PMSM Control via Flux Linkage Model Fitting for Temperature Adaptation
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Solution Overview
Problem
Permanent magnet synchronous motors in electric power steering systems face challenges in maintaining performance across varying temperatures, as many motor parameters are temperature-dependent, and existing control methods are not effectively adaptable to these changes.
Innovation Solution
A method that involves fitting a flux linkage model to real operational data to determine operational parameters, which are then used to modify current demand signals and optimize motor performance, including adapting phase advance and torque production to maximize electromagnetic torque and efficiency while avoiding costly temperature testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional control methods are used, then the control system is simple, but motor performance deteriorates under varying temperature conditions
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting control parameters (current demand signals, phase advance angles) based on temperature-dependent motor parameters obtained through flux linkage model fitting. The model adapts parameters such as stator resistance, inductance, and permanent magnet flux linkage according to operating temperature, enabling the control system to maintain optimal performance across varying temperature conditions without requiring complex hardware modifications.
Solution Approach 2:
The patent replaces physical temperature sensing and thermal monitoring hardware with a mathematical flux linkage model that estimates temperature-dependent parameters through electrical measurements. Instead of using additional temperature sensors and thermal management hardware, the system uses electrical model fitting to infer motor parameters and compensate for temperature effects, reducing device complexity while improving reliability.
2Reliability
If temperature testing and thermal monitoring systems are added, then motor performance under temperature variations improves, but device complexity and cost increase
Solution Approach 1:
The patent implements self-service by enabling the motor control system to automatically compensate for temperature effects using its own electrical measurements and the flux linkage model. The system monitors its own electrical parameters (voltages, currents, frequencies) and uses model fitting to determine temperature-dependent motor parameters, eliminating the need for external temperature sensors or separate thermal monitoring systems. The control algorithm self-adjusts based on inferred temperature conditions.
Solution Approach 2:
The flux linkage model serves multiple functions simultaneously: it characterizes motor performance, estimates temperature-dependent parameters, generates current demand signals, and provides diagnostic capabilities. This multi-functional approach replaces what would otherwise require separate temperature sensing, parameter characterization, and diagnostic systems, reducing overall device complexity while improving temperature adaptation capability.
3Productivity
If flux linkage model fitting is implemented, then motor performance and efficiency improve, but computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-developing the flux linkage model and its fitting algorithms during the design and commissioning phase. The model structure, parameter relationships, and fitting procedures are established beforehand, allowing the control system to efficiently execute model-based compensation during operation. This preliminary preparation reduces real-time computational complexity by transforming complex model fitting into streamlined calculations that can be executed within control cycle time constraints.
Solution Approach 2:
The system implements feedback by continuously comparing measured electrical parameters with model predictions and adjusting control signals based on the differences. The flux linkage model fitting process provides real-time feedback on motor parameter deviations caused by temperature changes, enabling dynamic compensation of current demand signals and phase advance angles. This feedback mechanism improves motor efficiency by maintaining optimal operating parameters despite temperature variations.
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 allows for improved motor performance and efficiency by maximizing torque and minimizing current usage, while also providing accurate temperature estimation and diagnostic capabilities, reducing the need for additional sensors and thermal monitoring systems.
Implementation Method 1
The rotor of a permanent magnet synchronous motor rotates in synchronism with the electrical supply. By varying the frequency of the AC current supplied to the motor, the motor speed can be varied.
Implementation Method 2
For a permanent magnet synchronous motor with surface mounted magnets, at low speeds, the assistance torque available is proportional to the magnitude of the phase current supplied to the motor.
Implementation Method 3
The inverter includes a set of switching elements that can be opened and closed to connect each phase to a positive battery supply or to ground. Rapidly opening and closing the switches in a defined pattern enables the AC waveforms to be applied to each phase from the DC battery supply.
Data Source
AI summary
A method of controlling a motor, for example of an electric power steering system, includes receiving a motor torque demand signal indicative of a torque required from the motor. A current demand signal indicative of the currents to be applied to each phase to meet the torque demand is generated from the motor torque demand signal. One or more operational values from the motor are determined. The current demand signal is set as a function of one or more parameters of the motor obtained by fitting a flux linkage model to the measured operational values. A motor circuit having the permanent magnet electric motor includes a control stage arranged to generate the current demand signal in response to a torque demanded of the motor. A modifying means modifies the magnitude and/or the phase of the current demanded for each phase of the motor by the controller.