Author, Institution: Sylvester Sedem Djokoto, Kaunas University of Technology
Science area, field of science: Technological Sciences, Mechanical Engineering, T009
Scientific Supervisor: Prof. Dr. Egidijus Dragašius (Technological Sciences, Mechanical Engineering, T 009)
Dissertation Defence Board of Mechanical Engineering Science Field:
Prof. Dr. Giedrius Janušas (Kaunas University of Technology, Technological Sciences, Mechanical Engineering, T 009) – chairman
Assoc. Prof. Dr. Saulius Baskutis (Kaunas University of Technology, Technological Sciences, Mechanical Engineering, T 009)
Prof. Dr. Krzysztof Jamroziak (Wroclaw University of Sciences and Technology, Technological Sciences, Mechanical Engineering, T 009)
Prof. Dr. Artūras Kilikevičius (Vilnius Gediminas Technical University, Technological Sciences, Mechanical Engineering, T 009)
Prof. Dr. Renaldas Raišutis (Kaunas University of Technology, Technological Sciences, Measurements Engineering, T 010)
The doctoral dissertation is available on internet and at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).
The recent interest in researching various types of high precision actuators and sensors designs used in mechanical and mechatronic systems is overwhelming. The introduction of smart fluids has provided some form of improvement for the functionality of these high precision actuators and sensors. This research was focused on the improvement of the functionalities of three different devices. These improvements are 1. Damper for Cantilever Beam (CB), using the change in the rheological properties of the electrorheological fluid (ERF) as a damping medium, 2. Frequency enhancement for Piezoelectric Energy Generator (PEG), using the change in the rheological properties of the magnetorheological fluid (MRF) as a soft impacting medium, and 3. Spherical braking of a 3D Rotational Piezoelectric Deflector (RPD), using smart fluids as braking media.
In this thesis, the first application gave an improved way of using ERF as a damping medium for structures. The growing application of medium-sized mechanical and mechatronic structures has ignited a lot of interest among researchers. These structures are subjected frequently to vibrations, which is why a more robust design is necessary for them to perform under different conditions such as dynamic loadings. It is well known that vibrations are better controlled through the damping of the system. By applying a low-power control signal, smart fluids can be used to continuously vary the force for developing suitable damping.
The second application of MRF as a soft impacting medium introduced in this thesis was enhancing the output power of piezoelectric energy generators through a Vibro-impacting method. Piezoelectric energy harvesting is a process where available mechanical energy from the environment is converted into electrical energy. Piezoelectric materials can convert the mechanical vibrational displacement to electrical voltage and the other way round. Their application is found in a lot of modern wireless telecommunication devices as it is in cell phones.
In the third application, smart fluids were introduced as a braking medium for a 3D Rotational Piezoelectric Deflector. Rotational type deflectors like optical beam deflectors have many applications areas. The growing demand for miniaturization of satellites systems requires the design of small size micro-optical components which are compact, low energy consumption, agile, and robust. “Investigation of sphere trajectories of a rotational type piezoelectric deflector”). One of these miniature types of 3D rotational piezoelectric deflectors was designed at the Kaunas University of Technology. The 3D RPDs devices transform multi-directional resonant oscillations of piezoelectric transducers into an accurate continuous or step motion of a micro-mirror or deflector with high accuracy (up to 0.1). One of these miniature types of 3D RPDs was designed at the Kaunas University of Technology.