High-performance control of dual-inertia servo-drive systems using low-cost integrated SAW torque transducers

Abstract—This paper provides a systematic comparative study of compensation schemes for the coordinated motion control of two-inertia mechanical systems. Specifically, classical proportional–integral (PI), proportional–integral–derivative (PID), and resonance ratio control (RRC) are considered, with an enhanced structure based on RRC, termed RRC+, being proposed. Motor-side and load-side dynamics for each control structure are identified, with the “integral of time multiplied by absolute error” performance index being employed as a benchmark metric. PID and RRC control schemes are shown to be identical from a closed-loop perspective, albeit employing different feedback sensing mechanisms. A qualitative study of the practical effects of employing each methodology shows that RRC-type structures provide preferred solutions if low-cost high-performance torque transducers can be employed, for instance, those based on surface acoustic wave tecnologies. Moreover, the extra degree of freedom afforded by both PID and RRC, as compared with the basic PI, is shown to be sufficient to simultaneously induce optimal closed-loop performance and independent selection of virtual inertia ratio. Furthermore, the proposed RRC+ scheme is subsequently shown to additionally facilitate independent assignment of closed-loop bandwidth. Summary attributes of the investigation are validated by both simulation studies and by realization of the methodologies for control of a custom-designed two-inertia system

Free Vibration Response of a Frame Structural Model Controlled by a Nonlinear Active Mass Driver System

Active control devices, such as active mass dampers, are mainly employed for the reduction of wind-induced vibrations in high-rise buildings, with the final aim of satisfying vibration serviceability limit state requirements and of meeting appropriate comfort criteria. When such active devices, normally operating under wind loads associated with short return periods, are subjected to seismic events, they can experience large amplitude vibrations and exceed stroke limits. This may lead to a reduced performance of the control system that can even worsen the performance of the whole structure. In this paper, a nonlinear control strategy based on a modified direct velocity feedback algorithm is proposed for handling stroke limits of an active mass driver (AMD) system. In particular, a suitable nonlinear braking term proportional to the relative AMD velocity is included in the control law in order to slowdown the device in the proximity of the stroke limits. Experimental and numerical free vibration tests are carried out on a scaled-down five-story frame structure equipped with an AMD to demonstrate the effectiveness of the proposed control strategy

Регулирование координат электромеханической системы прокатного стана на основе наблюдателя упругого момента

The paper considers the electromechanical system of the reversing stand of the plate rolling mill 5000 of PJSC “Magnitogorsk Metallurgical Plant” (PJSC “MMK”). The performed experimental studies of transient processes in the mode of gripping metal by rolls allowed establishing unacceptable dynamic loads of an oscillatory nature and a loss of controllability of the electric drive. This confirms the need for the development of control methods that limit the motor and spindle torques. It is noted that the known control systems for the speed modes of an electric drive, which decrease the elastic moment due to the preliminary closing of the angular gaps, are, in essence, open-loop speed control systems. This does not provide for the controlled regulation of coordinates in dynamic modes. The paper proposes the development of a closed system for automatic control of coordinates of a two-mass electromechanical system with an observer of the moment of the elastic shaft and the speed of the second mass. An observer of the unmeasurable parameters of a two-mass rolling mill system has been developed. It provides an indirect determination (recovery) of the roll speed and the spindle torque in on-line mode. It is based on a system of equations in the state space. By comparing the reconstructed and experimentally obtained transient processes, the satisfactory accuracy of the results has been confirmed. Based on the proposed observer, the authors developed an automatic control system (ACS) of the roll speed with subordinate contours of the elastic shaft moment, speed and engine torque. The setting of closed-loop regulators has been substantiated. Transient processes of moments and velocities are considered at impact application of a load with increased speed of the second mass speed control loop. The analysis of the LAFC and LPFC confirmed the stability of the developed system in the frequency range. The analysis of experimental data substantiated a conclusion about the influence of the angular gap on the accuracy of the elastic moment recovery in the mode of metal capture by rolls. Prospects for the introduction of developments at mill 5000 and other rolling mills operating with shock load are noted. Рассматривается электромеханическая система реверсивной клети толстолистового прокатного стана 5000 ПАО «Магнитогорский металлургический комбинат» (ПАО «ММК»). В результате экспериментальных исследований переходных процессов в режиме захвата металла валками установлены недопустимые динамические нагрузки, имеющие колебательный характер, и потеря управляемости электропривода. Это подтверждает актуальность разработки способов управления, обеспечивающих ограничение моментов двигателя и шпинделя. Отмечено, что известные системы управления скоростными режимами электропривода, обеспечивающие снижение упругого момента за счет предварительного замыкания угловых зазоров, по своей сути являются разомкнутыми системами задания скорости. Это не позволяет обеспечить контролируемое регулирование координат в динамических режимах. В качестве перспективного направления предложена разработка замкнутой системы автоматического регулирования координат двухмассовой электромеханической системы с наблюдателем момента упругого вала и скорости второй массы. Разработан наблюдатель неизмеряемых параметров двухмассовой системы прокатного стана, обеспечивающий косвенное определение (восстановление) скорости валка и момента шпинделя в online-режиме. В его основу положена система уравнений в пространстве состояний. Путем сопоставления восстановленных и экспериментально полученных переходных процессов подтверждена удовлетворительная точность результатов. На основе предложенного наблюдателя разработана система автоматического регулирования (САР) скорости валка с подчиненными контурами упругого момента вала, скорости и момента двигателя. Обоснована настройка регуляторов замкнутых контуров. Рассмотрены переходные процессы моментов и скоростей при ударном приложении нагрузки при увеличенном быстродействии контура регулирования скорости второй массы. В результате анализа ЛАЧХ и ЛФЧХ подтверждена устойчивость разработанной системы в частотном диапазоне. На основе анализа экспериментальных данных констатирован вывод о влиянии углового зазора на точность восстановления упругого момента в режиме захвата металла валками. Отмечены перспективы внедрения разработок на стане 5000 и других прокатных станах, работающих с ударным приложением нагрузки

