Analog PID control for DC motor position

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jivega

Joined: 26 Oct 2001
Posts: 35
Location: South-America

08 Oct 2003 21:40 analog pid controller

Hi.
I need a design example for Analog PID control for DC motor position
Thnks

ash

Joined: 25 Dec 2002
Posts: 160
Location: Europe

08 Oct 2003 21:47 analog pid circuit

lm12 is 80watt op-amp. it's suitable for analog motion controllers. There's a diagram of analog pid controller "modern control systems". You can design pid contoller with only 3 op-amps. For motion control applications you need frequency to voltage converter. You should convert tachometer signals to linear signal.

aslm

Joined: 03 May 2002
Posts: 125
Helped: 5

09 Oct 2003 10:45 analog pid

There is a lab not that gives a great introduction to this problem. With schematics and explanation of how to build an position controller for DC motors with op-amps.

Se a post in the e-book forum.
http://www.elektroda.pl/eboard/viewtopic.php?t=58753

regards Me

StoppTidigare

Joined: 16 Jul 2002
Posts: 156
Helped: 1
Location: Northern earth

11 Oct 2003 13:36 analog pid control

Hi the path you gave doesn't exist !
Do you have another link ?
regards,
/StoppTidigare

aslm

Joined: 03 May 2002
Posts: 125
Helped: 5

11 Oct 2003 22:46 dc motor position control

I did get the file from a friend and I found it great and useful so I uploaded it to the e-books section of the site. Now it seams like that section is gone Sad

(was a great resource)

I also noticed that the same document was out on the internet with another filename, but I can not find back to that place then the link was a reply to my post in e-book section and google gives nothing... So if anyone find it somewhere else, pleas give the link again, until then the file is attache to this post.

The file is a 12p labnoat about an analog PID position controller for a DC motor. It explains the P, I and D part of it and has a chematics.

regards Me

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aslm

Joined: 03 May 2002
Posts: 125
Helped: 5

14 Oct 2003 11:32 dc motor control pid

Found it outside elektroda, finaly...

http://www.people.fas.harvard.edu/~thayes/phys123/lb11PID_oct02.pdf

regards Me

7rots51

Joined: 17 May 2002
Posts: 1427
Helped: 14

14 Oct 2003 20:05 pid circuit

Hi
see yhis site:

hxxp://www.anadigm.com

An(at)digm brings platform-based design to the analog world with prequalified software and hardware components that allow complex analog circuits to be implemented in an analog equivalent to the FPGA.

You can use thier chips and build a PID controller (analog) they have appnote on this subject.

Regards

yangxh

Joined: 26 Nov 2004
Posts: 99

14 Mar 2005 1:32 motor position control

Hi
How can I design the cercuit using ICs as really PID controller?

shak

Joined: 29 Jul 2006
Posts: 5

15 Nov 2006 21:07 pid controller op amp

see
www.people.fas.harvard.edu/~thayes/phys123/lb11PID_oct02.pdf

Added after 2 minutes:

see
www.people.fas.harvard.edu/~thayes/phys123/lb11PID_oct02.pdf

egeorgiev

Joined: 12 Jun 2001
Posts: 44
Helped: 1

17 Nov 2006 13:25 analog pid control

Tried to "see www.people.fas.harvard.edu/~thayes/phys123/lb11PID_oct02.pdf", but it says:
Forbidden
You don't have permission to access /~thayes/phys123/lb11PID_oct02.pdf on this server.
So maybe you'll show it to us.
Regards

mostrengo

Joined: 27 Mar 2002
Posts: 126
Location: LSA

19 Nov 2006 20:44 analog pid circuits

see Lab 10c in http://www.people.fas.harvard.edu/~thayes/phys123/

... small sample

most

saqer

Joined: 15 Jul 2006
Posts: 5

20 Nov 2006 23:40 analog pid controller circuit

Hi
see this documentation, used the matlab simulink .
thanks

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oudghiri_m

Joined: 02 Dec 2006
Posts: 3

03 Dec 2006 10:37 pid analog circuit

see this site http://vet.hevs.ch/energie/techniquepid.asp

eehero

Joined: 23 Nov 2005
Posts: 232
Helped: 9
Location: Libya

04 Dec 2006 21:54 analog pi controller

you can use ATMEL AVR, it will help you in the way but i dont have more deatils about the problem
sorry

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04 Dec 2006 21:54 Ads

barfi

Joined: 11 Dec 2006
Posts: 40
Location: tehran

22 Dec 2006 18:36 analog pid controller design

i hope this would be useful!

