TW201623921A - Magnetic encoding device - Google Patents

Abstract

The present invention provides a magnetic encoding device, in which the magnetic encoding device is composed of a single-pair pole magnet, Hall elements, and a microcontroller. The present invention has a simple and reliable structure, low manufacturing cost and less manufacturing difficulties in contrast to the prior art.

Description

Magnetic coding device

The invention relates to signal conversion technology, in particular to a magnetic encoding device for converting an analog magnetic field signal into a digital code.

Encoder is a low-power signal adjustment device commonly used in defense, industrial, vehicle and general commercial signal adjustment applications, such as command transmission components of servos such as actuators in weapon systems, volume of TV audio speakers, and heating and cooling. Machine temperature, light brightness, etc. Any analog signal such as analog or digital control commands and human senses, such as adjustment of sound, brightness, temperature, and air volume, will be applied to such devices.

The current encoder types are roughly classified into mechanical, optical, and electromagnetic types. Among them, the mechanical type generates pulse signals by mechanical contacts, and the resolution per turn is low, and the service life is short. The optical incremental and absolute encoders are the mainstream of the current non-contact encoders. They are large in use, mature in technology, and highly accurate and reliable. They are suitable for machine tools, robots, robot arms, and high-end position servo control systems. . However, optical encoders have large volume and current consumption, and product reliability is greatly affected by the environment (such as dust and moisture).

The optical encoder has two types of grating type and reflective type. The grating type allows the rotating shaft to drive a sheet. The sheet is etched at a certain angular interval, and the LED or the laser source is separated at both ends of the sheet. At the other end, the photosensitive element detects whether the light passes through the grating to generate a pulse train of 0 and 1. This pulse wave is analyzed by a dedicated wafer to understand the angle of rotation of the shaft. At present, two sets of photosensitive elements are commonly used in the industry to generate two sets of pulse trains with a phase difference of 90 degrees, such as the optical encoder AB phase pulse wave diagram shown in FIG. 2, to produce a quadruple resolution effect. Taking a grating of 1000 grids per circle as an example, after four times of analysis, 4000 degrees can be decomposed by 360 degrees, that is, the resolution can reach 0.09 degrees. A reflective optical encoder, or optical scale, emits laser light to a reflecting surface by a set of laser light sources, and the reflecting surface is etched to form a sine wave or a triangular wave shape, and the phase of the reflected light when the laser light strikes at different heights There is a corresponding change, analyze the phase of the reflected light to understand the position of the spot, and then calculate the angle of rotation of the shaft. The reflective optical encoder can be divided into 8-bit (256-frame) or higher in a waveform range. Therefore, its resolution is higher than that of the grating encoder, generally up to 20 bits or higher. On the optical scale, the resolution is up to 0.1 μm . Grating optical encoders are available in both incremental and absolute versions. Absolute encoders have functions such as potentiometers or resolvers, which provide absolute angles of the shaft. This type of product is expensive, and 12-bit products require 12 pairs of light source transmitting and receiving modules. Incremental encoders must be set to zero (usually provided by the Z phase) to provide the relative angle of the shaft to the zero. Reflective encoders are only incremental. Whether it is a reflective or grating optical encoder, the light source is required, and the receiving end is a photosensitive element, which is greatly affected by dust or moisture, and the component also has aging problems. Therefore, optical encoder read heads are generally packaged in IP65 grade and are dust and water resistant. However, the weapon system needs to be considered in a harsh environment for a long time. Once the package of the optical encoder is degraded due to aging, the device may seep into water vapor or dust, and its performance will be affected or even fail. Therefore, general optical encoders are often used in precision machining rooms where the environment is good, and products used in weapon systems or vehicles must be products with a relatively high package level. In addition, the power consumption of the optical encoder is higher than that of a general sensor, and the current required is generally about 50-100 mA, while the power consumption of a general sensor is mostly below 10 mA.

A magnetic tape type magnetic encoder is similar to an optical scale, except that the optical scale generates a signal by laser light, and the magnetic tape type magnetic encoder generates a signal by using a magnetic stripe to demodulate the position or angle signal by magnetic sensing technology. By reading the change of the magnetic field strength, the pair of NS magnetic poles can be cut into tens to hundreds of equal parts. Therefore, the position resolution of such products can reach the μ m level, but the reading head is quite precise and the supply is small. The price is high, the civilian production industry is less used, and the threshold for cutting into technology is quite high.

