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Is this spec of motor good enough to run a small robot with wheels of diameter 8cm at a speed of roughly 4m\s

MOTOR, STEPPER 18 DEGREE; Angle, indexing: 18°; Centres, fixing: 25mm; Diameter, external: 20mm; Length / Height, external: 17.2mm; Length, shaft: 6.2mm; Phases, number of: 4; Power consumption: 0.74W; Resistance, phase:

If not could someone please give me the correct spec. it's pretty urgent so I would really appreciate it. thanks!

MOTOR, STEPPER 18 DEGREE; Angle, indexing: 18°; Centres, fixing: 25mm; Diameter, external: 20mm; Length / Height, external: 17.2mm; Length, shaft: 6.2mm; Phases, number of: 4; Power consumption: 0.74W; Resistance, phase:

If not could someone please give me the correct spec. it's pretty urgent so I would really appreciate it. thanks!

http://ie.farnell.com/jsp/endecaSearch/searchPage2.jsp?Ntt=stepper+motor&Nty=1&N=401&Ntk=gensearch

The biggest weight is apt to be the batteries, so you also have to decide what you want for range and operating time

To give yourself some margin, require that your robot be able to climb some small incline angle ( A of 10 deg for example) at some velocity (v) .

Now you can calculate the climbing power the motor must deliver:

P = sin(A)* M* g* v with P in Watts M in kg v in m/s g=9.8 m/s^2

You have to go the motor data sheets to find Torque and angular velocity:

The formula shaft power is

P = omega * T with T in N*m omega in radians/s ==> omega = 120 * Pi * (v in RPM)

http://www.318ti.org/notebook/torque/

Let the total mass of the robot be 2 kg including 0.3 kg for a 6 volt, 1.3 AH lead acid battery which lists for $8.00

http://rocky.digikey.com/WebLib/Panasonic/Web%20data/LC-R061R3P.pdf

We require that the robot climb a 10 deg incline at 1 m/s. We can find the climbing power:

P = sin(10)* 2 kg*( 9.8 m/s^2) * ( 1 m/s)

= (0.173) * 2 * 9.8 * 1

= 3.4 watts ==> So the 0.74 W motor you mentioned in the question could not drive this robot.

The current drain from the battery at 3.4 watts is

I = P/V = 3.4/6 = 560 mA

From the battery data sheet (Duration of Discharge vs Discharge Currrent) you can see that the battery would be dead in 1 minute.

On the flat, it might last five times longer. You might decide on a bigger battery. Maybe you can cut down on the mass. Maybe 1 minute is enough.

You may have to go through several rounds of calculations like this to optimize robot performance for your specific requirements.

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Not quite sure that such tiny motor could reach that much speed ... nevertheless,

by my calculations you need about 16 turns per second on the wheels.. well including a transmission from the motor to the wheel which should be at least say 3:1 means you need at least 48 turns per second , which means about 2880 turns per minute, which is quite high. If you're using transmission 1:1 then 960 turns per minuta should be enough.

The steping of 18 degree can assure you 20 steps per revolution...which means that this is quite a quick step motor...

Well I think this is possible. But like said depends on the mass of the whole thing ... should probabyl use some reductor

and offcourse you have to watch out for the pulse frequency that you give that motor...

by my calculation you need like at least 20 kHz source - pulse frequency to drive this thing.

I think this is achievable. This should be working, but if it's to heavy you'll need a stronger motor, or use a reductor at higher source frequency (multiplied by the transmission coefficient)

I hope my thinking can help you out here.