Rotary Encoder Research Articles

Motor DC PID System Regulator for Mini Conveyor Drive Based-on Matlab

The goal of the research was to develop a Proportional Integral Derivative (PID) control DC motor system as a Matlab-based driver mini conveyor to discover how to regulate speed on an actual mini conveyor where certain factors that impact the research are not considered 0. The hardware configuration of the mini conveyor used hollow steel as a frame and two copies of the roller belt for the stretch belt conveyor. The PID control system used an empirical approach to get the DC motor's response system to determine the best fit of proportional gain, integral gain and derivative gain, and then implement those PID control systems using Matlab and Arduino as the tools for data acquisition. The speed sensor (Rotary Encoder) was mounted on the roller belt to accurately gain read speed. This sensor will submit data on every increasing in PWM to accurately measure the speed and control speed at the same time, based on the set points. The consequence of this work was the proportional gain values = 0.94624747, the Integral gain = 51.4023958 and the derivative gain = 0.01941504. The PID control, designed to monitor the response of motor DC speed on this research, had successfully reached set point value and decreased steady state error from 47.16 percent to 1.015188 percent (unloaded) and 2.2020751 percent (loaded) on the real response device.

A Stable Adaptive Gradient Descent Harmonic-Disturbance Rejection for Improving Phase-Tracking Accuracy

This paper proposes a stable adaptive gradient descent for harmonic-disturbance rejection as a tool for grid-power signal processing, magnetic rotary encoders, and permanent-magnet synchronous motors. The method can be widely applied to increase the accuracy of phase or position estimation in various systems in which harmonic disturbances exist. The proposed technique is based on learning the harmonic amplitudes by means of gradient descent on the feedback phase error. To compensate for the disadvantages of existing gradient-descent methods, the derivative expansion is fully developed with system transfer function integration for stable weighting update. In addition, an adaptive learning rate is also proposed based on discrete Lyapunov standard to achieve stability, and theoretical analysis is discussed. The performance of the method is evaluated by numerical simulation in MATLAB with various scenarios, and by the experiment with the rotary magnetic encoders. The results show that the proposed method achieves stability and high performance in harmonic rejection.

Design and development of robotic end-effector position measuring device

Robot end-effector position measurement is very essential to determine the error between the commanded position and actual position reached by the robot end-effector. This also ensures the error with which the robot end-effector traces the commanded path. Conventionally position measuring devices like laser trackers, coordinate measuring machine and other non-contact-based position measuring devices are widely used to measure the position of the end-effector due to their high accuracy and precision, even though they are very expensive. This paper presents a cost effective solution for the measurement of position of robot end-effector. An end-effector position measuring device is designed and developed in spherical coordinate system using two absolute rotary encoders and a draw-wire sensor. A mathematical model for the end effector position measuring device is developed to determine the position of the end-effector with respect to a reference coordinate system using 3D homogeneous transformation approach. End-effector position measuring device is tested for ABB IRB 1600 for numerous poses and for a straight line path. The newly developed end-effector position measuring device is found to be capable of measuring the end effector position with an accuracy of 2 mm and hence can be implemented in calibration of industrial robots.

Speed controller of wind turbine emulator using variable speed drive based on PI method

The wind turbine system as a power plant is growing rapidly in line with the electrical energy needs and limitations of fossil energy as a source of electrical energy. Many research has been carried out to develop wind turbine systems and improve system efficiency. Research on wind turbine systems requires wind turbine emulators to simulate the behaviour of wind turbines against changes in wind speed. In this paper presents a design of speed controller based on PI controller for a Wind Turbine Emulator (WTE) using a Variable Speed Drive (VSD). WTE consists of VSD, microcontroller, 3 phase induction motor, Permanent Magnet Synchronous Generator (PMSG) and speed sensor. PMSG speed depends on wind speed. At certain wind speeds, PMSG will rotate at a certain value. WTE will adjust the speed of the induction motor according to a certain wind speed to drive PMSG. Motor and PMSG rotation speed are measured by rotary encoder sensor as speed sensor and feedback for WTE. Proportional-integral method is used to control the speed of a 3 phase induction motor through VSD analogue input. Based on experiment result, PI controller can adjust speed of induction motor so that PMSG will rotate according to a certain wind speed. WTE with PI controller controls the speed of induction motor at settling time 9s to simulate wind speed through PMSG speed controlling.

