Prof. Dr. Joachim Holtz
Editor-in-Chief
|
Prof. Dr. Joachim Holtz |
Special Section on Hardware Description Languages for Industrial Electronics
- Guest Editorial: Hardware Description Languages for Industrial Electronics
by Javier Uceda
Abstract - The use of Hardware Description Languages (HDLs) is a major issue in current Electronic Systems Design methods. HDLs enable the description of hardware systems at different abstraction levels, from the algorithmic level to the logic gate level, and including information of different types, behavioral or structural. Although HDLs have been mainly used for the design of digital electronic systems, recent developments present extensions of existing languages, such as VHDL or Verilog, for analog designs. Therefore, the Electronic Systems Design area is currently covered by different languages that allows the designers cope with systems complexity, aided by a number of CAD tools that allows an easy interaction between designers and systems.
Industrial electronics, as one of the main areas of electronic systems design, should take advantage of these methods and the use of HDLs. On one hand, the reusability of models and already designed pieces of hardware may reduce the design effort of industrial electronic systems. Another aspect is the prototyping of systems using a previous implementation that can be easily mapped to a final technology. These issues plus the general ones, make Industrial Electronics a potential user of the design technologies based on Hardware Description Languages. This Special Section contains two papers. The main goal has been to introduce this topic in the Transactions on Industrial Electronics by means of a very brief Special Section, with the idea of pushing step by step the use of HDLs in the Industrial Electronics community.- Design Methodologies based on Hardware Description Languages
by Teresa Riesgo, Yago Torroja, E. de la Torre
Abstract - In this paper we are presenting the basic methodology to be used in the design of a digital system, based on the use of Hardware Description Languages (HDLs). The most important stages of the design flow and the CAD tools involved are presented, from the initial specification to the final implementation. The design flow described in the paper is based on a top-down approach, as this is the methodology currently used for most of the digital systems to face the current system complexity. Although all the concepts and methods are feasible for any kind of digital electronic system, Application Specific Integrated Circuits (ASICs) are specially considered as application example along the paper. Besides, most of the examples shown are written in VHDL (VHSIC Hardware Description Language) as it is an IEEE standard and is one of the most commonly used.
- VHDL Modeling and Model Testing for DSP Applications
by J. R. Armstrong, F. G. Gray, Meng-Wei Lin
Abstract - The digital design process has been dramatically altered through the use of hardware description languages (HDLs) and associated synthesis tools. The designer translates the system specification to an HDL description which is processed by the synthesis tool to produce a gate level circuit. This development has had a dramatic beneficial effect on the design of Application Specific Integrated Circuits (ASICs). And because a high percentage of ASIC designs are Digital Signal Processing (DSP) circuits, this new automated design process has had its greatest effect in this area.
Historically, design engineers created designs pictorially; but with the advent of HDLs, the design of hardware has become a software development process in that the majority of the design time is now spent in developing the HDL model. The systems being modeled are large, e.g., HDL models which are translated into 20,000 gate circuits are common. Thus the models themselves are complex and their creation is a labor-intensive process. Model validation also becomes critically important. An incorrect model will result in an incorrect circuit. To check out a model, one develops a test bench, which is a testing framework into which the Model Under Test (MUT) is inserted and driven with sets of test vectors.
In this paper we discuss two DSP applications: 1) infrared search and track (IRST) and 2) synthetic aperture radar (SAR). The IRST sensor generates sequences of two dimensional arrays of integers representing pixels of varying intensity. The IRST system must detect and track targets using a sequence of these two dimensional images. SAR sensors generate sequences of real numbers representing radar returns. The SAR system combines returns to generate a two dimensional image of the area scanned by the radar.
Power Electronics
- A Contactless Electrical Energy Transmission System
by D. A. G. Pedder, A. D. Brown, J. A. Skinner
Abstract - Most mains-operated equipment in use today is connected to the supply via plugs and sockets. These are generally acceptable in benign environments but can be unsafe or have limited life in the presence of moisture. In explosive atmospheres and in under-sea applications special connectors must be used. This paper describes a technique, the Contactless Energy Transfer System (CETS), by which electrical energy may be transmitted, without electrical connection or physical contact, through non-magnetic media of low conductivity. CETS, which has been used to transfer up to 5 kW across a 10 mm gap, employs high-frequency magnetic coupling and enables plug-in power connections to be made in wet or hazardous environmental conditions without the risk of electric shock, short-circuiting or sparking. Energy may be transmitted without the necessity for accurately manufactured "plug and socket" mechanisms and may be transmitted from source to load even when there is relative motion. Load-source voltage matching may be made inherent to the system.
