FPGA-based adaptive backstepping control system using RBFN for linear induction motor drive

A field-programmable gate array (FPGA)-based adaptive backstepping control system with radial basis function network (RBFN) observer is proposed to control the mover position of a linear induction motor (LIM). First, the indirect field-oriented mechanism is adopted for controlling the LIM. Next, a backstepping control law is designed step by step for the tracking control of periodic reference trajectories, in which the uncertainties are lumped by a conservative constant. However, the lumped uncertainty is unknown and difficult to obtain in advance in practical applications. Therefore an RBFN is derived to observe the lumped uncertainty in realtime, and an adaptive backstepping control system with RBFN observer is resulted. Then, an FPGA chip is adopted to implement the indirect field-oriented mechanism and the developed control algorithms for possible low-cost, high-performance industrial applications. The effectiveness of the proposed control scheme is verified by some simulated and experimental results. By using the adaptive backstepping control system with RBFN observer, the FPGA-based LIM drive possesses the advantages of good transient control performance and robustness to uncertainties in the tracking of periodic reference trajectories.     

Analytical closed-form investigation of pwm inverter induction motor drive performance under dc bus voltage pulsation

The voltage unbalance conditions at the input rectifier stage of the AC?DC?AC rectifier-inverter fed induction motor drive is analysed. This unbalance can cause significant voltage harmonic of twice the line frequency 2f1 in the DC bus. This voltage ripple can have a degrading effect on the induction-machine performance characteristics. The authors present an analytical closed-form mathematical model and analysis of the impact of DC bus ripple voltage of the three-phase voltage source inverter with the space-vector PWM on the induction machine phase voltages, currents and torque pulsations. The analytical expressions for the voltage and current space vectors as a function of the DC bus voltage pulsation are derived. Using superposition, the separate parts of the motor currents can be determined. From the current space vectors, the torque behaviour is estimated, again as a function of DC link voltage pulsation. Next, it is shown that the DC link voltage ripple components may cause large torque pulsation. The proposed analytical method is based on the mixed p?z approach, enabling presentation of the results in lucid and closed form. To verify the effectiveness of the proposed analytical model, experimental results based on laboratory setup were obtained.     

Modelling and analysis of an open-loop induction motor drive incorporating the effect of inverter dead-time

The objective of this paper is to study the influence of inverter dead-time on steady as well as dynamic operation of an open-loop induction motor drive fed from a voltage source inverter (VSI). Towards this goal, this paper presents a systematic derivation of a dynamic model for an inverter-fed induction motor, incorporating the effect of inverter dead-time, in the synchronously revolving dq reference frame. Simulation results based on this dynamic model bring out the impact of inverter dead-time on both the transient response and steady-state operation of the motor drive. For the purpose of steady-state analysis, the dynamic model of the motor drive is used to derive a steady-state model, which is found to be non-linear. The steady-state model shows that the impact of dead-time can be seen as an additional resistance in the stator circuit, whose value depends on the stator current. Towards precise evaluation of this dead-time equivalent resistance, an analytical expression is proposed for the same in terms of inverter dead-time, switching frequency, modulation index and load impedance. The notion of dead-time equivalent resistance is shown to simplify the solution of the non-linear steady-state model. The analytically evaluated steady-state solutions are validated through numerical simulations and experiments.     

Three-phase soft-switched pwm inverter for motor drive application

A novel soft-switched inverter topology in which three mutually coupled inductors at a time are involved in the resonance process is proposed. By the introduction of magnetic coupling between three resonant inductors, the zero-voltage instants for the inverter can be generated by one auxiliary switch. Also, the resonant energy can be recycled, and the maximum voltage stress on the auxiliary circuit diode components is confined to the DC-link clamp voltage level. The DC link can be clamped to 1.1-1.3 times the DC-source value. This is unlike the soft-switched inverter in which two mutually coupled inductors are at a time are involved in a resonance process, wherein the clamping diode experiences voltage stress of the order of 11 per unit when clamping the DC-link voltage at 1.1 per unit. The proposed inverter also provides pulse-width modulated operation. An analysis of this novel quasi-resonant DC-link inverter topology is presented to reveal its soft-switching characteristics. Simulation and laboratory experiments are performed to validate the analysis.     