Design and development of robotic end-effector position measuring device

Robot end-effector position measurement is very essential to determine the error between the commanded position and actual position reached by the robot end-effector. This also ensures the error with which the robot end-effector traces the commanded path. Conventionally position measuring devices like laser trackers, coordinate measuring machine and other non-contact-based position measuring devices are widely used to measure the position of the end-effector due to their high accuracy and precision, even though they are very expensive. This paper presents a cost effective solution for the measurement of position of robot end-effector. An end-effector position measuring device is designed and developed in spherical coordinate system using two absolute rotary encoders and a draw-wire sensor. A mathematical model for the end effector position measuring device is developed to determine the position of the end-effector with respect to a reference coordinate system using 3D homogeneous transformation approach. End-effector position measuring device is tested for ABB IRB 1600 for numerous poses and for a straight line path. The newly developed end-effector position measuring device is found to be capable of measuring the end effector position with an accuracy of 2 mm and hence can be implemented in calibration of industrial robots.

Design and Control of a Polycentric Knee Exoskeleton Using an Electro-Hydraulic Actuator.

An exoskeleton robot helps the wearer with mechanical forces by identifying the wearer’s intentions and requires high energy efficiency, sufficient load capacity, and a comfortable fit. However, since it is difficult to implement complex anatomical movements of the human body, most exoskeleton robots are designed simply, unlike the anatomy of real humans. This forces the wearer to accept the robot’s stiffness entirely, and to use energy inefficiently from the power source. In this paper, a simple 1 degree of freedom (DoF) structure, which was mainly used in the knees of exoskeleton robots, was designed with a polycentric (multi-axial) structure to minimize the misalignment between wearer and robot, so that torque transfer could be carried out efficiently. In addition, the overall robot system was constructed by using an electro-hydraulic actuator (EHA) to solve the problems of the energy inefficiency of conventional hydraulic actuators and the low load capacity of conventional electric actuators. After the configuration of the hardware system, the sliding mode controller was designed to address the EHA nonlinear models and the uncertainty of the plant design. This was configured as Simulink for the first verification, and the experiment was conducted by applying it to the actual model to demonstrate the performance of the sliding mode control. In this process, an optical rotary encoder was used as the main feedback sensor of the controller. The proposed polycentric knee exoskeleton robot system using the EHA was able to reach the desired target value well despite the presence of many model uncertainties.

Investigations on Graphene Platelets as Dry Lubricant and as Grease Additive for Sliding Contacts and Rolling Bearing Application

In recent years, graphene-based lubrication was in the focus of nano- and microtribological studies. While the sliding properties of graphene based dry lubrication were previously investigated on the nano- and micro-scale, few studies can be found in the literature for the application of graphene as an additive to oil and grease in rolling contacts. In order to apply graphene platelets as dry lubricants and as grease additives in machine elements, tests were carried out on a rolling bearing test rig under typical load conditions. For these investigations, multilayer graphene platelets of varied staple thickness were functionalized on angular contact ball bearing surfaces as a dry lubricant, which forms a thin film. In addition, bearings were lubricated with grease containing graphene platelets. In this case, a small ratio of graphene was dispersed with grease. The graphene platelets were divided into three groups of different thickness: 2 nm, 6–8 nm, and 11–15 nm. Additionally, the tests were compared to graphite nanoparticles (spheres with a size of 3–4 nm) as dry lubricant and graphite-containing grease. The experimental studies were carried out under oscillating motion. The respective load in the tribological contact was 1.5 GPa. During the tests, the pivoting angle was measured by utilizing a rotary encoder. In addition, the friction torque was recorded under a frequency of 0.2 Hz. As the balls’ velocity at the reversal point is zero, the lubrication conditions are critical. The dry lubricated bearings were compared to grease lubricated bearings. Additionally, the frictional properties of the respective greases were investigated by applying a sliding tribometer. In this case, a ball rotates against three contact planes, which causes a tribological contact under a contact pressure of 1 GPa. It was shown that applying graphene as a dry lubricant and as a grease additive under rolling contact conditions reduces friction significantly.