The rotating shaft of the multi-pole type magnetic encoder drives a magnetic block of a plurality of magnetic poles, and uses two sets of Hall switches to output a pair of pulse waves with a phase difference of 90 degrees. Multi-pole type magnetic encoder products are especially suitable for sound volume adjustment, or control signal adjustment knobs that need to be used for a long time (such as control knobs for weapon system ground equipment). Their characteristics are the same as those of incremental optical encoders. Restricted, non-contact, no wear, long-term use will not be caused by dust or dander by static electricity attached to the brush to produce noise, environmental resistance is better than optical and variable resistance potentiometers. Multi-pole type magnetic encoder has no rotation angle limitation, no internal illumination and photosensitive element, only magnetic block and Hall switch, no component aging problem, in service life, reliability, and The environmental tolerance is superior to optical encoders and potentiometers, and the price is lower than that of optical encoders. However, the existing multi-pole magnetic encoder has several difficulties in manufacturing: the magnetization technology of the multi-magnetic magnetic block has a high threshold, especially for the shrinking of a smaller device, and only a few manufacturers currently have master technologies in the market. Multi-pole magnetic block requires high installation accuracy of the Hall switch. Take Figure 1 as an example. Figure 1 shows the structure of a typical multi-pole magnetic encoder. If it has 4 pairs of magnetic poles, each pair of poles is assigned 90 degrees. Angle (360 degree magnetic pole angle), each magnetic pole is assigned a mechanical angle of 45 degrees (180 degree magnetic pole angle). If two Hall switches are to output a phase difference of 90 degrees, the mechanical angle difference of the installation is 360/8/2. = 22.5 degrees mechanical angle, or 1 degree mechanical angle equivalent to 4 degrees magnetic pole angle, if 12 pairs of magnetic poles, the 90 degree magnetic pole angle is equivalent to 360/24/2 = 7.5 degree mechanical angle, or mechanical angle per 1 degree Corresponding to a magnetic pole angle of 12 degrees, that is, if the relative position error of the two sets of magnetic field sensors is 1 degree during installation, a 12 degree error occurs in the phase difference of the AB phase, with an outer diameter of 16 mm and 12 pairs. Magnetic pole magnetic encoder to calculate, 1 degree mechanical angle converted arc length is 0.140mm, in the group On very strict requirements, high technical threshold processing, easy to popularize application.

In view of the shortcomings of the conventional technology, the present invention provides a magnetic encoding device that uses a pair of magnetic pole magnetic blocks, and combines a Hall element and a microcontroller to form a magnetic encoding device. The structure of the present invention is simple and reliable, and the manufacturing cost and difficulty are compared. Traditional technology is low.

The present invention provides a magnetic encoding device, comprising: a circular magnetic block, which is a single pair of magnetic pole magnetic blocks; a plurality of Hall elements disposed on a circumferential side of the circular magnetic block, the Hall element is The center of the circular magnetic block is a base point and is disposed at an angle of 90 degrees from each other; a microcontroller is connected to the Hall element, and the amount of magnetic field change sensed by the Hall element is converted into a digital coded output, the microcontroller The system can simulate hysteresis switching, so that the magnetic encoding device can stably output the 2-state code; wherein the circular magnetic block rotates with the center of the circular magnetic block as a rotating axis; the circular magnetic block can also have a plurality of pairs of magnetic poles. a magnetic block; the circular magnetic block is a radial magnetizing magnetic block; the Hall element can be a linear Hall-effect device (LHE device), or other analog voltage can be output according to a magnetic field change Device.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

11‧‧‧Circular magnetic block

12‧‧‧ Hall element

13‧‧‧Microcontroller

FIG. 1 is a structural diagram of a typical multi-pole type magnetic encoder.

Figure 2 is an AB phase pulse diagram of an optical encoder.

3 is a structural view of a magnetic encoding device of the present invention.

Fig. 4 is a waveform diagram showing the output of a Hall element of the magnetic encoding device of the present invention.

Figure 5 is a diagram showing the relative relationship of Hall elements of the magnetic encoding device of the present invention.

Fig. 6 is a diagram showing the AB phase waveform of a pulse wave period in which the magnetic encoding device of the present invention is not processed by software.

7 is a 360-degree AB phase output waveform of the magnetic encoding device of the present invention without software processing.

Figure 8 is a graph showing the output characteristics of a Hall digital switch.

