Electric Machine Torque Compensation for Powertrain Vibration
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Solution Overview
Problem
Mechanical vibration and associated acoustic noise are generated during torque transfer between internal combustion engines and electric motor/generators in vehicle powertrain systems due to design and operating characteristics, leading to periodic ripples in motor shaft speed.
Innovation Solution
A powertrain system with an electric machine rotatably coupled to a crankshaft via a belt, where the electric machine's rotational position and acceleration rate are monitored to determine a virtual inertia term, which is used to calculate a torque compensation term, allowing for controlled torque generation to mitigate speed ripples and reduce noise and vibration without hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If torque is transferred between the engine and electric motor/generator via a belt-driven mechanism, then mechanical coupling and torque transfer are achieved, but mechanical vibration and acoustic noise are generated due to periodic ripples in motor shaft speed
Solution Approach 1:
The patent changes the torque command parameter dynamically by adding a compensation term that is calculated based on the derivative of the motor shaft speed. This parameter change allows the system to counteract the periodic ripples and reduce vibration and noise without modifying the physical belt-driven mechanism
Solution Approach 2:
The patent replaces potential mechanical vibration damping hardware with a control-based solution. By using a speed observer and calculating a compensation torque term through electronic control, the system substitutes mechanical intervention with electronic regulation to achieve vibration reduction
2Object-generated harmful factors
If hardware modifications are implemented to reduce vibration and noise, then vibration damping effectiveness is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces mechanical vibration damping hardware with a control-based solution. By using a speed observer and calculating a compensation torque term through electronic control, the system substitutes mechanical intervention with electronic regulation to achieve vibration reduction
Solution Approach 2:
The system uses its own existing sensors and processors to generate the vibration compensation. The speed observer utilizes existing motor position feedback to estimate speed and generate the compensation torque, allowing the system to self-regulate without external hardware additions
3Object-generated harmful factors
If engine crank position monitoring is implemented to reduce vibration, then vibration damping precision is improved, but device complexity and measurement requirements increase
Solution Approach 1:
The patent replaces mechanical vibration damping hardware with a control-based solution. By using a speed observer and calculating a compensation torque term through electronic control, the system substitutes mechanical intervention with electronic regulation to achieve vibration reduction
Solution Approach 2:
The patent introduces a speed observer as an intermediary that processes existing motor position feedback to generate estimated speed and compensation torque. This intermediary transforms available position data into actionable vibration compensation without requiring direct crank position sensing
Data Source
AI summary
A powertrain system including an electric machine rotatably coupled to a crankshaft of an internal combustion engine via a belt is described, wherein the electric machine is disposed to generate torque. A method for controlling the electric machine includes monitoring rotational position of the electric machine, and periodically executing a speed observer to determine a rotational speed of the electric machine based upon the monitored rotational position of the electric machine. An acceleration observer is periodically executed to determine an acceleration rate, wherein the acceleration rate is determined based upon a time-based change in the rotational speed of the electric machine. A virtual inertia term is determined based upon the acceleration rate, and a torque compensation term is determined based upon the virtual inertia term and the acceleration rate. The electric machine is controlled to generate torque based upon the torque compensation term.