TWI657228B - Linear displacement sensing device - Google Patents

Abstract

The invention discloses a linear displacement sensing device, which comprises a first and second sensing groups, which are arranged in parallel in a displacement path of a magnetically conductive object to be measured, and both ends of the same side of the measuring section are measured. 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 magnet members respectively measure the section and have one of the first and second varying magnetic fields partially overlapped, and the first and second varying magnetic fields are displaced by the magnetically conductive object to be measured. And changing, the first and second magnetic sensing units sense the change and output a first and second variable magnetic signals, and accurately obtain the magnetic conductive object through the first and second alternating magnetic signals. The position in the measurement section.

Description

Linear displacement sensing device

The invention relates to the technical field related to a measuring device, in particular to a linear displacement sensing device.

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

For example, a common optical encoder is used to measure absolute or relative position. Typically, a scale with regularly spaced marks is used with the sensor to measure the relative position between the two targets. Common optical encoders are roughly distinguishable by function: Incremental linear encoders only measure the relative position within the mark on the scale.

The relative position encoder continuously tracks the number of traverse 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 final position, so it is suitable for some applications. In addition, the absolute position encoder system can An absolute position is provided at startup, while a relative position encoder typically needs to locate a start point, which may not be practical in some applications.

Conventional absolute position encoders require a unique coding pattern to measure each position. Although such an encoder uses a scale, it is determined that there is a change in position only when the style is changed. In this case, the resolution of the position estimate is limited by the resolution of the pattern.

Similarly, a conventional relative linear encoder utilizes a mark on an optical detection scale to measure a linear position that is fixed to a predetermined position parallel to the readhead. However, the resulting position resolution is also limited by the degree of mark resolution on the scale. For example, the marking on the scale may be printed at a resolution of 40 microns, so the accuracy is limited to less than 40 microns (micron) and not higher than 40 microns.

In order to improve the resolution, the manufacturer has proposed a lesson plan, using two rulers, each of which is aligned in the detection direction and has a periodic scale pattern, such as white and black marks. The scale is illuminated by one side, and a photodiode system senses light that penetrates the two scales to the other side. As the scale moves relative to each other, the signal of the photodiode is between a maximum And a change between the minimum intensity values. A demodulation process is used to determine the phase of the signal, which is converted to a relative position that can be restored with a resolution above the scale resolution.

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

It can be seen from the structure and limitation of the above-mentioned conventional encoder that a scale is required, so that the magnetic code encoder also needs to be used with a magnetic scale, and the single sensing signal obtained by using a single encoder cannot be solved, and the output is simultaneously output. The need for multiple information such as relative position and absolute position. In addition, the above optical or magnetic encoders are very susceptible to environmental cleanliness, temperature, etc., resulting in loss of accuracy.

In addition, it is conventional to use a magnetic field change as a method of displacement sensing, which is commonly achieved by using a Hall element, such as Chinese CN100376872C (hereinafter referred to as Document 1). The structural feature of Document 1 must be provided with a magnetic element on the object to be measured, and the magnetic field generated by the magnetic element triggers the Hall element response, and the missing includes:

1. Whether the measured object can permit additional mounting of magnetic components, if not, then Document 1 cannot be implemented.

2. The magnetic component on the object to be tested is easily pulled by the magnetic structure of the mechanism itself, and cannot reach the magnetic quantity sufficient to trigger the Hall element, so that additional local structure of the measured object must be performed during the setting process. Designed and improved to ensure the magnetic quantity of the magnetic components.

3. The measured object is provided with a magnetic element, which is easy to magnetically attract iron filings when used in metal processing.

4. Hall elements are susceptible to distortion due to environmental disturbances, such as compensation for nonlinear temperature drift.

5. Hall element bandwidth is limited; when measuring small-scale current, it is required to use large bias voltage, which will cause error; it is susceptible to external magnetic field.

In view of the above problems and deficiencies of the prior art, the subject of the present invention The object is to provide a linear displacement sensing device that provides a requirement for micro motion sensing of a magnetically permeable object by structural design.

