Digital measurement of shaft rotation speed based on encoder signal: error analysis and adaptive method

Induction motors are broadly used as drivers of a large variety of industrial equipment. A proper measurement of the motor rotation speed is essential to monitor the performance of most industrial drives. As an example, the measurement of rotor speed is a simple and broadly used industrial method to estimate the motor’s efficiency or mechanical load. In this work, a new low-cost non-intrusive method for in-field motor speed measurement, based on the spectral analysis of the motor audible noise, is proposed. The motor noise is acquired using a smartphone and processed by a MATLAB-based routine, which determines the rotation speed by identifying the rotor shaft mechanical frequency from the harmonic spectrum of the noise signal. This work intends to test the hypothesis that the emitted motor noise, like mechanical vibrations, contains a frequency component due to the rotation speed which, to the authors’ knowledge, has thus far been disregarded for the purpose of speed measurement. The experimental results of a variety of tests, from no load to full load, including the use of a frequency converter, found that relative errors on the speed estimation were always lower than 0.151%. These findings proved the versatility, robustness, and accuracy of the proposed method.

Comparison of single and double electrostatic sensors for rotational speed measurement

Rotational speed is a key parameter for condition monitoring and control of rotating devices in many industries. This paper presents a novel measurement technique using a single electrostatic sensor coupled with autocorrelation signal processing algorithms. The characteristics of the electrostatic sensor are analyzed through Finite Element Modeling. Experimentation based performance assessment of the system for the speed measurement of shafts made of different materials, including polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyamide (PA) is reported. Effect of the size of the shaft is observed and quantified. Experimental results obtained on an experimental test rig suggest the measurement system is capable of producing repeatable rotational speed measurement with a maximum error of ±0.5% over the speed range of 600 to 3000 RPM (revolution per minute). The system performs better under the conditions of higher rotational speed and larger rotors.

Purpose. The article provides for finding solution to the problem of developing and improving the means for measuring tachometric data of the previously created information and measuring system for testing hydraulic locomotive transmission by substantiating the optimal sensor design and signal processing algorithms. At the same time first of all it is necessary to start from the possibility of modifying the already existing test bench for hydraulic locomotive transmissions at the Dnipropetrovsk diesel locomotive repair plant «Promteplovoz». Methodology. In the work, the researchers proposed a methodology for modifying the sensor design and the algorithm for processing its signals. It is grounded on previous developments of tachometric sensor of the optical type on the basis of D-2MMU-2 sensor of the microprocessor automated test bench system of hydraulic locomotive transmission in the locomotive repair plant conditions. Selection of the necessary measurement algorithm and the number of sensor teeth is substantiated by calculating instrumental and methodological errors. Also, the studies aimed at identifying the source of interference in the measurement of rotational speed are described and solution for its elimination has been found. Findings. For the designed rotation speed sensor of the optical type based on the existing D-2MMU-2 sensor, the authors analyzed the dependence of the methodological and instrumental errors. Based on the obtained data more rational variant of the rotation speed calculation algorithm is proposed, and the number of teeth of the sensor disk is justified. Further, the main source of measurement interference was established and a method for improving the hardware of the hydraulic locomotive test bench was proposed. Originality. There were conducted the studies according to the methodological and instrumental errors of the designed rotation speed of sensor. The mechanisms of interference filtering arising from the sensor rotation speed fixing were proposed. Additional studies have shown the need for a hardware revision of signal conditioner scheme. Practical value. Conducted studies make it possible to establish a rational number of sensor disk teeth, which allows improving the measurement algorithm. It was also performed a hardware improvement of signal conditioner scheme from the sensor, helping to get rid of interferences. The results of measurements in studies are the initial data to perform further studies in order to determine the technical condition of hydraulic transmission UGP 750-1200 during factory testing after repair.

