slow motor response - Electronic Circuits Projects Diagrams Free

ahmedragia21 · 11th March 2008, 01:29 PM

hi, im trying to follow a straight line and i found my motor has a slow response when i do PWM , i dont know why ? is this cuz the motor is a used one or what ? and how do i solve this problem ..

thanks !

NightFalcon90909 · 11th March 2008, 03:37 PM

It is probably just a matter of you using too little power or too small a motor for too heavy a robot. Anyway, that is what I would check first.

Papabravo · 11th March 2008, 04:38 PM

Basic priciples of motor drives

Code:

T = I * α

where T is torque, I is moment of Inertia, and α is angular acceleration
in radians/per second

T = Kt * i

where T is torque (again), Kt is a constant which is unique to each motor
and i is the current in the coil.

You can set the two expressions equal and solve for any one of the four quantities if you know the other three. Check on wikipedia for the moment of inertia for a cylindrical disc which is the easies thing to model that you can connect ot a motor shaft.

second286 · 16th March 2008, 10:39 PM

ahmedragia21:

Do a simple test, connect the motor directly to your voltage source-if the rpm/torque is still not good-replace the motor. But if it runs good then you know your problem is from either, insufficient power into the motor and/or you may need to adjust the PWM to match your motor electrical time constant.

Power in test:
compare the direct and PWM connected, motor RMS input currents?

PWM test:
You may do this by trial and error-varying your PWM freq/dutycycle for acceptable motor rpm/torque. Or simply place in series with your motor circuit a 2 to 3 ohm resistor (Rs)-then energize your system with a step voltage input (or a slow repeating squarewave)-view on a scope this transient voltage across Rs to get an estimate of your motor time constant. This voltage plot across Rs will be in proportion to the motor current, just larger in amplitude.

11th March 2008, 01:29 PM	(permalink)
ahmedragia21 Experienced Member	slow motor response hi, im trying to follow a straight line and i found my motor has a slow response when i do PWM , i dont know why ? is this cuz the motor is a used one or what ? and how do i solve this problem .. thanks !

11th March 2008, 03:37 PM	(permalink)
NightFalcon90909 New Member	It is probably just a matter of you using too little power or too small a motor for too heavy a robot. Anyway, that is what I would check first. __________________ If it is broken, let's fix it. If it is working, let's make it better.

11th March 2008, 04:38 PM	(permalink)
Papabravo Experienced Member	Basic priciples of motor drives Code: T = I * α where T is torque, I is moment of Inertia, and α is angular acceleration in radians/per second T = Kt * i where T is torque (again), Kt is a constant which is unique to each motor and i is the current in the coil. You can set the two expressions equal and solve for any one of the four quantities if you know the other three. Check on wikipedia for the moment of inertia for a cylindrical disc which is the easies thing to model that you can connect ot a motor shaft. __________________ We never have time to do it right; but we always have time to do it over.

16th March 2008, 10:39 PM	(permalink)
second286 New Member	Slow motor response: ahmedragia21: Do a simple test, connect the motor directly to your voltage source-if the rpm/torque is still not good-replace the motor. But if it runs good then you know your problem is from either, insufficient power into the motor and/or you may need to adjust the PWM to match your motor electrical time constant. Power in test: compare the direct and PWM connected, motor RMS input currents? PWM test: You may do this by trial and error-varying your PWM freq/dutycycle for acceptable motor rpm/torque. Or simply place in series with your motor circuit a 2 to 3 ohm resistor (Rs)-then energize your system with a step voltage input (or a slow repeating squarewave)-view on a scope this transient voltage across Rs to get an estimate of your motor time constant. This voltage plot across Rs will be in proportion to the motor current, just larger in amplitude.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Latest
slow response int on RB change	williB	Micro Controllers	9	23rd September 2006 06:39 AM
slow start dc motor	jack mcleod	Electronic Projects Design/Ideas/Reviews	15	27th September 2005 11:11 PM
stepper too slow !!!	dreamproject	Electronic Projects Design/Ideas/Reviews	15	9th November 2004 07:10 PM
TV slow to come on	Ken B	Electronic Projects Design/Ideas/Reviews	3	14th July 2004 09:40 PM
how to slow a motor	turbotec	Electronic Projects Design/Ideas/Reviews	6	27th February 2004 02:37 AM