Photoelectric Encoder Research Articles

Ultrasonic Obstacle Avoidance and Full-Speed-Range Hybrid Control for Intelligent Garages.

In the current study, which focuses on the operational safety problem in intelligent three-dimensional garages, an obstacle avoidance measurement and control scheme for the AGV parking robot is proposed. Under the premise of high-precision distance detection using Kalman filtering, a mathematical model of a brushless DC (BLDC) motor with full-speed range hybrid control is established. MATLAB/Simulink (R2022a) is used to build the control model, which has dual closed-loop vector-controlled motors in the low- to medium-speed range, with photoelectric encoders for speed feedback. The simulation results show that, at lower to medium speeds, the maximum overshoot of the output response curve is 1.5%, and the response time is 0.01 s. However, at higher speeds, there is significant jitter in the speed output waveform. Therefore, the speed feedback is switched to a sliding mode observer (SMO) instead of the original speed sensor at high speeds. Experiments show that, based on the SMO, the problem of speed waveform jitter at high motor speeds can be significantly improved, and the BLDC motor system has strong robustness. The above shows that the motor speed under the full-speed range hybrid control system can meet the AGV control and safety requirements.

Research on high-precision encoder based on optical-magnetic combination structure to measure absolute angle

As a kind of sensor for real-time feedback and dynamic monitoring of angular velocity and angular displacement of the system, the common photoelectric encoder is widely used in many fields such as new energy electric vehicles, servo closed-loop control systems, industrial control, security monitoring. In order to improve the resolution and accuracy, a kind of optical and magnetic combined encoder which combines photoelectricity and multi-pole magnetoelectricity is designed in this paper, where the light-blocking disk of photoelectric sensor is designed according to the pseudo-random sequence, and the photoelectric coding is used to determine the magnetic interval of multi-pole. The absolute angle is calculated according to the number of multiple circles plus the angle of single circle. The experimental results at different temperatures (−40 °C∼100 °C) show that the accuracy of the proposed combined encoder can reach ±0.08°, which is improved by 0.37° compared with that of the single-pole encoder. Finally, the combined encoder was applied to the pan-tilt-zoom (PTZ) camera of a video surveillance enterprise, and the experiment showed that its repeated positioning accuracy reached ±0.02°, which is greatly improved compared with single-pole encoder.

Absolute Photoelectric Encoder Based on Position-Sensitive Detector Sensor

In response to the engineering, miniaturization, and high measurement accuracy requirements of encoders, this paper proposes a new type of absolute photoelectric encoder based on a position-sensitive detector (PSD). It breaks the traditional encoder’s code track design and adopts a continuous and transparent code track design, which has the advantages of small volume, high angle measurement accuracy, and easy engineering. The research content of this article mainly includes the design of a new code disk, decoding circuit, linear light source, and calibration method. The experimental results show that the encoder designed in this article has achieved miniaturization, simple installation and adjustment, and easy engineering. The volume of the encoder is Φ50 mm × 30 mm; after calibration, the resolution is better than 18 bits, and the accuracy reaches 5.4″, which further demonstrates the feasibility of the encoder’s encoding and decoding scheme.

Research on the analog-to-digital hybrid square wave encoder signal error compensator

Photoelectric encoders are important electronic components, widely used in motion control systems, position measurement systems, and can measure angular displacement or displacement with high accuracy. Encoders widely used today output analog sine waves or digital square waves. The resolution of the encoder determines the measurement accuracy of the encoder, because the sine wave encoder can be more easily subdivided, which gradually replaces the square wave encoder in many occasions, but the square wave encoder is still widely used in the system with low demand for accuracy and low cost. The prerequisite for high subdivision of the output of the square wave encoder is good signal quality. Through the study of the signal output by the ideal encoder, this paper proposes the characteristics of distinguishing the error signal from the ideal signal, divides the error into two categories, designs a filter with two steps to compensate separately, and uses Simulink to establish a simulation model for verification.

