Floor Reaction Force Estimation for Two-Legged Walking Mobile Body
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Solution Overview
Problem
Existing methods for estimating floor reaction forces in two-legged walking mobile bodies, such as humans, often result in discontinuous and fluctuating estimates, particularly during transitions between one-leg and two-leg supporting states, due to sensitivity to disturbances and inaccuracies in acceleration sensor outputs.
Innovation Solution
A method that involves measuring joint displacements, calculating center-of-gravity locations using a rigid link model, and determining floor reaction force components by considering the total rate of change of angular momentum, ensuring smooth and continuous estimation of floor reaction forces by regulating the direction of these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the direction of floor reaction force is determined by relative positional relationship between center-of-gravity and ankle joint in two-leg supporting state, then the estimation method is simple, but the estimated value changes discontinuously when transitioning between one-leg and two-leg supporting states
Solution Approach 1:
The patent applies dynamics by making the determination criterion for floor reaction force direction changeable based on the supporting state. The system dynamically switches between two determination methods: using relative positional relationship in two-leg supporting state and using acceleration sensor output in one-leg supporting state, thereby maintaining continuity and reliability of estimated values during transitions.
Solution Approach 2:
The patent changes the parameter used for determining floor reaction force direction based on the supporting state. In two-leg supporting state, the parameter is the relative positional relationship between center-of-gravity and ankle joint, while in one-leg supporting state, the parameter is the acceleration sensor output direction. This parameter change resolves the discontinuity issue.
2Speed
If acceleration sensor output is directly used to determine floor reaction force direction in one-leg supporting state, then the estimation responds quickly to motion changes, but the estimated value fluctuates suddenly due to disturbances
Solution Approach 1:
The patent introduces an intermediary mechanism by determining the floor reaction force direction based on acceleration sensor output in one-leg supporting state, rather than directly using it. This intermediary determination method filters out some disturbances while maintaining responsive behavior, balancing speed and reliability.
3Adaptability or versatility
If different methods are used to determine floor reaction force direction in one-leg and two-leg supporting states, then each method is optimized for its state, but the overall estimation shows discontinuous changes at state transitions
Solution Approach 1:
The patent makes the determination method dynamic by switching between different methods based on the supporting state. The system automatically selects the appropriate method (relative positional relationship for two-leg state, acceleration sensor output for one-leg state), ensuring both state-specific optimization and continuity across transitions.
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
This approach prevents sudden changes in the direction of estimated floor reaction forces, enabling smooth and continuous estimation, thereby improving the accuracy of joint moment calculations without the need for force sensors or force plates.
Implementation Method 1
an acceleration sensor for sequentially measuring an acceleration of the two-legged walking mobile body
Implementation Method 2
joint displacement sensors for sequentially measuring displacements of a plurality of predetermined joints including at least a hip joint and a knee joint
Data Source
AI summary
The direction of a component vector on a plane perpendicular to a predetermined axis of a floor reaction force acting on landing legs of a two-legged walking mobile body is determined such that the direction of a moment generated around a center-of-gravity of the body by a total sum of the component vectors on the plane is coincident with the direction of the component around the predetermined axis of a total rate of change of angular momentum by calculating the total rate of change of angular momentum, and the total floor reaction force acting on the body by sensing joint displacement, acceleration, angular velocity, and using a rigid link model. An estimated value of the component vector is found based on the determined direction and the obtained total floor reaction force. This enables finding an estimated value of the floor reaction force showing a smooth and continuous change.