- Application of a Generalized Current Multilevel Cell to Current Source Inverters
by Fernando Antunes, Henrique A. C. Braga, Ivo Barbi
Abstract - In this work a new cell which lends itself as a generic current multilevel one is applied to current source inverters (CSI) with output current harmonics minimization and without the use of high frequency modulation. In this cell, inductors acting as current sources ensure equal current division among switches. DC current balance in the inductors is achieved also without closed-loop control. It is also shown that while for the five level structure it is easy to find proper control strategies, for higher levels it is necessary the use of numerical simulation programs to find out a proper switching strategy. Simulation and experimental results are included to show the performance of the new cell for high power applications.
- Constant-Frequency Sliding-Mode and PI Linear Controllers for Power Rectifiers: A Comparison
by Sónia Ferreira Pinto, J. Fernando Silva
Abstract - Constant frequency sliding mode and linear proportional integral (PI) cascaded controllers (internal current loop and external output voltage control loop) for twelve pulse thyristor rectifiers are designed, using new models and convenient assumptions, and their performances compared. The use of sliding mode control on line commutated power converters, implies the use of fixed frequency sliding mode design, originating steady-state errors. These are eliminated using an higher order switching function, with 4th order Bessel polynomial coefficients, to minimise the response time and to eliminate the overshoot in the reaching mode.
Comparisons are made using simulations (MATLAB/SIMULINK blocks), and experimental results. The sliding mode controller, as well as the PI controllers, need almost the same hardware, and present no steady state errors and no output voltage overshoots. Besides allowing a faster dynamics than the PI controllers, the proposed sliding mode approach provides a new, non linear theoretical frame for solving the control problem of power rectifiers with output filters.- Stepping Motor Driving by Controlled-Energy Discharge
by Luciano E. Chiang, Jaime E. Vadell
Abstract - Stepping motors are indexing devices widely used in microcomputer controlled machines. They have proven to give excellent results in terms of accuracy and repeatability in many industrial applications. The main weakness however, is their relatively low working speeds (when compared to the alternative of servo motors), but this has been changing lately mainly due to better electrical controller and motor designs. Hence today there is a wider interchangeability range with servo motors. This article describes a new electrical driving method for stepping motors based on controlled energy discharge (CED) over the motor windings. This method makes use of the fact that the time response of an LR circuit can be improved by the addition of an adequate capacitance. Experimental tests were performed for evaluation purposes. Results obtained show speeds reaching up to 6.000 rpm and as much as 90% of the low speed torque still available at 1.000 rpm for a commercial type stepping motor.
- Bang Bang Current Control with Predecided Switching Frequency for Switch-Mode Rectifiers
by Manjusha Dawande, G. K. Dubey
Abstract - Active current waveshaping techniques are more advantageous than the passive current waveshaping techniques. The major advantages include close to sinusoidal input current, unity power factor and reduced input/output filter size Broadly, these techniques can be divided into two categories,viz.Hysteresis Cur rent Control (HCC) and Constant Switching Frequency Control (CSFC) techniques. Hysteresis Current Control technique offers simple control fast dynamic response,increased reliability of semiconductor switch due to less current stresses and simple closed loop control. However, it suffers from the disadvantages such as essential precisin current sensing and switching frequency variation with load current and its random pattern. The switching frequency needs to be determined through digital simulation of power circuit of the rectifier. Variation of the frequency has to be studied for a g ien range of load current. Therefore, the switching frequency, unless determined through simulation can not be included as a part of the design. Constant Switching Frequency techniques though overcome variable switching frequency disadvantages of HCC and inone case even eliminates current sensing, they generally require complex control circuits as compared to HCC and hence, they loose the simplicity of control, a major advantage offered by HCC. A novel current control technique which offers a constant switching frequency operation for a given load current is proposed here. The switching frequency varies inversely with the load current but is known and predecided. The technique retains all the advntages of HCC as well as CSF techniques and also eliminates need for current sensing. It does not require a hysteresis window to control the current. The mathematically derived equation gives the ON period and starts falling from the end of ON period to the end of respective switching cycle i.e. OFF period. The switching frequency, f will be inversely proportional to curretn Im. Thus the lowest switching frequency will be observed at rated current. A typical range of load current, (and hence that of Im),can be chosen as 10:1. Then the switching frequency at ne tenth of the rated current will be taken ten times that of the switching frequency chosen at rated current. The range of load current control can be typically assumed as 10:1. Correspondingly, the switching frequency range will be 1:10. In this scheme, the current is made remain around a sinusoidal current reference within a hysteresis band by appropriate choiceof wt1 instead of by actual current measurement using a current sensor as in the conventional scheme. The Performance and feasibilty of the proposed scheme has been evaluated by digital simulation and practical implementation.