Another object of the present invention is to provide a linear displacement sensing device which overcomes the limitations of the conventional optical encoder or magnetic encoder structure and the measurement information provided by the design of the structure.

According to the above object of the present invention, a linear displacement sensing device is provided, comprising a first and second sensing groups, which are arranged in parallel in a displacement path of a magnetically conductive object to be measured, and both ends of the same side of the measuring section. 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 magnet members respectively measure the section and have one of the first and second varying magnetic fields partially overlapped, and the first and second varying magnetic fields are displaced by the magnetically conductive object to be measured. And changing, the first and second magnetic sensing units sense the change and output a first and second variable magnetic signals, and accurately obtain the magnetic conductive object through the first and second alternating magnetic signals. The position in the measurement section.

100‧‧‧linear displacement sensing device

10‧‧‧First Sensing Group

12‧‧‧First permanent magnet

122‧‧‧First variable 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 conductive test object

P‧‧‧displacement path

PS‧‧‧Measurement section

V1‧‧‧First Magnetic Sensing Unit

V2‧‧‧Second magnetic sensing unit

CS1‧‧‧First variable magnetoelectric signal

CS2‧‧‧Second variable magnetoelectric signal

0‧‧‧ origin

Figure 1 is a schematic view of an embodiment of the invention.

Fig. 2 is a schematic view showing the first and second variations of the magnetoelectric signals of the present invention.

In the following, the embodiment of the linear displacement sensing device of the present invention will be further described with reference to the related drawings. In order to facilitate the understanding of the embodiments of the present invention, the same components are denoted by the same reference numerals.

Please refer to Figures 1 to 2 for the linear displacement sensing device of the present invention. The first and second sensing groups 10 and 20 are disposed in parallel with the two ends of the measuring section PS in the displacement path P of the magnetically conductive object M for simultaneously guiding the magnetic field. The measured object M is subjected to displacement measurement.

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.

The first permanent magnet 12 has its N-extreme and S-extreme concentricity perpendicular to the displacement path P of the magnetically-measured object M, and the N-extreme of the first permanent magnet 12 is adjacent to the displacement path of the magnetically-measured object M P. a first variable magnetic field 122 and a first reference magnetic field 124 are formed on the outer peripheral side of the first permanent magnet 12 at a position opposite to the first magnetic field of the first permanent magnet 12; The magnetic field 12 partially overlaps with the measurement section PS in the displacement path P of the magnetically conductive object M. In practice, the portion of the first varying magnetic field 12 overlapping the measuring section PS is preferably not less than 50% of the total length of the measuring section PS (for example, 60% to 100%).

The first varying magnetic field 122 forms a magnetic traction on the first varying magnetic field 122 due to the proximity of the magnetically conductive object M to the first permanent magnet 12, thereby changing the magnetic force change of the first varying magnetic field 122.

In addition, the first reference magnetic field 124 is normally in a stable state with respect to the first variable magnetic field 122, is not easily disturbed by the interference of the magnetic conductive object M, and can also be designed to achieve the first reference by magnetic convergence. The magnetic field 124 converges to narrow the range of the first reference magnetic field 124 (enhance the intensity of the first reference magnetic field 124), avoiding being changed by the traction of the magnetically conductive object M, and ensuring 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 it)

The second permanent magnet 22 has its N-extreme and S-extreme concentricity perpendicular to the displacement path P of the magnetically-measured object M, and the N-extreme of the second permanent magnet 22 Adjacent to the magnetically conductive object M displacement path P. The second magnetic field of the second permanent magnet 22 moves along the S pole to the N pole, and a second varying magnetic field 222 and a second reference magnetic field 224 are formed at opposite positions on the outer peripheral side of the second permanent magnet 22; The variable magnetic field 222 partially overlaps with the measurement section PS in the displacement path P of the magnetically conductive object M. In implementation, the overlapping portion of the second varying magnetic field 222 and the measuring section PS is preferably not less than 50% of the total length of the measuring section PS (for example, 60% to 100%).

