Machine Shaft Research Articles

Synthesis of load moment observerasynchronous electric drive with vector control

Purpose. The energy characteristics of asynchronous electric drives in steady-state operation are functions of three variables: the angular speed rotation of the rotor, the module of the vector flux coupling of the rotor and the moment load. The moment of load is an external disturbing influence, effective methods of its measurement are not available. Therefore, the purpose of this paper is to mathematically describe the observer of the state variables of the active power channel and the load moment on the shaft of an asynchronous electric drive with vector control. Methodology. To achieve the purpose of the work, the method of synthesis modal observers is applied using the field-oriented model of the asynchronous machine with the decomposition of its equations and taking into account the nonlinearities of cross-connections between the control channels. Results. As part of the relay-vector control system, a modal observer of the load moment is synthesized, the information from the output of which can be used to build algorithms for extreme control of an asynchronous electric drive. The asymptotic stability is proved by the method of mathematical modeling and is sufficient the accuracy of the observer of the load moment at different distributions of the roots its characteristic equation. Scientific novelty. Thepaper solves the actual scientific problem of establishing the regularities of the structural-algorithmic synthesis and tuning of the modal observer of the moment of load on the shaft of an asynchronous electric drive. Identification of the moment load on the shaft of an electric machine will allow to improve the quality indicators of extreme control systems of asynchronous electric drives. Practical significance. The obtained equations of the observer determine the load moment identification algorithm, the information about which can be used in two-channel vector control systems for asynchronous electric drives to build an external extreme control circuit, which improves the energy performance of the asynchronous machine. First of all, we are talking about minimizing the loss of active power or the consumption of reactive power an asynchronous machine when the load moment on its shaft changes.

Cutting zone temperature reduction in by using novel nanofluid in SAE1144 machining

CNC Lathe is generally utilized for motor shaft machining. The cost of machining is high as it is machined in CNC machining as well as high cutting speed employed whereas heat generation is more. High cutting zone temperature causes thermal defects in the products. This research focused to create novel nanofluids with the use of waste cooking oil and Molybdenum disulfide Nanoparticles for cutting fluid for machining the SAE 1144 steel shaft. Two independent groups with Taguchi L16 experimental design were employed in this research. This investigation aims to make a shift from CNC-based machining to conventional machining practices without compromising the quality requirements by the reduction of cutting zone temperature with the use of a Novel nanofluid to provide cooling and lubrication at the cutting zone. This study investigates the effect of Molybdenum disulfide Nanoparticles’ concentration on waste cooking oil (Nanofluid) to reduce Cutting zone temperature while machining SAE1144 shaft. The observations were statistically validated. The base fluid is waste cooking oils from the largest sweets and savouries manufacturer as well as a widespread hotel network source. Green machining principles are compared with the findings. The results pass the statistical threshold for validity. That is the proposed clean machining practices reduced the average cutting zone temperature from 271.06 °C (dry/ green machining) to 194.94 °C. A low concentration of 0.1% gives better results at low as well as high cutting speeds. The cutting zone temperature is highly influenced by cutting speed.

Influence of the Compliance of a Technological System on the Machining Accuracy of Low-Stiffness Shafts in the Grinding Process

This paper reports the results of research on the influence of the compliance of the technological system used in grinding low-stiffness shafts on the shape accuracy of the workpieces. The level of accuracy achieved using passive compliance compensation was assessed, and technological assumptions were formulated to further increase the shape accuracy of the low-stiffness shafts obtained in the grinding process. Taking into account the limitations of passive compliance compensation, a method for the active compensation of the compliance of the elastic technological system during the machining process was developed. The experiments showed that the accuracy of grinding was most effectively increased by adjusting the compliance and controlling the bending moments, depending on the position of the cutting force (grinding wheel) along the part. The experimental results were largely consistent with the results of the theoretical study and confirmed the assumptions made. Adjusting the compliance in the proposed way allows for the significant improvement in the accuracy and productivity of machining of low-stiffness shafts.

Analysis of the amplitude of vertical oscillations of the main shaft on a sewing machine

The article provides a mathematical model of the vertical oscillations of the main shaft on the elastic supports of the sewing machine, taking into account inertial forces, as well as the rigidity characteristics of the rubber shaft supports. The regularities of the main shaft designs are experimentally determined for various modes of grinding materials. An effective design scheme of bearing supports with rubber shock absorbers of the main shaft of a sewing machine has been developed and recommended.

