Parking and Delivery Contest

Objective

This discipline uses the mecanum wheels’ ability to move sideways (strafe) and requires that motion to be driven programmatically – by custom code, not manual buttons. The goal is to learn the principle of omnidirectional motion and the motor calibration needed for precise straight-line strafing.

Mecanum wheels – principle of sideways motion

Each of the four wheels has rollers set at a 45° angle. By combining the spin direction of the individual wheels, several types of motion can be produced: straight forward/backward driving (all wheels the same direction), pure sideways motion – strafing (diagonal wheel pairs spinning in opposite directions), and rotation in place (the left and right sides spinning in opposite directions).

Programmatic control

Because this discipline requires programmatic (not manual) control of the sideways motion, competitors prepare their own script that sends commands over an https bridge or calls the motor driver functions directly for each named wheel (LeftFront, RightFront, LeftBack, RightBack). The script typically first brings the robot close to the parking zone and then performs a controlled sideways motion into the zone.

Motor calibration – why and how

Because of small manufacturing differences between the individual DC motors, differing friction, and battery voltage fluctuations, sending the same PWM signal to all four motors does not always guarantee purely straight sideways motion – the robot may drift or veer slightly. Recommended calibration procedure:

• Set the same PWM/duty cycle for all four motors (for example, a command for strafing right).
• Measure the robot’s actual motion – direction, distance traveled, and any rotation (a test distance of around 1 m is recommended).
• If the deviation from a straight path is greater than the chosen tolerance, adjust the PWM ratio between the individual motors (correct in small steps, e.g. about 5%).
• Repeat the measurement and adjustment until the motion settles within tolerance.
• Save the resulting correction coefficients in the robot’s configuration so they are applied automatically to every subsequent command.

Parking zone and delivery rules, scoring

• The parking zone is marked with tape only about 10-15 cm wider than the robot and is accessible only by sideways motion – the front is blocked by a tape barrier.
• At the start of the attempt the robot carries a small payload, which must be delivered to the marked delivery zone using sideways motion.
• Time limit: 5 minutes.
• Points for parking successfully within the zone boundaries, with a bonus for centering accuracy.
• Points for successfully delivering the payload to the delivery zone.
• Penalty for using manual control or any motion other than strafing when entering the parking zone, since this discipline specifically tests programmatic control of sideways motion.
• Penalty for touching the zone’s boundary tape.