Search

Harmonic positioning errors can negatively affect the positioning accuracy of the ball screw drive system. This paper addresses the problem of harmonic positioning error suppression in ball-screw drives using Adaptive Feedforward Cancellation (AFC). AFC method is integrated with the dual (i.e., rotational and translational) feedback structure used in ball-screw drives. The ability of AFC to quench harmonic positioning errors originating from multiple input sources is analyzed, considering the effects of the commanded trajectory, motor torque ripples, rotary encoder measurement errors, and lead errors coming from the ball-screw mechanism. A new approach for parameter tuning of the AFC resonators is proposed which considers both the performance deterioration issue at frequencies outside the target harmonics, and also the robust stability requirement in the sense of limiting the peak loop sensitivity value. Effectiveness of the proposed AFC scheme for ball-screw drives is validated in experiments, demonstrating successful rejection of time-periodic machining force disturbances, as well as mitigation of displacement-periodic lead error and misalignment type errors. In the case of machining force rejection, 50–78% improvement is achieved in the standard deviation of the translational positioning error. In the case of position dependent disturbances, the improvement is typically in the 10–20% range and is most effective during constant velocity motion.

An absolute surface encoder for measurement of absolute in-plane position with a mode-locked femtosecond laser and a planar scale grating having variable periods along the two orthogonal directions is proposed. In the proposed method, the absolute in-plane position is measured through observing the spectra of the coupled groups of the positive and negative first-order diffracted mode-locked femtosecond laser emanated from a single point on the planar scale grating. Due to the dispersive effect of the planar scale grating having variable periods, each of the diffracted modes has a unique angle of diffraction associated with the absolute position information. Therefore, the absolute in-plane position can be detected by obtaining the peak frequencies in the optical spectra of the coupled positive and negative first-order diffracted beams received by dual detector units. The dual-detector configuration of the optical head also contributes to improving the robustness of the absolute position measurement against the angular error motion of the planar scale grating. Furthermore, interference signals capable of being used for the improvement of the absolute position measurement can be generated under the dual detector configuration. Results of the numerical calculations for the theoretical verification of the proposed method, fabrication of a scale grating having a variable period (VLS grating) with interference lithography, design and development of the optical head, as well as the results of basic experiments by using the developed optical head and the VLS grating, are reported.

This paper presents a fast tool servo (FTS) driven by a voice coil motor (VCM) with a function of self-sensing of cutting forces. Conventionally, cutting force measurement associated with a FTS system is made by integrating an additional force sensor or a dynamometer, which would make the system complicated and influence the dynamic performance of the FTS. Differing from the conventional method, the force measurement in the proposed system is achieved by detecting the current of the VCM and then obtaining the cutting force based on the electromagnetic field distribution of the VCM. Since it is not necessary to integrate additional force sensors, the main body of the FTS could be compact and the dynamics of the FTS would not be influenced by the added function of force measurement. The FTS mainly consists of an air bearing guide driven by a VCM with a stroke of 2.5 mm, an optical encoders feedback system for precision positioning and a hall current sensor for current measurement. To obtain forces from the measured currents, the magnetic field distribution of the VCM is figured out and the nonlinear relationship between the position and the magnetic field distribution is corrected. The basic performances of the FTS for positioning and force measurement were experimentally investigated. It is shown that the system could have a positioning resolution of 20 nm and a force self-sensing resolution of 5 mN based on the proposed method. The proposed method provides a new way for in-process cutting force measurement associated with FTS systems.

Due to severe working condition, unexpected failures in wind turbine gearbox become rather frequent and may lead to long downtime or even catastrophic casualties. However, traditional diagnosis techniques based on vibration, acoustic emission etc. still face some problems when they are used for failure identification of wind turbine gearbox. Encoder signal carries rich diagnostic information which may be considered as an alternative tool for the wind turbine condition monitoring. Motivated by this, the encoder signal is initially introduced for the fault diagnosis of wind turbine gear in this paper. A novel adaptive filtering method, improved maximum correlated kurtosis deconvolution adjusted (IMCKDA), is proposed to eliminate the diverse noises in encoder signal. Additionally, to overcome the limitation from the sensibility of discontinuity point and filtered signal in traditional deconvolution methods (DMs), convolution adjustment definition is introduced. And correlated Gini index (CG) is originally designed to guide the selection of filter length. Finally, the encoder signal is verified to be an alternative tool for the fault diagnosis of wind turbine gear by real experimental cases. And without any prior knowledge and the least input parameters, IMCKDA is more suitable for processing encoder signal than existing state-of-the-art DMs.

With the rapid development of micro-spacecraft, miniaturization has become a key problem in attitude control. As an angular momentum exchange actuator, a single reaction sphere can generate multi-DOF output torques and satisfy the requirement of three-axis attitude control. This enables it to be a potential alternative for micro-spacecraft attitude control system. Categorized by the driving principles, the various design techniques of reaction spheres are firstly reviewed, including the spherical motor based and the multi-driving-wheels based. Their advantages and disadvantages are summarized. In order to realize the closed-loop control of the reaction sphere, the techniques of measuring the speed and orientation of the reaction spheres are subsequently reviewed. These include rotary encoders or gyroscope with gimbal guideway, photoelectric encoding ring, machine vision, Hall sensor, color sensor and piezoelectric sensor. By promoting the popularization of the concept of reaction spheres, it is expected to provide new ideas for the miniaturization design and attitude control of micro-spacecraft.

