Writing a new Calculation Controller

Calculation controller (CalcController) are designed to built virtual axes over real axes.

For example: N-legs tables, energy motor, slits, rotated translations.

Minimal set of functions to implement

• calc_from_real(self, positions_dict)

  • Must return a dictionnary of virtual positions corresponding to <positions_dict> values of real axes.

• calc_to_real(self, positions_dict)

  • Must return a dictionnary of real positions corresponding to <positions_dict> values of virtual axes.

Note

Those 2 functions must be able to operate on numpy arrays, not only scalar values. Indeed, the limits checking feature before move needs to execute the calculation functions with numpy arrays.

Code example

Example of code to create a calculational controller to link 2 axes with a 3.1415 factor.

def calc_from_real(self, positions_dict):
    calc_mot_axis = self._tagged["calc_mot"][0]
    calc_pos = 3.1415 * positions_dict["real_mot"]

    return {"calc_mot": calc_pos}

def calc_to_real(self, positions_dict):
    calc_mot_axis = self._tagged["calc_mot"][0]
    real_pos = positions_dict["calc_mot"] / 3.1415

    return {"real_mot": real_pos}

Mockup calc controller

calc_motor_mockup can be found in bliss/controllers/motors/mockup.py

controller:
    class: calc_motor_mockup
    module: mockup
    axes:
        -
          name: $m1
          tags: real real_mot
        -
          name: calc_mot
          tags: calc_mot

Usage:

CYRIL [1]: wa()
Current Positions (user, dial)

  calc_mot       m1
----------  -------
   3.14150  1.00000
   3.14150  1.00000

CYRIL [2]: mv(m1,2)
CYRIL [3]: wa()
Current Positions (user, dial)

  calc_mot       m1
----------  -------
   6.28300  2.00000
   6.28300  2.00000

Note

During step scans, real axes positions for calculated axes will be emitted as an additional acquisition channel of the motor master – unless “emit_real_position” is set to False in the controller configuration