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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.
Developer - The Robot Studio
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.
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.
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
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).
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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