I am designing a discrete model predictive position controller for a dc motor tracking a reference of angles. My output response for the position tracking is as a step like response where for example it steps from a current value to the next with no transient phase . Is that a logial response to have a non transient response and if it's logical how to get the rise settling times of such a response
It seems that some settings of controller are unrealistic, such as the amount of control input in the constraints.
The constraints due to the physical limitations of an electric motor should be considered in the controller design.
By adding a constraint to limiting motor current or limiting the rate of output changes (ramp rate), you can reduce the response speed and increase the settling time.
Discrete model predictive controller is a nonlinear control algorithm. The logical response analysis, which can be easily done for PID-control, requires a linearization for the control system which may be difficult and not accurate with this type of control. So, I think that there are two possible tests for your question:
1- Apply step change for the control reference from 0 to 100% of its value and see the response on the controlled variable.
2- Apply a step change to the motor load and see the response on the controlled variable.
You can get the rise time by determining the time between 10% to 90% of the step response of the controlled variable.
The following paper may help you:
https://ieeexplore.ieee.org/document/8708773