TCP Muscle — MUSCLE

MUSCLE ARCHITECTURE — BIOINSPIRED SPEED

Speed in TCP actuators isn't just a materials problem — it's a systems architecture problem. By mimicking biological motor unit recruitment and elastic energy storage, we push performance beyond single-fiber thermal limits.

THE CORE TRICK — ELASTIC PRE-LOADING

Fine fascicles run continuously at low PWM, keeping elastic tendons under pre-tension at all times. When coarse fascicles fire, the spring is already wound. The tendon releases stored energy simultaneously with muscle contraction → net speed greater than either system alone. Free speed — no extra actuation.

FINE FASCICLES (always on, low PWM)
    → maintains pre-tension on elastic tendons
    → positional stability + fast small corrections
    → analog continuous signal from ESP32

COARSE FASCICLES (burst recruited)
    → fires into already-loaded spring system
    → tendon releases simultaneously with contraction
    → burst PWM pulses from MOSFET driver

OIL-FILLED SLEEVES
    → faster cooling → faster reset for next contraction

CONTROL LAYER (ESP32)
    → MOSFET per fascicle wired physically
    → grouped per muscle in software by default
    → split to per-fascicle when needed — wiring already supports it

LVL 1

FIBER

Nylon + nichrome co-insert, sewing thread bound, TCP coiled

LVL 2

PAIR

2 fibers twisted opposite direction — 2-ply, self-stabilizing, no return spring needed

LVL 3

FASCICLE

2–3 pairs + Kevlar strain limiters in 4mm PET sleeve (oil-filled)

LVL 4

MUSCLE

Fine fascicles (pre-tension) + coarse fascicles (power) — controlled per muscle via MOSFET

LVL 5

ARM

Muscle groups with elastic tendons, Kevlar ligaments, 3D-printed TPU skeleton

PHASE	TIMING	NOTES
Coarse contraction	0.5–2 seconds	Nichrome Joule heating — active
Coarse relaxation (dry)	3–8 seconds	No oil — air cooling only
Human muscle	~100ms	Chemical, not thermal — fundamentally different
Reflex arc	~20ms	Spinal, bypasses brain entirely

TCP suits deliberate, controlled motion — not fast reflexes. Speed limit moves from "how fast can nylon cool" to "how fast can you sense and recruit" — a much more solvable problem in software.

04 MUSCLE

THE CORE TRICK — ELASTIC PRE-LOADING