Electric Motor Control via Load Estimation for Low Speed Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling the rotational speed of permanent magnet synchronous motors are limited by their applicability to motors with salient pole configurations and generate acoustic noise, and they are ineffective at low speeds due to the proportionality of induced voltage with rotational speed.
Innovation Solution
An apparatus comprising a current detector, controller, and load estimator that controls electric motor current based on detected current, speed command, and estimated mechanical load, independent of rotational speed, allowing stable control at low speeds without noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage pulse is applied to estimate magnetic pole positions, then starting control is achieved, but acoustic noise is generated
Solution Approach 1:
The invention extracts only the necessary information (current waveform characteristics) from the motor operation to estimate rotor position, eliminating the need to apply external voltage pulses that cause acoustic noise. The rotor position is estimated by analyzing the back-EMF waveform during normal operation without additional excitation.
Solution Approach 2:
The invention converts the back-EMF waveform, which is normally just a byproduct of motor operation, into a useful signal for rotor position estimation. By analyzing the characteristics of the back-EMF waveform during normal operation, the system achieves position estimation without generating additional noise.
2Adaptability or versatility
If induced voltage is used for position estimation, then method is independent of motor configuration, but control fails at low speeds
Solution Approach 1:
The invention performs preliminary analysis of the back-EMF waveform characteristics to establish estimation algorithms that work across all speed ranges. By pre-processing the waveform data and identifying key features that remain detectable even at low speeds, the system maintains configuration independence while enabling low-speed control.
Solution Approach 2:
The invention changes the analysis parameters from relying on amplitude (which is speed-dependent) to relying on waveform shape and zero-crossing points (which are configuration-dependent but speed-independent). This allows the estimation method to remain effective across the full speed range while maintaining independence from specific motor configurations.
3Measurement precision
If pulsating voltage is applied to estimate positions, then rotor position can be determined, but application is limited to salient pole motors
Solution Approach 1:
The invention creates a universal position estimation method that works with both salient pole and non-salient pole motors by analyzing the back-EMF waveform characteristics. The method uses general waveform features (zero-crossing points, slope characteristics) that exist in all motor types, making the system universally applicable while maintaining precise position detection.
Data Source
AI summary
An apparatus for controlling the drive of an electric motor, having a current detector for detecting the current through an externally connected electric motor; a controller for generating a control signal to control the electric motor on the basis of the current detected by the current detector and the speed command for specifying the rotational speed of the electric motor; wherein the apparatus includes a load estimator for estimating the mechanical load condition associated with the electric motor on the basis of the current detected by the current detector and the speed command, and the controller controls the electric motor current on the basis of the detected current, the speed command and the estimated load condition.