Variable Reluctance Motor Commutation Mapping for Torque Ripple Control
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Solution Overview
Problem
Variable reluctance motors face challenges in precision control due to high torque ripple and non-linear relationships between phase current, rotor position, and geometry, requiring accurate commutation models that are difficult to achieve, especially with changing motor coil inductances.
Innovation Solution
An optimal commutation scheme is developed that accounts for mutual inductance effects by empirically characterizing current, position, and torque relationships using an iso-torque value generation station, creating tables that map phase currents to torque and position, allowing for reduced torque ripple and improved control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If variable reluctance motors are used as a cost effective alternative to brushless direct current motors, then manufacturing cost is reduced, but precision control becomes challenging due to high torque ripple and non-linear relationships
Solution Approach 1:
The patent transforms the non-linear torque-current-position relationship into a manageable form by pre-computing commutation tables that map desired torque and rotor position to required phase currents. This parameter transformation allows standard variable reluctance motors to achieve precision control without requiring complex real-time non-linear calculations, resolving the contradiction between cost-effectiveness and control precision.
2Device complexity
If conventional feedback loops designed for fixed inductance are used, then control simplicity is maintained, but performance deteriorates due to changing motor coil inductances in variable reluctance motors
Solution Approach 1:
The patent pre-computes commutation tables that account for varying inductance effects across different rotor positions and torque levels. By performing this calculation in advance rather than in real-time during motor operation, the system maintains simple control hardware while achieving reliable performance that adapts to changing inductance conditions.
3Ease of manufacture
If variable reluctance motors are used in robot servo applications, then cost effectiveness is improved, but dynamic response becomes slower requiring adjustments to commutation strategy
Solution Approach 1:
The patent implements a dynamic commutation strategy where the controller uses pre-computed tables to rapidly determine optimal phase currents based on real-time rotor position and desired torque. This allows the system to adapt commutation parameters dynamically to maximize response speed while maintaining the cost advantages of variable reluctance motors.
4Manufacturing precision
If accurate commutation models are developed to reduce torque ripple, then control precision is improved, but model complexity and dependency increase
Solution Approach 1:
The patent creates simplified commutation tables that capture the essential torque-current-position relationships without requiring complex analytical models. By pre-computing these tables from motor characteristics and storing them in lookup format, the system achieves high control precision while avoiding the complexity of real-time model calculations and reducing dependency on accurate analytical commutation models.
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 minimizes torque ripple and enhances control precision by providing a method to compute currents in each motor phase, reducing dependency on accurate commutation models and improving motor responsiveness.
Implementation Method 1
a phase coil associated with each of the at least one stator pole, the phase coil being configured to establish a flux in a magnetic circuit between the rotor and stator
Implementation Method 2
Variable reluctance motors do not require magnets and their mechanical construction is simple however, the usage of variable reluctance motors for precision control remains challenging
Data Source
AI summary
A variable reluctance motor load mapping apparatus includes a frame, an interface disposed on the frame configured for mounting a variable reluctance motor, a static load cell mounted to the frame and coupled to the variable reluctance motor, and a controller communicably coupled to the static load cell and the variable reluctance motor, the controller being configured to select at least one motor phase of the variable reluctance motor, energize the at least one motor phase, and receive motor operational data from at least the static load cell for mapping and generating an array of motor operational data look up tables.