Reliability prediction of rotary encoder based on multivariate accelerated degradation modeling

The rotary encoder is an important sensor for measuring rotational motion. A step–stress accelerated degradation test (SSADT) is conducted with respect to accuracy to evaluate the reliability rapidly. The existing errors in output signals are identified as degradation indicator to characterize performance degradation. A methodology for the encoder SSADT modeling is presented. Wiener process theory with unit–to–unit variation is utilized in the model to describe the degradation process of each error. Considering the correlation among the degradation processes, a multivariate degradation modeling method is developed based on the Copula function to estimate the reliability of rotary encoder with multiple degradation indicators. The reliability of the encoder under the use–stress level is derived by combining the margin distributions and Copula function.

Electronic control for optimizing power absorption of darrieus vertical axis wind turbine by adjusting angle of attack method

This paper presents a mechanical design and electronic control for the angle of attack on the Vertical Axis Wind Turbine (VAWT) darrieus type with NACA0015 and 3 blades. This research was conducted to obtain high-efficiency absorption power on various wind speeds. The VAWT mechanical design is based on systematic calculations with a height of 150cm and a diameter of 120cm. NACA0015 airfoil with calculations in the NACA airfoil database obtained blade length of 15.892cm and width of 1.905cm. The electronic control on this system, Arduino mega controller, has input from an anemometer sensor, and rotary encoder sensor. While, the output is servo motors for 3 blade. A microprocessor control unit is programmed to control the adjustment of blade angle of attack. The angle of attack is defined by wind speed, angular speed of VAWT, and a defined TSR (Tip Speed Ratio). The angle of attack control method is PID (Proportional-Integral-Derivative) algorithm. By setting the TSR value constantly at 3-4, the angle of attack will be adapted even on any various wind speed. Expected result, the maximum power absorption will be obtained on various wind speed. This system can increase power efficiency of VAWT up to 35-40%.

A Robust 2D-SLAM Technology With Environmental Variation Adaptability

Simultaneous localization and mapping (SLAM) in complicated indoor/outdoor unknown environments is challenging. With a demand on high mobility and high integrity intelligent robotics, it is desired that the SLAM system should be portable and possibly standalone. To carry out the pose estimation as well as the mapping without relying on the information from other sensors, such as image, inertial measurement unit, rotary encoder of ground vehicle and so on, a single 2D light detection and ranging (LiDAR) is considered in this paper. In order to fulfill a robust 2D SLAM technology in unknown environments, the principal component analysis (PCA) is utilized to evaluate LiDAR scan contours and to carry out a corridor detector. The corridor detector is further extended to achieve adaptive unstable points removal, mapping probability adjustment as well as loop closure. Based on an adaptive grid map segmentation scheme, the cumulative mapping errors can obviously be reduced and a precise 2D map can be eventually carried out. Many experiments are conducted to verify the proposed method. Finally, for comparison, this paper utilizes the scan data and ground truth provided by the Computer Science and Artificial Intelligence Laboratory (CSAIL) at the Massachusetts Institute of Technology (MIT), to verify the localization precision of the proposed algorithm. Experiment shows that from the scan data in the route up to about 350 m, the maximum error can be as low as about 20 cm.

Development of Absolute Magnetic Rotary Encoder with Eccentric Rotation

Development of Absolute Magnetic Rotary Encoder with Eccentric Rotation

Measurement of the PMSM Shaft Position with An Absolute Encoder

The most critical aspect of assessing a permanent magnet synchronous motor is the problem of correctly measuring the position of the synchronous motor shaft. The purpose of this article was to show the effects of employing an absolute encoder to control a synchronous motor with permanent magnets while encountering disturbances. This problem is often overlooked, but it appears from time to time. The correct measurement of the shaft position eliminates improper motor operation characterized by jerking. The article showed that despite momentary erroneous readings of the shaft’s position, it was still possible to control the permanent magnet synchronous motor (PMSM). This also allows for correct measurement of the motor speed. This paper originally proposed an adaptive correction method for a rotary encoder.

