Robot Harness and PCB

Joint actuators

How is the wire gauge chosen?

Chain current is joints x per-joint peak current x simultaneity. The tool walks the AWG table from thin to thick and picks the first gauge whose derated ampacity covers that current and whose round-trip voltage drop stays inside your limit. Resistance is corrected to the conductor temperature with copper's 0.00393 per C coefficient.

Why are actuator currents treated as an upper bound?

The published peak currents for the Unitree and CubeMars actuators track torque through the torque constant, so they are motor phase currents. The DC current a drive pulls from the bus is lower, so sizing the supply wire on phase current errs on the safe side.

How does the URDF estimate work?

The file is parsed in your browser. The tree is split at its branch points, so each actuated joint belongs to one chain: a shared trunk such as a waist gets its own row, and fixed sensor or contact frames do not start a chain. Length is the sum of joint origin offsets up to the last actuated joint, times a routing factor (default 1.3, an assumption). Continuous joints are flagged for a slip ring, and identical chains fold into one row with copies.

How accurate are the impedance numbers?

They use the IPC-2141 closed forms, valid for w/h from 0.1 to 2.0. They ignore solder mask, etch shape and glass weave, so treat them as a starting width and check with a field solver and your fabricator's stackup.

How is the skew budget turned into length?

Unit interval = bits per symbol / line rate. Allowed skew is a share of the UI, and length = skew / propagation delay, with delay from the IPC paper S08-3 formulas: 85 x sqrt(0.475 Er + 0.67) ps/in for microstrip and 85 x sqrt(Er) ps/in for stripline.

Everything runs in your browser. Nothing you type or drop is sent anywhere. See also the Robot Interconnect Budget and URDF Inspector.