AC Motor Torque Control via Magnetic State Calculation
Solution Overview
Problem
Existing training devices with electric motors for muscle training lack accuracy, complexity, and safety, particularly in high torque ranges and low speeds, due to reliance on multiple sensors and complex control loops, which can lead to stiffness and safety issues.
Innovation Solution
A training apparatus with an AC motor and frequency converter that measures voltage and current to calculate the magnetic state, using a control unit to generate reference torque and flux for direct torque control, incorporating a hybrid controller and cascade control arrangement for precise torque control and safety features, eliminating the need for multiple sensors and reducing stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors and complex control loops are used to measure speed and torque, then measurement precision is improved, but device complexity increases and reliability decreases
Solution Approach 1:
The patent extracts the torque measurement function from separate force sensors and integrates it into the frequency converter by calculating torque from voltage and current measurements of the AC motor. This eliminates the need for separate torque sensors and simplifies the control system while maintaining measurement precision.
Solution Approach 2:
The frequency converter is designed to perform multiple functions: it controls motor speed, measures voltage and current, calculates magnetic state, and determines torque output. This multi-functionality eliminates the need for separate dedicated sensors for each parameter, reducing device complexity while maintaining measurement capabilities.
2Manufacturing precision
If field-oriented control with angle-of-rotation sensor is used, then torque control precision is improved, but device complexity increases due to multiple-turn detection requirements
Solution Approach 1:
The patent removes the angle-of-rotation sensor from the system and extracts the torque control capability by directly measuring voltage and current. This eliminates the complexity of multiple-turn detection while maintaining precise torque control through magnetic state calculation.
Solution Approach 2:
The patent replaces the mechanical angle-of-rotation sensor system with an electrical measurement system that calculates torque from voltage and current. This substitution eliminates mechanical sensors and their associated complexity while achieving the same torque control precision.
3Speed
If reference flux is used as exclusive control value for fast torque response, then response speed is improved, but manufacturing precision decreases due to insufficient torque dosing accuracy
Solution Approach 1:
The patent segments the torque control into two independent components: flux control for achieving fast response and torque control for ensuring precise dosing. By calculating both reference flux and reference torque separately and using them together, the system achieves both fast response and precise torque dosing without compromise.
4Speed
If high magnetization is used to achieve fast torque response, then response speed is improved, but harmful factors increase due to high stiffness and negative effects in braking mode
Solution Approach 1:
The patent implements dynamic adjustment of reference flux based on the actual torque demand and operating quadrant. By adapting the flux level to the specific operating conditions rather than maintaining high magnetization continuously, the system achieves fast response when needed while avoiding excessive stiffness and harmful effects during braking or low-torque operations.
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
The solution provides quick and precise torque response, improved safety, and reduced energy consumption, allowing for convection cooling and minimizing noise, while ensuring accurate and responsive training resistance across a wide range of torques.
Implementation Method 1
the frequency converter comprises measuring means being arranged to measure a voltage and a current of the AC motor and calculation means being arranged to calculate a magnetic state of the AC motor using the measured voltage, the measured current
Data Source
AI summary
A training apparatus including a training element for a user performing exercises, an AC motor and a frequency converter being arranged to control the AC motor, wherein the frequency converter comprises measuring means being arranged to measure a voltage and a current of the AC motor and calculation means being arranged to calculate a magnetic state of the AC motor using the measured voltage, the measured current, a reference torque and a reference flux in order to generate a torque of the AC motor. The training apparatus further comprises a control unit having a machine control module being arranged to calculate the reference flux and the reference torque using an intended overall torque, wherein the machine control module is connected to the frequency converter and arranged to transmit the reference flux and the reference torque to the frequency converter.