controller_manager update rate

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To avoid a possible xy-problem: do you really need the update rate, or the delta t?

I need to make some computations on the controller that depend on the relation between the controller execution rate and some other input topic publication rate (which I already know). Basically, the controller needs to do something in x steps, where x = controller frequency/topic frequency.

I don't know of any API for this. Controllers are passed t and dt in their update(..) methods, so that could perhaps be used.

I don't know how universal it is, but some controllers store the update_rate parameter internally at initialisation. The joint_state_controller is one such ..

.. example (see here fi). In that particular case it's a private member variable, so not sure how useful that is for you.

Perhaps a board member with more in-depth knowledge of ros_control answers your question.

Thank you. However, in that case update_rate is used to guarantee that the controller makes something at a specific rate, which is not my case. I could do something similar to force a specific x, but I would still need to know the actual controller frequency to make sure that x is achievable.

... However, I guess I could use dt to compute the current frequency instead of using it as a parameter. Have to check what implications may have a (probably) dynamic x value in the computations.

It would be enough to know where does controller_manager get the information for calling update

the controller_manager does not call update(..). That is the responsibility of the entity running the control loop, which is typically done in the 'hw interface node'.