A high-precision displacement sensor system

Abstract

The utility model discloses a high accuracy displacement sensor system for absolute position detection, include: light source for sending light field path, grating ruler is set up in the light field path of light source, including grating ruler baseplate and the incremental code channel, index code channel, reference code channel of setting on grating ruler baseplate, photoelectric detector is set up in the light field path after grating ruler modulation, is used for receiving optical signal, including signal processing module, incremental signal detection module, index signal detection module, reference signal detection module, and the output incremental signal, index signal, reference signal, signal processor with photoelectric detector electric connection, is configured as the collection and processing incremental signal, index signal, reference signal, to fuse output absolute position information. The utility model discloses adopts multi code channel grating encoding and decoding technology to realize absolute position identification, and there is no cumulative error, realizes micro - nanometer level precision and the dual promotion of extreme environment reliability.

Description

Technical Field

[0001] This utility model relates to the field of precision measurement technology, and in particular to a high-precision displacement sensor system, which can be widely used in industrial automation, automobile manufacturing, production measurement, medical devices, aerospace and other fields. Background Technology

[0002] As a key component for acquiring position information, displacement sensors directly determine the performance level of high-end equipment and precision instruments through their accuracy and reliability. They are widely used in high-end technology fields such as CNC machine tools, industrial robots, semiconductor manufacturing equipment, medical devices, and aerospace. As these fields develop towards higher precision and higher automation, unprecedented high requirements are placed on the measurement accuracy (micrometer to nanometer level), environmental adaptability (such as vibration resistance, high temperature resistance, and corrosion resistance) and long-term reliability of displacement sensors.

[0003] Traditional high-precision position sensors, such as potentiometer, inductive, and capacitive sensors, have applications in specific scenarios, but each has its inherent limitations. Potentiometer sensors, based on the principle of resistance change, have a simple structure and low cost, but their core components are subject to mechanical contact and wear, resulting in a lifespan of usually less than one million cycles. They are only suitable for low- to mid-range scenarios where lifespan and accuracy requirements are not high, such as automotive pedals and valve control. Inductive and capacitive sensors achieve measurement through changes in coil inductance or plate capacitance, respectively, with resolutions reaching micrometers or even nanometers. However, inductive sensors typically have a small measurement range, while capacitive sensors are highly susceptible to changes in ambient temperature and humidity, as well as electric field interference, resulting in insufficient stability and limiting their application in complex industrial environments.

[0004] To overcome the shortcomings of the aforementioned sensors, digital grating ruler sensors have become the mainstream technology for high-precision position measurement. Incremental grating rulers, in particular, count relative displacement by reading the phase signal generated by periodic grating lines, achieving extremely high resolution. However, they have two fundamental drawbacks: First, the system cannot know its current position each time it is powered on and must perform a "zeroing" operation to find a reference point, which seriously affects the efficiency and automation of the equipment. Second, during long-term operation, it is highly susceptible to signal loss or counting errors caused by electrical noise and vibration, resulting in cumulative errors that cannot be self-corrected, affecting long-term accuracy and reliability.

[0005] To address the shortcomings of incremental gratings, absolute grating rulers have emerged. By engraving a unique absolute position code on the ruler, the absolute position value can be directly read upon system power-up, avoiding zeroing operations and eliminating accumulated errors. However, existing single-track absolute encoding technology often requires reducing the encoding density to cover a large range, resulting in an inherent resolution far lower than that of incremental gratings. This makes it difficult to simultaneously meet the requirements of a large range and ultra-high resolution. If multi-track parallel encoding is used to improve resolution, it will lead to a complex grating ruler structure, large size, and a sharp increase in manufacturing costs, and the corresponding photoelectric reading system will also become more complex.

