How to

A RoboCup approved Current Best Approach Guideline

This document is intended to help you repair the neck tilt joint of a Sony Aibo ERS-7 yourself. The weak point of that joint is a (black) gear wheel that is barely mounted to the neck limb. The grey plastic of the frame quite often crumbles away after some strains.
At first, the head will get more and more slacky. Then the gear wheel will completely loosens from the neck. The neck tilt isn't movable any more and the head just dangles down. I assume that all ERS-7 robots that have been used in RoboCup games for a couple of time got at least some wearout at this point. Already after first slackness in head joint, you can be sure of the defect described and should fix it by glueing the head.
The following guide shows how to fix this problem by glueing the gear wheel back in place. Afterwards the joint should work exactly in the same way as a brand new one.

Sony Aibo Clinic would exchange a complete head with such a defect. That's very expensive and maybe take some time until you get your robot back again. Another advantage of the method shown is, that a further defect was never observed with repaired neck joints.

Anyway you should also be aware of the risks of the procedure. Don't do it, if there's warranty left on your device - otherwise you will void it. Make sure you carefully read the instructions, get the appropriate tools and work space. Although it's possible to follow the procedure on your own, it's recommended to ask one person to assist - especially if it's the first time you do it. We are not responsible for any damage caused by following this guide. You're acting on your own risk!

If you have doubts, don't do it. If you do it, have no doubts! ;-)

You'll need:

- screwdriver set
- two-component adhesive, epoxy casting resin or some similar strong glue
- spatula or plastic knife to spread the glue
- about one hour of time (not including time for the glue to dry)
- second person to assist recommended

also useful:

- soldering iron
- small screws
- camera

It might be nice to take pictures of the steps you're doing. If you got better fotos than the ones in this guide, you're welcome to send them to me.
I am especially interested in pictures of broken aibo parts and non glued gear wheels and aibo necks.

The fotos also might be very useful, when you're reassembling the robot ;-)

First you have to remove the Aibos body case and should also remove the front legs.
Please find a short instruction here (Removing the front legs isn't really necessary but makes thing easier).

Then it's recommended to put all screws and parts you removed so far in a plastic box and away of your working space.
Especially the screws. You will have to remove lots more from the head and it's nice to keep them separate.

Removing the head

Remove the power button using a small screw driver to lift the nozzle. Remove screw and covering.

Remove the marked screws and the flatcable. You can just pull it off carefully.

Carefully remove the shutter. Don't brake the bracket! Unplug the PSD sensor (plug shown on next picture).
Hint: Move the shutter from back to front to free it from the runner. Then pull it up and carefully bend it to the outside and free it from the pin.

Remove screws and the small metal frame.

Remove plugs and screw if not done already. Lift neck tilt metal case at the back side over the thread flanges.

Lift case over the screw sockets at the front side. Remove head and all plugs leading from body to head if not done already.
Be careful, don't break any pins.

Remove the tape and the 5 screws of the plasic case.

Carefully remove the potentiometer. Use a small screwdriver. Lift the orange cable - not only the plastic elements.

Remove the two screws of motor fixture. Don't lose the fixture rings (small black plastic rings).
By the way: Never drop screws on the floor unless you find them again!

Imortant:
When reassembling the head, think of the fixture rings and don't damp any flatcables.
Make sure, you lead them through the correct openings.

Glueing the gear

Free the gear wheel and the neck tilt from dirt and plastic dust.
Bigger elements that broke from the frame could also be cleaned and glued back to their position.

Put the wheel and the neck tilt together and check if it fits. Find the position to glue it.

(Depending on the damage of your Aibo, you could use a solderin iron to weld small holes into the gear wheel and maybe the plastic neck frame, in order to add small metal screws or something similar to provide more stability. Decide yourself whether to prepare that before using the glue.)

Put the glue to the neck tilt and the gear wheel according to the guidance of the glue you're using.
Keep it fixed together and wait until it sets hard.
You should use extremly strong glue. We recommend a two-component adhesive or epoxy casting resin.
However something you really shouldn't contact with your skin (therefore you might use your assistant or the plastic knife).
Don't add glue to other parts - put them far away in advance.

Think again of adding screws but don't spoil your soldering iron with adhesive.

Work carefully - probably you will only have one chance to glue the gear wheel - it shouldn't ever get loose again!

Glued gear wheel - additionally fixed by screws.

Reassembly

Reassemble everything. After adding the legs you can do a test run and see if the head is working fine or if you missed a plug or something.
Don't worry, if you have screws left in the end. Try to follow the pictures and find the steps where you missed them.
Worry if you have screws missing. Repeat the procedure with another robot and you might eventually find screws left over.
Or, even better, have a close look to the robot limbs and case elements - maybe the screws can be found there.

Don't be shocked. Although this might look frightening in the first place, it's a common procedure with some RoboCup teams and several robots have already been repaired successfully that way.

You're welcome to ask any questions on this method and also send pictures of your work and defective parts.

 

Jörg Zimmer
Technische Universität Darmstadt
RoboCup 4-legged-league
Darmstadt Dribbling Dackels and GermanTeam