Reflection absolute type angular displacement sensor and measurement method

Abstract

The invention discloses a reflection absolute type angular displacement sensor and a measurement method. The reflection absolute type angular displacement sensor comprises a stator base body, excitation electrodes on the stator base body, a rotor base body and induction electrodes on the rotor base body. The surface, facing the stator base body, of the rotor base body is covered with a light absorption insulating layer covering the excitation electrodes, two circles of reflective patterns are arranged on the light absorption insulating layer, and the two circles of reflective patterns are different and are coprime in number. And the area change of each reflective pattern along the circumference and the corresponding angle change form a function relationship. A light-emitting module and two sets of photoelectric sensors are arranged on the surface, facing the rotor base body, of the stator base body, the light-emitting module is used for sending light beams to the two circles of reflective patterns, and the photoelectric sensors are used for collecting light intensity reflected by the reflective patterns and outputting obtained photoelectric signals to a signal processing circuit. The photoelectric sensing principle is adopted for rough measurement, the transverse size of the sensor can be greatly reduced, fine measurement and rough measurement do not interfere with each other, the measurement precision is high, and implementation is easy.

Description

Technical Field

[0001] This invention relates to precision angular displacement measurement, specifically to a reflective absolute angular displacement sensor and measurement method. This sensor obtains absolute position using different methods for fine and coarse measurements, and belongs to the field of precision measurement and sensing technology. Background Technology

[0002] High-precision and large-diameter angular displacement sensors are widely used in precision equipment, such as precision machine tools, military weapons, automobiles, medical devices, and high-precision worktables, serving as key functional units in these devices. Absolute sensors enable absolute displacement measurement, effectively solving the problem of data loss during power outages. They also allow for fully closed-loop control and feedback, reducing interference from external factors such as temperature, and improving sensor measurement accuracy, thus broadening their application range.

[0003] Currently, electric field-type angular displacement sensors mainly achieve absolute measurement by using differential pole or coprime methods. Although absolute measurement is achieved, there are also drawbacks.

[0004] 1) When using differential or coprime to achieve absolute positioning, two rings of sensors are required. This requires setting two rings of excitation electrodes and two rings of induction electrodes on the stator base and rotor base respectively, which increases the size of the sensor, especially the lateral dimension of the sensor, which is not conducive to compactness and miniaturization.

[0005] 2) When using a differential pole structure, the difficulty of achieving absolute positioning around a large circle will increase significantly, mainly due to the positioning error. N and N-1 are the number of cycles for the two sensors, respectively. As the sensor diameter increases, the number of cycles required increases, the requirements for positioning accuracy become higher, and the more difficult it becomes to achieve.

[0006] 3) When absolute positioning is achieved by using differential polarity or coprime polarity, there is mutual interference between the two sensors, which will affect the measurement accuracy and is not conducive to high-precision large-size measurement. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a reflective absolute angular displacement sensor and measurement method. The present invention can significantly reduce the lateral size of the sensor, and the fine and coarse measurements do not interfere with each other, resulting in high measurement accuracy, simple structure, and ease of implementation.

[0008] The technical solution of this invention is implemented as follows:

[0009] A reflective absolute angular displacement sensor includes a rotor base and a stator base arranged in parallel with a gap between them. A ring of excitation electrodes is uniformly arranged circumferentially on the surface of the stator base facing the rotor base. A ring of sensing electrodes is uniformly arranged circumferentially on the surface of the rotor base facing the stator base, with the sensing electrodes on the rotor base directly opposite the excitation electrodes on the stator base. A concentric annular light-absorbing insulating layer, covering all the sensing electrodes, is placed on the surface of the rotor base facing the stator base. Two rings of uniformly arranged circumferential electrodes are arranged on the light-absorbing insulating layer. The reflective pattern is arranged in a circular pattern; each ring of reflective pattern consists of several identical reflective patterns connected end to end, and the two rings of reflective patterns are different and coprime in number; the area of ​​each reflective pattern along the circumference is a function of the corresponding angle change; a light-emitting module and two sets of photoelectric sensors are provided on the surface of the stator base facing the rotor base, and the two sets of photoelectric sensors are respectively facing the two rings of reflective patterns; the light-emitting module is used to send light beams to the two rings of reflective patterns, and the photoelectric sensors are used to collect the light intensity reflected by the reflective patterns and output the obtained photoelectric signals to the signal processing circuit.