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Shani

Joined: 26 Jul 2006
Posts: 67
Helped: 3
Location: Karachi, Pakistan

26 Dec 2006 17:07 analog dc motor positioning

Assalamo Allykum !

If you want to control the position of the DC motor then you must know some parameters of the DC Motor.

1) Open loop gain
2) Time constant OR Setteling Time (tau)

The moel in a model is represented by the

Km
_________
1 + TS

Then you must see its respose on the MATLAB.

Then there are the requiremenyts on that bases you design your PI controller.

I think that PI controller is enough for the position moor control.

"The Dish positioning Ssytem Using Geared Dc Motor" was my final practical in Control Engineering-II.

You design your PI controller for your requirement.

Wish you a good luck

Keep remember me in your prayers.

aiman_cia

Joined: 13 Mar 2008
Posts: 2

13 Mar 2008 20:44 analog pid controller design+opamp

i got problem with pid controller
please help me to design the analog pid controller for position control

umery2k75

Joined: 19 Apr 2006
Posts: 378
Helped: 24
Location: Pakistan

13 Mar 2008 22:27 pid position motor

Making the analog PID circuit, isn't difficult.It's just a piece of cake.You can make the general PID circuit in which Kp,Ki and Kd gains can be set by potentiometer.What more important is where your system gets stable.How will you find the gains for proprotional,intergral and derivative controller?What more important is, as how will PID circuit gets the feedback signal.Will you use some sensor? Calibration of sensor is also important in PID circuit, especially with Reference signal for PID controller.

dolpre

Joined: 18 Jan 2008
Posts: 103
Helped: 36

23 Mar 2008 10:24 motor damping constant

hey, i need help in determine the physical parameters such as damping ratio(b), moment inertia of rotor(J), electromotive force constant (Km), electric resistance (R) and electric inductance (L) of an actual motor.

this parameters is what mentioned in ee562bkkosh.rar.

umery2k75

Joined: 19 Apr 2006
Posts: 378
Helped: 24
Location: Pakistan

23 Mar 2008 11:14 pid motor position

Rougly speaking on this one.You need to have two potentiometers for this.One rotary potentiometer, which will be attach to your motor.The other potentiometer is the one by which you control it's angle.
How this will work

You change resistance of potentiometer(control angle), for example you set it to 100Ohms, then the motor will also move in order to set 100Ohms of rotary potentiometer.

So resistance of two potentiometer will always try to be the same.
100Ohms-----100Ohms

68Ohms------68Ohms

The resistance actually reflects the angle in position control.I assume you are talking about angular position control of DC motor.

So what will your PI controller would do.Your PI controller would try to keep the two resistance equals to each other.It keeps on moving the motor right in accroding with your potentiometer control angle.

If you need more help on it.I can help you make a circuit of DC motor position controller from scratch.

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

23 Mar 2008 11:55 pi dc motor control

The parameters are often given in motor datasheets or they can be extrapolated from performance graphs of general purpose motors.
e.g. as given byhttp://www.johnsonmotor.com

Rotor inertia isn't always given, but here the total inertia including the load must be inserted in calculation. It could be calculated from construction data or measured from a spin-up experiment. A mechanical damping can be neglected in most cases, I think, but could be estimated from spin-down time with open circuit motor.

oudghiri_m

Joined: 02 Dec 2006
Posts: 3

23 Mar 2008 13:46 op amp pid controller

Here u can find en interesting document for DC Motor

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dolpre

Joined: 18 Jan 2008
Posts: 103
Helped: 36

23 Mar 2008 19:43 dc motor position control potentiometer feedback

Hi FvM,

i am using S9D150-24CH from SPG motor.
The datasheet of the motor is as following website:
http://www.spg.co.kr/en/product/product_standarddc_st_6.asp

so, may i know how can i get the parameters which i need from the datasheet?
i need to know the back emf constant of the motor as well. So, how to get it experimentally? Or there is another way to get it from datasheet?

on the other hand, how am i going to estimate the mechanical damping from spin-down time with open circuit motor?
(i had get the ON/OFF by injecting step input to get the step response of the motor)

Thanks...