Design, Optimization, and Compensation of a High-Precision Single-Excitation Absolute Capacitance Angular Encoder up to ±4$^{\prime\prime}$

This paper presents a single-excitation absolute capacitive rotary encoder that is small in size, lightweight, robust, and highly precise. The encoder consists of two plates: a rotor and a stator. The rotor consists of a planar coupling ring, a petal-form sensitive electrode, and a rough sensitive electrode, whereas the stator consists of a planar excitation ring and eight groups of collection electrodes. First, the two sensitive electrodes together with the eight sets of collection electrodes encode the angular position into amplitude-modulated signals, which are read out by a single-excitation electronic system. High-precision absolute position information is obtained by using the combination of 36 petal-form sensitive electrodes and a rough sensitive electrode. Then, a linear programming method is used to optimize the critical dimensions of the encoder within a limited area to achieve a miniaturized design. Finally, a harmonic frequency compensation method is used to reduce repeatable and periodical measurement errors, which are caused by manufacturing, circuit, and installation errors. A prototype is fabricated and tested on a high-precision testing turntable. The measurement results show that the resolution is 0.00015° and the accuracy over the full absolute range is 0.0022°, indicating that the encoder has considerable potential for use in high-precision applications.

A survey on design of reaction spheres and associated speed and orientation measurement technologies

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.

3D Printing of Thermoplastic‐Bonded Soft‐ and Hard‐Magnetic Composites: Magnetically Tuneable Architectures and Functional Devices

Magnetic materials are key players for the development and implementation of novel technologies. However, the integration and tunability of these materials in complex designs remain challenging due to constraints in currently available manufacturing approaches. Herein, the fabrication of 3D printing (3DP) thermoplastic‐bonded magnetic composites is investigated with both tailored geometries and magnetic properties using a customized fused deposition modeling 3D printer. First, the level of complexity that can be achieved by printing magnetic architectures with different geometries is shown. Next, it is shown that architectures with tailored magnetic properties (saturation magnetization and coercivity) can be achieved by combining prints with different magnetic properties (i.e., hard‐ and soft, or hard‐ and semi‐hard). Additionally, to demonstrate the versatility and powerfulness of fused deposition, self‐contained mechanisms, which comprise multiple parts (magnetic and nonmagnetic) without the need for assembly, are successfully fabricated. As an example, planetary magnetic gearboxes are printed with different configurations and their potential applicability as magnetic rotary encoders is demonstrated.

A geometric approach for follow-the-leader motion of serpentine manipulator

This article presents a geometric approach for path planning of serpentine manipulator for real-time control in confined spaces. Firstly, the mechanical design of a serpentine manipulator is introduced, and its kinematics is analyzed. As the serpentine manipulator usually has more than 10 degrees of freedom, the motion control and obstacle avoidance are difficult considering its inverse kinematics. Follow-the-leader is an ideal path planning method for serpentine manipulator, as the manipulator moves forward, all the sections follow the path that the tip of manipulator has passed, which simplifies the obstacle avoidance. The realization of follow-the-leader method is to find the new configurations of the manipulator that can fit the ideal path with small errors. In this article, a novel geometric approach for follow-the-leader motion is proposed to solve new configurations with high precision of location and less computation time. The method is validated through simulation and the deviation from the ideal path is analyzed, simulation results show that calculation time for per step is less than 0.5 ms for a serpentine manipulator with 10 sections. To verify the follow-the-leader method, a 13-degree-of-freedom serpentine manipulator system with 6 sections was built, and 12 magnetic rotary encoders were embedded into the universal joints to collect data of rotation angles of each section. Experimental results show that the manipulator can carry out follow-the-leader motion as expected in real time.

