Showing papers presented at "International Symposium on Industrial Electronics in 1995"

Digital control for switching converters

Abstract: In this paper, several different techniques for designing discrete controllers for switching power converter applications are presented. Simulation results are also provided for illustration purposes.

Energy-saving motion control for an autonomous mobile robot

Abstract: The paper proposes an energy saving motion control strategy suitable for autonomous mobile robots (AMRs) working in environments cluttered with unpredictable obstacles like civil buildings. The strategy has been tested on the PARIDE mobile robot developed at the Robotics Laboratory of the Department of Computer Science, University of Pavia (Italy).

Active filter solutions for utility interface

Abstract: Active filters are an effective means for harmonic compensation of nonlinear power electronic loads, of particular importance as electric utilities enforce harmonic standards such as IEEE 519. Harmonic compensation is an extremely cost-sensitive application since the value-added to the user is not apparent. This paper addresses the cost-effectiveness of various active filter topologies based on the application. Pure active filter solutions and hybrid active filter solutions are both seen to have merit in realizing a harmonic free utility interface for industrial loads rated at 100 kW to several MW. The objective of this paper is to present a methodology, for both the industrial user and the utility, to match the optimal active filter solution to their application.

Modelling and analysis of a web tension control system

Abstract: The paper describes the mathematical treatments and simulations for an experimental web tension control system. Differential equations for the web dynamics are formulated systematically for the system including a dancer roll to construct the block diagram. The web itself could be expressed in terms of fundamental elements, but it is concluded that the elastic or Maxwell models may not be proper ways to describe it. Simulations are performed on the model which has PI controllers, to clarify the physical phenomena and to see the validity of the mathematical model.

Inertial navigation system for mobile land vehicles

Abstract: This paper describes a prototype of an inertial navigation system for use in mobile land vehicles, such as cars or mobile robots. The complete system is composed by sensors, their mechanical mount and cabling, these connect to a PC card with local processing and memory, based on a Intel 80C196KC microcontroller. The sensors used were a piezoelectric vibrating gyroscope, two silicon accelerometers, two clinometers and also a magnetic flux-gate compass acting as an independent source for drift compensation. The working principle of the various sensors are presented. The experimental setup used for testing is based on a robot arm controlled in real-time to move the sensors along a known trajectory (velocity control).

Texture segmentation using hierarchical wavelet decomposition

Abstract: Texture segmentation deals with identification of regions where distinct textures exist. In this paper, a new scheme for texture segmentation using hierarchical wavelet decomposition is proposed. In the first step, using Daubechies' 4-tap filter, an original image is decomposed into three detailed images and one approximate image. The decomposition can be recursively applied to the approximate image to generate a lower resolution of the pyramid. The segmentation starts at the lowest resolution using the K-means clustering scheme and the result is propagated through the pyramid to a higher one with continuously improving segmentation.

Kalman filter for dynamic weighing system

Abstract: In the area of mass production, products are weighed using load cell based dynamic weighing systems. A load cell is an uncontrollable weighing device and the value of weight, for the passing product, is estimated by filtering the electrical signal from a load cell. Improvement in filtering increases the speed of weighing and enhances the measurement accuracy. In this paper a Kalman filter is proposed as a weight filter for the dynamic weighing system. Furthermore, the paper includes mathematical models of the load cell and forcing functions. These models are used to examine the suitability of the proposed Kalman filter approach. Since this approach is based on the accurate model of the system in question, the exact model of the load cell based dynamic weighing system has been derived and presented. For one particular value of the weight, the parameters of the model are time-varying due to the product coming onto the weigh-table and due to the product length. Changing the measurement from one value of the weight to another causes even greater changes in the values of the model parameters and introduces a nonlinearity in the system. Therefore an adaptivity approach has been considered and a solution proposed. The simulation and experimental results are presented and compared. The results achieved show that the Kalman filter may provide an effective alternative to the conventional method especially when the system is nonlinear and low frequency noise is incorporated in the bandwidth of the useful signal.

Disc motor with reduced unsprung mass for direct EV wheel drive

Abstract: A new drive system for electric vehicles is presented. An axial flux disc motor is used. The stator of the machine is attached to the chassis whilst the rotor directly drives the wheel. This arrangement reduces the unsprung mass compared with a conventional wheel drive and also, because of the machine geometry, permits movement of the wheel as it is perturbed by the road. The motor is modelled using 2D and 3D finite element techniques and estimates are given for the reduction in torque and induced EMF when the rotor disc and stator are misaligned.