Shafts of technological machines with combined supports

This article discusses experimental studies of a saw cylinder (SC) composite shaft with combined support. We proposed a new design of the support that provides a reduction in the shaft. The article considers the influence of changing the parameters of the elastic element of the support of the composite shaft (CS) of the SC using the ANSYS software, calculates and analyzes the reaction forces of the supports for different parameters of the elastic elements, and also considers the effect on the stresses of the system, as well as the results of experimental and comparative tests in production conditions on the SC of the cotton gin machines with a composite bearing, where the parameters of the elastic element differ from each other by different elasticity. The fiberization process took place according to the established technological parameters. The experimental and standard SC models were compared during the experiment.

A Method for Predicting the Boring Topography Error of Shaft Hole on a Thin-Walled Box Based on a Proposed Dynamic Model

Traditional boring dynamic model ignores the effect of the uneven radial stiffness of the shaft hole of the thin-walled box on the boring vibration characteristic, which will lead to the deviation in the prediction for both the cutting force and the surface topography of the machining hole. To address this shortcoming, a new calculation model of the equivalent radial stiffness of the shaft hole is proposed and then validated by the finite element (FE) method. On this basis, a boring dynamic model of the shaft hole is developed, and an experimental study on the dynamic characteristics of the shaft hole boring is carried out to verify the correctness and effectiveness of the proposed dynamic model. Moreover, a prediction method for the surface topography error of the machined shaft hole is presented based on the proposed dynamic model. Finally, the comparison investigation on the hole machined surface topography predicted by the proposed method and measured in practice is carried out. The results show that the proposed theoretical models and method can achieve accurate predictions for both the boring cutting force and the machined surface topography error of the shaft hole on the thin-walled box. This study can provide a theoretical basis for machining error control and process optimization of the fine boring of the thin-walled transmission box.

Influence of misalignment of connection of electrical machine shafts on the nature of electric power of the induction motor

Purpose. To identify the vibration power components caused by misalignment of electrical machine shafts in the instantaneous power of the induction motor. Methodology. The power components of the induction motor are analytically determined taking into account the power caused by torque vibrations on the shaft. Based on this, using the methods of mathematical modelling in the visual programming environment, the known model of a three-phase induction motor with a short-circuited rotor has been made. In addition, elements and connections are introduced which realize the formation of the moment caused by the imbalance of rotating masses. Using Fourier transform of the electric power of the induction motor, we determine its discrete spectrum. Experimental research is conducted on the electric power of the induction motor with a short-circuited rotor, in similar model conditions, on laboratory equipment. With the use of a virtual device synthesized in the LabVIEW package, the wavelet analysis of stator electric power of the motor of laboratory electrotechnical complex is performed. Findings. Differential equations of the induction motor with a short-circuited rotor in abc coordinate system are obtained, which reflect the distribution of instantaneous power in the machine taking into account the vibration moment. As a result of modelling according to the specified equations of the induction machine, in the conditions of full symmetry of parameters of the scheme and the mode with eccentricity of rotating masses, low-frequency vibrations of electric power of a stator with frequency of 25 Hz have been found. Similar results were obtained as a result of wavelet analysis of the electric power of an induction motor of a laboratory electrotechnical complex. Originality. Rationality of use of instantaneous electrical power of induction motor stator for detection of vibration caused by misalignment between its shaft and the shaft of another machine has been substantiated, which allows detecting vibration without complex methods of measuring vibration displacement and its derivatives. Practical value. Detecting vibration by measuring the electrical parameters of the stator circuit of the induction motor and determining the vibrations of its instantaneous power without the use of specialized equipment significantly simplify the procedure of vibration diagnostics at its early stages.

Additively Manufactured Ultralight Shaped-Profile Windings for HF Electrical Machines and Weight-Sensitive Applications

Nowadays, additive manufacturing (AM) is becoming a more feasible solution for scalable electric drives compared to traditional production systems. Also, with the significantly growing automotive sector, innovation in electric machine technology is evolving rapidly. With the unmatched freedom in geometry, AM offers a great deal of flexibility in the design of electrical machine parts. Not only the passive parts can be printed such as the frame and the shaft of the electrical machine, but also active parts, such as windings, can be printed in lightweight materials such as Al–Si–Mg-based alloy. The main focus of this article is to further utilize AM in the design of electrical machine windings, with low weight and low losses especially at high-frequency (HF) operation. Aiming at HF loss reduction, different AM coils are prototyped using different materials, and their performance is compared with traditionally manufactured coils. Moreover, a new design concept of shaped-profile conductors is presented with reduced proximity effect and less impact by the cross-slot leakage flux. This design combines high electromagnetic performance and ultralightweight merits, allowing for higher power density electrical machines.

