My Creation! His name is DR-6

[UncleBob]

Do you have photo or video, want to see why it can't go forward.

[mic2]

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

[xx2747]

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? .

[Rick_swarty]

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.!

[mic2]

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

[mic2]

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

[mic2]

Videos updated! see page 1

[billyzelsnack]

Very very nice.

[mic2]

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.

[mog123]

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.

[billyzelsnack]

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.

[mog123]

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.

[bonmot]

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.

[mic2]

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,

[billyzelsnack]

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.