During a break in the action at last weekend's ROBO-ONE events in Kawasaki we had a chance to chat with Kazz about setting up a KHR-1 robot, and the importance of the home position.
It turns out that everytime you download a new motion sequence from your computer to the robot, its RCB-1 controller uses the home position settings in its memory to translate your 'relative' servo positions into 'absolute' positions so that it can accurately move the servos.
For example, your motion sequence may have a servo move to -10 (approximately -10 degrees). The RCB-1 converts that to 80 (out of a range of 0-180) and offsets it by your home position setting for that servo.
If you're creating all your own motions from scratch, and don't have to change your home position settings, it might not ever be a problem for you. But if, like most people, you want to use the motion sequences from the manufacturer or from friends, a small difference in the home position setting can create problems.
Frequently a new user will try to use a new motion sequence, run into problems, and then will spend a lot of time trying to change the sequence settings to get them working properly for their robot.
When that happens, the first place to look is the home position setting. Sometimes just changing the settings by one or two ticks one way or the other is enough to solve the problem.
This is especially true for the ankle servos since just a one degree difference in their setting will shift the robots center of gravity quite a bit.
Along the same lines, if you notice that your robot in its home position seems to be tilting slightly forward or backward over time, chances are it's due to gear wear in the ankle servos.
Start by making just minor adjustments to the settings for those two servos until its standing vertical again. If you change several different servo settings all at once, you'll probably throw your existing motion sequences out of wack, and just end up frustrated.
This applies to the KHR-1 robot and similar designs. It may also apply to the KHR-2HV, though we can't confirm that since we don't have one to play with ... yet.