Liquid purification or separation – With alarm – indicator – register – recorder – signal or... – Fluid pressure responsive
Reexamination Certificate
1999-07-28
2001-07-31
Ramirez, Nestor (Department: 2834)
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
Fluid pressure responsive
C310S06800R, C218S034000, C218S114000
Reexamination Certificate
active
06267876
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods of controlling the performance of magnetic bearing-supported rotors especially these which are designed to change speeds during operation. High speed rotors are supported by magnetic bearings which require an electronic control system. The control systems of this invention can be used to control rotor displacements and magnetic bearing currents inter alia, at low values. The methods of controlling the magnetic bearing systems of this invention employ mathematical relationships deriving from the rotor-magnetic bearing system. When a rotor operates over a speed range, parameters in the rotor change with time due to such effects as gyroscopics. The rotor-magnetic bearing systems of the invention employ advanced mathematical modeling and controller development to enable the physical hardware to operate in the most desirable manner with low vibration levels and low operating magnetic bearing currents. This invention concerns methods of using a linear parameter varying control system. The present invention also allows the user to implement a small to moderate size control system on a personal computer or workstation size computer for the operation of a high speed rotor-magnetic bearing system over an operating speed range.
BACKGROUND OF THE INVENTION
Historically, high speed rotors supported in magnetic bearings have been employed in applications such as energy storage flywheels, momentum transfer flywheels, pointing devices, and control moment gyroscopes. Typically, rotors in devices such as these are constructed of a relatively massive wheel with high inertia, such as a disk or cylinder, which is attached to a support shaft. The support shaft is driven by a motor, or motor-generator in the case of energy storage flywheels, and is supported by magnetic bearings. In normal operation, the rotor mass has different spin speeds which produces the energy storage, momentum transfer, pointing and control moment functions. Such high speed, magnetically suspended rotor systems are known per se. For example, see U.S. Ser. No. 09/248,520 filed Feb. 2, 1999, incorporated herein by reference.
Thus, this invention provides novel rotor-magnetic bearing control, especially linear parameter varying control systems for high speed rotors. An exemplary application comprising a large inertia energy storage/momentum mechanical flywheel rotor, a motor/generator, a set of magnetic bearings to support the flywheel rotor, a support shaft attached to the flywheel rotor, power amplifiers. It is therefore a primary objective of this invention is to provide improvements in the operation of high speed rotor-magnetic bearing systems using the linear parameter varying control system. The linear parameter varying control method optimizes rotor operation over the entire speed range of the flywheel plant supported on magnetic bearings. The advantages of the invention include the reduction of rotor vibration over the operating speed range of the rotor compared with previous control methods and minimization of coil currents to minimize rotating power losses in the flywheel rotor operational range.
SUMMARY OF THE INVENTION
The present invention provides innovative methods of controlling magnetic bearings, which permits optimum control. Linear parameter varying control methods optimize rotor operation over the entire speed range of the flywheel plant supported on magnetic bearings. Advantages of the invention include the reduction of rotor vibration over the operating speed range of the rotor compared with previous control methods and minimization of coil currents to minimize rotating power losses in the flywheel rotor operational range.
Conventional automatic control systems applied to magnetic bearing in previous applications assume that the plant is invariant with time. This means that the control algorithm is formulated based upon the engineering model of the rotor, bearing, actuator, sensor, and other components of the flywheel system, called the plant, that is time independent. Some of the control algorithms typically employed for time independent control algorithms are proportional-integral-derivative (PID) controls, mu synthesis and H
∞
controls. The control algorithm is then designed to operate for the specific values of the plant which are evaluated for a particular speed.
A number of high speed rotor applications such as high inertia flywheel rotors inherently have large gyroscopic effects. For example, in energy storage flywheel rotors, the energy stored in the flywheel is proportional to the mass of the flywheel, the square of the rotational speed, and the square of the radius of the mass. This means that the most effective energy storage will have most of the mass at the outer edges of the flywheel. In turn, this means that gyroscopic effects are very significant in energy storage/momentum wheels. Gyroscopic forces in energy storage/flywheel rotors (or any rotating mechanical component) are proportional to the operating speed of the rotor. These forces couple the vibration of the rotor along two transverse axes, often denoted x and y, which makes these forces difficult to control with the magnetic bearing control algorithm and maintain a centered rotor operation.
Other rotor properties will also vary with rotor operational speed. The rotor geometry changes due to centrifugal stress and thermal expansion. As the speed increases, centrifugal stresses induce strains in the rotor material generating significant increases in the rotor diameter and other dimensions. As the rotor speed increases, heat generation will increase and the rotor will run at higher temperatures. Thermal expansion of the rotor material creates additional changes in rotor geometry.
An energy storage/momentum flywheel must have the capability to accelerate and decelerate at a certain rate in order to have to capability to attain the desired energy storage or production and/or the desired changes in momentum. As the flywheel rotor accelerates or decelerates, the rotor properties change compared to conventional constant speed rotor models.
REFERENCES:
patent: 5084643 (1992-01-01), Chen
patent: 5347190 (1994-09-01), Lewis et al.
patent: 5732636 (1998-03-01), Wang et al.
patent: 5736800 (1998-04-01), Iannello et al.
patent: 5767597 (1998-06-01), Gondhalekar
patent: 6005315 (1999-12-01), Chapman
Allaire Paul E.
Bartlett Robert O.
Tsiotras Panagoitis
Lam Thanh
Ramirez Nestor
Trinity Flywheel Power
Woodcock Washburn Kurtz Mackiewcz & Norris LLP
LandOfFree
Control of magnetic bearing-supported rotors does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control of magnetic bearing-supported rotors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control of magnetic bearing-supported rotors will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552516