IMU Data Compression Using Remainder Rounding to Cut Power
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Solution Overview
Problem
Current motion sensing devices with inertial measurement units (IMUs) and application processors (APs) face challenges such as excessive power consumption and buffer overflow due to high bandwidth requirements and low update rates, particularly in consumer-grade mobile devices, which limit data transmission rates and accuracy.
Innovation Solution
The system employs a method to reduce energy consumption by rounding velocity and orientation increments at the IMU, using a FIFO buffer for on-demand data transmission, and applying variable quantization and lossy compression techniques to maintain integral accuracy while minimizing data transmission, including signal pre-conditioning and predictive algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling frequency is increased to prevent aliasing and maintain measurement accuracy, then the measurement precision is improved, but the power consumption and bandwidth requirements increase excessively
Solution Approach 1:
The patent segments the data processing workflow into two distinct stages: (1) high-frequency sampling at the IMU for accurate motion capture, and (2) low-frequency transmission to the AP for application processing. The IMU continuously samples at high rates (e.g., 2-4 kHz) to prevent aliasing, while the processed results are transmitted to the AP at lower update rates (e.g., 24 Hz or 1 Hz), thereby maintaining measurement precision while reducing power consumption and bandwidth requirements.
Solution Approach 2:
The patent introduces an intermediary processing stage between the IMU sensors and the AP. The IMU performs strap-down integration and combines multiple samples to determine velocity and orientation increments, acting as an intermediary that processes high-frequency data locally and transmits only essential processed results to the AP. This intermediary function allows the system to maintain high sampling rates for accuracy while reducing the data transmission burden.
2Productivity
If the data transmission rate is increased to maintain high update rates, then the productivity is improved, but the bandwidth requirements and power consumption increase
Solution Approach 1:
The patent extracts and transmits only the essential processed results (velocity and orientation increments) from the IMU to the AP, rather than transmitting all raw sensor data. By performing strap-down integration and sample combination at the IMU, the system extracts the critical motion information and transmits it at lower update rates (e.g., 24 Hz or 1 Hz), thereby maintaining productivity for typical applications while significantly reducing the quantity of data transmitted.
Solution Approach 2:
The patent applies partial action by transmitting data at update rates sufficient for typical applications (24 Hz for screen streaming, 1 Hz for pedestrian navigation) rather than continuously transmitting at the maximum sampling rate. This partial transmission approach maintains adequate productivity for most use cases while reducing overall data transmission volume and power consumption.
3Reliability
If the FIFO buffer size is increased to prevent buffer overflow, then the reliability is improved, but the device complexity and memory requirements increase
Solution Approach 1:
The patent implements dynamic buffer management where the FIFO buffer size and update rate can be adjusted based on application requirements and system conditions. The IMU can adaptively control the buffering strategy, switching between different update rates (e.g., 24 Hz, 1 Hz) and buffer configurations to prevent overflow while minimizing memory requirements and complexity for different operational scenarios.
4Quantity of substance
If the quantization resolution is decreased to reduce data transmission volume, then the loss of substance is reduced, but the measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by performing strap-down integration and sample combination at the IMU before transmission to the AP. By pre-processing the high-frequency samples and computing velocity and orientation increments at the source, the system reduces the data volume requiring transmission while maintaining adequate precision for application purposes. The preprocessing ensures that only essential information is transmitted, reducing quantization requirements.
Data Source
AI summary
A method, controller and system in accordance with various aspects of the present disclosure facilitate reduced energy consumption in a motion sensing device having an inertial measurement unit (IMU), with a strap down integration unit, and an application processing unit (AP). The system and method include rounding velocity increments and orientation increments at the inertial measurement unit, thereby producing a remainder values. The remainder values are added to subsequent velocity increments and orientation increments prior to rounding of those values, and so on. In this way, while motion granularity is slightly decreased, there is no drift of integration errors over time.