Electric Machine Audible Sound Generation via PWM Dithering
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Solution Overview
Problem
Electric vehicles operating in silent mode can be difficult to audibly locate and communicate acceleration, deceleration, and direction due to reduced noise emission, which poses challenges for safety and awareness.
Innovation Solution
A vehicle powertrain system that includes an electric machine connected to a power inverter, where the system determines a preferred audible sound based on vehicle speed and incorporates this sound into control signals to generate a specific sound through PWM frequency dithering and current injection, enabling the electric machine to produce a vehicle-speed-dependent audible tone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the vehicle operates in electric vehicle mode with a power inverter and electric machine, then energy efficiency and emissions are improved, but audible noise emission is reduced making the vehicle difficult to locate
Solution Approach 1:
The patent applies mechanical vibration by intentionally inducing vibrations in the electric machine components (such as the stator or rotor) to generate audible sounds. The controller modulates the electrical signals to the electric machine to create controlled vibrations that produce desired audible feedback, allowing the vehicle to emit sound while operating in electric mode without compromising energy efficiency or emissions performance.
Solution Approach 2:
The patent employs periodic action by using pulse-width modulation (PWM) techniques to generate audible sounds through periodic switching of electrical signals to the electric machine. The controller applies periodic electrical pulses at frequencies within the audible range, creating rhythmic vibrations that produce the desired audible feedback. This periodic control method enables precise regulation of sound characteristics while maintaining efficient electric vehicle operation.
2Productivity
If the power inverter operates the electric machine in electric vehicle mode, then propulsion efficiency is improved, but the vehicle's presence and operation become less detectable to pedestrians and other drivers
Solution Approach 1:
The patent implements feedback by using sensors to detect vehicle operating conditions (such as acceleration, deceleration, and direction) and feeding this information back to the controller. The controller then adjusts the audible sound generation in real-time based on this feedback, ensuring that the vehicle emits appropriate sounds that communicate its presence and operational state to pedestrians and other drivers while maintaining propulsion efficiency.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the frequency, amplitude, and timing of audible sounds based on vehicle operating parameters. The controller modifies sound characteristics in response to changes in vehicle speed, acceleration, and operational mode, ensuring that the audible feedback remains informative and appropriate for current driving conditions while preserving propulsion system efficiency.
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
The solution effectively enhances the audible feedback of electric vehicles, improving safety by providing a vehicle-speed-dependent sound that alerts pedestrians and other drivers to the vehicle's presence and operation, thereby addressing the silent operation challenge.
Implementation Method 1
an electric machine electrically connected to a power inverter
Implementation Method 2
A method for controlling the powertrain system includes determining a vehicle speed, and determining a preferred audible sound to be generated by the powertrain system when operating in the electric vehicle mode at the vehicle speed
Data Source
AI summary
A vehicle including a powertrain system that includes an electric machine electrically connected to a power inverter is described, wherein the powertrain system is operative in an electric vehicle mode to generate propulsion torque. A method for controlling the powertrain system includes determining a vehicle speed, and determining a preferred audible sound to be generated by the powertrain system when operating in the electric vehicle mode at the vehicle speed. A control signal for the power inverter is determined, and is associated with operating the powertrain system in the electric vehicle mode at the vehicle speed. The preferred audible sound is incorporated into the control signal for the power inverter, and the power inverter is controlled to operate the electric machine employing the control signal and the preferred audible sound.