Simulation analysis and collaborative optimization of key components of the precision detection platform for high precision encoder

To realize the error detection of the high-precision photoelectric encoder, the optical small-angle precision measurement principle of the photoelectric autocollimator and single-sided mirror, and the 360° full circle measurement principle of angle inversion of the compound biaxis turntable are used to establish the precision detection platform of the encoder. The error model of the biaxial structure in the photoelectric coding error detection platform is established by introducing the error sources of the biaxial structure, such as the coaxiality error, angular position error, and installation error. At the same time, the biaxis structure and error models are used to optimize the compound biaxis structure system. By analyzing the natural frequency and vibration characteristics of the structure, the rationality and reliability of the compound biaxis system of the high-precision encoder precision detection platform are verified.

Data Acquisition and Performance Analysis of Image-Based Photonic Encoder Using Field-Programmable Gate Array (FPGA)

With the continuous advancement of numerical control technology, the requirements for the position detection resolution, precision, and size of photoelectric encoders in computer numerical control machine tools are increasingly stringent. In the pursuit of high resolution and precision, this work investigates the principles of electronic subdivision and embedded hardware. It designs a high-precision image-based photonic encoder using a Field-Programmable Gate Array (FPGA). This photonic encoder captures the pattern of a rotating code disk using a complementary metal-oxide-semiconductor (CMOS) image sensor. The encoder’s core is the XC6SLX25T chip from the Spartan-6 series, with peripheral circuits including only A/D sampling and low-pass signal processing circuits. The FPGA module handles the digital signal reception, waveform conversion, quadrature frequency coarse count calculation, fine count subdivision calculation, and final position calculation of the encoder. In experiments, the output signal of the photonic encoder contains many impurities. After processing by the signal processing module, the A and B phase signals are not affected by previous interference, with a phase difference of 90°, meeting the requirements for subsequent signal processing modules. After fine count subdivision processing, the waveform graph significantly increases within one cycle, and after quadrupling the frequency, 30 subdivisions are performed within each cycle. Noise is introduced into graphic positioning or graphics are positioned under different noise conditions. Experimental results show that utilizing an improved centroid algorithm helps further suppress noise and enhance measurement accuracy in the design of image-based photonic encoders.

An Encoder-Based Relative Attitude Observation Method for Self-Calibration in Dual-Axis RINS

This study investigates an encoder-based relative attitude observation method for self-calibration in dual-axis rotational inertial navigation system (RINS). First, the calibration error of the gyroscope parameters caused by the velocity and position observations in systematic calibration is analyzed. Second, a relative attitude observation method utilizing photoelectric encoders for gyroscope parameters estimation is proposed. We apply the proposed method in our designed dual-axis RINS to verify its effectiveness in this work. Experimental results show that the calibration accuracy of the gyroscope can be improved to 0.0005 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^ \circ /h$</tex-math></inline-formula> in bias, and 0.98 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ppm$</tex-math></inline-formula> in scale factor using the proposed method. The proposed self-calibration method can be utilized as a high-accuracy self-calibration method in dual-axis RINS when the vehicle is in static condition.

Forced Servoing of a Series Elastic Actuator Based on Link-Side Acceleration Measurement

Joint stiffness of an elastic-joint robot can be changed according to joint stiffness requirements. A series elastic actuator (SEA) can reduce the contact stiffness between the body and the environment or human, which can further ensure interactive operation in a human–machine-compatible environment. However, the introduction of the SEA improves the complexity of the robot dynamics model. In this paper, we propose a control schema based on link-side acceleration measurement to eliminate the overshoot and vibration in the transient process of force control. An extended Kalman filter (EKF) algorithm that fuses photoelectric encoders and accelerometers is first presented based on the link-side acceleration measurement. Following this, based on the external torque estimation, the vibration reduction control algorithm is designed. The simulation model is built, and the algorithm design and simulation of position control and force control are carried out and finally tested on the real robot platform. The effectiveness of the control algorithm is proved. The experimental results show that the dynamic response of the external force estimation is about 2 ms faster than that of the force sensor, and the error between the estimated external torque and the real external torque is within ±0.16 N·m.

