Vehicle Key Positioning Using ToF for Outdoor Area Accuracy
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Solution Overview
Problem
Existing vehicle electronic key systems face challenges in accurately determining the position of a portable device with respect to a vehicle, particularly in outdoor operation areas, due to the attenuation of high-frequency radio waves by the vehicle body and human presence, leading to unreliable reception strength measurements.
Innovation Solution
A position determination system that employs multiple outdoor and indoor communication units to assess the reception strength and time of flight (ToF) correlation values of wireless signals from a portable device, using these parameters to differentiate between vehicle interior and outdoor operation areas, thereby enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If reception strength is used for position determination in outdoor areas, then the system can operate with simple measurement, but the measurement precision deteriorates due to signal attenuation by vehicle body and human presence
Solution Approach 1:
The patent changes the measurement parameter from reception strength (RSSI) to time of flight (ToF) correlation values. ToF measures the actual propagation time of wireless signals, which directly correlates with distance and is not affected by signal attenuation from vehicle body or human presence. This parameter change resolves the contradiction by providing accurate outdoor position determination without relying on reception strength.
2Measurement precision
If multiple parameters are used for position determination, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent dynamically selects the appropriate parameter based on the determined area. When the portable device is determined to be in the vehicle interior, reception strength is used. When in outdoor operation areas, ToF correlation values are used. This dynamic adaptation allows the system to achieve high measurement precision in each specific context without requiring all measurement capabilities to be active simultaneously, thus managing device complexity effectively.
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
This configuration allows for more accurate determination of the portable device's position, both inside the vehicle and in outdoor operation areas, by leveraging the ToF correlation values which are less affected by human presence and vehicle structure, compared to relying solely on reception strength.
Implementation Method 1
acquire a time of flight (ToF) correlation value as a parameter different from the reception strength
Data Source
AI summary
A position determination system includes a microcomputer configured to: control operations of multiple outdoor units and an indoor unit; determine whether a portable device is present inside a vehicle interior or in an outdoor operation area; acquire a reception strength of a signal from the portable device in each indoor and outdoor units, acquire a time of flight (ToF) correlation value as a parameter different from the reception strength, change a type of the parameter used for position determination corresponding to an area for which the position determination is to be performed; determine whether the portable device is present inside the vehicle interior based on the reception strength observed in each outdoor unit and indoor unit, determine whether the portable device is present in the outdoor operation area based on the ToF correlation value.