[0010] Furthermore, each group of photoelectric sensors consists of two sensors located on the same circumference. The angle formed by the line connecting the two photoelectric sensors in each group to the center of the stator base is equal to 1 / 4 of the circumferential angle of the single reflective pattern corresponding to that group of photoelectric sensors.

[0011] Furthermore, the functional relationship is a sine or cosine functional relationship.

[0012] Furthermore, on the surface of the rotor base facing the stator base, two inner and outer rings of induction signal emitting rings are arranged around the outer ring of the induction electrodes. The two rings of induction signal emitting rings are respectively connected to the two induction phases to emit the induction signals generated by the corresponding induction phases. The light-absorbing insulating layer covers all induction electrodes and the two rings of induction signal emitting rings. On the surface of the stator base facing the rotor base, two inner and outer rings of induction signal receiving rings are arranged around the outer ring of the excitation electrodes. The two rings of induction signal receiving rings correspond one-to-one with the two rings of induction signal emitting rings and are used to receive the induction signals emitted by the corresponding induction signal emitting rings.

[0013] Furthermore, the two sets of photoelectric sensors are located on two loops of induction signal receiving rings, respectively.

[0014] Furthermore, the excitation electrode is composed of 4k rectangular excitation electrodes of the same size and with an electrode spacing of θ1, evenly arranged along the circumference; every four adjacent excitation electrodes form a group, and the 4k excitation electrodes form k groups; in each group, the excitation electrodes in the first position are connected together to form excitation phase A, the excitation electrodes in the second position are connected together to form excitation phase B, the excitation electrodes in the third position are connected together to form excitation phase C, and the excitation electrodes in the fourth position are connected together to form excitation phase D; the sensing electrode is composed of 2k double sinusoidal electrodes of the same size and with an electrode spacing of 2θ1, evenly arranged along the circumference; every two adjacent sensing electrodes form a group, and the 2k sensing electrodes form k groups; in each group, the sensing electrodes in the first position are connected together to form sensing phase A, and the sensing electrodes in the second position are connected together to form sensing phase B.

[0015] The measurement method of the above-mentioned reflective absolute angular displacement sensor includes the following steps:

[0016] 1) An excitation signal is applied to the excitation electrode. Under the action of the excitation electrode, the induction electrode outputs a corresponding traveling wave signal. The signal processing circuit processes the induction traveling wave signal and the reference signal of the same frequency accordingly to obtain a square wave signal. Then, relevant calculations are performed to obtain the angular displacement value θ. i And used as a precise measurement value;

[0017] 2) The control module emits a light beam that illuminates two reflective patterns. Two sets of photoelectric sensors collect the corresponding reflected light and output photoelectric signals to the signal processing circuit. After processing, the signal processing circuit obtains the angular displacement values ​​measured by the two sets of photoelectric sensors. Let the number of periods of the two reflective patterns be m and n, m and n be coprime and n > m, and the total angle of the sensors be 2π. The angular displacement value θ measured by the set of photoelectric sensors corresponding to the number of periods m is... m The angular displacement value θ corresponding to the group of photoelectric sensors that periodically varies within the range of [0-2π / m] with period number n is... n The angle difference between the two sets of photoelectric sensors varies periodically within the range [0-2π / n], and is represented by δ, where δ = θ. m - θ n By determining the number of reflective pattern cycles (N1) corresponding to the photoelectric sensor with a reflective pattern cycle number of n using the δ value, the absolute angle value θ can be roughly measured. c =(N1-1)2π / n+θ n ;

[0018] 3) The rough measurement of the absolute angle value θ c Divide by the precision measurement period width θ and round to obtain the precision measurement period N of the rotor base; Nθ is the coarse measurement value;

[0019] 4) The precise measurement value θ obtained in step 1)i Combining the coarse measurement value Nθ obtained in step 3) yields the final absolute angular displacement value θ. a = Nθ + θ i .