[0006] In summary, those skilled in the art face a long-standing technical dilemma: how to simultaneously achieve high resolution for incremental measurements, power-on functionality for absolute measurements, and zero cumulative error characteristics within a single displacement sensor system, while maintaining a compact system structure and controllable cost. Existing technical solutions all involve trade-offs between accuracy, functionality, cost, and reliability, failing to fundamentally meet the comprehensive requirements of high-end industrial applications for displacement sensors. Utility Model Content

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a high-precision displacement sensor system that uses multi-channel grating encoding and decoding technology to achieve absolute position recognition without cumulative error, thus achieving a dual improvement in micro-nano-level accuracy and reliability in extreme environments.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a high-precision displacement sensor system for absolute position detection, comprising:

[0009] A light source, used to emit a light field path;

[0010] A grating ruler is disposed in the light field path of the light source, and includes a grating ruler substrate and incremental code track, index code track and reference code track disposed on the grating ruler substrate;

[0011] A photodetector, disposed in the optical field path modulated by the grating ruler, is used to receive optical signals. It includes a signal processing module, an incremental signal detection module, an index signal detection module, and a reference signal detection module. The incremental signal detection module collects the optical signal of the incremental code channel, converts it into an optical signal, and then adjusts and outputs an incremental signal by the signal processing module. The index signal detection module collects the optical signal of the index code channel, converts it into an optical signal, and then adjusts and outputs an index signal by the signal processing module. The reference signal detection module collects the optical signal of the reference code channel, converts it into an optical signal, and then adjusts and outputs a reference signal by the signal processing module.

[0012] The signal processor, electrically connected to the photodetector, is configured to acquire and process incremental signals, index signals, and reference signals to fuse and output absolute position information.

[0013] As a preferred embodiment, the light source is a Lambertian light-emitting chip mounted on the photodetector, or the light source is a collimated light source separately from the photodetector.

[0014] As a preferred embodiment, the grating ruler is a reflective grating, the grating ruler substrate is made of metal, and the incremental code track, index code track, and reference code track are light-absorbing material layers deposited in grooves etched on the surface of the metal grating ruler substrate.

[0015] As a preferred embodiment, the grating ruler is a transmissive grating, the grating ruler substrate is a transparent material such as glass or plastic, and the incremental code track, index code track, and reference code track are patterns formed by a light-shielding coating on the surface of the transparent grating ruler substrate.

[0016] As a preferred embodiment, the incremental code track is a periodic grating structure used to generate a phase difference signal, the index code track is a grating structure with a unique reference mark engraved at a fixed position used to output an index signal to calibrate the start of the period, and the reference code track is a grating structure with a unique non-repeating code engraved across the entire range used to determine the absolute position.

[0017] As a preferred embodiment, the incremental code track is an equally spaced grating pattern with a period length of T, and the index code track is an equally spaced grating pattern with a period length of 2T, used to generate an absolute index point signal every increment period. The reference code track is a non-periodic pattern that covers the entire measurement path and whose line width or spacing changes continuously.

[0018] As a preferred embodiment, the incremental signal detection module and the index signal detection module in the photodetector are photodiode arrays, and the reference signal detection module is a single or multiple light-emitting diodes.

[0019] As a preferred embodiment, the signal processing module includes an operational amplifier and a comparator. The operational amplifier is used to convert the detection signals from the incremental signal detection module and the reference signal detection module into sine and cosine voltage incremental signals and analog level reference signals, respectively. The comparator is used to convert the detection signals from the index signal detection module into TTL level index signals.

[0020] As a preferred embodiment, the signal processor includes a microprocessor, an analog-to-digital converter, and a communication interface. The analog-to-digital converter is used to convert the analog signals of the incremental signal, index signal, and reference signal into digital signals. The microprocessor is used to fuse the digital signals of the incremental signal, index signal, and reference signal to obtain absolute position information. The communication interface is used to output the absolute position information.

[0021] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0022] (1) Combination of high precision and large range: high-resolution measurement at the nanometer level is achieved through incremental code channels, and absolute position identification with a large range is achieved through reference code channels, thus balancing precision and range.

[0023] (2) Power-on and ready to use, no need to return to zero: By using the absolute position information provided by the reference code track, the system can immediately determine the current position after power-on or restart, avoiding the traditional full-stroke zeroing operation and improving efficiency;

[0024] (3) No cumulative error: The cumulative error of incremental counting can be reset periodically by using the periodic reference points provided by the index code track, which ensures the stability and reliability of long-term measurement.

