Saad Tapuchi

A Differential State-Space Approach to Simultaneous Emulation of Uncertainties and Disturbances in Voltage-Controlled Brushless Motors

A method that allows emulation of parameter uncertainties and external disturbances without any mechanical and electrical parts supplementary to the electric drive is proposed. The emulating signal reflecting the desired changes is created in software and added to the nominal controller output, forcing the unperturbed motor output to resemble the output of a motor with actual uncertainties and disturbances. The proposed method allows simultaneous emulation of any combination of parameter variations and unpredicted disturbances. The method can be related to a class of advanced hardware-in-the-loop simulations, where the nominal hardware is present in the test bed in addition to the controller. The technique can be used to thoroughly test the performance of advanced control algorithms before mass production or for didactic purposes in an educational laboratory using motion control kits found on the market. Simulation and experimental results are reported to prove the feasibility of the proposed approach.

Input‐output nominalization of linear systems with slow‐varying uncertainties

Purpose – The purpose of this paper is to present a method to compensate slow varying disturbances and plant parameter drifts using a simple yet robust algorithm called input‐output nominalization.Design/methodology/approach – In case of known uncertainties, an analytical expression of pre‐computed feed‐forward compensation command is derived. In presence of unknown disturbances and parameter drifts, the control algorithm uses a proportional‐integrative estimator‐based nominalizer. It creates a nominalizing signal, reflecting the deviation of the system from its nominal form using plant input and output. The signal is subtracted from the nominal controller output to cancel the uncertainty and disturbances effects.Findings – As a result, the uncertain plant and the nominalizer quickly converge to the nominal plant. Therefore, a simple controller tuned according to the nominal plant can be used despite the disturbances and parameter drifts and a nominal response is always obtained. Simulation and experiment...

Wind turbine performance index

In this paper, two approaches to calculating Capacity Factor of fixed speed wind turbines are reviewed and then compared using a case study. The quasi-exact approach utilizes discrete wind raw data (in the histogram form) and manufacturer provided turbine power curve (also in discrete form) to numerically calculate the capacity factor. On the other hand, the approximate approach employs a continuous probability distribution function, fitted to the wind data as well as continuous turbine power curve, resulting from double-polynomial fitting of manufacturer-provided power curve data. The latter approach, while being an approximation, can be solved analytically thus providing a valuable insight into the factors, affecting the Capacity Factor. Moreover, several other merits of wind turbine performance are based on the analytically derived equations and hence are an approximation as well. The note shows that the results obtained by employing both approaches are very close, thus the analytically derived approximations are valid and may be used for wind turbine performance evaluation.

Emulating time varying nonlinear uncertainties and disturbances in linear time invariant systems

An approach allowing the creation of parameter uncertainties and external disturbances without any hardware parts supplementary to the nominal system is proposed in this manuscript. The emulating signal, reflecting the plant variations, essential for testing of controllers, is created in software and added to the plant input, forcing the nominal system output to resemble the output of a system with actual uncertainties and disturbances, thus allowing us to test the controller’s robustness prior to an actual field test. In addition, the full state vector of the emulated system may be reconstructed and fed back to the controller, if necessary. The proposed methods allow simultaneous emulation of any combination of time-varying parameter variations and external disturbances. The method can be related to a class of enhanced hardware-in-the-loop simulations, since the nominal hardware is present in the setup in addition to the controller under test. The proposed techniques can be used to test the performance of advanced control algorithms before their mass production. Extended simulation results are reported to confirm the feasibility of the proposed approaches.

Capacitance-Increase Method

A new method for capacitance increase is proposed, thus allowing for capacitance standards with a sixfold higher value than those currently found in the market. The method can be used for capacitance increase in any standard and provides a solution for calibration problems of high-capacitance four-terminal meters. The increase in capacitance is based on the introduction of inductive coupling between the current and potential circuits in devices with four electrodes. The output capacitance is created by the summation of the capacitive and inductive parameters that were formed in various channels. The operating frequency range resides at the left of the resonant frequency and is separated from the resonance by a range of frequencies called ¿protective band¿. The limitations on the width of this band and the quality factor are considered in this paper and are discussed in depth. It is shown that standards should be calibrated on each operating frequency when using the proposed method. The uncertainties of the method are also analyzed, and the factors that affect the uncertainty increase are clearly indicated. Simulation and experimental results are presented to verify the proposed method and demonstrate its feasibility.

Synchronous Motor Pull-in Process Analysis

In this paper, simple approach to analyzing the starting procedure of synchronous motors (SMs) is presented with an emphasis on the pull-in process. Instead of the classical, mostly intuitive pulling-repelling torque approach, an analytical method based on the motor mechanical part swing equation is employed. Factors affecting starting and pull-in processes are clearly indicated and torque impulse balance leading to a pull into step is revealed. It is shown that if the motor fails to pull into step within a single oscillation, it can still be synchronized during one of the succeeding acceleration periods. The crucial role of the excitation winding energizing instant is demonstrated as well. Moreover, the revealed similarity between the SM and phase locked loop (PLL) operations, leads to the conclusion that the algorithms use for analyzing the operation of one may be employed for investigating the other. Experimental results are given to demonstrate the different scenarios, mentioned in the manuscript.

Novel differential linear electrostatic motor with light weight rotor

The paper proposes a new type of linear electrostatic motor operated on a principle of the electric field effect on dielectric material. The proposed motor has a simple structure that simplifies the production process. Moreover, the motor is designed with very light weight rotor. As a result, the friction and power losses of the motor are reduced. Additional advantage of this motor is that it is not influenced by external magnetic fields. Furthermore, the proposed motor has advanced motion control options that allow precise control of velocity and position profiles. Extensive simulation results of the proposed motor at different operation modes are presented and analyzed. The simulation results demonstrate proposed control methods and show the practicability of the motor.

Boundary controller for switched capacitor converters

A boundary controller to switched capacitor circuit is proposed. Conventional average output voltage control usually leaves the voltage ripple uncontrolled. The proposed controller keeps the ripple between two desired bounds allowing connecting a smaller output capacitor. Moreover, it can solve the start up or other non-steady states problems. Simulation results are presented to validate the theoretical analysis.

Phase-shifted Discontinuous Pulse-Width Modulation Methods for Multi-level Inverters Operated in Over-modulation Range

Abstract This article presents combinations of the generic phase-shifted pulse-width modulation method with conventional discontinuous pulse-width modulation methods operated in the over-modulation range. The treated discontinuous methods are the third harmonic injection, Depenbrocks DPWM1, and Ogasawaras DPWM2. The significant advantage of the present approach over the conventional phase disposition pulse-width modulation method is the equal power flow between the H-bridges and the improved distribution of the switching operations number between them. Furthermore, they provide improved linearity in the over-modulation range. The proposed pulse-width modulation methods are analyzed by extensive simulation results. Several aspects, such as the total harmonic distortion factor of the inverter output currents and voltages, harmonic content, frequency spectrum distribution, and switchings number, are studied.

Input stage enhancement of a switched-capacitor switched inductor circuit

This paper proposed the enhance of the input stage of a switched-inductor switched capacitor DC-DC converter. The inductors are charged in parallel from input voltage and discharged in series to the capacitor which are connected in parallel to each other, and then the capacitors are discharges in series to the load. Thus, the converter can achieve high step-up voltage gain which means high input currents. The number of switches in the input stage of this converter was reduced, reducing conduction losses and achieving a better efficiency. Mathematical analyses of the steady state operation and simulation results are presented. The simulations are according to the original circuit, 1kW output power, 700V output voltage and input voltage within the range from 70V to 120V.