The second varying magnetic field 222 forms a magnetic traction on the second varying magnetic field 222 due to the proximity of the magnetically conductive object M to the second permanent magnet 22, thereby changing the magnetic force change of the second varying magnetic field 222.

In addition, the second reference magnetic field 224 is opposite to the second variable magnetic field 222, and the normal state is in a stable state, and is not easily disturbed by the magnetic conductive object M, and can be arbitrarily changed by the magnetic convergence structure. The 224 converges to reduce the range of the second reference magnetic field 224 (enhance the intensity of the second reference magnetic field 224) to avoid being changed by the pulling of the magnetically conductive object M, ensuring 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 it)

The first and second magnetic sensing units V1, V2 are the same members, and comprise a magnetic sensing circuit composed of at least one magnetoresistive element. In the implementation, the case excludes the use of Hall elements.

The first magnetic sensing unit V1 is disposed between the displacement path P of the magnetically conductive object M and the N terminal of the first permanent magnet 12, and the first variable magnetic field of the first permanent magnet 12 A magnetic change of 122 (or the first reference magnetic field 124) is performed on the sensing group, and a first varying magnetic signal CS1 (or a first reference magnetic signal, not shown) is outputted according to the sensing.

The second magnetic sensing unit V2 is disposed between the displacement path P of the magnetically conductive object M and the N terminal of the second permanent magnet 22, The magnetic change of the second varying magnetic field 222 (or the second reference magnetic field 224) of the magnetic member 22 is subjected to a sensing group, and a second varying magnetic signal CS2 is outputted according to the sensing (or the second reference magnetic signal, the figure is not Show).

Therefore, the above is the introduction of the components and the assembly manners of the linear displacement sensing device according to a preferred embodiment of the present invention. The actuation features of the embodiments of the present invention are further described below.

First, as shown in Figures 1 and 2, the displacement of the magnetically conductive object M at each position of the measurement section PS is the first to form the first and second permanent magnets 12, 24. The two varying magnetic fields 122, 222 form different degrees of magnetic traction, and the changes of the first and second varying magnetic fields 122, 222 are respectively perceived by the first and second magnetic sensing units V1, V2, respectively, through the first and second magnetic senses. The measuring units V1 and V2 respectively convert the changes of the first and second varying magnetic fields 122 and 222 into electrical signals to output the first and second variable magnetic signals CS1 and CS2.

Referring to FIG. 2, we illustrate the magnetic displacement of the first and second varying magnetic fields 122, 222 by the displacement of the magnetically-measured object M at each point of the measuring section PS through the following graph, resulting in the first And change the relationship between the magnetoelectric signals CS1 and CS2.

In the X-axis of Figure 2, we regard it as a number axis coordinate (which can also be regarded as the measurement section PS), which has an origin 0, and the positive or negative value in the coordinate value depends on the magnetic permeability object. M is determined on which side of the origin. Through such a definition, we can express the coordinates moving in the direction of the origin 0 to the first permanent magnet 12 with a positive value (the larger the number, the closer it is). Conversely, the coordinates moving toward the second permanent magnet 22 through the origin 0 are represented by a negative value (the closer the number is, the closer it is). Further, the Y-axis in Fig. 2 indicates the strength of the first and second variable magneto-optical signals CS1 and CS2 (the larger the number, the stronger).

The definition of the origin 0 refers to the displacement of the magnetically sensed object M. When the middle portion of the measurement section PS is measured, the magnetic traction force of the first and second variable magnetic fields 122, 222 is the same for the first and second variable magnetic fields 122, 222 (the Y-axis 5 position in the figure), so the first and second magnetic sensing units The first and second varying magneto-optical signals CS1 and CS2 of the V1 and V2 outputs approach the same, and this position is regarded as the origin 0.

