Full-circle Range Research Articles

Full-circle localization diagnosis of rolling bearing outer ring defects based on double-vibration signal fusion

Localization diagnosis (LD) of rolling bearing outer ring defects plays an important role in failure cause analysis and residual life prediction. This study aims to solve three main issues in the existing LD methods. Firstly, a full-circle functional relationship between outer ring defect and localization index is established based on the dynamics simulation analysis of bearing system. Secondly, the generation mechanism and solution method of the positioning datum are determined using a novel finite element transient dynamic model. Furthermore, variation law of the initial direction of the fault impact under different angular positions is investigated. Lastly, a general localization rule applicable to outer ring defects in the full-circle range is proposed. Therefore, a full-circle localization formula for outer ring defects based on the characteristic fusion of horizontal–vertical signals is proposed. Simulation results verify the effectiveness of the proposed localization formula. Additionally, a morphological filter for LD is investigated to resolve the diagnostic error caused by noise interference in the actual signal. Experimental results show that the presented method can considerably improve diagnostic accuracy.

An Improved Magnetic Transduction Scheme and Electronic Processing for Sensing Rotary-Shaft Position Over Full-Circle Range

Angular position of a through-shaft is an important measurand whose value needs to be accurately estimated in a number of industrial scenarios. This paper brings forward the design, analysis and hardware-based evaluation of a new magnetic transduction module and associated electronics for through-shaft angle estimation. The proposed transduction module enables non-contact and full-circle operation using an intelligent arrangement of magnetic discs and two Hall sensors. This easy-to-fabricate module is analyzed and its (nonlinear) characteristics are derived. Optimal specifications for the transducer are also ascertained using this analysis. Further, a simple electronic processor, implementing new linearization function, is employed to realize an automated through-shaft sensing system. This system retains all merits of magnetic sensor and reluctance techniques and eliminated many issues of the previous through-shaft sensor systems. A hardware prototype of the transducer and electronic processor is built and tested. Test results show that the developed system can measure through-shaft angle over 360° range with error < 0.8%. The paper, in its final part, discusses the comparison of the developed scheme with prior art as well as the recommendations for fabricating an equivalent industrial model of the proposed system.

Performance Investigation of a Simplified TMRBased Rotary Position Sensing System

Measurement of angular position of a rotating shaft is required in several industrial, medical, and aerospace applications. In this article, a simplified position measurement system using Tunneling Magneto-Resistance (TMR) sensing technique is proposed to cater this objective. The TMR-based rotary position-sensing system (TRPS) uses inherent merits of the TMR technology for shaft angle measurement. It processes the sensor signals, possessing sine-cosine behavior, and renders a linearly varying output. The TRPS is primarily designed and tested for angle measurement over full-circle range. However, a modified design, with lower component count, is also proposed and verified for half-circle range measurements. The circuit architecture of the TRPS and its operation are discussed in detail. Owing to its faster response, the TRPS can be used to track the angular position of the shaft, even at high speeds. The effects of non-idealities of sensor and circuit, on the TRPS output, are analyzed. Several simulation- and emulation-based tests are conducted to validate the suitability of the TRPS for static and dynamic inputs. The TRPS is found to be useful for angle measurement up to shaft speeds of 12000 rpm. A TRPS hardware is fabricated using AAT003-10E TMR integrated circuit (IC) as the sensor and tested. Experiments show that the TRPS output varies linearly for 360° range. Finally, a performance comparison study is carried out to highlight the achievements of the TRPS over the existing schemes.

Design and experimental study of the biorthogonal linkage laser self-mixing angle sensor

In order to make up the defects of low-resolution and narrow measurement range ubiquitous in the current angle-measurement method, a biorthogonal linkage laser self-mixing angle sensor is designed for the micro-radian angular measurement over the full-circle range by taking the Acrylonitrile–butadiene–styrene resin as the material and adopting the 3D printing technology. The experimental results are in excellent agreement with the theoretical values, of which implies that the tool is capable of measuring the angle with effectively and accurately. Furthermore, the deviation degree between the measured and actual angle, and the experimental error are further investigated and discussed. As a result, this self-mixing angle sensor can greatly improve the angle measurement accuracy and reduce the experimental error rate. In the case of different rotating angles of 250 and 500 μrad, which corresponding to the angular resolution is better than 29.53 μrad and the relative error can be smaller than 3.18×10−4 %.

