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Team Member
- Jaehyun Bae
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Overview
Motivation
DARPA Warrior Web Program
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- Harvard Biodesign group, one of a project groups in this program, is trying to make their warrior web suit soft and light, and they call their suit harvard exosuit.
- Experimental data proved that it can help loaded walking by reducing metabolic costs.
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Challenge
As it is a new approach to assist human gait with deformable structure, there are many challenges while developing the exosuit. The examples of the challenges are
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- The under-suit may be soft and deformable
- Hard to identify how external actuation assists loaded gait.
- Experimental metabolic cost data is inconsistent case by case
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Goals
Through this project, I tried to resolve the challenges in developing exosuit with Opensim simulation. Simulation can help developing soft wearable exosuit as it can gives an intuition on how exosuit help muscles, and what are the key features that one should care about when developing the suit.
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- Metabolic cost reduction when biarticular actuators are added to loaded gait mode
- When ankle actuator is appended: 10.35%
- When hip actuator V4 is appended: 6.62%
- When biarticular actuator is appended: 3.12%
- is 3.12% from baseline. It is much lower than reduction rate of ankle actuator or hip actuator.
- Control input is noisy, which makes it hard to realize
- Biarticular actuator is not as effective as uni-articular actuators in terms of metabolic cost reduction.
Conclusion
Featured result
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- Both hip actuator and ankle actuator can reduce the metabolic cost during walking
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- If we can apply sufficient amount of force, it is better to apply force to ankle joint.
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- If not, hip actuator is a good alternative, even though it is hard to control
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•The optimal input force for ankle actuator when it’s maximum force is bounded is similar to the general optimal input force saturated at maximum force
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•Biarticular actuator doesn’t assist loaded walking very well and the force input is not consistent.
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•Both hip actuator and ankle actuator can reduce the metabolic cost during walking
–If we can apply sufficient amount of force, it is better to apply force to ankle joint.
–If not, hip actuator is a good alternative, even though it is hard to control
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•The
- Exosuit offers greater assist for loaded walking than unloaded walking
- Optimal input of ankle actuator is consistent with gait cycle and muscle forces data, while that of hip actuator is not.
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•The simulation methodology to use CMC as an optimization tool works, but more improvement is needed.
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•Longer MA magnifies the effectiveness of Exosuit
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- The optimal input force for ankle actuator when it’s maximum force is bounded is similar to the general optimal input force saturated at maximum force
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•Exosuit offers greater assist for loaded walking than unloaded walking
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•Biarticular - Biarticular actuator doesn’t assist loaded walking very well and the force input is not consistent.
Limitations
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- The experimental data was obtained from a subject without exosuit. Exosuit may change the kinematics of a subject as well as GRF.
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•CMC - The simulation methodology to use CMC as an optimization tool works, but more improvement is needed.
- CMC process doesn’t minimize metabolic cost. Instead, it minimizes 2-norm of activation.
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•The - The experimental data is only one gait cycle.
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•More - More realistic actuator simulation is needed. (E.g. Combination of passive & active actuator
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Source code
You can find the model that I used in htt~~~~
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