Electric Motor Torque Band Control for EV Gear Rattle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gear rattle in electric vehicles is a noticeable issue due to the lack of engine noise masking the sound of gear impacts, which occurs when intermeshing gear teeth separate and impact, causing undesirable noise in the passenger cabin.
Innovation Solution
A method and system to control the torque output of an electric motor by maintaining it within a predefined torque band, using threshold levels to prevent gear rattle by ensuring sufficient torque for gear contact, determined by rotational speed and vehicle speed, utilizing a controller to manage torque levels based on predefined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor operates at low torque levels, then energy consumption is reduced, but gear rattle noise increases due to insufficient torque to maintain gear contact
Solution Approach 1:
The controller dynamically adjusts the torque output parameter of the electric motor based on operating conditions (rotational speed, acceleration requests). When the motor operates within a problematic rotational speed range, the controller modifies the torque parameter to stay above a threshold level, preventing gear rattle while minimizing energy consumption by only adjusting torque when necessary.
2Object-affected harmful factors
If the electric motor increases torque output to prevent gear rattle, then gear contact is maintained, but energy consumption increases
Solution Approach 1:
The torque threshold is not fixed but dynamic, varying with the rotational speed of the motor. The controller continuously monitors operating conditions and adjusts the minimum torque requirement accordingly. This dynamic approach ensures gear rattle prevention only when actually needed (within problematic speed ranges), rather than maintaining high torque continuously, thus reducing unnecessary energy consumption.
Solution Approach 2:
The control system uses feedback from the motor's own operational parameters (rotational speed, current torque output) to automatically adjust torque levels. The controller independently determines when torque adjustment is needed based on pre-defined threshold criteria, enabling the system to self-regulate and prevent gear rattle without external intervention while minimizing energy use.
3Use of energy by moving object
If torque threshold levels are set low to allow energy-efficient operation, then energy consumption decreases, but gear rattle prevention becomes ineffective
Solution Approach 1:
The torque threshold parameter is made dependent on rotational speed. Rather than using a single fixed threshold that would either be too low (ineffective) or too high (inefficient), the system implements a variable threshold that adapts to the motor's operating conditions. This ensures reliable gear rattle mitigation across different operating ranges while allowing energy-efficient operation when conditions permit.
Data Source
AI summary
Embodiments include a method for controlling a torque of an electric motor. The method includes receiving a requested output torque for the electric motor and obtaining a rotational speed of the electric motor. Based on determining that the rotational speed of the electric motor is within a predefined range, the method includes instructing the electric motor to operate at the requested output torque based on determining that the requested output torque is greater than a first threshold or less than a second threshold, instructing the electric motor to operate with a torque that is at least the first threshold based on determining that the requested output torque is less than the first threshold and greater than zero, and instructing the electric motor to operate with the torque that is at most the second threshold based on determining that the requested output torque is greater than the second threshold.