Measurement of idlers rotation speed in belt conveyors based on image data analysis for diagnostic purposes

The Polish Naval Academy has been involved in marine reciprocating combustion engines indication tests for many years. Results of researches aiming to diagnostic using of measurement of engine crankshaft unsteady angular speed are presented in the paper. Up to now, adequate accuracy of angular speed measurement had not been achieved to make proper diagnostic decision. Commercially, measurement of unsteady rotation speed has been used only in MAPEX –TV system (Torsional Vibration detector) dedicated to SULZER engines, which can detect only the one engine cylinder switch out of work without any mistakes. For several years, mostly in navigation, more often are used optic gyroscopes which work on the base of Sagnac effect, assuring angular speed measurements with resolution of 0.001o/h. Such resolution is too high than needed in piston engines diagnostic, but range of measured rotation speed is much much lower than rpm of medium-or low-speed marine diesel engines. In scope of conducted research it was decided to build a model of Sagnac interferometer prepared to measure of instantaneous angular speed in range adequate to medium speed marine diesel engines. At rotational crankshaft speed equal 750 rpm 1mV change in output voltage had been achieved for the difference of 0,4 o/sec of rotational speed. Time of measurement is equal the time which need light ray to go through distance of 100 m fibber-optic line. In practice this method do not introduce any significant phase shifts and does not limit the number of samples per revolution.

The accuracy and real-time performance of the speed measurement method were important factors influencing the accuracy of the seeding spacing monitoring. In this study, three different speed measurement methods (including GNSS (Global Navigation Satellite System) receiver speed measurement, radar speed measurement, and encoder measurement rotation speed) were used to compare and analyze the monitoring results of seeding spacing. The same monitoring system was used to calculate the seeding spacing under three different speed measurement methods. The encoder directly measured the rotation speed of the seeding disc instead of the traditional method of measuring the rotation speed of the driving wheel. The monitoring results of uniform-speed and variable-speed seeding field tests showed that the three speed measurement methods have extremely high correlations, with a correlation coefficient R > 0.95. There was small difference among the three speed measurement methods, and they all met the needs of field seeding operations. After comprehensively considering the use cost and installation complexity, it was recommended to use GNSS receiver speed measurement to monitor the speed of the seeding operation and the real-time seeding spacing.

Rotational speed is a key parameter for the condition monitoring and control of rotating equipment such as generators, electromotors, centrifugal and machine tool spindles. This paper presents the principle and application of electrostatic sensors and correlation signal processing techniques to real-time measurement of rotational speed. Experimental tests were conducted on a test rig under a range of conditions. The results suggest that the operability and accuracy of the measurement system depend on a number of factors, in particular, the distance between the electrodes and the surface of the rotating equipment. The system performs better under higher rotational speed conditions as more electrostatic charge is produced on the rotating surface.

Rotational speed measurement has increasingly become an important requirement both in the industrial and aerospace fields. This article presents a technique for rotational speed measurement based on the non-contact optical method by using superposition vortex light. To the best of our knowledge, for the first time, we realized the ultralow rotational speed measurement as low as 0.001 r/s with high accuracy based on real rotating objects. By using an optical vortex (OV) with a large topological charge up to ±65, the rotational frequency is magnified significantly. The detection system proposed in this article has a simple structure and non-contact features, including a transmitter, a receiver end, and a control and signal processing unit. Depending on the rotational speed of the target, the different sampling time is used to achieve near real-time speed acquisition. The experimental results suggest that the measurement result of the rotational speed has nothing to do with the receive angle of the receiver, and different receive distances only affect the intensity of the signal. An autocorrelation algorithm is designed which can effectively improve the signal-to-noise ratio of the detection signal. At different rotation speeds, the experimental results are in good agreement with the theoretical value. Our work fills the margin of the ultralow rotational speed measurement of RDE, and the related technique in this article may be useful in the precision mechanical testing and spatial instability targets sensing.

The acquisition of parameters plays a crucial role in rotary systems, while multi-parameter measurements with single or integrated sensing unit have distinct advantages over those with multiple or separated ones. This work proposed a passive non-interference scheme for synchronously measuring multiple parameters, such as rotation speed, diametral deviation, and diametral vibration, by fully using vibrational characteristics of a magnet-integrated piezo-cantilever excited by rotational magnetic-coupling. Firstly, the measurement of rotation speed is achieved with high linearity, high accuracy, and broad range. Secondly, the measurement of diametral deviation features non-contact compared to mechanical or electromagnetic ones, and is light-free compared to optical methods. Thirdly, the measurement of diametral vibration is discretely realized by creatively considering physical magnetic-coupling as an equivalent to digital signal-sampling, which is fundamentally different from previous ones, and extendable to other physical coupling. The proposed scheme is experimentally demonstrated its effectiveness and feasibility with a typical rotary disk, and is theoretically analyzed by the interaction between rotating magnets, the electro-mechanical response of the piezo-cantilever, as well as the coupling-based sampling model. The proposed scheme is believed to have a widespread application, from precision measuring of rotary systems to health monitoring of manufacturing centers, with further fulfilling its potential like structure miniaturization and higher adaptivity.

