IMU Strapdown Integration Buffer for Power-Constrained Motion Sensing
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Solution Overview
Problem
Current inertial measurement unit (IMU) and application processor (AP) systems face challenges in reducing bandwidth requirements and preventing buffer overflow, particularly in power-constrained mobile devices, where high sampling frequencies lead to excessive power consumption and low update rates.
Innovation Solution
Implementing a FIFO buffer in the IMU to store velocity and orientation increments, allowing for on-demand data transmission and combining oldest values to prevent buffer overflow, along with event detection and a backtrack buffer to handle high-frequency events, enabling efficient data communication and reducing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sampling frequency is used to accurately sense motion, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by performing strap-down integration computations within the IMU before data transmission. The IMU pre-processes raw sensor data into velocity and orientation increments, so that only processed results need to be transmitted to the application processor. This reduces the frequency and volume of data transmissions, thereby lowering power consumption while maintaining measurement precision.
Solution Approach 2:
The patent extracts and processes only the essential motion information (velocity and orientation increments) within the IMU using strap-down integration. By extracting only the necessary derived parameters and transmitting them instead of raw high-frequency sensor data, the system reduces communication bandwidth requirements and power consumption while preserving the essential motion measurement precision.
2Reliability
If high update rate is implemented to maintain data freshness, then reliability is improved, but bandwidth requirements increase
Solution Approach 1:
The patent performs preliminary strap-down integration computations within the IMU to generate velocity and orientation increments at high rates. By pre-processing data at the source and transmitting only the essential integrated results, the system maintains high update rates and data freshness without requiring excessive communication bandwidth, thus resolving the contradiction between reliability and bandwidth requirements.
3Reliability
If buffer size is increased to prevent overflow, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing strap-down integration within the IMU to generate compact velocity and orientation increment values. These pre-processed values occupy less memory space than raw sensor data, allowing the buffer to maintain sufficient capacity for overflow prevention without requiring large memory allocations, thus resolving the contradiction between reliability and device complexity.
Data Source
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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 sensing acceleration values and rotational values at the IMU and converting the sensed acceleration and rotational values into velocity and orientation increments by strap down integration. The velocity and orientation increments are stored in a first buffer at the IMU between updates to the AP. When an update request is received at the IMU from the AP over an interrupt link, the buffer contents are transmitted over a serial link from the IMU to the AP.