A Novel Linearizing Signal Conditioner for Half-Bridge Based TMR Angle Sensor

This paper proposes a novel signal conditioning circuit for half-bridge topology based Tunneling Magneto-Resistance (TMR) angle sensor. The resistances of TMR angle sensor vary as a sine/cosine function of the shaft angle. The proposed circuit employs an enhanced dual-slope technique to process these non-linear resistance variations and render a linear digital output for full-circle range. The circuit uses easily available and low-cost circuit components, and a novel linearization logic in its architecture. It possesses low dependence on many circuit and sensor non-idealities. Further, a novel algorithm is proposed to reduce the measurement error due the mismatch in nominal resistances of the TMR sensor. The working of the circuit is verified using simulation as well as experimental studies. The maximum non-linearity in the circuit output, observed with expected sine/cosine characteristic, is 0.038 %. Later, a shaft angle sensing unit, employing AAT003-10E half-bridge TMR angle sensor IC, is designed, built, and characterized. The interfacing studies showcase the capability of the developed signal conditioning circuit for linearizing practical TMR angle sensors. The efficacy of the compensation algorithm is also proved in the experimentation.

Oscillator-Less Direct-Digital Front-End Realizing Ratiometric Linearization Schemes for TMR-Based Angle Sensor

A simple oscillator-less direct-digital front end (ODF) for tunneling magnetoresistance (TMR) angle sensor is presented in this paper. The TMR sensor outputs vary as sine and cosine functions of the shaft angle to be measured. To these outputs, the ODF applies ratiometric-based techniques to obtain a linear output for the full-circle range. The first ratiometric linearization scheme (RLS-A) provides a linear output which is insensitive to the variation of sensor transformation constant. Alternatively, the second ratiometric linearization scheme (RLS-B) renders output with minimal nonlinearity (0.009%). The ODF does not require any sinusoidal oscillator for its operation, thereby eradicating one major error source. Furthermore, the proposed methodology uses dc excitation for the sensor. This makes the ODF insensitive to the sensor parasitic capacitances. The operation of the ODF and two linearizing schemes are explained in detail. Mathematical evaluation of the schemes is conducted to determine the effects of different sensor and circuit nonidealities. The static and dynamic performances of the ODF are studied using emulated TMR sensor outputs. The results establish a linear transfer-characteristic over 360° range. Tests are also conducted to quantify the effect of nonidealities like phase imbalance in sensor outputs and deviation in sensor transformation-constant. A close degree of agreement was observed between the emulation results and the mathematical analysis performed. Later, the ODF is interfaced and tested with a prototype TMR-based shaft-angle measurement unit. The interfacing results underline the fact that the developed ODF acts as an efficient linearizer for TMR angle sensors.

A Linear Direct-Digital Converter for Sinusoidal Encoders

This paper proposes a novel linear direct-digital converter for sinusoidal encoders (LDCS) to measure the angular position of a rotating shaft. The outputs of a sinusoidal encoder vary as sine and cosine functions of the shaft angle. The proposed LDCS, which has a low component count, processes these outputs and renders a linear accurate direct-digital output for full-circle range. The LDCS is suitable for both static and dynamic measurements of the shaft angular position. The working principle of the LDCS is mathematically derived and explained in this paper. An elaborate evaluation of non-ideal parameters affecting the LDCS operation is carried out and reported. Furthermore, the static and dynamic performances of the LDCS are verified using simulation and emulation studies. The output nonlinearity obtained during emulation studies, for static measurement, is 0.027 %. A close agreement between simulation and emulation results is observed during these studies. Later, a tunneling magnetoresistance (TMR) angle sensing unit which acts as a representative sinusoidal encoder is fabricated. The LDCS is interfaced with the sensing unit, and several experimental tests are carried out. The worst-case nonlinearity in the static measurement of shaft angle is 0.29 %. Additional tests which study the dynamic performance and effect of mechanical misalignments of the combined TMR-LDCS system is also revealed in this paper.

A Noncontact Angle Sensor Based on Eddy Current Technique

This paper presents the design and development of a novel, linear, eddy current-based noncontact angle sensor with 360° range. Although the eddy current proximity sensors are known for high reliability, resolution, and insensitivity to moisture and oil, the approach has not been exploited to develop full-circle range angle sensors with such features. The proposed sensor consists of a rotary conducive hollow tube (e.g., made of aluminum) part and a stationary part with four identical flexible coils. The tube has a simple but special groove. The position of the groove modifies the value of the inductance of the stationary coil as a function of the sensing angle. The design is such that the inductance of each coil varies linearly for a specified range of the angle. From this piecewise linear characteristic, an output that is linear for the full-circle range is obtained using a simple yet effective algorithm. A suitable signal conditioning circuit is developed to obtain an output that is proportional to the change in the inductance of the coil. In order to optimize the design, first, the sensor structure was studied using finite-element analysis. Then, a prototype of the sensor was built and tested in the laboratory. The prototype sensor has a resolution of 0.08° and a maximum nonlinearity of 0.25%. The possible sources of error of the sensor have been analyzed and quantified. The sensor has no electrical contact to the rotary part and its output is immune to moisture, dust, and oil.

