Evacuation zone strategy: where Rescue Line matches are won

You can follow the line flawlessly and still lose. The evacuation zone concentrates most of the available points into the hardest part of the course: an open arena, no line, victims to find and rescue. Here's how to think about it strategically.

The problem in three parts

Navigation. Without a line, the robot needs another way to move purposefully. The classic approach is wall following: hug the perimeter with side distance sensors, which guarantees systematic coverage. Camera-based teams navigate toward detected targets directly. Whatever you choose, handle the entry transition explicitly, the robot must know it has entered the zone (the entrance marker and the sudden absence of line are your signals) and switch behaviour completely.

Detection. Silver balls are reflective, black balls absorb light, both stand out to a camera with basic blob detection. Sort your targets: living victims (silver) are usually worth more, so collect them first when the rules reward it. If you run without a camera, systematic sweeps with distance sensors can work, but expect to trade time for coverage.

Manipulation. The gripper is where mechanical design pays off. Proven patterns: scoop-and-lift designs that trap the ball against the chassis, rotating claw arms, and roller intakes that swallow the ball. The common failure isn't grip strength, it's alignment tolerance. Design a mouth wide enough that a few centimetres of positioning error still ends in a capture.

Time budget

Runs are time-limited, so decide in advance how the run splits between line and zone. If your line following is reliable, push speed there to buy zone time, a rushed evacuation attempt that drops balls scores less than a calm one that rescues fewer but banks them.

Practice the zone in isolation

Most teams practice full runs, so their robot sees the evacuation zone a handful of times per session. Build a standalone zone mock-up and run only the zone in a loop. A hundred repetitions of the hard part beats twenty repetitions of the whole course. That's the entire secret: the evacuation zone rewards whoever has failed in it the most times before competition day.