Academic literature on the topic 'Sensorless control system'

The main aim of this project was to research, develop and test an induction motor drive not requiring a speed encoder, but which could be considered commercially viable by motor drives manufacturers, and which should aim to meet the follow requirements: • Dynamic torque performance and steady state speed-holding accuracy to be comparable with encodered vector controlled drives • Extensive and highly accurate knowledge of electrical and mechanical parameters of the motor and load not to be required • Extensive commissioning from an expert engineer not to be necessary • Algorithm not to rely on excessive computational capability being available The drive was to operate, in a stable manner, over speed and load ranges at least comparable with commercially available sensorless induction motor drives. The above requirements were set such that the developed sensorless technique may be considered for synchronised multi-motor process applications, where the advantages of a sensorless system could be exploited for hazardous, damp and hot conditions. The solution developed consists of a leading model-based sensorless method augmented with a speed estimator that tracks harmonics, seen in the stator terminal quantities, due to rotor slotting. The model-based scheme facilitates field-orientated control for dynamic performance. The slot harmonic speed estimator tunes the model for speed accuracy. Slot harmonics are identified using a recursive signal processing method termed the Recursive Maximum Likelihood - Adaptive Tracking Filter. This work is the first example of the method being developed into a practical sensorless drive system and the complete speed identifier is described, including set-up, pre-filtering and the minimal parameter considerations. Being recursive the method is computationally efficient, yet has accuracy comparable with that of FFT identifiers used in other work. The developed sensorless strategy was implemented practically on two motor drive systems. The performance of the scheme is shown to give encoder like speed holding accuracy and field-orientated dynamic performance. The two drives were also configured and tested as a speed synchronised pair, using applicable multi-motor control techniques, themselves compared and contrasted. The sensorless performance is demonstrated, alongside an encodered version acting as a benchmark, and the performance of the two schemes is shown to be highly comparable. The author has found no other example of sensorless techniques considered for use in multi-motor applications. The use of such a technique brings established advantages associated with encoder removal and allows multi-axis electronic synchronisation to be considered for parts of a process where an encoder may not be appropriate.

Fuel cells have the potential to provide clean power for a variety of uses including stand-alone residential power. But to increase the acceptance of fuel cells for off-grid generation, the cost of the energy management system must be greatly reduced. Of the many ways to accomplish this, this paper looks at reducing cost through topology changes and elimination of current sensors. A dual 2.5kW non-isolated bidirectional boost converter is designed and analyzed. The various bidirectional boost topologies are compared on cost and ability to meet the specifications. A sensorless average current mode is designed, implemented and verified through testing in a low-cost fixed-point DSP. Both boost and buck modes are accurately modeled and voltage and current controllers are designed for good closed-loop response. The accuracy of the sensorless average current measurement is investigated in both modes of operation. A classical dual-loop controller is implemented in boost mode with the sensorless average current and in buck mode, a dual controller operating in either current or voltage mode is implemented. The design is verified through testing in boost and buck mode and it is shown that the results are acceptable.<br>Master of Science

The structure of a permanent magnet generator (PMG) connected with an active front-end rectifier is very popular in the AC-DC architecture. Especially for certain applications like aircraft and vehicles, power density and efficiency is critical. Since the generator and the rectifier can be controlled simultaneously, it would be very desirable to develop a unified control. With this unified control, the boost inductors between the PMG and rectifier is eliminated, which significantly reduce the volume and the weight of the whole system and improve the system power density. Also the system efficiency can be improved with appropriate control strategy. In this thesis, a unified control for the permanent magnet generator and rectifier system is presented. Firstly, the unified model of the PMG and rectifier system is given as the basis to design the control system. Secondly, a unified control method for PMG and rectifier system is introduced. The design procedure for each control loops are presented in detail, including current control loop, voltage control loop, reactive control loop and speed and rotor position estimator loop. Thirdly, the hardware is developed and the experiment is conducted to verify the control strategy. Fourthly, a method to optimize the overall system efficiency by appropriate reactive power distribution is proposed. The two cases when the DC link voltage is flexible and the DC link voltage is fixed are considered.<br>Master of Science

