Absolute Position Sensing Using Magnetic Pole and Field Angle Sensors
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Solution Overview
Problem
Existing position sensing systems for moveable assemblies, such as in machine tools and active suspension systems, face challenges in accurately determining the position of moveable components over a travel distance, particularly in environments with random accelerations, where precise and continuous sensing of magnetic fields is required.
Innovation Solution
A position sensing system comprising a linear motor with a stator and armature, where a first magnetic device with magnetization state transition locations and a second magnetic device creating a cyclically-varying magnetic field are used in conjunction with magnetic pole and field angle sensors to provide continuous and absolute position feedback, allowing for precise control of the armature's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single type of position sensor is used, then the device complexity is reduced, but the measurement precision and reliability of position sensing is insufficient
Solution Approach 1:
The patent combines two different sensing systems (magnetic pole sensor and magnetic field angle sensor) into a single integrated position sensing system. The magnetic pole sensor provides absolute position information while the magnetic field angle sensor provides incremental position information, and their outputs are merged to achieve both high measurement precision and full travel distance coverage without requiring separate sensor systems
2Adaptability or versatility
If the sensing range is extended to cover the full travel distance, then the adaptability is improved, but the measurement precision may be compromised
Solution Approach 1:
The patent divides the sensing function into two segments: the magnetic pole sensor segment that provides absolute position reference over the full travel distance, and the magnetic field angle sensor segment that provides high-resolution incremental position measurements. Each sensor segment is optimized for its specific function, allowing the overall system to achieve both full travel distance coverage and high measurement precision
3Reliability
If environmental disturbances such as random accelerations are present, then the reliability of position sensing deteriorates, but the system must maintain precise control
Solution Approach 1:
The patent implements a feedback mechanism where the outputs of both the magnetic pole sensor and magnetic field angle sensor are continuously monitored and combined. The magnetic pole sensor provides absolute position feedback that corrects drift and errors caused by environmental disturbances, while the magnetic field angle sensor provides continuous incremental feedback for precise position tracking, together maintaining reliable position sensing under random accelerations
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
The system enables accurate and continuous sensing of the armature's position, enabling effective control of the assembly's movement, even in systems subject to random accelerations, by using a combination of absolute and incremental position sensors to determine the absolute position and track cycles, thereby enhancing the precision and reliability of position control.
Implementation Method 1
A magnetic pole sensor is coupled to the stator adjacent the first magnetic device such that the first magnetic device moves past the magnetic pole sensor... the magnetic pole sensor sensing the adjacent poles of the first magnetic device
Implementation Method 2
A second magnetic device is coupled to the armature, the second magnetic device defining a sensing surface that comprises a plurality of adjacent alternating opposite magnetic poles that create a cyclically-varying magnetic field proximate its sensing surface
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
To determine the relative position of movable portions of an assembly, a first magnetic device is coupled to a first portion of the assembly. The first magnetic device has a sensing surface with a number of magnetic poles that provide a magnetization state transition location. An absolute position sensor with a two-state output is coupled to the assembly adjacent the first magnetic device. The output state changes when a magnetization state transition of the first magnetic device moves past the absolute position sensor. A second magnetic device is coupled to the assembly. The second magnetic device creates a cyclically-varying magnetic field proximate its sensing surface. An incremental position sensor is coupled to the assembly adjacent the second magnetic device, and has an output that varies continuously relative to magnetic field angle over at least a portion of one cycle of the cyclically-varying magnetic field of the second magnetic device.