[0025] (4) Flexible structure and wide applicability: It can adopt a reflective or transmissive optical path structure, and the grating can be straight or circular, which is suitable for various industrial application scenarios such as machining and manufacturing, electronic and semiconductor manufacturing, automated equipment calibration, material error prevention and control. Attached Figure Description

[0026] Figure 1 This is a system block diagram of this utility model;

[0027] Figure 2 This is a schematic diagram of the structure of the grid ruler in this utility model;

[0028] Figure 3 This is a schematic diagram of the structure of the photodetector and signal processor in this utility model;

[0029] Figure 4 This is a schematic diagram of the reflective high-precision displacement sensor system in this utility model;

[0030] Figure 5 This is a schematic diagram of the transmission-type high-precision displacement sensor system in this utility model;

[0031] The attached diagram includes the following components: light source 1, grating ruler 2, grating ruler substrate 200, incremental code track 201, index code track 202, reference code track 203, photodetector 3, signal processing module 300, incremental signal detection module 301, index signal detection module 302, reference signal detection module 303, operational amplifier 304, comparator 305, signal processor 4, microprocessor 41, analog-to-digital converter 42, and communication interface 43. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the protection scope of the present invention.

[0033] Example 1:

[0034] like Figures 1-3 As shown, a high-precision displacement sensor system for absolute position detection includes:

[0035] Light source 1, used to emit the light field path;

[0036] The grating ruler 2 is disposed in the light field path of the light source 1, and includes a grating ruler substrate 200 and an incremental code track 201, an index code track 202, and a reference code track 203 disposed on the grating ruler substrate 200.

[0037] A photodetector 3, disposed in the optical field path modulated by the grating ruler 2, is used to receive optical signals. It includes a signal processing module 300, an incremental signal detection module 301, an index signal detection module 302, and a reference signal detection module 303. The incremental signal detection module 301 collects the optical signal of the incremental code channel 201, converts it into an optical signal, and then the signal processing module 300 adjusts and outputs an incremental signal. The index signal detection module 302 collects the optical signal of the index code channel 202, converts it into an optical signal, and then the signal processing module 300 adjusts and outputs an index signal. The reference signal detection module 303 collects the optical signal of the reference code channel 203, converts it into an optical signal, and then the signal processing module 303 adjusts and outputs a reference signal.

[0038] The signal processor 4 is electrically connected to the photodetector 3 and is configured to acquire and process incremental signals, index signals, and reference signals to fuse and output absolute position information.

[0039] Preferably, the light source 1 is a Lambertian light-emitting chip mounted on the photodetector 3, or the light source 1 is a collimated light source separately from the photodetector 3.

[0040] Specifically, light source 1 can be a point light source, collimated light source, diffuse light source, integrated light source, etc. It can be an LED chip, VCSEL chip, solid-state light source, LD light source, or a surface light source or volume light source composed of a light source plus a lens, superlens, diffractive light source element, package, etc.

[0041] Preferably, the grating ruler 2 is a reflective grating, the grating ruler substrate 200 is made of metal, and the incremental code track 201, index code track 202, and reference code track 203 are light-absorbing material layers deposited in grooves etched on the surface of the metal grating ruler substrate 200.

[0042] Specifically, the grid substrate 200 includes, but is not limited to, opaque materials or processes such as steel alloy, aluminum alloy, and coated metal.

[0043] Preferably, the grating ruler 2 is a transmissive grating, the grating ruler substrate 200 is made of glass or transparent plastic material, and the incremental code track 201, index code track 202, and reference code track 203 are patterns formed by a light-shielding coating formed on the surface of the transparent grating ruler substrate 200.

[0044] Specifically, the grid substrate 200 includes, but is not limited to, light-transmitting or partially light-transmitting processes or materials such as glass and plastic.

[0045] Furthermore, the grating ruler 2 includes circular code disks of different radii, linear grating rulers, and other grating rulers with arbitrary motion trajectories and shapes. The grating ruler 2 can be various grating types such as rectangular gratings, sinusoidal gratings, blazed gratings, step gratings, and volume gratings, including but not limited to transmission gratings, reflection gratings, diffraction gratings, or interference gratings.