Single phase rectifier with high power factor in continuous and discontinuous conduction mode

Abstract: This paper describes techniques for single phase AC-to-DC converter with near unity power factor. The topologies of single phase power factor correction (PFC), consisting of an AC source, a front-end diode rectifier, power stage of the converter with output filter, and a load, are proposed to achieve high performance and simple control circuit. The output voltage can be maintained above or below the peak AC input voltage by changing the duty cycle of the active switch. The PWM switch classification, AC-to-DC converter circuit topology, design of control circuit, simulation and experimental results are reviewed in this paper.

A fuzzy logic-based control of series DC motor drives

Abstract: This paper considers the application or fuzzy logic-based control to a DC motor drive system. The DC drive system is a DC series motor driven by a single-phase full bridge power converter. Two fuzzy controllers are proposed for the drive system, namely, speed and current controllers. Fuzzy control laws are developed to regulate the motor speed and maintain the current at a limiting value. A simulation study of the fuzzy controlled drive system has been carried out to validate the proposed controllers. The simulation result clarifies the superiority of the designed fuzzy controllers over classical PI controllers.

A robust vision system for vehicle licence plate recognition using grey-scale morphology

Abstract: Mathematical morphology is increasingly being used in image processing applications due to its inherent ease of operations. In this paper, the authors propose an algorithm based on grey scale morphological operations to detect the region of a vehicle licence plate from an image. The uniqueness of this algorithm, in comparison with other approaches to this problem, is that there are no special restrictions imposed on the input images. The robustness of the algorithm can be seen by the extremely good detection rate even when the images are fairly complex, in poor illumination, and noisy.

Electric drives for pump, fan, and compressor loads in automotive applications

Abstract: Optimization of automotive power plants is moving in the direction of increased utilization of electrically driven auxiliary loads. Such subsystems include cooling and power assist functions. The power levels required by these loads range from hundreds to tens of hundreds of watts. At these power levels, the current ratings of switching devices and motor phase leads, assuming tradition drive and motor designs, can exceed 100 amps at the standard 13.5 VDC bus level. This paper discusses alternative drive and motor configurations which will mitigate the current rating requirements of the drive and motor components. The authors present the case for usage of H-bridge and bipolar bus drives and usage of five-phase machines.

Use of power electronic converters in wind turbines and photovoltaic generators

Abstract: In this paper, a brief review is presented of common electrical generation schemes for wind turbines (WTs) and photovoltaics (PVs). Attention is mainly focused on the power converter interfaces used for the grid connected operation of the renewable generators. The WT soft starting arrangements are described and the most common variable speed operation configurations are presented and discussed. The fundamental characteristics and requirements of the power conditioning equipment used in PVs are outlined and the power converters of certain PV generators are briefly presented.

Fuzzy tuned PI controllers for series connected DC motor drives

Abstract: A new approach for tuning a PI controller for the speed adjustment of a series-connected DC motor drive system is presented. Using the classical Ziegler-Nichols technique, the nominal feedback gains of a PI speed controller are obtained. However, the model of the system is nonlinear and, in order to achieve an improved performance, it is proven that the PI gains must be corrected in accordance to the changes from the nominal operation. Taking into account this last ascertainment, a suitable fuzzy logic controller is constructed involving time variant feedback gains. Extensive simulation studies are conducted to compare the response of the system with the fuzzy tuned controller to the response given with the classical static Ziegler-Nichols controller. In all cases, a significantly improved performance of the transient behaviour of the closed-loop system is verified.

High power, high performance parallel connected multiconverters: analysis and control

Abstract: Recently, there has been an increasing demand for high power, high performance converters for power system applications, motor drives, etc. The low switching frequency of existing devices poses a severe limitation that can be overcome by the use of interconnected smaller power converters (multiconverter) with appropriate control. This paper concentrates on the transformerless parallel connection of three-phase power converters, that offers interesting features like simplicity, gracefully degrading operation, high reliability, easy expandability and easy maintenance. Based on its state space model, the decoupling and the behavior of the balanced and zero sequence currents are explained. The PWM is explained as a special sample and hold element. After showing the requirements for the current controller of a parallel connected multiconverter, and discussing individual and centralized control, the use of an individual deadbeat controller is discussed. Influence of the sampling times displacement is analyzed, and the harmonics minimization by optimum zero sequence is proposed. Both are confirmed by simulation results.

