9/5/2012 3:54 AM | |
Joined: 9/27/2006 Last visit: 9/21/2024 Posts: 12282 Rating: (2684) |
Hello nayden; Welcome to our A&D forum. And may I say that for a first posting you ask a very interesting question. For Hamid and others whomighthave not heard of "relay autotuning" algorithms, hereare a fewquotes and links explaining it a bit more: http://ieeecss.org/sites/ieeecss.org/files/documents/IoCT-Part2-01AutoTuners-LR.pdf In relay auto-tuning, the process is first brought to oscillation by replacing the PID controller with a relay function (Figure 3). The controller parameters are then determined from the period and the amplitude of the oscillation. An interesting feature of relay auto-tuning is that it automatically generates signals that are customized for modeling critical aspects of the process. The relay can also be applied to a closed-loop system. For typical process control applications, the relay auto-tuners can be designed so that tuning can be executed simply by pushing a button; there is no need to set any parameters. The auto-tuner can also be used to generate gain schedules automatically. http://homepages.ihug.co.nz/~deblight/AUTResearch/papers/relay_autot.pdf As it turns out, under relay feedback, most plants oscillate with a modest amplitude fortuitously at the critical frequency. The procedure is now the following: 1. Substitute a relay with amplitude d for the PID controller as shown in Fig. 2. 2. Kick into action, and record the plant output amplitudea and period P. 3. The ultimate period is the observed period, Pu = P, while the ultimate gain is inversely proportional to the observed amplitude, Ku = 4d Having established the ultimate gain and period with a single succinct experiment, we can use the ZN tuning rules (or equivalent) to establish the PID tuning constants. Incidentally, the modified values given in Table 1 are improved versions of the original constants given in most textbooks which have been found to be excessively oscillatory.
|
This contribution was helpful to2 thankful Users |
Follow us on