Angular Position Sensor Research Articles

Output Feedback Active Fault Tolerant Control for a 3-DOF Laboratory Helicopter With Sensor Fault

In this paper, an output feedback-based active fault tolerant control (FTC) scheme is proposed for an unstable three degree-of-freedom (3-DOF) helicopter equipped only with angular position sensors, of which a single sensor can be faulty. Limited by the available outputs, existing fault estimation (FE) and FTC schemes cannot be applied to this helicopter because when the sensor measuring the elevation or travel angle is faulty, it does not satisfy the minimum-phase and matching conditions required by standard observers. To circumvent this problem, an adaptive interval observer is firstly designed as a fault detection and isolation (FDI) unit to indicate the occurrence and location of a fault, in contrast to the existing FDI methods that require a bank of observers and incur a high computational cost. Then a high-gain observer is combined with a sliding mode observer to form an FE unit that does not require the matching and minimum-phase conditions. Based on the estimate of the fault, an FTC scheme is constructed to ensure an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal{H}_{\infty}$</tex-math> </inline-formula> performance of the faulty system. Finally, physical experiments on the 3-DOF helicopter verify the effectiveness of the proposed scheme. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The 3-DOF lab helicopter serves as an ideal experimental platform for control strategies. In this paper, an active fault tolerant control (FTC) scheme is developed for a 3-DOF lab helicopter when any single sensor can be faulty. The helicopter is nonlinear and subject to external disturbances. There are only encoders measuring the attitude angles and no sensors for angular velocities. In this paper, we firstly design a fault detection and isolation (FDI) unit based on an adaptive interval observer to detect the fault and identify its location; it incurs a lower computational cost compared to existing methods that use a bank of observers. Then a high-gain observer is combined with a sliding mode observer to estimate the fault. Based on the estimate of the fault, an FTC scheme is constructed and designed using Linear Matrix Inequalities to ensure an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal{H}_{\infty}$</tex-math> </inline-formula> performance of the faulty system.

A MEMS-Based Three-Ring Capacitive Angular Position Sensor With an Absolute Zero Position Feature

A MEMS-Based Three-Ring Capacitive Angular Position Sensor With an Absolute Zero Position Feature

Fully Digitalized Optoelectronic Angular Position Sensor and Its Application in Real-Time Gait Recognition

The optoelectronic angular position sensor, as a component for integrated optical-electromechanical angle measurement, operates by converting angle position information into optical signals through a photonic code disc. Subsequently, these optical signals are transformed into electrical signals through photoelectric conversion to measure axial rotation information. This study proposes a fully digitalized optoelectronic angular position sensor, wherein Moore stripes are digitally subdivided, and high-order inner ring angle division employs Gray code encoding. A photoelectric diode array serves as the sensing element, corresponding one-to-one with the encoding channels on the code disc. The output of the photoelectric diodes is binarized through comparator processing, thus converting it into encoded electrical signals. Hardware implementation utilizes PIN photosensitive diodes as sensing elements, designs a laser driver circuit, and employs the 74HCT165 chip for serial-to-parallel conversion. The FPGA program is debugged using JTAG, and the program is solidified on an external EPCS1S18 chip through AS downloading. The LDO chips AMS1117-3.3 V and AMS1117-1.2 V power the FPGA chip. The CH341 chip is used for interface conversion between the FPGA and PC. In experiments, when the fully digitalized optoelectronic position sensor is installed, the voltage output of approximately 2.2 V meets the sensing response requirements after optical path attenuation. After data transmission, the results are correctly displayed on the host computer. The designed sensor is applied to gait recognition through tests involving single-person walking, two-person walking, and mixed walking. The results show an accuracy rate exceeding 95%, indicating its suitability for gait recognition in footprints.

