Independent Cart Queue Control to Eliminate Caterpillar Motion
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Solution Overview
Problem
In independent cart systems, the 'caterpillar effect' occurs due to processing delays, leading to erratic motion and reduced machine throughput, especially when dealing with multiple movers and complex motion programming, which results in potential collisions and inefficiencies.
Innovation Solution
Implementing a method where queue zones have a lead mover that dictates target positions for follow movers, using a circular stack pointer to update target positions only when the lead mover exits the zone, eliminating the need for each mover to monitor adjacent neighbors and simplifying motion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If movers monitor the location and movement of neighboring movers and plan motion based on this information, then collision prevention is improved, but processing delays occur due to processor performance constraints
Solution Approach 1:
The system divides the track into multiple queue zones, with each zone independently managed. Movers within a queue zone follow a lead mover's target position, eliminating the need for each mover to monitor all neighboring movers across the entire system. This segmentation reduces computational complexity and processing delays while maintaining collision prevention within each zone.
Solution Approach 2:
The lead mover in each queue zone acts as an intermediary that dictates target positions for follow movers. Instead of each mover directly monitoring and reacting to all neighbors, the lead mover mediates motion planning for the queue, reducing individual processor loads and eliminating processing delays while maintaining coordinated motion and collision prevention.
2Quantity of substance
If a large number of movers (over forty) are controlled using prior approaches, then system capacity is improved, but processing delays become inevitable
Solution Approach 1:
The system segments the large fleet of movers into multiple queue zones, each with its own lead mover and follow movers. This allows the system to control over forty movers without processing delays by distributing control across multiple independent zones, where each zone manages a smaller subset of movers with reduced computational requirements.
Solution Approach 2:
Multiple follow movers within a queue zone share the same target position dictated by the lead mover, merging their motion planning into a single coordinated action. This combining approach reduces the total number of independent motion planning calculations needed, allowing the system to handle a large quantity of movers efficiently without processing delays.
3Adaptability or versatility
If the primary machine controller performs a multitude of other machine functions, then system functionality is improved, but motion control of movers deteriorates
Solution Approach 1:
The motion control system is segmented into independent queue zone controllers, each managing its own lead and follow movers. This segmentation isolates motion control calculations from other machine controller functions, allowing the primary controller to perform multiple machine functions simultaneously without degrading motion control performance, as each queue zone operates independently with simplified control logic.
4Device complexity
If traditional motion programming is used with multiple movers, then system complexity increases, but the 'caterpillar effect' and erratic motion occur
Solution Approach 1:
The system segments motion programming into queue zone-level control rather than individual mover control. Each queue zone uses a simple lead-follower model where follow movers replicate the lead mover's target position, eliminating complex inter-mover monitoring and planning. This segmentation reduces programming complexity while stabilizing motion by preventing the caterpillar effect through synchronized queue-based control.
Solution Approach 2:
The lead mover in each queue zone preliminarily determines the target position for all follow movers in that zone. This preliminary action establishes a coordinated motion plan before execution, eliminating erratic motion and the caterpillar effect by ensuring all movers in a queue are pre-coordinated to move together, reducing programming complexity while improving motion stability.
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 prevents collisions and improves throughput by ensuring synchronized and efficient motion control, reducing the complexity of motion programming and eliminating the 'caterpillar effect', even at high speeds and with multiple movers.
Implementation Method 1
Successive activation of electric coils establishes a moving electromagnetic field that interacts with magnets of a mover (also referred to as a cart) and causes the mover to travel along a track.
Data Source
AI summary
A method and system for motion control of movers in an independent cart system is disclosed. In one implementation, the independent cart system includes a plurality of movers, a track including a path, and a controller coupled to the track. Each of the plurality of movers includes at least one drive magnet, and each track segment includes a plurality of drive coils and a drive coupled to the plurality of drive coils. The controller defines a queue zone for the path, the queue zone having one or more target positions; defines a circular pointer queue for the queue zone; associating the circular pointer queue with the one or more target positions of the queue zone; circulating the circular pointer queue when a lead mover leaves the queue zone; and moves the movers through the queue zone based on the circular pointer queue.