Linear Electric Machine Commutation for Smooth Force Output
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Solution Overview
Problem
Existing linear electric machines (LEMs) face challenges in generating smooth and linear force responses over a wide range of motion without mechanical impedance, especially when unpowered, and often require complex force sensors and closed-loop control systems, which increase cost and complexity.
Innovation Solution
A LEM design that combines specific geometries of motor windings and permanent magnets with advanced characterization and commutation techniques to produce smooth, linear force responses through magnetic interaction alone, eliminating the need for force sensors and reducing system complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If closely spaced alternating permanent magnets are used to generate magnetic fields, then the magnetic field strength is improved, but the force ripple (cogging) increases and the magnetic field changes sharply
Solution Approach 1:
The patent employs sinusoidal geometries for both the permanent magnets and windings, replacing the sharp transitions of closely spaced alternating magnets with smooth curved field distributions. This curvature approach maintains strong magnetic fields while eliminating the abrupt field changes that cause cogging and force ripple.
Solution Approach 2:
The patent transforms the magnetic field distribution from a stepped, discontinuous pattern (characteristic of closely spaced alternating magnets) to a continuous sinusoidal pattern. This parameter change in field distribution smooths the magnetic interaction, reducing force ripple while maintaining field strength through optimized sinusoidal geometry.
2Length of moving object
If mechanical couplings (screw drives) are used to convert rotary motion to linear motion, then the range of motion is improved, but the mechanical impedance and wear increase
Solution Approach 1:
The patent replaces mechanical coupling systems (screw drives, gears) with a direct linear magnetic interaction system. The linear motor structure uses magnetic fields directly to produce linear force without mechanical transmission elements, eliminating mechanical impedance, wear, and complexity while maintaining full range of motion capability.
Solution Approach 2:
The patent extracts and removes the mechanical coupling components (screw drives, nuts, shafts) from the system, retaining only the essential magnetic interaction elements. This extraction eliminates the harmful mechanical impedance and wear while preserving the force generation and motion capabilities through direct linear magnetic actuation.
3Measurement precision
If force sensors and closed-loop control systems are added to control force output, then the force control precision is improved, but the system complexity and cost increase
Solution Approach 1:
The patent enables the linear motor to inherently produce smooth, linear force responses through its sinusoidal geometry design, eliminating the need for external force sensors and complex closed-loop control systems. The system serves itself by designing the magnetic field geometry to naturally deliver the desired force characteristics without requiring measurement and correction mechanisms.
Solution Approach 2:
The patent converts the potential harm of complex control systems into a benefit by designing the magnetic geometry to inherently produce the desired smooth force output. The sinusoidal arrangement of magnets and windings transforms what would require complex active control into a passive, inherent system characteristic, reducing complexity while maintaining force precision.
4Adaptability or versatility
If multiple phases with alternating permanent magnet arrays are used, then the commutation capability is improved, but the construction complexity and assembly difficulty increase
Solution Approach 1:
The patent employs sinusoidal geometries for permanent magnets and windings that naturally facilitate smooth commutation across multiple phases. The curved, sinusoidal field distribution simplifies the magnetic interaction patterns, making commutation more straightforward and reducing assembly precision requirements compared to traditional alternating magnet arrays.
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 precise control of forces and maintains lower system complexity and cost by using sinusoid-like shaft field functions and phase commutation methods to achieve linear force outputs across the range of travel without mechanical impedance.
Implementation Method 1
These devices typically accelerate faster than screw-drive systems... generate forces through magnetic interaction alone
Implementation Method 2
Methods and apparatus for linear electric machine... effectively converts mechanical energy to electrical energy, and effectively converts electrical energy to mechanical energy
Implementation Method 3
effectively converts mechanical energy to electrical energy, and effectively converts electrical energy to mechanical energy
Data Source
AI summary
An embodiment of a linear electric machine includes two or more phases that define a central bore, and alternating permanent magnets that are disposed within the central bore and are free to move relative the windings. An embodiment of a method for selectively powering the windings is disclosed that enables the machine to realize a commanded force, or to determine the force present by using the current within the windings and the alignment of the magnets relative to the windings.