Welding is one of the mostly used joining techniques for metal parts in the manufacturing industry. The quality of a weld is critical since it influences the lifetime of the product or people’s safety. Therefore, manufacturers are looking for reliable and cost-effective methods to monitor and control welding quality in real-time. In this paper, an attempt has been made to investigate data acquisition, integration, and visualization using heterogeneous sensor data. A semi-automatic welding system is then developed using a linear track and a Gas Metal Arc Welding (GMAW) power source. The system includes voltage, current and temperature sensors, a rotary encoder, CCD camera, and signal processing hardware and software. Welding signatures were captured using a data acquisition (DAQ) module and software was developed to store and visualize the captured data. The developed system can be used as a testbed for experimental applications or as a quality control system for the arc welding process in manufacturing shop floors.

This study aims to develop equipment and procedures to test the performance of Self-calibratable Angle device (SelfA) rotary encoder designed to detect spindle runout. Spindle runout decreases the processing and rotating-position accuracy in machine tools and can lead to a mechanical failure of the bearings inside rotary machines. To detect spindle runout, the National Institute of Advanced Industrial Science and Technology in Japan developed Self-calibratable Angle device (SelfA), which can detect the angle error by itself and has the epochal function to detect spindle runout. Experimental equipment is needed to generate a known amount of runout so that the performance of SelfA can be evaluated quantitatively. Therefore, we propose two spindle-runout generators and evaluate the amount of spindle runout generated by these generators. The first generator vibrates the main shaft directly and generates spindle runout within ±0.1 [μm] of the desired amount. The second approach vibrates the sensor side of the SelfA encoder and can generate several arbitrary amounts of spindle runout simultaneously, which are accurate to within ±0.02 [μm].

In recent year, ultra-compact and high-speed optical logic devices are extremely attractive for the scientific community and optical computing. In this paper, 2 × 1 encoder is proposed and designed using two-dimensional photonic crystal based microstructure. This logic device is constructed by point and line defects in a triangular lattice with silicon rod embedded in air host. The encoder performances are analyzed by using Finite Difference Time Domain method. The numerical results reveal that the designed micro device is capable of working accurately for different logic states. The proposed device is operated at 1520 nm, and it provides a high contrast ratio of 25.82 dB, the excellent response time of 0.2833 ps and a bit rate of around 3.52 Tbps. Hence, it is highly suitable for an optical signal processor and photonic integrated circuits.

This article presents an experimental apparatus for assessing two-scale command shaping (TSCS) as applied to mitigating undesirable vibrations during internal combustion engine (ICE) restart. The apparatus contains a three-cylinder diesel ICE coupled to a permanent magnet alternating current (PMAC) electric machine (EM) mounted on a plate and welded frame. Through Controller Area Network (CAN) messaging, the EM applies a TSCS-designed torque profile to the ICE. Data taken using on-board rotary encoders and a laser Doppler vibrometer document the effectiveness of the TSCS strategy in significantly reducing undesirable powertrain and frame vibrations.

The filling level within feed frames and the uniformity of the powder supply by feed frames for die filling have not been monitored so far during tableting processes. This study was intended to investigate if the powder filling level inside a rotary tablet press feed frame is affected by the feed frames' paddle wheel speed and/or by the turret speed. Furthermore, it was examined whether the filling level affects the resulting tablet masses while filling the respective dies. Two tableting excipients one with poor flowability and one with excellent flowability were selected as model powders. For inline analysis within the feed frame, a laser triangulator was used, which at a particular position scans the powder surface level within the filling chamber of the feed frame and, combined with the recognition of the angle position of the paddle wheel by a rotary encoder, calculates the filling level and the uniformity of the powder supply by an in-house written software. Results show that the turret speed, the paddle wheel speed and the powder characteristics may all affect the filling level within the filling chamber. The presented method is suitable for inline monitoring of the filling level in the filling chamber of the feed frame and the homogeneity of the powder supply for die filling during tableting. Moreover, a decrease of the filling level during tableting and/or a sudden refill effect of the filling chamber can be detected as well, which may occur under certain process settings at the end of the tablet production and may influence the tablet mass. The results also showed that initial deviations of the filling levels of the individual paddle wheel interspaces persisted until the end of the tableting runs, which might be one of the reasons for tablet mass deviations during production.

A study was conducted to develop a control system for variable rate application (VRA) of granular fertilizers and evaluate its performance. By the use of a microprocessor, a pneumatic cylinder and a rotary shaft encoder, the manual mechanical fertilizer rate adjustment system of a seed drill (SOLA TRISEM 294/R ESP, Model: 37193 TIPO250) was modified and transformed to a real-time automatic control system. Laboratory based tests were conducted to evaluate the developed system performance in automatically applying the predetermined desired application rates at different ground speeds, which were within the range of 3–12 km h−1. Linear regression and ANOVA tests were among the measures used to assess the accuracy of the developed system. Results of this study revealed that the developed system enabled an efficient automatic setting of the desired fertilizer application rate. The investigated operating speeds showed no significant effects on the performance of the system (P > F = 0.7968). In addition, the system exhibited an overall application rate error (difference between desired and actual application rate) of ±2.6%. The response time of the developed system was found to range between 6 and 11 ms for a change of one kilogram in the application rate.

