# Topics > Robotics > Humanoids >  Compliant humanoid robot, The Robot Studio, Divonne-Les-Bains, France

## Airicist

Developer - The Robot Studio

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## Airicist

How to build a compliant humanoid robot - PTFE Shoulder Socket Liner 

 Published on Nov 14, 2013




> 80mm sq sheet of PTFE, commonly sold in DIY stores for furniture sliders, etc heated to approx 110C and then formed by hand pressing with a shoulder ball.

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## Airicist

How to build a compliant humanoid robot - Shoulder Socket 

 Published on Nov 15, 2013




> Forming of a polymorph socket for the shoulder.

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## Airicist

How to build a compliant humanoid robot - Ligaments 

 Published on Nov 15, 2013




> Ligaments connect bone to bone, tendons connect muscles to bones. Each shoulder joint requires 5 ligaments for stability and to limit rotation. They are made from a chunky dyneema (approx 300daN) by working hot polymorph into the last 30mm of each end with a standard pair of hair straightening tongs heated just to the melting point of dyneema (approx 140C). For maximum strength the very ends of the dyneema should just be fusing with the polymorph when drawn through the tongs for the final time. Typically the centre of the tongs is slightly hotter than the ends, thus allowing this fine control.

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## Airicist

How to build a compliant humanoid robot - Fitting PTFE Liner 

 Published on Nov 15, 2013




> The pre-formed PTFE liner is stretched over the pre-formed shoulder socket and secured by hot crimping.

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## Airicist

How to build a compliant humanoid robot - How to make a half mounted pulley 

 Published on Nov 15, 2013




> The pulley is formed of a needle roller bearing (4x8x8), a hardened steel dowel (4x24) and a machined grooved nylon cylinder. One side slots into the 3D printed guide, the other is pre-formed with a polymorph retainer.

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## Airicist

How to build a compliant humanoid robot - Upper Scapula Motors 

 Published on Nov 15, 2013




> Motors are first checked for position and cable aligment and then secured to the 3D printed guide with a hot fitted 0.4g gasket of polymorph.

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## Airicist

How to build a compliant humanoid robot - Components 

 Published on Nov 15, 2013




> Complete set of parts for the Mk1 open source compliant robot torso powered by 26 DCX maxonmotors.
> 
> All 3D printed parts are available on Thingiverse as stl files, search under "therobotstudio".
> 
> Video instructions for assembly are on-going on YouTube and installation of software is covered on our blog at therobotstudio.com

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## Airicist

How to build a compliant humanoid robot - Series Elastomer 

 Published on Nov 19, 2013




> The most important mechanical difference between traditional and compliant robots is the addition of a series elastic element, which can be as simple as just a spring on the end of the motor.
> 
> Here, three lengths of polyurethane (PU) tubing (40mm) are bonded to dyneema tendons ready for attachment to the motor output spool. The working load of this arrangement is 200N and the breaking strain well over twice that, if the bonds are done correctly it should be very difficult indeed to break by hand. Note the technique for terminating the dyneema consists of rolling and folding over the roll, somewhat like a croissant.
> 
> The PU is 1/4" tubing with a hardness of 85A available from Freelin-Wade in a variety of colours, the red for example is part number: 1J-025-05 (Fre-Thane 85A Polyurethane).

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## Airicist

How to build a compliant humanoid robot - Bonding a tendon to a motor output spool 

 Published on Nov 19, 2013




> The motor output spool winds up the dyneema tendon to shorten the muscle. The tendon is attached by bonding the spread fibres into a hole drilled across the spool. This hole has two diameters, 1.8mm and 2.2mm to provide positive location for the bonded tendon.
> 
> Note that the bonding takes account of the orientation of the dyneema so that the elastic element will lie flat to the shoulder.
> 
> The glue used is a specialist cyanoacryolate produced by Charkbait for sport fishing: CHARKBAIT SPECTRA ADHESIVE

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## Airicist

How to build a compliant humanoid robot - Mounting motor output spool 

 Published on Nov 19, 2013




> The motor output spool is secured to the motor shaft by a grub screw and an additional support bearing is then added to withstand the radial loads placed on the motor shaft by the tension in the tendon.
> 
> The support bearing is mounted into a carrier which also provides a cage around the motor output spool to prevent the tendon falling out of position.
> 
> These components are all held in place by hand applied polymorph. Note the dyneema is wetted to prevent accidental burning with the hot air gun.

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## Airicist

How to build a compliant humanoid robot - Pulley reinforcement 

 Published on Nov 19, 2013




> An example of applying polymorph by hand to strengthen the structure between the motor output and the pulley. A small retaining piece is also added over the top of the pulley to join the two half of the pulley mount and to prevent the tendon from falling off the pulley.
> 
> Note the use of wet tissue paper to prevent accidental burning of the dyneema tendons with the hot air gun.

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## Airicist

How to build a compliant humanoid robot - 3D print reinforcement 

 Published on Nov 19, 2013




> An example of reinforcing the 3D printed guide with hand applied polymorph.
> 
> Pulleys are also half mounted during this process.

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## Airicist

How to build a compliant humanoid robot - Arm motors 

 Published on Nov 20, 2013




> Mounting of the arm motors to the 3D printed guide with a hot fitted polymorph gasket (0.4g).
> 
> Note the rotation of the motors to allow connection to the EPOS driver boards without twists in the cable.

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## Airicist

How to build a compliant humanoid robot - Elbow pin guide 

 Published on Nov 20, 2013




> Mounting of the needle roller bearings (6mm ID) that carry the elbow pin and hand applied polymorph reinforcement of the carrier.

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## Airicist

How to hand build a humanoid robot - PTFE eyelets 

 Published on Jun 11, 2014




> PTFE eyelets are used all over the robot and are essential for the tendons to glide smoothly. They are surprisingly tricky to keep in place due to their low friction nature so it helps to flare both ends of the tube to make a hollow dumbell shape.
> 
> PTFE tube that is a loose fit on the dyneema is cut into short lengths (8-10mm) and then flared at both ends with a tool made of a hinge, two bits of wood and two or more speaker stand spikes.
> 
> The key to this process is to get everything hot enough in advance for the PTFE tube to stretch easily.
> 
> One use of the PTFE eyelets is in the fingers for pulleys:
> 
> 1. pre wrap the formed eyelet with a small ring of polymorph so it's a bulging cylinder
> ...

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## Airicist

How to hand build a humanoid robot - finger ligaments 

 Published on Jun 11, 2014




> The simplest way to actuate a finger is with a single tendon connected all the way to the tip. This leaves the three joints of the finger underconstrained so such a finger is likely to move in painful looking ways and has very little grasping capability. One easy remedy to this is to add extra ligaments from the back of one finger section to the underside of the next.

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## Airicist

How to build a compliant humanoid robot - Self stabilising balance 

 Published on Sep 8, 2014




> The balancing algorithm shown is so far only able to control the motors in the ankles, thus balance can only be recovered from a very minor perturbation.
> 
> On the right hand side of the TV screen you can see the Centre of Pressure (COP) which is calculated from six ground reaction force sensors and displayed as a normalised red dot. Each line on the grid corresponds to 10%. The robot tries to keep the COP at the point 25% back from the geometric centre of the area of ground contact. This corresponds to a relaxed pose with the weight of the body almost directly over the ankles.

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## Airicist

Final Systems Test 

 Published on Nov 3, 2014




> The first successful test of all the new systems running together at the same time - this is what it's all about - now we see what we've got...

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