I'm trying to develop a robot control system made up of two parallel control loops.
The first control loop should control the robot position: it should acquire encoder position from a counter/timer board (PXI 6602), execute a control law and output the calculated torque reference, as a voltage level, (using a PXI 6711) towards the motor servocontrollers. This control loop should run at a frequency that can be selected in the range 5-50 Hz.
The second loop, at higher frequency (100-200 Hz), should acquire strain gauge signals (using a PXI 6070E) and generate, with a specified control law, a second torque reference. This reference signal have to be added to the previous one.
I see, from many examples, that a good strategy to have a con
trol loop with a deterministic timing is "anchoring loop time to hardware clock" using AI single scan and AO single update (having also a synchronized I/O operation).
Now my question is: which is the best way to develop a deterministic control loop, like the previous one, when no AI single scan have to be used?
In fact, in the slower loop I haven't an analogue input reading, instead I have to read a counter but I haven't found any example discussing the problem of timing deterministic control loops in which only counter reading and output operations are present.
Thank you for your help.
Regards.
Luca Bascetta
