why the nonlinear model of a small UAV cant give correct results when using a discret PID?

hi, i have a nonlinear model of a small UAV controlled by PID controller, when using the continuous PID, it gives the desired results, but when using the discret version of the PID controller, it doesnt give results.

the discret version of the PID is implemented using the xilinx system generator and it is correct because we tried with other models and it gave us good results.

so, i dont konw where is the problem exactly? we tried with changing the sampling time, as we tried to make a lot of changes, but no results?? i hope from you to give me a a solution thank you very much

Answer 1

[David Sanchez]

Hi, what do you mean by "it doesn't give results"? Does that mean the UAV becomes unstable or that the system crashes? If the UAV becomes unstable with the discrete PID, I think you should re-tune the PID parameters and/or adjust the sample time. I had a similar problem time ago and it worked for me. Good luck

[djalal ACHACHA]

hi, thank you very much for your help. now let me explain more. for example, for the current time am controlling the airspeed of the UAV: first of all i put the desired speed 25m/s, so when using the continuous PID, it gives the desired speed which is 25m/s. but, when using the discret PID, it gives us always 50m/s. we used to change the sampling time from small ranges to bigger ones, but always gives us 50m/s. i hope that i explained more.

[Arkadiy Turevskiy]

that does not really help. Any way you could share the model?