Page 1 of 4 1234 LastLast
Results 1 to 10 of 33

Thread: How to performance test servos?

  1. #1
    Join Date
    Aug 2008
    Location
    Iowa City, IA
    Posts
    390
    Rep Power
    43

    How to performance test servos?

    Over in the humanoids forum I've been blathering on about testing the Turnigy/MKS HV-300 servo. It makes much more sense for me to post over here in actuators.

    This is where I am at at this point..
    http://billyzelsnack-robotics.blogsp...-test-rig.html

    I'm most interested is seeing the relationship between the various types of torque ( dynamic, stall, and holding. ) I'm especially interested in seeing the dynamic torque on this particular servo as I know the dynamic torque of the AX-12 has been reported to be less than half its stall torque.

    If anyone has suggestions or ideas on the best way to go about this I would love to talk about it. Once I have the method worked out I'll test out some other servos as well.

    Also.. If anyone has any data on big boy servos such as the RX-64 ( or anything else ) I'd definitely appreciate seeing that too.
    Last edited by billyzelsnack; 03-16-2010 at 10:46 PM.

  2. #2
    Join Date
    Dec 2007
    Location
    Whidbey Island, WA
    Posts
    1,718
    Images
    456
    Rep Power
    94

    Re: How to performance test servos?

    OK...

    I think the first couple of things is to form a standard jig in which to measure various servos. I saw someone on the forum using a shop vice to hold the servo, and then using KG weights at the end of two back to back SES long servo brackets. That way they could vary the amount of load at a known torque arm length and test performance. I suppose you could mount a protractor behind the servo and measure specific angle movements to see how well it is hitting the mark, and use a stopwatch to test how fast it is moving both without, and under load.

    Finally, the test you did already isn't bad, but I would like to see you try it with smoother movements programmed. Right now it seams to move well, but I'm not sure how much of the jerkyness of the movement is the servo, and how much of that is the programming.

    Thank you for doing the testing you have done. I'm pretty stoked about these servos, and may pick up a couple.

    DB

  3. #3
    Join Date
    Aug 2008
    Location
    Iowa City, IA
    Posts
    390
    Rep Power
    43

    Re: How to performance test servos?

    My software is plain dumb at the moment. I just have 5 keys to set various positions. When it goes up in the video it's going from say 0 to 180. When it goes down I step it a little so the weight does not slam down as hard.

    This does bring up an issue. Should I be doing these tests at full speed? ( speed in the sense of interpolating target positions ) I guess I should do tests at a variety of different speeds.

    btw. Here's the test rig that vstone uses for their high-end servos..
    http://www.vstone.co.jp/top/products...vo/50kgfcm.wmv ( 5MB )

  4. #4
    Join Date
    Jan 2008
    Location
    Montreal, Canada
    Posts
    477
    Images
    63
    Rep Power
    53

    Re: How to performance test servos?

    That servo looks really good for the price!

    For your rig, I would also suggest clamping down or screwing the servo to something to make it stand still. It depends a lot on the precision you want to get from these tests. The bigger the wheel, I believe the better the precision you could get (let's say you have something like this)

    Your % of error would probably go down since the length is bigger. Get good weights and a way to hold them. I would also (if you can) suggest doing everything in metric (Kg, centimeters and newtons) then you can convert.

    If you have a SSC-32 you could program the same movement but slower and faster to see the difference. I'm not sure of your setting, but there could be a way of doing that.

    This is interesting, keep us posted!

    EDIT : Oh, do you know if the work with the SES?

    Sam

  5. #5
    Join Date
    Aug 2008
    Location
    Iowa City, IA
    Posts
    390
    Rep Power
    43

    Re: How to performance test servos?

    I'm planning on doing a setup that is solid enough to be repeatable over various speeds. I just threw together an Arduino so I'll be able to do the testing at various speeds. I'll probably make some graphs if the data looks interesting.

