Robotic Footstep Timing Using Capture Point Balance Control
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Solution Overview
Problem
Existing robotic systems lack efficient timing mechanisms for footstep placement, relying on predetermined clock-based timing, which can lead to instability and difficulty in maintaining balance, especially when encountering disturbances.
Innovation Solution
A robotic system determines mechanically-timed footstep placement by calculating a capture point based on its center of mass position and velocity, using a linear inverted pendulum model to arrest momentum, and adjusts the timing of foot contact based on a threshold position to maintain balance and adapt to disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If predetermined clock-based timing is used for footstep placement, then the control system is simple, but the robot stability deteriorates and difficulty in maintaining balance increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the robot's center of mass position and velocity, and using this information to dynamically adjust footstep timing. The capture point calculation provides feedback about the robot's dynamic state, allowing the control system to adapt foot placement timing to maintain stability rather than following predetermined clock-based schedules.
Solution Approach 2:
The patent transitions from static predetermined timing to dynamic timing based on real-time robot state. The footstep placement timing becomes a dynamic variable that adjusts according to the capture point trajectory and center of mass dynamics, allowing the robot to adapt to disturbances and maintain balance through mechanically-timed footsteps.
2Device complexity
If predetermined clock-based timing is used for footstep placement, then the control algorithm is simple, but the adaptability to disturbances deteriorates
Solution Approach 1:
The control system uses feedback from center of mass position and velocity measurements to continuously update the capture point calculation. This feedback mechanism enables the robot to detect and respond to disturbances by adjusting footstep timing based on the actual dynamic state rather than following a predetermined schedule, thereby improving adaptability.
Solution Approach 2:
The robot performs self-adjustment by autonomously calculating its own capture point and determining appropriate footstep timing based on its current state. The system serves itself by using its own dynamic information to generate appropriate control actions, eliminating the need for external timing signals and enabling autonomous adaptation to disturbances.
3Stability of the object's composition
If mechanically-timed footstep placement based on capture point is used, then the robot stability improves, but the control system complexity increases
Solution Approach 1:
The patent replaces complex real-time dynamic control with a mechanically-inspired timing approach based on the capture point concept. By using the capture point trajectory as a natural timing reference, the system achieves stable footstep placement through mechanically-timed actions rather than complex continuous control calculations, simplifying the control architecture while maintaining stability.
4Adaptability or versatility
If mechanically-timed footstep placement based on capture point is used, then the adaptability to disturbances improves, but the computational requirements increase
Solution Approach 1:
The patent extracts the essential timing information from complex dynamic control by identifying the capture point trajectory as a natural reference signal. By taking out the capture point calculation as a separate, computationally efficient module that provides timing cues, the system achieves adaptability to disturbances without requiring heavy computational resources for continuous optimal control calculations.
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 allows for more stable and adaptive footstep timing, enabling the robot to maintain balance and adjust to disturbances without relying on predetermined timing, enhancing its operational efficiency and stability.
Implementation Method 1
A robotic system determines mechanically-timed footstep placement by calculating a capture point based on its center of mass position and velocity, using a linear inverted pendulum model to arrest momentum
Data Source
AI summary
An example implementation for determining mechanically-timed footsteps may involve a robot having a first foot in contact with a ground surface and a second foot not in contact with the ground surface. The robot may determine a position of its center of mass and center of mass velocity, and based on these, determine a capture point for the robot. The robot may also determine a threshold position for the capture point, where the threshold position is based on a target trajectory for the capture point after the second foot contacts the ground surface. The robot may determine that the capture point has reached this threshold position and based on this determination, and cause the second foot to contact the ground surface.