Acceleration control for Steppers

[Raghu]

stepper motor acceleration 555

I am using a 2.75Nm rated ( Pull out torque ) bipolar stepper motor. This has a winding resistance of 2.3 Ohms per phase; Rated current of 2 Amps / Phase. and Inductance of 14mH/Phase.

I am using the L297 + L298 combination driver as a bipolar chopper for driving the motor in full step mode. The supply is at 12V / 10 A rating.

I am unable to achieve the quoted torque if I increase the clock frequency beyond 500Hz and the motor just stalls. ( the motor data sheet shows the torque drooping only after 1000 Steps/ sec) . The load is just frictional and not inertial.

I currently use a clock source that can be varied between 100 to 1500 Hz but not ramping it . I am told that if I apply the clock with a ramp from 0 Hz to 1000 Hz in a time of say 0.5 Sec, then the stepper will support 2.75 NM at 1000 Hz.

Kinldy advise if my information on ramping the frequency is correct.

( If so I can then use the 555 clock source as a VCO and ramp the frequency )

Thanks.

Raghunathan

 

[lollobrigido]

I think you are ramping too fast, however it depends mainly from the mass to move!
For the best performance use full step or better, microstep driving mode.
You need more voltage to support high step rate (I drive my motors with 24 V or more) to achieve the needed current.

Good look
Lollo

 

[H_u_n_t_e_r]

you powersupply should be 40V for more torq-speed efficiency...Voltage very important...Current will be very high at low speed (exceed your l298 max current) so you should use current limiting feature(l298-297)

But current will be low (app 0.5-1 A) at high speed.....
SUPPLY VOLTAGE VERY IMPORTANT IN RAMP APPLICATION!!!!!!!!!!

Also Half speed operation more stable than full step.