linear analog servo motor drive

[ammar86]

hello my friends
i am trying to build a linear analog servo drive for a servo motor and YES it is analog not a PWM for many reasons one of them :is that this drive is a part of control system i am working on and i want to reduce the noise to minimum.
so i dig the web and i found several power op amp: like L165,L2720, LM675,LM12
i am kid of confused because all i want is :
Class-AB linear power Amplifier with no distortion around zero
i am trying to use the power op-amp rather than power transistors to reduce the number of components and the issues related to them .
here is the motor specifications:

Motor Data sheet
i suppose to control the position in bi-direction.
the questions:
1-which power op-amp should i use?
2- is there a ready drive that i can buy ?
3-is this circuit correct to control the motor position in bi-direction?

any help will be more than appreciated

 

[itsmoked]

Can you even buy that AMP anymore?

Your circuit is 'generally' correct if your supply to the chip is bipolar and your DAC output is bipolar too. You'd want about a 0.01uF cap across the motor for noise suppression.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ammar86]

thanks for replay
can you suggest a better power op-amp 6v 2.5 amp
please

 

[mikekilroy]

you want linear drive to keep noise to minimum, yet you show a dc motor? so you have brushes that generate significant noise......

your drive will probably not work satisfactorily for you, as it is just a linear voltage amplifier; you probably want a summing junction in front of the amp input and sum - current from a current sense resistor is series with armature. then your dac command is command for current or force - which is linear. voltage into a motor armature is not linear with speed due to IR drop.

but what is "minimum?" do you realize folks supply ac drives and motors used in places today where in the past only linear amps would work? we do a lot of work with coordinate measurement machines; our linear motors and pwm drives allow accuracies well below 1 um and resolutions well below .01um. I think you might find a good linear motor and pwm drive designed and applied properly for your application would provide less noise than what you can build and use with a dc linear motor with brushes. just my opinion though.

 

[ammar86]

thanks mikekilroy for your great comment , the problem is that i cant change the motor because it is part of this system:

the only thing i can do is to build a driver for this motor , the company who built this system sell it's servo drive with a power supply for 2000$ which is too much for 3watt servo amplifier so i decided to build one . so the company (Quanser) use analog servo amplifier so i decided to build it as the company did.so PWM will be more efficient for this motor?

 

[mikekilroy]

you might email galilmc.com see if they still sell their small linear drive amplifier similar to what you want. it was an accessory for running very small motors rated around 40vdc 3 amp.

 

[blacksea]

You can check possibility to use Apex power op amp for bi-direction rotation of such DC motor as well - look in

http://www.apexanalog.com

 

[ammar86]

thanks a lot everyone