Steering Inverter Harmonic Compensation for Torque Ripple
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Solution Overview
Problem
Permanently excited synchronous machines in steering systems experience torque ripple due to parasitic effects, particularly in the weak-field region, leading to noticeable acoustic issues that can be perceived as faults by drivers, necessitating a solution to reduce noise and complaints.
Innovation Solution
A control device calculates a compensation voltage using a harmonic machine model to cancel the sixth-order electrical harmonic torque ripple by maintaining a voltage reserve, allowing operation close to the voltage limit while maximizing torque yield through efficient modulation voltage utilization, either by extending the modulation limit along a circle or hexagon in the voltage plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the permanently excited synchronous machine is operated close to the voltage limit to maximize torque yield, then the power output is improved, but the torque ripple increases due to parasitic effects
Solution Approach 1:
The control device calculates a compensation voltage based on a harmonic machine model that predicts the torque ripple before it occurs. This compensation voltage is added to the fundamental actuating voltage in advance, creating a preliminary counteracting effect that cancels out the parasitic torque harmonic when the machine operates close to the voltage limit
2Object-generated harmful factors
If a compensation voltage is added to cancel the sixth-order electrical harmonic torque ripple, then the acoustic noise is reduced, but the available voltage reserve decreases
Solution Approach 1:
The control device dynamically adjusts the fundamental actuating voltage based on the calculated voltage reserve. When compensation is needed, the fundamental voltage is reduced to accommodate the compensation voltage within the available modulation limit, ensuring optimal use of the voltage reserve while maintaining torque ripple cancellation
3Power
If the modulation limit is extended along a hexagon in the voltage plane to fully utilize the inverter actuation range, then the torque yield is increased, but the control complexity increases
Solution Approach 1:
The control device changes the modulation strategy by extending the modulation limit along a hexagon in the voltage plane instead of a circle. This parameter change allows full utilization of the inverter's actuation range, maximizing torque yield while the automated calculation methods manage the control complexity
Data Source
AI summary
The disclosure relates to a method for operating a steering system of a motor vehicle. A voltage reserve is determined as a function of a compensation trajectory for a second actuating voltage and as a function of a modulation limit. A first actuating voltage with a fundamental frequency is determined as a function of the voltage reserve. A compensation voltage with a sixth-order harmonic with respect to the fundamental frequency of the first actuating voltage is determined. The second actuating voltage is determined for an inverter as a function of the first actuating voltage and as a function of the compensation voltage.