Constrained Optimized Command Shaping for Minimizing Residual Vibration in a Flexible-Joint Robot

Joint flexibility is a natural trait of robotic manipulators, which limits fast point-to-point motion. Remedial measures are often employed to enable these systems to perform their goal in a desired manner. These measures range from either modifying the system dynamics such that the resonance is increasingly damped or by designing cleverly shaped input commands that avoid exciting the resonant modes altogether. In this work, a numerical framework for generating constrained shaped commands for a two-link flexible-joint robot is presented. To optimally select the design parameters for generating shaped commands, the effects of subjecting the optimization to mutually exhaustive constraints of residual vibration performance, speed of motion and size of actuators has been studied. Few important performance metrics to characterize the performance are also introduced and discussed. The framework has been tested for two basis functions, ramped sinusoid and segmented versine, in simulations and experiments and performance is evaluated against one another and an unshaped bang-bang profile. In practice, it has been shown that the constrained numerical approach reduces vibration in the nonlinear robot system in a more effective and efficient manner than the unconstrained closed-form solution

Lithium-Ion Ultracapacitor Energy Storage Integrated with a Variable Speed Wind Turbine for Improved Power Conversion Control

The energy of wind has been increasingly used for electric power generation worldwide due to its availability and ecologically sustainability. Utilization of wind energy in modern power systems creates many technical and economical challenges that need to be addressed for successful large scale wind energy integration. Variations in wind velocity result in variations of output power produced by wind turbines. Variable power output becomes a challenge as the amount of output power of the wind turbines integrated into power systems increases. Large power variations cause voltage and frequency deviations from nominal values that may lead to activation of relay protective equipment, which may result in disconnection of the wind turbines from the grid. Particularly community wind power systems, where only one or a few wind turbines supply loads through a weak grid such as distribution network, are sensitive to supply disturbances. While a majority of power produced in modern power systems comes from synchronous generators that have large inertias and whose control systems can compensate for slow power variations in the system, faster power variations at the scale of fraction of a second to the tens of seconds can seriously reduce reliability of power system operation. Energy storage integrated with wind turbines can address this challenge. In this dissertation, lithium-ion ultracapacitors are investigated as a potential solution for filtering power variations at the scale of tens of seconds. Another class of issues related to utilization of wind energy is related to economical operation of wind energy conversion systems. Wind speed variations create large mechanical loads on wind turbine components, which lead to their early failures. One of the most critical components of a wind turbine is a gearbox that mechanically couples turbine rotor and generator. Gearboxes are exposed to large mechanical load variations which lead to their early failures and increased cost of wind turbine operation and maintenance. This dissertation proposes a new critical load reduction strategy that removes mechanical load components that are the most dangerous in terms of harmful effect they have on a gearbox, resulting in more reliable operation of a wind turbine