IK Motion Retargeting for Loop Robots Without Singularity Failures
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Solution Overview
Problem
Robots with kinematic loops offer superior mechanical performance but face challenges in modeling and control, limiting their widespread use due to complexity and the need for custom modules, which restricts mechanical design and increases processor intensity and costs.
Innovation Solution
A versatile inverse kinematics (IK) controller is developed that includes an IK module for precise control of end effectors and center of mass, addressing kinematic singularities and enabling the retargeting of motions onto robots with or without loops, using a regularizer to circumvent velocity singularities and ensure physically feasible motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a versatile IK formulation is implemented to retarget motions onto robots with kinematic loops, then motion retargeting capability is improved, but device complexity increases
Solution Approach 1:
The IK module is designed to handle multiple robot types (kinematic trees and kinematic loops) using a unified formulation, making it universally applicable across different robotic systems without requiring type-specific custom modules
Solution Approach 2:
The controller is segmented into distinct functional modules: the IK module for motion retargeting, the regularizer for singularity handling, and the constraint satisfaction component. This modular architecture manages complexity by separating concerns while maintaining versatility
2Manufacturing precision
If custom modules are written for every submechanism type, then modeling accuracy is improved, but ease of manufacture deteriorates
Solution Approach 1:
A single versatile IK module replaces the need for custom modules for each submechanism type, maintaining modeling accuracy through a unified mathematical formulation that works for both kinematic trees and loops without restricting mechanical design choices
Solution Approach 2:
Instead of creating custom modules for each mechanism type and then adapting them, the approach inverts the process by creating a general-purpose IK formulation that naturally handles all mechanism types, eliminating the need for adaptation
3Reliability
If regularizer is used to circumvent kinematic singularities, then reliability is improved, but use of energy increases
Solution Approach 1:
The regularizer applies a small corrective force just enough to keep the system away from singularities without over-correcting. This partial action maintains reliability by preventing singularity-related failures while minimizing the energy expenditure required for the correction
Data Source
AI summary
A new controller for use in robots with kinematic loops as well as in most other types of robots (such as those with fully actuated kinematic trees). The controller includes an inverse kinematics (IK) module that implements a versatile IK formulation for retargeting of motions, including expressive motions, onto mechanical systems (i.e., robots with loops and/or without loops). Further, the controller is configured to support the precise control of the position and orientation of end effectors and the center of mass (CoM) (such as of walking robots). The formulation of the algorithms carried out by the IK module safeguards against a disassembly when IK targets are moved outside the workspace of the robot. A regularizer is included in the controller that smoothly circumvents kinematic singularities where velocities go to infinity.