[0020] This invention generates four excitation signals with equal amplitude and 90° phase difference through an excitation module, which serve as inputs to an electric field-type grating angle sensor. The output signals from the electric field-type grating angle sensor and the photoelectric sensor are connected to a signal processing circuit. This circuit processes the traveling wave signal and reference signal generated by the grating angle sensor, and enhances the analog voltage signal converted from the amplitude sampling of the photoelectric sensor to improve the signal-to-noise ratio and ensure a clear signal. Finally, the processed signal is input to an FPGA module. The FPGA module receives the input signal from the signal processing circuit, demodulates the analog voltage signal processed by the photoelectric sensor to obtain coarse measurement data, and performs phase measurement on the signal generated by the grating angle sensor to obtain fine measurement data. Combining fine and coarse measurements enables absolute measurement.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The coarse measurement signal of this invention is based on the amplitude sampling of the light field intensity by the photocell in the photoelectric sensor. The light field intensity collected by the photocell is proportional to the area integral of the reflected pattern and the photoelectric sensor. The output displacement signal is proportional to the area integral of the reflected pattern. The encoded pattern is simple, the output displacement is linear, and the absolute position can be obtained through simple calculation. The encoding and decoding are simple.

[0023] 2. The present invention uses optical field amplitude sampling to achieve absolute angular periodic positioning for coarse measurement. Coarse periodic positioning only requires locating the period value of the incremental angular displacement sensor, and periodic positioning can be achieved without fine graphic printing. The positioning method is simple, and reflective graphic printing is simple and easy to implement.

[0024] 3. This invention achieves absolute positioning without employing a double-ring structure, fully utilizing the sensor's thickness space. The coarse-measurement reflective pattern and the fine-measurement excitation electrode are arranged in a two-layer structure, with the reflective pattern thickness only at the micrometer level (only 20µm in this example), thus its impact on the sensor thickness is negligible. Compared to existing two-ring structures in the width direction, this invention effectively reduces the sensor's volume, facilitating compact and miniaturized design.

[0025] 4. The present invention employs two different positioning and signal transmission methods for coarse and fine measurement. Since coarse measurement only needs to determine the period in which fine measurement is performed, it can tolerate a large absolute positioning error and can achieve large-size measurement. At the same time, there is no signal interference between the two methods, which can ensure high measurement accuracy while achieving large-size absolute positioning. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the sensor stator structure of the present invention.

[0027] Figure 2 This is a schematic diagram of the sensor rotor structure of the present invention.

[0028] Figure 3 This is a schematic diagram of the sensor installation according to the present invention.

[0029] Figure 4 This is a schematic diagram of the rotor of the present invention (without a light-absorbing insulating layer).

[0030] Figure 5 This is a schematic diagram of the encoding of the present invention.

[0031] Figure 6 This is a schematic diagram of the absolute positioning of photoelectric amplitude sampling according to the present invention.