A comparison of various VSS techniques on the control of automated guided vehicles

Abstract: In this paper, various VSS techniques based on sliding mode control (SMC) including a novel approach are proposed for the control of automated guided vehicles (AGV). The first approach is a classical SMC based on Lyapunov design. The second approach is classical SMC with the estimation of the equivalent control, and the third one is a novel approach and eliminates the chattering. The third method is also modified with a different estimation of the equivalent control. The last scheme is observed to be the most powerful method and easily applicable in real systems. The methods are compared and implementation results are presented.

Discrete sliding mode control of two mass system

Abstract: This paper deals with control of two mass system coupled by flexible shaft Fast response of a linear controller produces a peak in the control which might drive the system into the forbidden domain The main contribution of this paper is to examine, via experimental investigations of a two mass system, the engineering feasibility of an observer based discrete-time sliding mode control design to prevent the system from entering into the nonadmissible domain

Neural networks in robotics: state of the art

Abstract: This paper provides a short review of the neural network approach to system control with reference to robotic systems Starting with an exposition of the main neurocontrol architectures, the paper overviews the literature on the application of neural networks to robot kinematics, dynamics, path planning and motion control, including some work on neurofuzzy control To appreciate better robot neurocontrol, an unsupervised robot neurocontroller is presented in some detail The paper includes a discussion of the criticism made to the neural control paradigms, and an outline of some interesting areas for further research

Power quality and nonlinear load voltage stabilization using error-driven switched passive power filter

Abstract: The paper presents an error-driven rule-based control system for passive power filter switching to enhance power quality and reduce voltage flicker. The scheme extends the functionality of a fixed passive power filter by modulating the filtering action using a solid-state switching power converter.

High performance induction motor control via feedback linearization

Abstract: This paper presents a feedback linearization approach for high performance induction motor control. The principle of the method is discussed and compared with most popular in AC motor drive technology field oriented control technique. Some oscillograms illustrating the properties of the PWM inverter-fed induction motor with control via feedback linearization are presented.

Multilevel voltage source converters for medium voltage adjustable speed drives

Abstract: In this paper a brief review of multilevel converter structure is presented. The main characteristics of phase shifted output transformer converters, modular converters and (strictly defined) multilevel converter are described. In the second part of the paper the application of multilevel converter to medium voltage adjustable speed drives (ASD), as jointly studied by Ansaldo and EPRI is illustrated.

Neural networks applied for induction motor speed sensorless estimation

Abstract: In this paper, two schemes using neural networks (NN) as speed estimators in induction motor field oriented controlled (FOC) drives are compared. The first estimator consists of a two-layer neural network (often called a perceptron) while in the second a three-layer neural network is used for motor speed estimation. Both estimators are simulated with an indirect field oriented controller (IFOC) for induction motor drives.

MORRPH: a modular and reprogrammable real-time processing hardware

Abstract: MORRPH is a general-purpose reconfigurable processing unit, primarily intended for real-time 2-dimensional image processing. Its flexible architecture allows it to be used for other applications including 1-dimensional signal processing, 2-dimensional cellular automata problems, and 3-dimensional image processing. The modular, open-ended (incompletely specified) architecture consists of a rectangular mesh of processing elements. Each processing element contains one socket for a field programmable gate array (FPGA) chip and one socket for support processing chips. The FPGA chips provide an array of logic resources, consisting of combinational logic functions, flip-flops, and interconnections. Empty support sockets allow several discrete IC chips to be tightly coupled to each FPGA, the type of IC is determined by the individual requirements of the task to be performed by the MORRPH board. This allows the support chips to implement functions that are not efficiently realized by the FPGAs. These memory, arithmetic, or processing support chips are specified when a particular application is compiled for the MORRPH board. If a single MORRPH board does not provide enough computational power for a particular application, several MORRPH boards can be interconnected to solve the task. The MORRPH architecture is implemented as an adapter The modular nature of the MORRPH architecture at both the chip and board level allows a very efficient implementation of a required machine vision task.

