### Author Topic: Help in my project  (Read 3253 times)

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#### andropoland

• Beginner
• Posts: 6
##### Help in my project
« on: August 17, 2009, 08:37:08 AM »
hello... im going to build a robot that can lift, push and pull an object.. the object is a customized box, wherein the robot can grab the object my problem is... i dont know how will i determine the maximum load / weight of the box to determine how strong the arms, and shoulders of the robot... is there a formula i can use to solve for the weight? so that i can determine how strong the robot must be...

#### Joker94

• Supreme Robot
• Posts: 1,119
##### Re: Help in my project
« Reply #1 on: August 17, 2009, 04:43:45 PM »
well without mathamatics there are two options.

1)Build your robot without fussing about the weight and modify the box you want to carry to go with the strenght of the bot

2)Ge the best parts you can afford and build the bot a strong as you cab make it.

keep us up to date and we'll figure something out.

#### dual

• Jr. Member
• Posts: 43
##### Re: Help in my project
« Reply #2 on: August 18, 2009, 11:32:18 AM »
I think the people in this forum are really nice.. in an AVR forum that I used to hang out, the people are very strict with beginners especially those who start out with questions such as these, akin to "help me start my project". Here you guys still help out the people regardless.

Anyway, here's what you need to figure out, the weight of the box, friction coefficient, and in which direction you want to move it.

If you want to push it for example, say the weight to be F1, friction force to be F2, you will need forward motors that can give a push force of greater than or equal to the friction force and hopefully has an upward force not to smaller than F1, if not greater.

If you want to lift it fo example, say the weight to be F1 and friction force to be F2, you will need a servo for the arm that can give a lift force greater than F1.

given that torque = lever arm * Force * sin(angle between force and lever arm)
So if say you know the weight to lift the box is F3, and the length of your arm is R1, then say for angle of 90 degrees then the torque of a servo that you need is F3*R1 and the servos that can be bought specify the amount of torque.

Hope that helps

#### andropoland

• Beginner
• Posts: 6
##### Re: Help in my project
« Reply #3 on: August 19, 2009, 09:02:07 AM »
for mr. dual

#### andropoland

• Beginner
• Posts: 6
##### Re: Help in my project
« Reply #4 on: August 19, 2009, 10:05:25 AM »
well without mathamatics there are two options.

1)Build your robot without fussing about the weight and modify the box you want to carry to go with the strenght of the bot

2)Ge the best parts you can afford and build the bot a strong as you cab make it.

keep us up to date and we'll figure something out.

heheh i'm greatful in that idea, but actually i cant use those two options  haha , eerr... this project was actually my design project, a final project before i graduate and hehe im really a beginner in the field of robotics and the only thing i can do is to program PIC but i still dont know how to program pic controlling the servo's angle.. i have to defend it in our defense 3 and a half months from now.. so i really have to undergo computations that will prove every ideas in this project thats why, i have no choice but to do some mathematics ehehe anyway sir, i am really grateful and will be in depth for helping me willingly to my project i'll keep u sir up to date in this forum...

I think the people in this forum are really nice.. in an AVR forum that I used to hang out, the people are very strict with beginners especially those who start out with questions such as these, akin to "help me start my project". Here you guys still help out the people regardless.

Anyway, here's what you need to figure out, the weight of the box, friction coefficient, and in which direction you want to move it.

If you want to push it for example, say the weight to be F1, friction force to be F2, you will need forward motors that can give a push force of greater than or equal to the friction force and hopefully has an upward force not to smaller than F1, if not greater.

If you want to lift it fo example, say the weight to be F1 and friction force to be F2, you will need a servo for the arm that can give a lift force greater than F1.

given that torque = lever arm * Force * sin(angle between force and lever arm)
So if say you know the weight to lift the box is F3, and the length of your arm is R1, then say for angle of 90 degrees then the torque of a servo that you need is F3*R1 and the servos that can be bought specify the amount of torque.

Hope that helps

ur ryt sir dual, people here are really nice for helping me  and giving me ideas such as wat u have mentioned sir, (im thankful) eer.. so given that the weight of the box is F1 and the force i need to lift the box is F3, do i have to determine the materials or components of my arm to determine the servo's power that will lift the box? and since this project is involve with lifting pushing and pulling.. is some formulas from strength of materials is required for this project?? i will be really grateful

#### dual

• Jr. Member
• Posts: 43
##### Re: Help in my project
« Reply #5 on: August 19, 2009, 11:46:29 AM »
andropoland: I have to apologize but this is where I say I'm not a mechanical engineer and that I'm actually a student in Computer Hardware Engineering.

I cannot help you with the field of Mechanics of Materials if you really have to go in-depth in your defense regarding computations.

However, though technically you do have to figure out the strength of the material you will be using, there are more cases where you can avoid them.
Here is a wiki on the Strength of Materials that has a lot of links to the formulas that may be of use to you.
http://en.wikipedia.org/wiki/Strength_of_materials

If you will be building a robot to be used for defense, can I assume that you will be building only a Robotic Arm?
If not, can you enlighten us with your proposed design so we can work on what stuff actually needs to be computed.

#### Joker94

• Supreme Robot
• Posts: 1,119
##### Re: Help in my project
« Reply #6 on: August 20, 2009, 05:44:23 AM »
think of it like this, look at the speck of the servo and it should have a torque rating. This theoretically is how much it will lift. There for take the weight specified and take the weight of the servo and arm materials and it will give you the amount of weight it will be able to lift.

Are you planing on using one or two servos to lift the box. And do you plan on using servos or motors for pushing and pulling

keep us updated !

