Parallel Exoskeleton with Passive Springs for Metabolic Cost Reduction
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Solution Overview
Problem
Existing load-bearing exoskeletons for running and walking are heavy, inefficient, and pose safety risks due to high power requirements and complex systems, which hinder their ability to effectively support payloads and reduce metabolic costs.
Innovation Solution
The development of a parallel exoskeleton structure with passive spring elements and variable dampers that transfer payload or wearer weight to the ground, using cam mechanisms and non-conservative actuators to enhance hip flexion and maintain stability, while minimizing distal exoskeleton mass and kinematic constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional powered exoskeletons are used to support payloads and assist locomotion, then load capacity and assistive torque are improved, but system weight and power requirements increase significantly
Solution Approach 1:
The patent employs passive dynamic elements (springs and dampers) that automatically adapt to the user's motion without requiring active power input. The spring elements store and release energy dynamically during the gait cycle, providing assistive torque while keeping the system lightweight and power-free.
Solution Approach 2:
The exoskeleton utilizes the user's own motion and body weight to power the system. The passive spring-damper mechanism automatically engages and disengages based on the natural gait cycle, eliminating the need for external power sources or complex control systems while still providing load support and torque assistance.
2Force
If heavy powered systems are used to support payloads, then load capacity is improved, but metabolic cost reduction and efficiency are worsened
Solution Approach 1:
The patent employs periodic energy storage and release through spring elements that are compressed during the stance phase and release energy during the swing phase. This periodic action synchronizes with the natural gait cycle, providing load support while reducing the metabolic energy required for locomotion.
Solution Approach 2:
The passive spring mechanism recovers energy that would otherwise be lost during the gait cycle. By storing energy during energy-absorbing phases and releasing it during energy-requiring phases, the system reduces the overall metabolic cost without requiring active power input.
3Force
If complex actuation systems are used to assist locomotion, then assistive torque is improved, but device complexity and safety risks increase
Solution Approach 1:
The patent extracts the active power and control systems from the exoskeleton, leaving only passive mechanical elements (springs and dampers). This simplification removes safety risks associated with powered systems while maintaining the ability to provide assistive torque through carefully designed mechanical properties.
Solution Approach 2:
The patent replaces complex, expensive, and potentially hazardous powered actuation systems with simple, robust, and safe passive mechanical elements. The spring-damper system is inherently safer and more reliable while achieving the same functional goal of providing assistive torque during locomotion.
4Force
If the exoskeleton transfers payload weight to the ground, then load support is improved, but stability and wearer comfort may be worsened
Solution Approach 1:
The patent uses dynamic spring-damper elements that automatically adjust to the user's motion and terrain variations. This dynamic adaptation allows the exoskeleton to transfer payload weight to the ground while maintaining wearer stability through natural motion synchronization rather than rigid load bearing.
Solution Approach 2:
The spring-damper system acts as an intermediary between the payload and the ground, mediating the load transfer process. This intermediary mechanism smooths out force transmissions and adapts to user motion, preventing direct rigid coupling that would compromise stability while still achieving effective load support.
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 design reduces metabolic costs, enhances stability, and allows for efficient energy transfer during walking and running by mimicking natural human biomechanics, with the exoskeleton's parallel architecture and energy storage mechanisms effectively supporting loads without destabilizing the wearer.
Implementation Method 1
a spring element operatively connected between the first skeletal member and the second skeletal member for storing energy when the members move relative to one another in a first direction and for releasing energy when the members move relative to one another in a second direction
Implementation Method 2
a controllable damping element to dissipate mechanical energy and arrest the relative motion of the first skeletal member and the second skeletal member at controllable times
Data Source
AI summary
An exoskeleton worn by a human user consists of a rigid pelvic harness, worn about the waist of the user, and exoskeleton leg structures, each of which extends downwardly alongside one of the human user's legs. The leg structures include hip, knee, and ankle joints connected by adjustable length thigh and shin members. The hip joint that attaches the thigh structure to the pelvic harness includes a passive spring or an active actuator to assist in lifting the exoskeleton and the human user with respect to the ground surface upon which the user is walking and to propel the exoskeleton and human user forward. A controllable damper operatively arrests the movement of the knee joint at controllable times during the walking cycle and a spring located at the ankle and foot member stores and releases energy during walking.