Step Assist Device Phase Angle Stabilization
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Solution Overview
Problem
Conventional step assist devices fail to stabilize the phase angle of hip joint movement relative to the step period, leading to disturbances in phase changes.
Innovation Solution
A step assist device with a control system that detects hip joint angles and speeds, calculates phase angles, and modifies them using a predetermined pattern to approach a straight line over time, ensuring stable auxiliary force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a first phase oscillator based on hip joint angle period and a second phase oscillator based on left-right hip joint angle deviation are used to generate assistance torque, then the movement period of the step assist device can be balanced with the walking step period of the assisted walker, but the phase angle relative to the step period becomes easily disturbed and cannot be corrected
Solution Approach 1:
The patent changes the control parameter from raw phase angle to modified phase angle, where the modified phase angle is obtained by adding a monotonic increase value to the calculated phase angle. This parameter transformation ensures that the phase angle monotonically increases over time without disturbance, resolving the instability issue while maintaining the existing oscillator-based control structure.
Solution Approach 2:
The patent replaces the complex mechanical phase correction mechanism with a computational approach. Instead of using additional sensors or mechanical feedback systems to correct phase angle disturbances, the system uses a calculating section to compute the phase angle from hip joint angle data and a modifying section to apply the monotonic increase correction, substituting mechanical complexity with algorithmic simplicity.
2Ease of manufacture
If the phase angle is calculated based on periodic hip joint movement without modification, then the calculation is simple, but the phase pattern deviates from a straight line relative to time passage
Solution Approach 1:
The patent transforms the phase angle parameter by adding a monotonic increase value that is calculated based on the step period. This modification converts the non-linear phase pattern into a linear one relative to time, while the modification process itself remains computationally simple, requiring only basic arithmetic operations on the calculated phase angle.
Solution Approach 2:
The patent applies preliminary modification to the phase angle calculation by pre-determining the monotonic increase value based on the step period before using it in control. This preliminary action ensures that the phase pattern linearity is achieved without requiring complex real-time adjustments, simplifying the overall control algorithm.
Data Source
AI summary
Provided is a step assist device including a first phase angle modifying section that, according to repetition of the step movement, modifies in a staged manner the phase angle input thereto, based on a predetermined phase change pattern, such that a phase pattern of the phase angle approaches a straight line relative to the passage of time, and outputs the modified phase angle as a first modified phase angle. The control section acquires a target value based on a continuous change pattern of the auxiliary force set in advance for at least one of the first modified phase angle and a prescribed phase angle, and controls the providing section according to the target value.