- Reducing IGBT Losses in ZCS Series Resonant Converters
by Gregory Ivensky, Sam Ben-Yaakov, Ilya Zeltser, Arkadiy Kats
Abstract - The fundamental operational parameter that controls the losses in series resonant converters was found to be the reflected DC voltage transfer ratio. Losses which are a function of the average current (such as conduction losses of IGBTs and diodes) are independent of the switching frequency. Losses which are associated with the rms current are a function of both the reflected DC voltage ratio and the switching frequency ratio. Universal and normalized graphs, derived in this study, can be conveniently used to assess the expected rms and average current conduction losses under any given operational conditions. The residual switching losses in zero current switching series resonant converters operating in Continuous Current Mode can be reduced by simple current snubbers placed in the commutation circuits. The experimental results of this study confirm the theoretical predictions and demonstrate that the turn on snubbers can reduce switching losses by about 1.5% at a switching frequency of 65kHz.
- Actively-Clamped Zero-Current-Switching Quasi-Resonant Converters using IGBT's
by Bo-Tao Lin, Kam-Wah Siu, Y. S. Lee
Abstract - Conventional zero-current-switching quasi-resonant converters (ZCS-QRC s) suffer from disadvantages of high switch current stress and variable switching frequency. This paper proposes the use of a 'current-clamping circuit' to overcome these disadvantages. By incorporating such a circuit into the family of ZCS-QRC s, a new family of actively-clamped ZCS-QRC s using IGBT s is derived.
These converters feature high (and constant) switching frequency and zero-current turn-off (without increased current stress), which are particularly useful for high-power applications where minority-carrier semiconductor devices (such as IGBT s and BJT s) are used as power switches. The design criteria, simulation, and experimental results are reported.- A New ZVS Semi-Resonant High Power Factor Rectifier with Reduced Conduction Losses
by Alexandre Ferrari de Souza, Ivo Barbi
Abstract - This paper presents a novel single-phase unity power factor rectifier, which features Critical Conduction Mode and Zero Voltage Switching. The reduced conduction losses are achieved by the employment of a single converter, instead of the typical configuration composed of a front end rectifier followed by a boost converter. Theoretical analysis, a design example and experimental results of a 300 W converter with 127 Vrms input voltage and 400 VDC output voltage are presented.
- Stepwise Quadratic State-Space Modeling Technique for Simulation of Power Electronics Circuits
by K. K. Tse, Henry S. H. Chung, S. Y. R. Hui
Abstract - A fast and accurate technique for simulation of power electronics circuits is presented. The methodology is started with using Chebyshev polynomials to derive an adaptive stepwise quadratic state-space model for each piecewise-linear circuit topology. The state-space equation sets are integrated with modified nodal equations. The key feature of this algorithm is that it gives an approximate value of the optimum simulation step size for analysis of each circuit topology in order to achieve a desired accuracy in calculating the state transition matrix of the topology. Moreover, the algorithm hybridizes the advantages of calculating the circuit responses at circuit level and determining switching instants at device level. The switching instants are calculated directly by solving simple quadratic equations. Furthermore, it is unnecessary to have prior knowledge of the circuit operations, such as the topology sequence and duration. The algorithm automatically looks for a valid topology at any time instant. The proposed method is illustrated with the examples of a practical induction heater and a boost dc/dc regulator. The theoretical predictions are verified with the results obtained in experiment and available literature.