Single-current-sensor-based active front-end-converter-fed four quadrants induction motor drive

Induction motor (IM) is a workhorse of the industry, whose dynamics can be modified close to that of a separately excited DC machine by field-oriented control technique, which is commonly known as vector control of induction machine. This paper presents a complete performance of the field-oriented control of IM drive in all four quadrants with a single-current-sensor-based active front end converter whose work is to regulate DC link voltage, draw pure sinusoidal currents at unity power factor and to facilitate bi-directional power flow between the grid and the drive. The entire system is completely modelled in MATLAB/SIMULINK and the results are discussed in detail. The vector control analogy of the back to back converters is highlighted along with the experimental results of field-oriented control of induction machine using a dsPIC30F6010A digital signal controller.     

Design and implementation of an industrial vector-controlled induction motor drive

Vector-controlled induction motor drives are quite popular in the industry in applications that demand high dynamic performance. This paper describes the implementation of a complete industrial vector-controlled drive for a 30 kW induction motor. The control algorithms for the drive are implemented using a TMS320F28335 Digital Signal Controller (DSC). Various monitoring and protection functions for the drive are implemented using a Cyclone IV FPGA that communicates with the DSC, and acts as the master controller for the drive. The FPGA also communicates with a Human–Machine Interface to provide a simple graphical control interface to the operator.     

Minimization and identification of conducted emission bearing current in variable speed induction motor drives using PWM inverter

The recent increase in the use of speed control of ac induction motor for variable speed drive using pulse width modulation (PWM) inverter is due to the advent of modern power electronic devices and introduction of microprocessors. There are many advantages of using ac induction motor for speed control applications in process and aerospace industries, but due to fast switching of the modern power electronic devices, the parasitic coupling produces undesirable effects. The undesirable effects include radiated and conducted electromagnetic interference (EMI) which adversely affect nearby computers, electronic/electrical instruments and give rise to the flow of bearing current in the induction motor. Due to the flow of bearing current in the induction motor, electrical discharge machining takes place in the inner race of the bearing which reduces the life of the bearing. In high power converters and inverters, the conducted and radiated emissions become a major concern. In this paper, identification of bearing current due to conducted emission, the measurement of bearing current in a modified induction motor and to minimize the bearing current are discussed. The standard current probe, the standard line impedance stabilization network (LISN)), the electronics interface circuits are used to measure high frequency common mode current, bearing current and to minimize the conducted noise from the system. The LISN will prevent the EMI noise entering the system from the supply source by conductive methods, at the same time prevents the EMI generated if any due to PWM, fast switching in the system, will not be allowed to enter the supply line. For comparing the results with Federal Communications Commission (FCC) and Special Committee on Radio Interference (CISPR) standards, the graphs are plotted with frequency Vs, line voltage in dBμ V, common mode voltage in dBμ V and the bearing current in dBμ A with out and with minimizing circuits.     

Experimental determination of mechanical parameters in sensorless vector-controlled induction motor drive

High-performance industrial drives widely employ induction motors with position sensorless vector control (SLVC). The state-of-the-art SLVC is first reviewed in this paper. An improved design procedure for current and flux controllers is proposed for SLVC drives when the inverter delay is significant. The speed controller design in such a drive is highly sensitive to the mechanical parameters of the induction motor. These mechanical parameters change with the load coupled. This paper proposes a method to experimentally determine the moment of inertia and mechanical time constant of the induction motor drive along with the load driven. The proposed method is based on acceleration and deceleration of the motor under constant torque, which is achieved using a sensorless vector-controlled drive itself. Experimental results from a 5-hp induction motor drive are presented.     

A nine-level hybrid symmetric cascaded multilevel converter for induction motor drive

A nine-level hybrid symmetric cascaded multilevel converter (MLC) fed induction motor drive is proposed in this paper. The proposed converter is capable of producing nine output voltage levels by using the same number of power cells as that of conventional five-level symmetric cascaded H-bridge converter. Each phase in this configuration consists of one five-level transistor-clamped H-Bridge (TCHB) power cell and one three-level H-bridge power cell with equal dc link voltages, and they are connected in cascade. Due to cascade connection and equal dc link voltage, the power shared by each power cell is nearly equal. Near-equal power sharing enables the feature of improving input current quality by using an appropriate phase-shifting multi-winding transformer at the converter input. In this paper, the operation of the converter is explained using staircase and hybrid multi-carrier sine PWM techniques. Further, a detailed analysis for the variations in the dc link capacitor voltages and the dc link mid-point voltage in TCHB power cell is carried out, and the analytical expressions thus obtained are presented. The performance of proposed system is analysed by simulating a 500 hp induction motor drive system in MATLAB/Simulink environment. A laboratory prototype is also developed to validate the claims experimentally.     

