Introduction: GECO - Wall Climbing Robot
This is an instructable on how to make a wall climbing robot using impeller technology. The goal of GECO (a research project from Ghent University) was to create a low cost, diy wall climbing robot.
Our solution uses the following parts:
- EDF ducted fan (70mm - 1,45kg thrust) (XRP-70142600)
- ESC (60A 2-6S)
- Lipo battery (2600 mAh)
- Arduino Uno or handmade pcb
- Motor Board (L298N)
- Micro motors (Pololu 1595 - 1000:1 - 6V)
- Wifi module
And uses the following techniques:
- 3D printing
Step 1: Calculations
If you want to make a wall climbing robot like GECO but want to adapt the design (add wheels, camera, ... or use different materials, parts...) you will have to do a little calculation (not hard!). Therefore you can use the equation as shown in the upper image.
First you'll need to know the mass of the robot. I managed to estimate the mass quite accurate by summing up the masses of the parts of the robot (don't forget the mass of the fan too). I got: m = 800 gram.
For the friction coefficient for rubber on concrete I found: µ = 0.6 (you can argue with the use of this number)
With this we can solve the equation.
Fs = (0.8 kg * 9.81 N/kg) / 0.6 = 13,08 N
Because most of the ducted fans are indicated with 'kilogram-force' or 'thrust' we will now convert the Newtons into kilogram-force.
Kilogram-force = 13,08 N / 9.81 N/kg = 1,33 kg thrust
Or you can check it on the following website: http://www.convertunits.com/from/kilogram-force/to...
Now you can choose the right fan for your project!
If you have an EDF ducted fan and know amount of thrust it can produce, you can also calculate the maximum weight of the robot (reverse the equation).
Step 2: Assembling
The zip file contains the 3D CAD models of the GECO robot. This way you can add or adjust parts from the robot.
It also contains a pdf file for lasercutting the base out of poplar wood (4 mm) and the cover out of pp (0.5 mm). After this you can 3D print the stl parts (PLA).
Everything is designed so that assembling is easy.
If you have a different Fan you may have to adjust some parts so your fan fits in.
Step 3: Arduino or Handmade PCB
The two next steps let you choose out of making the electronics with an arduino or handmade pcb.
Both options have their advantages. The arduino uno is a standard component while you have to make the pcb yourself. The pcb will save some space (no need for extra voltage regulators anymore, these are integrated) and will give the possibility to power a ledstrip.
Both options are programmable in arduino.
Step 4: Handmade PCB
We chose to integrate the arduino, voltage regulator and wifi module into one pcb. The first picture shows the wiring diagram of the robot. The second the pcb scheme. The third picture shows the actual pcb.
You can use an atmega328 out of an arduino uno, or flash one yourself (see other instructables).
The program you have to put on the atmega is given at the 'programming' section of this instructable.
The ledstrip I used had 4 connection pins (R, G, B, +12V). There are several versions of ledstrips on the market, if you choose to work with a different type of ledstrip you may have to adjust the pcb/program. An example of the used ledstrip in the link below. (Offcourse you can always leave the ledstrip out of the design)
Step 5: Arduino
The arduino will be powered by the lipo. To do this you will have to make a voltage regulator. The arduino will controll the motorboard, esc and RGBled. You will have to connect a wifi module to the arduino so you can control the arduino from a distance.
The first picture shows a selfmade voltage regulator, you can find instructables to make one. This regulator will have to convert 13 - 16 V into 5 V.
To check the voltage of the battery we have used a voltage divider (two resistors 6.8K - 2.2K). This way we can use an analogue pin of the arduino. If the battery has a voltage of 16V the arduino will read out a voltage of 3,91V and if the battery has a voltage of 12V the arduino will read out a voltage of 2,93V. If the battery goes under 13V we will indicate this by using leds. This because the voltage of the battery shouldn't go under 12 V.
I have integrated the voltage divider into the battery balancer plug (second picture).
geco_3.3.ino is a testing program for the arduino. If you connect all electronics (scheme is given in the third picture), you can use this program to test your robot or electronics (the test program does not use wifi).
Beware: you will have to program your ESC as well. Instructions can be found in the manual of your ESC. For example: http://www.xblade-tech.com/ztw-user-manual/ztw-bea... (can be tricky)
I will not handle how to connect the arduino to a wifi shield. Information on this topic can be found in other instructables.
Step 6: Assembling the Electronics
First we add the impeller to the robot. After this you can add the lipo, esc, motorboard, motors, arduino, powerswitch and ledstrip. You can look into the 3D files to get an idea about how to assemble this.
Step 7: Programming
The zip file contains a code in aruidno which is used to program the arduino chip and a processing file which is used to control the robot from a computer.
Step 8: Finishing
You can protect the content of the robot by adding this resealable cap.
Enjoy the GECO robot!
Step 9: Remarks
I have faced problems with the grip of this robot but solved this problem by gluing a small strip of working gloves (the black part) on to the wheels. This eliminated the problem entirely.