hipcover_assembly_instructions.md

Hip Cover & Cable Harness Sub-Assembly

[TOC]

Overview

The hip cover is a complex scaffolding and wiring structure that tunnels power and signal from the torso of the robot into the trimotor assemblies and back.

NOTE: In the partially-assembled robot below, we have a Front Right leg (screen left) with the hip cover installed compared to a leg sans cover (right side). The entire hip cover and cable harness sub-assembly is highlighted purple.

This is the path upon which ECAT signal travels down. It starts from the torso, and next proceeds into the abduction, then into the hip, and finally terminating at the knee before returning to the torso.

NOTE: An inside and outside view of a hip cover and its cable harness assembly. Parts have been highlighted to group them with regards to direction & orientations. Everything highlighted BLUE resides inside the hip.
RED is used to denote the external hip features.
The GREEN bundle travels through a center hole in the cover into the knee.
And the YELLOW group funnels through the topside hole into the torso.

And it comes in FOUR DISTINCT BUILD CONFIGURATIONS:

1. FL (Front Left)
2. HL (Hind Left)
3. FR (Front Right)
4. HR (Hind Right)

This dictates the specific lengths of cables needed to cross over the physical space inside the robot in order to reach power and communication.

Parts Needed

Separating the inventory chart into three distinct "chunks" so we can better parse how the disparate power and signal cables come together based on the specific assembly configuration we are making.

EtherCAT Cables

Five cables are involved in I/O for the EtherCAT signal.

Part Name	Quantity	Description & Details
A2H ECAT	1	Transfers data from Abduction to (2)
: : : Hip Gebru; Cable 15 :
H2K ECAT	1	Communication between Hip to (2)
: : : Knee PCBAs; Cable 16 :
K2H Cover ECAT	1	One half of the "return cable" from Knee
: : : through the Hip *and back into the :
: : : torso*; Cable 17 :
Hip Return SS ECAT	1/0	Second half of the "return cable"; used if
: : : the following leg is on the Same :
: : : Side; Cable 18 :
Hip Return OS ECAT	0/1	Alternative complement for "return cable" if
: : : the next joint is on the Opposite :
: : : Side; Cable 19 :

WARNING: Front Left (FL) and Rear Left (RL) have special incoming and outgoing cables dependent on the (DFB) that are NOT LISTED HERE (see cable drawings). The reason being that FL and RL are the first and last limb in the ECAT chain, respectively.

Power Distribution Cables

Three distinct cables are used for power distribution.

Part Name	Quantity	Description & Details
Hip Power Distro	1	Cable 4; plugs directly into the Fei-Fei PCBA
: : : so **all build configurations will use ONE of :
: : : these** :
Fei-Fei to A+H FR	1/0	Distributes power to Abduction and
: : : Hip; exclusively used for FRont legs; :
: : : Cable 2 :
Fei-Fei to A+H RE	0/1	Only for REar cable assemblies; Cable 3

WARNING: Do not repair faulty cables. If a pin is loose or sleeving is damaged or connectivity is suspect, cut and throw away the cable.

Mechanical Parts

The mechanical components will be the same regardless of the previous cable combinations.

Part Name	Quantity	Description & Details
Hip Cover	1	3D printed part that shields the hip
: : : PCBA; :
Cable Clamps	2	Complementary archpieces to the hip
: : : cover that serve as cable retention :
M3x12mm FHCS	4	Countersunk bolt that secures the
: : : cable clamps into the hip-cover heat :
: : : inserts :
Braided Cable Wrapping	as needed	For organizing the cable bundles; we
: : : cut two pieces per harness: 180mm x1 :
: : : and 250mm x1 :
Torso Grommet	1	Paired 3D-printed parts that retain
: : : the bundle to torso :
M3x10mm SHCS	2	Secures torso grommet mated pieces
Knee Cable Entry Gland	1	Two mated 3D-printed pieces that
: : : retain the cable running into the :
: : : knee :
M3x18 FHCS BO	2	Counter-sunk bolts that keeps the
: : : knee gland parts together :

Procedure

1. Combine the appropriate power cable pair and affix it to the left side of the internal Hip Cover.

   A. Staring with various empty Hip Covers. In this example we've already specified limb designation in advance for the entire batch based on build need.

