Linear Motor Levitation Control via Inductive Gap Sensing
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Solution Overview
Problem
Linear motors used in conveyors, trains, and elevators face challenges in maintaining a stable air gap between the mover and stator parts, leading to potential system imbalance and damage due to the lack of effective and affordable levitation control methods, particularly in multicar systems where traditional guidance systems are costly or difficult to install.
Innovation Solution
A method utilizing an oscillating circuit with a sensing coil arranged in a fixed spatial correlation to the linear motor's mover part, receiving response signals to determine gap length, and controlling the levitation unit to maintain a predetermined gap length, employing affordable components like air core coils and inductance-to-digital converters for precise and responsive levitation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sliding guides or roller guides or magnetic guides are used to keep the mover part in track, then the system stability is improved, but the device complexity and manufacturing cost increase due to considerable efforts in materials and tolerance control
Solution Approach 1:
The patent replaces mechanical guidance systems (sliding guides, roller guides) with a magnetic field-based sensing and control system. The sensing coil detects air gap variations through electromagnetic induction, and the control system adjusts the magnetic forces to maintain stability, eliminating the need for complex mechanical alignment and tolerance control.
Solution Approach 2:
The patent introduces an intermediary sensing coil and control system between the mover and stator. This intermediary detects air gap variations and mediates the control of magnetic forces, providing stability without requiring direct mechanical contact or complex mechanical guidance structures.
2Measurement precision
If optical laser is used for gap length control, then the measurement precision is improved, but the device cost increases significantly
Solution Approach 1:
The patent replaces expensive optical laser systems with affordable inductive sensing coils and standard electronic components. The sensing coil provides sufficient measurement precision for gap length control at a fraction of the cost of laser-based systems, making the solution economically viable for commercial applications.
Solution Approach 2:
The patent substitutes optical measurement systems with electromagnetic induction-based sensing. The sensing coil measures air gap variations through changes in inductance caused by the magnetic properties of the stator teeth, providing a cost-effective alternative to optical laser measurement.
3Loss of information
If magnetic tape is installed for linear encoder, then the position information is obtained, but the installation time and complexity increase
Solution Approach 1:
The patent makes the stator teeth structure serve dual purposes: as part of the motor's functional structure and as the reference structure for position sensing. The sensing coil detects the position of stator teeth, eliminating the need for separate magnetic tapes or encoder installations, thereby reducing installation time and complexity.
Solution Approach 2:
The patent gives the stator teeth multiple functions: they serve as both the magnetic interaction structure for motor operation and as the position reference structure for the sensing coil. This multi-functionality eliminates the need for separate positioning components and simplifies the overall system.
4Ease of operation
If the air gap is not precisely controlled, then the system is simpler to operate, but the reliability decreases due to potential system imbalance and damage
Solution Approach 1:
The patent implements a feedback control system where the sensing coil continuously detects air gap variations, and the control system adjusts the magnetic forces in response to these detections. This automatic feedback maintains precise air gap control without requiring manual intervention, ensuring both ease of operation and system reliability.
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
This approach enables reliable and highly responsive levitation control, ensuring the air gap is maintained within a predetermined range, reducing the risk of system imbalance and damage, while being cost-effective and suitable for elevator systems, with the ability to detect position, velocity, and acceleration of the mover part.
Implementation Method 1
supplying an alternating current or alternating voltage to at least one oscillating circuit comprising at least one sensing coil being or assumed to be arranged in a fixed spatial correlation to a mover part of the linear motor such that an opening plane of the sensing coil faces a sensor counter-surface of a stator part of the linear motor with a gap therebetween; receiving a response signal from the oscillating circuit; determining a gap length of the gap based on the response signal
Implementation Method 2
the mover part may comprise four linear motor units which form two opposite levitation pairs around the stator rail, and during a movement both levitation pairs are controlled so that the stator rail stays in the middle of the mover without making contact
Implementation Method 3
A linear motor comprises a stator part and a mover part. A stator part may comprise a toothed stator rail, and the mover part may comprise a number of motor units each having an arrangement of poles, permanent magnets, and electric coils controlled to generate a magnetic flux cooperating with the teeth of the stator rail, for generating a desired linear movement of the mover part with respect to the stator part
Data Source
AI summary
A method for levitation control of a linear motor includes supplying an alternating current or alternating voltage to at least one oscillating circuit including at least one sensing coil being or assumed to be arranged in a fixed spatial correlation to a mover part of the linear motor such that an opening plane of the sensing coil faces a sensor counter-surface of a stator part of the linear motor with a gap therebetween; receiving a response signal from the oscillating circuit; determining a gap length of the gap based on the response signal; and controlling the gap length by driving a magnetic levitation unit of the linear motor based on the determined gap length. An inductive sensing device and an elevator system, and a method for determining a position of the linear motor are also disclosed.