MCT8316A: Why does the speed response is different depending on the speed input command?

Kenji

Part Number: MCT8316A

Hi Team

Why speed response is different depending on the speed input command?
Below is the speed response when switching from 10% to 90% of speed (step input) and from 10% to 90% speed using the same PID parameters.

I want to use PWM duty mode for speed input.
How can I improve the response of PWM duty mode?
I want to do the same as I2C speed input response.

I2C mode:

PWM duty mode:

This is too slow. I want to the same speed response, like I2C speed input.
Does it take time to recognize the speed?　Are you using any filters, is it possible to change the order?

My environment:

MCT8316AEVM (PMCT8316A)
MCT8316A_GUI ver1.0.0

over 3 years ago

0 Vishnu Balaraj over 3 years ago

TI__Mastermind 24415 points

Kenji,

The speed ramp up/down profile will be same in I2C and PWM mode. Only difference that I can think of is the rate at which you change the PWM duty cycle. If this rate of change is slower, then the speed response will also be slower. Can you try increasing this rate?

Regards,

Vishnu

0 Kenji over 3 years ago in reply to Vishnu Balaraj

Intellectual 530 points

Hi Vishnu Balaraj

This is the result of changing the PWM frequency.
There is no difference depending on the frequency.

Speed response is too slow than I2C and analog speed input.

Result1:

[ANA_PWM_SPD_SET] = PWM mode speed input
Acc: step input, duty 10% to 90%
Dec: step input, duty 90% to 10 %

Result2:

Question:

I suppose, that using some kind of LPF filter for PWM speed input, in fact.
To input to the ADC, like below red figure.
Is it possible to change the characteristics of the filter?

0 Vishnu Balaraj over 3 years ago in reply to Kenji

TI__Mastermind 24415 points

Speed response is slow in pre-production devices. We have fixed this issue in production devices. Can you switch to production device and try again?

Regards,

Vishnu

0 Kenji over 3 years ago in reply to Vishnu Balaraj

Intellectual 530 points

Hi Vishnu Balaraj -san

I'm already trying to order at the TI store.
But, as you know, it is difficult to obtain parts now.

Could you show me the step response waveform of speed, in production device.
I want to know how it improved.
I want to see the response speed when the speed changes from 2.5krpm to 22.5krpm.

+1 Vishnu Balaraj over 3 years ago in reply to Kenji

TI__Mastermind 24415 points

Kenji,

Attached are the speed response (10% to 100% and 100% to 10% duty cycle) in I2C and PWM mode in production device. We do not see any difference in acceleration and deceleration timing in both modes.