Click image to open full size
Wheels, Tracks, and Legs
Three movement systems compared by terrain and use
Related Tools
Related Labs
Related Worksheets
Related Cheat Sheets
Robots can move in many ways, but three common designs are wheels, tracks, and legs. Each movement system helps a robot travel across certain kinds of ground, such as smooth floors, rocky soil, stairs, or sand. Engineers choose a design by thinking about speed, stability, cost, and the environment. This matters because a delivery robot, a Mars rover, and a rescue robot all face different movement challenges.
Wheels are simple and fast on flat surfaces because they roll with little friction. Tracks spread a robot's weight over a larger area, which helps it grip rough or soft ground and climb over small obstacles. Legs can step over objects and move on stairs, but they need more sensors, motors, and computer control. A good robot design matches the movement system to the job it must do.
Key Facts
- Wheels are usually fastest and most energy efficient on smooth, flat ground.
- Tracks give more grip because they touch the ground over a longer contact area.
- Legged robots can step over obstacles, climb stairs, and balance on uneven surfaces.
- Speed = distance ÷ time, or v = d/t.
- More moving parts often means more control is needed and more chances for parts to break.
- The best robot movement system depends on the terrain, task, load, speed, and power supply.
Vocabulary
- Wheel
- A round part that turns around an axle to help a robot roll across a surface.
- Track
- A continuous belt that moves around wheels to give a robot strong grip on rough or soft ground.
- Legged robot
- A robot that uses mechanical legs to walk, step, climb, or balance.
- Terrain
- The type of ground or surface a robot must travel across.
- Traction
- The grip between a robot and the ground that helps it move without slipping.
Common Mistakes to Avoid
- Choosing wheels for every robot is wrong because wheels work best on smooth, flat ground and may get stuck on rocks, stairs, or deep sand.
- Thinking tracks make a robot faster is wrong because tracks usually improve grip and stability, but they can be slower and use more energy than wheels.
- Assuming legs are always best is wrong because legged robots are complex, expensive, and need careful balance control.
- Ignoring the terrain is wrong because the surface strongly affects which movement system will work safely and efficiently.
Practice Questions
- 1 A wheeled robot travels 12 meters in 4 seconds on a smooth floor. What is its speed in meters per second?
- 2 A tracked robot climbs over 8 small obstacles in 2 minutes. If it keeps the same rate, how many obstacles can it climb in 5 minutes?
- 3 A robot must deliver medicine inside a school, then climb a short set of stairs during emergencies. Would wheels, tracks, or legs be the best main design? Explain your choice using at least two reasons.