Failure analysis of an axle shaft in an airport ground support vehicle

In this study, failure analysis of an axle shaft in an airport ground support vehicle was carried out to determine failure mechanism, failure root causes and preventive actions. Macroscopic observation, numerical analysis, metallographic analysis, chemical composition analysis, hardness measurement and tensile test methods were used in failure analysis. In numerical fatigue analyses, axle shaft was modelled as a functionally graded material due to mechanical properties changing in the material radial section as a result of induction surface hardening. The analysis results showed that the failure mechanism of fractured axle shaft was torsional fatigue. High surface roughness and insufficient mechanical properties were found as failure root causes. Making finish cut with low depth and even grinding in surface finishing process were proposed as a prevention to increase surface quality, reduce surface roughness and stress concentrations in machining of axle shaft. In addition, using another material with higher yield strength (EN 37Cr4) was proposed instead of EN 34Cr4 alloy steel as the axle shaft material.

An investigation of oil leakage from automotive driveshaft radial lip seals

There is an ever-increasing stringent directive for environmental protection, even for the previously rather negligible lubricant leakage from vehicular drivetrains. Leakage from transmissions and differential units are no longer permitted and can lead to excessive warranty costs. Additionally, the trend in component downsizing, including for sealing systems has indirectly altered the leakage behaviour of transmissions. To guarantee leakage-free operation, it is important to establish standardised methods of manufacturing processes, particularly for surface topography of shafts. The paper investigates the leakage from two different shaft machining processes: corundum and cubic boron nitride (CBN) grinding. The performance of passenger car transmission sealing system is ascertained with the development and use of a novel detailed representative fully instrumented test rig. A test protocol is set up to assess the performance of shafts during break-in period and correlate shaft topographic data with its measured performance. The results show that the measured oil leakage correlates well with the shaft surface skewness whilst no particular trend is observed with Ra, Rz and shaft lead angle values, which form the basis of most current standards used in industry. Overall, it was observed that shafts with negative skewness in their roughness profile produced lesser leakage. A basic analytical predictive method is also developed which corroborates with the measured data.

A new oval shaft, high performance, 2 pole line start synchronous reluctance machine for submersible pump applications

In this paper, a 2 pole, 4 kW, 6 inches diameter line start synchronous reluctance machine (LS-SynRM) as a submersible water pump motor is designed and optimized with a new oval shaft structure. The aim is to improve the machine performance by widening the flux path on the rotor via narrowing down the shaft on the q-axis. This way a wider d-axis flux path is obtained, and accordingly, the d-axis inductance, the saliency ratio Ld∕Lq, and the inductance difference Ld–Lq are increased. First, a set of structural analyses is carried out on a 7-flux barrier rotor in 3 stages: modal, harmonic, and static structural analyses. According to analysis results, the safe limit for the shaft size reduction is determined as 8 mm to avoid excessive deformations and undesired vibrations due to resonance. Later, the machine is optimized using Multi-Objective Differential Evolution (MODE) algorithm with a narrower shaft. The quality of the Pareto front solutions shows that the oval shaft machine is superior to the circular shaft machine in terms of efficiency, motor mass, and torque ripple. The maximum recorded efficiency improvement for the same size LS-SynRM is 4 points and the same size commercial induction machine is around 20 points.

A shield tunneling method for enlarging the diameter of existing tunnels: Experimental investigations

As for the construction of a metro line, excavated stations usually serve as departure and receiving shafts of the shield tunneling machines, used for drilling of station-to-station tunnels. However, the shield tunneling machines may reach the stations before their excavation. In order to avoid stopping of tunneling to wait for the completion of the station, a Shield Twice Tunneling Method (STTM) is developed and applied to a real engineering example. It permits the station-to-station tunneling machines to pass through the stations first. Subsequently, larger-diameter shield tunneling machines are driven from one end of the station to the other one. The resulting tunnels serve as side-platform stations. A model test, simulating the tunneling process of the larger-diameter shield tunneling machines, was carried out. It was designed according to the concept of equivalent specific energy. The experimental results corroborate the rationality of the selected tunneling machine and of its equipment with cutters. In addition, suitable tunneling parameters are provided. The average values of the thrust forces and the torsional moments are predicted, based on the results of the model test. They agree with the monitored results on site. This demonstrates the usefulness of the model test. Application of the STTM to a real engineering project shows that the entire construction period was reduced by 45%.

