Generalized Coordinate Surrogates for Stable Legged-Robot Foot Placement
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Solution Overview
Problem
Existing robotic systems face challenges in maintaining balance and efficient movement, particularly in legged robots, as they transition between stance and swing phases during locomotion, leading to instability and inefficiency.
Innovation Solution
Implementing a 'touch-down lift-off' (TDLO) control procedure that determines the position of a swing leg based on measurements of the stance leg's touch-down and lift-off relative to the robot's center of mass, using sensors and actuators to adjust leg placement for balance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional balance control methods are used in legged robots, then the control system is simpler, but the robot experiences instability and inefficiency during transitions between stance and swing phases
Solution Approach 1:
The patent implements dynamic control by continuously adjusting leg placement based on real-time measurements of center of mass position and velocity. The TDLO control law dynamically computes optimal foot placement locations during locomotion, allowing the robot to adapt to varying terrains and maintain balance stability while managing control system complexity through systematic dynamic adjustment.
Solution Approach 2:
The patent employs feedback control by using measurements from sensors (such as center of mass position and velocity) to inform the TDLO control law, which then determines optimal leg placement. This closed-loop feedback mechanism enables the robot to correct balance deviations and maintain stability during transitions between stance and swing phases, directly addressing the reliability issue.
2Reliability
If leg placement is optimized for balance, then stability improves, but movement efficiency may be reduced due to additional control computations
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the TDLO control law relationships between center of mass states and optimal foot placement locations. During actual locomotion, the controller only needs to evaluate the pre-computed control law with current measurements, rather than performing complex optimization computations in real-time, thus maintaining movement efficiency while achieving optimized leg placement for balance.
3Measurement precision
If the robot uses more sensors and actuators for precise leg placement control, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the control system to process measurements from standard sensors (such as inertial measurement units and force sensors) for multiple purposes: determining center of mass position, calculating velocity, and computing optimal foot placement locations. This universal approach allows the same sensor suite to support precise leg placement control without requiring additional specialized sensors, thus improving measurement precision while limiting device complexity growth.
Data Source
AI summary
A robotic device includes a control system. The control system receives a first measurement indicative of a first distance between a center of mass of the machine and a first position in which a first leg of the machine last made initial contact with a surface. The control system also receives a second measurement indicative of a second distance between the center of mass of the machine and a second position in which the first leg of the machine was last raised from the surface. The control system further determines a third position in which to place a second leg of the machine based on the received first measurement and the received second measurement. Additionally, the control system provides instructions to move the second leg of the machine to the determined third position.