Drive Control
- A Dynamic Decoupling Control Scheme for High-Speed Operation of Induction Motors
by Jinhwan Jung, Kwanghee Nam
Abstract - In a high speed operation of a vector controlled induction motor, coupling between d-q current dynamics impairs the characteristics of torque response. The feedforward decoupling scheme does not perform well if there exists an error in the motor parameter estimation. We derive a dynamic decoupling condition when the two additional PI current controllers are used. A great advantage of this dynamic decoupling controller is the robustness to the motor parameter estimation errors. Further, we observe that overmodulation methods lead to the violation of the decoupling condition, thereby yield a poor performance in the high speed, high power operation. As a method of resolving this problem, we propose a decoupling preserving overmodulation (DPO) algorithm which also enhances the torque transient response. Through simulation and experiment results, we demonstrate the improved performances of the proposed controller.
- Automatic IM Parameter Measurement under Sensorless Field-Oriented Control
by Chern-Lin Chen, Yih-Neng Lin
Abstract - A novel approach of automatic induction motor (IM) parameter measurement under sensorless field-oriented control (FOC) is presented. Before start-up, the inverter drive automatically performs the dc test, the no-load test, and the locked-rotor test for the driven IM. The only measured values are input current signals. No additional hardware is required in this approach. In order to automatically measure the IM parameters under FOC structure, the concepts of no-load test and dc test should be modified. In addition, because conventional locked-rotor test requires that the rotor shaft has to be locked mechanically, this makes automatic measurement impossible. In order to solve this problem, a locked-rotor test at single-phase excitation for sensorless FOC structure is also performed in this paper to facilitate automatic IM parameter measurement. Finally, the test data are then computed to get the IM parameters and the field current command for FOC. The presented method has been tested on a 3-hp inverter-driven IM system. Its effectiveness is illustrated by experimental recordings.
- Torque and Speed Regulations of Induction Motors using the Passivity Theory Approach
by Carlo Cecati, Nicola Rotondale
Abstract - This paper deals with the Passivity-based control of induction motors. This non linear control method is considered here mainly from the experimental point of view. Two different configurations have been considered: CR-PWMI with hysteresis controllers and SVM-VSI. Experimental results show that both schemes give precise, fast and robust torque and speed tracking in the full speed range. The CR-PWMI configuration is more attractive due to its better transient response and reduced complexity.
- Real-Time Sliding-Mode Observer and Control of an Induction Motor
by Abdelkrim Benchaib, A. Rachid, E. Audrezet, M. Tadjine
Abstract - This paper deals with the control and observation of an induction motor using sliding mode technique. Our aim is to regulate the speed and the square of the rotor flux magnitude to specified references. Assuming that all the states are measured, sliding surfaces are proposed whithin a sliding mode control framework. Then, the stator voltages are derived such that the sliding surfaces are asymptotically attractive. Since in practice the rotor fluxes are not usually measurable, a sliding mode observer is derived to estimate the rotor fluxes. Furthermore, it is shown that our observer is robust against modeling uncertainties and measurement noise. To illustrate our purpose, we present experimental results for a 0.37 kW induction motor obtained on a digital signal processor (DSP) TMS 320C31/40 MHz based system. The experimental results show that the proposed control system is robust against rotor resistance variations.
- Identification of Induction Motor Parameters from Transient Stator Current Measurements
by Steven R. Shaw, Steven B. Leeb
Abstract - This paper describes three methods for estimating the lumped model parameters of an induction motor using startup transient data. A three-phase, balanced induction motor is assumed. Measurements of the stator currents and voltages are required for the identification procedure, but no measurements from the motor shaft are needed. The first method presented applies simple models with limited temporal domains of validity and obtains parameter estimates by extrapolating the model error bias to zero. This method does not minimize any specific error criterion, and is presented as a means of finding a good initial guess for a conventional iterative maximum-likelihood or least-squares estimator. The second method presented minimizes equation errors in the induction motor model in the least-square sense using a Levenburg- Marquardt iteration. The third identification method is a continuation of the Levenburg- Marquardt method, motivated by observed properties of some pathological loss functions. The third method minimizes errors in the observations in the least-squared sense, and is therefore a maximum-likelihood estimator under conditions of normality. The performance of the identification schemes is demonstrated with both simulated and measured data, and parameters obtained using the methods are compared with parameters obtained from standard tests.
