the humanoid bill of materials — before you buy

Every component a robot needs, needs many decisions.

Thirteen subsystems stand between a concept and a humanoid that actually stands up — and each hides a fork in the road. Pick the wrong motor, reducer or hand and you pay in torque, in grams, in dollars, and in months of lead time. roboBOM lays out every option against the constraints that decide it, so the trade-off is obvious before the purchase order goes out.

the anatomy of a humanoid

Where every system lives on the body

Hover a system to light it up on the robot — or hover the robot to surface the systems inside it. Click any row to jump to its options.

01Joint actuator 02BLDC servo motor 03Reducer 04Bearing 05Linear screw 06Encoder 07Compute (SoC / GPU)08Battery pack 09Structure / frame 10PCBs & harness 11Proprioceptive sensors 12Tactile skin 13End effector (hand)

●●● cost & supply pressure★ what most humanoids ship◄ scroll any table right for suppliers · lead time ►

Joint actuator

how each joint is driven · logistics: heavy; rare-earth export rules

Type / option	Used when	Torque density	Backdrivability	Efficiency	Control ease	Cost	Suppliers	Lead
Quasi-direct-drive (QDD)★	legs & arms — dynamic, impact-tolerant joints	high	excellent	high	easy	●●●	Unitree, MIT-derived, in-house	8–14 wks
Geared electric (harmonic)	precision arms, wrists, waist	very high	poor	medium	precise	●●●	Harmonic Drive-based	12–20 wks
Series-elastic (SEA)	safe human-contact joints	medium	good	medium	force-friendly	●●●	in-house	10–16 wks
Hydraulic	legacy high-power (early Atlas)	very high	poor	low	hard	●●●	BD-style, custom	custom

Joint actuatorschematic

BLDC servo motor

the electromagnetic core · logistics: magnet content → export controls

Type / option	Used when	Low-speed smoothness	Torque density	Maintenance	Humanoid fit	Cost	Suppliers	Lead
BLDC, sensor-based (Hall)★	every powered joint	excellent	high	none	✓	●●●	T-Motor, Robotis	6–12 wks
BLDC, sensorless	fans & pumps — not joints	poor at low speed	high	none	✗	●●●	generic	4–8 wks
Brushed DC	toys, low-cost auxiliaries	good	medium	brushes wear	✗	●●●	many	2–6 wks
Stepper	3D printers, camera rigs	detented	medium	none	✗	●●●	OMC, generic	2–6 wks
Coreless	fingers & dexterous hands	very smooth	low	none	hands only	●●●	Maxon, Faulhaber	8–14 wks

BLDC servo motorschematic

Reducer

high-ratio gearing at the joint · logistics: fragile, precision handling

Type / option	Used when	Backlash	Torsional stiffness	Ratio range	Shock tolerance	Cost	Suppliers	Lead
Strain-wave (harmonic)★	arms, wrists — precision	near-zero	high	high	medium	●●●	Harmonic Drive, Leaderdrive	12–20 wks
Cycloidal	hips, knees — high load & shock	low	very high	high	very high	●●●	Nabtesco, Sumitomo	12–20 wks
Planetary	grippers, low-cost joints	moderate	high	low–med	high	●●●	Neugart, Apex	6–12 wks

Reducerschematic

Bearing

carries the joint load · logistics: standard freight

Type / option	Used when	Radial load	Axial load	Moment load	Compactness	Cost	Suppliers	Lead
Deep-groove ball	light auxiliary shafts	✓	light	✗	good	●●●	SKF, NSK	4–8 wks
Cylindrical roller	heavy radial shafts	high	✗	✗	medium	●●●	SKF, NSK	4–8 wks
Needle	compact wrist / finger	high	✗	✗	very compact	●●●	INA, IKO	4–8 wks
Thrust	vertical load points	✗	✓	✗	flat	●●●	SKF	4–8 wks
Crossed-roller★	every major joint	✓	✓	✓	very compact	●●●	THK, IKO	6–12 wks

Bearingschematic

Linear screw

rotary → linear motion · logistics: standard freight

Type / option	Used when	Efficiency	Load capacity	Precision	Self-locking	Cost	Suppliers	Lead
Ball screw★	linear leg / ankle actuators	~90%	high	high	✗	●●●	NSK, PMI	8–14 wks
Planetary roller	high-force compact linear	high	very high	very high	✗	●●●	Rexroth, GSA	10–16 wks
ACME / lead	manual adjust, low-cost lifts	low	medium	medium	✓	●●●	many	2–6 wks

Linear screwschematic

Encoder

closes the servo loop · logistics: light / air

Type / option	Used when	Resolution	Robustness	Absolute	Cost class	Cost	Suppliers	Lead
Optical	lab / precision arms	very high	dust-sensitive	option	high	●●●	Renishaw	6–12 wks
Magnetic★	most robot joints	med–high	robust	✓	medium	●●●	AMS, iC-Haus	4–10 wks
Capacitive	compact joints	high	medium	✓	medium	●●●	CUI	4–10 wks
Inductive	dirty / industrial joints	medium	very robust	✓	medium	●●●	Renishaw	4–10 wks

