Author Topic: Getting started  (Read 1745 times)

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Offline CotowarTopic starter

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Getting started
« on: July 08, 2008, 11:00:42 PM »
Okay, heres the plan for my first build.

I want to build a self powering robot with 4 wheels, an actuating arm coming out the top, and enough power to be decently useful in everyday life. I was planning on controlling it with speech recognition, and I was thinking of adding various sensors as needed.

I'm not afraid of a serious challenge, and my mechanical prowess is pretty insane. I admit I do lack when it comes to circuitry, but hell, no one is perfect. I was planning on building out of steel, as I get a hella huge discount on all types of it, I have access to a wicked sweet TIG welder, and yea, I want a super duper strong frame. Programming doesn't scare me, as I am "fluent" in VB, FORTRAN, C/C++, Java, HTML, Ruby, and I've dabbled in weird stuff like brainfuck.

So far I think I'll be needing a Pico-ITX MoBo, a DC transformer to power the motors at 24VDC, a DC generator, a PLC, and the sensors themselves.

Feedback, comments, and suggestions are greatly appreciated.
--Cotowar--

Offline krich

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Re: Getting started
« Reply #1 on: July 09, 2008, 11:32:25 AM »
Just some thoughts on your plan.  Take them or leave them as you see fit.

I want to build a self powering robot with 4 wheels, an actuating arm coming out the top, and enough power to be decently useful in everyday life. I was planning on controlling it with speech recognition, and I was thinking of adding various sensors as needed.


Robotic arms are quite complex and difficult to control precisely.  You might want to put that on the back burner for a while and just work on your robots movement and spatial awareness through the sensors.

I was planning on building out of steel, as I get a hella huge discount on all types of it, I have access to a wicked sweet TIG welder, and yea, I want a super duper strong frame.


Steel is very strong, but very heavy.  You might want to consider aluminum instead.  Take a look at Admin's tutorial pages on materials.

Programming doesn't scare me, as I am "fluent" in VB, FORTRAN, C/C++, Java, HTML, Ruby, and I've dabbled in weird stuff like brainfuck.


If you are going to use a general purpose computer, running Linux or Windows or whatever, you'll need to consider building or buying an I/O interface to run your sensors and motor controller.  What strengths gen purp computers bring in raw processing power and capacity, they generally lack in basic analog and digital I/O interfacing.


So far I think I'll be needing a Pico-ITX MoBo, a DC transformer to power the motors at 24VDC, a DC generator, a PLC, and the sensors themselves.

Feedback, comments, and suggestions are greatly appreciated.


If your robot is going to run untethered to a power outlet, you'd better be thinking batteries rather than transformers.  With a heavy steel chassis, you'll need some big motors, which will require lots of juice, so you'll need some big batteries.  The bigger and heavier your robot, the more flex and wobble you'll have throughout the whole structure, which translates into more difficult sensor reading and interpretation.

Good luck and keep us posted on your progress.

Offline CotowarTopic starter

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Re: Getting started
« Reply #2 on: July 09, 2008, 02:57:39 PM »
I know steel is heavy, but I was thinking of a 2' x 3' x 2' rectangular box shape, with a few ribs running the short way on the bottom side. I guess aluminum could work, but I don't know the specs or grades of it like I do with steel. My father works in a prototype shop, so I've been around metals (particularly brass, zinc, and steel), for most of my life, and am very comfortable working with such metals. Aluminum doesn't necessarily scare me, its just that I'm not very good with it, and don't know the full potential of the material. I'll probably look into it though, just to keep all my bases covered.

As for the robotic arm, I think I have that problem solved. Again, being around my father's shop, I was exposed to CNC machines, and other computer driven machinery from an early age, and am somewhat familiar with PLC, and real-time control. I'm no expert by any means, but I'm comfortable enough with it to understand the basics of how it functions. I was not planning on using motors for the entire device, but instead, using an inline linear actuator, hooked to a steel cable, threaded through an off center hole running the length of the arm. By doing this, you can effectively push and pull on the cable to get the desired arm movement, and it is very strong and very precise. I was planning on doing the same thing for the fingers on the hand as well, only to a smaller scale. I can upload a diagram if there is any confusion on this idea. I know that trying to explain it to my mother was rediculously hard, and most people can't picture what I'm talking about.

I was planning on using 24VDC servos for my wheels, but I don't yet know if i want two or four of them. I would imagine four would be better, as I would have more power in forward and reverse motion, and the same amount of control for turning, but I've not yet looked into these aspects. I'm actually still kind of designing this beast, and I'm flat broke as I'm just home for the summer from college, and have not yet found a job because we just moved.

I was looking into transformers because I can then hook a small battery (6V, 12V) or what have you, to the motors controlling the wheels. The motors I'm looking at are industrial grade, low profile, and very powerful. They do require a lot of juice, but thats totally fine with me.

As for the batteries themselves, I did find some 6V rechargeable ones on McMaster.com, and was planning to make some type of array, where one battery would power the transformer, one would power the electronics and DC generator, and two or four more would be charging. I planned on making my own casings for them so I could quickly replace them when they finally die. The only things I haven't looked into yet for this are how long it takes to discharge the batteries under load, and how long it takes to recharge them.

As for the computer, I was thinking of running a version of Linux on it, not exactly sure which one (probably Ubuntu 8.10), as I'll be putting it on my laptop when it finally comes out. For I/O interfaces, the PLC works wonderfully for that, allowing me to take input from many sensors, and program motor or actuator output accordingly. I figured I'd throw a nice mic and speaker on it too so I could make it talk to me, play music off my laptop, and take voice commands.

On the other hand, building an I/O interface would be a lot of fun, and would give me exactly what I need.


I hope I get a job soon so I can start saving up for parts and whanot. I'm probably going to start a website and upload pics of every step I take in this process, and just post the link every now and then so people can literally SEE what I'm doing.
--Cotowar--

 


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