Optical encoders are circuits that are used in the design of optical processors. To reduce the size of optical devices, it is necessary to design small-scale logic circuits. In this study an all-optical 4 × 2 encoder based on 2D photonic crystals, was designed and simulated. The simple structure of this optical encoder makes it possible to build it in optical integrated circuits. Owing to its low dimensional structure and the use of simple defect paths, the delay time of the encoder will be reduced and so, the data bit rate will be increased. The obtained transmission delay time for the proposed encoder is less than 0.1 ps. Another characteristic of the proposed optical encoder is that the output optical power in “0” logic state is very low, which increases the contrast ratio as compared to the previous works. The contrast ratio CR = 16.5 dB was obtained for the proposed encoder.

To improve precision performance of angular sensor, in this paper, research is performed on subdivision technology for a single-track absolute photoelectrical encoder. Firstly, a robust subdivision algorithm is proposed by means of processing a feature matrix of measurement which is created from multiple grating lines’ image. Secondly, simulation of anti-noise and anti-spot is established to prove that the proposed algorithm is robust theoretically. Finally, the algorithm is applied in a photoelectrical encoder for real tests, experiment result shows that the subdivision algorithm proposed in this paper is more accurate and adaptive than the traditional way. To reduce a negative precision effect caused by noises and spots, it measures angle according to multiple grating lines by assigning different weights, making those grating lines deeply noised with lower weight, and higher weight with minor noise, thus the overall accuracy is improved. With the proposed subdivision algorithm, test encoder’s standard deviation of error can be increased to 1 . 6 ″ and precision achieves up to ± 0 . 9 ″ .

In the diagnosis of electromechanical system, traditional vibration analysis methods are affected by the positioning of additional sensors. To overcome this problem, we propose a virtual phase torque (VPT) diagram method based on self-sensing motor drive system. Firstly, the q-axis current is obtained from field oriented control (FOC) process of permanent magnet synchronous motor (PMSM) drive system and used for load torque sensing. Then, fault components extracted from q-axis current and the phase angle from motor encoder are combined together to form the VPT diagram to detect the offset angle of misalignment. Therefore, misalignments in different directions can be classified. Simulations and experiments using a ball screw platform are implemented to validate the proposed method.

In this paper, we have implemented servo motor that can be controlled to rotate in even 360 degree using normal DC motor and an optical encoder. This helps to reduce the cost required to buy a servo motor spatially for heavy duty tasks. It is important to mention that the prices of servo motors increase as the rotation range of the servo is wider. In addition, the prices increase as the torque of the servo motor is higher. Therefore, using a normal DC motor with gearbox and optical encoder, will reduce the cost significantly because we have provided a high torque using the gearbox and also provided a 360-degree controllable rotation range using the optical encoder. Arduino Uno has been chosen to provide compatible system that is easy to operate and economically. This idea can be used in any application that requires servo motor with high torque or with wide rotation angle to reduce the specified cost and save some money.

The increase in the number of fatalities in road accidents, it has become important to know the reasons for the crash and use the retrieved information for further study. The purpose of the project is to develop a crash box that can be installed for diagnosis into the vehicle. It will act as an independent system, which in case of a crash; will record speed, time of accident, and location of the vehicle, for some references. This recorded data will provide valuable information during the post-crash analysis. The device will make use of components like the ATMEGA328P, a GSM module, a rotary encoder, a NEO 6M GPS module & an EEPROM. The data obtained by the device can be used by the vehicle manufacturers to analyze the reason for the crash and to find proper solutions to prevent the same in the future.

This paper is focused on the angular velocity estimation for the electric machine drive system. The angle tracking observer with filtered control variable presented in this paper uses the angular position information for the velocity estimation. The angular position is given by the optical quadrature encoder. The angle tracking observer is composed from the PI controller, first order Butterworth filter and the integrator. A tuning approach for the PI controller and flter constants is presented in this paper as well. The presented approach is compared with the angle tracking observer without Buttherworth filter and with traditional velocity estimate by the simple diference. Experimental results are gained either by the simulation or by the experiment at the real device.

This paper presents a digital interpolation module for high-resolution sinusoidal encoders. The proposed strategy performs phase-shifting manipulation on the sinusoidal encoder signals, and takes advantage of the linear sections of the absolute values of the phase-shifted sinusoidal signals. Thus, an approximately linear signal is obtained, from which the displacement can be linearly determined. Simulation result shows that the theoretical error of the proposed interpolate strategy is within 0.072° over the 360° signal period. Furthermore, a digital interpolation module is developed by implementing the interpolate strategy in a field-programmable gate array (FPGA), and performance evaluation experiments are carried out by applying it to a linear optical encoder with a pitch of 20 μm. The effectiveness of the digital interpolation module has been validated by both simulation results and experimental results.