An artificial neural network to linearize a G (tungsten vs. tungsten 26% rhenium) thermocouple characteristic in the range of zero to 2000/spl deg/C

Abstract: An alternative way to correct sensors in order to exhibit good linearity is proposed. This paper describes the design and behavior of an artificial neural network (ANN) with two hidden layers of twelve neurons each for linearizing a static characteristic of a G thermocouple ranged from zero to 2000/spl deg/C. The use of interpolation methods to perform such corrections is also discussed. In the training phase of the ANN, backpropagation and random optimization algorithms have jointly been used to adjust the weights of the network for a desired final error. After training the ANN, it is then used as a neural linearizer to generate the primary variable (temperature) from the thermocouple's output voltage. The accuracy of this method is compared with those obtained by interpolation.

PLD implementation of logic controllers

Abstract: This paper presents a unified design environment of concurrent logic controllers, based on the use of Petri nets, rule-based description languages and PL4 specification languages (especially AMD Palasm 4). The straightforward templates are presented that made possible a rule-based Petri net specification to be simulated and then efficiently synthesised with modern programmable devices. Though the example presented in this paper is relatively trivial, the concepts are directly applicable in the more realistic designs.

Piecewise modeling and optimal commutation of switched reluctance motors

Abstract: A piecewise modeling approach to characterize the nonlinearities of switched reluctance machines is presented. In particular, the phase torque function, which is a highly nonlinear function of phase current and rotor position, is shown to be modeled by simple, yet accurate, piecewise analytic expressions. Consequently, implementation of instantaneous torque control by on-line computation, rather than by look-up tables is a feasible option using the piecewise model. Another feature of the piecewise modeling approach is that it simplifies the formulation and solution of various optimization problems. Two optimal commutation methods are presented for instantaneous torque control: the first minimizes copper losses, whereas the second minimizes the rates-of-change of phase currents.

Full-bridged MOSFET DC-to-RF inverter for high frequency ultrasonic transducer at 3 MHz

Abstract: Described is a full-bridged MOSFET DC-to-RF inverter operating at a frequency of 3 MHz for driving a high frequency ultrasonic transducer for cleaning material surfaces. The full-bridged MOSFET DC-to-RF inverter generates an RF power of 60 W with a power conversion efficiency of 79 to 87% at 3 MHz when an ultrasonic transducer with a very low impedance in the order of 1 to 5 ohms is connected to the inverter. The ultrasonic transducer was satisfactorily operated when the ultrasonic transducer was driven from the full-bridged MOSFET DC-to-RF inverter.

Modular parallel three-phase inverter system

Abstract: This paper develops three-phase inverter modules that have the following functions: (1) inverters for stand-alone operation; (2) inverters in parallel; and (3) inverters in parallel with the utility system. For obtaining parallel operation, the parallel technique for a voltage-controlled PWM inverter and (N-1) current-controlled PWM inverters is proposed in this paper. Through the current control, the current-controlled PWM inverter can be operated in synchronism with the voltage-controlled PWM inverter. By a load-sharing center, the load is shared to each inverter in parallel, and accurately limits the output current of each inverter to its maximum rating. In this paper, system operations are described in detail and experimental results are developed. From the experiment results, this proposed scheme is adequate.

A single-phase buck-boost AC-to-DC converter with high-quality input and output waveforms

Abstract: This paper describes a new single-phase buck-boost power factor correction (PFC) converter with output-voltage-ripple-free operation. The rectifier is operated by two modulators which obtain PFC and the ripple-free operation, respectively. The modulator controls the buck-boost switch to obtain PFC. On the other hand, another modulator controls squire-value of instantaneous-inductor-current to perform the ripple-free operation. In both modulation, space or time-integral-value of the input and output currents in each modulation period is controlled directly and indirectly, respectively. Thus, modulation errors or distortions of the currents are eliminated even if the DC-inductor-current produces large ripples. The theories and combination technique of the modulators, implementation and experimental results are shown.

Minimal optimal topologies for invariant higher-order neural architectures using genetic algorithms

Abstract: Higher-order neural networks (HONNs) are successful in performing position, rotation and scale (PRSI) recognition. A major limitation of these networks is the combinatorial explosion of the higher-order terms, which increases the complexity of the network architecture. This work proposes a genetic optimisation scheme for determining the minimal optimal topology of a network for automated inspection of industrial parts.