SERVOs

hi everybody !
I want to use Servos in my project but i don't know what kind of servos to use, how much torque the servo should be and the cost of the servos.
thanks for help!

Are you talking about "real" servos?
http://www.teknic.com/model-info/CPM-MCPV-3421S-RLN/

Big steppers are easier to drive and way cheaper, another option.
Plus only 2 wires needed to drive them, and an Ard , no expensive card needed either.
Has been done.

yes i talking about real servos.

what do you mean Big stepper?

I thought about servos and if it will be expensive I will find some viper motors and build/buy Hbridge and connect it to my arduino.
I already built a small concept with small servos that works and because of that i want to find a big servos for the full scale project.

A stepper would have to be "big" enough to never loose a step due to lack of power or overshooting or, to my understanding, it will loose its position and have to be reset.

This is not an issue when you consider the power (Torque) of a stepper against the torque of DC motor, for size the stepper wins.

The unit I helped design used a ball screw attached to the stepper so the power needed was actually quite small 4nm to drive the ballscrew so loosing step was never an issue, since the stepper had a massive 50NM of holding torque, plus ballscrew used had a non backlash nut meaning with no power on the nut can not be rotated as in the machine stayed still while motors were not moving.
Ok setting up, calibrating was all done via limits switches, so driving the stepper cw until it triggered the lower limit switch to find its 0 position, when found reset the step count then drove ccw , counting the steps till the upper limit was reached and then maped those two figures to a 16 bit value and then it set its home position being centre. A true 16 bit movement , very nice resolution once we sent game movement to it.

All this is very simple to do in Ard IDE.
Works very nicely, sorry no pictures or videos as this was a commercial development I was paid to build.
But doesn't stop myself from sharing the theory with all, part of the agreement of me helping out.

The unit lifted 150kg sitting on top it , without losing any steps for a period of 1 hr running up/down at its fastest speeds - 700mm/s. So steppers used in the right way are piece of piss to use on a sim.
BTW it was a 48v - 5 amp unit with 50NM holding torque. - cost $70 on ebay complete with driver. Could have been used in the same way as a DC motor.

Can you tell me what is the model of this step motor? so i can to find it on ebay ?

Sorry that his private details, you are looking for a 1.8deg step, with high torque holding specs, NEMA
are used a lot in DIY CNC equipment , Hint !!

=) thanks, 1.8 deg step , 50 NM enough ?

Thanks for sharing what you can @eaorobbie ! Sounds like it may be viable but I haven’t researched steppers myself and don’t know much about them. I did look on ebay in the USA though and the best I could find was 30nm maximum at around $1000 for three of them with drivers. So it may be difficult for everyone to obtain the steppers required and at a reasonable price. This would likely still be less expensive than using industrial grade servos though!

http://www.teknic.com/model-info/CPM-MCPV-3421S-RLN/

These bldc servo motors with integrated drive and motion controller are often used to replace the weak stepper motors... go to the main page of teknic and watch the videos...

A stepper motor in conjunction with the right type of ballscrew you don't need 50NM looking at the range out there you will notice a very small turning torque is require to operate them, the pro on using steppers once set correctly they very accrutate and no feedback apart from 2 limit switches needed and are about 1/2 the price of the teknic motor which looking at them will require a right angle box on them or will need to fashioned in a build with the same sense.

I like to keep an open mind on what's available and what works too. More options the merrier.

So we have a lot of options but i need to do some physics calculations of my model to calculate the right torque and buy the rightest motor because of safety issue and finance.
Although i studying Electrical Engineering it very difficult to me to calculate the torque i need.

All depends on the mechanics of the sim, ie the end weight being needed to move and how long a lever if no levers how much torque is require to turn something. Need to look at the overall picture. or over build it and pay a lot extra for what you didn't need. When stepping up past 12/24v rigs there is a lot more to consider but the limit is the budget too.

I think to build simulator with 2dof platform, something like this:

for this concept i need to calculate the physics.

Ok that concept does work better with 3phase AC motors, they just used slow motors.
Spent some time on several of theses ,their profile was lousy and reaction lag in race was nearly unplayable but running their software.
Can all be built around the 3k mark and recently proven here on site can be controlled using @RufusDufus code with a simple Ard. Check the post out , Well done @hooshang - http://www.xsimulator.net/community...and-windows-utilities.4957/page-13#post-57897

Take a look think his got the answers you require.

No I dont want to use a 3phase AC motors. i want to use only the moving platform and use some servos or step motors. Because of that i need to understand what torque i need in that kind of platform.

@Sergey Komarevtzev , you need to come up with a design then. You need to consider how much movement you want, the size of the frame, what you intend to sit on it - weight wise.
Once you have an estimation of all that, then you can look at what sort of power you need.
12v boat winch motors and JRKS would lift it, but again, depends what sort of weight you want to carry on it.