Multi-Robot Motion Synchronization Using Run-Ahead Limits
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Solution Overview
Problem
In industrial robot manufacturing, especially in robot cells where multiple robots work together, existing methods struggle to synchronize motion sequences effectively while preventing collisions, as unplanned deviations from ideal conditions often occur, leading to the need for costly continuous 3D collision testing.
Innovation Solution
A method where robot controllers calculate and adjust path speeds based on 'run-ahead limits' determined from path parameters, allowing for anticipatory adjustments to prevent collisions by exchanging information on current positions and using anticipatory maximum run-ahead times to synchronize robots' movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous 3D collision testing is performed online during robot operation, then collision prevention reliability is improved, but computational cost and system complexity increase significantly
Solution Approach 1:
The patent pre-calculates maximum run-ahead times during the offline simulation phase, storing these values for later use during online operation. This preliminary action eliminates the need for complex real-time 3D collision testing, as the pre-computed time limits directly provide collision-free operation boundaries during actual robot execution.
Solution Approach 2:
The patent segments the continuous collision prevention problem into discrete time-based intervals by calculating maximum run-ahead times at specific simulation points. Instead of continuously testing for collisions, the system divides the operation into time segments where each segment's safety is guaranteed by the pre-calculated run-ahead limit, reducing computational burden.
2Reliability
If robot motion sequences are strictly synchronized according to simulation plans, then collision prevention is improved, but adaptability to unplanned deviations deteriorates
Solution Approach 1:
The patent introduces dynamic adaptability by allowing robots to deviate from their planned motion sequences within dynamically calculated time boundaries. The maximum run-ahead time acts as a flexible constraint that adapts to real-time conditions, enabling robots to speed up, slow down, or perform subordinate tasks as long as they remain within the pre-calculated safe time window, thus balancing collision prevention with operational flexibility.
Solution Approach 2:
The patent changes the control parameter from strict time-synchronization to time-boundary-constrained execution. Instead of requiring robots to follow exact timestamps from simulation, the system transforms the constraint into a maximum time deviation parameter (run-ahead time), allowing parameter variations within safe limits while maintaining collision-free operation.
3Manufacturing precision
If robot controllers exchange position information and calculate run-ahead limits online, then synchronization accuracy is improved, but communication and processing requirements increase
Solution Approach 1:
The patent performs the computationally intensive calculations of maximum run-ahead times during the offline simulation phase, storing results for efficient online retrieval. This preliminary computation eliminates the need for complex real-time calculations, reducing online processing energy requirements while maintaining high synchronization accuracy through the use of pre-computed time boundaries.
Data Source
AI summary
In the following, a method for synchronizing the motion sequences of at least two robots will be described. In accordance with one embodiment, the method comprises the following: During operation of a robot cell having at least two robots, a path parameter is regularly calculated for each of the at least two robots based on a current position of the respective robot and on a previously specified robot path of the respective robot. The path parameter represents the current position of the robot. Subsequently, a run-ahead limit is calculated for each robot based on the path parameters determined for the respective other robots. Based on the respective calculated run-ahead limit, the path speed of every robot can be adjusted.