assisted transfer robot design help required please

[Cradboard]

Hi all,

i dont really know what to call this so if you can think of a better title do let me know and ill amend it! thats if you even understand my description!!

Essentially i am trying to make transfer device.  I have attached a rough 3D model to aid in my explanation! the gold components i already have, the car sits on these and allow me to work around it easily.  however to move the car i have to push it.  what i want to do is attach something (like the silver component)  to the trolley that will move the car via remote control or by just holding a button on it and walking with it.

from my research so far i want the following to be incorporated in my robotic arm

1) i want to be able to attach and detach the "robotic arm" simply and easily

2) the maximum force required to start the system moving is about 80kg, consequently the robotic arm must weigh more (this affects point 1 above) or must have a means of using the weight of the vehicle to increase the pressure it exerts on the floor, a sort of jack or expansion system such that the load is spread between all three points of contact evenly.  The bending moments will be high with a design like this however??

3) all components for powering, moving, braking and guiding it need to be housed in it, including power, i would like it rechargeable. A simple remote control system could be implemented to control forward and backward motion or a button on the arm itself.  

4) i wouldn't mind a means of sensing how far the wall is from the front, much like car parking sensors?feasible?

i think some DC motors would have sufficient torque, ones used in golf buggies and wheelchair units but thats as far as ive got techincally.

My knowledge is limited in most of the above areas lol and im struggling to find relevant literature to progress my ideas. any advice you can give me or literature you can recommend reading would be greatly appreciated.

 

[GWER57]

You basically first need to find a DC motor that is strong enough to move this device. Controlling it wouldn't be hard as all you would need is a heavy duty h-bridge, a button, and some wire for tethered control

For wireless control you would need a wireless transmitter and receiver, and two microcontrollers.

As for the battery i would reccomend rechargeable sealed lead acid.

And as for object avoidance all you would need is a sharp ir rangefinder connected to a comparator or a microcontroller. (Which is very feasable  )

To mount it i would use some sort of pipe clamp

[Cradboard]

sorry ive been away.
how do i calculate the required power etc? and what size battery is needed to provide enough charge?
i know weights, time, and distance?

[GWER57]

Just look for tutorials on this site or on the internet
 

[nottoooily]

Yea there's load of tutorials on that basic stuff.

Power output is a function of speed and force

Electric input power will vary a lot between startup and cruising - because speed, force and motor efficiency all change. Lots of approximations available depending on how precisely you want to predict battery life.

Batteries have specs on their maximum current output. P=IV. Lead acid can be pretty useless for heavy currents.

Battery capacity (Ahr rating) is the energy stored in it. Work out the energy used to moved it for the time you require, and make sure they match up after applying the efficiency factor.

For the mechanics, how about the leg having an axial spring so you kind of rotate it in against the floor? Then you don't have to use all your strength to compress the spring and still get plenty of spring force against the floor. Alternatively a toggle mechanism to lengthen the leg slightly but very powerfully.

Also, silver may not be the most cost effective material choice

[Cradboard]

for any of you that were interested in the project at all the latest progress is here

http://www.societyofrobots.com/robotforum/index.php?topic=10525.0