Transportation of liquids and gasses in industries in forms of pumping and fanning, constitutes asignificant part of the world-wide electric energy consumption. In order to meet global environmentalgoals of greenhouse gas emissions and sustainable material usage, the development of efficiency andtechnical lifetime of industrial pump and fan technology, are key. Innovative designs of electricmotors, motor control and electronics have improved the energy efficiency and technical lifetime ofresidual and wastewater pumps technologies. Mid-sized wastewater submersible pumps are oftenused in hazardous environments, where the pumped medium consists of a mixture of water, sludgeand solids. Solids in wastewater such as textiles are prone to get stuck in the impeller of the pump,thereby halting the motion, lower the efficiency or completely locking the rotor. An aspect ofimportance is henceforth the pump’s ability to provide full torque at low or start-up speed toovercome the blockade of the solids. “Xylem Water Solutions” most modern and advanced wastewater pump consists of a permanent magnet synchronous motor (PMSM) for obtaining a vastincrease of efficiency compared to induction motors traditionally used in wastewater pumpingapplications. Also, PMSM’s can provide full torque at zero speed. PMSM’s are commonly controlledby position-sensorless means. However, obtaining full torque at low- or zero speed is for sensorlessPMSM control extremely challenging.The thesis project examines sensor-based PMSM control and compares this to conventionalsensorless strategies. This was done both by building and analysing a simulated model inSIMULINK/MATLAB of both a sensor-based and sensorless drive system. Secondly, a laboratorytest system was implemented with a motor drive platform with programmable motor controlalgorithms. This was done partially to grasp the knowledge of implementation and design of motorcontrol, and partially to enable tests and comparisons between different motor control strategies in amotor brake bench test rig located at the lab of Xylem Water Solutions Sundbyberg.The implementation of the motor control platform lab system was successfully implemented and ranwith the vendors pre-configured sensorless control. An own interrupt-driven sensor-based cascadedmotor control algorithm was designed in SIMULINK where all suggestions of design andimplementation are outlined in the report. However, during an early step of the test procedure ofthe pre-programmed sensorless control code, the hardware equipment malfunctioned and caused abreakdown of the current-sensors of the controlled inverter. This led to disabled test equipment andleft the own-written code unverified at the time of the project’s end.The results from the simulation resulted in a successfully implemented SCVM model and a sensorbasedmotor control model. The sensored model was implemented by assuming synchronization atany given moment, whereas the SCVM finds the position angle by estimating the back-EMF of themotor. The simulated sensored and SCVM controls performs well for the targeted system application.Parametric study of the SCVM model suggests that both the stator winding resistance and thesynchronous inductance should be underestimated for guaranteed synchronization at start-up.<br>Förflyttning av vätskor och gaser med hjälp av pumpar och fläktar i industustriella applikationerstår för en signifikant del av den globala konsumtionen av elektrisk energi. För att möta miljömålmed avseende på utsläpp av växthusgaser och hållbar användning av naturresurser är effektiviseringoch ökad teknisk livslängd inom industriell pump- och fläktteknologi viktigt. Förbättrad design avelektriska motorer, motorstyrning och elektronik har ökat energieffektiviteten och den tekniskalivslängden för avloppsvattenpumpar. Medelstora nedsänkta avloppspumpar används ofta iutmanande miljöer, där det pumpade mediet består av en blandning av vatten, slam och fastmaterial. Fasta material såsom textilier i avloppsvatten riskerar att orsaka problem för pumpargenom att fastna i impellern och därmed göra pumprörelsen ojämn, sänka verkningsgraden ellertotalt låsa rotorn. Därför är en viktig egenskap hos en högpresterande och pålitlig pump dessförmåga att leverera fullt vridmoment vid uppstart och vid låga hastigheter, för att kunna hanteramaterial som fastnat. “Xylem Water Solutions” modernaste och mest avanceradeavloppsvattenpump har en synkron permanentmagnetmotor (PMSM) vilket ger en betydandeeffektivitetsökning jämfört med traditionella induktionsmotorer. Dessutom kanpermanentmagnetmotorer ge fullt vridmoment vid noll hastigheten. PMSM:er styrs vanligen utanpositionsgivare. Dock är det extremt utmanande att uppnå fullt vridmoment vid låg eller nollhastighet för givarlös PMSM-styrning.Avhandlingens projekt undersöker givarbaserad PMSM-styrning och jämför detta medkonventionella givarlösa strategier. Detta utfördes för det första genom att konstruera och analyseraen simuleringsmodell i SIMULINK/MATLAB för både en givarbasera och en givarlös drivlina. Fördet andra implementerades ett testsystem i laboratorium bestående av en drivlina framtagen förprogrammeringsbar motorstyrning. Projektet genomfördes dels för att bygga kunskap om designoch implementering av motorstyrning, dels för att möjliggöra tester och jämförelser mellan olikastrategier för motorstyrning i en befintlig testbänk för motorbromsning i Xylem Water Solutionslaboratorium i Sundbyberg.Implementering av motorstyrningsplattformen och drivlinan genomfördes framgångsrikt ochkördes med leverantörens förkonfigurerade styrning av givarlös typ. En egen givarbaserad algoritmför motorstyrning designades i SIMULINK. Alla förslag rörande design och implementering avdenna algoritm summeras i rapporten. Under ett av de tidiga stegen i testproceduren för denförprogrammerade koden för givarlös styrning fallerade dock hårdvaran och orsakade attströmgivarna i den styrda växelriktaren havererade. Detta ledde till inaktiverad testutrustning ochlämnade den egenskrivna programkoden overifierad vid tiden för projektets avslutning.Resultaten från simuleringen gav en framgångsrikt implementerad SCVM (Statiskt kompenseradspänningsmodell) och en givarbaserad modell för motorstyrning. Den givarbaserade modellenrealiserades genom att anta synkronisering vid varje givet tillfälle, medan SCVM-modellenbestämmer positionsvinkeln genom att estimera motorns back-EMF. De simuleradestyrmodellerna, den givarbaserade och SCVM, fungerar båda väl för målapplikationen.Parameterstudier av SCVM-modellen tyder på att både statorns lindningsresistans och densynkrona induktansen ska estimeras i underkant för att garantera synkronisering vid uppstart.

