Exoskeleton Ankle Robot Torque Control via Servomotor
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Solution Overview
Problem
Current gait rehabilitation devices, particularly ankle-foot orthoses (AFOs), fail to provide effective active assistance and adaptability to different walking conditions for stroke survivors with drop foot, often being cumbersome, restrictive, or lacking in torque generation, especially during push-off, and are not suitable for unilateral assistance.
Innovation Solution
A compact and portable exoskeleton ankle robot with a gear transmission system, powered by a servomotor, and equipped with sensors and a control algorithm that provides active torque assistance and adapts to various walking conditions, including stair ascent and descent, using lightweight materials and wireless communication for unmodified shoe compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If passive or semi-active AFO is used, then the device structure is simple, but it cannot provide active torque assistance especially during push-off
Solution Approach 1:
The patent replaces traditional passive mechanical spring-damper systems with an active electrical motor system. The servomotor provides controlled torque assistance during different gait phases, particularly during push-off, replacing the limited mechanical energy storage and release mechanisms of passive AFOs.
Solution Approach 2:
The device incorporates sensors that detect user gait phase and automatically trigger appropriate torque assistance without external control. The system serves itself by sensing the user's movement state and autonomously providing the necessary mechanical assistance.
2Ease of operation
If traditional AFO is used, then the device is simple to manufacture, but it is cumbersome and restrictive
Solution Approach 1:
The AFO is divided into separate functional modules: a motor module, sensor module, power module, and structural brace. This segmentation allows each component to be optimized independently and facilitates easier assembly, adjustment, and maintenance while reducing overall bulk.
Solution Approach 2:
The device transitions from a static, rigid structure to a dynamic system that actively adapts its mechanical properties in real-time. The motorized joint provides variable impedance control, allowing the device to be compliant during swing phase and stiff during stance phase, improving comfort and usability.
3Adaptability or versatility
If bilateral gait assistance is provided, then the device can assist completely paralyzed patients, but it is not suitable for unilateral assistance needs of stroke survivors
Solution Approach 1:
The device is designed as a universal platform that can be configured for unilateral or bilateral application. The same motorized AFO design can be applied to one or both legs, allowing stroke survivors with unilateral impairment to use only the affected side while maintaining the option for bilateral use if needed.
4Ease of operation
If the actuator rotation axis is not optimized, then the device structure is simple, but the device becomes cumbersome and requires modified shoes
Solution Approach 1:
The actuator rotation axis is repositioned from the traditional ankle joint center to a location on the lateral aspect of the lower leg. This dimensional repositioning allows the motor to be mounted externally without interfering with shoe wear, while the torque is still effectively transmitted to the ankle joint through the lever arm of the tibia.
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 device offers effective gait assistance by actively supporting ankle joint movement, enhancing walking speed and stability, and reducing energy expenditure, while being lightweight and untethered for improved usability and comfort.
Implementation Method 1
an actuator receiving power from a power source and generating torque driving the articulated joint to produce relative rotatory movement between the leg brace and the foot piece
Implementation Method 2
a gear transmission system coupling to the articulated joint transmitting rotation axis of the actuator
Data Source
AI summary
A portable electrical motor-driven exoskeleton ankle joint robot with gear transmission and control system which is intended to provide walking assistance in different speed and walking conditions to persons with disability in walking or muscle weakness or joint problem.