Editorial Feature

Types of Locomotion from Start to Finish: Wheeled Motion

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Sep 22 2014

Image Credits: Tatyana T Tomsickova/shutterstock.com

Wheeled motion is the most popular locomotion mechanism in robotics. This mechanism enables a robot to move rapidly and requires less energy when compared to other types of robotic locomotion mechanisms. In addition, the wheeled mechanism is easy to control due to its good stability and the simplicity of the mechanism.

There are different variations of wheeled robots. In general, these robots are less resistant to derailing and consume less power while using narrow wheels. Large wheels with a rough surface pattern on the other hand, are well-suited for uneven or soft-ground surfaces.

Basic Principle of Wheeled Locomotion

Wheels are available in various dimensions and sizes depending on the requirements of the application. The following are the four primary types of wheels:

Standard wheels – characterized by two degrees of freedom and an ability to move in the forward and reverse direction. The angle between the robot frame/chassis and the wheel is constant while the center of the wheel is fixed to the robot frame.
Castor/Ball wheels – have total freedom of 360° and are good at balancing the robot. These wheels are provided with a spherical ball made of nylon, plastic or any hard material fixed in a holder. Castor wheels are easy to implement and have high load capacity. However, the major limitation of castor wheels is that there is a high degree of traction and therefore more power consumption.
Omni-directional wheels – attached to large wheels at an angle of 45° to form a multi-directional structure capable of moving in any direction. Omni wheels are designed such that the axis of the smaller wheels is at a right angle to the axis of the large wheels, which enables the it to rotate parallel to its axis, generating low surface resistance. These wheels are used for driving as well as steering the robot.
Orientable wheels – mounted on an omni-directional fork support. There are two types of orientable wheels; centered and off-centered. Centered wheels have a vertical axle passing through the wheel center, while the off-centered wheels have a vertical axis slightly off-centered from the its center.