[0046] Furthermore, the incremental code channel 201, index code channel 202, and reference code channel 203 include, but are not limited to, processes, materials, or coatings for absorption, reflection, transmission, scattering, interference, or diffraction.

[0047] Preferably, the incremental code track 201 is a periodic grating structure used to generate a phase difference signal, the index code track 202 is a grating structure with a unique reference mark engraved at a fixed position used to output an index signal to calibrate the start of the period, and the reference code track 203 is a grating structure with a unique non-repeating code engraved across the entire range used to determine the absolute position.

[0048] Specifically, the grating substrate 200 includes at least three types of code tracks: incremental code track 201, index code track 202, and reference code track 203. Incremental code track 201 is a periodic grating structure used to generate square wave or simple harmonic signals with phase difference for real-time displacement calculation. Index code track 202 is a grating structure with a unique reference point or distance-encoded reference mark engraved at a fixed position. The code track outputs an index signal (zero-position pulse) to mark the periodic start point of the incremental signal, assisting in eliminating accumulated errors or achieving periodic position calibration. Reference code track 203, also known as absolute code track, is a grating structure with a unique non-repeating code engraved throughout the entire range. It is used to quickly determine the absolute position upon power-on, avoiding full-stroke zero-return operation.

[0049] More preferably, the incremental code track 201 is an equally spaced grating pattern with a period length of T, and the index code track 202 is an equally spaced grating pattern with a period length of 2T, used to generate an absolute index point signal every increment period, and the reference code track 203 is a non-periodic pattern that covers the entire measurement stroke and whose line width or spacing changes continuously.

[0050] Specifically, the aperiodic pattern of reference code track 203 includes, but is not limited to, triangles or trapezoids.

[0051] Preferably, the incremental signal detection module 301 and the index signal detection module 302 in the photodetector 3 are photodiode arrays, and the reference signal detection module 303 is a single or multiple light-emitting diodes.

[0052] Specifically, the incremental signal detection module 301, index signal detection module 302, and reference signal detection module 303 in the photodetector 3 include, but are not limited to, photoresistors, photoconductive detectors, photodiodes, APDs, PMTs, CCDs, CMOS, InGaAs detectors, etc.

[0053] More specifically, the incremental signal detection module 301 in the photodetector 3 is used to detect the optical field path modulated by the incremental code channel 201, and outputs an incremental signal carrying a small range of precise position information after photoelectric conversion; the index signal detection module 302 is used to detect the optical field path modulated by the index code channel 202, and outputs an index signal carrying an absolute position index point after photoelectric conversion; the reference signal detection module 303 is used to detect the optical field path modulated by the reference code channel 203, and outputs a reference signal after photoelectric conversion. This reference signal is unique across the entire range and is used to determine a coarse absolute position.

[0054] Preferably, the signal processing module 300 includes an operational amplifier 304 and a comparator 305. The operational amplifier 304 is used to convert the detection signals of the incremental signal detection module 301 and the reference signal detection module 303 into sine and cosine voltage incremental signals and analog level reference signals, respectively. The comparator 305 is used to convert the detection signal of the index signal detection module 302 into a TTL level index signal.

[0055] Specifically, the operational amplifier 304 is used to amplify the weak current signals output by the incremental signal detection module 301 and the reference signal detection module 303 across impedance and convert them into voltage signals, and then filter and amplify them to generate high-quality sine and cosine voltage incremental signals and analog level reference signals. The comparator 305 is used to compare the analog signal of the index signal detection module 302 with a threshold voltage to generate a clear TTL level index signal.

[0056] Preferably, the signal processor 4 includes a microprocessor 41, an analog-to-digital converter 42, and a communication interface 43. The analog-to-digital converter 42 is used to convert the analog signals of the incremental signal, the index signal, and the reference signal into digital signals. The microprocessor 41 is used to fuse the digital signals of the incremental signal, the index signal, and the reference signal to obtain absolute position information. The communication interface 43 is used to output the absolute position information.

