Linear Motor Position Sensing Without Reference Travel
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Solution Overview
Problem
Existing methods for determining the position of a movable component relative to a stationary component in linear motors, especially when switched on, are inadequate for large range of movement or multiple rotors, as they require reference travel or close positioning of sensors, which is impractical and unreliable.
Innovation Solution
A method using a sensor model to compare measured sensor responses with expected responses while varying the assumed position of the movable component, allowing for reliable position determination even when components are closely or completely adjacent, by determining the sensor model once and using it for each position sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference travel is used to determine position when linear motor is switched on, then position can be determined, but this is unsuitable for large range of movement or long stator linear motors with large number of rotors
Solution Approach 1:
The patent applies preliminary action by pre-determining the sensor model offline before actual operation. The sensor model is created by moving the movable component through its entire range of movement and storing the sensor responses at various positions. This allows immediate position determination upon switching on without requiring reference travel, resolving the contradiction between position determination capability and operational simplicity for large range applications.
2Measurement precision
If position sensors are arranged closely together to determine absolute position, then position can be determined without reference travel, but this increases device complexity and is impractical for large range of movement
Solution Approach 1:
The patent uses copying by creating a virtual model (sensor model) of the sensor responses across the entire range of movement. Instead of physically arranging sensors closely together, the system copies the sensor response characteristics into a pre-stored model that can be queried for any position. This eliminates the need for dense physical sensor arrangements while maintaining absolute position determination capability.
3Measurement precision
If additional position magnets are added to determine position without reference travel, then position determination is improved, but this increases device complexity
Solution Approach 1:
The patent applies universality by making the existing position magnets serve dual purposes: both for generating propulsive force in the linear motor and for position determination. The sensor model is trained to recognize the magnetic field patterns of these multi-functional magnets, eliminating the need for separate position magnets while maintaining position determination accuracy.
4Reliability
If sensor model is determined for each position sensor, then position determination is robust, but this increases computational load
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the sensor model responses during an offline training phase. The computationally intensive model determination is performed beforehand, and only lightweight model querying and comparison operations are required during actual operation. This shifts the computational burden from runtime to setup time, maintaining robustness while reducing operational energy consumption.
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
Enables robust and reliable position determination of movable components relative to stationary components, recognizing multiple components and their positions without the need for additional position magnets or closely spaced sensors, suitable for large range of movement or multiple rotors.
Implementation Method 1
a position sensor detects a magnetic field of a position magnet in the region of this position sensor in the form of a sensor response
Data Source
AI summary
For determination of the position of a movable component with a plurality of position magnets relative to a stationary component with a plurality of position sensors, it is provided that the sensor responses are detected for a group of position sensors in the region of the movable component, sensor model responses of the group of position sensors are determined from a sensor model for a plurality of assumed different relative positions of the movable component relative to the stationary component, the sensor model responses are compared with the sensor responses and the assumed relative position with the smallest deviation between the sensor model responses and the sensor responses is used as the relative position of the movable component.