Virtual Slot Control for Dense Independent Cart Throughput
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Solution Overview
Problem
Existing independent cart systems face reduced throughput due to increased spacing between movers to avoid collisions, especially when carrying payloads, which necessitates slower deceleration rates and longer stopping distances.
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 close proximity, thus coordinating traffic flow to enhance throughput without collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If increased spacing is maintained between movers to avoid collisions, then collision safety is improved, but throughput is reduced
Solution Approach 1:
The system segments the track into multiple virtual slots that are spatially distributed along the track. Each mover is assigned to a specific virtual slot, creating discrete segments for individual mover travel. This segmentation allows multiple movers to occupy different segments simultaneously, increasing throughput while maintaining safety through structured spacing.
Solution Approach 2:
The virtual slots are not static positions but dynamic references that move along the track with a defined throughput velocity. This dynamic characteristic allows the spacing between movers to be maintained relative to moving reference points rather than fixed positions, enabling higher throughput while preserving collision avoidance margins.
2Productivity
If high speed travel is maintained for movers, then throughput is improved, but stopping distance increases
Solution Approach 1:
The system performs preliminary assignment of movers to virtual slots before the movers actually reach the tracking zone. The controller assigns movers to specific virtual slots in advance, and the virtual slot system pre-calculates and maintains appropriate spacing. This preliminary organization ensures that when movers enter the tracking zone at high speed, they are already positioned with sufficient stopping distance margins built into the virtual slot spacing.
3Reliability
If reduced deceleration rate is used for payload-carrying movers, then payload safety is improved, but spacing between movers must increase
Solution Approach 1:
The virtual slot system acts as an intermediary between the controller and the physical movers. Rather than directly controlling each mover's deceleration based on payload conditions, the system uses virtual slots as intermediate reference points that automatically incorporate appropriate spacing margins. The virtual slots mediate the conflict by providing pre-calculated positioning references that account for reduced deceleration rates, allowing payload-carrying movers to maintain safer spacing without manual intervention.
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
The synchronized operation of virtual slots enables movers to be packed more densely, increasing overall throughput by reducing the need for excessive spacing between them, even when carrying payloads.
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.
Data Source
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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.