Development of wire length measuring equipment for prefabricated erection of transmission lines

AbstractThe existing prefabricated wireline construction technology is difficult to accurately measure the real‐time length of the deployed wires, resulting in too large construction errors and cannot be popularized and applied. To this end, a length measuring device that can accurately measure the length of the wire during the construction of the prefabricated wire is developed. In terms of the hardware of the length measuring equipment, based on the construction characteristics of the prefabricated wiring and the characteristics of the wire, the photoelectric encoder and the STC8G series single‐chip microcomputer are used to complete the collection and processing of the wire length data, and the mature and stable LoRa technology is used to complete the wireless transmission of the data. In terms of software program of length measurement equipment, the measurement of wire length data, transmission, and interaction of control command signals are realized by optimizing length measurement scheme, interface development of terminal equipment, and information interaction program design. Finally, according to the actual working conditions of the prefabricated wiring construction, the mechanical structure of the length measuring equipment is designed, and the assembly is completed. The developed length measuring equipment has been successfully applied to practical projects. According to the wire length measuring equipment, the deviation between the observation sag and the design sag after the wire length is measured by the wire length measuring equipment is 2.0%, which meets the design requirement of ±2.5%.

Track Image Acquisition Based on the Signal Device of the Photoelectric Encoder

The photoelectric encoder is a kind of encoder that uses high-precision metrology grating as the detection element to convert the input angular position information into corresponding digital signals through the photo-electric conversion device. It has the advantages of high resolution and wide measuring range, so it is widely used in precision angle measuring devices and high-precision speed regulating systems. In this study, an incremental photoelectric encoder is used, and a receiving system of vertical incidence is chosen, covering a photocell receiving circuit and an infrared circuit. The signal acquisition device of the photoelectric encoder is further designed, that is, the weak photoelectric signal is captured and transformed into an electrical signal that can be recognized by the microprocessor after amplification and adjustment, and then the signal is processed and transmitted. In the test, the signal output of the photoelectric encoder is simulated first. The results reveal that the theoretical output voltage of the drive is 3.5 V, and the peak of the actual output signal is 7.2 V, which meets the design requirements. The designed photoelectric encoder signal device is used with the charge coupled device (CCD) camera to capture the track image. The single-camera and dual-camera tests are carried out respectively. The speed of the bearing vehicle is adjusted to 0.6 m/s~1.2 m/s, and the velocity of the vehicle is adjusted timely. The findings show that the signal device of the photoelectric encoder +CCD camera can be triggered in real-time with the different speeds of the vehicle, and obtain relatively clear images of the track surface and its image of the fastener.

Speed feedback observation algorithm based on parameter introduction and its application in asynchronous motor

In this article, three-phase asynchronous motor and photoelectric encoder are taken as the research objects. In order to solve the problem of delay in the velocity feedback measurement result of asynchronous motor by photoelectric encoder, this article proposes a velocity feedback observation algorithm which introduces parameters according to different velocity instructions. The proposed method ensures that the speed feedback of asynchronous motor can keep good tracking effect under different speed instructions, reduces feedback delay, and the oscillation of speed tracking waveform is small. Stability analysis is also carried out in this article to ensure the reliability of the system. In the whole control system, the position signal output by the photoelectric encoder is the input of the algorithm, and the output of the algorithm is the speed feedback of the system. The proposed method establishes the speed control system model of three-phase asynchronous motor through MATLAB/Simulink for simulation, and the experiment is carried out based on the simulation. The simulation and experiment are compared with the traditional differential velocity measurement method of encoder. The results show that the velocity observation algorithm proposed is verified under different velocity instructions and varying loads, and the system has smaller steady-state error, better dynamic response, and good robustness.

Research on Tree Ring Micro-Destructive Detection Technology Based on Digital Micro-Drilling Resistance Method

Micro-drilling resistance method is a widely used tree ring micro-destructive detection technology. To solve the problem that the detection signal of the analog micro-drilling resistance method has excessive noise interference and cannot intuitively identify tree ring information, this research proposes a digital micro-drilling resistance method and provides a recommended hardware implementation. The digital micro-drilling resistance method adopts the photoelectric encoder instead of ADC as the signal sampling module. Through the theoretical analysis of the DC motor characteristic, the PWM closed-loop speed control, the detection principle of the digital method is given. Additionally, the experimental equipment that can complete the detection of the digital method and the analog method simultaneously is designed to carry out comparative experiments. The experimental results show that: (1) The detection results of the digital method have a better-quality signal which can intuitively identify the tree rings. (2) The average correlation coefficient reaches 0.9365 between the detection results of the digital method and the analog method. (3) The average Signal-to-Noise Ratio (SNR) of the digital method is 39.0145 dB, which is 19.2590 dB higher than that of the analog method. The average noise interference energy in the detection result of the digital method is only 1.27% of the analog method. In summary, hardware implementation of the digital micro-drilling resistance method can correctly reflect the tree ring information and significantly improve the signal quality of the micro-drilling resistance technology. This research is helping to improve the identification accuracy of micro-drilling resistance technology, and to develop the application of tree ring micro-destructive detection technology in the high-precision field.

