Lower Extremity Exoskeleton Hip Actuator Torque Control
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Solution Overview
Problem
Existing lower extremity exoskeletons fail to reduce the energy consumption of their wearers, as they either lack actuation or provide power in opposing directions, thereby increasing energy expenditure.
Innovation Solution
A lower extremity exoskeleton with two leg supports, knee joints, an exoskeleton trunk, and hip actuators powered by a power unit, which creates a torque profile that transfers energy to the wearer during the stance phase, reducing the energy required for locomotion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a quasi-passive exoskeleton with springs is used for load-carrying augmentation, then structural support is provided, but the wearer's oxygen consumption increases
Solution Approach 1:
The exoskeleton harnesses the wearer's own motion and forces to generate power through regenerative braking during descent and swing phase, storing energy in the energy storage device. This self-service mechanism allows the system to recover energy that would otherwise be lost, reducing the net energy consumption of the wearer while maintaining load-carrying capability
Solution Approach 2:
The system dynamically adjusts the torque applied by the actuator based on the phase of the gait cycle and the load being carried. By changing the torque parameter in response to varying conditions, the exoskeleton provides optimal assistance during stance phase while minimizing energy consumption during other phases, thereby reducing overall wearer energy expenditure
2Ease of operation
If a powered exoskeleton uses 'get out of the way' control method, then the exoskeleton responds to wearer's forces, but the force from exoskeleton increases the wearer's energy expenditure
Solution Approach 1:
The system continuously monitors forces applied by the wearer and uses this feedback to modulate the actuator torque. During stance phase, when the wearer applies force to push off, the system detects this and provides positive torque assistance. During swing phase, when the wearer pulls back, the system provides negative torque to assist swing. This feedback mechanism ensures the exoskeleton responds appropriately to wearer intentions while reducing energy expenditure
Solution Approach 2:
The exoskeleton applies torque in a periodic manner synchronized with the gait cycle. Positive torque is applied during stance phase to assist push-off, and negative torque is applied during swing phase to assist leg swing. This periodic action pattern matches the natural rhythm of walking, providing assistance at the right moments while minimizing overall energy consumption
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 exoskeleton decreases the wearer's energy expenditure and oxygen consumption by transferring mechanical energy during the stance phase, leading to a lower heart rate and improved load-carrying capabilities.
Implementation Method 1
the power unit is configured to cause the hip actuator of the leg support in the stance phase to create a torque profile such that the energy supplied by the power unit to the hip actuator
Data Source
AI summary
A lower extremity exoskeleton, configurable to be coupled to a person, includes: leg supports configurable to be coupled to the person's lower limbs and designed to rest on the ground during stance phases, with each leg support having a thigh link and a shank link; two knee joints, each configured to allow flexion and extension between respective shank and thigh links; an exoskeleton trunk configurable to be coupled to the person's upper body, rotatably connectable to the thigh links of the leg supports, allowing for the flexion and extension between the leg supports and the exoskeleton trunk; two hip actuators configured to create torques between the exoskeleton trunk and the leg supports; and at least one power unit capable of providing power to the hip actuators. In use, power is supplied to the hip actuators in an amount to reduce the energy consumed by a user during a walking cycle.