- Linear Quadratic State Feedback and Robust Neural Network Estimator for Field-Oriented-Controlled Induction Motors
by Pompeo Marino, Francesco Vasca, Michele Milano
Abstract - A field oriented control scheme for induction motor with a Linear Quadratic optimal regulator and a robust neural network estimator is proposed. The state feedback is designed by using the synchronous frame motor model. The number of the states is increased in order to take into account the presence of two integrators on the flux and torque errors. The resulting model is suitably simplified and the corresponding approximations are discussed. The procedure proposed is shown to be suitable also for the design of the state feedback via pole placement technique. A comparison with standard PI regulators is provided. The rotor flux is estimated by using a robust neural network observer. The network training set is suitably designed in order to preserve the drive effectiveness also in the presence of large parameter uncertainties. The robust neural observer is compared with an Extended Kalman filter and a standard neural network observer. Using a 250 kW induction motor as case study, the simulation results show the effectiveness of the proposed solution both during transient and steady state operating conditions.
- Slow Resonance Ratio Control for Vibration Suppression and Disturbance Rejection in Torsional System
by Yoichi Hori, Hideyuki Sawada, Yeonghan Chun
Abstract - In the resonance ratio control, which we proposed for vibration suppression and disturbance rejection in torsional system, the estimation speed of the disturbance observer should have been much faster than the resonance frequency of the controlled system. However, too fast disturbance observer sometimes causes implementation problem. In this paper, we give the optimal speed of the disturbance observer and propose a novel technique named 'slow resonance ratio control'. It does not have any fast part in the controller. It also enables us to design the speed control and the vibration suppression control almost completely independently.
- Fuzzy Logic for Constant Force Control of End Milling
by Shiuh-Jer Huang, Chiou-Yuarn Shy
Abstract - Usually, the machining condition has significant variation resulted from the change of cutting depth and the intrinsic property of the workpiece. In order to maintain the performance of a classical PID control system, the tool life and machining quality, conservative feedrate and cutting depth change are pre-specified as the limitations of CNC operators. Therefore, the constant cutting force control is proposed as a useful approach for increasing the metal removal rate and the tool life. However, the model based controller can not handle the nonlinearity of force control system due to cutting condition variations. Here a fuzzy controller with learning ability was employed to improve both the system performance and adaptability. This control approach was implementaed on a retrofit old-fashioned milling machine for end milling process. The experimental results show that this control strategy has smooth feedrate and good cutting force dynamic responses.
- On Torque Ripple Reduction in Current-Fed Switched Reluctance Motors
by Aleksandar M. Stankovic, Gilead Tadmor, Zoran J. Coric, Ismail Agirman
Abstract - The paperadresses a basic control issue in Switched Reluctance Motor (SRM) drives the production of a ripple-free torque. Simple and largely model independent conventional supply waveforms are not able to satisfy this requirement. The goal of this work is to improve SRM dynamical performance by compansating for motor nonlinearities, while maintaining the robustness of conventional methods. The method is based on a complete parameterization of position dependent voltage and current profiles in ripple-free operation, and on a waveform optimization to minimize power supply requirements. Furthermore, model uncertainities are included to show that the proposed strategy consistantly outperforms the conventional policy. Experimental data verifying the analytical approach are included.
- Sensorless Full-Digital PMSM Drive with EKF Estimation of Speed and Rotor Position
by S. Bolognani, R. Oboe, Mauro Zigliotto
Abstract - The paper concerns with the realisation of a sensorless permanent magnet synchronous motor drive. Position and angular speed of the rotor are obtained through an Extended Kalman Filter. The estimation algorithm does not require either the knowledge of the mechanical parameters or the initial rotor position, overcoming two of the main drawbacks of other estimation techniques. The drive also incorporates a digital d-q current control, which can be easily tuned with locked rotor. The experimental set-up includes a PM synchronous motor, a PWM voltage source inverter and floating-point DSP-based control system.
