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UncleBob
Savvy Roboteer
Joined: 27 Dec 2009
Posts: 221
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 Posted: Fri Feb 05, 2010 11:47 am Post subject: Vid |
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| Do you have photo or video, want to see why it can't go forward. |
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mic2
Savvy Roboteer
Joined: 01 Mar 2007
Posts: 85
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| Posted: Sat Feb 06, 2010 12:11 am Post subject: |
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| Rick_swarty wrote: | hai ........ sorry for my English is bad
your robot are very good in shape design ...
I really like the hands especially the fingers.
you can tell how to design a robot, especially in selecting materials and type of servo used ...
I have created a humanoid robot, but failed, I created a robot that can not go forward ...
I use aluminum material with a thickness of 0.8mm and I use servo HITEC type 311HD with torque around 3kg ..
I hope you can help me ...
thanks .. |
HI Rick,
Nice to meet you, in my opinion, before we talk about how to design a robot, first you’ll need to find out how well you know about humanoid robot and being understand how it works, what does it consist with to build a working 2 legs robot.
For a start, you should decide how tall your robot will be, because this will reflect what sort of servo you will need (as in size & torque) then find a controller board that can go with the selected servos. There are several common types of Controller board & Servos you can choose from e.g PWM or TTL etc.
Generally a hobby humanoid would be around 30 to 40 cm tall, since most of the robot servos & controller boards are designed to fit in this range.
According to the spec of the HITEC 311HD servo, size 40x20x36 mm with 3kg – cm torque are way too low between size and torque ratio. Let say you want to build a 30cm tall robot, you will need at least 7kg – cm torque servos to start with in order to get some stable walking motion.
For the aluminium sheet, I would recommend to use 1mm – 1.5mm of thickness, this will gives a good ratio between weight and strength.
Hope this help
mic |
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xx2747
Savvy Roboteer
Joined: 05 Jul 2009
Posts: 27
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| Posted: Sat Feb 06, 2010 5:54 am Post subject: |
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Hello once again...
right now im building a "cheap" humanoid with a goal set for under $400.
I use cheap chinese servos with (apperantly) 12kg torque and the SSC-32 from lynxmotion. I was thinking of using xbee to wirelessly connect to a pc and dont have any brains in the robot. (more processing power, memory and speed).
just... here: http://forums.trossenrobotics.com/showthread.php?t=3476&page=6
Anyways, I was wondering what servos you were using and some specs. I'm sure they're really expensive japanese servos right?  . |
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Rick_swarty
Newbie
Joined: 01 Jan 2010
Posts: 2
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| Posted: Sat Feb 06, 2010 3:14 pm Post subject: for mic2 |
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thank you for the information mic2.
I designed a robot that has a height of about 40-50cm ..
if you know the reference books or websites that discuss the design and detailed calculations to compute the torque on a humanoid with a certain size, please help me?
I plan to make a humanoid for my thesis.! |
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mic2
Savvy Roboteer
Joined: 01 Mar 2007
Posts: 85
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| Posted: Sun Feb 07, 2010 6:33 pm Post subject: |
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| xx2747 wrote: | Hello once again...
right now im building a "cheap" humanoid with a goal set for under $400.
I use cheap chinese servos with (apperantly) 12kg torque and the SSC-32 from lynxmotion. I was thinking of using xbee to wirelessly connect to a pc and dont have any brains in the robot. (more processing power, memory and speed).
just... here: http://forums.trossenrobotics.com/showthread.php?t=3476&page=6
Anyways, I was wondering what servos you were using and some specs. I'm sure they're really expensive japanese servos right? . |
Nice to see you again,
Interesting! What program do you use to control those servos? Hmm.. 12kg torque is good enough for the size of your robot, what is the dimension of those cheep servo?
On mine have 4 different types of servos, 9.2, 28.5, 7.5 and 2.6 kg-cm. Yes they are expensive Japanese servos 
Good luck to your project, please post some video later to see both legs working together 
Last edited by mic2 on Sun Feb 07, 2010 8:12 pm; edited 2 times in total |
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mic2
Savvy Roboteer
Joined: 01 Mar 2007
Posts: 85
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| Posted: Sun Feb 07, 2010 8:03 pm Post subject: Re: for mic2 |
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| Rick_swarty wrote: | thank you for the information mic2.
I designed a robot that has a height of about 40-50cm ..
if you know the reference books or websites that discuss the design and detailed calculations to compute the torque on a humanoid with a certain size, please help me?
I plan to make a humanoid for my thesis.! |
The fact that, the taller the robot, the more it will cost to build and more difficult to get it walk stably.
