Linear Motor Position Correction for Distributed Stator Speed Variation
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Solution Overview
Problem
In linear motors with distributed stator arrangements, the movable member experiences speed variations due to inadequate control over its position, particularly when transitioning between stators, leading to inefficient movement.
Innovation Solution
A driving system with a movable member equipped with magnets and a scale, and multiple stators each having coils and position sensors, where the distance between adjacent stators and sensors is optimized to allow for precise position control through position and speed calculations, ensuring continuous thrust and minimizing speed variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stators are arranged in a distributed manner to reduce facility cost, then the conveying system becomes more cost-effective, but speed variation occurs due to inadequate position control when transitioning between stators
Solution Approach 1:
The system performs preliminary position correction calculations before the movable member enters a stator's control area. The back-calculating unit computes the deviation and corrects position data in advance, ensuring smooth transition between distributed stators without speed variation. This preliminary action prevents the harmful effect of speed fluctuation while maintaining the cost-effective distributed stator arrangement.
2Measurement precision
If the movable member is accelerated and decelerated in the region opposed to the stator, then position control is achieved, but unnecessary speed variation occurs due to repeated acceleration and deceleration cycles
Solution Approach 1:
The system uses feedback from position sensors to continuously monitor the movable member's position and provides this information to the back-calculating unit. The feedback loop enables real-time calculation of position deviation and generates appropriate correction commands, achieving precise position control without unnecessary speed variation through intelligent feedback-based control rather than brute-force acceleration/deceleration cycles.
3Speed
If the distance between adjacent stators is reduced to enable continuous control, then speed variation is minimized, but the facility cost increases
Solution Approach 1:
The back-calculating unit acts as an intermediary between distributed stators, computing position corrections that bridge the gaps between stators. This intermediary calculation system enables effective continuous control despite physical discontinuities in the distributed stator arrangement, achieving smooth speed control without requiring reduced distances between stators, thereby maintaining cost-effectiveness.
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 configuration enables smooth and controlled movement of the movable member by preventing unnecessary speed variations, ensuring consistent performance across multiple stators.
Implementation Method 1
a linear motor including a movable member (20) and stators (10A, 10B, 10C)... each of the stators (10A, 10B, 10C) including a coil (11)
Implementation Method 2
a position sensor for detecting, from the scale portion, a position of the movable member
Data Source
AI summary
In a linear motor, a driving device calculates a deviation between a position command from a controller and a position detected by a position sensor, a position controlling is performed calculating speed command to be utilized for speed controlling of the movable member based on the deviation and a position gain, a deviation is calculated at a time when the movable member enters a control area in which at least a part of the magnet portion opposes to the coil of the stator within an area of which position is detected by the position sensor, and the position of the movable member is back-calculated from deviation from the position command and the position command, and the position detected by the position sensor is corrected with the calculated position being as the position of the movable member at a time when the movable member enters the control area.