A motion characteristics modeled angular position sensor by nonlinear transfer of differential capacitance for miniaturized scanning mirrors

In this paper, an angular position sensor (APS) designed for a resonant miniaturized scanning mirror (M-SM) is presented. The APS operates based on the principle of differential variable capacitance, significantly expanding the detectable bandwidth from a few hertz to several kilohertz. By modeling the motion characteristics, the sampling rates of the biaxial scanning angles are 1473.6 times and 539.4 times higher than those of conventional sensors. Initially, the motion characteristics model is presented as a simple harmonic motion, converting sampled capacitance into continuous capacitance. Subsequently, the nonparallel state of the M-SM and sensor is transformed into a parallel state through the space coordinate system transformation. Furthermore, a 2D nonlinear angle transfer function is developed to convert the differential capacitance into an angle, thereby mitigating the nonlinear errors resulting from large angles. Achieving an accuracy better than 0.014°, the measuring range expands from ±0.5729° (±10 mrad) to ±5.026° ( ± 87 mrad). Additionally, the capturing mode and tracking mode are proposed to monitor real-time angular changes of the M-SM with an accuracy of 0.017°. High-precision APSs have enhanced beam pointing accuracy and resolution and can thereby be used to advance the development of laser components, including light detection and ranging (LiDAR).

Development of a Multisensory Underactuated Prosthetic Hand With Fully Integrated Electronics

The compliance and manipulability are the crucial properties for prosthetic hands design, especially considering both the usefulness and versatility. This study presents a novel mechatronic design of an underactuated prosthetic hand named HIT-VI hand. It consists of four modular underactuated fingers, one opposite thumb, and a set of multisensory embedded control system. Each modular finger uses one dc motor to drive its two active joints and one passive joint. Due to the use of an underactuated nine-bar mechanism, it can execute anthropomorphic coupled motion and self-adaptive motion. The hand contains 39 distributed force sensors, 10 angular position sensors, 6 current sensors, 1 temperature sensor, and 1 inertial measurement unit (IMU). The multisensory system enables the prosthetic hand to achieve intelligent position/force/current control. The fully integrated mechatronic design makes the prosthetic hand similar to an adult hand in size, weight, and appearance. Based on the kinematics and statics, the stability analysis of the prosthetic hand is carried out. Furthermore, the experiments executing the activities of daily living validate that the proposed hand has a respectable compliance and manipulability.

Automatic Control System of Manipulator Clamping Angle Based on Machine Vision

In order to shorten the time it takes for the manipulator components to reach the preset position and avoid the behavior state of excessively increasing the gripping angle, an automatic control system for the gripping angle of the manipulator based on machine vision is designed. According to the motion state of the mechanical components of the gripper, the connection sensitivity of the angular position sensor is controlled, and then the tension and pressure control structure is used to complete the on-demand adjustment of the clamping force action form and realize the construction of the application platform environment of the hardware structure of the automatic control system. On this basis, by grabbing the necessary manipulator operation image, following the principle of machine vision, completing the preprocessing, and then combining the kinematic functions to perform the force control switching operation and realizing the gripping force control based on machine vision, and completing the design and application of the automatic control system for the gripping angle of the manipulator. The experimental results show that when the motor driving speed is equal to 2000 PPS,4000 PPS, and 6000 PPS, the consumption time required for the manipulator components to reach the preset position will not exceed 9.5s. Compared with the double closed-loop control system, it is more in line with the application requirements of effectively controlling the behavior of the clamping angle.

Motion profile and control design of fast steering mirror for backscanning step and stare imaging.

Fast steering mirrors (FSMs) have been used for decades to improve the performance of electro-optical imaging systems, such as airborne imaging systems and space-based optical surveillance systems. With the advantage of increasing the accuracy of image motion compensation and the efficiency of scanning imaging, backscanning step-and-stare imaging has become the main approach to realizing wide-area surveillance for airborne imaging systems. According to the operating mode and motion profile of the FSM in the imaging system, a combined optimized profile (COP) is designed to avoid abrupt changes in the velocity and acceleration of the FSM. The angular position sensor based on a four-quadrant detector is used in FSMs to expand the measuring range and cut the cost at the expense of larger measurement noise. Combining a Kalman filter with a disturbance observer and zero-phase error tracking control, a control method is proposed to improve the control precision and bandwidth while suppressing measurement noise. Simulation and experimental results show that the profile designed by COP is smooth enough to meet the special requirements of FSM's backscanning image motion compensation and that the Kalman filter-based FSM control method can significantly improve the control accuracy.

