Project: Observer-based and repetitive control for a peristaltic pump

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Demcon is a company that develops a variety of new high-tech mechatronic systems such as the peristaltic pump system shown in Figure 1. During the design phase, a closed-loop controller was required that regulates the behavior of the system. Traditionally, linear PID-type controllers are designed due to their simplicity and wide use in industry. However, linear PID controllers are limited in suppressing disturbances close to or beyond the bandwidth. 

To overcome these limitations in view of disturbance rejection, one can use disturbance observer based control  (DOBC) as an add-on to classical PID control. Using DOBC, a real-time estimation of the actual disturbance to the system is made and instantly compensated. In literature, several methods and implementations of DOBC are found. In an earlier project, an M.Sc graduation student implemented an inversion-based DOBC controller for the peristaltic pump system, thereby making use of plant inversion to estimate the disturbance. Although the demonstrated performance improvement was promising, the method itself suffered from some strict constraints regarding causality and stability because inversion-based DOBC is mainly intended for random unknown disturbances.

The goal of this assignment is to replace the inversion-based DOBC by an alternative DOBC method that exploits the periodic nature of disturbances present in peristaltic pumps. Namely, if the disturbances are assumed to be periodic, the strict design constraints related to inversion-based DOBC could be relaxed such that further improvements become possible. A first step would be to design and implement a time-domain repetitive controller (or any other DOBC method that suffices) to improve performance by aiming at a constant rotational speed of the pump. As a second step, a transition to the position domain could be made to make the compensation independent of the actual pump speed. Third, one could add a flow sensor to reduce the flow ripple (which is a primary performance measure of the pump). An alternative development is the implementation of a flow ripple disturbance observer to obtain the same performance improvements but without the need of a flow sensor. 

About Demcon

Each one of our companies differentiates itself in its own domain with unique expertise and skills. This way they help customers improve their performance and achieve more. On the basis of their passion for technology our companies are able to combine forces. By sharing knowledge and working together we increase our social impact. Demcon is a developer and producer of technology and innovative products that contribute to solutions for technical and social problems.

What are you going to do?

A possible outline of the project could be:

  • Study literature about disturbance observer based control (including repetitive control)
  • Set up a model of the plant in Simulink
  • Design and simulate the new DOBC controllers using Matlab/Simulink
  • Perform a (nonlinear) stability analysis
  • Implement and test the new DOBC controllers on the setup available in the Demcon laboratory.

What do you bring to the table?

Required pre-knowledge:

  • M.Sc. education programme in Mechanical Engineering, Robotics or Systems and Control, including courses on control system design, and learning and adaptive control.


What do we offer you?

DEMCON offers a dynamic, growing and innovative organization. With our complex projects and multidisciplinary teams we offer you a lot of challenge and variety in this position. Thanks to enthusiastic and dedicated colleagues, our working atmosphere is good, open and informal, with a flat organizational structure.

You will have a regular supervisor to coach you and all mutual wishes and expectations are clearly agreed upon before the start of the assignment. Furthermore, the standard working method gives you the opportunity, in a motivating working atmosphere, to act within the team. So you get a good impression of what it is like to be part of the world of DEMCON. And that can be a very good start of your career.

Do you have any questions about this position?

Do you have any questions about this position? We will be happy to answer them. mail to Michiel Beijen, m.beijen@utwente.nl or Gijs Boerrigter, gijs.boerrigter@demcon.com

Are you interested in this graduation project? Then we look forward to receiving your cv. You can apply via the application button.

Acquisition based on this advertisement is not appreciated.

"bringing ambitious challenges to a success together."

application procedure.

Does this vacancy appeal to you and are you curious about the application process? This goes as follows:

1. Apply
You have applied! We will discuss it internally and respond as soon as possible.
2. Phone call
We got acquainted briefly and want to get to know each other better.
3. First call
See if there is a match from both sides and if the expectations are correct.
4. Second call
We investigate a possible collaboration more closely.
5. Offer
We both see the match! Let’s make you a suitable proposal.
6. Contract
Your response to the offer is positive. We are going to finalize the collaboration!