Advanced Line Following

revised 5-15-15

These rules were created by the Portland Area Robotics Society (PARTS) for their annual PDXBOT. The Seattle Robotics Society (SRS) has made adjustments to some of the criteria, but basically the rules are identical

Object

Robots will follow a line from a starting location to a finish location. The robot that accomplishes that goal in the shortest time is the winner.

Race Categories

There are two race categories: Line Following and Advanced Line Following. The Line Following course is a 3/4″ non-crossing line with curves no tighter than 6″ in radius. The Advanced Line Following course has a combination of a 1/4″ wide line and ¾” wide line and has a number of hazards including breaks in the line, line crossings, different colored line, and inclines to navigate. From here on, this document only discusses the Advanced Line Following rules.

Robot Specifications

Robots must be autonomous. Data links to off-board computers are not allowed, but wetware (human) operated remote controls will be permitted.

The length, width, height, and weight of a robot are not specified in this contest. The only requirement is that the robot must remain on the course during the event. It is the designers’ responsibility to design the robot to accomplish its task.

No robot that is deemed by race officials to be harmful or damaging to either people or the course will be permitted.

Track Specifications

  • The track surface is a minimum of 11.5″ (292 mm) wide.
  • The track surface is white. This year’s course will be cut from Collegewood brand “polar white” melamine coated hardboard, available in 3’x7’x1/8″ sheets from Home Depot and other sources. This is the same surface that is used in Portland Robotics’ PDXBOT.
  • The track surface is assembled from 11.5″ (292-mm) wide sections.
  • The track surface may have discontinuities, not to exceed 1/10″ at segment joints.
  • The course line is 1/4″ wide +/- 1/16″. It will be made of standard 3M vinyl electrical tape, 3M splice tape (thicker and stretchier for curves) and/or 2″ Pro-Pak plumbers tape on curved sections (tests show little or no difference in reflectance between these tapes). Plumbers’ tape usually has white writing on its surface. This can be easily removed by wiping the tape with a rag dampened with acetone.
  • The course line may have discontinuities, not to exceed 1/10″.
  • The course line may be curved. Right angle turns may be expected.
  • The robot must deal with the lighting conditions as they appear. That is, room lighting and window drapes will be set as desired by the judges and will not be modified for individual contestants. Also, flash photography and IR focusing cameras will be allowed, unless the judges deem such activities as interfering with the ability to hold the event in general.
  • Note: the figure above is just an example — the courses will be different the day of the event.

The Advanced Line Following course will have challenges, including some or all of the following:

  • Tight turns: Robots will be expected to navigate turns of up to 90 degrees.
  • Breaks in line: There may exist missing line segments approx. 0.25″ to 1″ long. If the robot drives straight, it will reach the next segment. This will only be in a straight section of the course.
  • Thickening of line: A line can vary from 0.25″ to 0.75″.
  • Line crossings: Robots may have to cross lines at right angle to robot motion.
  • Ramp: Robots will be expected to navigate ramps both ascending and descending. The maximum slope of an ascending ramp shall be 1 in 8. The maximum slope for a descending ramp shall be 1 in 6. The radius of vertical transitions shall be no sharper than an 18″ radius. The maximum ramp height may be up to 12″. A typical transition will be from 0″ to 6″ to 0″ in about 7 linear feet.
  • Colored line: The course line may change to a different color for part of its length.

Race Operations

A sample track will be available for “test drives” prior to the competition, to perform testing and calibration.

All robots must be ready to run at the start of the contest. The order of running will be randomly assigned. Before the contest starts, all contestants are invited to examine the course. Any issues the contestants have with the course (smudges, uneven surfaces, etc.) must be brought to the attention of the judges at this time.

When it is his or her turn, a contestant may perform a quick calibration (e.g. metering black and white etc.) before starting the run. The contestant starts a match by pressing a start button. Timing of the run will begin when the robot crosses the “START” line.

Once a match has started, no contestant or official may touch the track or interfere with the robots in any way except to reset a robot as stated below. Resets are done only by the race official.

If time permits, after all robots have made one run, robots may make a second run. The score for each robot will be the better of its two scores. No robot modifications are permitted between runs!

Race Scoring

Races are run as solitary timed events. The robot with the lowest total time wins the match.

The time is to the start/end line after the specified number of laps.

After the initial start, a contestant may not operate a robot. All manipulation of the robot is to be done only by the tournament official.

A machine that has no part of its structure over the course line, or is clearly not steering in response to the course line, is no longer tracking the course line.

An official may reset a machine that is no longer tracking the course line.

Resetting a machine onto the course incurs a 5-second penalty (plus how ever much time it takes the official to replace it). Placement is to be at the previous turn or hazard.

Decisions regarding whether a machine is tracking the course line are made only by a track official.

A robot’s run ends when it has completed the course, or it is deemed by the official to be unable to track the line, or at the end of 3 minutes.

Some races may offer time reductions for achieving secondary objectives (for example, lap-counting). These will be posted before the race.

Some races may use alternative elimination methods. These will be posted before the race.

Final scoring

Accuracy in completing the event is ranked above speed.

Final scoring shall be as follows:

Entries that have completed the course with no penalties shall be ranked in order of fastest time.

Then:

Entries that have been assessed penalties shall be ranked in the order of lowest combined time and penalty points.

If no robots complete the course, the robots shall be ranked by total distance traveled before the first reset, as determined by the match official.

Hints

  • Keep your robot wheel base short to avoid problems with vertical transitions. For the same reason, avoid long overhangs to the front and rear of your robot.
  • Keep your line sensors in line with either the front or rear contact patches of the robot. If you don’t, your sensors will vary in distance from the track in the transition areas and give false readings in vertical transition areas.
  • Make some effort to shield the sensors from camera lights and IR focusing cameras. A flexible skirt around the sensors may help.
  • Get a piece of white Melamine, some tape, and PRACTICE.

Make sure you can calibrate your sensors at the event. Lighting conditions are sure to be different than in the Bat Cave