Sensor Offset Determination Using Pre-Shutdown Memory
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Solution Overview
Problem
Existing vehicle dynamics control systems face challenges in accurately determining the offset value of longitudinal acceleration sensors due to temperature changes during the shutdown process, leading to erroneous offset values when the vehicle is restarted, especially when sensors are exposed to varying temperatures.
Innovation Solution
A method that uses low-pass filtering to determine the offset value outside the shutdown period and introduces an auxiliary variable to correct the sensor signal immediately after ignition is switched on, ensuring the offset value adapts to the sensor's temperature change, thereby minimizing the impact of short-term temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor is installed near the engine or underbody where temperature changes are significant, then the sensor can detect roadway gradient accurately during operation, but the offset value becomes highly temperature-dependent and erroneous after shutdown
Solution Approach 1:
The system determines the offset value before the shutdown process begins, when the sensor is still at operating temperature. This preliminary determination ensures that the stored offset value reflects the sensor's characteristics at the temperature it will have when measurement begins after restart, preventing the temperature-dependent offset error that occurs when offset is determined after shutdown.
Solution Approach 2:
The control device stores the determined offset value in memory and retrieves it after shutdown. The system continuously monitors whether the vehicle is in shutdown mode and selectively applies the stored offset value only during shutdown periods, creating a feedback mechanism that adapts to temperature changes by using the appropriate offset value for the current operational state.
2Adaptability or versatility
If the offset value is determined after shutdown, then the sensor has assumed the ambient temperature at the installation location, but the determined offset value becomes erroneous due to temperature change during shutdown
Solution Approach 1:
The offset value is determined before shutdown occurs, capturing the sensor's offset at its operating temperature. This preliminary determination prevents the temperature-induced offset error that would occur if offset determination waited until after shutdown, while still allowing the sensor to adapt to its installation location's ambient temperature during normal operation.
Solution Approach 2:
The system proactively determines and stores the offset value before the harmful temperature change during shutdown occurs. This beforehand action cushions against the subsequent offset error by having the correct offset value ready in memory to be applied when the vehicle restarts, preventing the measurement error before it can affect roadway gradient calculations.
3Reliability
If long-term offset compensation algorithms are used to learn and store offset values, then offset drift over long periods is compensated, but short-term offset changes during shutdown cannot be adjusted immediately
Solution Approach 1:
The offset compensation approach is segmented into two distinct time scales: long-term offset compensation algorithms handle slow drift over extended periods, while a separate mechanism determines and stores offset values before shutdown to address short-term temperature changes. This segmentation allows each mechanism to optimize for its specific time scale without interfering with the other.
Solution Approach 2:
The system performs preliminary offset determination before shutdown occurs, capturing the offset value at the appropriate temperature state. This preliminary action enables immediate application of the correct offset value after restart, eliminating the delayed response problem of traditional methods that only discover offset errors after shutdown has already caused measurement inaccuracies.
Data Source
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AI summary
The invention relates to a method for determining the offset value of a sensor signal in a vehicle after the end of a switch-off period in which the vehicle was switched off, containing the steps of - determining the offset value of the sensor signal before the start of the switch-off period, - storing the determined offset value in a data memory, - determining the changed offset value of the sensor signal after the end of the switch-off period from the offset value determined before the start of the switch-off period and the sensor signal available after the end of the switch-off period.