Author Topic: robotic hand  (Read 767 times)

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Offline sesco-lbTopic starter

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robotic hand
« on: June 23, 2013, 01:13:58 PM »
hey there, i am planning to build a tactical robot with robotic hand with high torque and capable of lifting up to 20 kilos..... attached is the picture for reference.... I am planning to use the roboteq ax3500 dc motor controller to control the motors of the robot while the controller offers a 8 x pwm rc control outputs which i am planning to use for the control of the robotic hand...... i dont want to use hooby like servo motors due to limitations in power, size, shape and many more. i want to use normal big dc motor with servo drive and encoder etc..... so i cant find the suitable one.....

any help ? please if you can check the ax3500 specs of pwn output range must be suitable with the dc servo drive / motor i must get.

Offline jwatte

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Re: robotic hand
« Reply #1 on: June 23, 2013, 04:09:28 PM »
Quote
roboteq ax3500 dc motor controller

That's a fine controller to put power into a DC motor. It can also read quadrature encoders to figure out how fast the motor is turning. However, without other "homing" sensors, it's not possible to get the absolute position control out of that controller that you will typically need for a robotic arm.

Separately, 20 kilo lifting force times your arm length (looks like two half-meter segments?) plus lifting the arm itself (say, 5 kg) means 25 kg times 100 cm == 2500 kgcm torque, or 250 Nm. That's... a lot. You will want a motor with a gearbox, rather than a direct-drive motor, for this amount of torque.

Typically, at these power ranges, you will select the gearbox separate from the motor, and then integrate them yourself. Additionally, you will want to select a quadrature encoder, and some way of "homing" the main axles, to get the appropriate closed-loop absolute control.

Suppliers of industrial motors include Maxon and Kollmorgen and Dynetic and NMB. I'm sure you'll find something there if you go looking for an appropriate gearbox plus motor plus encoder combination.

Also note that the AX3500 is "not recommended for new designs."

Offline sesco-lbTopic starter

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Re: robotic hand
« Reply #2 on: June 24, 2013, 02:57:29 PM »
Umm... what do you recommend to use for such a robotic arm..... I mean for geared motors with servo drive and even a controller. ... knowing that the controller should have a lan interface.

Thank you.

Offline jwatte

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Re: robotic hand
« Reply #3 on: June 24, 2013, 03:55:17 PM »
You can buy an arm like this from industrial robot suppliers.

You can also build it with a variety of off-the-shelf robotics components.

Google for "industrial motion control" and you'll get a lot of hits from various motion control companies that have servo motors, encoders, controllers, and control networks (CAN, Ethernet, RS485, etc.)

I haven't had the opportunity to throw tens of thousands of dollars at my robotics projects, so I haven't done a deep investigation into what would be the best set of parts for this application.

Offline nanotechopolis_gr

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Re: robotic hand
« Reply #4 on: June 27, 2013, 01:56:18 AM »
20 kg its too much load ,in my opinion is that you will need high end servos like http://www.pololu.com/catalog/product/1390 but not only 1 maybe 3 or 4! its a lot of money project! my robotic arm can only lift 0.3 kg  :P
"On the 29th of May, the last day of the siege, our Lord God decided, to the sorrow of the Greeks, that He was willing for the city to fall on this day into the hands of Mahomet Bey the Turk son of Mu

Offline jwatte

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Re: robotic hand
« Reply #5 on: June 27, 2013, 01:48:30 PM »
You cannot do 20 kilograms over 50 centimeters with any servo sold on Pololu. You will need significantly higher-end gear (think "Kollmorgen" or "ABB" or "Bosch Rexroth" or "Emerson Industrial.")
Sorry if that wasn't clearly articulated in my previous answer.

 


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