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EJBot-II: Skid-Steering Propeller-Type Climbing Robot

Creator: Egypt-Japan University of Science and Technology

Country: Egypt

Year: 2019


A versatile climbing robot with a hybrid actuation system combining propeller thrust & wheel torque for stable adhesion on diverse surfaces.

Status: Prototype, Research

Operation: Semi-autonomous, Teleoperation

Robot Type / Domain: Research, Other Infrastructure

Tasks: Visual Inspection, Wall Thickness Measurement

Whimsical Intro (by addoobot)

Ever seen a helicopter move up a wall? It sounds strange, but that's exactly what the mini helicopter, EJBot-II, does! Normally, propellers help us move away from surfaces and soar through the sky, but what if they did the opposite? Instead of flying away, EJBot-II uses them to cling to surfaces. Intrigued? There's more to this story below!

Learn More

Why Climbing Robots, Such as EJBot-II, Are the Future (and the Coolest)

Imagine a world where robots effortlessly climb skyscrapers, inspect the toughest spots on nuclear plants, and rescue those in danger from high places. These robots are becoming a reality, and at this rate of advancement, we will be witnessing various cool climbing robots in the near future that are able to solve real-world problems in places where human involvement is too risky.

One such robot is EJBot-II. This robot has the potential to carry out many different tasks, from cleaning those impossible-to-reach glass facades to inspecting the intricate welds of ships, tanks, and bridges. But EJBot-II is currently designed to traverse the outer and inner surfaces of vessels in petrochemical and liquefied gas industries, conducting wireless visual inspections of welds for corrosion and measuring wall thickness.

What Makes EJBot-II Special for Climbing?

When you think of propellers, you might think of drones and helicopters using them to move away from the surface. But EJBot-II leverages propeller-based aviation systems with an intriguing twist—to stay on the surface. It uses a hybrid actuation system (wheels and propellers) to ensure that the climbing robot doesn't fall off the surface while it moves around walls, ceilings, and curved surfaces securely.

Think of a car on a steep ramp: the car relies on both its weight and the torque of its wheels to avoid rolling back. Similarly, EJBot-II's propellers increase traction force (similar to the weight of a car on a ramp), while the wheels provide the torque and friction needed to navigate and stop on inclined surfaces.

The Magic of the Propeller System

The main benefit of using a propeller-based climbing method is that, unlike other climbing adhesion systems such as suction cups and magnets, it eliminates the need for smooth surfaces or a particular structural material. Thus, holes, cracks, protrusions, and even curvatures on cylindrical surfaces are no issue for this robot. This versatility opens up many possibilities for operating in complex environments such as vessels, pipes, and bridges.

A Closer Look at EJBot-II's Ingenious Design

The original version, EJBot-I, already had an impressive design that featured two coaxial upturned propellers on a mobile platform with four wheels. But EJBot-II takes it up a notch. The wheels have been swapped out for a track system, providing superior traction. Plus, EJBot-II is built with a composite material frame, making it both stiff and lightweight.

Another great upgrade of EJBot-II is the mechanism to smoothly transition from the ground to a vertical wall. Several transition mechanisms were investigated but the two-arm design underneath the robot was found to be the most suitable option. The two arms beneath the robot generate forces against the ground, effortlessly lifting the robot towards vertical surfaces.

And let's not forget the batteries—now mounted directly on the robot, there's no more dealing with the cumbersome and heavy umbilical cord that hinders the movement of the robot.

Technical Specifications

Size: 324L  371W (mm)

Size: 12.756L  14.606W (in)

Reachable Height: N/A

Max. Payload: 0.4 kg

Max. Payload: 0.882 lbs

Weight: 1.75 kg

Weight: 3.858 lbs

Max. Climbing Speed: N/A

Max. Slope: 360°

Battery Operated? Yes

Average Runtime: 0.21 hr(s)

Max. Runtime: 0.25 hr(s)

Battery Recharge Time: N/A

Climbing Methods: Pneumatic, Two Coaxial Upturned Propellers

Climbable Surfaces: Walls, various surface materials and terrains, ferrous and non-ferrous

Number of Axes: N/A

Manipulation: N/A

IP Rating: N/A

Operating Temperature: N/A

Max. Wind Speed Resistance: N/A

Open-source? N/A

Price: N/A

Torque: Max. transition arm servo motor torque: 3.500 N m • Max. wheel motor torque: 1.1277 N.m

Other Dimensions: Tracks wheel radius: 30 mm • Propeller diameter: 304 mm • Orthogonal distance: 34 mm

Max. Thrust Force: 49.05 N

Controller & Computing: Electronic Speed Controller ESC; Dual 7A motor controller

Remote Control / Interface: RC hoTT 2.4GHZ Transmitter - tele-operated radio control system consisting of 9-channel 2.4-GHz hoTT receiver and transmitter

Material: 12 inch carbon fiber propeller • Material density of frame (CFRP): 1760 kg/m^3 • Frame thickness: 2 mm

Actuators: DC geared motor for the tracks. Brushless motor for the propeller.

Power supply: Battery mounted directly on the robot platform

Battery: Portable LIPO battery that has 6-cell and 3000 milli-Ampere-hour (mAh) capacity. Its mass is around 300 g and mounted directly on the robot platform

No more specs to show.

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Comment by addoobot - Our Perspective

What we find particularly attractive about this robot is its use of propellers to obtain greater adhesion to all sorts of surfaces, not just smooth, flat, or ferrous ones. Such a robot may have a disadvantage in terms of payload capacity compared to some other adhesion mechanisms like magnetic or suction-based systems, but there is room for improvement. However, this robot design is ideal for inspection, surveying, and thickness analysis. What do you find appealing about this robot? We would love to know your perspective below.

addoorable score:
The second version of this robot, EJBot-II, looks more 'addoorable' than its predecessor. It is not designed to be a toy, but rather an R&D project for an industrial application. So, reliability and performance are of greater importance.

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