Mobile Robot Balance Control for Expressive Limb Motion
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Solution Overview
Problem
Current methods for mobile robots with multiple articulated limbs struggle to perform complex motions that combine displacement and limb movements without becoming unbalanced, especially when executing expressive behaviors like dance or interacting with obstacles, due to computational intensity and limitations in maintaining balance.
Innovation Solution
A processor-configured system that calculates a target trajectory for the center of mass and predicted movements of articulated limbs based on dynamic constraints, using a double inverted pendulum model to minimize cost functions and ensure the Zero Moment Point remains within a stable region, allowing for real-time adaptation and interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inverse dynamics is used to control all articulations to perform dance movements while following a trajectory, then the robot can execute expressive limb movements, but the computational complexity becomes too high for real-time calculation on onboard resources
Solution Approach 1:
The patent segments the control system into two independent parts: (1) a dynamic model that calculates only the center of mass trajectory and base movements, and (2) a separate inverse kinematics module that generates limb movements. This segmentation allows each module to operate with reduced computational complexity, enabling real-time processing on onboard resources while maintaining the ability to execute expressive dance movements.
Solution Approach 2:
The patent extracts the center of mass trajectory calculation from the full inverse dynamics computation. By using a simplified dynamic model that focuses only on the center of mass and base movements, the system removes the computationally intensive full-body inverse dynamics calculations, leaving only the essential balance control while enabling separate limb movement generation.
2Adaptability or versatility
If the robot executes movements of articulated limbs to perform dance or interaction behaviors, then the robot can define expressive behaviors, but the Zero-Moment Point or Center Of Mass may leave the stability region causing the robot to fall
Solution Approach 1:
The patent applies preliminary action by first calculating the center of mass trajectory and determining the required base movements to maintain balance before generating limb movements. The dynamic model predicts the center of mass position and velocity, and the controller pre-adjusts the base and trunk movements to compensate for upcoming limb movements, ensuring the Zero-Moment Point remains within the stability region throughout the dance sequence.
Solution Approach 2:
The patent uses counterweight by having the base and trunk movements compensate for the center of mass shifts caused by limb movements. The dynamic model calculates the required counter-movements of the base and trunk to offset the gravitational and inertial effects of articulated limb movements, maintaining the Zero-Moment Point within the support polygon and preventing falls during expressive behaviors.
3Reliability
If the robot follows a strict target trajectory with limited degrees of freedom, then the robot can maintain balance, but the robot cannot perform complex dance movements of articulated limbs
Solution Approach 1:
The patent applies dynamics by making the system adaptable through separate control modules. The dynamic model continuously updates the center of mass trajectory based on current state, while the inverse kinematics module dynamically generates limb movements that adapt to the available degrees of freedom. This dynamic approach allows the robot to perform complex dance movements while maintaining balance through real-time adjustments.
Solution Approach 2:
The patent achieves multi-functionality by creating a control architecture that can simultaneously handle trajectory following, balance maintenance, and expressive limb movements. The separate dynamic model and inverse kinematics modules work together to enable the robot to perform multiple functions: follow the target trajectory, maintain balance through center of mass control, and execute complex dance movements of articulated limbs independently.
Data Source
AI summary
A mobile robot is provided to follow a trajectory and adopt a behavior which can be defined by movements of articulated limbs of the robot. The mobile robot is equipped with a processor which is configured, based on instructions defining a motion of the mobile robot and instructions defining a behavior of the mobile robot, to calculate a target trajectory of a center of mass of the mobile robot; calculate, based on the target trajectory of the center of mass of the mobile robot and dynamic constraints of the mobile robot, a predicted trajectory of the center of mass of the mobile robot over a time horizon, and calculate, based on the predicted trajectory of the center of mass of the mobile robot and the instructions defining a behavior of the mobile robot, predicted movements of articulated limbs.