Full-circle range and microradian resolution angle measurement using the orthogonal mirror self-mixing interferometry.

The self-mixing technique based on the traditional reflecting mirror has been demonstrated with great merit for angle sensing applications. In order to solve the problems of the narrow measurement angle range and low resolution in traditional angle measurement method, we proposed an angle measurement system using orthogonal mirror self-mixing interferometry combine an orthogonal mirror with designed mechanical linkage. It overcomes the shortcomings of traditional angle measurement methods and realized the angle measurement with microradian resolution in a full-circle range of 0 rad to 2π rad. In the experiment, the measurement resolution can reach to 5.27 µrad and the absolute error can lower to ± 0.011µrad, which satisfies the requirements of most high accuracy angle measurement.

Absolute angle measurement using a phase-encoded binary graduated disk

A new absolute angle measurement method using a phase-encoded binary graduated disk (PE-BGD) is presented. An absolute position binary code (APBC) is encoded by shifting the positions of binary patterns, and can be sub-divided by detecting their positions with sub-pixel resolution of a multi-element detector. Using an n-bit linear shift feedback register, we expressed a recursive APBC dividing the full circle by 2n−1 angular positions. An experimental setup was constructed with a microscopic imaging system, a rotation stage having a precision angle encoder, and two kinds of PE-BGDs which employed 10-bit and 13-bit APBC. The resolution of the APBC, which equals to signal period of the PE-BGD, used in each disk is 0.352° and 0.044°, respectively. We evaluated its performance by comparing the readouts of the proposed system and the angle encoder, throughout the full circle range and for one signal period. In the full circle range, the differences between two measurement systems were less than 1/50 of the resolution of the APBC. We also proved that the absolute angle could be measured with small nonlinearity error, which was less than 1/600 of the signal period.

New Signal Conditioning Circuit for MR Angle Transducers With Full-Circle Range

An efficient signal conditioning (SC) scheme that helps to obtain a linear output from a magnetoresistive (MR) angle sensor for 0°-360° range is presented in this paper. Most of the existing MR angle sensors have a sine/cosine relationship between the output and sensing angle, but a linear characteristic will be very useful. The new SC circuit of the proposed transducer accepts and processes output signals from an MR sensor that is sine/cosine in nature and gives an output directly proportional to the sensing angle. The sensitivity of the transducer output to variations in different circuit and mechanical parameters has been analyzed in detail, and their effect has been quantified. The functionality of the SC has been studied using SPICE simulations. A prototype of the proposed SC circuit has been built and tested using emulated sensor output signals. The output of the prototype circuit was linear from 0° to 360°, and worst case error was less than 0.08%. An angle sensor unit has been built using an MR sensor IC, interfaced to the SC circuit and tested. As expected, the output was found to be linear for a full-circle range.

Note: High precision angle generator using multiple ultrasonic motors and a self-calibratable encoder

We present an angle generator with high resolution and accuracy, which uses multiple ultrasonic motors and a self-calibratable encoder. A cylindrical air bearing guides a rotational motion, and the ultrasonic motors achieve high resolution over the full circle range with a simple configuration. The self-calibratable encoder can compensate the scale error of a divided circle (signal period: 20") effectively by applying the equal-division-averaged method. The angle generator configures a position feedback control loop using the readout of the encoder. By combining the ac and dc operation mode, the angle generator produced stepwise angular motion with 0.005" resolution. We also evaluated the performance of the angle generator using a precision angle encoder and an autocollimator. The expanded uncertainty (k = 2) in the angle generation was estimated less than 0.03", which included the calibrated scale error and the nonlinearity error.

An accurate low-cost capacitive absolute angular-position sensor with a full-circle range

A novel high-performance smart capacitive angular-position sensor with a full-circle measurement range is presented. The sensor is mainly composed of three parts: the capacitive sensing element, a signal processor and a microcontroller. Using an appropriate algorithm, the effects of the main undesired influences are eliminated or strongly reduced. The measurement range covers the full-circle range (360/spl deg/). The structure of the sensing element is optimized to reduce the influence of the electric-field-bending effect and the mechanical errors. The signal processor has a multicapacitance input and a single period-modulated output, and includes a nearly linear capacitance/period converter. The microcontroller acquires output data from the processor, calculates the positions and optionally communicates with the outside digital world. The resolution of the smart capacitive angular-position sensor is 1.5 arcsec, and the nonlinearity is less than /spl plusmn/58 arcsec over the 0-360/spl deg/ range for a measurement time of 140 ms.