    I think you are right that the bigger wheel will be more precise. I'll see what I can find. I also will be changing my setup so the load is supported on both sides of the pulley to get rid of some of the side-load.

    It's funny.. I used to convert everything into ozf-in to so that I'd have some sort of mental concept of the torque values. No I find myself converting to kgf-cm. I feel much better now. haha.

    What's all this SES business people are talking about? I know it's Servo Erector Set, but I don't know how it's related. Do they have a bunch of pulleys available or something?

  6. #6
    Join Date
    May 2008
    Posts
    2,228
    Images
    155
    Rep Power
    124

    Re: How to performance test servos?

    Quote Originally Posted by billyzelsnack View Post
    What's all this SES business people are talking about? I know it's Servo Erector Set, but I don't know how it's related. Do they have a bunch of pulleys available or something?
    I think the question is: does this servo conform to standard sizes well enough to use SES parts on it (I may be wrong, but that's the typical question I see for non-hitec/futaba servos)

    -Fergs

  7. #7
    Join Date
    Jul 2008
    Location
    Chicago
    Posts
    307
    Rep Power
    44

    Re: How to performance test servos?

    Regarding the SES compatiabily there already is a new hitec that recently was released that is a little to big for the SES. There is a thread over at Lynxmotion that covers this.

    My guess is that the mounting pattern will never change on the servos. But the hieght size of the case might start to change. In time as performance is reguired as RC models get faster the servos that control them need to get stronger as well. The design of the gears will get beefier.

    If they released one there will be plenty more.

  8. #8
    zoomkat Guest

    Re: How to performance test servos?

    For testing the servo, I'd mount it on the edge of a table or shelf and attach the center of a long arm to the servo horn (equal am lengths on each side of the servo horn to balance out the arm weight). On the end of one end of the arm attach weights via a string. Start the servo with the arm straight down and let it move upward. When it finally stalls, measure the distance horozontally from the verticle centerline of the servo horn out to the centerline of the string. Multiply this distance by the weight of the weights to see the max torque being produced. Move the arm up to a more horozontal position and release. The arm should go down and stop. This should be the ~holding torque.

  9. #9
    Join Date
    Jan 2008
    Location
    Montreal, Canada
    Posts
    477
    Images
    63
    Rep Power
    53

    Re: How to performance test servos?

    That's a nice idea to get nice holding torque and holding torque!

    It could be a bit tricky to calculate the horizontal distance precisely thought, even if you decide to measure the angle and use trigonometry. But the setup could be easier.

    Oh and I'm pretty sure that servo won't fit with the SES.

  10. #10
    zoomkat Guest

    Re: How to performance test servos?

    It could be a bit tricky to calculate the horizontal distance precisely thought, even if you decide to measure the angle and use trigonometry. But the setup could be easier.
    Use a plumbob setup centerded at the center of the servo horn and hanging down. Then measure the horozontal distance between the two strings.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Question(s) what servos
    By Grand Robot Master in forum DYNAMIXEL & Robot Actuators
    Replies: 21
    Last Post: 06-10-2009, 08:48 AM
  2. Controlling Servos with a servo controller
    By bodhibuilder in forum Arbotix, Microcontrollers, Arduino
    Replies: 25
    Last Post: 09-29-2008, 11:07 AM
  3. HITEC Servos: Can the OEM RN-1 Servos handle 7.4V?
    By MYKL in forum DYNAMIXEL & Robot Actuators
    Replies: 10
    Last Post: 06-23-2008, 04:39 PM
  4. Easy Programing of servos and play back
    By hotrodled in forum DYNAMIXEL & Robot Actuators
    Replies: 1
    Last Post: 01-30-2008, 03:18 PM
  5. 1HV owner haveing problem with servos, help requested
    By Droid Works in forum Humanoids, Walkers & Crawlers
    Replies: 13
    Last Post: 11-08-2007, 01:55 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •