Reference Manual

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PMAC 2 Software Reference

96 PMAC I-Variable Specifiation

Ix62 Motor x Current Loop Proportional Gain (Forward Path) {PMAC2 only}

Range

0.0 .. 1.0 (24-bit resolution)

Units

Output = 4 * Ix62 * (I

cmd

- I

act

)

Default

Remarks

Ix62 is the proportional gain term of the digital current loops that is in the “forward path”

of the loop, multiplying the difference between the commanded and actual current levels.

Either Ix62 or Ix76 (back path proportional gain) must be used to close the current loop.

Generally, only one of these proportional gain terms is used, although both can be. Ix62 is

only used if Ix82>0 to activate digital current loop execution.

Ix62 can provide more responsiveness to command changes from the position/velocity

loop servo, and therefore a higher current loop bandwidth, than Ix76. However, if the

command value is very noisy, which can be the case with a low-resolution position sensor,

using Ix76 instead can provide better filtering of the noise.

Ix62 is typically set using the current loop auto-tuner or interactive tuner in the PMAC

Executive Program. . Typical values of Ix62, when used, are around 0.5.

See Also

Setting Up PMAC Commutation

I-variables Ix61, Ix66, Ix76, Ix82

Ix63 Motor x Integration Limit

Range

-8,388,608 .. 8,388,607

Units

(Ix33/2

) counts * servo-cycles

Default

4,194,304

Remarks

Ix63 limits the magnitude of the integrated position error (the output of the integrator), which

can be useful for “anti-windup” protection. The default value of Ix63 provides essentially no

limitation. (The integral gain Ix33 controls how fast the error is integrated.)

A value of zero here forces a zero output of the integrator, effectively disabling the integration

function in the PID filter. This can be useful during periods when you are applying a constant

force and are expecting a steady-state position error. (In contrast, setting Ix33 to 0 prevents

further inputs to the integrator, but maintains the output.)

The Ix63 integration limit can also be used to create a fault condition for the motor. If Ix63 is

set to a negative number, then PMAC will also check as part of its following error safety

check whether the magnitude of integrated following error has saturated at the magnitude of

Ix63. With Ix63 negative, if the integrator has saturated, PMAC will trip (kill) the motor with

a following error fault. Both the normal fatal following error motor status bit and the

integrated following error status bit are set when this fault occurs. If Ix63 is 0 or positive, the

motor cannot trip on integrated following error fault.

To set Ix63 to a value such that the integrator saturates at the same point that its contribution

to the command output causes saturation at the Ix69 level, use the following formula:













∗

±=

30Ix08Ix

269Ix

63Ix

To cause trips, the magnitude of Ix63 must be set to less than this value due to other potential

contributions to the output. Remember that the integrator stops increasing when the output

saturates at Ix69.