Single Motor-Generator Joint Selector for Wearable Energy Harvesting
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Solution Overview
Problem
Existing energy harvesting devices that target multiple body joints are inefficient due to the weight and metabolic cost of carrying multiple generators and joint selectors, and often increase metabolic cost when harvesting energy during positive mechanical power modes.
Innovation Solution
A device that uses a single motor-generator to selectively harvest energy and augment motion at either the knee or ankle joint, depending on terrain grade, by switching between harvesting and augmentation modes and connecting to either joint via a joint selector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple generators and joint selectors are used to harvest energy from multiple joints, then energy harvesting capability is improved, but device weight and metabolic cost increase
Solution Approach 1:
A single motor-generator unit is designed to perform multiple functions: it can harvest energy from different joints (knee, ankle, hip) and can operate in both generation mode (harvesting) and motor mode (augmentation). The joint selector mechanism enables this single unit to be dynamically connected to different joints, replacing what would traditionally require multiple dedicated generators for each joint.
2Adaptability or versatility
If multiple generators and joint selectors are used to harvest energy from multiple joints, then energy harvesting capability is improved, but metabolic cost increases
Solution Approach 1:
The single motor-generator unit with joint selector capability reduces the number of components the user must carry and manage, directly reducing metabolic cost. The unit can be dynamically switched between harvesting mode (generating power) and motor mode (providing assistance), allowing the system to adapt to varying terrain conditions and user needs without requiring multiple dedicated systems.
Solution Approach 2:
The joint selector mechanism dynamically reconfigures the mechanical connection between the motor-generator and different joints based on real-time conditions such as terrain grade and user activity. This dynamic switching allows the system to optimize performance for current conditions while minimizing weight and metabolic burden, as the same hardware adapts its configuration rather than requiring separate systems for different scenarios.
3Weight of moving object
If a single motor-generator is used to selectively harvest from one joint, then device weight is reduced, but adaptability to multiple joints decreases
Solution Approach 1:
The joint selector acts as an intermediary mechanical device that enables a single motor-generator to be connected to multiple different joints. This selector mechanism serves as a mediator between the fixed motor-generator unit and the variable joint connections, allowing dynamic reconfiguration without requiring multiple generators. The selector transmits mechanical power selectively based on control signals, providing multi-joint adaptability through a single intermediate switching component.
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 solution reduces weight and metabolic cost by using a single motor-generator and joint selector, optimizing energy harvesting and augmentation based on terrain, thereby reducing the overall metabolic burden on the user.
Implementation Method 1
a generator driven by joint motion is coupled to an electrical load
Implementation Method 2
Generator torque developed by a harvesting generator always counteracts or opposes motion of a body segment
Data Source
AI summary
A device that attaches to three body segments connected by two joints harvests energy selectively from one of the two joints using a single motor-generator. The device also selectively augments relative body segment motion about one of the two joints. Selection of the harvesting or generating mode depends on the user's preference. When in a particular mode, the device automatically selects which of the two joints to connect to the motor-generator in order to optimize the augmentation or harvesting. Depending on whether the user is on flat terrain, going up an incline or down a decline, the selection of the joint to be connected is different. Use of a single motor-generator and gearbox mounted near the knee reduces metabolic cost compared to the use of two motor-generators and gearboxes.