Linear Motor Absolute Position Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Tubular linear motors face challenges in achieving absolute position detection of the rotor relative to the stator without initialization or homing, and existing solutions often require complex external components that compromise the compact and integrated design.
Innovation Solution
A non-contact position detection system using internal and external magnetic field sensors arranged within the stator and tubular extension, respectively, to generate signals for absolute position determination, allowing for compact design and eliminating the need for initialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external magnetic field sensors are used for absolute position detection, then position detection capability is improved, but device complexity and volume increase
Solution Approach 1:
The patent combines internal magnetic field sensors (within stator) and external magnetic field sensors (on tubular extension) into a unified position detection system. The internal sensors detect magnetic fields from permanent magnets on the rotor, while external sensors detect magnetic fields from the stator, and both sets of signals are processed together by evaluation electronics to determine absolute rotor position without requiring initialization or homing sequences.
Solution Approach 2:
The magnetic field sensors serve dual purposes: they detect the periodic magnetic field for position determination while also being part of the motor's electromagnetic structure. The same permanent magnets that generate motor force also serve as information carriers for position detection, eliminating the need for separate information carriers or complex external sensor systems.
2Measurement precision
If initialization or homing is required for position detection, then measurement accuracy is improved, but loss of time and productivity worsen
Solution Approach 1:
The system performs preliminary configuration during manufacturing by writing a unique identification code to the evaluation electronics that corresponds to the physical arrangement of magnetic poles. This preliminary action enables the system to immediately determine absolute position upon startup without requiring runtime initialization or homing sequences, as the evaluation electronics can directly interpret sensor signals using the pre-stored reference data.
3Ease of manufacture
If discrete permanent magnets are used for magnetic excitation, then manufacturing flexibility is improved, but manufacturing precision and assembly complexity worsen
Solution Approach 1:
The system uses the actual magnetic field generated by the discrete permanent magnets as the information carrier for position detection, rather than requiring precise mechanical alignment or additional alignment features. The evaluation electronics measure the actual magnetic field strength and phase at each sensor location and use this measured data to determine position, making the system self-adapting to the specific magnetic field configuration regardless of manufacturing tolerances in magnet placement.
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 absolute position detection of the rotor relative to the stator without initialization, maintaining a compact and integrated design while avoiding the need for additional complex components, thus enhancing the motor's precision and usability.
Implementation Method 1
The internal and external magnetic field sensors are designed to detect the periodic permanent magnetic field of the rotor at the location of the respective magnetic field sensor and to generate signals which correspond to the periodic permanent magnetic field detected in each case
Implementation Method 2
The permanent magnetic excitation is usually generated by discrete permanent magnets that are arranged in such a way that a longitudinally periodic magnetic field with alternating north and south poles is created
Implementation Method 3
The force for driving the rotor is typically generated by one of the two components, stator and rotor, having permanent magnetic excitation and the other component being provided with current-capable windings which are supplied with current
Data Source
Figure 1~5
Figure 2a~2b
Figure 3
AI summary
In a linear motor with a stator (1) having a longitudinal axis (16) and a rotor (2) movable relative to the stator (1) in the direction of the longitudinal axis (16) between two end positions, either the stator (1) or the rotor (2) has currentable electrical windings (12) and the rotor (2) or the stator (1) is excited by a permanent magnetic field periodic in the direction of the longitudinal axis (16). The linear motor further comprises a position sensing system (100; 200; 300; 400; 500) for sensing the position of the rotor (2) relative to the stator (1). The position detection system (100; 200; 300; 400; 500) is a non-contact position detection system designed to generate a signal corresponding to the distance between a reference point (11a; 15a) on the stator (1) and a reference point (24a) on the rotor (2).