A Multivector Variable Area Type Capacitive Angular Displacement Encoder Based on a Rotating Electric Field and Improvement of Its Demodulation Method

The problems of the traditional type grating angular displacement encoder make it difficult to balance the measurement performance of miniaturization, high precision and high resolution, and the ability to resist vibration and shock is poor. In this article, a multivector variable-area capacitive angular displacement encoder based on a rotating electric field is proposed. Based on the principle of constructing a rotating electric field, a three-layer transmissive sensing structure with upper and lower layers of electrode plates and a modulation rotor as the middle layer is proposed and designed. A single-channel signal is used as the input excitation signal of the capacitive sensor to avoid the problem of mismatching multiple input signals. A pair of quadrature signals reflecting the spatial angle information is obtained through electric field demodulation and differential processing. The phase demodulation method based on the time scale is further adopted to improve the precision of demodulation. Simulations and experiments show that the sensor has a diameter of 50 mm, a thickness of 5 mm, a resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.81''$ </tex-math></inline-formula> , an accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5''$ </tex-math></inline-formula> , and a maximum nonlinear error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40''$ </tex-math></inline-formula> . The design is verified to be feasible, which provides a new solution for capacitive angular position sensor design.

A Distributed Method for Self-Calibration of Magnetoresistive Angular Position Sensor within a Servo System

Magnetoresistive angle position sensors are, beside Hall effect sensors, especially suitable for usage within servo systems due to their reliability, longevity, and resilience to unfavorable environmental conditions. The proposed distributed method for self-calibration of magnetoresistive angular position sensor uses the data collected during the highest allowed speed shaft movement for the identification of the measurement process model parameters. Data acquisition and initial data processing have been realized as a part of the control process of the servo system, whereas the identification of the model parameters is a service of an application server. The method of minimizing of the sum of algebraic distances of the sensor readings and the parametrized model is employed for the identification of parameters of linear compensation, whereas the average shaft rotation speed has been used as a high precision reference for the identification of parameters of harmonic compensation. The proposed method, in addition to a fast convergence, provides for the increase in measurement accuracy for an order of magnitude. Experimentally obtained measurement uncertainty was better than 0.5°, with the residual variance less than 0.02°, comparable to the sensor resolution.

North alignment of multi-rotating systems using a known fixed point

This article deals with multi-rotating systems cooperation and their measurements exchange. We investigate the geographic north alignment in rotating systems such as antenna pedestals, positioners, etcEach system contains some angular position sensors that make measurements based on their local zero angles. These measurements cannot be used by other systems. Therefore, the alignment of these rotating systems with respect to the common angle is necessary, such that all measurements are made based on this common angle. In this paper, we introduce a method for the north alignment considering a known fixed point. For this purpose, we propose an efficient approach for finding the angle between the north direction and the zero angle of these systems. Both the spherical and ellipsoidal Earth models are considered. The results accuracy is also analyzed and the effect of each rotation axis not being perpendicular to the Earth surface is investigated. The proposed approach is shown to be extremely accurate while being simple. Finally, the significance of the proposed approach is validated through several experiments.

Type-III resolver-to-digital converter using synchronous demodulation / Tipo-III conversor resolver-para-digital utilizando a desmodulação síncrona

Resolver is an angular position sensor widely used in applications such as electric/hybrid vehicles, CNCs, antennas and robotics. However, the estimation of the angular position from resolver outputs is more difficult than the analysis of encoder signals, and it is still an open question. Most algorithms proposed in literature are based on type-I or type-II angle tracking ob- servers. Some type-III observers were proposed, but they require a high sampling frequency. This paper explores the use of synchronous demodulation of the resolver outputs to simplify the implementation of a type-III angle tracking observer. The resolver outputs are sampled at the peaks and valleys of the excitation resolver signal, being easy to get sine and cosine of the angular position. The proposed approach reduces the computational cost and the required sampling frequency to implement the type-III observer. Simulation and experimental results prove the accuracy of the proposed approach.

