Electric WheelChair project Help ! Urgent

[andrwo2]

Hello guys ,

I'm doing a solar panel powered electric wheelchair ,

I Will have a weight of total 100 kg (  person + motors + wheels + batteries + panel )

I will use 2 identical motors to power the 2  back wheels of  20 cm of diameter  each

I need you to help me to know the specifications  of the motor i should buy  , ( torque , power , rpm )

I have no idea to relate the weight to the torque and power i need !!  knowing that the ideal speed of an electric wheelchair  is  3 to  5  mph 

Waiting for your help   , thank you guys

[newInRobotics]

Hi there,

knowing that the ideal speed of an electric wheelchair  is  3 to  5  mph

1. If You use wheels with diameter of 20 cm, then circumference of the wheel = ~62.8 cm
2. Required speed is 5m/h, which equals to 13411.2 cm/min
2. All of the above gives us that motor RPM should be 13411.2/62.8 = ~213.6 RPM

I need you to help me to know the specifications  of the motor i should buy  [...]

If max weight carried is equal to 100kg and wheel radius is 10cm then torque required must be no less than 100/10 = 10 kg-cm. Two motors must be able to deliver at least half of that torque at 213.6 RPM in order to meet requirements.

What voltage are You planning to use to drive motors?

[andrwo2]

12 or 24 volt

[newInRobotics]

12 or 24 volt

So which one? 12V or 24V? 

[andrwo2]

it depends on which i find in market but i want 12 V !  but  can i ask a question !

what formulas did you use to calculate the torque  ?

F = m * a  ( a ? is this the acceleration of gravity 9.8 or the acceleration i use to reach the max speed )
 
T of one motor  = F/2 * R (   R = 10 cm )

is that right ?

V =  pi * diamter * w ( in rps )  (  * 60 ) to get it in RPM ?

[andrwo2]

through my formulas :  F = 100 * 1.5 =  150 N

Torque ( per wheel ) =  150 /2   * 0.1 = 7.5 N.M   WHICH IS EQUAL   76  Kg. cm   

is that wrong ? and why ?

[newInRobotics]

My first post in this thread outlines formulas used quite well 

torqueToMoveVehicle = vehicleWeight / wheelRadius;

circumference  = radius * pi;

rpm = desiredSpeed / circumference;

[andrwo2]

so i shall not use these equations ?
http://www.societyofrobots.com/mechanics_dynamics.shtml

im really confused and i can't get the exact information 

sorry

[newInRobotics]

so i shall not use these equations ?
http://www.societyofrobots.com/mechanics_dynamics.shtml

im really confused and i can't get the exact information 

sorry

These equations use You shall

Desired values one must know if equation result correct must be 

What is desired acceleration (in how many seconds do You want Your vehicle to reach 5mph)?

Example: If You want 5mph to be reached in 3 seconds, then desired acceleration is 5mph/3 = ~2.45ft/s^2 = ~0.75m/s^2;
Now, force required to achieve that (on flat ground) = 100kg * 0.75m/s^2 = 75N (Newtons);
Torque required (leaving friction out) to achieve the goal = 75N * 10cm = 750N-cm = ~76.5kgf-cm

Before You did not specify what acceleration You need, hence 10kgf-cm is overall torque required to move object from the spot.

[Soeren]

Hi,

I'm doing a solar panel powered electric wheelchair ,

I Will have a weight of total 100 kg (  person + motors + wheels + batteries + panel )

Did you consider just how little power you can get from even the largest panels you can fit?
You might wanna use a battery and let the panels add however much (or little) they can.