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

23 Mar 2008 20:51 how to convert pid to analog controller

You can estimate R,K and b from the motor data using some simplifications. Assume that the motors no load current would be actually 2 A and is caused by friction losses proportional to rotational speed that are identical to mechanical damping of the system. Then you get a true unloaded speed of 3117 rpm or 326 rad/s and a Ke of 0.074 Vs/rad = Kt 0.074 Nm/A (Kt estimation from T-N characteristics would be slightly higher at about 0.09).

Friction losses at 3000 rpm are 2 • 0.074 = 0.15 Nm or 0.15/314 = 0.47e-3 Nms damping constant. R estimated from the given operational points is 0.47 ohms. You can use an electrical measurement instead.

Motor L could be estimated from current rise time of blocked motor or with an impedance meter.

Inertia could be estimated from dynamical measurement, e. g. rotational speed or current response to voltage step when motor L is already known or rotational speed response to current step without motor L. Also resonance frequency with a torsion spring would allow an accurate measurement.

dolpre

Joined: 18 Jan 2008
Posts: 103
Helped: 36

04 Apr 2008 17:48 control position motor use pid

Hi FvM,

Quote:

Assume that the motors no load current would be actually 2 A and is caused by friction losses proportional to rotational speed that are identical to mechanical damping of the system. Then you get a true unloaded speed of 3117 rpm or 326 rad/s and a Ke of 0.074 Vs/rad = Kt 0.074 Nm/A (Kt estimation from T-N characteristics would be slightly higher at about 0.09).

1. How can i get the true unloaded speed of 3117rpm? As what i get from the datasheet is 3000rpm.
2. What did you mean by Ke= Kt 0.074 Nm/A? Is it means that Ke=Kt=0.074 Nm/A?
3. For the friction losses at 3000rpm, u mentioned that 0.15/314=0.47e-3 Nms damping constant. May i know where the 314 come from?
4. U mentioned that R estimated from the given operational points is 0.47 ohms. Can you explain more about this?

Hope you can help me...
Thank you very very much...

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

04 Apr 2008 18:07 dc motor pid control

1. I simply constructed a "true unloaded speed" in "speed versus load current" diagram by extrapolating up to I=0. This is motivated by my assumption about nature of losses respectively idle current.
2. Yes, Ke=Kt=0.074 Nm/A
3. 314 is 3000 rpm expressed as rad/s
4. The resistance is calculated from Ke and and speed drop versus load current.

dolpre

Joined: 18 Jan 2008
Posts: 103
Helped: 36

04 Apr 2008 19:26 analog pid with operational amplifier

Hi Fvm,

Really thank you very very much...
And i found one website which explain about this as well.
http://inst.eecs.berkeley.edu/~ee128/fa04/labs/lab7-motor.pdf

Very Happy

Added after 1 hours 7 minutes:

What i found from experimentally value of Kt is 0.076 Nm/A and it is just slightly higher than calculation from datasheet, i.e. 0.066Nm/A.

How if the motor is with a gearhead, will the value of parameters (Kt,Ke) change?

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

04 Apr 2008 21:00 analog position control

I think the correspondence of parameter from different calculation methods is exactly enough, to allow e. g. design of a controller.

With a gear, the sizes observed at the reduced shaft have to be scaled with the reduction ratio, either divided (speed) or multiplied (torque). Ke = Kt related to the reduced shaft would also be scaled. But I think it's useful or common, to do this. One would calculate the sizes for the motor shaft and scale the derived values. Another point is, that a gear increases the mechanical damping.

dolpre

Joined: 18 Jan 2008
Posts: 103
Helped: 36

05 Apr 2008 14:29 analog pid design

Hi FvM,

i understand that with a gear, the speed will reduce while the torque will increase.
May i know what is the relationship between a gear ratio, N with torque and speed?
In my case, i found that speed_gear = speed/N but the torque_gear != torque*N.

Quote:

Ke = Kt related to the reduced shaft would also be scaled.

may i know how to scaled it? Is it just multiply or divide it by N?

How if i found the transfer function of the motor without gear, is Kt/(tau*s+1) and want to convert it to the transfer function of motor with gear ratio of N?

Thanks in advance...

FvM

Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany

05 Apr 2008 14:56 analog pid controller

For an ideal gear, Ke and Kt would be multiplied with N. If you observe a torque below the theoretical value, it could be due to gear efficiency below 1, I would expect 60 to 90 % depending on gear ratio.