Function based control for bilateral systems in tele-micromanipulation

Design of a motion control system should take into account (a) unconstrained motion performed without interaction with environment or any other system, and (b) constrained motion with system in contact with environment or other systems. Control in both cases can be formulated in terms of maintaining desired system configuration what makes essentially the same structure for common tasks: trajectory tracking, interaction force control, compliance control etc. The same design approach can be used to formulate control in bilateral systems aimed to maintain desired functional relations between human and environment through master and slave motion systems. Implementation of the methodology is currently being pursued with a custom built Tele-micromanipulation setup and preliminary results concerning force/position tracking and transparency between master and slave are clearly demonstrated

Disturbance Observer-based Robust Control and Its Applications: 35th Anniversary Overview

Disturbance Observer has been one of the most widely used robust control tools since it was proposed in 1983. This paper introduces the origins of Disturbance Observer and presents a survey of the major results on Disturbance Observer-based robust control in the last thirty-five years. Furthermore, it explains the analysis and synthesis techniques of Disturbance Observer-based robust control for linear and nonlinear systems by using a unified framework. In the last section, this paper presents concluding remarks on Disturbance Observer-based robust control and its engineering applications.Comment: 12 pages, 4 figure

Rotors on Active Magnetic Bearings: Modeling and Control Techniques

In the last decades the deeper and more detailed understanding of rotating machinery dynamic behavior facilitated the study and the design of several devices aiming at friction reduction, vibration damping and control, rotational speed increase and mechanical design optimization. Among these devices a promising technology is represented by active magnetic actuators which found a great spread in rotordynamics and in high precision applications due to (a) the absence of all fatigue and tribology issues motivated by the absence of contact, (b) the small sensitivity to the operating conditions, (c) the wide possibility of tuning even during operation, (d) the predictability of the behavior. This technology can be classified as a typical mechatronic product due to its nature which involves mechanical, electrical and control aspects, merging them in a single system. The attractive potential of active magnetic suspensions motivated a considerable research effort for the past decade focused mostly on electrical actuation subsystem and control strategies. Examples of application areas are: (a) Turbomachinery, (b) Vibration isolation, (c) Machine tools and electric drives, (d) Energy storing flywheels, (e) Instruments in space and physics, (f) Non-contacting suspensions for micro-techniques, (g) Identification and test equipment in rotordynamics. This chapter illustrates the design, the modeling, the experimental tests and validation of all the subsystems of a rotors on a five-axes active magnetic suspension. The mechanical, electrical, electronic and control strategies aspects are explained with a mechatronic approach evaluating all the interactions between them. The main goals of the manuscript are: • Illustrate the design and the modeling phases of a five-axes active magnetic suspension; • Discuss the design steps and the practical implementation of a standard suspension control strategy; • Introduce an off-line technique of electrical centering of the actuators; • Illustrate the design steps and the practical implementation of an online rotor selfcentering control technique. The experimental test rig is a shaft (Weight: 5.3 kg. Length: 0.5 m) supported by two radial and one axial cylindrical active magnetic bearings and powered by an asynchronous high frequency electric motor. The chapter starts on an overview of the most common technologies used to support rotors with a deep analysis of their advantages and drawbacks with respect to active magnetic bearings. Furthermore a discussion on magnetic suspensions state of the art is carried out highlighting the research efforts directions and the goals reached in the last years. In the central sections, a detailed description of each subsystem is performed along with the modeling steps. In particular the rotor is modeled with a FE code while the actuators are considered in a linearized model. The last sections of the chapter are focused on the control strategies design and the experimental tests. An off-line technique of actuators electrical centering is explained and its advantages are described in the control design context. This strategy can be summarized as follows. Knowing that: a) each actuation axis is composed by two electromagnets; b) each electromagnet needs a current closed-loop control; c) the bandwidth of this control is depending on the mechanical airgap, then the technique allows to obtain the same value of the closed-loop bandwidth of the current control of both the electromagnets of the same actuation axis. This approach improves performance and gives more steadiness to the control behavior. The decentralized approach of the control strategy allowing the full suspensions on five axes is illustrated from the design steps to the practical implementation on the control unit. Furthermore a selfcentering technique is described and implemented on the experimental test rig: this technique uses a mobile notch filter synchronous with the rotational speed and allows the rotor to spin around its mass center. The actuators are not forced to counteract the unbalance excitation avoiding saturations. Finally, the experimental tests are carried out on the rotor to validate the suspension control, the off-line electrical centering and the selfcentering technique. The numerical and experimental results are superimposed and compared to prove the effectiveness of the modeling approach