Rotary encoder signal, as the built-in position information, possesses a wide variety of advantages over vibration signal and has aroused great interest in the field of health monitoring for rotating machinery. However, there are two major issues when attempting to detect and diagnose failures with encoder information. First of all, a series of proper signal processing methods need to be designed for fault feature extraction, which largely relies on the expert experience and domain knowledge. Furthermore, existing studies primarily concentrate on a single transform, such as instantaneous angular speed, which neglects the diversity of encoder information. In view of above deficiencies, a multivariate encoder information based convolutional neural network (MEI-CNN) is proposed for intelligent diagnosis in this paper. In this framework, three different types of dynamic encoder information are firstly acquired by analyzing and processing the raw position sequence, after that multivariate encoder information (MEI) data are constructed by data fusion. Finally, a concise and effective convolutional neural network is designed to extract discriminating features and provide diagnosis results. The proposed method not only overcomes drawbacks of traditional techniques based on vibration analysis, but also provides an intelligent way to achieve satisfactory diagnosis results. The effectiveness and superiority of MEI-CNN are validated by experimental data from a planetary gearbox test rig. The results also indicate that the proposed method may offer a promising tool for intelligent diagnosis of rotating machinery.

In this paper, mechatronic design, actuator optimization and controls of a long-stroke (20 mm) linear nano-positioner are presented. The mechatronic design is described in terms of the stage’s most prominent features regarding mechanical design, assembly, actuator configuration, and power supply. A novel air-bearing/bushing arrangement has been used in which the commonly employed double shaft arrangement is replaced with a single shaft supported by an air bearing from the bottom to constrain the roll motion. The assembly is greatly simplified by exploiting the self-aligning property of the air-bushings which are held in the housings by O-rings. Also, the footprint of the stage is reduced. Voice coil actuators (VCA) in moving magnet mode have been used in complementary double configuration for uniformity of force response. The performance objectives of previously optimized VCA’s as standalone actuators are re-evaluated in this configuration. It is observed that while the performance objectives decrease a bit, the desirability of the design point is still retained. Controller design has been made for the current control and position control loops. Heydemann’s method for the compensation of encoder quadrature detection errors is implemented. The positioning resolution of the stage as measured from the sensor output is experimentally determined to be +/−5 nm. Dynamic Error Budgeting (DEB) method has been used to analyze the contributing factors to the positioning error, and sensor broadband noise is determined to be the major contributor. The actual positioning accuracy of the stage is estimated by DEB to be 0.682 nm root-mean-square (RMS). The trajectory following accuracy is determined to be +/−15 nm. It is expected that trajectory following accuracy can substantially improve if more advanced compensation methods for encoder quadrature errors are implemented.

In this paper an 8 to 3 optical encoder will be proposed using nonlinear photonic crystal ring resonators. For realizing the proposed 8 to 3 encoder we will combine one optical waveguide with three 4-input port OR gates. In the proposed structure I j (where j = 0, 1, 2, 3, 4, 5, 6 and 7), acts as input port. And O0, O1 and O2 act as the output ports, also V is auxiliary output port to distinguish the totally OFF state from the case in which I 0 is ON. The maximum time delay of the proposed structure is about 2 ps.

Signal distortion is a key issue that limits the measurement resolution and accuracy of optical encoders. In this paper, an optical encoder based on generalized grating imaging using a two-dimensional index grating is presented. The general expression of intensity distribution for generalized grating imaging including the relative displacement between the scale grating and the reading head is derived, and the formation of the signal distortion of the optical encoder is analyzed. Then, a two-dimensional index grating, which consists of multiple grating tracks with defined offsets, is proposed to suppress the dominant third and fifth order harmonic signals. The operating principle of the two-dimensional index grating is explained in detail and a reflective optical encoder is developed. In the experiment, approximately ideal Lissajous figure of the encoder signals is obtained. Fourier analysis of the encoder signals shows that both the third and fifth order harmonic distortions are below 0.6%. Experimental results show that the interpolation error of the optical encoder is within ± 0 . 18 μ m, and the accuracy is better than ± 0 . 3 μ m over 255 mm travel range with a maximum variation of 0.136 μ m.

This paper presents information about a new device for measuring the synchronous machine load angle in laboratory conditions using the optical encoder. The prototype device is used in education for practical measuring exercises in the study course of electrical machines. Described in the article is block diagram of the measuring device. The operation principle of the device and the measurement principle of load angle of the synchronous machine presents a subject of the article, too. Moreover, the device evaluates operating mode (motor or generator) of the synchronous machine.

This study proposes a measurement system to detect spalling phenomena of ball-type constant velocity joints (CVJ). The spalling phenomena that usually occur in the inner race of a CVJ are a significant factor to the CVJ’s life, but it is very difficult to measure the spalling because the inner race is mechanically enclosed by an outer race and a cage. The developed system can not only detect the spalling but also measure the depth of adhesive wear in real time by implementing kinematics and applying force to an individual ball-type CVJ. The kinematics of a CVJ was analyzed to ensure that the measurement system operates the same as the actual CVJ. Especially, reciprocal yaw motions in the ball-type CVJ were perfectly implemented to the system. The system consists of three subsystems. The first system applies normal force to the contact points. Ball screws, spur gears attached to the motor amplify the force. The second system creates the reciprocal yaw motion with the same profiles as an actual CVJ. The third system is the measurement part, consisting of an incremental rotary encoder and a load cell. The resolution of wear depth is amplified and achieves up to 0.18°/μm. For validation, a ball-type CVJ was chosen and its spalling depth was measured. The results were verified by comparing the system measurement data with the profilometer measurement data.

