0

I modeled a control loop with a hysterisis controller and a saw. I identified the saw as PT4 system. So this PT4 block is my plant. Now the controller gives me a relative position value for the saw. Retract 0,3 mm or extend 0,3mm. The plant wants to have a absolute position. Therefore I made a feedback from the actual position of the saw to an add block with the relative position. So far so good. The control loop works. The only problem is the start, as the simulated value starts at zero. So it takes some time till the saw is extended to the desired position. Later before controlling starts the saw is extended to 8.6mm. Accordingly I wanna start my simulation at 8.6mm too.

How can I do this?

I tried to use an initial condition block but this didn't change anything.

Figure 1 shows the output of the control loop with the problem at the beginning.

Figure 2 shows the feedback

Figure 3 shows the output of scope42 with IC block set to 8.6.

output

control loop

scope42

user47091
  • 523
  • 2
  • 6
  • 16

1 Answers1

0

Put Initial Output of Transport Delay block to 8.6

Additionally: Your Transfer Fcn block (PT4) needs conversion if you want to have initial conditions other than zero. Please check this.

durasm
  • 174
  • 3
  • 10
  • it is better but still not perfect. How would I realise it in a hardware in the loop simulation, as there won't be a transport delay block. – user47091 Feb 12 '16 at 14:18
  • @user47091 Did you try to convert your Transfer Fcn block as suggested above? – durasm Feb 15 '16 at 12:32
  • thanks for the advice, I didn't know that. But now I get this result [link](http://www.directupload.net/file/d/4266/duiuvyft_jpg.htm) although this is the step response of the pt4 system [link](http://www.directupload.net/file/d/4266/vhn78n4j_jpg.htm). It is very unstable at the beginning. – user47091 Feb 16 '16 at 19:21
  • @user47091 What simulation step are you using? Can you inspect values at first few steps around Transport delay and PT4. – durasm Feb 17 '16 at 08:22
  • I used a step size of 0.001 (1ms). This is the ouput [before](http://www.directupload.net/file/d/4273/jxopb4eh_jpg.htm) the transport delay and [after](http://www.directupload.net/file/d/4273/tbjt7mmb_jpg.htm) transport delay respectively before pt4. The result after the pt4 is shown above. – user47091 Feb 23 '16 at 16:32