Asked — Edited

Backwards Or Is It Just Me

So I have my JD assembled and sort of running, as I was working on the walking frames I noticed something odd. When I have the edit frames window open and I am looking at the assembled JD in the front view. The servos on the left, that would be my left as I am facing the JD are moving opposite in direction from the servos on the right. So for example if I click the left servo directly below the main body (his left hip) and drag the mouse up towards the top of the window the servo moves forward towards me (it leans his body towards me) If I do the same thing to the the right hip servo it leans his body away from me. To my mind it would seems like they should both move in the same direction. IE an upward drag on either would move either one towards me. Maybe I am missing something here.....I also noticed it is the same with the knees and the arms and shoulders. I did the initial calibration of the servos and created a servo profile and all that. Most of the motions like a wave and a bow seems to be working right. Although his walking and sitting motions are really rough. I have double checked my assembly and that seems okay so for example on his legs the servo horns are all facing in and on his arms they are all facing up or forward.......Any thoughts?


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The photo is him facing you, so all servos are relative to his position. So servos on the RIGHT of the image are his LEFT. Notice how his face is toward you. Go to a mirror and raise your right hand:D

The moving of the servos is moving the degrees - there is no reference to degrees. 10 degrees is the same for any servo in any position.

A servo is specified in degrees. The degrees are between 1 and 180. If you move a servo to 90 degrees, it will look the same from any direction that you look at it. But if you move a servo to 70 degrees, it will look different from each angle.

How about this. If you open your door 30 degrees, it will look different from the inside or outside of your house. It depends on what side of the door that you're standing on. Does that make more sense?

Guess it's something that not a lot of people use in the real-world, but degrees are relative to the source of the arc.

What are you stabbing in your photo? Better not be a robot!


Nope I get what you are saying let me ask it this way if I turn JD 90 degrees counter clockwise from the front view in the edit frames window so I am seeing his profile. His right hip is closest to me his head is 0 degrees and his feet being 180 degrees. When I drag the cursor towards the top of the window that servo moves towards 90 degrees and when I click on the left hip and drag up the servo moves towards 270 degrees. Is that the normal operation? It seems to me that they would both move in the same direction ie 90 degrees,

And yeah I am stabbing, a lobster, when I am not playing with robots I cook and when I am not doing either of those I inspect aerospace parts!


The servo doesn't know what direction it is facing relative to any other servo. 1 degree on every servo is same.

The only way a servo could know it's position relative to another servo position is if there was some sort of localized sensor. Or maybe a compass and accelerometer built into the servo. Then each servo could report it's position and placement so the software could understand it.

Of course, it technically is possible for us to create servos with built-in accelerometer and compasses - but they would cost a pretty penny:D

I suspect the areo space industry may be able to afford servos with built-in sensors:) Maybe we should get into that industry!


I realise the servos are each independent of each other. I think my question is more basic than that, so let me try it this way. Once again with the hip servos, an upward drag on the screen should produce a servo movement in the same direction regardless of the hip servo selected, correct? So in other words an up drag on the screen would move which ever hip servo I select from 180 degrees towards 90 degrees, obviously independent of the other.

You would be surprised at how amazingly low tech Aerospace Manufacturing can be, I measure .0001 of an inch with equipment from 60 years ago, it's still very accurate but no where near as cool and flashy as robotics. LOL if you were to take a look at G code which we still use to program CNC machines compared to your software, it would be like comparing the Wright Brothers plane to the Space Shuttle!


Moving up will increase the degrees and moving down will decrease the degrees.

The direction that the servo moves is based on the way it is mounted. 1 degree is the same direction for every servo ever made. 180 degrees is also the same direction. Now, keep in mind that not all servo manufacturers and models work in degrees, so it's not always the same position but it is the same direction.

So if you move the slider UP, then the number on the screen that you're moving is the degrees. The degrees will increase, such as 1... 2... 3... 4... 5... all the way to 180. And if you slide the numbers in a decreasing order, for example 180, 179, 178, 177, etc.. then the degrees will decrease.

So the number 1 on any servo control in ARC (this includes the auto positioner) is degree 1. And a 180 is degree 180.

The servos will move between 1 and 180 degrees with an increment of 1.


pictures or a video can be very helpfull.


Resolved this myself so how do I clear it?