Permanent magnet synchronous motors are widely used in elevator applications. This is due to their high efficiency and reliability, whereby motors are directly connected to the elevator ropes without the need of having a gearbox. This efficient system comes with some new challenges regarding the control of the motor. Since no gearbox is added to the system, the motor speed oscillations are directly transferred to the elevator cabin. This urges the need of having a smooth control algorithm to suppress the measurement noises generated by the absolute encoder especially at low speed. On the other hand, whenever the mechanical brakes are released, the speed controller needs to react quickly to prevent the cabin from rolling back. In order to overcome these challenges, this paper presents an improved speed control algorithm that reacts quickly in transient state to reduce the rollback of the cabin and slowly at steady state to ensure smooth ride. The proposed controller is based on the combination of a Model Predictive Controller (MPC) along with a torque observer. It also benefits from being computationally less demanding unlike other MPC techniques. The proposed controller is experimentally tested on an elevator and then compared to classic controllers. Finally, conclusions are drawn.

In this paper, design and prototyping of a novel, high resolution, and low-cost capacitive encoder were presented. Detailed analysis showed that the number of poles on the rotor should be as high as possible to keep the gain high and to reduce the non-linearity. Moreover, contrary to the common intuition, inter electrode gap is found to have an optimum non-zero value, corresponding to a particular number of poles, in order to maximize the gain. However, increasing number of poles brings practical problems due to manufacturing limits and digital electronic frequency load. As the electronics, micro-controller based digital signal processing is used to keep the cost as low as possible. With miniaturizing the encoder geometry as a design target, the number of plates were increased to three to increase the capacitances. One prototype, which is around 3 cm in diameter could be successfully mounted to an industry oriented DC motor and tested. The tests of this miniaturized encoder showed non-linearity error of 0.12% and resolution of 0.02 degrees. One source of the non-linearity error is the DC motor itself, and we believe that with a better setup, the error could be measured to be even better. (C) 2021 Elsevier B.V. All rights reserved.

Rice is the staple food for a large portion of the world’s population, therefore breeding improved high yielding varieties is important in the achievement of food security. An important factor in an experimental plot is quantifying the number of seedlings planted for experimenting on rice breeding, seed breeding, soil fertility and other tests. A research was carried out on a PZ-60D high-speed rice seedling transplanter fitted with a seedling number counting device based on Hall sensor, in order to analyse the marginal signal count at various transplanting speeds. The seedling counting system is divided into two parts: a counting signal acquisition device and a counting display device, the hall sensor generates the signal which is then displayed on a counting relay. To synchronize the counter signal and transplanting claws, an absolute rotary encoder was used to determine the angle of push point and transplanting claws stop position, and a logic analyzer was used to process the encoder signal into a data form readable on a computer. The installation position of counting device on the transplanting shaft was within the range of 143 ~ 202 degree. Both transplanter idle running test and field test showed that the counter device works accurately.

The BTA deep-hole drilling process is used to manufacture holes with a high length-to-diameter ratio of up to 100. A major quality criteria is the difference between the drilled hole axis and the desired, ideal straight hole axis, called center deviation. A novel measuring system is being investigated in order to measure the center deviation simultaneously to the drilling process. The deviation is determined by calculating the bending line of the boring bar using a newly developed algorithm. The measuring system consists of four subsystems: Optical fiber Bragg grating (FBG) sensors, four eddy current sensors, a rotary encoder and a displacement encoder. These subsystems enable a spatial measurement visualization of the bending line and the center deviation at the head of the boring bar. A major challenge is the separation of the bending strain from other undesired strain fractions. This is done by using an arrangement of two FBG sensors and a digital band pass filter. Experimental investigations show sufficiently good agreement between the calculated and the actual center deviation. Furthermore, drilling experiments reveal that the measurement setup can be used for additional process monitoring by using frequency analysis. Therefore, the investigated system is able to visualize and observe the center deviation. The visualization can be used to derive adequate countermeasures in order to ensure a better process control for the machine operator. The objective of the investigation is to increase the process reliability and productivity by preventing scrap parts. Within this paper, the investigated measuring system, the calculation of the center deviation and first experimental results are described.

In modern rotating machinery, rotary encoders have been widely used for the purpose of positioning and dynamic control. The study in this paper indicates that, the encoder signal, after proper processing, can be also effectively used for the health monitoring of rotating machines. In this work, a Kurtosis-guided local polynomial differentiator (KLPD) is proposed to estimate the instantaneous angular speed (IAS) of rotating machines based on the encoder signal. Compared with the central difference method, the KLPD is more robust to noise and it is able to precisely capture the weak speed jitters introduced by mechanical defects. The fault diagnosis of planetary gearbox has proven to be a challenging issue in both industry and academia. Based on the proposed KLPD, a systematic method for the fault diagnosis of planetary gearbox is proposed. In this method, residual time synchronous time averaging (RTSA) is first employed to remove the operation-related IAS components that come from normal gear meshing and non-stationary load variations, KLPD is then utilized to detect and enhance the speed jitter from the IAS residual in a data-driven manner. The effectiveness of proposed method has been validated by both simulated data and experimental data. The results demonstrate that the proposed KLPD-RTSA could not only detect fault signatures but also identify defective components, thus providing a promising tool for the health monitoring of planetary gearbox.