Eighteen-sided polygonal voltage space-vector-based PWM control for an induction motor drive

An inverter scheme with 18-sided polygonal voltage space-vector structure is proposed for induction motor drive applications. An open-end winding configuration is used for the drive scheme. The motor is fed from one end with a conventional two-level inverter and from the other end with a three-level inverter, realised by cascading two conventional two-level inverters. The inverters are fed with asymmetrical DC-link voltages. A simple linear PWM control scheme up to 18-step mode is proposed, based only on the motor reference phase amplitudes. The proposed scheme gives an increased modulation range with the elimination of the 5th, 7th, 11th and 13th-order harmonics, for the entire modulation range, when compared with any conventional schemes. The absence of low-order harmonics gives nearly sinusoidal currents throughout the modulation range, and makes PWM control of voltage very simple, with low inverter switching frequencies, especially in the extreme modulation range.     

Implementation of feedback-linearization-modelled induction motor drive through an adaptive simplified neuro-fuzzy approach

A simple modified version of neuro-fuzzy controller (NFC) method based on single-input, reduced membership function in conjunction with an intuitive flux–speed decoupled feedback linearization (FBL) approach of induction motor (IM) model is presented in this paper. The proposed NFC with FBL remarkably suppresses the torque and speed ripple and shows improved performance. Further, the modified NFC is tuned by genetic algorithm (GA) approach for optimal performance of FBL-based IM drive. Moreover, the GA searches the optimal parameters of the simplified NFC in order to ensure the global convergence of error. The proposed simplified NFC integrates the concept of fuzzy logic and neural network structure like a conventional NFC, but it has the advantages of simplicity and improved computational efficiency over the conventional NFC as the single input introduced here is an error (speed and torque) instead of two inputs, error and change in error, as in the conventional NFC. This structure makes the proposed NFC robust and simple as compared with conventional NFC and thus, can be easily applied to real-time industry application. The proposed system incorporated with different control methods is also validated with extensive experimental results using DSP2812. The effectiveness of the proposed method using FBL of IM drive is investigated in simulation as well as in experiment with different working modes. It is evident from the comparative results that the system performance is not deteriorated using the proposed simple NFC as compared to the conventional NFC; rather, it shows superior performance over PI-controller-based drive.     

Control of a converter system for an asymmetrical parameter type two-phase induction motor drive operating in motoring and generating modes

The control of a converter system is presented and discussed for an asymmetrical parameter type two-phase induction machine drive that is operating in motoring and generating modes. The proposed system consists of back-to-back voltage source converters. For a machine side, a three-leg voltage source converter provides both unbalanced and balanced two-phase output voltages with a scalar V/F control based on a carrier space vector pulse width modulation (SVPWM) technique. For a front end, a single-phase AC/DC doubled voltage converter with hysteresis current control is used to keep DC-link voltage constant, thus resulting in a bi-directional power flow operation for the motoring and generating modes. A closed-loop design for the DC-link voltage is fully given and also included is a review of carrier-based SVPWM for two-phase three-leg VSI. The proposed drive system was both simulated using MATLAB/SIMULINK and implemented on digital microcontrollers. The comparative performance evaluation of the whole system between balanced and unbalanced two-phase voltages for the machine is given. The simulation and experimental results show that the unbalanced phase voltage offers better performance for the whole system.     

A comparison of spectrum estimation techniques for nonstationary signals in induction motor drive measurements

This paper compares different spectrum estimation techniques applied to nonstationary signals in order to determine which is the most suitable in analyzing the spectral harmonic content of signals in a very close frequency band. The comparison examines a specific application in which spectral analysis is applied to nonstationary signals, such as currents or voltages in induction motor drives. A test signal and some performance parameters are defined. Experimental tests were carried out by applying different spectral analysis algorithms in order to compare their behavior in detecting defined harmonic frequencies. The results show that the chirp-Z transform outperforms other techniques especially when a restricted frequency band has to be analyzed.     