The use of brushless motors has increased in recent years due to superior performance characteristics compared with alternatives. The operation of a brushless motor is dependent upon a separate controller which is often in the form of a printed circuit board. As such, the size and performance capability of the controller can restrict the performance of the overall motor control system so advancements of these controllers further the potential use of BLDC motors. This project outlines the design of a PCB based, sensorless motor controller for operation of a three-phase BLDC motor powered by a 24 V, high current external supply. Components used were selected to withstand an ambient temperature environment of 125 degrees C. The design for this PCB based motor control system was completed but fabrication and testing of the system was prevented by COVID-19 related restrictions that prohibited the use of necessary facilities and equipment. The detailed design including component selection, board layout, and software development is included in addition to a plan for fabrication and fundamental functional testing. Although no results are available for analysis to bring about any conclusions, a variety of design strategies and corresponding learnings hold the potential to be a source of valuable reference to the further study and development of future designs.

ABSTRACT SENSORLESS DIRECT FIELD ORIENTED CONTROL OF INDUCTION MACHINE BY FLUX AND SPEED ESTIMATORS USING MODEL REFERENCE ADAPTIVE SYSTEM This work focuses on an observer design which will estimate flux-linkage and speed for induction motors in its entire speed control range. The theoretical base of the algorithm is explained in detail and its both open-loop, and closed-loop performance is tested with experiments, measuring only stator current and voltage. Theoretically, the field-oriented control for the induction motor drive can be mainly categorized into two types<br>indirect and direct field oriented. The field to be oriented may be rotor, stator, or airgap flux-linkage. In the indirect field-oriented control, the slip estimation based on the measured or estimated rotor speed is required in order to compute the synchronous speed. There is no need for the flux estimation in such a system. For the direct field oriented case the synchronous speed is computed with the aid of a flux estimator. In DFO, the synchronous speed is iv computed from the ratio of dq-axes fluxes. With the combination of a flux estimator and an open-loop speed estimator one can observe stator-rotor fluxes, rotor-flux angle and rotor speed. In this study, the direct (rotor) flux oriented control system with flux and-open-loop speed estimators is described and tested in real-time with the Evaluation Module named TMS320LF21407 and the Embedded Target software named Vissim from Visual Solutions Company.

