Intermittent Body Motion Assistance via Periodic Power Mode Switching
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Solution Overview
Problem
Existing energy harvesting devices increase metabolic cost when muscles are in positive mechanical power mode due to generator torque opposing motion, making non-mutualistic energy harvesting inefficient.
Innovation Solution
A system that intermittently assists body segment motion during positive power modes by using a motor-generator with a mechanical linkage and circuit that supplies energy only during positive power modes, preventing energy supply during negative power modes, and allowing bi-directional energy flow to reduce metabolic cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If energy harvesting is performed during positive mechanical power mode, then electrical energy can be generated from body joint motion, but generator torque opposes muscle motion and increases metabolic cost
Solution Approach 1:
The system performs energy harvesting in periodic cycles, alternating between harvesting phases (during negative power mode) and assistance phases (during positive power mode). This periodic switching allows the system to accumulate energy during muscle-assisted phases and release it during muscle-intensive phases, resolving the contradiction between energy generation and metabolic cost reduction
Solution Approach 2:
The system recovers mechanical energy from the body joint during negative power mode when muscles are already performing decelerating work, and then discards the generator torque during positive power mode by switching to motor mode. This recovery and discarding strategy eliminates the harmful opposing torque while capturing useful energy
2Loss of energy
If generator torque is applied continuously to harvest energy, then energy can be accumulated from body motion, but muscle workload increases during positive power modes
Solution Approach 1:
The system dynamically switches between generator mode and motor mode based on the real-time power mode of the muscle. During negative power mode, the system operates as a generator to accumulate energy. During positive power mode, it switches to motor mode to provide assistance and reduce muscle workload. This dynamic adaptation resolves the contradiction between energy accumulation and muscle workload reduction
Solution Approach 2:
The system uses sensors to detect body joint position, velocity, and power mode, then feeds this information back to the control logic which adjusts the motor-generator operation accordingly. This feedback mechanism ensures energy is harvested only when it doesn't increase muscle workload, and assistance is provided only when muscles are in positive power mode
3Use of energy by moving object
If energy assistance is provided continuously to reduce metabolic cost, then muscle workload decreases, but energy efficiency is reduced by providing assistance during negative power modes
Solution Approach 1:
The system provides energy assistance periodically only during positive power modes when muscles are performing work, rather than continuously. This periodic assistance strategy ensures energy is delivered when it directly reduces metabolic cost, while avoiding waste during negative power modes when muscles are already performing decelerating work or when energy should be harvested instead
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
The system reduces metabolic cost and exertion during activities like walking, jogging, or running by providing assistance only when needed, enhancing energy harvesting efficiency and reducing muscle workload.
Implementation Method 1
a motor-generator; a mechanical linkage configured to transmit mechanical power from the motor-generator to the body segment
Implementation Method 2
Energy may be harvested from the movement of body joints of humans and other animals by converting mechanical energy derived from such movement to electrical energy
Data Source
AI summary
Motion of a body segment is assisted when the body segment is moving in a positive power mode but not when it is moving in a negative power mode. When the motion of the body segment is cyclical, for example during walking, assistance to the body segment is switched on and off throughout the cycle to correspond to positive and negative power modes respectively. Energy used to assist the body segment may be harvested from prior motion of the body segment, either in prior cycles and/or when the body segment is moving in a negative power mode. The energy used may also be harvested from other body segments. Assisting motion of a body segment may be used to reduce the metabolic cost of locomotion, or to reduce exertion, when walking, jogging, running or sprinting.