University of Twente Student Theses
Position Domain Repetitive-Control of a Peristaltic Pump
Celik, Kutay (2025) Position Domain Repetitive-Control of a Peristaltic Pump.
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| Abstract: | Peristaltic pumps are used in transporting contamination sensitive fluids with the use of flexible tubes, commonly found on medical devices. A pulley with rollers is spun by a motor. The rollers pinch the tube and transfer a small amount of liquid. The pump introduces disturbances due to its working principle, the rollers pushing on the tube impact the pump velocity. Another disturbance comes from the non-perfect commutation of the brushless DC motor used. DEMCON developed a medical device with a peristaltic pump. Currently the pump uses a PI2 controller, previously the effects of using a Inversion-Based-Disturbance-Observer-Based-Control (IBDOBC) was investigated. The research modelled the disturbance. Building on this, the current work proposes using the known disturbance model in combination with position-domain repetitive control to enhance performance. The disturbance modelled shows the disturbance is periodic. Therefore a controller exploiting the periodic nature of the disturbance is chosen as possible improvement. The disturbances have a fixed frequency in position domain, in terms of radians, but are aperiodic in case the pump speed changes in time domain, in terms of seconds. Position domain repetitive control is hypothesised to improve the performance of the pump. The Position-Domain-Control (referred to as SC) is built on the traditional control method Repetitive-Control (RC). To justify the use of SC, it is compared with RC and an intermediate controller between the two controllers, Disturbance-Observer-Based-Repetitive-Control (DOBRC). A major advantage of the time domain controllers is that they excel in rejecting periodic disturbances that match their design frequency and its integer multiples. However a major shortcoming, not present in SC, is that the disturbances that do not the design frequency or its integer multiples are amplified. Two papers are given after the literature review of DOBRC and SC that use ideas and results generated during the thesis. A plant model is made. Lagrangian Equations are used to formulate equations of motion, which are then linearised to obtain a linear time invariant system representation of the plant. The plant model is later used in the simulations and in making inverse approximations for the controllers using a disturbance observer framework to estimate the disturbance. Three scenarios were simulated, disturbance rejection, disturbance amplification by time domain controllers using a steady reference and an increasing reference signal in steps. The simulation results matched with the sensitivity plots and performance expectations. The experiments included DOBRC, SC, linear controller and IBDOBC from previous research. RC was omitted due to time constraints and due to DOBRC performing better in the simulations. It was not deemed useful to experiment with when the simulations showed DOBRC, another time domain repetitive controller outperforming it consistently. Two scenarios were experimented with, disturbance rejection and disturbance amplification by time domain controllers. The reference signals used were all steady state references. At the end SC and IBDOBC showed consistent performance as expected. DOBRC on the other hand had a significant difference between the disturbance rejection and disturbance amplification scenarios. In the best case scenario DOBRC performed best with a Root-Mean-Square error reduction of 68% form the current controller, then SC with 40% reduction, then IBDOBC with a 26% reduction and last the linear controller. In the worst case scenario DOBRC performed worse by 36% than the linear controller IBDOBC performed better than the linear controller, best performer was SC. |
| Item Type: | Essay (Master) |
| Faculty: | EEMCS: Electrical Engineering, Mathematics and Computer Science |
| Subject: | 31 mathematics, 50 technical science in general |
| Programme: | Systems and Control MSc (60359) |
| Link to this item: | https://purl.utwente.nl/essays/106466 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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