International audience; We address the problem of rotational velocity and acceleration estimation from incremental encoders in the presence of sensor imperfections. In the area of motion control, measurements of shaft velocity and acceleration are often affected by large disturbances with a period of one revolution that arise from sensor imperfections and degrade the performance of most closed-loop control algorithms. We present an algorithm to identify and remove such periodic perturbations online, without the need of error compensation look-up tables, and without assuming constant velocity. The proposed algorithm is evaluated via open-loop experimental tests, and its implementation in closed-loop control applications is investigated via numerical simulations through a DC motor case-study.

The use of an image detector to receive grating images and measure angle displacement via image processing is a relatively new technique, which yields higher resolution and better precision than the traditional moire fringe method. To improve the robustness of image-type angle measurement, this paper proposes a robust sub-pixel subdivision algorithm based on the least square method. Firstly, by analyzing the characteristic of grating image, a new subdivision algorithm is established based on the least square method. Secondly, the simulations of robustness are completed to prove the performance in theoretically. Lastly, the proposed algorithm is used in a typical image-type angle sensor to test the performance in real case. By test, the proposed method is shown to be more accurate and with better robust than the traditional algorithm (centroid algorithm). In a typical image-type angle sensor, it successfully achieves a resolution of 0.62″ (21-bit), 213-fold subdivision resolution, and precision of 12.85″. The results presented here may provide a theoretical and technological foundation for further research on small-size, high-resolution photographic rotary encoders.

Low frequency accelerometer calibration is generally a time consuming process and requires special considerations as well as excitation techniques due to the low frequency and low acceleration levels encountered. A limited work has been reported on this aspect so far. The paper discusses the measurement considerations associated with the implementation of optical encoder technology in low frequency accelerometer calibration. The method may be considered as primary one as reference is displacement rather than acceleration. The paper provides comparison of the optical encoder reference technique to manufacturer’s accredited primary calibration of an artifact as per ISO 16063-11. The work also discusses the measurement uncertainty associated with low frequency accelerometer calibration using an optical encoder sensor.

In the area of traction and brake control, measurements of the rotational velocity of the wheels are often affected by large periodic disturbances that arise from sensor imperfections and degrade the performance of any closed-loop control algorithm. The aim of our paper is to address this problem. First, we present a detailed analysis of the most common sensor imperfections and their effect on their measured velocity. Then, we propose an estimation scheme that greatly reduces the periodic disturbances in order to provide a better estimate of the velocity, and we validate it via numerical simulations and experiments.

In this article a new type of absolute shaft encoder is presented for the measurement of fuel level in a tank. This measurement technique is based on the principle of sensing the float arm displacement with respect to the fuel level. Here, the mechanical displacement is detected by an absolute shaft encoder and each position is represented by variant intensity of lights. Furthermore, the variation of light intensity is converted into voltage level by using a signal processing circuit (SPC) and calibrated with measured fuel level. Experimentally, it is observed that the developed prototype is able to measure the fuel level up to the range of 30 cm within the accuracy of ± 1% FSO.

Absolute optical encoders have emerged as a preferable choice of accurate positioning measurement for high-end manufacturing. To further improve the measurement accuracy of the absolute optical encoder, a novel error compensation method is proposed based on the empirical mode decomposition (EMD) method. This method is operated as follows: First, the measurement error achieved by an absolute optical encoder is decomposed into a number of intrinsic mode functions (IMFs) and the residue based on EMD. Then, a novel Hilbert marginal spectrum (HMS) based scheme is proposed to extract the underlying trend of the measurement error. Finally, the underlying trend is eliminated from the measurement error to improve the measurement accuracy. Experimental results indicate that the proposed compensation method extracts the underlying trend of the measurement error very well and improves the measurement accuracy of the absolute optical encoder.

Detection of spark ignition engine firing is an important parameter to understand proper and improper combustion inside the engine cylinder. The engine firing can be detected by direct measurement of in-cylinder pressure by using piezo-electric sensor. However, the cost of the sensor is really high. Therefore, in this paper, engine firing has been detected by analysis of instantaneous angular speed (IAS) signal from output shaft measured by cheap device like rotary encoder. The direct short time Fourier transform (STFT) is unable to detect engine firing clearly as the signal contains various frequencies (rotational frequency and its harmonics) other than engine firing frequency. Therefore, an algorithm has been developed based on complementary ensemble empirical mode decomposition (CEEMD) and followed by STFT and applied on IAS signal to detect engine firing. Moreover, a comparative study has been performed between laser vibrometer signal and IAS signal to understand the efficacy of these signals.

