🦾 Biomechanical Robotic Arm

Project Overview

Tendon-driven biomechanical robotic arm inspired by human anatomy. Staged build: upper arm → forearm → shoulder → wrist → hand/fingers. Actuation via TCP nylon muscle fibers + nichrome heating, mirroring biological muscle hierarchy.

Status: Prototype phase — material testing, first fascicle build in progress.

Muscle Hierarchy

Level	Description
Fiber	0.3mm nylon + 0.15mm nichrome co-inserted, sewing thread bound, coiled
Pair	2 fibers twisted opposite direction — 2-ply, self-stabilizing
Fascicle	2–3 pairs + Kevlar strain limiters in 4mm PET braided sleeve
Muscle	Multiple fascicles, controlled per muscle via MOSFET
Arm	Kevlar tendons, aluminum/brass bones, resin joints

Actuation Specs

Nylon: 0.3mm PA6/PA66 monofilament (not fluorocarbon)
Nichrome: 0.15mm AWG34, co-inserted parallel to nylon
Target resistance: 10–50Ω per strand (~25Ω sweet spot at 12V)
Contraction: 0.5–2s heating | Relaxation: 3–8s cooling
Control: ESP32 + N-channel MOSFETs (IRLZ44N) + PWM
Power: 30V/10A lab PSU (dev) → ATX 600–700W (final)

Skeleton

Bones: Aluminum/brass tubing + 3D-printed resin joints (PTFE-coated)
Tendons: Braided Kevlar/aramid — transmit force only
Joints: PTFE bushings for low-friction rotation

Build Phases

Upper arm — prove TCP fiber concept