Bearingless Motor Tilt Control Using Filtered Displacement Feedback
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Solution Overview
Problem
The stability of the rotor in the tilt direction is vulnerable to disturbances and oscillations due to interference between radial and tilting movements, leading to potential destabilization and oscillation amplification at critical velocities.
Innovation Solution
A bearingless motor with a two-axis control type that includes a rotor, stator, first and second displacement sensors, a computing unit, and a tilt-directional position controller, which computes and removes unwanted frequency bands to stabilize the rotor by superimposing magnetic fluxes and using current commands to damp oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the rotor is passively stabilized using attractive force between permanent magnet and iron core, then the structure is simpler without active control, but the stability in tilt direction is lower and oscillation cannot be damped
Solution Approach 1:
The patent combines passive stabilization structure with active control system into an integrated bearingless motor. The magnetic bearing system provides both passive restoring torque through magnetic attraction and active damping control through controlled magnetic flux adjustment, merging the simplicity of passive structures with the stability of active control.
Solution Approach 2:
The patent implements feedback control by detecting rotor position and tilt angle, then adjusting the magnetic flux distribution to generate damping forces. The control system continuously monitors the rotor state and modifies the magnetic field to counteract oscillations, providing active stabilization in the tilt direction.
2Force
If the support force line of action does not pass through rotor center of gravity, then torque for tilt control is generated, but oscillation in tilt direction cannot be sufficiently damped
Solution Approach 1:
The patent applies preliminary damping action by pre-positioning the support force line of action to generate restoring torque, and then adding active damping control to counteract oscillations before they grow. The control system proactively adjusts magnetic flux to provide damping forces that prevent oscillation amplification.
Solution Approach 2:
The patent creates a composite control strategy combining passive magnetic restoring forces with active electromagnetic damping forces. The magnetic bearing system integrates both torque generation and oscillation damping functions through composite control of permanent magnets and electromagnetic coils.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves stability of the rotor in the tilt direction by effectively damping oscillations and maintaining stable suspension even under disturbances or critical velocities.
Implementation Method 1
a motor winding for generating a magnetic flux having p poles to produce the torque, and a support winding for generating a magnetic flux having p±2 poles or two poles to produce the support force
Implementation Method 2
The rotor is passively stabilized by using attractive force between the permanent magnet of the rotor and the iron core of the stator
Implementation Method 3
a tilt-directional position controller that receives the displacement in the tilt direction obtained by the computing unit, removes at least part of a band not including a natural angular frequency of tilting of the rotor, and outputs a current command
Data Source
AI summary
A bearingless motor includes a rotor, a stator for applying support force and torque to the rotor, and a first displacement sensor and a second displacement sensor for detecting a radial position of the rotor. The stator includes a motor winding for generating a magnetic flux having p poles to produce the torque, and a support winding for generating a magnetic flux having p±2 poles or two poles to produce the support force. The first displacement sensor and the second displacement sensor are disposed at positions axially different from each other.