[0057] Specifically, the microprocessor 41 obtains the absolute coarse position information n of the entire range from the reference signal subdivision counting, demodulates the absolute index point 0 from the index signal, and re-subdivides the counting with the absolute index point 0 as the zero point to eliminate the deviation caused by the cumulative error of the incremental code track 201. The microprocessor 41 demodulates the motion direction information from the incremental signal, adds the positive direction and subtracts the negative direction, and at the same time subdivides the incremental signal to obtain the precise position subdivision information δ, and fuses them to obtain the absolute position information P = n + 0 ± δ.

[0058] More specifically, the reference signal is unique across the entire range, used to determine absolute coarse position information, determine the initial position and avoid the traditional incremental zero-return operation, and when power is restored after a power outage, the absolute coarse position is directly determined based on the reference signal without the need to perform a zero-return operation, thereby ensuring that the position information is not lost after power failure.

[0059] In specific implementation, such as Figure 4 As shown, in this embodiment, the light source 1 is a Lambertian light-emitting chip integrated on the photodetector 3. The grating is a reflective grating, and the grating substrate 200 is stainless steel with chrome plating. The incremental code channel 201, index code channel 202, and reference code channel 203 are light-absorbing materials etched and deposited on the metal surface. The incremental code channel 201 is a periodic grating structure with a period length of T, the index code channel 202 is a periodic grating structure with a period length of 2T, and the reference code channel 203 is a triangular code channel covering the entire measurement range. The light emitted by the light source 1 is reflected by the incremental code channel 201 and detected by the PD array on the incremental signal detection module 301. The signal processing module 300 converts it into a sinusoidal voltage incremental signal output. The light emitted by the light source 1 is reflected by the index code channel 202 and detected by the PD array on the index signal detection module 302. The signal processing module 300 converts it into a TTL level index signal output. The light emitted by the light source 1 is reflected by the reference code channel 203. After reflection, the signal is detected by the PD on the reference signal detection module 303 and converted into an analog level reference signal output by the signal processing module 300. When the high-precision displacement sensor is used for measurement, the test structure drives the scale 2 to move relative to the photodetector 3. The signal processor 4 collects the incremental signal, index signal and reference signal output by the photodetector 3. The signal processor 4 demodulates the motion direction information from the incremental signal and simultaneously subdivides and counts the incremental signal within the period T to obtain precise displacement information. The signal processor 4 demodulates the index signal to generate an absolute index point signal once every 2T, eliminating the deviation caused by the cumulative error of the incremental code track 201. The signal processor 4 subdivides and counts the reference signal to obtain the absolute coarse position information of the entire range, determines the initial position and avoids the zero-return operation of the traditional incremental signal, and the position information is not lost when power is turned off and then restored. Thus, the information calculated by the signal processor 4 from the incremental signal, index signal and reference signal is fused to obtain the absolute position information.

[0060] Example 2:

[0061] The difference from Example 1 is that, as Figure 5 As shown, in this embodiment, the light source 1 is a collimated light source. The light source 1 and the photodetector 3 are located on opposite sides of the grating ruler 2. The grating is a transmission grating, and the grating ruler substrate 200 is a glass surface plated with chrome. The incremental code channel 201, the index code channel 202, and the reference code channel 203 are light-transmitting channels etched on a metal surface. The incremental code channel 201 is a periodic grating structure with a period length of T, the index code channel 202 is a periodic grating structure with a grating pitch of 2T, and the reference code channel 203 is a trapezoidal code channel covering the entire measurement range. The light emitted by the light source 1 is transmitted through the incremental code channel 201 and detected by the PD array on the incremental signal detection module 301. The signal processing module 300 converts it into a sinusoidal voltage incremental signal output. The light emitted by the light source 1 is transmitted through the index code channel 202 and detected by the PD array on the index signal detection module 302. The signal processing module 300 converts it into a TTL level index signal output. The light emitted by the light source 1 is transmitted through the reference code channel 203 and... The PD detection on the reference signal detection module 303 is converted into an analog level reference signal output by the signal processing module 300. When the high-precision displacement sensor is used for measurement, the test structure drives the scale 2 to move relative to the photodetector 3. The signal processor 4 collects the incremental signal, index signal and reference signal output by the photodetector 3. The signal processor 4 demodulates the motion direction information from the incremental signal and simultaneously subdivides and counts the incremental signal within the period T to obtain precise displacement information. The signal processor 4 demodulates the absolute index point signal generated once every 2T from the index signal to eliminate the deviation caused by the cumulative error of the incremental code track 201. The signal processing system subdivides and counts the reference signal to obtain the absolute coarse position information of the entire range, determines the initial position and avoids the zero-return operation of the traditional incremental signal, and the position information is not lost when power is turned off and then restored. Thus, the information calculated by the signal processor 4 from the incremental signal, index signal and reference signal is fused to obtain the absolute position information.

