Question:
How is the status display 'CDATA-X0' to be interpreted?
Answer:
The status signal CDATA-XO (output at the function block CDATA) represents the zero crossing of the profile clock pulse on the x axis.
The x axis of the profile/motion profile shows the phase or position characteristic in the range from 0 to the end of the clock pulse.
Standard profile clock pulses in rotating systems are e.g. in the range from 0...360 °.
The signal CDATA-X0 is often used as a trigger for cyclic calculations in addition to the motion control of the application in the controller, or for the handshake with a higher-level control system.
The following conditions must be observed for the 'switching' of CDATA-X0:
- The signal is always output when the x position of the motion profile is crossed
- The signal is not always output when approaching the position x = 0
- A valid profile cycle is internally derived in the FB CDATA from a zero crossing of the x axis of the profile and the exceedance of 1/2 the profile clock pulse length.
- The output can be forced by setting the input CDATA-XRESET and simultaneous selection of CDATA-X-START=0. (If necessary, only set the x axis when the controller is inhibited to ensure that the drive will not move.)
Application example:
A motion profile with a clock pulse length of 0...360° is controlled by a master value selection at CDATA-XIN. During the initialisation of the master value encoder or for a process-related intervention of the operator, the master position of the x axis must be reset to '0', if necessary.
If the master position is reset within a profile clock pulse in the range from 181...360 ° of the current master angle, CDATA-X0 will be set.
If the master position is reset within a profile clock pulse in the range from 0...180 ° of the current master angle, CDATA-X0 will not be set.
Explanation: The conditions for zero crossing are not met because 1/2 the profile clock pulse length has not been exceeded.
Remedies:
For initialisation processes for setting the master position to 0, if necessary, the control signal CDATA-XRESET can be set for a short time to force the status output CDATA-X0.
By using a comparison function (function blocks PHCMPx) between the master position and the clock pulse length (CDATA-X-ACT and CDATA-ACTLEN) it is also possible to build up a status signal for detecting the profile zero crossing in the application.
For detailed information on the above-mentioned function blocks, please see the product documentation for the servo controller 9300EK.
