Spider Robot

The “Spider Robot” project (original designer : Regis Hsu) is a quadruped robot with 12 degrees of freedom (DOF), which uses 9 grams servos, a mini-pro Arduino card, a HC-06 bluetooth module and 3D printed parts, that made the project complete and relatively inexpensive (note it has ever been one of the goals of the designer).

 

Regis Hsu shares all the needed files in the Instructables website and in his blog : from the STL files up to the Arduino files, passing by the silk screen for the PCB making: open-source & open-hardware development at the true term meaning – thanks to the designer for this.

 

By rubbing against this robot, numerous of things will be learnt:

  • CAD modeling → to remodel the parts and to adapt them if necessary (and why not adding a new centrale shape closer to the one of the spider),
  • programming →Arduino card and bluetooth module,
  • electronics →PCB making and remote controler under development,
  • robotics → through Inverse Kinematic, learning and understanting the theory that is behind the behaviour of the spider,
  • and so on…

 

This project will be the opportunity to create training classes in our Fablab; several people took a keen interest for such project and they started to order the parts.

 

Some amazing videos: video1, video2.

 

 

1- Ordered parts list

Herebellow the table of the ordered parts:

Name Price Remark Link
Arduino Pro-mini 3.07€

Card choosen with the connexion USB → TTL module

Aliexpress
DC – DC Converteur 12V → 5V/3A 2.27€ UBEC: input from 5.5 to 26V → 5V/3A or 6V/3A in output (*) Aliexpress
HC-06 bluetooth module 2.51€ Robot driven from a smartphone for example (waiting for the remote controler under development) Aliexpress
9 grams Servos SG90 22.86€   set of 20 (12 requested) Aliexpress
LiPo 3000 mAh 2S 40C battery 18.05€ Battery in 7.4V (**) Hobbyking
On/Off switch 2.89€ Set of 10 here (only one is needed – interesting if grouped order) Aliexpress
2.54 mm male pin header connector 0.65€ set of 10 Aliexpress
2.54 mm female pin header connector 3.13€ Set of 12 Aliexpress

(*): The UBEC conterbalances the tension loss when using the battery, compared to an ajustable regulator.

(**): Purchase a LiPo charger for whom does not have one; I was adviced to get the Imax B6 (get the original and not the copy), with a power supply.

(***): a Perfboard or a double side copper clad (for toner transfer) may be usefull.

(****): The battery connector has not be anticipated yet (not Jack connector here).

(the Led and the resistance will be easily found in the fablab).

 

The cost (without the 3D printed parts and the LiPo charger) ) remains lower than 60€.

 

 

2- Parts remodeled under FreeCAD

From the STL files, I remodeled the parts under FreeCAD (using Assembly2 module as well); after a first modelling that led to issues when using external references, all the parts were modelled ounce again; no external reference has been used  anymore and It works correctly now (sometime not as practical as using the previous references, it’s a pity).

 

The goal is mainly to be able to make my own changes (I’m not speaking about improvement on the original design, but rather minor modifications due to different components for example – typically the Lipo battery). Another non negligeable reason : a complete leg was printed highlighting that I needed to increase some dimensions and some gaps (it might come from the printer – I don’t know / I’m not skill enough), but I can do these changes now.

 

Before sharing the native files, I would like to validate that the modifications I’m making are relevant … somes pictures here after in the meantime:

 Spider_Robot3  Spider_Robot1

View 1

View 2

 Spider_Robot2 leg_horiz_crop

View 3

View 4

 max_vert_crop
max_horiz_crop

View 5

View 6 (bug in the module)

NB : Please remember that such project will be used for FreeCAD training sessions in our Fablab (“learning through example”)

 

A FreeCAD merged assembly CAD model can be found here (“muxed” – Spider_Robot_muxed) – the complete model with all the parts and sub-assemblies will come in a second step, when the assembly is made.

 

In the meantime some photos of the parts currently 3D printed:

 

spider_3D_printing_1 

 spider_3D_printing_2

Photo 1

Photo 2

 

A colleague at the Fablab (electronics engineer) has finished his “Spider Robot” ; some photos and videos hereafter.

Spider_colleague1

Spider_colleague2

Photo 1

Photo 2

(416 gram – the choice of the 2S lipo battery has  not probably

the best one)

The videos of the first test (see video1) and the first walk (see video2) have been published here.

 

The assembly of our spider robot is now in my soon’s hand – he seems now galvanized by the previous success  😉  .

 

 

3- Electronic section

In coming.

NB: Experiment to perform:

  • completely a newbie in electronic engineering, I was looking for a “DIY” way to make my own PCBs – I heard about ferric chloride or ammonium persulfate for etching process, even the use of hydrochloride acid mixtures – dangerous products by nature, toxic, that must be stocked carefully, etc
  • in some websites, I can read that instead it’s possible to use a mix of White vinegar (5% of acidity), Hydrogen Peroxide (3%) and Kitchen Salt – clearly safer than the previous products, easy access and certainly less expensive,
  • furthermore, using water bath heating at about 40°C (≈100°F), the chemical kinetic is speed up (duration reduces by a ratio of 2),
  • experiments (and set-up) to make for the Spider Robot PCB (and some others)!!!

Some interesting documents (doc1 – doc2) and videos  – trials to make.

 

4- Arduino & programing section</