Analytical and Numerical Analysis of Injection Pump (Stepped) Shaft Vibrations Using Timoshenko Theory

Abstract The free transverse vibrations of shafts with complex geometry are studied using analytical methods and numerical simulations. A methodology is proposed for evaluating the results of a natural transverse vibration analysis as generated by finite element (FE) models of a shaft with compound geometry. The effectiveness of the suggested approach is tested using an arbitrarily chosen model of the injection pump shaft. The required analytical models of the transverse vibrations of stepped shafts are derived based on the Timoshenko thick beam theory. The separation of variables method is used to find the needed solutions to the free vibrations. The eigenvalue problem is formulated and solved by using the FE representation for the shaft and for each shaft-simplified model. The results for these models are discussed and compared. Additionally, the usefulness of the Myklestad–Prohl (MP) method in the field of preliminary analysis of transverse vibration of complex shaft systems is indicated. It is important to note that the solutions proposed in this paper could be useful for engineers dealing with the dynamics of various types of machine shafts with low values of operating speeds.

Design, Fabrication and Testing of a Direct Drive Electric Powered Hammer Mill Machine

This research designed, fabricated and tested a direct drive electric powered hammer mill machine. A 3 HP electric motor with speed of 1800 rpm was used to power the mill. The fundamentals of machine design, mechanics of machine and basic workshop technology were applied in manufacturing the mill. The calculated design values for maximum centrifugal force of the beaters mounted on the rotor and the maximum machine shaft diameter of the mill are 27 KN and 12 mm respectively. The working principle of the mill is based on repeated combined hammers (beaters) impacts and collisions of the materials being milled with the housing of the milling compartment. Tests were carried out on the mill using dry maize, dry millet, dry stock fish and the combination of dry maize, dry millet and dry stock fish as samples to determine the mill productivity and milling efficiency. In determining the productivity and milling efficiency of the mill, the initial masses of the samples were made equal. The dry stock fish sample produced the highest mill productivity and milling efficiency. The actual mill productivity of 45.05 kg/h and milling efficiency of 91.12 % were obtained by averaging the mill productivities and milling efficiencies obtained when the samples were tested. From the calculated values of the actual mill productivity and milling efficiency, the mill performance is satisfactory.

ROTOR SPEED OBSERVER OF ASYNCHRONOUS GATE CASCADE

The vector control system of an asynchronous motor, which is closed in terms of the rotor speed, assumes the presence of a sensor on the shaft of the electric machine. However, in practice, often there are problems of regulating the speed of rotation of asynchronous electric drives, in the solution of which the use of mechanical movement coordinate sensors is technically irrational or impossible. In this case, it is necessary to use one of the sensorless vector control algorithms, which involve direct measurement of only electrical quantities. In rotor vector control systems, when the stator is connected to the network at the same time, the need to measure the angle of rotation of the rotor relative to the stator is added, which complicates the structure of the observer.
 For the synthesis of speed observers in asynchronous electric drives, the approach known in control theory is widely used, in which, based on the second Lyapunov method, an adaptation function is formed that provides asymptotic convergence of the adaptive model to the reference one.
 In this paper, the synthesis of the rotor speed observer of an asynchronous gate cascade (AGC) was carried out for its application in a sensorless relay-vector control system. Equations of electromagnetic processes in an asynchronous machine, formulas for coordinate transformations and an identifier for the position angle of the rotor AGC were used as initial mathematical models. The observer synthesis is based on the second Lyapunov method, which allows to determine the structure of the adaptation function, which adjusts the adaptive model in such a way that the difference between the outputs of the adaptive and reference models tends to zero. Thus, the adaptation function, which uses the stator flux vector, ensures the asymptotic stability of the perturbed motion. The proposed speed observer AGC differs from the known observers for stator control in that, along with the speed calculation, the trigonometric functions of the rotor rotation angle are determined, and the structure of the observer includes coordinate transducers that are absent in stator vector control systems, since they do not need to calculate the projections of the voltage vector of one part of the machine onto the orthogonal axes of its other part.

Development of a fatigue strength testing machine

A profound engineering design and modeling of fatigue strength machine for testing the failure which occurs when a metallic material is subjected to cyclic stresses is presented. The main goal is developing a locally made fatigue strength machine that can be used in material science laboratory. A major direction in this development of the machine is the ability to thread on the path of technology transfer and dominance by concentrating on the building of indigenous capacity. In carrying out the machine development, engineering design formulae were applied and Computer Aided Design modeling was developed. The developed fatigue strength testing machine had a designed machine capacity of 18875Nmm that sustained a motor power of 5.93kw.The machine shaft diameter determined to be 9.88mm developed an equivalent torque and bending moment of 45799.8Nmm and 40890Nmm respectively. The machine designed critical speed of 23.52rad/s had belt tensions on the tight and slack sides to be 139.02N and 44.65N respectively. The fabricated machine has the ability to record low and high fatigue cycles.