FIG. 9 is a comparison diagram of a 4-phase code and a conventional 2-state code A phase waveform according to the present invention.

FIG. 10 is a comparison diagram of a 4-phase code and a conventional 2-state code B-phase waveform according to the present invention.

Figure 11 is a diagram showing the AB phase waveform of the 4-state code of the present invention.

Figure 12 is a diagram showing the state of the four-state encoding of the AB phase single pulse period in the embodiment of the hysteresis point 4 of the present invention.

Figure 13 is a diagram showing the state of the four-state encoding of the AB phase single pulse period in the embodiment of the hysteresis point 1 of the present invention.

Figure 14 is a diagram showing a single pulse period 4 state coded waveform of the B phase backward A phase 54 degree embodiment of the present invention.

Figure 15 is a diagram showing a single pulse period 4 state coded waveform of the B phase leading A phase 45 degree embodiment of the present invention.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

The structure of the magnetic encoding device of the present invention is as shown in FIG. 3, which includes: a circular magnetic block 11 which is a single pair of magnetic pole blocks rotating with the center of the circular magnetic block as a rotating axis; Is disposed on a circumferential side of the circular magnetic block, and the two Hall elements are the circular magnetic block The center of the circle is set at an angle of 90 degrees from each other; a microcontroller 13 is connected to the two Hall elements, and the amount of change in the magnetic field sensed by the two Hall elements is converted into a digital coded output: wherein the microcontroller is The hysteresis switching can be simulated, so that the magnetic encoding device can stably output the 2-state code; the circular magnetic block is a radial magnetizing magnetic block; the Hall element is a linear Hall-effect device (LHE) Device), or other device that outputs an analog voltage based on changes in the magnetic field.

The working principle of the magnetic encoding device of the present invention is: when the circular magnetic block rotates one turn, the output signals of the two Hall elements (LHE) are a pair of sine/cosine waves with a phase difference of 90 degrees, as shown in FIG. 4 (measured Signal), the relative relationship between the two groups of signals is a circle, as shown in Figure 5. Since the output waveform of FIG. 4 is not in the form of the AB phase pulse of the optical encoder of the prior art (as shown in the figure ! The reference source is not found ), the present invention first uses the microcontroller to read the signal of the Hall element. After the rotation angle of the circular magnetic block is solved, the AB phase waveform of 0 or 1 is output according to a preset data table. First, the magnetic encoding device of the present invention has a pulse wave number N _ppr (Pulse Per Round, ppr) per circle, and the circle of FIG. 5 is divided into N _ppr equal parts, or the horizontal axis (angle) in FIG. 4 is divided into N. _{In the ppr} grid, as shown in Fig. 4, the horizontal axis is divided into 12 grids, and each grid will generate a pulse wave, so every 30 degrees is a pulse grid. In each pulse wave (30 degrees), there is a pair of AB phase square waves. The present invention subdivides each pulse wave into a N _gpc grid (Grid per Cycle, gpc), where each pulse wave has N _gpc = For example, if 40 circles have a total of N _ppr = 12 pulse cells, the angle of each cell is 0.75 degrees. If N _gpc = 80, the angle of each cell is 0.375 degrees. The product of N _ppr and N _gpc is the total number of fines (girds) per revolution, which is limited by the number of bits of the Micro Control Unit (MCU) and the signal noise. Generally, a 10-bit microcontroller can resolve up to 1024 analog voltages. The upper limit of N _ppr ×N _gpc is 1024. Therefore, if N _{gpc is} set to 40, the magnetic encoding device is not processed by software. The upper limit of the wave number is 25.6, and the AB phase waveform of each pulse period is as shown in Fig. 6. A total of N _ppr pulse period is generated in a 360 degree cycle, wherein phase A is 1 in the first half of each pulse period, and the second half is It is 0; phase B and phase A are 90 degrees apart (quarter cycle). The pulse grid of every 30 degrees in Fig. 4, the 40 grid points inside are designed as the data of 0 and 1 in Fig. 6. In theory, the magnetic coding device can output N _ppr pulses per revolution. The wave code is shown in Figure 7. However, in fact, the output of the encoder is not fixed at 0 or 1 at certain positions (angles). In the interval where 0 is switched to 1 and 1 is switched to 0, the change may be switched at a high speed, resulting in a coded signal error and noise generation. Directly designing the output of the microcontroller of the present invention to the waveform of Figure 7, there will be no hysteresis characteristics, which can cause problems in use. Generally, the digital output switch has a hysteresis switching function to prevent the output from changing at a high speed between 0 and 1 when the switch position is at the switching point. Taking the Hall digital switch as an example, Figure 8 shows the output characteristic curve of the Hall digital switch. Taking the right picture of Fig. 8 as an example, B _OP > B _RP , both of which are magnetic flux densities. When the magnetic flux density faced by the Hall digital switch is higher than B _OP , the Hall switch output must be 1. When the magnetic flux density is < B _RP , the output must be 0, but when the magnetic flux density is between B _RP and B _OP The output of the Hall switch is related to the state of the previous moment. This design avoids the Hall switch switching between 0 and 1 at high speed at a certain magnetic flux density, causing signal errors. And the hysteresis characteristic value relating to the state before the moment, in addition, also from the point of a switch, as shown in FIG 8, the gap between the B _OP and B _RP B _HYS is the Hysteresis Interval.