TUNING THE ANGULAR SPEED CONTROLLER OF THE REACTIVE FLYWHEEL OF THE NANOSATELLITE ORIENTATION SYSTEM

The paper describes reactive flywheels based on brushless magnetoelectric motors for controlling the spatial orientation of satellites, developed at the Institute of Electrodynamics of the National Academy of Sciences of Ukraine. The main attention is paid to the problem of implementing a rotor angular speed and position sensor, provided that it can be integrated into the motor design. The influence of the number of feedback signal pulses per one revolution of the motor shaft on the tuning of the reactive flywheel angular speed controller is studied under the condition that the ripple range at the controller output signal is limited at a given level. The dependences of the filter time constant and the controller gains on the value of the reactive flywheel angular speed and on the number of feedback signal pulses per revolution are obtained. Ref. 8, fig. 5, table.

Generalized Nonoverlapping Tooth Coil Winding Method for Variable Reluctance Resolvers

Variable reluctance (VR) resolver is an angular position sensor, which is commonly used in the automotive industry. In this article, a general method for determining the winding configuration of VR resolvers is proposed, which eases the manufacturing process. At first, the operational principle of conventional winding has been presented using mathematical formulations. Following that, the nonoverlapping tooth coil winding method, as the ideal winding option for VR resolver, has been extended, which can be applied to the VR resolver with arbitrary poles and stator tooth numbers. The method of determining the reference and signal windings presented and used to determine the winding for a two, six, and eight poles resolvers. The validity of the proposed winding is investigated using 3-D time stepping finite element analysis and experimental measurements.

CONSTRUCTION OF ROTOR ANGLE IDENTIFIER IN VECTOR CONTROL SYSTEMS OF DOUBLE FEED MACHINES

In asynchronous electric drives with vector control on the rotor, it is necessary to calculate the value of the sine and cosine of the angle of rotation of the rotor relative to the stator to form control actions. When using angle sensors, complex structural tasks can arise — placement and reliable mounting of the sensor on the shaft and, accordingly, the task of the overall layout of the unit. For high-power machines, the tasks of developing and creating the design of the sensor itself arise. If serial rotor angular position sensors can be used, the task of placing and mounting the sensor is no less difficult. In these cases it is necessary to deduce the second end of a shaft from the case of the engine with contact rings that complicates its design. Therefore, the urgent need to create more reliable electric drives with vector control systems on the rotor is the synthesis of identifiers of the angle of rotation of the rotor.&#x0D; Identifiers are known whose calculation algorithms are based on determining the projections of the flow coupling vectors. In the work with the use of coordinate transducers of projections of stator or rotor current vectors and equations of electromagnetic circuits of an asynchronous machine, the synthesis and subsequent analysis of the properties of the rotor position angle identifier in vector control systems of dual power machines is performed. New equations of the identifier of flux couplings are received, its stability is investigated and on conditions of stability types of electric drives in which it is possible to apply the offered identifier are defined. The stability of the vector control system and sufficient identification accuracy when using the proposed equations and functions are confirmed by the method of mathematical modeling of the recommended electric drive systems in different operating modes.

An Adaptive Mechatronic Exoskeleton for Force-Controlled Finger Rehabilitation.

This paper presents a novel mechatronic exoskeleton architecture for finger rehabilitation. The system consists of an underactuated kinematic structure that enables the exoskeleton to act as an adaptive finger stimulator. The exoskeleton has sensors for motion detection and control. The proposed architecture offers three main advantages. First, the exoskeleton enables accurate quantification of subject-specific finger dynamics. The configuration of the exoskeleton can be fully reconstructed using measurements from three angular position sensors placed on the kinematic structure. In addition, the actuation force acting on the exoskeleton is recorded. Thus, the range of motion (ROM) and the force and torque trajectories of each finger joint can be determined. Second, the adaptive kinematic structure allows the patient to perform various functional tasks. The force control of the exoskeleton acts like a safeguard and limits the maximum possible joint torques during finger movement. Last, the system is compact, lightweight and does not require extensive peripherals. Due to its safety features, it is easy to use in the home. Applicability was tested in three healthy subjects.

