UWB Vehicle Access System Using TWR and TDoA Localization
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Solution Overview
Problem
Current Passive Entry Systems (PES) face challenges in accurately determining the proximity and position of a key fob relative to a vehicle due to limitations in radio frequency communication technologies, requiring multiple antennas and complex power control to satisfy both range and localization requirements.
Innovation Solution
A vehicle access system utilizing a network of ultra-wideband (UWB) system nodes throughout the vehicle, which communicate with a target portable device to determine its position through time of flight and time difference of arrival calculations, optimizing communication protocols to improve power efficiency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LF communication is used for proximity detection and localization, then localization precision is improved, but device complexity increases due to requiring multiple antennas both inside and outside the vehicle
Solution Approach 1:
The patent combines multiple localization techniques (TOF-based distance measurement and TDoA-based position determination) into a unified system that uses a single antenna per system node, eliminating the need for multiple antennas while achieving both proximity detection and localization requirements
Solution Approach 2:
Each system node is designed to perform multiple functions: transmitting poll messages for TOF measurement, receiving response messages for TDoA calculation, and participating in both proximity detection and localization tasks using the same hardware components
2Speed
If UHF communication is used for RKE functionality, then communication range is improved, but localization precision deteriorates due to inability to satisfy strict proximity requirements
Solution Approach 1:
The system segments the communication functionality into two distinct protocols: UHF for long-range RKE communication and TOF/TDoA-based UWB for precise localization, allowing each protocol to optimize for its specific function without compromise
Solution Approach 2:
The patent introduces an intermediary localization layer that uses time-stamped message exchanges between system nodes and key fobs to bridge the gap between UHF communication range and the precision requirements for proximity-based access control
3Measurement precision
If multiple antennas and optimal power control are used to satisfy proximity requirements, then localization precision is improved, but use of energy increases
Solution Approach 1:
The system implements periodic poll-message transmission at optimized intervals rather than continuous transmission, allowing the key fob and system nodes to enter low-power states between measurements while maintaining localization accuracy when needed
Solution Approach 2:
The patent dynamically adjusts transmission power and measurement frequency based on detected proximity levels, using lower power for distant objects and increasing power only when precise localization is required, thereby reducing overall energy consumption
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
Enables precise localization of the target portable device, enhancing the convenience and security of vehicle access by accurately determining its position relative to the vehicle, even in challenging communication environments.
Implementation Method 1
determining a respective time of flight between the target portable device and each system node in the first set of system nodes based on the respective first timestamp, the respective second timestamp, and the one of (i) the respective third timestamp and the fourth timestamp and (ii) the respective wait time
Implementation Method 2
determining a respective time difference of arrival between a first system node in the second set of system nodes and each other system node in the second set of system nodes based on the respective second timestamp recorded by the first system node and the respective second timestamp recorded by each other system node in the second set of system nodes
Data Source
AI summary
A vehicle access system having a plurality of system nodes arranged throughout a vehicle is disclosed. The vehicle access system employs a communication protocol which utilizes two way ranging (TWR) and time distance of arrival (TDoA) localization processes to determine a position of a target portable device. The communication protocol selects the optimal combination of TWR and TDoA estimations, depending on a number of system nodes that are in communication range of the target portable device, to provide the greatest accuracy with the best power efficiency at the target portable device. Particularly, the communication protocol minimizes the number of messages sent and received by the target portable device, thereby improving the power efficiency thereof. Furthermore, the communication protocol schedules messages between the system nodes and target portable device so as to minimize the wake time of the target portable device, thereby further improving the power efficiency thereof.