A New Method of Angle Measurement Error Analysis of Rotary Encoders

In this article, a method of error source analysis and detection to improve the angle measurement accuracy of rotary encoders in precision measuring instruments is proposed. The angle measurement error caused by the installation eccentricity of the grating disk and the radial error motion of the rotating shaft is analyzed, and the error model is built. The method of measuring the radial error motion is introduced, and the visual system and image processing technology is proposed to detect the eccentricity. The verification experiment by the use of an autocollimator and a polygon is carried out. The residual error after comparison within ±6″ accounts for 9% of the angle measurement error. The proposed error model is verified, and the angle measurement error can be predicted if the installation eccentricity and radial error motion are known.

Design of a joint angle measurement system for the rotary joint of a robotic arm using an Incremental Rotary Encoder

The design of a prototype system that measures the joint angles of the rotary joint of a robotic exoskeleton is presented in this work. An incremental rotary encoder is a sensor that can be connected to any rotary joint to measure the angle of rotation, speed of rotation, direction of rotation (clockwise or counter-clockwise motion) as well as the acceleration of a joint. The measurement system using a rotary encoder which generates an electrical signal either analog or digital according to the rotation movement was designed in this work. A prototype rotary joint having a 270° range of motion was fabricated with ABS plastic using 3D printing and then connected to an incremental rotary encoder to measure its speed and angle of motion. A robotic exoskeleton was then proposed to be used with the tested and developed measurement system.

Health Assessment and Fault Detection System for an Industrial Robot Using the Rotary Encoder Signal

In an industrial robot, rotary encoders have been extensively used for dynamic control and positioning. This study shows that the encoder signal, after appropriate processing, can also be efficiently utilized for the health observation of energy performance of industrial robots system. Singular spectrum analysis (SSA) and Hilbert transform (HT) is proposed in this work, for detecting weak position oscillations to estimate the instantaneous amplitudes (IA) and the instantaneous frequencies (IF) of an industrial robot based on the encoder signal. Compared with empirical mode decomposition (EMD) and HT, the singular spectrum analysis and Hilbert transform (SSAHT) outperforms empirical mode decomposition Hilbert transform (EMDHT) in terms of ability and precision to determine source noise, and it can accurately catch the weak oscillations without signal deformation in both position and speed introduced via mechanical flaws. Combined with SSA, the IA and IF of both oscillations and residual are extracted by HT. They are obtained from the robot arm movement. These features play an important role in improving the performance detecting weak oscillations and the residual, essential information to evaluate the health conditions and fault detection to serve the energy performance for the industrial robot. The efficiency of the proposed system has been verified both numerical simulation and experimental data. The outcomes prove that the proposed SSAHT can detect flaw indications and additionally, it can also identify faulty components. Thus, the study presents a promising tool for the health monitoring of an industrial robot instead of the vibration-based monitoring scheme.

A Self-Compensation Algorithm for Electromagnetic Rotary Encoder With Unbalanced Installation

An electromagnetic rotary encoder (ERE) is a kind of angular sensors using magnetic effects to measure angular positions. It is widely used in many industrial control systems because it has many advantageous characteristics: low cost, simple structure, work in a harsh environment, and high reliability. However, the output signal of ERE is always disturbed by magnetic leakage caused by the inappropriate installation of ERE. To address this problem, the paper proposed a self-compensation algorithm for induced signal which contains two parts: the first part is determining the angle positions apart from 180 electrical-degree each other by constructing the ideal output signal by the difference between the sensor output signals of the two adjacent positions, and establishing the equations of the induced voltage at both positions to obtain the residual signal induced by the electromotive force generated by the leakage flux. The second part is employing the least square method for estimating the amplitude, phase, and offset of the residual voltage. In order to verify the algorithm, the experiments of the sensor in the unbalanced installation situation are carried out, and the signal compensation algorithm is then implemented based on ERE and the high accuracy optical encoder. The experimental results show that the unbalanced installation produces a systematic error of the rotation angle and the proposed algorithm can effectively reduce the systematic errors.