High-speed wide-angle interleaved scanning technique for a 3D imaging lidar

In this paper, we describe a novel interleaved scanner for an eye-safe 3D scanning lidar system to measure aerodynamic phenomena in a wind tunnel using elastic backscatter from seeding particles. The scanner assembly consists of a rotating polygon scanner for line scanning along the fast axis, a galvanometer (galvo) scanner for scanning along the slow axis, angular position sensors, and motor controllers. The polygon scanner sweeps the lidar beam at up to 10,000 lines/s across a 27 deg angular field of regard in the fast axis, while the galvo scanner covers an angular range of 20 deg in the slow axis. Using this scanner, the lidar can perform nonintrusive flow visualization, velocimetry, and hard target mapping at millimeter-scale spatial resolution to a standoff range of 5 m at an update rate of 50 Hz for the full field of regard. An interleaved scanning methodology for the acquisition of two snapshots of 3D lidar intensity data with a 100 µs time offset is discussed. The design of the control and data acquisition electronics is described. The effects of rapid scanning on the response of a narrow field-of-view lidar are addressed. The design of the scanner is scalable and can be tailored to meet the requirements of other applications by increasing or decreasing the standoff range, angular field of regard, and scan rate.

The Choice of Criteria and Methods to Estimate the Quality of the Angular Sensor Based on the Effect of Nuclear Magnetic Resonance

To adjust the stabilization systems that ensure the operation of the angular position or rate sensor based on the effect of nuclear magnetic resonance, it is required to choose the criteria for the quality assessing of sensor’s operation. The article presents the criteria of the quality of the angular sensor operating as a self-oscillation system. It is shown that the accuracy of the angular sensor increases when the proposed criteria are met.

Uncertainty estimation in calibration of instruments of model turbine test facility

The experimental testing of the reduced scale model turbine is an important phase to obtain the performance characteristics of the prototype because the characteristics are difficult to obtain from theoretical calculations. A specially designed hydraulic test facility following the guidelines of international standards is generally used to obtain the performance characteristics of model turbine. These characteristics are transposable to the prototype turbines. The model turbine test facility is also used for the research and development work by the designers and scientists. The accuracy of the results obtained is entirely dependent on the instrumentation, calibration and uncertainty estimation. In the present study, the instrumentation and calibration procedure of a model Francis turbine test facility is presented by following the guidelines of international electrotechnical commission. The instruments such as flow meter, inlet and differential pressure transducers, torque sensors, angular position sensors and temperature sensors are calibrated using primary and secondary methods. The calibration curves and uncertainties involved in different instruments are obtained and presented. Both systematic and random uncertainties involved in hydraulic efficiency measurements are also presented. The maximum total uncertainty is ±0.15% in the hydraulic efficiency of model Francis turbine at best efficiency point.

Study on the viability of a microminiature inductive angular position sensor using low-cost fabrication techniques

In this study, we propose an inductive angular position sensor comprising thin film, gold spiral inductors on ceramic chips as an alternative to the current state of the art which suffers from limitations in terms of the scope for micro-miniaturization. The geometry of the transmitter and receiver coils, operating frequency, and the air gap between the transmitter and sense coils all influence the performance of the sensor. Herein, we design and fabricate an inductive position sensor based on micro inductors normally employed in the resonant elements of microwave circuits and as chokes in power sources. We use these inductors as both a magnetic field receiver and transmitter and quantify the generated electromagnetic field. This approach has the advantage of providing angular sensing while being substantially easier and more economical to fabricate compared to currently available commercial sensors. The sensor is designed in such a way that the inductance versus angular displacement possesses an arctangent relationship. Due to this feature, the angular position is obtained easily from the sensor signal without the need for complex mathematical calculations, which is not the case for most of the planar coil-based sensors. A prototype of the proposed sensor has been developed and tested. The sensor has an accuracy comparable with much larger existing sensors (residual error standard deviation 2.55% of full scale), a high linearity (R2 99.3%) and a low sensitivity to injected noise (0.5%). This low-cost, miniature, rotary position sensor could find numerous applications especially in the modern field of automotive engineering.

Design and Calibration of a Novel Angular Position Sensor Based on BP Neural Network

Design and Calibration of a Novel Angular Position Sensor Based on BP Neural Network