Virtual Slot Control for Dense Independent Cart Traffic
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Solution Overview
Problem
Existing collision avoidance routines in independent cart systems require increased spacing between movers to accommodate varying deceleration rates due to payloads, leading to reduced throughput.
Innovation Solution
Implementing virtual slots along the track that are synchronized to move in unison, allowing movers to enter and exit these slots while maintaining reduced spacing, thus coordinating traffic flow and avoiding collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If collision avoidance routine increases minimum stopping distance to accommodate varying deceleration rates, then reliability is improved, but productivity deteriorates
Solution Approach 1:
The system segments the track into multiple virtual slots that are independently controllable. Each virtual slot acts as a discrete control zone, allowing the controller to manage movers in segmented portions of the track rather than treating the entire track as a single control domain. This segmentation enables localized control actions that maintain safety while preserving throughput in other areas.
Solution Approach 2:
Virtual slots serve as an intermediary control mechanism between the controller and the movers. Instead of directly controlling each mover's speed and position, the controller assigns movers to virtual slots and controls the slots themselves. This intermediary layer simplifies collision avoidance by managing spacing at the slot level rather than requiring complex real-time calculations for each mover pair.
2Reliability
If increased spacing between movers is implemented to ensure sufficient stopping distance, then reliability is improved, but productivity deteriorates
Solution Approach 1:
The system dynamically adjusts the spacing and positioning of virtual slots based on real-time conditions. Virtual slots are not fixed in space but move along the track with a controlled velocity. This dynamic positioning allows the system to maintain optimal spacing between movers while maximizing the number of movers on the track simultaneously, thereby preventing collisions without sacrificing throughput.
Solution Approach 2:
The controller changes the parameters of virtual slots (position, velocity, spacing) to optimize both safety and throughput. By adjusting the velocity and positioning of virtual slots, the system can maintain reduced spacing between movers while ensuring sufficient stopping distances are preserved through coordinated control, rather than relying on fixed increased spacing.
3Productivity
If virtual slots move along the track with synchronized velocity, then productivity is improved, but device complexity increases
Solution Approach 1:
The system merges the control of multiple movers into a single virtual slot control mechanism. Instead of independently controlling each mover's speed and position, the controller assigns multiple movers to virtual slots and controls the slots collectively. This merging reduces the overall control complexity while maintaining the ability to manage mover spacing and prevent collisions, thereby enabling improved throughput without proportionally increasing device complexity.
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
Enhances throughput by allowing movers to be packed more densely without the need for increased spacing, improving overall system efficiency.
Implementation Method 1
The track is made up of a number of track segments that, in turn, hold individually controllable electric coils. Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track.
Implementation Method 2
Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track.
Data Source
AI summary
Virtual slots are provided to coordinate traffic flow in an independent cart system. Multiple virtual slots are defined along a length of a track for the independent cart system. The track includes multiple track segments, and the independent cart system includes a linear drive system to propel movers along the track. Each of the virtual slots are controlled to travel along the length of the track. The virtual slots are spaced apart at a first distance and are controlled to travel synchronously at a desired speed. Each of the movers is controlled to travel within one of the virtual slots at the desired speed, and each of the movers has a minimum stopping distance greater than the first distance when travelling at the desired speed.