[0032] Figure 7 This is a flowchart of the signal generation and data processing of the present invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] See Figures 1-5This invention discloses a reflective absolute angular displacement sensor, comprising a rotor base 2 and a stator base 1 arranged parallel to each other with a gap (d). A ring of excitation electrodes 1-1 is uniformly arranged along the circumference of the upper surface of the stator base 1, and a ring of sensing electrodes 2-1 is uniformly arranged along the circumference of the lower surface of the rotor base 2. The sensing electrodes on the rotor base are directly opposite the excitation electrodes on the stator base. A concentric annular light-absorbing insulating layer 2-3, covering all the sensing electrodes 2-1, is placed on the lower surface of the rotor base 2. Two rings of reflective patterns 2-4 are uniformly arranged along the circumference of the light-absorbing insulating layer 2-3. Each ring of reflective patterns 2-4 consists of several identical reflective patterns joined end-to-end. The two rings of reflective patterns are different and coprime in number. The area change of each reflective pattern along the circumference is a function of the corresponding angle change. A light-emitting module and two sets of photoelectric sensors 1-3 are provided on the upper surface of the stator base 1. The two sets of photoelectric sensors 1-3 are respectively directly opposite the two rings of reflective patterns. Each set of photoelectric sensors 1-3 consists of two sensors. The light-emitting module is used to send a light beam (which can be invisible or visible light) to the two rings of reflective patterns. The photoelectric sensors are used to collect the light intensity reflected by the reflective patterns and output the obtained photoelectric signal to the signal processing circuit. Since the area change of each reflective pattern along the circumference is a function of the corresponding angle change, correspondingly, during the rotation of the rotor base along the stator base, the area (overlapping area) of the photoelectric sensor and the reflective pattern changing is a function of the angular displacement.

[0035] In this invention, the positional relationship between the rotor base 2 and the stator base 1 is relative. Alternatively, the rotor base 2 can be below and the stator base 1 can be above, which is equivalent to flipping the entire sensor by 180° without changing its structure.

[0036] The inventive concept of this invention lies in using displacement data generated by an incremental angular displacement sensor for precise measurement, measuring precise angles within a small period, and using optical amplitude decoding values ​​generated by an absolute photoelectric sensor for coarse measurement. The number of absolute displacement cycles for the precise measurement is calculated from two rings of coprime reflective patterns through simple encoding and decoding. Combining these two methods achieves absolute precision measurement using the angular displacement sensor. The rotor base, stator base, and their excitation and sensing electrodes constitute the main body of the incremental angular displacement sensor, while the reflective patterns, light-emitting module, and photoelectric sensor constitute the main body of the absolute photoelectric sensor. The measurements of these two parts are independent of each other, but are combined in the algorithm; that is, the coarse measurement result is used to determine the precise measurement period, and thus the precise absolute displacement value.

[0037] See Figure 1The excitation electrode 1-1 is composed of 4k rectangular excitation electrodes of the same size and with a spacing of θ1, uniformly arranged along the circumference. Each group consists of four adjacent excitation electrodes, and the 4k excitation electrodes form k groups; k represents the stator cycle number. The excitation electrodes in the first position of each group are connected together to form excitation phase A, the excitation electrodes in the second position of each group are connected together to form excitation phase B, the excitation electrodes in the third position of each group are connected together to form excitation phase C, and the excitation electrodes in the fourth position of each group are connected together to form excitation phase D. See also... Figure 4 The induction electrode 2-1 consists of 2k identical double sinusoidal electrode plates evenly arranged along the circumference. Each pair of adjacent induction electrodes forms a group, and the 2k induction electrodes form k groups, where k represents the rotor cycle number (i.e., the stator cycle number is the same as the rotor cycle number). The induction electrodes in the first position of each group are connected together to form induction phase A, and the induction electrodes in the second position of each group are connected together to form induction phase B. The excitation module inputs four excitation signals to the four excitation phases of the stator base. These four excitation signals are represented as follows: , , , The mutual movement between the rotor and stator generates an induced traveling wave signal on the induction electrodes on the rotor base. The signal processing circuit amplifies and filters the induced traveling wave signal and the reference signal of the same frequency. After the traveling wave signal and the reference signal are shaped into a square wave by the zero-crossing comparator, the data is output to the FPGA module for high-frequency clock interpolation calculation to obtain the precise measurement value.

