Introduction: Wall Climbing Robot

The wall climbing robot serves to provide an alternative inspection for walls through the use of mechanical and electrical systems. The robot offers an alternative to the expense and dangers of hiring humans to inspect walls at high heights. The robot will be able to provide live feed and storage for documentation of the inspections via bluetooth. Along with the inspection aspect of the robot, it will be able to be controlled through transmitters and receivers. Through the use of a fan producing thrust and suction allows for the robot to climb perpendicular to a surface.


Base & Cover:

- Fiberglass: Used to make the chassis

- Resin: Used with fiberglass to make the chassis


- OTTFF Robot Tank Kit: Tank treads and motor mounts

- DC Motor (2): Used to control robot movement

- Impeller and Connectors: Produces airflow to keep the robot on the wall

- ZTW Beatles 80A ESC with SBEC 5.5V/5A 2-6S for Rc Airplane (80A ESC with Connectors)


- Arduino: Circuit board and software for coding of the fan, motors, and wireless signal

- Joystick: Used to control the DC motors to drive the robot

- WIFI Receiver: Reads data from the transceiver and relays it through the Arduino to the motors

- WIFI Transceiver: Records data from the joystick and sends it to the receiver over a long-range

- Female and male connectors: Used to wire the electrical components

- WIFI Antennas: Used to increase connection signal and distance for transceiver and receiver

- HobbyStar LiPo Battery: Used to power the fan and other possible electrical components

Step 1: Understanding the Theory

To better understand the equipment selection, it is best to first discuss the theory behind the Wall Climbing Robot.

There are several assumptions that must be made:

  • The robot is operating on a dry concrete wall.
  • The fan is operating at full power.
  • The body of the robot remains completely rigid during operation.
  • Steady airflow through the fan

Mechanical Model

Variables are as follows:

  • Distance between the center of mass and surface, H = 3 in = 0.0762 m
  • Half of the length of robot, R = 7 in = 0.1778 m
  • Weight of robot, G = 14.7 N
  • Static coefficient of friction - assumed rough plastic on concrete, μ = 0.7
  • Thrust generated by the fan, F = 16.08 N

Using the equation shown in the above image, solve for the force generated by the pressure difference,

P = 11.22 N

This value is the adhesion force that must be generated by the fan to allow the robot to remain on the wall.

Fluid Model

Variables are as follows:

  • Change in pressure (using P from the mechanical model and the area of the vacuum chamber) Δp = 0.613 kPa
  • Density of fluid (air), ⍴ = 1000 kg/m^3
  • Friction coefficient of surface, 𝜇 = 0.7
  • Inner radius of vacuum chamber, r_i = 3.0 in = 0.0762 m
  • Outer radius of vacuum chamber, r_o = 3.25 in = 0.0826
  • Clearance, h = 5 mm

Using the equation shown above, solve for the volumetric flow rate,

Q = 42 L/min

This is the required flow rate that the fan must produce to generate the necessary pressure difference. The chosen fan meets this requirement.

Step 2: Creating the Base

Fiberglass quickly became an essential material in the construction of the base. It is inexpensive and fairly easy to work with, as well as being extremely lightweight, which is very important for the application.

The first step in creating this base is to measure it. For our application, we used a dimension of 8" x 8". The material shown in the above pictures is known as E-glass. It is fairly cheap and can come in large quantities. When measuring, it is important to provide an extra 2+ inches to ensure there is an ample amount of material to cut into the desired shape.

Secondly, secure something that can be used to form the fiberglass into a smooth, even surface; for this the team used a large metal plate. Before beginning the curing process the tool must be prepared. A tool can be any large flat surface.

Begin by wrapping a double-sided adhesive, preferably in the shape of a square, as big as you need. Next prepare a filament and place the dry cut pieces of fiberglass on top of it. Transfer all items on to the tool.

Note: you can stack the cut pieces of fiberglass to add thickness to your final product.

Next: you want to properly mix the resin and its catalyst, every resin is different and will require the user manual to properly mix portions with its catalyst. Pour the resin across the glass until all dry parts of the glass are wet with resin. Next cut off any excess filament. After that is done, add another piece of film and then a fiberglass cloth that covers the entire product. Afterward, add a breather cloth.

Now it is time to cover the entire operation with a plastic wrap. But before this can occur a breach device must be added. This device will sit underneath the plastic to allow a vacuum pump to be added.

Remove the adhesives protective brown cover and press the plastic cover down so it is the adhesive makes a vacuum-tight seal in the square. Next cut a hole in the center of the tool underneath so that a hose can be connected. Turn the vacuum on to remove air making a flat surface and a well put together product.

Step 3: Robot Mobility

To get the robot to move up and down the wall, we decided to use tank treads from a relatively cheap Arduino tank kit. This kit included all tools and fasteners needed to secure the tracks and motors. The black metal chassis was cut to create mounting brackets; this was done to reduce the amount of additional fasteners, as all of the ones needed were included.

The instructions below will show how the brackets were cut:

  • Use a ruler to mark the center point of the chassis
  • Draw a horizontal and vertical line through the center
  • Carefully cut along these lines, preferably with a band saw or other metal cutting blade
  • Use a grinding wheel round off any sharp edges

The finished brackets are shown in the following step.

Step 4: Mount Brackets for Tank Tracks

Begin by marking the center lines on the fiberglass sheet; these will be the reference.
Using a 1/8" drill bit, cut the following holes; all brackets must be flush with the outer edge of the robot as shown.
  • The first hole that needs to be marked should be 2" from the center line as shown
  • The second hole should be 1" from the previous mark
  • This process should be mirrored over the center.

Note: Brackets include additional holes; these can be marked and drilled out for additional support.

Step 5: Construct and Mount Tracks

Begin by assembling the bearings and gears using the provided parts; instructions are included in the kit. The tracks should be pulled tight to avoid slipping from the gears; too much tension may cause the fiberglass to warp.

Step 6: Install Fan to Chassis

Begin by cutting a 3" diameter hole in the center of the fiberglass sheet. This can be accomplished in several different ways, such as a hole saw or dremel. Once the hole is complete, place the fan over the hole as shown and secure with some type of adhesive or epoxy.

Step 7: Coding

The microcontrollers that we used are all Arduino components.

Arduino Uno board= 2

Male to female jumper wires = 20

Male to male jumper wires = 20

L2989n motor driver = 1

nrf24l01 = 2 (Our wireless communication device)

nrf24l01 = 2 (An adapter that makes installation easier)

The wiring diagram shows the proper connection we used and the code that goes along with it.

Step 8: Wire Diagram

Step 9: Constructing the Robot

After the base and treads are built, the final step is putting all the parts together.

The most important factor is weight distribution, the battery is very heavy so that should be on one side alone. The other components should be placed purposefully to counter the weight of the battery.

Putting the electronics on one corner in the middle of the motors is important to ensure the wires meet the motor without the use of additional wires.

The final connection is the battery and ESG to the fan, this step is very important. Make sure the battery and ESG are correctly connected with both positive sides connecting to each other. If they are not connected correctly you risk blowing a fuse and destroying the battery and the fan.

I taped the controller electronic parts on a panel to keep organized, but that part is not a necessity.