Turning Considerations

"Turning scrub" refers to the friction that resists turning on a robot's drivetrain. This occurs from the wheels experiencing drag laterally as the robot completes its turn
1. Turning scrub can be reduced by reducing the length of the drivetrain/chassis, The more length, the more sideways movement is required to turn, thus increasing scrub
Slipping occurs when the wheel does not have a good grip on the terrain
1. This can be avoided by using a suspension system – such that the drivetrain and wheel conforms to the terrain shape – and by having a high sprung mass to unsprung mass ratio
2. Even better is to use a suspension system that is actively pushing the wheels into the ground, such as designs using springs
3. Wheel tread design is also crucial for providing grip to a wheel's surface such that it can catch on the edges of objects
Stalling occurs when the drivetrain is unable to overcome the turning scrub it experiences
1. This means the gearing on the drivetrain motors is too low, as it is not producing enough torque
2. Stalling can be avoided by calculating the required torque for overcoming the highest scrub event (i.e. when performing a one-sided turn)

University of Waterloo Robotics Design Team