The question for How can calculate Motor[x].Servo.NominalGain

Hi,

My system environment is not suitable for executing Position loop Auto-tune of PowerPMAC IDE.

So, I'd rather to know equation of calculating Motor[x].Servo.NominalGain value but it is not mentioned anywhere.

(PowerPMAC Users manual, Software reference manual, PowerPMAC forum threads)

It is mentioned as "the value for Motor[x].Servo.NominalGain can be determined analytically" at PowerPMAC Software reference manual 521page(Motor[x].Servo.NominalGain part).

Could Somebody let me know the equation?

Thank you.

Analytically, it is best to think of this in terms of the detailed block diagram transfer functions, evaluating the gains of each step.

For example, if you have a +/-10V analog output to a current mode amplifier that commands +/-30A over the full command range, driving a motor with a torque constant of 0.5 N-m/A, with an effective total inertia of 5 kg-m^2, with 360 motor units defined per revolution, you would have the following gains:

Kdac = 10V / 32768 LSBs

Kamp = 3A / V

Kt = 0.5 N-m / A = 0.5 [kg-m^2/s^2] / A

Kmech = 1/J = 0.2 (1 / [kg-m^2])

Kenc = 360 motor units / (2*Pi)

The total gain is just the product of all of these individual gain terms.

Hi,

 

My system environment is not suitable for executing Position loop Auto-tune of PowerPMAC IDE.

 

So, I'd rather to know equation of calculating Motor[x].Servo.NominalGain value but it is not mentioned anywhere.

(PowerPMAC Users manual, Software reference manual, PowerPMAC forum threads)

 

It is mentioned as "the value for Motor[x].Servo.NominalGain can be determined analytically" at PowerPMAC Software reference manual 521page(Motor[x].Servo.NominalGain part).

 

Could Somebody let me know the equation?

 

Thank you.

The units are Acceleration in motor units per single bit of dac.

10 Volts/32768 * Amplifier tranconductance in Amp/Volt * Motor Force/Amp *1/Stage Mass

A = F/M

Gearing and ballscrew efficiency tend to muddy things a bit. I typically write a plc to output some small dac voltage per a time unit, capturing the velocity at the end of the time. A=V/T and scale this down to a single bit of DAC. repetition and averaging improve the results.

Dear, curtwilson and JeffLowe,

With your help, I can solve the question probably.

Thank you for your kind explanation.