- Efficiency-Optimized Direct Torque Control of Synchronous Reluctance Motor using Feedback Linearization
by Hyeoun-Dong Lee, Seong-Joo Kang, Seung-Ki Sul
Abstract - In this paper, a nonlinear controller capable of the high dynamic torque regulation and the efficiency optimization of the Synchronous Reluctance Motor(SynRM) using the input-output feedback linearization is proposed. The cross-coupling effects in SynRM model and the torque non-linearity due to the iron losses in torque-speed characteristics of the SynRM are discussed. And the criterion for the efficiency optimization is also introduced and investigated. Since the proposed nonlinear controller directly regulates the torque by selecting the product of d and q-axis torque currents as one of output variables, the nonlinear and cross-coupling aspects between the d and q-axis torque currents and the terminal currents can be eliminated. Hence, the linear torque-speed characteristic can be achieved. In addition, by controlling the power loss-minimizing criterion directly, the proposed controller can optimize the efficiency of the SynRM without deteriorating the dynamics performance.
Robotics and Vision
- A Fully Neural-Network-Based Planning Scheme for Torque Minimization of Redundant Manipulators
by Han Ding, S. K. Tso
Abstract - The aim of this paper is to develop a new method for minimizing joint torques of redundant manipulators in Chebyshev sense and to present a fully neural-network-based computational scheme for its implementation. Minimax techniques are used to determine the null space acceleration vector which can guarantee to minimize the maximum joint torque. For real-time implementation, we transform the proposed method into a computation of a recurrent neural network. At each time step, the neural network is adopted for both the solution of the least-norm joint acceleration and the determination of the optimum null space acceleration vector. Compared with previous torque minimization schemes, the proposed method enables more direct monitoring and control of the magnitudes of the individual joint torques than does the minimization of the sum of squares of the components. Simulation results demonstrate that the proposed method is effective for the torque minimization control of redundant manipulators.
Signal Processing
- Design of a Hardware Accelerator for Real-Time Moment Computation: A Wavefront Array Approach
by Donald L. Hung, H. D. Cheng, Savang Sengkhamyong
Abstract - In image processing, pattern recognition and computer vision, one of the most powerful techniques for feature extraction is to use moments. Real-time applications of this method, however, have been prohibited due to the intensive computation encountered in calculating the moments. One solution to this problem is to adopt specially designed hardware accelerators. This paper describes, from a practical standpoint, the design of a custom hardware accelerator for speeding up the moment computation. The design of the core functional units and the design of the overall system based on a wavefront array architecture are discussed. The moment accelerator can be easily configured into different sizes to meet diverse application requirements cost effectively. Testing results based on implementation using FPGA (field programmable gate array) devices show that at an affordable cost, the proposed hardware accelerator can deliver real-time speeds for moment computation. Elimination of this computational bottleneck makes it possible to use moments-based features in real-time industrial applications.
- Colour Grading of Randomly Textured Ceramic Tiles using Colour Histograms
by C. Boukouvalas, J. Kittler, R. Marik, Maria Petrou
Abstract - We present a method designed to solve the problem of automatic colour shade grading for industrial inspection of randomly textured multi-coloured ceramic tiles. Our grading method is based on the comparison of colour histograms and we present results of correctly grading several series of ceramic tiles, the differences of which were at the threshold of human perception.
Letters to the Editor
- Copper Loss Reduction of a Voice-Coil Motor for Cutting Tool Positioning using an Auxiliary Rotary Motor
by Lichuan Li
Abstract - When a voice coil motor (VCM) is used for cutting tool positioning under load forces, it is likely to have a high copper loss and consequently a high temperature rise. A novel solution that uses an auxiliary rotary motor (RM) is proposed. Design approach is discussed. A design example with simulations is given.
- Redundancy Resolution of Robotic Manipulators with Neural Computation
by Han Ding, S. K. Tso
Abstract - This paper presents a neural-network-based computational scheme for redundancy resolution of manipulators. The Tank- Hopfield (TH) network is adopted for pseudoinverse and inverse kinematics calculations and it can provide joint velocity and joint acceleration solutions within a time frame of the order of hundred nanoseconds. Incorporating the TH network into the redundancy resolution scheme allows planning algorithms to be implemented in real time. Simulation results for a 3-link planar manipulator are presented to demonstrate that the proposed approach is efficient and practical.