Rotational‐speed measurement in harsh environments is an important topic. However, the high rotation results in rapid frequency variations in the signals of a sensor and changes in physical properties under extreme thermal circumstances cause significant difficulties in reading signals. To address this problem, we adopt wireless passive measurement methods to design a special characteristic signal circuit module that achieves precise measurement of rotational speed at high temperatures. The sensor and the readout system include a variable frequency source, a readout antenna, and a radio frequency demodulation circuit. Herein, a demodulation detector of the signal conversion circuit is designed and used in the envelope detection module of the single sideband demodulation method. In addition, a conversion circuit test platform for high‐temperature environment sensor signal is developed. From the testing, the output signal demodulation of the sensor was observed under a maximum temperature of 700°C with error less than 0.12%. The new sensor and measurement method do not require physical leads and achieve wireless noncontact accurate measurement of rotational speed at high temperature.

Condition monitoring of machines working under non-stationary operations is one of the most challenging problems in maintenance. A wind turbine is an example of such class of machines. One of effective approaches may be to identify operating conditions and investigate their influence on used diagnostic features. Commonly used methods based on measurement of electric current, rotational speed, power and other process variables require additional equipment (sensors, acquisition cards) and software. It is proposed to use advanced signal processing techniques for instantaneous shaft speed recovery from a vibration signal. It may be used instead of extra channels or in parallel as signal verification.

Research on motor rotational speed measurement in regenerative braking system of electric vehicle

The growing number of civil applications in which Unmanned Aerial Vehicles (UAVs) are involved can create many concerns for airspace security and surveillance. Gathering as much information as possible about a drone can be crucial to apply proper countermeasures if a potentially dangerous situation is detected. Of course, the presence of a UAV can be detected by radar, but it is possible to extend the system capabilities to obtain additional information. For example, in the case in which the UAV is equipped with propellers, the radar-measured rotational speed could be important information to classify the type of UAV or to reveal if it is carrying some possibly harmful payload. In addition, the rotational speed measured through radar could be used for different purposes, such as to detect a drone manumission, to estimate its maximum payload, or for predictive maintenance of the drone. Measuring the propellers’ rotational speed with radar systems is a critical task, as the Doppler generated by the rotation can be very high, and it is very difficult to find commercial radar systems in the market able to handle such a high Doppler. Another problem is caused by the typically very small Radar Cross-Section (RCS) of the propellers, which makes their detection even more difficult. In the literature, common detection techniques are based on the measurement of the Doppler effect produced by the propellers to derive their rotational speed, but due to the very limited capabilities of commercial sensors, this approach can be applied only at very low values of the rotational speed. In this work, a different approach based on a Frequency-Modulated Continuous Wave (FMCW) radar is proposed, which exploits the vibration of the UAV generated by the rotation of the propellers. The phenomenon and how the sensor can detect it will be presented, which is joined with a performance analysis comparing different estimation techniques for the indirect measurement of the propellers’ speed to evaluate the potential benefits of the proposed approach.

Accurate and reliable angle and rotational speed measurement is crucial in various industrial and scientific applications. This paper develops a cost-effective, real-time system for angle and rotational speed measurement Using magnetic sensors. The setup comprises a magnetic sensor arranged around a turntable with a DC motor-driven magnet. Sensor signals are amplified and converted to digital via the ADC of an STM controller, with a high-precision timer recording relevant signal intervals. Processed data are framed per the USART protocol for transmission to a host computer. At the software layer, callback functions identify frame headers/tails for data extraction, filter signals via a low-pass filter to reduce noise, and enable real-time angular position display. System accuracy is validated through mathematical fitting to model and calibrate the sensor output-physical angle relationship, ensuring high precision and reliability with a measurement error as low as 0.6 °.