Conventional GPS and encoder-based solutions for the real-time position and velocity tracking of tethered aircraft in airborne wind energy (AWE) systems are known to have some practical limitations. As an alternative, the main contribution of this paper is to present a setup based on 2.4 GHz radio-frequency (RF) devices, for which there are still no reported experimental results in the literature. To this end, four estimation algorithms are formulated to a lateration problem: linear and nonlinear least squares (kinematic approaches), as well as the extended and the unscented Kalman filters (dynamic approaches). The Cramer–Rao lower bound is computed to serve as a benchmark for the filtering performance in terms of the position estimate covariance. Drawbacks of the two kinematic algorithms are discussed, followed by the advantages of using the two Kalman filters in a sensor fusion scheme that uses not only the RF rangings but also line angles and length measurements obtained from rotary encoders at the ground station. Estimates computed from field experimental data acquired with a small-scale AWE prototype are validated against the encoder measurements. The results show that setups based on RF ranging devices have many advantages over more conventional positioning techniques such as those based on line-following mechanisms with encoders, GPS and IMU, and computer vision, representing a promising solution for AWE applications.

In this paper, we propose a novel low-cost optoelectronic sensor to measure angular displacements from 0 to 360 ° utilizing diffraction principles that avoid the need for complicated software and hardware designs. The arrangement of the sensor includes a cylinder attached to a rotary element in a non-concentric design containing a fixed laser that emits light to the wall of the cylinder which is made of a high-frequency diffraction grating film. The non-concentric rotational movement of the cylinder produces a variation of the distance between the orders of the projected diffraction pattern, allowing measurements of the angular position of the shaft. The mathematical design of the encoder was validated through simulations demonstrating its viability and reliability of the proposed equations. An experimental prototype was built to verify, via interferometric techniques, the resolution in the order of 0.03 [arcsec], therefore showing the potential of a low-cost diffraction optical absolute encoder with an outstanding cost-benefit ratio.

This paper presents a methodology to transform two PWM signals into four is presented to generate the motion of the arms of a quadcopter having a variable frame geometry. Each arm can rotate around each axis by arms’ actuators. The four angles describing the angular position of the arms have been introduced. Based on the different geometric configurations of arms, the pitch and roll rotation of the quadcopter is developed. The algorithm that characterizes the control’s logic is based on few assumptions derived from the structure of the joystick’s motion and the maximum PWM width that each servo can develop corresponding to the maximum rotation of the arm. A specific geometric constraint is introduced so that all possible values of two combined PWM signals can be transformed that do not violate the maximum amount of PWM signal directed to the servo. The experimental validation is built up by using a commercial hardware characterized by four servos, a rotary encoder, one control board and an oscilloscope to validate the generated signal developed by the mathematical algorithm installed on the control board.

All-optical encoders with high response speed are required to achieve efficient information conversion in the field of ultra-fast information encoding, which can break the bottleneck of photoelectric conversion delay in traditional optical encoders and achieve a tunable bandwidth up to THz. The modifiable advantages of light path about all-optical encoder can widely satisfy the functional requirements of the modern high-precision device. This review introduces two principles of all-optical encoders, based on light propagation design and radiation source parameter design. We introduced the principle and miniaturization development of all-optical encoders based on the fabrication of two-dimensional (2D) photonic crystal defects to control optical path propagation, which can effectively use the photonic band gap effect to construct waveguide and the ring resonator to improve the coupling efficiency. In addition, we compared the previous method of the all-optical encoder with the design of radiation source parameters, and offer a practicable idea for the design of high-order encoder.

The main objective of this work is to develop a miniaturized, high accuracy, single-turn absolute, rotary encoder called ASTRAS360. Its measurement principle is based on capturing an image that uniquely identifies the rotation angle. To evaluate this angle, the image first has to be classified into its sector based on its color, and only then can the angle be regressed. Inspired by machine learning, we built a calibration setup, able to generate labeled training data automatically. We used these training data to test, characterize, and compare several machine learning algorithms for the classification and the regression. In an additional experiment, we also characterized the tolerance of our rotary encoder to eccentric mounting. Our findings demonstrate that various algorithms can perform these tasks with high accuracy and reliability; furthermore, providing extra-inputs (e.g. rotation direction) allows the machine learning algorithms to compensate for the mechanical imperfections of the rotary encoder., Measurement, 169, ISSN:0263-2241, ISSN:1873-412X

We present a novel multi-dimensional positional encoder approach that uses range-resolved interferometry (RRI) to simultaneously interrogate multiple interferometers differing in optical path length, using only a single photo detector and a single diode laser. Employing only stage-mounted non-polarising beamsplitters and reflections from three orthogonal, externally mounted, planar mirrors, three Cartesian measurement directions are formed, that when combined with measurements from a stage-mounted reference reflection, allow for three-dimensional measurements of stage motion obtained via a single access port. Through a variety of movements of a three-dimensional Piezo-electric stage over its nominal stage working range of ± 50 μm, simultaneous measurements of displacements from three orthogonal dimensions are acquired with a 10 kHz quadrature bandwidth, achieving typical displacement noise densities of below 0.4 nm/ Hz , with the noise floor dropping to below 0.1 nm/ Hz above 50 Hz, as well as high linearity with cyclic errors amplitudes well below 1 nm in all three directions.