#### andropoland

• Beginner
• Posts: 6
##### Re: Help in my project
« Reply #7 on: August 20, 2009, 10:03:48 AM »

http://i457.photobucket.com/albums/qq295/andropoland/Picture1.jpg
http://i457.photobucket.com/albums/qq295/andropoland/Picture2.jpg

this is the ideal and initial design of my design project sirs..

this is a bipedal unit mecha, it stands 2 and a half feet in height and has an external cockpit to control the mech eerr.. actually it can walk but since there are alot of references to a walking robot the idea was extended..
it's primary objective is to lift, push and pull a customized box wherein the maximum weight of the box is still unknown
when in push an pull mode.. the mech can change into wheels (well the idea is similar to code geass' lancelot and knightmare frames) for faster and easier way of pushing and pulling.. (since it will be too hard to push and pull the box while considering walking)
when in wheel mode the mech's walking feature will be disable or i can say in 0 state.. the project is actually a combination of a bipedal and robotic arm but the project is not totally a robot since the project can be controlled by a human.. you can say that this project is like a robo puppet similar to what we saw in anime like gundam and robotech

the problem are these;
> the materials weight and sizes.. how can i compute them?? should i use aluminum in the project for the exoskeleton??
> the servo motors power
> how can i program the servos angle?
> designing the circuit board??
> wat kind of PIC should i use and consider?

and other problems that i should consider ...

ehehehe  i need more ideas

#### mdmedlin

• Full Member
• Posts: 73
##### Re: Help in my project
« Reply #8 on: August 22, 2009, 01:18:09 AM »
Torque is rotational force.  It is how much force the servemotor can output in it's axis of rotation.  To calculate the torque you need, you need to know how much the arm and all the hardware weighs, the weight of the box and the weight of the contents of the box or the servo will not turn.  In so far as the push and pull, I guess you will need to also know the friction coefficient of the box and the surface it will be resting on.  If at all possible, make the bottom of the box out of teflon or use teflon tape LOL .  Ok now back to the box issue.  This customized box, who will be making it?  If you are going to be making, then I would figure out what the max load on the box is and use that.  Without more information I am not sure how much more I can help.
Do or do not, there is no try yes I changed my picture, it is of my daughter.

#### andropoland

• Beginner
• Posts: 6
##### Re: Help in my project
« Reply #9 on: August 22, 2009, 09:08:57 AM »
Torque is rotational force.  It is how much force the servemotor can output in it's axis of rotation.  To calculate the torque you need, you need to know how much the arm and all the hardware weighs, the weight of the box and the weight of the contents of the box or the servo will not turn.  In so far as the push and pull, I guess you will need to also know the friction coefficient of the box and the surface it will be resting on.  If at all possible, make the bottom of the box out of teflon or use teflon tape LOL .  Ok now back to the box issue.  This customized box, who will be making it?  If you are going to be making, then I would figure out what the max load on the box is and use that.  Without more information I am not sure how much more I can help.

hmmm... from wat u have mention sir, i think that is my main problem hehe  ... actually after designing the initial design of the project i suddenly thought the hardware weights. starting to build or construct the robot or mech from below( feet to body) i am even having a hard time thinking if the robot's feet to hips will be able to withstand the body's weight wherein in the body is the robot's arm and shoulders plus the other components inside the robot that will affect it's performance.
last time when  i go to a metal fabricator they asked me about the materials weight, diameter, length etc, etc before they shape and construct the metal i need of course i dont know those kind of things yet  since i still lack the data and information i need and that time the problem arouse hehhehe

actually if the only problem is programming it, i think there will be no problem (i hope?) since i'm a computer engineering student, the problem is that i have to solve problems that involve civil, mechanical and electrical engineering ( well,, electrical maybe i can do it...) in this project where im starting to bleed my nose... so.. maybe  i should think first all the hardware specification and from that.. how should i know those kind of thing??

ideas??  greatly appreciated thank u

#### wil.hamilton

• Robot Overlord
• Posts: 207
• rtfm
##### Re: Help in my project
« Reply #10 on: August 23, 2009, 09:28:31 AM »
if you don't know how much your box weighs then you're going to have difficulty building something that can move it.  i would first figure out how much the box weighs, and then you can figure out how much force you need to move it.

#### andropoland

• Beginner
• Posts: 6
##### Re: Help in my project
« Reply #11 on: September 14, 2009, 08:47:04 AM »
yey.. it takes me in a while to post in this forum..

hmm.. i've been busy this past few days for the completion of my documents for this design project
next month (in october) were now going to start the building of the project "MCU-Base Load Lifter Pusher and Puller Mecha" thats the project title hehe

so i read the information send me by mr. wil hamilton and yep it really help me alot (thanks master)
my new problem is this one... our design project aims to carry a load (customized box) with a maximum weight of  1kg.. yep buts its only initial.. if its too heavy were going to reduce it.. hehe the thing is.. is there a servo or stepper motor which can carry or i mean has a torque force that can carry a load that i have mention??
if so.. how will i look the specs of the motor if im going to buy it? how will i determine its rotational force or torque? and the last but not the least question...
heheh how will im going to control the motor's angle using PIC?? all my past project only involves PIC controlling LEDS to light but controlling the stepper/servo motor's angle is not yet sumthing i have done so far.. sow...masters on this forum will someone lend me a hand or help me, or provide me a nice childish tutorial site or a pdf file where i can learn it?

P.s i dont really want to shift to pneumatics for lifting purpose its too expensive and our wallet will surely bleed.. im going to pray now hehhehe

• Beginner
• Posts: 4