Harmonic Regulator for Motor Speed Stability
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Solution Overview
Problem
Existing motor control systems face challenges in maintaining desired speed with minimal speed variation due to periodic torque disturbances, particularly from engine cylinder compression/cam linkage interactions and electrical distortions, which current techniques like repetitive controllers and harmonic regulation methods fail to address effectively.
Innovation Solution
A harmonic regulator system that transforms feedback signals into a harmonic reference frame, subtracts error signals, and adds compensation signals to control signals to regulate individual harmonics, effectively minimizing or eliminating periodic torque disturbances by using a qd control signal framework and PI regulators, even at low engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the bandwidth of the drive speed loop is raised to reduce speed variation, then speed stability improves, but the system becomes more sensitive to noise and computational complexity increases
Solution Approach 1:
The control system segments the torque disturbance into individual harmonic components using Fourier series decomposition. Each harmonic is processed separately through its own PI regulator, allowing targeted compensation without requiring excessive overall bandwidth. This segmentation enables effective disturbance rejection at specific frequencies while maintaining system stability.
Solution Approach 2:
The patent introduces an intermediary harmonic regulator block between the speed control loop and the power converter. This intermediary processes the speed error signal through Fourier analysis and generates harmonic-specific compensation commands, effectively mediating between the conflicting requirements of high bandwidth and controlled complexity.
2Stability of the object's composition
If a disturbance torque observer is added to decouple and minimize speed variation, then speed stability improves, but measurement precision deteriorates due to acceleration estimate error
Solution Approach 1:
The patent replaces the mechanical differentiation process (which amplifies noise and estimation errors) with an electrical/software-based Fourier series approach. By transforming the speed signal into the frequency domain, the system can accurately extract harmonic components without the numerical differentiation errors that plague time-domain acceleration estimation methods.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual speed, comparing it with the reference speed, and using the error signal to adjust the harmonic compensation commands. The Fourier coefficients are updated based on the persistent speed error, creating a closed-loop system that adapts to actual disturbance conditions rather than relying on potentially inaccurate open-loop acceleration estimates.
3Manufacturing precision
If a repetitive controller is used to compensate for harmonics, then harmonic compensation improves, but system stability deteriorates and online learning is precluded
Solution Approach 1:
The patent changes the control parameters from fixed repetitive control gains to adaptive PI regulator gains for each harmonic component. The PI regulators provide infinite gain at DC in the transformed frame, ensuring complete rejection of persistent harmonics, while the gains can be independently tuned for each harmonic to maintain stability. This parameter adaptation allows stable operation with effective harmonic compensation.
4Manufacturing precision
If FFT processing is performed to remove unwanted harmonic multiples, then harmonic regulation precision improves, but computational complexity and processing time increase
Solution Approach 1:
The patent performs preliminary action by pre-calculating the Fourier series coefficients for the reference speed profile and storing them in lookup tables. During real-time operation, these pre-computed coefficients are simply retrieved and scaled according to the actual speed, avoiding the need for complex real-time FFT processing. This preliminary computation significantly reduces online computational burden while maintaining precision.
Data Source
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AI summary
Presented is a harmonic regulator that regulates a plurality of individual harmonics in a system having periodic torque disturbances to commanded values, including zero. For each harmonic being regulated, a feedback signal having at least one harmonic component due to the harmonic being regulated is transformed from a source reference frame to a harmonic reference frame of the harmonic being regulated to form a qd feedback signal. The qd feedback signal is subtracted from the commanded value to form a qd signal and regulated. The regulated qd signal is transformed to a destination reference frame to form a compensation signal and the compensation signal is added to a control signal to form a qd control signal that drives each harmonic being regulated towards the commanded value.