Closed Loop Control Of a DC motor

[azamuk]

Hi , Please Help

here the circuit diagram of my speed controller i need to conect it with the PID Controller that i have already made.

Please tell me the connections to connect it thanks...

 

[Grossel]

What you haqve there is a PMW generator. You control it by regulate P1.

If you want to use an external controller source, you must detatch P1, R1 and R2 and just feed voltage into positive input at IC1A. But first you have to calculate the minimum and max voltage to input.

Assuming you also have a tachometer on the motor shaft, next thing is to assemble it and run it.

 

[azamuk]

Thankz Grossel

yea i have a techometer

so the output from the techometer (frequency to voltage converter) will go into the input of the PID controller and the out put from PID controller to the Pin 3.

the motor is at 24V and 30Amps.

 

[Ubergeek63]

Thankz Grossel

yea i have a techometer

so the output from the techometer (frequency to voltage converter) will go into the input of the PID controller and the out put from PID controller to the Pin 3.

the motor is at 24V and 30Amps.

do you need it to be bidirectional?

if you do not need accuracy you do not need a tach... diode or the two sides of the motor together and filter out the HF component - DC motor speed is proportional to motor voltage

we use simple PWM ICs to control 100V 30A motors here... simple summing function - for a 1V summing junction you take

((0 to 5V control)/5 + (IR compensation for your motor) - (motor voltage)/24 = 1V

IR compensation is probably 20-30%. for instance our 100V 30A motors are mostly around 1 ohm armatures, so at full current they drop 30V on the resistance leaving 70V for the ideal armature... for 10% of full speed at full torque this means we need to supply 40V instead of 10V

many applications would not even need a PID loop ... BTW switching all 4 FETs every cycle is very wasteful, you should only be switching one side at a time.

dan

 

[azamuk]

Hi
Thankz for your advice my motor is in one direction.

I have also designed a PID but dont knw wat values to use it to control the closed loop speed. ny help with that please

 

[azamuk]

ALso i have designed a PWM but its onli suplying abt 10V if its on the ful.

I need abt 24 volts i m using the resistor walues as 8.2k and 10k. if i change the resistor values will i get more more output from the PWM.

 

[Ubergeek63]

R1 ,R2 & P1 determine your PWM ... delete half the bridge and ground that side of the motor

what is your PID loop in? the over complicated circuit is to prevent the transistors from being on at the same time and i think (with out doing any calculations) is why you are having trouble. if a micro you are better off using its PWM directly and external delays (if it is not a real motor chip that has non overlapping PWM outputs) to prevent the transistors from being on at the same time... or simply put a fast diode across the motor with a single FET