[SOLVED] Motor[x].DesVelZero

[erikj]

Hi DT Support,

 

I noticed the following behavior wrt Motor[x].DesVelZero which disagrees with the PPMAC SW Reference manual (Power PMAC Status Data Structure Elements). The manual says:

 

The Motor[x].DesVelZero status bit is set to 1 if the motor is in closed-loop control and the commanded velocity is zero (i.e. it is trying to hold position). It is zero either if the motor is in closed-loop mode with non-zero commanded velocity, or if it is in open-loop mode (enabled or disabled). It is bit 14 of 32-bit element Motor[x].Status[0].

 

I am seeing that the value is 1 (true) if the servo loop is open. See the example below. First status is for the loop closed, second one is for loop open. You can see the closedLoop and ampEna flags change state, but the desVelZero flag remains the same.

 

Servo loop is closed at start:

Status: Motor[1].pos: -0.5

Status: Motor[1].vel: 0

Status: Motor[1].desVelZero: true

Status: Motor[1].closedLoop: true

Status: Motor[1].ampEna: true

Status: Motor[1].inPos: true

 

Opening the loop...

Status: Motor[1].pos: 1.07031

Status: Motor[1].vel: 0

Status: Motor[1].desVelZero: true

Status: Motor[1].closedLoop: false

Status: Motor[1].ampEna: false

Status: Motor[1].inPos: false

 

Is this behavior correct?

 

Thanks,

 

Erik

[bradp]

The documentation is wrong. The motor can be closed loop, open loop, or killed. When closed loop the bit will be 1 when the commanded motor velocity is zero even if the actual velocity is not zero. When open loop or killed it will be 1 when the actual velocity of the motor is zero. You can AND it with another bit such as Motor[].ClosedLoop if you want to distinguish that case.