[0038] In this invention, each group of photoelectric sensors 1-3 consists of two sensors located on the same circumference. For the case where the reflective pattern is sinusoidal, the angle formed by the lines connecting the two photoelectric sensors in each group to the center of the stator substrate is equal to 1 / 4 of the circumferential angle of the single reflective pattern corresponding to that group of photoelectric sensors. For the case where the reflective pattern is triangular, if the angle corresponding to one period of the triangle is θ... x The angle occupied by the photoelectric sensor is θ y Then the distance between the two photoelectric sensors is θ. x -θ y .

[0039] The functional relationship is a sine or cosine function. The reflective pattern is a sine pattern or a triangle shape.

[0040] Due to the motion properties of the rotor substrate, directly leading signal lines through the induction electrodes would increase design complexity. Therefore, this invention solves this problem by using wireless transmission via signal emission. Specifically, two induction signal transmitting rings 2-2 are arranged on the lower surface of the rotor substrate 2, surrounding the induction electrodes 2-1. Each ring is connected to one of the two induction phases to transmit the induction signals generated by the corresponding phases. The light-absorbing insulating layer 2-3 covers all the induction electrodes 2-1 and the two induction signal transmitting rings 2-2. Two induction signal receiving rings 1-2 are arranged on the upper surface of the stator substrate 1, surrounding the excitation electrodes 1-1. Each receiving ring corresponds to one of the induction signal transmitting rings 2-2, receiving the induction signals transmitted by the corresponding ring. The traveling wave signals received by the two receiving rings are 180° out of phase, forming a differential signal. In specific connection, the odd-numbered induction electrode plates are connected to the inner ring induction signal transmitting ring, and the even-numbered induction electrode plates are connected to the outer ring induction signal transmitting ring. The induction signal receiving ring couples and receives the differential traveling wave signal emitted by the induction signal transmitting ring, and then sends it to the signal processing circuit.

[0041] In this embodiment, the two sets of photoelectric sensors 1-4 are located on the two loops of sensing signal receiving rings 1-2, respectively.

[0042] The photoelectric sensing part of this invention is further described below, and can also be found in [reference 1]. Figure 2 and Figure 5The light-absorbing insulating layer covering the rotor substrate sensing electrode is a black film, and the reflective pattern is white. The area of ​​the reflective pattern has a certain functional relationship with the angular displacement (it can be sinusoidal or triangular). Taking a sinusoidal signal as an example, the FPGA module on the stator substrate controls the light-emitting module to emit invisible light of constant intensity. The invisible light is reflected back to the photoelectric sensor by the rotor reflection pattern. The intensity of the light received by the photoelectric sensor is linearly related to the area between the photoelectric sensor and the reflective pattern. Since each group of photoelectric sensors in this invention consists of two sensors, the angle formed by the lines connecting the two photoelectric sensors to the center of the stator substrate is equal to 1 / 4 of the circumference angle of the single reflective pattern corresponding to that group of photoelectric sensors. Through area integration, it can be seen that the light signal collected by one photoelectric sensor has a sine relationship with the angle, and the light signal collected by the other photoelectric sensor has a cosine relationship with the angle. The circuit processing module converts the light intensity signals collected by the two photoelectric sensors into current signals. The current signals are converted into voltage signals, amplified, filtered, and sampled by the ADC amplitude before the collected voltage signals are sent to the FPGA for demodulation processing. The FPGA module calculates the tangent of the sinusoidal and cosine signals output from the two photoelectric sensors. It then divides each cycle into eight intervals by judging the sign of the sine and cosine signals. The intervals are determined by the sign of the absolute values ​​of the two sensor signals and the sign of the difference between their absolute values, thus converting the tangent signal into a quasi-linear periodic angle signal.

