the first magnetic sensing unit includes at least one magnetoresistive element The formed magnetic induction circuit is disposed between the displacement path and the first permanent magnet N extreme pole, so as to sense the magnetic change of the first changing magnetic field, and output a first changing magnetic-electrical signal according to the sensing. ; The second sensing group includes a second permanent magnet and a second magnetic sensing unit ; The second permanent magnet, whose N extreme and S extreme are concentric and orthogonal to the displacement path, and the N extreme of the second permanent magnet is adjacent to the displacement path, and the second permanent magnet is along the S extreme toward N The second magnetic field line of extreme motion forms a second fluctuating magnetic field on the outer peripheral side of the second permanent magnet, so that the second fluctuating magnetic field partially overlaps the measurement section and the second fluctuating magnetic field, and the second fluctuating magnetic field will The magnetic traction is formed by the distance between the magnetically permeable measurement object; the second magnetic sensing unit includes a magnetic induction circuit composed of at least one magnetoresistive element, and is arranged on the displacement path and the second permanent magnet N Between extremes, the magnetic change of the second variable magnetic field is sensed, and a second variable magneto-electric signal is output according to the sensing. Among them, the back end is provided as a countermeasure through the changes of the first and second variable magnetic-electric signals. Feedback of the micro-displacement of the magnetically measured object in the measurement section.         According to the linear displacement sensing device described in the first item of the patent application scope, wherein the overlapping portion of the first and second variable magnetic fields and the measurement section is 60% to 100% of the total length of the measurement section.         The linear displacement sensing device according to item 1 of the scope of patent application, wherein the first magnetic field line of the first permanent magnet moving along the S extreme to the N extreme forms a first datum on the outer peripheral side of the first permanent A magnetic field, and a position where the first reference magnetic field is formed is opposite to the first fluctuating magnetic field.         The linear displacement sensing device according to item 1 of the scope of the patent application, wherein the second magnetic field line of the second permanent magnet moving along the S extreme to the N extreme forms a second reference on the outer peripheral side of the second permanent A magnetic field, and a position where the first reference magnetic field is formed is opposite to the second fluctuating magnetic field.