Detection and compensation of installation eccentricity of photoelectric encoder based on double highpass filter

As a precision position sensor, the photoelectric encoder has difficulty avoiding eccentricity or tilt error in the industrial manufacturing and assembly process. At present, manual error correction is often used to adjust. The adjustment efficiency is low, and it has difficulty cooperating with other types of error compensation methods. In view of these problems, we proposed a photoelectric encoder eccentricity error detection and compensation method based on digital signal bandpass filtering that effectively corrects the signal deviation caused by the installation eccentricity in the output signal and judges the direction and magnitude of the eccentricity error to realize the encoding correction of eccentricity and inclination error of the device. The mathematical model of the eccentric error generation principle of the photoelectric encoder combined with the Lissajous figure was derived. We then demonstrated the design of a photoelectric encoder error detection platform to detect photoelectric encoders of different diameters in real time. Finally, using the advantages of field programmable gate array high-speed parallel processing, the error compensation algorithm was written into the development chip to improve the efficiency of processing the encoder output error signal. This method can adapt to the eccentricity error correction and compensation of different models of photoelectric encoders and can greatly improve the efficiency and accuracy compared with previous detection methods.

Research on Particle Swarm Compensation Method for Subdivision Error Optimization of Photoelectric Encoder Based on Parallel Iteration.

Photoelectric encoders are widely used in high-precision measurement fields such as industry and aerospace because of their high precision and reliability. In order to improve the subdivision accuracy of moiré grating signals, a particle swarm optimization compensation model for grating the subdivision error of a photoelectric encoder based on parallel iteration is proposed. In the paper, an adaptive subdivision method of a particle swarm search domain based on the honeycomb structure is proposed, and a raster signal subdivision error compensation model based on the multi-swarm particle swarm optimization algorithm based on parallel iteration is established. The optimization algorithm can effectively improve the convergence speed and system accuracy of traditional particle swarm optimization. Finally, according to the subdivision error compensation algorithm, the subdivision error of the grating system caused by the sinusoidal error in the system is quickly corrected by taking advantage of the high-speed parallel processing of the FPGA pipeline architecture. The design experiment uses a 25-bit photoelectric encoder to verify the subdivision error algorithm. The experimental results show that the actual dynamic subdivision error can be reduced to ½ before compensation, and the static subdivision error can be reduced from 1.264″ to 0.487″ before detection.

Development of Experimental Device with Data Acquisition for Thermomechanical Characterization of Polymers

Abstract The aim of this paper is to present a handmade laboratory device with data acquisition for estimating the thermomechanical characteristics (caused by dimensional changes in height) of polymeric materials. This experimental device is able to perform penetration tests, monitoring the expansion of the samples and based on experimental tests, the thermal expansivity or coefficient of thermal expansion (CTE) can be determined. A data acquisition instrument, which register (i) the deformation of the specimen, by using two displacement transducers (an inductive proximity transducer and an transmission type photoelectric linear encoder) as well as registers (ii) the temperature (at the base of the specimen and in the vicinity of the point of contact with the penetrator) is used. In order to test the device and to highlight its qualities, preliminary tests were carried out on a thermosetting polymeric material in various stages of polymerization.

Absolute Photoelectric Encoder and Its Adoption in Fertilizing Corn Machinery in Ridge Planting