[0043] Since the voltage signal collected by the photoelectric sensor is a sine wave and a cosine wave, there are symmetrical rising and falling segments. This makes it impossible to determine whether the same voltage signal value is in the rising or falling segment. To address this issue, the present invention sets up two photoelectric sensors and performs the above-mentioned processing.

[0044] To achieve coarse-scale absolute positioning, the reflective pattern in this invention consists of two concentric rings. Specifically, a ring of reflective patterns is arranged outside the inner ring, with a period number that is prime to the inner ring (each reflective pattern represents one period). Similarly, a set of two photoelectric sensors is provided on the upper surface of the stator substrate, directly opposite the outer ring reflective pattern. The arrangement of the two photoelectric sensors is the same as above, and a periodically linearly varying displacement signal with the same period number as the outer ring can be obtained.

[0045] See Figure 6 Let m and n be the number of periods of the two reflective patterns, respectively. m and n are coprime and n > m. The total angle of the sensor is 2π. The angular displacement value θ measured by the photoelectric sensor corresponding to the reflective pattern with period m is... m The angular displacement value θ corresponding to the photoelectric sensor that collects a reflective pattern that varies periodically within the range of [0-2π / m] with a period number of n. n The angle difference θ between the two photoelectric sensors varies periodically within the range of [0-2π / n], and is represented by δ.m -θ n .pass Figure 6 It can be seen that no repeated δ value appears within the entire travel range of 2π, meaning that each angle difference δ uniquely corresponds to a cycle number. Therefore, this unique δ value can be used as the absolute positioning sequence value, and the number of sensor cycles N1 can be determined by looking up a table, thus roughly measuring the absolute angle value θ. c =(N1-1)2π / n+θ n The absolute angle value θ here. a It is a rough measurement of the absolute angle value. Although the accuracy is poor, it can be used to locate the rotor in the cycle of the fine measurement, thereby obtaining a high-precision displacement.

[0046] The angle value measured by the two sets of photoelectric sensors is a linear angle value with a relatively large error. The linear angle value measured by the photoelectric sensors can uniquely determine the period value N of the incremental angle displacement sensor. The angle value measured by the incremental sensor is a linear periodically changing angle value with high accuracy. The combination of the two sensors can measure a high-accuracy absolute angle value.

[0047] The complete signal generation and processing flow of this invention is as follows: Figure 7 As shown, the excitation control module in the FPGA generates four excitation voltage signals U with a 90° phase difference. S+ U C+ U S- U C- (corresponding to the aforementioned U) a U b U c U d The excitation electrode on the stator base of the incremental angular displacement sensor is activated. Under the action of the excitation electrode, the induction electrode on the rotor base senses and outputs a corresponding traveling wave signal. This signal is then output to the signal processing circuit through the transmitting and receiving loops. The signal processing circuit performs corresponding processing on the induced traveling wave signal and the reference signal of the same frequency, such as amplification, filtering, differential processing, and shaping, to obtain a square wave signal. This square wave signal is then input into the FPGA module for calculation, thus obtaining the angle value θ. i This is used as the precision measurement value. Simultaneously, the light-emitting control module in the FPGA module controls the light-emitting module in the signal processing circuit to emit a light beam, which illuminates two rings of reflective patterns on the rotor base. Two sets of photoelectric sensors on the stator base collect the corresponding reflected light and output photoelectric signals to the signal processing circuit. The signal processing circuit performs corresponding processing, such as amplification, filtering, and analog-to-digital conversion, to obtain the amplitude displacement signal. Then, the two sets of amplitude displacement signals are input to the FPGA module. After demodulation of the two sets of amplitude displacement values, the angular displacement value Nθ is obtained and used as the coarse measurement value. N represents the current precision measurement cycle number of the rotor base, and θ is the precision measurement cycle width, which here is 4θ1. The cycle N is obtained by measuring the coarse absolute displacement value θ.c Divide by the precision measurement period width θ and round to obtain the value. Finally, combine the precision measurement value with the coarse measurement value to achieve the absolute angle measurement, and obtain the final absolute angular displacement value θ. a = Nθ + θ i .