Induction motor driven mechanical transmission systems are widely utilised in many applications across numerous sectors including industry, power generation and transportation. They are however subject to common failure modes primarily associated with faults in the driven mechanical components. Notably, gearboxes, couplings and bearings can cause significant defects in both the electrical and mechanical systems. Condition monitoring (CM) undertakes a key role in the detection of potential defects in the early development stages and in turn avoiding catastrophic operational and financial consequences caused by unplanned breakdowns. Meanwhile, variable speed drives (VSDs) have been increasingly deployed in recent years to achieve accurate speed control and higher operational efficiency. Among the different speed control designs, sensorless VSDs deliver improved dynamic performance and obviate speed measurement devices. This solution however results in heightened noise levels and continual changes in the power supply parameters that potentially impede the detection of minute fault features. This study addresses the gap identified through a systematic review of the literature on the monitoring of mechanical systems utilise induction motors (IM) with sensorless VSDs. Specifically, existing techniques prove ineffective for common mechanical faults that develop in gearboxes and friction induced scenarios. The primary aim of this research centres on the development of a more effective and accurate diagnostic solution for VSD systems using the data available in a VSD. An experimental research approach is based to model and simulate VSD systems under different fault conditions and gather in-depth data on changes in electrical supply parameters: current, voltage and power. Corresponding techniques including model based methods and dynamic signature analysis methods were developed for extracting the changes from noise measurements. An observer based detection technique is developed based on speed and flux observers that are deployed to generate power residuals. Both static and dynamic techniques are incorporated for the first time in order to detect the mechanical misalignment and lubrication degradation, each with different degrees of severities. The results of this study demonstrate that observer based approaches utilising power residual signalling can be effective in the identification of different faults in the monitoring of sensorless VSD driven mechanical systems. Specifically, the combination between dynamic and static components of the power supply parameters and control data has proved effective in separating the four types of common faults: shaft misalignment, lubricant shortage, viscosity changes and water contamination. The static data based approach outperforms the dynamic data based approach in detecting shaft misalignments under sensorless operating modes. The dynamic components of power signals, however, records superior results in the detection of different oil degradation problems. Nevertheless, static components of torque related variables, power and voltage can be used jointly in separating the three tested lubricant faults.

Thesis (MScEng)--Stellenbosch University, 2013.<br>Wind energy has proven to be a viable source of clean energy, and the worldwide demand is growing rapidly. Variable speed topologies, with synchronous generators and full-scale converters, are becoming more popular, and the e ective control of these systems is a current trend in wind energy research. The purpose of this study is the modelling, design, simulation and implementation of a small-scale, variable speed wind energy conversion system, incorporating the position sensorless direct torque control with space vector modulation, of a permanent magnet synchronous generator, including an RLC converter lter. Another aim is the development of a gain scheduling algorithm that facilitates the high level control of the system. Mathematical models of the combined lter-generator model, in the stationary and rotating reference frames, are presented and discussed, from which equivalent approximate transfer functions are derived for the design of the controller gains. The design of the controller gains, RLC lter components, gain scheduling concept and maximum power point tracking controller are presented. It is discovered that the RLC lter damping resistance has a signi cant e ect on the resonance frequency of the system. The system is simulated dynamically in both Simulink and the VHDL-AMS programming language. Additionally, the maximum power point tracking controller is simulated in the VHDL-AMS simulation, including a wind turbine simulator. The simulation results demonstrate good dynamic performance, as well as the variable speed operation of the system. The practical results of torque and speed controllers show satisfactory performance, and correlate well with simulated results. The detailed gain scheduling algorithm is presented and discussed. A nal test of the complete system yields satisfactory practical results, and con rms that the objectives of this thesis have been reached.