Transmission Backlash Detection from EV Motor Speed Vibrations
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Solution Overview
Problem
In electric vehicles with direct power electronics and fixed transmission systems, accurately determining transmission backlash is crucial for maintaining drivability and detecting mechanical wear, as existing methods are inadequate for precise monitoring and fail to provide timely fault detection.
Innovation Solution
A method that involves detecting rotational speed fluctuations during driving interventions, filtering high-frequency oscillations to determine transmission backlash, and averaging these values over specific distances to infer mechanical wear and potential defects, with gradients indicating normal aging or impending failure, allowing for adaptive torque reduction and fault messaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to determine transmission backlash, then the system structure remains simple, but measurement precision and fault detection capability are insufficient
Solution Approach 1:
The patent replaces mechanical measurement systems with signal processing methods. Instead of using physical sensors and mechanical gauges to measure backlash, the invention uses rotational speed signals from the electric machine and applies spectral analysis to extract backlash information. This substitution achieves high measurement precision without adding complex mechanical detection devices.
Solution Approach 2:
The patent introduces rotational speed fluctuations as an intermediary to indirectly measure transmission backlash. Rather than measuring backlash directly, the system detects how backlash affects rotational speed during driving interventions, then uses signal processing to retrieve backlash values. This intermediary approach enables precise measurement while keeping the detection system simple.
2Reliability
If existing methods are used for transmission monitoring, then the system remains simple, but reliability and timely fault detection are compromised
Solution Approach 1:
The patent implements a feedback mechanism where rotational speed measurements are continuously monitored, processed to detect backlash changes, and used to trigger fault detection and maintenance scheduling. The system feeds back transmission health status to the control unit, enabling reliable fault detection while using only the existing rotational speed sensor without additional monitoring hardware.
Solution Approach 2:
The patent performs preliminary analysis of rotational speed signals during normal operation to detect early signs of transmission wear and backlash increase. By continuously evaluating spectral characteristics and detecting changes before critical failure occurs, the system achieves reliable fault detection and enables proactive maintenance without requiring complex real-time monitoring systems.
3Measurement precision
If high-frequency oscillations are not filtered, then the detection process remains simple, but measurement precision of transmission backlash is reduced
Solution Approach 1:
The patent replaces physical filtering mechanisms with digital signal processing. Instead of using mechanical filters or dampers to remove high-frequency oscillations, the invention applies spectral analysis and filtering algorithms to the rotational speed signals. This digital approach achieves precise backlash measurement while keeping the physical system simple.
4Reliability
If no averaging over distance is performed, then the detection process is simpler, but reliability of wear detection and maintenance scheduling is reduced
Solution Approach 1:
The patent continuously accumulates and averages backlash measurements over driving distance to track transmission wear progression. By maintaining a continuous record of backlash changes rather than relying on isolated measurements, the system reliably detects wear trends and determines optimal maintenance timing. This continuous evaluation uses simple data accumulation and averaging operations.
Data Source
AI summary
The invention relates to a method for ascertaining the backlash (40) of a gear (24) which is coupled to an electric machine (12) of a vehicle which has at least one electric machine (12). According to the method, at least the following steps are carried out: a) detecting the rotational speed of the at least one electric machine (12) during a driving intervention (80) and detecting rotational speed fluctuations produced therefrom, b) evaluating a high-frequency vibration (60) which is generated as a result of the gear (24) reaching a lower stop (54) in delay phases (56) and reaching an upper stop (50) when reversing the rotational direction in acceleration phases (58), c) filtering out high-frequency components from the high-frequency vibration (60) according to step b), wherein position information (42), relating to a corresponding rotational angle, from the rotational speed signal is saved in the event said components occur, and d) evaluating the distance between the upper stop (52) and the lower stop (54) and ascertaining the backlash (40) from the difference of the position information (42) between the upper stop (52) and the lower stop (54).