Modelling and predicting of a switched reluctance motor drive using radial basis function network-based adaptive fuzzy system

A novel fuzzy-neural system, which is referred to as a radial basis function network-based adaptive fuzzy system (RBFN-AFS), is presented, to model the switched reluctance machine (SRM) and predict the dynamic performances in an SRM drive system. First, we use an indirect method to measure the phase flux linkage of a 6/4 SRM and then use the co-energy method to calculate phase torque characteristics. Secondly, the RBFNAFS is designed to learn and train the SRM in the knowledge of the electromagnetic characteristics by using the hierarchically self-organising learning algorithm. This modelling scheme does not require any prior information about the SRM system apart from the input and output signals, and has good capability of generalisation and excellent convergent speed. Then, an RBFN-AFS current-dependent inverse flux linkage model and an RBFN-AFS torque model are used to simulate the various transient and steady-state performances of the 6/4 0.55 kW SRM. The simulation and experimental results based on a DSP drive platform are reported to show that the modelling scheme has good estimation performance under different operation conditions of the SRM.     

精密步进谐波系统谐波参数与步进电机匹配问题的研究

 提出了一种高精度的精密步进系统,指出要获得高精度的步进谐波传动系统必须充分考虑谐波传动的啮合性能、加工精度、系统的动态性能和电机的矩频特性及其控制技术的机电性能匹配问题。     

Sensorless permanent-magnet synchronous motor drive using a reduced-order rotor flux observer

A sensorless permanent-magnet synchronous motor (PMSM) drive is developed. A second-order Luenberger observer is used to estimate the position of the rotor flux and hence the rotor speed. The observer is computationally efficient as it has a simple structure and does not involve mechanical parameters. An integral-feedback method is adopted for the estimation of the rotor speed. The inner current loop is realised using a decoupling and diagonal internal model control algorithm. Details of the sensorless control system are given and the feasibility of the proposed method is verified through simulation and experiments. Satisfactory estimation accuracy is obtained even when the drive operates at very low speeds and also during rotor speed reversals.     

Theoretical prediction and experimental verification of light-load instability in a 11-kW open-loop induction motor drive

This paper presents the small-signal stability analysis of an 11-kW open-loop inverter-fed induction motor drive, including the effect of inverter dead-time. The analysis is carried out using an improved small-signal model of the drive that has been reported in literature recently, and is used to demonstrate small-signal instability in a higher-power-level motor. Through small-signal stability analysis, the region of oscillatory behaviour is identified on the voltage versus frequency plane (V–f plane), considering no-load. These predictions using the improved model are also compared against predictions of a standard model of an inverter-fed induction motor including dead-time effect. The oscillatory behaviour of the 11-kW motor drive is also studied through extensive time-domain numerical simulations and actual measurements over wide ranges of operating conditions. Both the simulation and experimental results confirm the validity of the predictions by the improved analytical model. Further, these results establish that the analysis is valid for both sine-triangle pulse-width modulation (PWM) and conventional space vector PWM.     

全数字交流异步电机伺服系统的设计与实现

介绍了基于TMS320LF2407A的交流伺服系统的硬件和软件构成及实现方案，给出了系统的实验结果，矢量控制与其它控制方法的比较结果表明，与其它控制方式相比，转差频率矢量控制具有动态性能好、控制精度高的突出优点，适合于伺服系统的设计．     

An adaptive fuzzy-neural-network controller for ultrasonic motor drive using the LLCC resonant technique

In this study an adaptive fuzzy-neural-network controller (AFNNC) is proposed to control a rotary traveling wave-type ultrasonic motor (USM) drive system. The USM is derived by a newly designed, high frequency, two-phase voltage source inverter using two inductances and two capacitances (LLCC) resonant technique. Then, because the dynamic characteristics of the USM are complicated and the motor parameters are time varying, an AFNNC is proposed to control the rotor position of the USM. In the proposed controller, the USM drive system is identified by a fuzzy-neural-network identifier (FNNI) to provide the sensitivity information of the drive system to an adaptive controller. The backpropagation algorithm is used to train the FNNI on line. Moreover, to guarantee the convergence of identification and tracking errors, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of the FNNI and the optimal learning rate of the adaptive controller. In addition, the effectiveness of the adaptive fuzzy-neural-network (AFNN) controlled USM drive system is demonstrated by some experimental results.     

Space-vector-based PWM switching strategies for a three-level dual-inverter-fed open-end winding induction motor drive and their comparative evaluation

Two space-vector-based pulse-width-modulated (PWM) strategies are proposed for a dual two-level inverter-fed open-end winding induction motor drive. Neither of these PWM strategies require sector identification or lookup tables. These PWM strategies require only instantaneous phase reference voltages. Also, a simple model is suggested to compute the motor phase currents for this drive, and this model is validated through experimentation. The inverter losses are estimated for this drive system with these PWM strategies using an existing thermal model. The simulation studies suggest that one of these two PWM strategies is better than the other, as it causes lower losses in the inverters.