   

   NOTE: We have a cover meant for a Front Left leg so the following procedure will be based on that particular build configuration. The necessary heat inserts should already be installed.

   B. It will receive the corresponding pair: x1 Hip Power Distro and x1 Fei-Fe to A+H FR

   C. Secure the junction of the power cable pair with a zip-tie around the XT60H-M(ale) connector as shown. Slowly tighten with a zip-tie gun to approximate tightness setting: 2.5

2. Assemble the corresponding ECAT "return cable" duo and affix it to the right-side slot of the internal Hip Cover.

   NOTE: Mark all ends with their corresponding Input or Output (arbitrary designation) so they don't get mixed up or plugged in the wrong direction once finalized.

   A. The current limb is Front Left (FL). Therefore the following joint must be Front Right (FR), which is on the SAME SIDE. Thus we use the required x1 K2H Cover ECAT along with a x1 Hip Return SS ECAT

   NOTE: The "return cable" with a mark to denote the junction between a K2H cable and either a SS or OS cable, depending on what specific leg comes next.

   B. Secure the junction on the remaining right-side slot with a zip-tie across the Molex 2014441110 as shown and tighten to spec like before.

3. Slot in the Abduction (output side) to Hip (input side) Ethercat cable.

   A. A2H ECAT goes in through he topside hole from the outside.

   B. We zip-tied it on the external side to preserve bundle length.

   It will need ~3 inches into the motor in order to properly reach the hip Gebru.

4. Install the Hip (output end) to Knee (input) Ethercat cable. A. The H2K ECAT cable will tunnel from inside the hip cover and through the middle opening to the outside.

   

   B. This goes further downstream into the KNEE joint, which is last in the trimotor chain.

5. Wrap and secure the external cable bundles.

   A. Cut a pair of braided cable sleeving to lengths of 180mm and 250mm.

   B. Wrap the external cable bundles as shown.

   NOTE: The shorter 180mm length will exit to topside hole and run towards the torso. The longer 250mm variant covers the cables coming out from the center hole and into the knee.

   C. Ensure the ends of the bundles are slightly crossing through the openings so the clamps will secure them in the following step.

   D. Each hole exiting the hip cover has a complementary clamp piece that is secured with x2 m3x12mm bolts. Tighten until the cable feels anchored.

NOTE: For the following steps we'll be applying the additional scaffolding for the cable bundle outputs. In the below example we have a torso grommet pair (left) and the knee gland assembly. (right). Prior to the installation we cut out two aluminum rods to 120mm and 190mm in order to serve as "rulers" to ensure enough slack for cables to reach their intended destinations.

1. Install the Torso Grommet {value=6}

   A. Confirm distance before marking and clamping. Make sure the cables aren't all tangled up inside the bungle, which could lead to pinched wires.

   B. Also consider the ORIENTATION of the mated halves, as they need to be installed as shown to easily slot into the torso with minimal cable strain.

   C. Clamp the halves together, aligning openings to heat inserts, and screwing down x2 M3x10mm bolts to hand-tightness.

2. Apply Knee Entry Gland

   A. Measure distance and access cable "health" as before.

   B. Confirm orientation of the knee gland pieces with respect to the cable bundle, as shown:

   WARNING: The knee gland pieces can be connected incorrectly. This creates a much tighter opening which can damage the cable bundle going into the knee on top of not properly fitting into the joint it's traveling towards.

   C. Clamp down the knee gland pairs and fasten the x2 M3x18mm bolts to hand-tightness.

NOTE: Example of a completed Front Left (FL) hip cover & cable harness sub-assembly. REMEMBER: there are minor differences with regards to cable lengths, combinations, and port orientation depending on which specific leg you are building for.