A globally exponentially stable position observer for interior permanent magnet synchronous motors

The design of a position observer for the interior permanent magnet synchronous motor is a challenging problem that, in spite of many research efforts, remained open for a long time. In this paper we present the first globally exponentially convergent solution to it, assuming that the saliency is not too large. As expected in all observer tasks, a persistency of excitation condition is imposed. Conditions on the operation of the motor, under which it is verified, are given. In particular, it is shown that at rotor standstill---when the system is not observable---it is possible to inject a probing signal to enforce the persistent excitation condition. {The high performance of the proposed observer, in standstill and high speed regions, is verified by extensive series of test-runs on an experimental setup

Asenkron motorlar için ayarlanabilir gerilim uygulamalı V/f tabanlı hız denetiminde farklı PWM tekniklerinin performans analizi

This paper presents a comparative study and a method to improve Volt-Hertz (V/f) based speed control of Induction Motors (IMs). For this purpose, Sinusoidal Pulse Width Modulation (SPWM) and space vector pulse width modulation (SVPWM) techniques are investigated and evaluated, especially from the point of their control performance on the V/f-based control for three-phase IMs working at different load and speed conditions. From this aspect, it is a different study from the literature. Steady and transient effects of both techniques on the above mentioned control methods are analyzed for several case studies. Afterwards, adjustable boost voltage application with modified reference commands technique is proposed for both PWM methods in order to improve start-up performance. All investigations for both PWM models are carried out under the same conditions. Although SVPWM technique gives more effective results in many cases, the proposed method provides noticeable improvements on SPWM-based applications from point of performance on the control method. As a novelty of this study, it is shown that, the bad performance of the control method at low frequency in SPWM application, which has lower computational burden for low cost microcontroller, can be improved by applying adjustable boost voltage along with modified references that are proportional to the DC bus current

CLOSED-LOOP DYNAMIC RESPONSE OF A STATIC SCHERBIUS DRIVE.

Generalized root-loci techniques, for squirrel-cage motors have been extended to wound-rotor, slip-energy-recovery systems (static Scherbius drive). The influence of a feedback control loop on these root loci is considered. General conclusions on Scherbius drive dynamics, as well as supporting experimental results, are presented

Partitioning And Interface Requirements Between System And Application Control For Power Electronic Converter Systems

Applications of power electronics in power systems are growing very rapidly and changing the power system infrastructure in terms of operation speed and control. Even though applications of power electronics are wide spread, the cost and reliability of power electronics are the issues that could hinder their penetration in the utility and industrial systems. The demand for efficient and reliable converter controllers gave rise to modularized converter and controller design. The objective of this dissertation is to determine the appropriate partitioning and interface requirements between the system and application control layers for power electronic converters so that the minimum set of system layer to application layer control interfaces is compatible across all power electronic controllers. Previous work, using the Open System Architecture (OSA) concept has shown that there is a set of common functions shared by different converters at the low-level control layers. It has also shown that, depending on the application, there is a variation in control functions in application/middle control layers. This functional variation makes it difficult to define system functionality of power converters at upper control layers and further complicates the investigation into the partition requirements of system to application control layer. However, by analyzing the current or voltage affected by a converter in terms of orthogonal components, where each component or group of components is associated with a power-converter application, and the amount of required DC bus energy storage, a common functionality can be observed at the application control layer. Therefore, by establishing common functionality in terms of affected current or voltage components, a flexibility of operation can be realized at upper control layers that will be a major contribution towards standardizing the open system architecture. In order to a construct functional flexible power converter control architecture, the interface requirements to the system control layer and the partitioning between the system control layer and application control layer need to be explored. This will provide flexibility of system design methodology by reducing the number of constraints and enabling system designers to explore possible system architectures much more effectively