Latent Oscillator Frequency Estimation for UWB Ranging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ultra-wideband (UWB) radios in robotics applications face low-accuracy range measurements due to poor frequency stability of commodity oscillators, leading to high range measurement errors, which is exacerbated by the need for frequent oscillator calibration, increasing power consumption and limiting ranging rate.
Innovation Solution
A method for estimating changes in clock frequency using a factor graph model that interconnects vertices representing object locations and oscillator frequencies, allowing for fewer oscillator calibration measurements, improving ranging accuracy and rate, and reducing power consumption by modeling frequency drift as a Gaussian random walk and incorporating direct frequency observations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent oscillator calibration measurements are performed to improve ranging accuracy, then measurement precision improves, but power consumption increases and ranging rate decreases
Solution Approach 1:
The system performs oscillator calibration measurements in advance and stores the calibration data. During normal ranging operations, it uses these pre-calibrated values to compensate for frequency drift, avoiding the need for frequent recalibration. This preliminary action reduces power consumption while maintaining ranging accuracy.
Solution Approach 2:
The system continuously monitors ranging measurements and uses the factor graph to estimate oscillator frequency drift in real-time. This feedback mechanism allows the system to adjust for frequency variations without performing full calibration sequences, reducing power consumption while maintaining measurement precision.
2Measurement precision
If frequent oscillator calibration measurements are performed to improve ranging accuracy, then measurement precision improves, but ranging rate decreases
Solution Approach 1:
The system performs oscillator calibration measurements in advance and stores the calibration data. During normal ranging operations, it uses these pre-calibrated values to compensate for frequency drift, avoiding the need for frequent recalibration. This preliminary action reduces power consumption while maintaining ranging accuracy.
Solution Approach 2:
The system continuously monitors ranging measurements and uses the factor graph to estimate oscillator frequency drift in real-time. This feedback mechanism allows the system to adjust for frequency variations without performing full calibration sequences, reducing power consumption while maintaining measurement precision.
3Measurement precision
If higher precision oscillators are used to improve ranging accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The system uses the commodity oscillator's own measurements and the factor graph model to self-correct for frequency drift. By estimating drift from the ranging measurements themselves and applying corrections through the factor graph, the system achieves high accuracy without requiring expensive precision oscillators, maintaining simplicity while improving precision.
Data Source
AI summary
Time of Flight ranging using double-sided two-way ranging (DS-TWR) is a conventional method of ranging with ultra-wideband (UWB) radios and has been shown to have ranging accuracies on the order of tens of centimeters. This approach requires several transmissions for each range measurement, which does not scale well for multi-agent robotics because of the bandwidth needed for ranging measurements. This disclosure proposes a latent model for clock frequencies using a factor graph that enables greater consistency of clock synchronization and increases the rate of useful range measurements. This model is an effective and robust improvement to conventional DS-TWR that can leverage shared information from a network of robots. An increase in the rate of range measurements of 232% was obtained as compared to DS-TWR with the same hardware and transmission rate, and with a mean square error of range measurements of 20 cm.