MIMO PID Control of Rotors with Electromagnetic Bearings.pdf (original) (raw)

IMPROVEMENT OF FLEXIBLE ROTOR/ACTIVE MAGNETIC BEARINGS SYSTEM PERFORMANCE USING PI-D CONTROL

Proportional-integral-derivative (PID) control is the most common control approach used to control active magnetic bearings system, especially in the case of supporting rigid rotors. In the case of flexible rotor support, the most common control is again PID control in combination with notch filters. Other control approaches, known as modern control theory, are still in development process and cannot be commonly found in real life industrial application. Right now, they are mostly used in research applications. In comparison to PID control, PI-D control implies that derivate element is in feedback loop instead in main branch of the system. In this paper, performances of flexible rotor/active magnetic bearing system were investigated in the case of PID and PI-D control, both in combination with notch filters. The performances of the system were analysed using an analysis in time domain by observing system response to step input and in frequency domain by observing a frequency response of sensitivity function.

Design and performance assessment criteria for controllers applied to magnetic bearings

Electrodynamic and Mechatronic Systems, 2011

Active Magnetic Bearings, due to a plant-intrinsic instability, require a control system for normal operation. Many control strategies have been proposed for the stabilization task, in some instances emphasizing market recognized control approaches, as PID controllers arranged in decentralized structures, and in other instances modern control approaches are envisaged, like LQR or H∞ structures. The objective of this paper is to present criteria to assess the performance of such proposed controllers, in order to establish a metric to compare different control schemes. The performance assessment criteria discussed include time domain as well as frequency domain approaches. Such criteria are applied to two control systems used in a laboratory prototype to stabilize a bearingless motor, being one based on PID controllers and the other being a LQR scheme. Discussion of the results is used to select a metric to be applied in the comparison of some controller algorithms, both centralized and decoupled, in order to determine which control law best suits such a bearingless motor.

A Control Model of Active Magnetic Bearings

Active magnetic bearings (AMBs) support a rotating shaft, inside a stator, contactless. Their major benefit in respect to hydrodynamic journal bearings is the possibility of operating in much higher rotational speeds (above 20.000 RPM). This is due to the fact that, their angular velocity is only limited by the strength of the shaft material and always they have stabilized operation without any mechanic contact. Also, AMBs are resulting in long life time, without the use of any lubrication system, eliminating thus the complexity of the lubricant network and promoting green operation of the rotating machines. Furthermore, the electromagnetic bearings are active elements that allow the measurement and the control of the position of the shaft, targeting in most accurate equilibrium positions, in terms of the shaft operation. Therefore, a suitable control system is required for a magnetic bearing, to exploit the above advantageous operational characteristics.

Robust control of rotor/active magnetic bearings

In this paper we design, analyze and compare the performance of various stabilizing robust controllers for the model of a horizontal rotor with active magnetic bearings. Rotors suspended with electromagnetic bearings are inherently unstable; therefore, feedback control is an essential part of their operation. Despite the nonlinear form of the actuator (electromagnetic bearing) dynamics, plant (rotor) model is linear and time-invariant at constant rotor speed. Actuator dynamics are linearized around an operating point using a constant bias current. Two H 1 controllers are designed for the nominal system using different structures. The uncertainties in the system dynamics due to changes in the model parameters are two-fold: gyroscopic forces due to different rotor speeds within the range of operation, and the changing spring stiffness of the electromagnetic bearings due to different conditions during the operation. To ensure robust stability of the closedloop system for all possible values of parameters that can change during the operation, an H 1 controller based on the model incorporating uncertainty in the system is designed. The limits for the allowable parameter changes for robust stability are tested and established with -analysis.

2004 IEEE ICS Fuzzy logic based control of rotor motion in active magnetic bearings

Active magnetic bearings (AMB) are increasingly being used as an alternative to rolling element and fluid-film bearings in rotating machinery application. Stablc opcration of AMB can only be achievcd via feedback control of which the most widcly used controllers are of thc linear PID type. Undcr extreme conditions, however, the dynamic responsc of the rotor in AMB bccomes highly nonlinear. As a result, the linear controllers are no longer capable of suppressing or controlling the bifurcations of the rotor response. In order to suppress the non-linearity in AMB, a nonlinear control strategy is required. One of such strategies is the use of fuzzy logic based control approach. This paper aims to investigate and analyze the dynamical response of rotors in active magnetic bearings in AMB and presents the dcvclopmcnt and implemcntation of a fuzzy logic control strategy for suppressing the nonsynchronous response in AMB. This control strategy is expected to stabilize the rotor-bearing system or to delay its onset of instability. Through modcling and simulation of the non-linear rotor response. i t i s found that for certain operating parameters, the rotor in AMB exhibits non-synchronous response (quasi-periodic or chaotic).

Decentralized PI/PD position control for active magnetic bearings

Electrical Engineering, 2006

This paper discusses a closed-loop decentralized control for active magnetic bearings. A cascade connection of PI and PD position controllers is proposed. The control design is based on a simplified linearized model for one axis using a root locus. An excellent agreement is noticeable between simulation and experimental results. It has been shown, that the presented PI/PD control guarantees satisfactory high damping and stiffness of the overall system.

A fractional order PID control strategy in active magnetic bearing systems

Alexandria Engineering Journal, 2018

Active Magnetic Bearings (AMBs) are broadly utilized for high angular speed machines such as turbo-machinery, compressors and high speed motors. In AMBs, the rotating parts run without physical contacts with the moving parts. This reduces maintenance costs and minimizes friction. Generally, the applied loads cause extra gyroscopic effects on the rotating parts especially under high-speed operation. Although conventional PID controllers are widely employed in these systems, they experience some stability problems under high dynamic operations. In this paper, the design of an active magnetic bearing system based on fractional order PID (FOPID) controllers to enhance system dynamics and stability is introduced. The suggested controller gains are optimized utilizing particle swarm optimization (PSO) approach. An ordinary AMB system framework with four radial bearings is used to assess the suggested FOPID controller against routine PID controllers. The system current limitation, overshoot constraint, and time specifications requirements are deemed in the optimization technique.