Milan Bebic

Controlled multi-motor drives

Controlled multi-motor drives are used in a great number of industrial plants. The functioning of large and complex systems such as ironworks, paper mills, excavators, etc. depends on the performance of the controlled multi-motor drives. A systematic survey of multi-motor drives based on the method of coupling and mutual influence is presented in the paper. Following that, an overview of the appropriate control algorithms, sorted by the principle of operation and the means of realization, is given. The paper is illustrated with selected applications of controlled multi-motor drives from the authors practice

Gain scheduling control of DC motor drive with field weakening

A new adaptive control system for a DC motor drive with field weakening is proposed. The adaptation mechanism is based on the gain scheduling. A deep knowledge of the phenomena in the drive was necessary to define the scheduled variables that capture the essential nonlinearities of the process considered. However, in practice, to realize the proposed adaptive control system, the only a priori knowledge required is the experimentally determined magnetization curve. Simulation and experimental results indicating high performances of the control system proposed, are presented.

Controlled induction motor drives supplied by frequency converters on belt conveyors — modeling and commissioning

During the past two decades, drive and control system of belt conveyors on open pit lignite mines have seen significant advances. The main demand for new construction of belt conveyors was the increase of reliability, unit capacity, minimization of personal, reduction of maintenance cost, increase of safety, reduction of consumed energy, etc. The paper presents detailed mathematical model of the belt conveyor suitable for analyses of both static and transient operating regimes. The model includes electrical drive system of the conveyor, and the mechanical part, with the special attention given to the elastic nature of the belt. Simulation results of the developed model for the drive with frequency converter are presented. Experimental results from the field measurements confirm the validity of the model.

Optimal utilization of the bulk material transportation system based on speed controlled drives

The main demand for construction of new belt conveyors in open pit mines (OPM) is the increase of safety and system capacity, minimization of personal, reduction of maintenance cost, consumed energy, etc. The paper presents the algorithm for speed control of the system of belt conveyors, in terms of improved system efficiency. The algorithm is based on the principle of optimum utilization of the available material cross section on the belt. The algorithm is developed and tested on the detailed mathematical model of the drive system with the rubber belt, transporting variable capacity of the bulk material, measured at the input of the system. The simulation results are verified through performed measurements of characteristic values, which best illustrates the response of the system to the applied control strategy in the control center of the belt conveyor system with remote control.

Energy efficiency in transportation of bulk material with frequency controlled drives

The paper presents the algorithm for speed control of belt conveyors, in terms of optimal energy consumption. The algorithm is based on principle “minimal speed means minimum power”. The minimal speed is calculated as a ratio of transported capacity of bulk material and maximum possible material cross section on the belt.

Fuzzy speed control of belt conveyor system to improve energy efficiency

The paper presents a control strategy for the system of belt conveyors with adjustable speed drives based on fuzzy logic control. The proposed control structure is developed and tested on the detailed mathematical model of the drive system with the rubber belt. The presented algorithm is implemented on the new variable speed belt conveyor system with remote control on an open pit mine. Results of measurements on the system are used to compare the proposed algorithm with another approach to optimum speed determination based on the method of sequential quadratic programming. It is proved that both solutions provide minimum of electrical energy consumption of the drive under given constraints.

Realization of Rewinder With a Reduced Number of Sensors

When adequately maintained, the mechanical system of rewinders and similar machines in paper industry may have a significantly longer service life than its electrical and control systems. Over the lifetime of the facility, a rewinder may experience several major maintenance cycles, and these generally include significant upgrades to the electrical drive and control system. These upgrades present an opportunity to modify the design of the control system to eliminate some of the sensors or to provide signal redundancy by using state estimation. During such major reconstruction of a paper-board rewinder, it was noticed that the shipping-roll radius and the web tension force can be accurately estimated from the measurements available within the drives control system. This paper presents the implementation of the two estimators on a commercial production rewinder. Test results from the equipment in service show that the measured signals can be supplemented with the estimated ones to provide an alternative in the event of sensor malfunction or to enable trending of accuracy of calibration. Both applications have an entitlement to reduce the downtime of the rewinder, as the replacement of the faulted sensor can be scheduled for the next planned idle period of the machine.

Analysis of Torque Ripple Reduction in Induction Motor DTC Drive with Multiple Voltage Vectors

This paper shows an analysis of torque ripple reduction in modified DTC algorithm by using multiple voltage vectors with the appropriate multilevel hysteresis controller. A short theor ...

Control of the main working axes of bucket wheel excavators according to the criterion of desired capacity

The bucket wheel excavator is basic mining machine used on open pit mines with a continuous excavation process for soft and medium-hard materials. The increase in the need for ever greater quantities of excavated material has led to excavators being constructed today with a daily production capacity greater than 200,000 m3. Aside from the time and capacity availability of the excavators, to achieve efficient production, the manner in which they are controlled is also of great significance. The analysis of the technology for excavating massifs, as well as the structure and geometry of excavators, has led to the greatest number of applied solutions for control of excavators being through automatic operation: no/cos and P=const. Due to the non-homogenous structure of material and the inconsistent and unpredictable geometry of the excavated block, the aforementioned methods do not provide the necessary efficiency for the operation of the excavator. The development of systems for measuring the volume flow of material and their application on excavators makes it possible for the measurement results to be used not only for statistical analysis, but also to develop algorithms for control of excavators. The location where the measurement system is installed complicates the use of its measurement results. Specifically, the information on the instantaneous production which the control system receives from the measurement system is delayed by the amount of time it takes the excavated material to travel from the bucket wheel to the location where its volume is measured (one of the conveyors on the excavator). In this work we will present the algorithm for control of a bucket wheel excavator according to the criterion of desired capacity, where the results of the system for measuring volume flow are used as feedback information on the capacity. The results of measurements performed on the terrain verify the control strategy, which is developed and tested based on mathematical model of bucket wheel excavator presented in the paper.

Energy efficiency in paper industry — Study of two cases

The paper presents two case studies in order to illustrate an efficient usage of energy in paper industry and to point out the benefits gained. Two different approaches for obtaining higher energy efficiency of the paper production process show that energy efficiency in paper industry must be considered as a multidisciplinary field. Differences in realization of paper machine systems for control and supervision are also presented in the paper.