If the magnetically conductive object M approaches the first varying magnetic field 122 of the first permanent magnet 12, the first varying magnetic signal CS1 will gradually increase, and the magnetic traction of the second varying magnetic field 222 gradually. Weakening, so the second variable magneto-optical signal CS2 will be gradually weakened. Conversely, if the magnetically conductive object M moves toward the second permanent magnet 22, the associated first and second varying magnetic signals CS1, SC2 are present, as opposed to the above result.

The first and second variable magnetic signals CS1 and CS2 (continuous curves) of the magnetically sensed object M located at each point in the measurement section PS are defined (coded) at the back end according to requirements, and the guide can be clearly obtained. The absolute position of the magnetic object to be measured M in the measurement section PS, or the relative position of the magnetic property object M relative to the first and second magnetic sensing units V1, V2. Also, since each point or displacement can be encoded, the backend can take each point as a feedback of control, and is no longer just a simple switch.

Furthermore, by further utilizing the intersection ratio of the first and second varying magneto-optical signals CS1 and CS2, the displacement amount and position of the magnetically conductive object M are more accurately obtained.

In the embodiment of the present invention, the magnetically conductive object to be tested M can be defined (encoded) at each point in the measurement section PS, so that when the power is interrupted and then returned again, the magnetically conductive object M does not need to be returned to the original. At point 0, the back-end device can still determine the magnetically-measured object M in any position in the measurement section PS through the first and second variable magnetic signals CS1 and CS2.

The above description is only the 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. </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt;

Claims (4)

A linear displacement sensing device includes a first and a second sensing group disposed on one side of the same side of one of the measuring sections in parallel, for performing displacement measurement on a magnetically conductive object The first sensing group includes a first permanent magnet member and a first magnetic sensing unit; the first permanent magnet member has an N-extreme and S-extreme concentricity orthogonal to the displacement path, and the a N-extreme portion of a permanent magnet member is adjacent to the displacement path, and the first permanent magnet member forms a first varying magnetic field on the outer peripheral side of the first permanent magnet member along a first magnetic line of force moving along the S-extreme toward the N-pole, such that the first magnetic field a variable magnetic field partially overlaps with the measuring section, and the first varying magnetic field is magnetically pulled by a distance between the magnetically conductive analytes M; the first magnetic sensing unit includes at least one magnetoresistive element The magnetic sensing circuit is disposed between the displacement path and the N-terminal of the first permanent magnet, and senses a magnetic change of the first variable magnetic field, and outputs a first variable magnetic signal according to the sensing The second sensing group includes a second permanent magnet and a second magnetic sensing unit The second permanent magnet member has an N-extreme concentric with the S-extreme intersection in the displacement path, and the N-extremity of the second permanent magnet member is adjacent to the displacement path, and the second permanent magnet member is along the S-extreme N a second magnetic field line of the extreme motion forms a second varying magnetic field on the outer peripheral side of the second permanent magnet, such that the second varying magnetic field partially overlaps the measuring section and the second varying magnetic field, and the second varying magnetic field Magnetic traction is formed by the distance between the magnetically conductive objects; the second magnetic sensing unit includes at least one magnetoresistive element a magnetic sensing circuit disposed between the displacement path and the second permanent magnet N pole, sensing a magnetic change of the second varying magnetic field, and outputting a second varying magnetic signal according to the sensing; The back end is provided as a feedback of the trace displacement of the magnetically conductive object to the measurement section through the change of the first and second variable magnetic signals. The linear displacement sensing device of claim 1, wherein the overlapping portion of the first and second varying magnetic fields and the measuring segment is 60% to 100% of the total length of the measuring segment. The linear displacement sensing device of claim 1, wherein the first permanent magnet member moves along the first magnetic field line of the S pole toward the N pole, and forms a first reference on the outer peripheral side of the first permanent magnet member. a magnetic field, and the first reference magnetic field is formed at a position opposite to the first varying magnetic field. The linear displacement sensing device of claim 1, wherein the second permanent magnet member has a second magnetic field line moving along the S pole toward the N pole, and a second reference is formed on the outer peripheral side of the second permanent magnet member. a magnetic field, and the first reference magnetic field is formed at a position opposite to the second varying magnetic field.