Encoderschematic

Compute (SoC / GPU)

the robot’s brain · logistics: export controls

Type / option	Used when	AI throughput	Power	Toolchain	Availability	Cost	Suppliers	Lead
NVIDIA Jetson / Thor★	most humanoids’ brain	high	med–high	mature (CUDA)	constrained	●●●	NVIDIA	8–20 wks
Tesla FSD SoC	Tesla Optimus only	high	efficient	closed	in-house	●●●	Tesla	n/a
Qualcomm / edge SoC	lighter cobots	medium	low	growing	good	●●●	Qualcomm	8–14 wks
Custom ASIC	high-volume production	tuned	lowest	build-it	NRE-heavy	●●●	fabless	6–12 mo

Compute (SoC / GPU)schematic

Battery pack

energy + power delivery · logistics: hazmat (UN38.3), duty

Type / option	Used when	Energy density	C-rate	Safety	Cost	Cost	Suppliers	Lead
Li-ion NMC★	most mobile humanoids	high	high	medium	medium	●●●	LG, Samsung SDI	6–12 wks
LFP	safety-first, stationary	medium	medium	high	low	●●●	CATL	6–12 wks
Li-Po	lightweight prototypes	high	high	low	medium	●●●	Molicel, many	4–8 wks
Solid-state	next-gen (future)	very high	medium	high	very high	●●●	emerging	R&D

Battery packschematic

Structure / frame

the load-bearing skeleton · material choice · logistics: bulky; Mg 85–90% China

Type / option	Used when	Strength : weight	Machinability	Fatigue	Supply risk	Cost	Suppliers	Lead
Aluminum★	main frame & housings	high	excellent	cracks	low	●●●	CNC shops	4–8 wks
Steel	shafts, gears, fasteners	medium	good	excellent	low	●●●	CNC shops	4–8 wks
Titanium	critical joint carriers	very high	poor (galling)	good	medium	●●●	Ti mills	6–12 wks
Magnesium	mass-critical limbs	very high	thixomolding	good	high	●●●	Mg (China)	8–14 wks
Composite	long limb segments	highest	forming-limited	impact-sensitive	medium	●●●	layup shops	8–16 wks
Polymer	covers & cable routing	low	excellent	good (damping)	low	●●●	injection molders	4–10 wks

Structure / frameschematic

PCBs & harness

power + signal distribution · logistics: light / air

Type / option	Used when	Movement zones	Current	Reliability	Cost	Cost	Suppliers	Lead
Rigid PCB	compute & power boards	static only	high	high	low	●●●	JLC, TTM	2–6 wks
Flex PCB	wrists, fingers, neck	flexes	medium	medium	medium	●●●	JLC, TTM	3–6 wks
Rigid-flex★	articulated joints	at joints	medium	high	high	●●●	TTM	4–8 wks
Wire harness	torso ↔ limb runs	anywhere	high	connector-dep.	low	●●●	Molex, TE	2–6 wks

PCBs & harnessschematic

Proprioceptive sensors

balance + force feedback · logistics: light / air

Type / option	Used when	Measures	Accuracy	Bandwidth	Cost	Cost	Suppliers	Lead
IMU (6/9-axis)★	torso balance	orientation, accel	med (drift)	high	low	●●●	Bosch, TDK	4–8 wks
6-axis F/T sensor	wrists & ankles	contact force/torque	high	high	high	●●●	ATI, Aidin	6–12 wks
Joint torque (strain)	each actuator	joint torque	medium	medium	medium	●●●	in-house	6–12 wks
Motor-current estimate	every motor (free)	rough torque	low	high	~free	●●●	firmware	n/a

Proprioceptive sensorsschematic

Tactile skin

touch sensing · logistics: light / air

Type / option	Used when	Spatial res	Durability	Maturity	Cost	Cost	Suppliers	Lead
Optical (GelSight)	fingertips (research)	very high	medium	research	high	●●●	GelSight	R&D
Piezoresistive	palms & grippers	medium	medium	some	medium	●●●	emerging	varies
Capacitive	hand surfaces	med–high	medium	some	medium	●●●	emerging	varies
Magnetic (Hall array)	robust fingertips	medium	robust	emerging	medium	●●●	Contactile	varies

Tactile skinschematic

End effector (hand)

manipulation · logistics: standard freight

Type / option	Used when	DoF	Dexterity	Payload	Cost	Cost	Suppliers	Lead
Parallel gripper	industrial pick-and-place	1	low	high	low	●●●	many	4–8 wks
Underactuated hand	general grasping	few	medium	medium	medium	●●●	in-house	8–12 wks
Tendon-driven dexterous★	human-like hands	many	high	low–med	very high	●●●	Shadow, Wonik	8–16 wks
Fully-actuated hand	research dexterity	many	high	medium	very high	●●●	in-house	12–20 wks

End effector (hand)schematic

Ranking reflects share of BOM cost, engineering difficulty and how often the part is the industry bottleneck. Options, suppliers and lead-times are indicative examples for comparison, not live quotes. Source: “Humanity’s Last Machine” — a component-level map of humanoid robotics hardware.

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