Wearable Sensor Protection Volumes for Handheld Power Tools
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Solution Overview
Problem
Existing power tool operator protection systems, such as those described in US 2010/0064532 A1, are not sufficiently efficient, accurate, or reliable in preventing injuries to chainsaw operators, as they rely on simple distance-based sensors that do not account for the dynamic posture and geometry of the operator or the power tool, leading to potential kickback incidents.
Innovation Solution
A power tool operator protection system utilizing wearable position sensors and a power tool position sensor to generate a model of the operator's posture and associate each limb with a protection volume, determining the position and motion of the power tool's working implement relative to these volumes to generate a protection signal, which can alert the user or activate safety features to prevent accidents, even when the implement is close to the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple distance-based sensors are used to protect operators, then the device complexity is reduced, but the measurement precision and reliability of injury prevention deteriorate
Solution Approach 1:
The operator's body is segmented into multiple limbs (arms, legs, torso), each equipped with separate position sensors. This segmentation allows the system to track the precise position of each body part independently, creating a detailed skeletal model that accurately represents the operator's dynamic posture while maintaining manageable system complexity through modular sensor placement.
Solution Approach 2:
The system transitions from simple one-dimensional distance measurement to three-dimensional spatial tracking by monitoring the x, y, z coordinates of multiple sensors on different body parts. This dimensional expansion enables accurate reconstruction of the operator's posture and orientation, significantly improving measurement precision for injury prevention.
2Productivity
If the working implement is allowed close to the operator's body, then productivity is improved, but the safety and reliability of operation deteriorates
Solution Approach 1:
The protection system dynamically adjusts safety zones based on the operator's real-time posture and the implement's position. Rather than using fixed safety distances, the system calculates dynamic protection volumes that adapt to the operator's limb positions and orientations, allowing safe operation when the implement is close to the body while maintaining high injury prevention reliability.
Solution Approach 2:
The system continuously monitors the relative positions of the working implement and operator's body parts through multiple sensors, providing real-time feedback. When the implement approaches dangerous proximity to any body part, the system generates protection signals that can alert the operator or activate safety functions, enabling safe close-proximity operation through active monitoring and response.
3Loss of information
If a protection signal is generated only when the implement enters the protection volume, then false alarms are reduced, but the response time for injury prevention is delayed
Solution Approach 1:
The system performs preliminary calculations of protection volumes and safety zones in advance, based on the operator's current posture and the implement's position. By pre-computing these safety parameters, the system can immediately generate protection signals when dangerous conditions arise, eliminating calculation delays while maintaining accurate false alarm filtering through pre-established safety criteria.
Data Source
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AI summary
A power tool operator protection system comprises a plurality of wearable position sensors configured to be worn by an operator of a handheld power tool; a power tool position sensor configured to detect the position of a handheld power tool; and processing equipment configured to generate a model of the operator based on the mutual positions of the respective wearable sensors relative to each other, the mutual positions defining the operator's posture; associate each of a plurality of limbs (32a-g) of the operator with a respective protection volume (30a-g); and based on the position and/or motion of the power tool in relation to the protection volume (30a-g) indicating an imminent danger that the working implement enters a protection volume (30a-g), generate a protection signal.