Knee Assistive Device Cable Path Management
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Solution Overview
Problem
Existing knee movement assistive devices generate undesired forces that interfere with user movement, causing discomfort and invalidating rehabilitation exercises.
Innovation Solution
A knee movement assistive device with a waist garment, calf garment, actuator, and transmission cable that transforms rotational force into tension force, using a Bowden cable and gear mechanism to provide assistive torque while minimizing direct force on the knee joint, and a chain to guide the cable path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmission cable connects the actuator directly to the calf garment to transmit actuation force, then the assistive torque is provided effectively, but undesired forces act directly on the knee joint causing discomfort and interfering with user movement
Solution Approach 1:
A chain mechanism is introduced as an intermediary between the actuator and the calf garment. The chain includes a first portion connected to the actuator and a second portion connected to the calf garment, with the portions arranged to change relative position during knee movement. This intermediary arrangement transmits the actuation force while avoiding direct application of undesired forces on the knee joint, thereby maintaining assistive torque effectiveness without causing discomfort or movement interference.
2Ease of operation
If the transmission cable is used to transmit force from the actuator to the calf garment, then the knee movement is assisted, but the device structure becomes complex and the cable path management becomes difficult
Solution Approach 1:
The transmission cable is extracted from the direct force transmission path and replaced with a chain mechanism. The chain is configured to change its arrangement during knee movement, with the first and second portions changing relative position as the knee flexes and extends. This extraction of the cable and replacement with a configurable chain simplifies the overall device structure while maintaining the ability to assist knee movement effectively.
3Power
If the actuator generates rotational force that is transformed into tension force, then the assistive device can provide the necessary torque, but the force transmission may cause incorrect user movements
Solution Approach 1:
The chain mechanism is designed to be dynamic, with the first and second portions changing their relative position according to the knee movement phase. During knee flexion and extension, the chain configuration adapts automatically, ensuring that the transformed tension force from the actuator is transmitted in a manner that guides correct user movement rather than inducing incorrect movements. This dynamic adaptation maintains reliability while preserving the rotational force transformation capability.
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 ensures high comfort and corrects user movements by providing stable assistive torque without direct knee joint interference, reducing the risk of incorrect movements.
Implementation Method 1
an actuator attached to the waist garment and comprising a driver, said driver being configured to switch between an active state, wherein the driver generates a rotational force, and an idle state, wherein the driver generates a null force, the actuator being configured to transform the rotational force of the driver in a tension force
Implementation Method 2
a transmission cable connecting the actuator to the calf garment and being configured to transmit the tension force, generated by transforming the rotational force of the driver, to foot-worn portions
Implementation Method 3
a chain comprising a modular body having a fixed end, attached to a lower frame, a free end and an upper surface connecting the fixed end and the free end, wherein: the chain is configured to switch between an initial configuration, wherein the fixed end and the free end of the modular body are at a first distance, and a limiting configuration, wherein the modular body is arranged along a curvature direction defining a curvature angle with respect to the longitudinal direction
Data Source
Figure 1
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Figure 3
AI summary
A knee movement assistive device (1), comprising: a waist garment (2) attachable to a user waist and a calf garment (3) attachable to a user calf; an actuator (4) attached to the waist garment (2) and comprising a driver (41; a transmission cable (5) connecting the actuator (4) to the calf garment (3); a chain (7) comprising a modular body (71) having a fixed end (72), attached to the calf garment (3) and a free end (73) and comprising a groove (75) defined on the upper surface (74), the transmission cable (5) being slidably channeled in the groove (75),.