For a 40-50 cm robot you will have to user some high torque servos like 25 kg – cm or above (Usually very expensive)
Remember when choosing a servo for “Thigh roll axis” (See my servos layout), get some good high torque servo for it. This will help to keep the leg off the floor while walking. Otherwise if you use some low torque servo, your robot will move forward but both legs a hardly off the ground!
This might help, http://robosavvy.com/forum/viewtopic.php?t=2243&highlight=book |
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mic2
Savvy Roboteer
Joined: 01 Mar 2007
Posts: 85
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| Posted: Sat Feb 13, 2010 1:03 am Post subject: |
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Videos updated! see page 1  |
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billyzelsnack
Savvy Roboteer
Joined: 30 Dec 2006
Posts: 509
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| Posted: Sat Feb 13, 2010 1:39 am Post subject: |
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| Very very nice. |
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mic2
Savvy Roboteer
Joined: 01 Mar 2007
Posts: 85
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| Posted: Wed Feb 17, 2010 9:37 pm Post subject: |
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| billyzelsnack wrote: | | Very very nice. |
Thanks I have used a similar walking style call “SHIN-Walk” from Robot Laboratory CHROINO robot.
http://www.robo-labo.jp/english/robot_intro/chroino.html
Which aim to give more naturally walking motion than traditional robots that walk stiffly with constantly bent knees. |
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mog123
Robot Builder
Joined: 30 Jan 2010
Posts: 20
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| Posted: Sat Mar 06, 2010 10:39 pm Post subject: |
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| Your creation is really swell. I only want to note that the "2servo" knee isn't just for flexibility. It's main role is to eliminate servo backlash, divide some of the torque, and improve knee-bending speed. |
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billyzelsnack
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Joined: 30 Dec 2006
Posts: 509
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| Posted: Sun Mar 07, 2010 12:53 am Post subject: |
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I understand how dual servo knees doubles the knee speed, but how does it increase knee torque? Each "half" of the knee would still only be capable of each servo's maximum torque output.
I would think that servos in series double the speed and maintain torque and servos in parallel would maintain the speed and double the torque. |
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mog123
Robot Builder
Joined: 30 Jan 2010
Posts: 20
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| Posted: Sun Mar 07, 2010 4:21 pm Post subject: |
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| billyzelsnack wrote: | I understand how dual servo knees doubles the knee speed, but how does it increase knee torque? Each "half" of the knee would still only be capable of each servo's maximum torque output.
I would think that servos in series double the speed and maintain torque and servos in parallel would maintain the speed and double the torque. |
I didn't say that it doubles, but divides a bit. |
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bonmot
Robot Builder
Joined: 21 Mar 2007
Posts: 17
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| Posted: Mon Mar 08, 2010 2:14 am Post subject: |
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Hi Mic2
Nice job! I am into robotics now, have been thinking about it for years!
I have the same questions about the robot size.
I am thinking about this servo:
Turnigy HV-300 Digital HV-3S Servo 38.40kg/ .130sec / 79g.
What's the reasonable size of the robot I can built based on your rule of thumb. |
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mic2
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Joined: 01 Mar 2007
Posts: 85
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| Posted: Tue Mar 09, 2010 12:48 pm Post subject: |
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| bonmot wrote: |
I am thinking about this servo:
Turnigy HV-300 Digital HV-3S Servo 38.40kg/ .130sec / 79g.
What's the reasonable size of the robot I can built based on your rule of thumb. |
Hi bonmot,
Good price for a Coreless digital servo with Turnigy Alloy case and Titanium gear, refer to the spec of the servo @ (8.4V) - 26.90 kg.cm and @ (12V) - 38.40 kg.cm. Let say you are using 3S li-po battery, the operate voltage would be above 11V and then drop down to somewhere near 8.2v (When Fully discharged Power cut-off point) i.e. around 34 – 25 kg.cm torque, refer to the size and the torque of the servo you could build a robot around 40-52cm tall, depends how light the top half of the body can be. I would suggest using some small light weight servo for the top half of the body. This will reduce servo backlash problem when it is at high speed motion, as well as allowing you to build a taller robot.
However make sure you have made a lot of test between the controller board and the servo before getting into the design stage. E.g. Accuracy, speed, respond time, stress testing (run it at high speed with full travel to see when the body temperature goes up etc. this should give you some ideas of how the performance of your robot can be.
Hope this help
Mic,
Last edited by mic2 on Tue Mar 09, 2010 5:30 pm; edited 2 times in total |
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billyzelsnack
Savvy Roboteer
Joined: 30 Dec 2006
Posts: 509
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| Posted: Tue Mar 09, 2010 2:13 pm Post subject: |
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| Why do you say.. drop down to somewhere near 8.2v? To take in account the voltage of the battery under load? From my understanding Lipo's should easily hold above 3.2v/cell under load, especially in robotics applications which require much less continuous and surge current compared to typical RC applications. |
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£158.95 inc. VAT
