IMU Power Reduction via Dynamic Sampling Rate State Transitions
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Solution Overview
Problem
Wearable devices face challenges in reducing power consumption while maintaining functionality, particularly due to the need for efficient use of inertial measurement units (IMUs) to detect motion and touch events, which affects battery life and user satisfaction.
Innovation Solution
The implementation of a state transition mechanism for IMUs in wearable devices, where sampling rates are dynamically adjusted based on detected motion, allowing for power-saving modes while still enabling the detection of motion and tap events, including single and double taps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the IMU sampling rate is increased to improve detection accuracy of motion and tap events, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by transitioning the IMU between different operational states (low-power state and active state) based on detected motion conditions. The sampling rate is dynamically adjusted: in the low-power state, the IMU operates at a reduced sampling rate, and when motion is detected, it transitions to an active state with a higher sampling rate to accurately detect tap events. This dynamic state transition resolves the contradiction by adapting the sampling rate to actual detection needs rather than maintaining a constantly high rate.
Solution Approach 2:
The patent changes the sampling rate parameter of the IMU based on operational requirements. By switching between a first sampling rate (lower) in low-power state and a second sampling rate (higher) in active state, the system optimizes the balance between detection accuracy and power consumption. This parameter adjustment allows the IMU to maintain measurement precision when needed while reducing energy usage during periods of minimal activity.
2Use of energy by moving object
If the IMU is placed in a low power state with reduced sampling rate, then power consumption is reduced, but detection capability of fast tap events deteriorates
Solution Approach 1:
The patent implements preliminary action by continuously monitoring for motion at a lower sampling rate before transitioning to full detection mode. The low-power state maintains just enough sampling to detect the presence of motion, and upon detecting a potential tap event, the system transitions to the active state with higher sampling rate to confirm and characterize the event. This preliminary detection approach ensures that fast tap events are not missed while minimizing power consumption during intervals between events.
3Weight of moving object
If a small battery is used to reduce device size and weight, then device portability is improved, but battery life deteriorates
Solution Approach 1:
The patent applies periodic action by implementing intermittent high-rate sampling rather than continuous high-rate sampling. The IMU alternates between low-power state with reduced sampling and active state with higher sampling based on motion detection needs. This periodic switching between operational modes reduces average power consumption, thereby extending battery life for devices with small batteries, while still maintaining the capability to detect tap events when they occur.
Data Source
AI summary
Systems and methods for detecting touch events with an accelerometer are disclosed. In one aspect, a method includes measuring first accelerometer data at a first rate, detecting a first touch event based on the first accelerometer data, in response to detecting the first touch event, measuring second accelerometer data at a second rate, determining whether a second touch event is detected based on the second accelerometer data, measuring third accelerometer data at the first rate in response to an absence of the second touch event being detecting in the second accelerometer data over a predetermined threshold period of time.