Planetary gearbox fault diagnosis via vibration signal analysis is highly challenging, because of vibration spectral complexity due to gear fault modulation and especially time-varying transmission path effects. Rotary encoder signals contain gear fault signature, and are free of extra amplitude modulation caused by time-varying transmission path effects. Hence, encoder signal analysis provides a potentially effective approach to overcome difficulties in planetary gearbox fault diagnosis. Gear faults induce jitters in instantaneous angular speed, thus leading to changes in pulse interval of encoder signals. We proposed to analyze the order spectrum of repetitive temporal interval reciprocal between adjacent encoder pulses in the angle domain. Our proposed method is free from the algorithmic complexity of instantaneous angular speed or acceleration estimation, and more importantly addresses the difficult issue of planetary gearbox fault diagnosis under time-varying speeds. It is validated through lab experiments of a planetary gearbox under both constant and time-varying speed conditions. Localized faults on the sun, planet and ring gears are all successfully diagnosed.

Rotary forcespinning (RFS) is a simple method of fabricating fibers with a high production rate and low production cost. It can modify fibers morphology by varying polymer concentration, the solution flow rate, and the speed of induction motor. The change in the motor speed affects fibers diameter distribution. Therefore, it is necessary to implement a PID (proportional-integral-derivative) controller to maintain the stability of the speed during fibers production. A dimmer circuit to control the AC voltage supplied to the induction motor and a rotary encoder with a signal conditioner to measure the motor speed were used to regulate the motor speed. By applying the second Ziegler-Nichols tuning method, the PID controller constants, which are Kp, Ti, and Td, were obtained; Their values were 0.001242, 5, and 1.25, respectively. From the control system responses for the set points in the range of 16,000 to 28,000 rpm, it was shown that the control system has a fast response. In addition, a maximum overshoot of 345 rpm at the set point of 24,000 rpm and a maximum steady-state error of 335 rpm at the set point of 28,000 rpm were also obtained by the control system. Under a disturbance of 5 s given to the control system, the speed could be restored back to its original state within 34 s. Therefore, the speed regulation system was regarded as a good control system.

A current-independent torque equation for the permanent-magnet synchronous motor (PMSM) aiming at direct-drive servo applications is derived from a first principles model. Instead of measuring currents, all required control parameters are derived from optical incremental encoder measurements. The results are verified on a real system in test series showing the effect of static friction and proving the obtained torque model.

Linear displacement encoders are necessary in field of machine tools, metrology and electronic industry. Those devices provide nanometric resolution when constructed according to the interferometric scheme. Mathematical modeling of signal transfer process into its optical system to analyze an interference field is described. Signal intensity depending on a small displacement of moving grating phase shift correlations is considered. A sample model of the linear optical encoder is developed based on the optical scheme under research.

Skye Foundation postgraduate scholarship and the Eskom Power Plant Engineering Institute (EPPEI).

An optical encoder based on symmetric Littrow configuration is presented. Although the grating is one dimensional, both horizontal and vertical displacement can be measured simultaneously. The angle between grating vector and horizontal movement is taken into account in the measurement results, which not only decreases the requirement of installation but also decreases the cosine error. Thanks to the short grating period of 561.8 nm, a high resolution of 0.137 nm is obtained. The measurement results of optical encoder are compared with that of commercial laser interferometer. The coincident results demonstrate that the encoder should be a useful optical measurement device for detecting two-dimensional movement.

The paper presents the design of a pin-on-disc type tribometer intended for experimental characterization of static and dynamic friction behaviors for various sliding sample pairs. The normal force, slip speed, and temperature, as the main influencing parameters, are precisely controlled during experiments, by applying vertical and rotational servo-axes and an electric heater built in the rotating disc. A compact three-axial piezoelectric force sensor, placed between the vertical-axis screw drive and the friction sample, provides direct measurement of normal and tangential forces used to calculate the sample coefficient of friction. The slip speed is measured directly using an incremental encoder mounted at the rotational table. The disc temperature is measured by a built-in Pt probe, whose wires, together with the heater wires, are connected to the temperature control unit by means of slip rings. The tribometer performances are demonstrated through a study of coefficient of friction, shudder sensitivity , and wear rate characterization for a dry clutch friction material.

Presented in this paper is a development of a high-performance optical accelerometer with new configuration and small size (28 × 24 × 22 mm3) that integrates an intensity-modulated linear encoder and a patterned leaf spring. In general, the sensor possesses a strong applicability and keeps a simplified layout and low cost. High resolution, large installing tolerance, and low crosstalk are achieved by employing a 20 μm-pitch optical encoder based upon Talbot Effect. Moreover, large measurement range, high eigenfrequency, and proper sensitivity is inherent in the sensor by adopting a special-designed patterned leaf spring made by beryllium copper through wet etching. Both theoretical and FEM(Finite Element Modeling) analyses are conducted to optimize the design and verify the scheme whose results show that the measuring range, resolution and sensitivity of the sensor are ±160 g, 5 mg, and 110 mV/g, respectively. That the developed optical accelerometer is appropriate for monitoring low frequency vibration between 0 and 32 Hz within a 1.9% error margin and 0.7% crosstalk has been demonstrated by experimental testing. A potential solution to resolve the contradiction between the price and performance is offered, which may help to widespread the usage of the optical-type accelerometers.