[0048] This invention's sensor comprises two parts: an incremental angular displacement sensor and an absolute photoelectric sensor. The incremental angular displacement sensor, serving as the precision measurement component, generates four excitation signals with equal amplitude and orthogonal phase through an excitation module, which are applied to excitation electrodes on the stator substrate. The induction electrodes on the rotor substrate generate two differential traveling wave signals. These signals are amplified, filtered, and differentially processed by a signal processing circuit. Finally, the incremental precision displacement value is obtained using high-frequency pulse interpolation technology in the FPGA module. The absolute photoelectric sensor performs absolute position periodic measurement, serving as the coarse measurement component. Two rings of reflective patterns with mutually prime period numbers are covered on the rotor substrate; the area of ​​the reflective patterns is a function of the displacement. A light-emitting module located on the stator substrate emits a light beam towards the rotor substrate. The reflective pattern covering the rotor substrate converts the area of ​​the pattern into light intensity, which is then reflected onto a photoelectric sensor. The photoelectric sensor converts the acquired optical signal into an analog signal. A signal processing circuit processes this analog signal, and the amplitude of the processed analog signal changes with the angle. Finally, the FPGA module calculates the absolute displacement cycle number by analyzing the two sets of analog signals with varying amplitudes as an angle. The incremental angle value obtained from the incremental angular displacement sensor and the absolute displacement cycle number obtained from the absolute photoelectric sensor are combined to obtain the absolute displacement value, thus achieving absolute measurement by the angular displacement sensor.

[0049] Compared with existing technologies, this invention employs a two-layer design structure to achieve precise measurement and absolute positioning, resulting in a more compact design and easier miniaturization. The upper layer uses two rings of photoelectric sensors and a reflective pattern to obtain the absolute position cycle count for coarse measurement. The printing of the reflective pattern does not require high precision to achieve absolute cycle measurement. Displacement calculation is performed by using the facing area of ​​the reflective pattern and photoelectric sensors, linearizing the pattern encoding and simplifying encoding and decoding. The lower layer uses an incremental grating angular displacement sensor to measure the precise angle value within the cycle, achieving fine measurement while maintaining high accuracy despite miniaturization. The combination of fine and coarse measurement achieves absolute measurement without mutual interference, ensuring that obtaining the absolute position cycle count does not affect the precision measurement signal.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A reflective absolute angular displacement sensor, comprising a rotor base and a stator base arranged in parallel with a gap, wherein an excitation electrode is uniformly arranged around the circumference of the surface of the stator base facing the rotor base, and a sensing electrode is uniformly arranged around the circumference of the surface of the rotor base facing the stator base, wherein the sensing electrode on the rotor base is directly opposite the excitation electrode on the stator base; characterized in that: A ring-shaped light-absorbing insulating layer, concentric with the rotor substrate, covers the surface of the rotor substrate facing the stator substrate, simultaneously covering all the sensing electrodes. Two concentric rings of reflective patterns are arranged evenly along the circumference on the light-absorbing insulating layer. Each ring of reflective patterns consists of several identical reflective patterns connected end to end. The two rings of reflective patterns are different and their numbers are coprime. The area change of each reflective pattern along the circumference is a function of the corresponding angle change. A light-emitting module and two sets of photoelectric sensors are provided on the surface of the stator substrate facing the rotor substrate. The two sets of photoelectric sensors are respectively facing the two rings of reflective patterns. The light-emitting module is used to send a light beam to the two rings of reflective patterns, and the photoelectric sensor is used to collect the light intensity reflected by the reflective patterns and output the obtained photoelectric signal to the signal processing circuit.

2. The reflective absolute angular displacement sensor according to claim 1, characterized in that: Each group of photoelectric sensors consists of two sensors located on the same circumference. The angle formed by the line connecting the two photoelectric sensors in each group to the center of the stator base is equal to 1 / 4 of the circumferential angle of the single reflective pattern corresponding to that photoelectric sensor.