ENGINEERING PRACTICE OF SETTING A FIELD ORIENTED CONTROL SYSTEM FOR INDUCTION ELECTRIC DRIVE OF PIPELINE VALVES BASED ON EQUIVALENT CIRCUIT PARAMETERS, ESTIMATED BY FALLING PHASE CURRENT CURVE

To support modern requirements for an induction electric drive of pipeline valves, the most promising is the organization of a filed oriented control system, the setting of which is extremely difficult without the parameters of the equivalent circuit of an induction machine. This article provides a technique of setting a field oriented control system for induction electric drive of pipeline valves based on equivalent circuit parameters, estimated by falling phase current curve. The main aim of the research is to test the functioning of an induction filed oriented electric drive using a load stand, the setting of which is made on the basis of parameters previously estimated by falling phase current curve. Methods. To achieve the goal of the research, theoretical and experimental research methods were used. Theoretical research methods include the theory of electric drive, the theory of automatic control systems, the theory of electrical machines. Experimental research were carried out using a load stand that provides the required level of load on the shaft of the tested induction machine. Results. Suggested the technique of setting a field oriented control system for induction electric drive of pipeline valves based on equivalent circuit parameters, estimated by falling phase current curve. Relative values of deviations of current, speed and torque are obtained at the nominal level of load on the shaft of an induction machine. The applicability of the proposed technique using a loading stand was confirmed.

TECHNIQUE OF SETTING UP A PIPELINE VALVE ELECTRIC ACTUATORS CONTROL SYSTEM USING THE EQUIVALENT CIRCUIT PARAMETERS, ESTIMATED BY FALLING CURRENT CURVE

To support modern requirements for an induction electric drive of pipeline valves, the most promising is the organization of a filed oriented control system, the setting of which is extremely difficult without the parameters of the equivalent circuit of an induction machine. This article provides a technique of setting a field oriented control system for induction electric drive of pipeline valves based on equivalent circuit parameters, estimated by falling phase current curve. The main aim of the research is to test the functioning of an induction filed oriented electric drive using a load stand, the setting of which is made on the basis of parameters previously estimated by falling phase current curve. Methods. To achieve the goal of the research, theoretical and experimental research methods were used. Theoretical research methods include the theory of electric drive, the theory of automatic control systems, the theory of electrical machines. Experimental research were carried out using a load stand that provides the required level of load on the shaft of the tested induction machine. Results. Suggested the technique of setting a field oriented control system for induction electric drive of pipeline valves based on equivalent circuit parameters, estimated by falling phase current curve. Relative values of deviations of current, speed and torque are obtained at the nominal level of load on the shaft of an induction machine. The applicability of the proposed technique using a loading stand was confirmed.

Collaborative robot UR10 integration with CNC lathe Haas ST10

The article describes the process of integrating a UR10 collaborative robot with a Haas ST10 CNC lathe. The integration has been implemented in order to operate the lathe in the technological process of shaft machining. The control systems for both devices were integrated using the digital input and output method. Correctness tests of the programmed machining cycle were carried out.

Novel Characterization of Si- and SiC-Based PWM Inverter Bearing Currents Using Probability Density Functions

The high frequency PWM voltage pulses from a two-level six-switch inverter produce a common-mode voltage in an electric machine’s windings, a fraction of which appears on the machine shaft due to electrostatic (capacitive) coupling. When the shaft voltage exceeds the dielectric strength of the bearing lubricating grease, electric discharge machining (EDM) electrostatic discharges occur within the bearing, which can lead to premature failure. According to pulsed dielectric theory, the breakdown voltage across a dielectric increases with an increase in voltage slew rate (dv/dt). Therefore, the faster voltage rise times of wide bandgap devices are expected to produce higher magnitude shaft voltages and EDM bearing currents. This paper presents circuit modeling of EDM currents and compares the shaft voltage and bearing current amplitudes of silicon- and silicon carbide-based PWM inverters through experimental measurements and a statistical analysis using probability density functions. The statistical analysis provides insights regarding the correlation between bearing failure and the number of damage causing discharges over time which is a key step in developing bearing lifetime prediction models.