Gait Assist Control Using Thigh Phase Estimation
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Solution Overview
Problem
Conventional gait motion assisting devices face challenges in accurately identifying gait states due to noise components and time delays, particularly when users with paralysis or leg disabilities attempt to perform gait motions, as they often rely on detecting lower leg movements that are incapable of normal gait, leading to inadequate assisting force provision.
Innovation Solution
A gait motion assisting device that includes a thigh orientation detecting means, a thigh phase angle calculating means using a pendulum movement model and state estimator, and an assisting torque calculating means to replicate leg movements around the hip joint, allowing for accurate calculation of the thigh phase angle and torque values to be applied by an actuator, thereby providing suitable assisting force while minimizing time delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-pass processing is applied to remove noise components, then measurement precision improves, but time delay occurs and productivity deteriorates
Solution Approach 1:
The patent substitutes the time-consuming low-pass filtering process with a state estimation approach. The state estimator provides smooth, noise-reduced estimates of hip joint angle and angular velocity without introducing the time delays characteristic of low-pass filters, thereby maintaining both measurement precision and real-time responsiveness.
2Device complexity
If lower leg angle sensor is used to detect gait motion state, then device complexity is reduced, but reliability deteriorates for users with paralysis
Solution Approach 1:
The patent inverts the conventional approach by detecting thigh motion (which remains functional in paralyzed users) instead of lower leg motion (which is impaired). By placing the sensor on the thigh and detecting hip joint angle, the system identifies gait motion states based on the upper leg's movement pattern, which is preserved even when the lower leg cannot perform normal gait motions.
Solution Approach 2:
The patent uses the thigh's motion as a proxy or copy for identifying overall gait state. Since the thigh's swing motion correlates with the gait cycle even when the lower leg is paralyzed, the system copies the functional information from the healthy thigh motion to infer the gait state that would otherwise be detected from the impaired lower leg.
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 effectively imparts suitable assisting force during a gait cycle by accurately estimating hip joint angles and angular velocities, reducing noise components and time delays, and providing appropriate support to users with gait impairments.
Implementation Method 1
the thigh phase angle calculating means replicates movement of the user's leg including a thigh and a lower leg around a hip joint by pendulum movement of a rod-like rigid body having a predetermined length l, wherein a distal end part of the rod-like rigid body has a material point having a predetermined mass m and a proximal end part of the rod-like rigid body serves as a swing center
Implementation Method 2
an actuator for imparting assisting force to a gait motion of a user... an assisting torque calculating means having an output pattern data directly or indirectly defining a relationship between the thigh phase angle and a torque value that should be output by the actuator
Data Source
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AI summary
The gait motion assisting device (1) according to the present invention replicates movement of user's leg including thigh and lower leg around hip joint by pendulum movement of a rod-like rigid body, estimates hip joint angle and hip joint angular velocity of thigh calculated based on equation of motion of the pendulum movement by a state estimator using angle-related signal received from a thigh orientation detecting means (510) as the observation, calculates the thigh phase angle using the estimated hip joint angle and the estimated hip joint angular velocity, and outputs assisting force having torque value calculated based on the thigh phase angle.