3. The reflective absolute angular displacement sensor according to claim 1, characterized in that: The functional relationship is a sine or cosine function relationship.

4. A reflective absolute angular displacement sensor according to claim 1, characterized in that: Two rings of induction signal transmitting rings are arranged on the outer ring of the induction electrodes on the surface of the rotor base facing the stator base. The two rings of induction signal transmitting rings are respectively connected to the two induction phases to transmit the induction signals generated by the corresponding induction phases. The light-absorbing insulating layer covers all induction electrodes and the two rings of induction signal transmitting rings. Two rings of induction signal receiving rings are arranged on the outer ring of the excitation electrodes on the surface of the stator base facing the rotor base. The two rings of induction signal receiving rings correspond one-to-one with the two rings of induction signal transmitting rings and are used to receive the induction signals transmitted by the corresponding induction signal transmitting rings.

5. A reflective absolute angular displacement sensor according to claim 4, characterized in that: Two sets of photoelectric sensors are located on two loops of induction signal receiving rings, respectively.

6. A reflective absolute angular displacement sensor according to claim 1, characterized in that: The excitation electrode consists of 4k rectangular excitation electrodes of the same size with an electrode spacing of θ1, evenly arranged along the circumference. Each group consists of four adjacent excitation electrodes, and the 4k excitation electrodes form k groups. In each group, the excitation electrodes in the first position are connected together to form excitation phase A, the excitation electrodes in the second position are connected together to form excitation phase B, the excitation electrodes in the third position are connected together to form excitation phase C, and the excitation electrodes in the fourth position are connected together to form excitation phase D. The induction electrode consists of 2k double sinusoidal electrodes of the same size with an electrode spacing of 2θ1, evenly arranged along the circumference. Each group consists of two adjacent induction electrodes, and the 2k induction electrodes form k groups. In each group, the induction electrodes in the first position are connected together to form induction phase A, and the induction electrodes in the second position are connected together to form induction phase B.

7. The measurement method of a reflective absolute angular displacement sensor according to claim 1, characterized in that: The steps are as follows: 1) An excitation signal is applied to the excitation electrode. Under the action of the excitation electrode, the induction electrode outputs a corresponding traveling wave signal. The signal processing circuit processes the induction traveling wave signal and the reference signal of the same frequency accordingly to obtain a square wave signal. Then, the angular displacement value θ is calculated. i And used as a precise measurement value; 2) The control module emits a light beam that illuminates two reflective patterns. Two sets of photoelectric sensors collect the corresponding reflected light and output photoelectric signals to the signal processing circuit. After processing, the signal processing circuit obtains the angular displacement values ​​measured by the two sets of photoelectric sensors. Let the number of periods of the two reflective patterns be m and n, m and n be coprime and n > m, and the total angle of the sensors be 2π. The angular displacement value θ measured by the set of photoelectric sensors corresponding to the number of periods m is... m The angular displacement value θ corresponding to the group of photoelectric sensors that periodically varies within the range of [0-2π / m] with period number n is... n The angle difference between the two sets of photoelectric sensors varies periodically within the range [0-2π / n], and is represented by δ, where δ = θ. m - θ n By determining the number of reflective pattern cycles (N1) corresponding to the photoelectric sensor with a reflective pattern cycle number of n using the δ value, the absolute angle value θ can be roughly measured. c =(N1-1)2π / n+θ n ; 3) The rough measurement of the absolute angle value θ c Divide by the precision measurement period width θ and round to obtain the precision measurement period N of the rotor base; Nθ is the coarse measurement value; 4) The precise measurement value θ obtained in step 1) i Combining the coarse measurement value Nθ obtained in step 3) yields the final absolute angular displacement value θ. a = Nθ + θ i .

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