The invention realizes the hysteresis switching function by software simulation, and the microcontroller further divides the two states of the original pulse output 2 state code 0 and 1 into four states of 0, 1, 2, and 3, Therefore, it is necessary to find out the position (switching point) from 1 to 0 and from 0 to 1 in the original 2-state code, as shown in the figure 20 in the first 20 (from 1 to 0), and the 40th ( Change from 0 to 1). The embodiment of the method for simulating hysteresis switching of the microcontroller of the present invention comprises: setting a pulse switching point position, if the number of cells per pulse period is N _gpc , the switching point is located at N _gpc /2, and N _gpc As in the previous example, N _gpc =40, the switching points are located at 20 and 40 respectively (since 1 and 0 are half of a cycle pulse, so N _gpc must be set to an even number.); set the length of the hysteresis interval, hysteresis interval length (hysteresis points) N _hys the representative points before and after the switching point where the hysteresis interval N _hys; hysteresis range defined state before and after the switching point, the switching point N _hys (co 2N _hys points) before and after the dot interval (i.e. The set hysteresis interval is redefined as a state other than 0 and 1. If the state of the N _hys point (including the switching point itself) before the switching point or the N _hys point (excluding the switching point itself) after the switching point is 1, the switch will be switched. The state of the interval of the N _hys point (including the switching point itself) before the point is set to 2, and the state of the N _hys point (including the switching point itself) before the switching point or the N _hys point (excluding the switching point itself) after the switching point is 0. N _hys state point before the switching point will be (including switching point itself) is set to 3; and after the switching point of the hysteresis The state between the two is classified into two state codes. For example, in the microcontroller, 2 of the above steps is regarded as 1 and 3 generated by the above steps is regarded as 0. The magnetic encoding device can have a hysteresis switching function and stabilize the output 0. 1 to 2 state code. Please refer to FIG. 9. The upper picture shows the original 2-state A-phase coding (upper figure in FIG. 6). The first half period is 1, and the second half period is 0. After re-arranging according to the 4-state coding method of the present invention, N _{hys is} set to 2 The result of the A-phase 4-state coding is shown in the following figure. If the state that belongs to 1 at 2 points before and after the switching point is 2, and the state belonging to 0 is 3, it will become the 2 state code of the B phase in FIG. 10 and the 4 state code result of the lower diagram of FIG. 10, 4 state. The encoded AB phase waveform is shown in Figure 11. According to the present invention, the microcontroller defines the 2 in the above embodiment as 1 and 3 as 0 in a software simulation manner, so that the magnetic encoding device of the present invention can stably output 0 and 1 of 2 state codes, eliminating When the output pulse is switched from 0 to 1 and 1 is switched to 0, high-speed switching oscillation occurs, resulting in poor noise and signal, and the present invention does not need to provide an additional digital switching circuit, thereby reducing production complexity and manufacturing cost.

The circular magnetic block of the magnetic encoding device of the present invention can also use an axial magnetizing magnetic block. In this configuration, the Hall element (LHE) can be perpendicular to the circuit board, and the axially magnetized magnetic block faces the Huo. When the element (LHE) is used, the Hall element (LHE) sees the most lines of magnetic force, and the other Hall element (LHE) has the least number of lines of magnetic force, but the output of the Hall element (LHE) cannot be as radial as the magnetized block. The configuration generates a set of sin/cos (sin/cos) waveforms, and an external angle correction unit is needed in the calibration procedure to facilitate the coding arrangement of the microcontroller. The external angle correction unit is disposed on the rotation of the circular magnetic block. On the shaft, and connected to the microcontroller, the external angle correction unit provides the rotation angle of the circular magnetic block to the microcontroller to improve the signal precision of the microcontroller. When the magnetic encoding device of the present invention uses a radial magnetizing magnetic block, an external angle correcting unit may be added to meet the demand for a product having high angular precision and resolution. The external angle correction unit can be an optical encoder, a resolver or other angle measuring device.

