Peter Nachtwey
Member
So you thought you would take the weekend off! No way. The link below is saying download me! Give me a try!
The link is to a spreadsheet that simulates a velocity control system instead of a position control system. The simulated system uses the same gain and time constant of last week's system. I even made it do the same motion profile only now it is in term of velocity instead of position. It is important to compare the two systems because you will see that there is a difference. One can see that velocity control systems are much easier to tune that position systems all other things being equal.
Simulations wise, the difference between the two systems is that the velocity control system is a type 0 system whereas the position control is a type 1 system. Type 0 systems are systems like velocity and temperature control where if the control signal is removed, the system will falls back to the original steady state. In the case of a temperature system this is ambient temperature and in the case of a velocity system this is stopped. A type 1 system has an extra integrator. A position system integrates velocity so that the feed back is position. A type one system will not go back to the original steady state. A position system will stop after coasting down when the control signal is removed, but the position will not return to the original starting position. The integrator in the type 1 system adds a pole ( a lag in response ) that makes tuning it harder. See the real poles sheet in the other thread to see what a pole does to the response of a system.
Knowing the type of a system is important when tuning a system. It gives you a clue as to how to adjust the gains.
As I said before the spreadsheet is just a velocity form of the position system of last week. However, it will tune differently. The equations that I use to calculate the gains are different. I leave it to you to find out what this difference is. The lowest ISE ( integrated squared error ) achievable is about 1660. This is because of the step input in the velocity when the target generator starts.
Simple Velocity System using a PID controller.
It will be interesting to hear of the results and the comments about the differences between the position and velocity system.
Have a nice weekend. I plan to hike and see some firework. We have the largest fireworks show west of the Mississippi at Fort Vancouver on the Columbia river. I will be checking in from time to time.
The link is to a spreadsheet that simulates a velocity control system instead of a position control system. The simulated system uses the same gain and time constant of last week's system. I even made it do the same motion profile only now it is in term of velocity instead of position. It is important to compare the two systems because you will see that there is a difference. One can see that velocity control systems are much easier to tune that position systems all other things being equal.
Simulations wise, the difference between the two systems is that the velocity control system is a type 0 system whereas the position control is a type 1 system. Type 0 systems are systems like velocity and temperature control where if the control signal is removed, the system will falls back to the original steady state. In the case of a temperature system this is ambient temperature and in the case of a velocity system this is stopped. A type 1 system has an extra integrator. A position system integrates velocity so that the feed back is position. A type one system will not go back to the original steady state. A position system will stop after coasting down when the control signal is removed, but the position will not return to the original starting position. The integrator in the type 1 system adds a pole ( a lag in response ) that makes tuning it harder. See the real poles sheet in the other thread to see what a pole does to the response of a system.
Knowing the type of a system is important when tuning a system. It gives you a clue as to how to adjust the gains.
As I said before the spreadsheet is just a velocity form of the position system of last week. However, it will tune differently. The equations that I use to calculate the gains are different. I leave it to you to find out what this difference is. The lowest ISE ( integrated squared error ) achievable is about 1660. This is because of the step input in the velocity when the target generator starts.
Simple Velocity System using a PID controller.
It will be interesting to hear of the results and the comments about the differences between the position and velocity system.
Have a nice weekend. I plan to hike and see some firework. We have the largest fireworks show west of the Mississippi at Fort Vancouver on the Columbia river. I will be checking in from time to time.