Power Tool Twist Detection Using Periodic Acceleration Integration
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Solution Overview
Problem
Existing electric power tools face errors in detecting twisting due to unwanted noise signals from acceleration sensors, leading to inaccurate speed and rotation angle calculations, which can result in improper detection of twisting events, especially during continuous operation.
Innovation Solution
The implementation of a twisted-motion detector that integrates accelerations over specific periods, weights accelerations to reduce noise-induced errors, and uses a digital high-pass filter to remove unwanted signal components, allowing for accurate detection of twisting by calculating speed and rotation angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous integration of acceleration detection signal is performed, then speed and rotation angle can be calculated, but errors accumulate due to noise leading to inaccurate twisting detection
Solution Approach 1:
The patent applies periodic action by performing integration of acceleration signals only over specific time periods rather than continuously. The integration is executed in discrete time windows, allowing the system to calculate speed and rotation angle periodically while avoiding cumulative error accumulation that would occur with continuous integration. This periodic approach maintains detection accuracy during extended operation.
Solution Approach 2:
The patent discards acceleration detection signals that fall outside the predetermined time periods for integration. By selectively ignoring signals during intervals when integration is not performed, the system prevents noise from these periods from contaminating the speed and rotation angle calculations. This selective discarding recovers accurate measurement capability by ensuring only relevant, time-bound signals contribute to the integration results.
2Difficulty of detecting and measuring
If acceleration sensor is used to detect twisting, then twisting motion can be detected, but unwanted noise signals cause errors in speed and rotation angle calculation
Solution Approach 1:
The patent applies preliminary action by establishing predetermined time periods for integration before the detection process begins. These pre-defined time windows structure when acceleration signals should be integrated and when they should be discarded. This preliminary framework ensures that only acceleration data within the correct time boundaries contributes to speed and rotation angle calculations, preventing noise from unrelated time periods from affecting measurement precision.
3Duration of action of moving object
If integration of acceleration signal is performed without time limitation, then complete motion data is captured, but errors accumulate indefinitely during long operation
Solution Approach 1:
The patent resolves the contradiction between continuous operation duration and measurement precision by implementing periodic integration with predetermined time periods. Instead of integrating acceleration signals continuously without bound, the system performs integration only during specific time windows that repeat periodically. This approach allows the system to operate indefinitely while resetting the integration baseline regularly, preventing error accumulation even during extended operation periods.
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
This approach enables precise detection of twisting events, even during long motor operation, by reducing errors and improving the accuracy of speed and rotation angle calculations, ensuring appropriate motor stoppage timing.
Implementation Method 1
The acceleration sensor is configured to detect acceleration imposed on the housing
Implementation Method 2
The twisted-motion detector is configured to calculate the speed by integrating, of the obtained accelerations, accelerations obtained in a certain period
Implementation Method 3
The twisted-motion detector is configured to detect twisting of the housing from the calculated speed
Data Source
AI summary
An electric power tool is configured to rotate an attachment about a Z-axis. The electric power tool includes a three-axes acceleration sensor and an acceleration detection circuit. The acceleration detection circuit calculates an angular acceleration about the Z-axis based on an input signal from the three-axes acceleration sensor. The acceleration detection circuit calculates a change in an angular velocity based on integrating the angular acceleration for a most recent period. The acceleration detection circuit determines a Z-axis angular velocity about the Z-axis, without adding a previous change in the angular velocity from before the most recent period, as equal to the change in angular velocity. The acceleration detection circuit detects a twisted-motion of the electric power tool based on the Z-axis angular velocity.