Absolute photoelectric encoder has the advantages of output data only corresponding to one position, requiring absolute zero position, no need to search for zero position after power failure and restart, and no cumulative error. Firstly, the principle of the traditional absolute photoelectric encoder is analyzed, and the matrix code plate is adopted to complete the production of the 16-bit absolute photoelectric encoder code plate, which reduces the volume of the high digit encoder. Then, K9 glass is chosen for the material of code plate and slit plate, which has good light transmittance and can improve the precision of photoelectric encoder. Giving that that the performance of light source of photoelectric encoder directly determines the accuracy of photoelectric encoder, bullet SE2470 light-emitting diode is selected as the emitting light source. It has a beam angle of 18 degrees and a large operating temperature range, supporting the working wavelength of 880 nm. The receiving light source is set as the bullet photosensitive triode SD2440, which has low power consumption, with 48 degrees of receiving angle, can be directly mounted to the double-sided PCB board. Finally, the designed absolute photoelectric encoder is used in the ridge corn mechanical fertilization system, and the system controller adjusts the opening of proportional valve through the motor speed signal fed back by the photoelectric encoder. In the experiment, the absolute photoelectric encoder is tested with the help of serial debugging assistant. When the encoder does not rotate the serial port, the output data of the assistant does not change. When the encoder rotates, the result change after receiving a lot of data due to the high baud rate. The error of each fertilization tube in the mechanical fertilization system of ridge planting corn is less than 3%, the coefficient of variation is less than 0.05, and thus the economic benefit of fertilization is improved.

Improving the subdivision accuracy of photoelectric encoder using particle swarm optimization algorithm

The aim of this study is to improve the subdivision accuracy of a photoelectric encoder and reduce the effects of sinusoidal errors in signals on the measurement accuracy of the system. To this end, an optoelectronic chip that can receive grating moiré fringe signals was designed, along with an amplifier circuit with a hierarchical pipelined architecture. The photodetector array was matched with the code disk before processing the received signals. The sinusoidal errors in the signals were quantitatively analyzed. The results were used to develop a sinusoidal error-compensation method based on a particle swarm optimization (PSO) algorithm. A subdivisional error-compensation model was established to correct the errors in those signals. A rapid solution to the PSO algorithm was implemented on a field-programmable gate array, and a grating test platform was constructed for experimental verification. The peak-to-peak subdivision error of the encoder’s photoelectric signal decreased by approximately 60% from 2.98ʺ to 1.13ʺ. Therefore, the proposed scheme not only significantly improves the measurement accuracy of the photoelectric shaft angle encoder, but also contributes to its miniaturization.

Phase-locked subdivision method of digital signal based on FPGA

In order to improve the accuracy and real-time performance of the subdivision signal expression result of the photoelectric encoder in the signal dynamic measurement process, a phase-locked subdivision method of digital signal based on FPGA is proposed. The open-loop structure is used to realize the large-range detection of the grating measurement system, and the fractional frequency division method is used to realize the subdivision function of the grating moiré signal. In order to verify the effectiveness of the design, we compare the analog signal subdivision with the traditional digital phase-locked subdivision method. The experimental results show that the digital phase-locked subdivision algorithm designed in this paper can be used in the high-frequency moiré signal frequency and rate of change. The subdivision function is realized under the following conditions, which can be better applied to dynamic measurement occasions.

Error detection system of photoelectric encoder based on optical continuous closed-loop

Error detection system of photoelectric encoder based on optical continuous closed-loop

Knee Joint Curvature Detection System Based on Fiber Optic Mach-Zendler Interferometric Curvature Sensor

In the monitoring process of human motion and posture, the movement information of the knee joint is useful for diagnosis and rehabilitation evaluation. This paper presents a knee directional bending measurement device (KDBMD) using a Mach–Zehnder interferometer-based directional curvature (MZI-BDC) sensor that was fabricated by fusion-splicing a section of three-core fiber between two single-mode fibers with a core offset. Knee flexion and extension induce bending of the MZI-BDC sensor, changing its modal interference, which makes the sensor suitable for monitoring knee directional bending. Frequency-based modulation and swept source-based techniques are used in the KDBMD. The measurement range of the KDBMD is 0°–90° in both the forward and backward bending directions. For forward bending (bending direction of 0°), the sensitivity and resolution of the proposed KDBMD are 5.29 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> and 0.11 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> , respectively. For backward bending (bending direction of 180°), the sensitivity and resolution of the KDBMD are −3.11 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> and 0.12 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> , respectively. The temperature sensitivity of the KDBMD is 0.043 nm/°C. Furthermore, the performance of the KDBMD for knee-joint movement detection is compared with that of an inclinometer. The experimental results indicate that the data acquired from the KDBMD and the photoelectric encoder are consistent with regard to the accuracy and responsiveness. The proposed device, which is versatile and inexpensive to fabricate and can achieve temperature compensation, has potential for applications in gait analysis.