Long Stator Linear Motor Normal Force Control
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Solution Overview
Problem
In long-stator linear motors with drive coils arranged on one side, generating a normal force is disadvantageous as it reduces propulsion force and leads to mechanical stress, vibrations, and increased wear due to high frictional forces, necessitating oversized mechanical guides that are costly and complex.
Innovation Solution
A controller determines a normal force-forming current component of the drive current to regulate the resulting normal force, ensuring it meets a predetermined holding force, thereby reducing mechanical stress and improving smooth operation by adjusting the normal force dynamically based on the transport unit's position and operating state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a normal force is generated in long-stator linear motors with drive coils arranged on one side, then the transport unit can be held on the transport route, but the propulsion force is reduced and mechanical stress increases
Solution Approach 1:
The patent applies dynamic control of the normal force by continuously adjusting the d-component of the drive current based on the transport unit's position, speed, and acceleration. This dynamic adjustment ensures the normal force is optimized at each moment to maintain holding while minimizing impact on propulsion force
Solution Approach 2:
The patent changes the parameter of normal force from a static to a dynamically variable quantity. By modifying the d-component of the drive current according to real-time operating conditions, the normal force is adjusted to achieve optimal balance between holding reliability and propulsion efficiency
2Reliability
If high normal force is applied to hold the transport unit securely, then the transport unit remains stable on the transport route, but mechanical stress, vibrations, and wear increase
Solution Approach 1:
The patent implements feedback control by continuously monitoring the transport unit's position, speed, and acceleration, and using this information to adjust the normal force. This closed-loop control ensures the normal force is precisely matched to actual needs, avoiding excessive forces that would cause mechanical stress and wear
Solution Approach 2:
The normal force is dynamically adjusted based on real-time operating conditions rather than maintained at a constant high level. This dynamic approach maintains stability when needed while reducing harmful mechanical effects during normal operation
3Ease of operation
If drive coils are arranged on both sides to generate normal force for centering, then the transport unit is guided in the middle, but the device complexity increases
Solution Approach 1:
The patent extracts the normal force generation function from the mechanical guide structure and transfers it to the electromagnetic field. By using the d-component of the drive current to generate normal force, the system eliminates the need for complex mechanical guides while maintaining effective transport unit centering and guidance
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 reduces mechanical load on guide elements, minimizes running noise, and ensures secure transport unit holding without unnecessary high forces, enhancing the longevity and efficiency of the transport system.
Implementation Method 1
Through the interaction of the (electro)magnetic fields of the drive magnets and the drive coils, a propulsion force acts on the transport unit
Implementation Method 2
Due to the magnetic flux generated by the drive coils, in addition to the propulsion force in the direction of movement of the transport unit, a normal force can also be generated transversely to the direction of movement
Data Source
Figure 1
Figure 2~7
Figure 3~6
AI summary
To reduce the mechanical stress caused by the guidance of the transport unit of a transport device in the form of a long-stator linear motor, and yet to ensure secure mounting of the transport unit on the transport track of the transport device in all operating states, it is provided that the normal force (FNn) acting on the transport unit is controlled by a controller (Rk) for regulating the normal force (FNn), wherein the controller (Rk) determines a normal force-generating current component (iAnd) of the drive current (iAn) of the drive coils (7, 8) interacting with the transport unit (Tn), such that a resultant normal force (FΣNn) acting on the transport unit (Tn) is calculated as the sum of the normal force (FNn), one of the drive magnets (4,5) the magnetic force (FMn) generated in the normal direction (N) and an external force (FEn) acting on the transport unit (Tn) in the normal direction (N) corresponds at least to a predetermined holding force (FNnmin) in the normal direction (N).