Introduction

Mobile robots are becoming increasingly important for automating tasks in many different fields. That's because mobile robots are a key way of replacing a robot's legs with wheels in order to automate labor-intensive and potentially dangerous tasks. In this blog, we will look into the structures, advantages, limitations, and use in practice of the two main types of mobile robots: legged robots such as real animals, and wheeled robots such as tractors and cars.

Wheeled Mobile Robots

The most common kind of mobile robot you will encounter is the wheeled robot, which is simple and efficient to operate on flat surfaces.

Structure and Components:

• Wheels: The fundamental component for locomotion, providing the necessary traction and mobility.
• Motors: These drive the wheels and determine the speed and direction of the robot.
• Sensors: Cameras, LIDAR, ultrasonic sensors, and encoders to detect obstacles and measure distances.
• Control Systems: Algorithms and software that manage movement, path planning, and obstacle avoidance.

Advantages:

• Speed and efficiency: Wheeled robots can move at a very high velocity on level flat surfaces. Their simple roll motion lends itself to fast and efficient movement.
• Stability on Flat Surfaces: On flat surfaces, wheeled robots are some of the most stable mobile robots. There is very little chance that wheeled robots will fall over. This stability is essential to execute precise repeatable actions.
• Energy efficiency: Given that the friction and resistance posed by the ground to wheels are lower than to legs, wheeled robots exhibit higher energy efficiency compared with legged robots, allowing for longer operation times.

Common Applications:

• Industrial Automation: Automated guided vehicles (AGVs) are widely used in warehouses and factories, which are developed for material handling, inventory management, and assembly line operations. They can transport goods by following the predefined paths in order to improve efficiency and productivity.
• Logistics: Delivery robots such as the ones developed by Starship Technologies provide last-mile delivery of packages and food items between a transport hub and a customer's premises. These robots can move autonomously in urban environments.
• Cleaning Robots: Autonomous vacuum cleaners like the Roomba have become commonplace. They intelligently navigate homes, cleaning floors while navigating furniture or other obstacles.

Limitations:

• Terrain adaptability: Wheeled robots are highly affected by rough, uneven or soft terrains. Moreover, their performance is severely limited on non-flat or non-smooth surfaces, restricted to indoor environments or smooth roads.
• Obstacle Navigation: Wheeled robots cannot traverse steps or large pieces of debris that are higher than their wheel radius. So, they are limited to simple environments where there aren't many steps or obstacles.

Legged Mobile Robots

Legged robots move like animals and humans by employing several legs. Multiple legs enable these devices to move across challenging terrain, where wheeled robots cannot go.

Types of Legged Robots:

• Bipeds: Robots with two legs, that walk like humans, such as Boston Dynamics' Atlas, which can do complex motions such as running, jumping, even flipping.
• Quadrupeds: Four-legged robots that run and walk like a dog or horse. Boston Dynamics' Spot is a prominent example that can operate in natural or urban environments, performing tasks such as inspection and mapping.
• Hexapods: Six-legged robots with greater stability and versatility than their four-legged counterparts. With an extra set of legs, hexapods ensure redundancy, so if one or two of the legs fail, the robot is still standing.

Advantages:

• Adaptability: Legged robots can move over rugged, rocky, unstable and soft surfaces that could be inaccessible to wheeled robots. Their ability to locate the foot position and lift and place each leg separately enables them to move over obstacles.
• Obstacle Navigation: They can step over obstacles and traverse stairs People in disaster-stricken areas need their rescue robots to be as close as possible. Legged robots can step over obstacles and traverse stairs, giving them a much
• Adaptability: The robot's gait changes depending on the environment, which helps it maintain stability and efficiency for locomotion even on varied terrain (advanced control algorithms and sensors help out here).

Challenges:

• Complexity: Legged robots are mechanically and computationally complex to design and control. It's difficult to accomplish multiple legs marching in unison without tripping up and falling over.
• Power consumption: A legged robot uses more power than a wheeled robot because of the mechanical effort needed to lift the legs against gravity. Efficient power management and better batteries will help extend operating time.
• Balance: For bipedal robots in particular, remaining stable is a huge challenge and involves sophisticated sensors and control systems. It requires enough accuracy so that the robot does not topple over.

Potential Applications:

• Search and Rescue: Legged robots are perfect for navigating debris and uneven terrain to reach victims in disaster areas, carrying supplies, performing reconnaissance and helping to locate survivors.
• Exploration: Robots equipped with legs are ideal for planetary exploration, as they can traverse the uneven and treacherous landscapes of the planets they are zooming in on. In 1997, NASA's Sojourner robot was the first rover to be sent to Mars, paving the way for media coverage of the six rovers that followed. Robots equipped with legs are meant to last in these harsh environments, and their primary objective is being a 'scientist' of the robotic kind.
• Human-Robot Interaction: Assistive robots for home and elder care can have legs, and roam around in your home and in health, care and nursing facilities, thereby reducing your mobility problems, perform routine tasks, and provide companionship.

Hybrid Robots

Hybrid robots strive to combine the merits of both legs and wheels, leveraging the best of both worlds to create one efficient creature. They walk, jump, and roll, switching between wheels and legs depending on the terrain.

Future Trends and Developments

• Enhanced AI: The continued advancement of AI will lead to better algorithms for decision-making and adaptability between robots and their surroundings.
• Better Batteries: Advances in batteries will increase the operating lives of both legged and wheeled robots, making them more practical for long-term tasks.
• Soft Robotics: Robots that merge conventional mechanics with pliable materials will be more versatile and resilient, and will be able to undertake more diverse, wider-ranging tasks, in different environments.
• Human-robot collaboration: As robots get better at what they do, working side by side with humans will get better, driving productivity and safety.

Conclusion

Legged robots have their advantages over wheeled ones, and vice versa. Both can find success in different applications, but some tasks might be easier for one type of robot than the other. As long as we keep these in mind - and as technology evolves to include more adaptive AI, better materials and novel designs - it seems that robots with legs and those with wheels will help us tackle an increasing variety of applications in the future. With hybrid designs, we will get the best aspects of both. Whether we're exploring Mars or delivering food, robots will start to perform tasks that were once firmly in the domain of humans.