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Another Pan/Tilt Question For Camera Control

Hi folks,

I've searched this forum and found some information related to my question, but I'm still experiencing some problems.

The vertical on my pan/tilt camera set-up is having some problems. It still bobs and flops up and down. Sometimes it locks in an up or down position. I don't know if the blue servo just isn't strong enough, or if there's a problem with my set-up.

I replaced the horizontal blue servo with one from the EZ kit, because the first seemed too flimsy. The horizontal tracking for face and color works great.

I uploaded my project file in-case anyone has time to investigate. But it seems fairly simple. I attached a picture of my set-up too. Many thanks!

My1stEZRobot.EZB


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Synthiam
United Kingdom
#1  
Those little blue servos are ok for pan but any weight and it struggles to beat gravity in my experience. Does it make a lot of noise when it's trying to tilt up?
#2  
It does sometimes. But usually it'll flop up or down and then be locked in that position. I think I'll replace with a black servo, give that a try.
PRO
Synthiam
#3  
First, you need to upgrade your copy of ARC. The version you are running is quite old. Everytime you load ARC, you will be notified of a newer version by a flashing control. You will need to change the camera resolution before you can upgrade, however.

Follow these instructions to upgrade...

1) Load ARC

2) Load your project

3) Change your camera resolution to 320x240

4) Save your project

5) Close ARC

6) Upgrade ARC, Download and Install a more recent version

7) Load ARC

8) Load your project


Now, as for your Y axis camera tracking issue... You may need to use the Invert option, but i'm uncertain of that yet. It depends on the direction that the camera moves when it tracks the object.

Also, check the servo port is correct. The Y axis servo is specified for D1, and the others seem to be D17, D18, and D19.

The little servo is fine for the weight. They do break easily if you force their movement by hand, or move past their limit. Always use the servo Calibration tool (found in the tutorial) when attaching things to a servo. The servo Calibration simply centers the servo, so you can predict it's limits.

If the is "flopping" the weight, perhaps one of the gears inside is stripped. If the servo is "moving" toward a direction and holding it's weight, than it's most likely a configuration issue.
#4  
Thanks for the help. I upgraded. I also took the camera out of the aluminum housing and mounted just the board to the pan-tilt. The vertical seems to respond a little better. Maybe my expectations for this are too high. It still isn't tracking vertically very well. I'll keep tinkering. I set the horizontal port to one I wasn't using for now, so I could debug the vertical.


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PRO
Synthiam
#5  
Your expectations should be very high:)
United Kingdom
#6  
I have to say, echoing what Rich said, I found the same problem when using the lil' blue servos. Pan was working fine, but tilt was like a piece of wet lettuce. I assumed it was a lack of oomph from the blue servos. I never did resolve it, though.
PRO
Synthiam
#7  
I haven't seem to experienced that issue. Very strange that you would. Usually it's a case of misconfiguration:)

Poor lighting is usually an issue with face tracking.

Also, I'm starting to get away from mounting the camera on the servo. I'm starting to mount the camera stationary and use the "Relative Position" option in the Camera Config. Who says robot's need their eyes on their head?:)
United Kingdom
#8  
So that's what "Relative Position" is for then, I always wondered (all I knew is the head didn't move correctly when it was ticked).

I know I paid next to nothing for my little blue servos and suspect they may be of a lesser quality than what is suggested on the label... in other words, cheap Chinese knock-offs.

The TG9e should have 1.5kg/cm of torque so should be able to tilt the camera in the housing.

If all settings are correct and lighting levels OK check the power supply is providing the EZB with enough voltage and check the bracket isn't stiff to move - I had a similar bracket which was rather stiff when I put it together (I expect I put it together wrong).
PRO
Synthiam
#9  
@alphapepper I should also add that you may need to tweak the grids. When the resolution is changed, the grid's will be wacky. You want each grid to occupy 1/3 of the screen. When an object is across any grid, the servos will move to keep the object in the center of the grids.

Also, not sure if i need to tell you this... but Movement and servo tracking both enabled will not work. Moving the head while moving the body is impossible to do together... Unless Relative servo tracking is used with a stationary camera.
#10  
DJ, thanks for getting back to me. So to test my understanding: I have the radar enabled which is controlling my movement (object avoidance). That works great. But I can't operate that and the Camera servo Tracking (Pan, Tilt) at the same time?
PRO
Synthiam
#11  
If your robot is moving while it is trying to follow and object with the head, can you imagine what will happen?:) The object is moving, the robot head is also trying to keep it centered. It's like running while reading a book
#12  
Okay, got it. The problem I'm seeing with the vertical tracking is while it's stationary. I'm going to tinker with it tonight. Thanks again.
PRO
Synthiam
#13  
Have you adjusted the Grid's to be 1/3 of the screen for each one?

I can assure you that once you have adjusted the grids, specified the min and max positions, adjusted the object color brightness... that it just works - like magic:)

What object are you attempting to track?

If you're sitting very close to the camera, some objects won't be tracked because they are too close. For example, if you hold a basketball in front of my face, i have no reason to move my eyes or my head to look at it - because it's right there in front of me:)

I hope that's making sense
United Kingdom
#14  
hi, i had the same problem and you have done what i done, you have the pan tilt on backwards. so i turned it around and it solved the problem. hope this helps

simon
#15  
I'm having a similary issue. I have blue 9g servos in a pan/tilt setup with brackets. The pan servo on D16 (the X axis) works great, I can track my face or color objects and (once I configured the grids) when objects are moved the tracking will center the camera on the objected.

The tilt servo on D17 (the Y axis) does not work as well. If I manually control the servo (via a vertical servo control element in ARC) I can move the head up and down pretty well. When the servo has to tilt during camera tracking it will move a little bit up to track an object but that's about it, then it pooters out and won't tilt up or down. Also when setting the min-max values in the camera control for D17 the tilt servo I can make the servo move to the extremes, but not back to a middle position. For example say I set my min position to 10 and my max to 90, but then change the max to 50 the servo does not go back up, it just make noise like it's trying.

But, if I switch to a vertical control servo element I can make the tilt servo move up and down and back to center.

My gut tells me the issue is in the 9g blue servo.
United Kingdom
#16  
It sounds like it could be that the servo isn't powerful enough, I had similar issues in Melvin's arms. I upgraded to Tower Pro MG90s with 6v external power and it worked much better.

Those 9g servos aren't all that strong. Pan will be fine but lifting anything, you may struggle.

Try an MG90 (or similar) and see if that's any better.
#17  
Rich, it look like the MG90's are size wise the same as the blue9gs but have metal gears. Would you say the size is about the same? Do you power all your servers via an external source?

I would agree with you, pan works great, tilt is a little weak. BUT.....

I took a fresh start at the Pan/Tilt camera controls, re-tested the servos for centering and re-adjusted the grids via a ruler and low and behold my little bot is tracking my face and blue wire guard and motion like a champ. :D

Redoing the grid layout helped a TON. Eyeballing it I thought I had the grid in 3rds but when I used a ruler I could see I was very uneven. I vote for AutoGrid in the next release :D
United Kingdom
#18  
MG90s are the same size, give or take 1mm. I swapped mine with no problems and they went in a tight space.

Setting up the camera will help a lot with tracking, as will servo speeds. Mine are set to 3 which makes it smooth but experiment, you may need 2 or 4 or maybe something way different.

You could just power the blue ones with 6V to see if that helps (if they go bang don't blame me though, I haven't tested or looked them up to see their voltage ratings).

Yes, all of my servos are now externally powered to save from browning out. It's a little more work, a little more wiring and a bit more hardware but it's worth it in my opinion.