The magnetic encoding device of the present invention can adjust the hysteresis width. The hysteresis range of the general digital switch is determined by the circuit hardware, and the magnetic encoding device of the present invention can set the AB phase pulse wave by the software built in the microcontroller during production. The hysteresis width of the switching point. It is only necessary to adjust the hysteresis point N _hys when setting. As shown in Fig. 9 and Fig. 10, the number of hysteresis points is 2, so there are 2 grids on the left and right sides of the switching point, and the range of 4 grids is the hysteresis range. In the two graphs, the lattice point N _gpc = 40 in each pulse wave period, and the whole circle has N _ppr = 12 pulse wave grids. Therefore, the angle of each small grid is 0.75 degrees, and the hysteresis range is 3 degrees. 12 is a waveform diagram of a 4-state encoding of an AB phase single pulse period in the embodiment of the hysteresis point 4 of the present invention, and FIG. 13 is a 4-state encoding waveform of an AB phase single pulse period in the embodiment of the hysteresis point 1 of the present invention. Figure. The magnetic encoding device of the present invention can adjust the hysteresis width by the software of the microcontroller without changing the hardware specifications, thereby increasing the production efficiency and saving the processing cost.

Generally, the phase difference of the AB phase of the encoder is fixed to be 90 degrees behind the A phase. The magnetic encoding device of the present invention can set the phase difference of the AB phase by the software built in the microcontroller during production, and only needs to be set when setting. Adjust the phase difference value, and adjust the minimum scale to the angle of 1 grid point. 14 is a single pulse period 4 state coded waveform diagram of the B phase backward A phase 54 degree embodiment of the present invention, and FIG. 15 is a single pulse wave period 4 state coded waveform of the B phase leading A phase 45 degree embodiment of the present invention. In the figure, both of the hysteresis lattice points are 2. The magnetic encoding device of the present invention can set the phase difference of the AB phase by the software of the microcontroller, can adapt to the encoder requirements of various uses, has large design flexibility and wide application range.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

11‧‧‧Circular magnetic block

12‧‧‧ Hall element

13‧‧‧Microcontroller

Claims (10)

A magnetic encoding device includes: a circular magnetic block, which is a single pair of magnetic pole magnetic blocks; a plurality of Hall elements disposed on a circumferential side of the circular magnetic block; and a microcontroller connected to the Hall The component converts the amount of magnetic field change sensed by the Hall element into a digital coded output, and the microcontroller can simulate hysteresis switching so that the magnetic encoding device can stably output the 2-state code. The magnetic encoding device of claim 1, wherein the circular magnetic block is a radially magnetized magnetic block. The magnetic encoding device of claim 1, wherein the circular magnetic block is an axially magnetized magnetic block. The magnetic encoding device according to claim 1, wherein the circular magnetic block rotates with the center of the circular magnetic block as a rotation axis. The magnetic encoding device of claim 1, wherein the circular magnetic block has a plurality of pairs of magnetic poles. The magnetic encoding device according to claim 1, wherein the Hall element is a Linear Hall-effect device (LHE device), or other device capable of outputting an analog voltage according to a change in a magnetic field. . The magnetic encoding device according to claim 1, wherein the Hall element is disposed at a 90 degree angle from each other based on a center of the circular magnetic block. The magnetic encoding device of claim 1, wherein the method for simulating the hysteresis switching of the microcontroller comprises: setting a pulse switching point position; setting a hysteresis interval length; and defining a state of the hysteresis interval before and after the switching point; The state of the hysteresis interval before and after the switching point is classified into a 2-state code. The magnetic encoding device of claim 1, further comprising: an external angle correcting unit that is coupled to the microcontroller, the external angle correcting unit providing rotation of the circular magnetic block Angle to the microcontroller to improve the letter of the microcontroller Number accuracy. The magnetic encoding device of claim 9, wherein the external angle correcting unit is an optical encoder, a resolver or other angle measuring device.