FOPID Controller Prototype

Fol­low­ing research
Since this is a pro­to­type, the form fac­tor is not opti­mal.
of imple­men­ta­tion of dig­i­tal frac­tion­al-order con­trollers, I built a pro­to­type con­troller. The PLC mod­ule is based on the STM32F407 micro­con­troller. The i/o mod­ule was designed to sup­port some indus­try stan­dard inter­faces and has the fol­low­ing features:

  • Ther­mo­cou­ple input, sup­port­ing type K thermocouples;
  • Volt­age input, range: $\pm$10 V;
  • Cur­rent loop out­put: 0(4)$\dots$20 mA;
  • Volt­age out­put: range $\pm$10 V;
  • Sam­ple res­o­lu­tion: 12 bit on alanog chan­nels; 14 bit res­o­lu­tion of the ther­mo­cou­ple converter;
  • Sam­ple rate: up to 10kSPS;
  • Ref­er­ence volt­age: pre­ci­sion; on-board.

This set­up allows to con­duct exper­i­ments with lab­o­ra­to­ry equip­ment. An exam­ple exper­i­ment with the mag­net­ic lev­i­ta­tion sys­tem can be seen in this video.

Details about the imple­men­ta­tion can be found in my Ph.D. the­sis11A. Tepl­jakov, Frac­tion­al-order Mod­el­ing and Con­trol of Dynam­ic Sys­tems. Springer Inter­na­tion­al Pub­lish­ing, 2017..

Virtual Coupled Tank System

Click here to see the video of the device in action.
Vir­tu­al Cou­pled Tanks sys­tem (VCT) rep­re­sents a phys­i­cal imple­men­ta­tion of an indus­tri­al liq­uid lev­el con­trol process where the liq­uid tanks are emu­lat­ed by means of LCD screens.

The unit can work in stand­alone mode, or be con­trolled from a PC run­ning appro­pri­ate soft­ware. The process is mod­eled on an embed­ded device using pre­cise math­e­mat­i­cal mod­els. The device itselt can be seen as an inter­me­di­ate step between pure soft­ware sim­u­la­tions and real-life con­trol objects, as it pro­vides the phys­i­cal pre­sense of a cou­pled tanks sys­tem, yet requires no main­te­nance as a real-life device would.

The device is patent­ed11A. Tepl­jakov, E. Petlenkov, and J. Belikov, “Vir­tu­al cou­pled tank sys­tem,” Eston­ian Patent P201 400 045, 2017.. Depict­ed here is a pro­to­type built accord­ing to a spe­cif­ic con­fig­u­ra­tion: it has two inter­con­nect­ed tanks. It is of course pos­si­ble to build such sys­tems with cus­tom con­fig­u­ra­tions on demand for the pur­pos­es of student/control engi­neer training.


Laboratory equipment

I have man­u­fac­tured
Mil­li­volt­age source: man­u­fac­tured asset ver­sus pro­to­type
some lab­o­ra­to­ry equip­ment for edu­ca­tion­al pur­pos­es in Tal­Tech (small scale pro­duc­tion). The devices are used in automa­tion and con­trol the­o­ry relat­ed courses.

Two types of devices were designed and manufactured:

  1. Dig­i­tal­ly con­trolled mil­li­volt­age source (depict­ed here). This device fea­tures a rotary encoder with a push button—the user can change the out­put volt­age (includ­ing neg­a­tive volt­age) by rotat­ing the encoder, and cycle through avail­able lim­its using the push button.
  2. Type K ther­mo­cou­ple amplifier—this is a sim­ple, USB-pow­ered device that is used in a mea­sure­ment loop.

A few words
Hand-sol­der­ing such devices is almost nev­er done. But for a small series, it is doable.
about tech­nol­o­gy. The dig­i­tal­ly con­trolled mil­li­volt­age source PCBs were ordered from a man­u­fac­tur­ing plant (with the excep­tion of the pro­to­type which I pro­duced myself), while the ther­mo­cou­ple ampli­fi­er devices were all made using the ton­er trans­fer tech­nol­o­gy. All com­po­nents were hand-sol­dered and the cas­es were 3D-printed.

I have also man­u­fac­tured numer­ous DAQ and dig­i­tal con­trol boards which I have used in con­trol exper­i­ments through­out my Ph.D. study. Some rel­e­vant papers can be found in the pub­li­ca­tions list.