[0062] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A high-precision displacement sensor system for absolute position detection, characterized in that, include: A light source, used to emit a light field path; A grating ruler is disposed in the light field path of the light source, and includes a grating ruler substrate and incremental code track, index code track and reference code track disposed on the grating ruler substrate; A photodetector, disposed in the optical field path modulated by the grating ruler, is used to receive optical signals. It includes a signal processing module, an incremental signal detection module, an index signal detection module, and a reference signal detection module. The incremental signal detection module collects the optical signal of the incremental code channel, converts it into an optical signal, and then adjusts and outputs an incremental signal by the signal processing module. The index signal detection module collects the optical signal of the index code channel, converts it into an optical signal, and then adjusts and outputs an index signal by the signal processing module. The reference signal detection module collects the optical signal of the reference code channel, converts it into an optical signal, and then adjusts and outputs a reference signal by the signal processing module. The signal processor, electrically connected to the photodetector, is configured to acquire and process incremental signals, index signals, and reference signals to fuse and output absolute position information.

2. The high-precision displacement sensor system according to claim 1, characterized in that: The light source is a Lambertian light-emitting chip mounted on the photodetector, or the light source is a collimated light source separately from the photodetector.

3. The high-precision displacement sensor system according to claim 1, characterized in that: The grating ruler is a reflective grating, the grating ruler substrate is made of metal, and the incremental code track, index code track, and reference code track are light-absorbing material layers deposited in grooves etched on the surface of the metal grating ruler substrate.

4. The high-precision displacement sensor system according to claim 1, characterized in that: The grating ruler is a transmissive grating, the grating ruler substrate is a transparent material such as glass or plastic, and the incremental code track, index code track, and reference code track are patterns formed by a light-shielding coating on the surface of the transparent grating ruler substrate.

5. The high-precision displacement sensor system according to claim 1, characterized in that: The incremental code track is a periodic grating structure used to generate a phase difference signal. The index code track is a grating structure with a unique reference mark engraved at a fixed position, used to output an index signal to calibrate the start of the period. The reference code track is a grating structure with a unique non-repeating code engraved across the entire range, used to determine the absolute position.

6. The high-precision displacement sensor system according to claim 1, characterized in that: The incremental code track is an equally spaced grating pattern with a period length of T, and the index code track is an equally spaced grating pattern with a period length of 2T, used to generate an absolute index point signal every increment period. The reference code track is a non-periodic pattern that covers the entire measurement path and whose line width or spacing changes continuously.

7. A high-precision displacement sensor system according to claim 1, characterized in that: The incremental signal detection module and index signal detection module in the photodetector are photodiode arrays, and the reference signal detection module is a single or multiple light-emitting diodes.

8. A high-precision displacement sensor system according to claim 1, characterized in that: The signal processing module includes an operational amplifier and a comparator. The operational amplifier is used to convert the detection signals from the incremental signal detection module and the reference signal detection module into sine and cosine voltage incremental signals and analog level reference signals. The comparator is used to convert the detection signals from the index signal detection module into TTL level index signals.

9. A high-precision displacement sensor system according to claim 1, characterized in that: The signal processor includes a microprocessor, an analog-to-digital converter, and a communication interface. The analog-to-digital converter is used to convert analog signals of incremental signals, index signals, and reference signals into digital signals. The microprocessor is used to fuse the digital signals of incremental signals, index signals, and reference signals to obtain absolute position information. The communication interface is used to output the absolute position information.

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