Bidirectional Compliant Joint Torque Actuation for Exoskeletons
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Solution Overview
Problem
Current exoskeletons and orthotic devices are limited in their ability to provide bidirectional torque augmentation to human joints, restricting range of motion and being too heavy, which exacerbates fatigue and injury in military personnel carrying heavy loads during long marches.
Innovation Solution
A bi-directional compliant joint torque augmentation system that includes an actuation system with an actuator and springs, coupled to a lever and sensors, which measures joint position to apply assistive torque during specific phases of the gait cycle, reducing metabolic energy expenditure and allowing for a greater range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current exoskeletons and orthotic devices provide torque augmentation to human joints, then gait assistance is improved, but range of motion is restricted and device weight increases
Solution Approach 1:
The patent changes the mechanical parameters of the joint augmentation system by introducing compliant elements (springs) that allow variable torque delivery across different ranges of motion. The system transitions from rigid torque application to compliant torque application, enabling bidirectional motion assistance while maintaining adaptability to natural gait variations and different movement amplitudes.
Solution Approach 2:
The system implements dynamic torque augmentation by using sensors to detect joint position and velocity, then modulating the actuator output in real-time. The compliant mechanism dynamically adapts the torque profile during the gait cycle, providing assistance during swing phase while allowing natural motion during stance phase, thus improving both gait assistance and range of motion adaptability.
2Productivity
If current exoskeletons and orthotic devices provide torque augmentation to human joints, then gait assistance is improved, but device weight increases which exacerbates fatigue
Solution Approach 1:
The system employs passive compliant elements (springs) that store and release energy during the gait cycle without requiring active power input. The springs self-regulate the torque delivery based on joint position and velocity, reducing the power requirements of the active actuator and enabling a lighter overall system design while maintaining effective gait assistance.
Solution Approach 2:
The system delivers torque assistance periodically during specific phases of the gait cycle (primarily swing phase) rather than continuously. The compliant mechanism naturally cycles through compression and extension as the joint moves, allowing the actuator to operate in intermittent bursts rather than continuous mode, which reduces energy consumption and enables lighter battery and actuator sizing.
3Productivity
If current exoskeletons and orthotic devices provide torque augmentation to human joints, then gait assistance is improved, but the system interferes with natural range of motion
Solution Approach 1:
The system changes from rigid torque application to compliant torque application, allowing the joint to move through its natural range of motion while receiving assistance when needed. The compliant elements enable variable stiffness that adapts to the user's movement intentions, preserving natural gait patterns while providing productivity benefits.
4Quantity of substance
If soldiers carry heavy loads for long distances, then mission capability is maintained, but fatigue and injury risk increase
Solution Approach 1:
The system provides counter-torque at the joint to offset the gravitational effect of the carried load during swing phase. The actuator generates an opposing moment that compensates for the weight-induced resistance to limb acceleration, effectively reducing the metabolic cost of carrying heavy loads over long distances and lowering fatigue and injury risk.
Solution Approach 2:
The system applies torque assistance before the limb would naturally decelerate during swing phase, helping to maintain momentum and reduce the effort required from the user's muscles. By providing preliminary acceleration assistance, the system enables soldiers to carry heavier loads without experiencing the same level of fatigue and injury risk.
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 effectively reduces metabolic energy consumption and enhances gait efficiency, enabling soldiers to carry heavy loads for longer distances without fatigue, while maintaining natural range of motion and comfort.
Implementation Method 1
A compliant mechanism includes a motor-driven screw, a spring, and a lever arm
Implementation Method 2
A compliant actuation assembly includes a motor-driven screw, a spring, and a lever arm that rotates about a system joint
Implementation Method 3
A position sensor is disposed on the system joint to determine a position of the system joint
Data Source
AI summary
A joint actuation device for adding torque to a joint of a user includes an actuation system having an actuator and a spring. A lever is configured to couple to the user's leg and to the actuation system. The lever configured to rotate at a device joint with respect to the actuation system. A first sensor measures a position of the device joint. A second sensor measures deflection in a spring. The actuator is positioned based on the position of the device joint and deflection in the spring. The actuator is configured to deflect the spring to apply a torque the device joint. The device joint aligns with the user's joint to add a torque to the user's joint during a gait activity. The actuator disengages the spring during a non-gait activity. The lever is configured to disengage from the actuator when the device joint exceeds a predetermined angle.