In this study, a novel concept for a downhole flywheel energy storage module to be embedded in a bottom-hole-assembly (BHA) is presented and modeled, as an alternative power source to existing lithium-ion battery packs currently deployed in measurement-while-drilling (MWD) or logging-while-drilling (LWD) operations. Lithium-ion batteries disadvantages include deteriorated performance in high temperature, limited lifetime that necessitates frequent replacement which elevates operational costs, and environmental disposal. Extreme and harsh downhole conditions necessitate that the flywheel module withstands temperatures and pressures exceeding 300 ?F and 20 kpsi, respectively, as well as violent vibrations encountered during drilling. Moreover, the flywheel module should adhere to the geometric constraints of the wellbore and its corresponding BHA. Hence, a flywheel sizing procedure was developed that takes into consideration the required energy to be stored, the surrounding environmental conditions, and the geometric constraints. A five-axis magnetic levitation control system was implemented and tuned to maintain continuous suspension of the flywheel under the harsh lateral, axial and torsional drilling vibrations of the BHA. Thus, an integrated finite element model was developed that included the rotordynamic behavior of the flywheel and the BHA, the component dynamics of the magnetic levitation control system, and the cutting dynamics of the drillbit for both PDC and tricone types. The model also included a newly developed coupling between lateral, axial and torsional vibrations. It was demonstrated through simulations conducted by numerical integration that the flywheel maintains levitation due to all different types of external vibration as well as its own lateral vibration due to mass unbalance. Moreover, a passive proof-mass-damper (PPMD) was developed that suppresses axial bit-bounce vibrations as well as torsional vibrations, and was extended to also mitigate lateral vibrations. Optimized values of the mass, stiffness and damping values of the PPMD were obtained by the hybrid analytical-numerical Chebyshev spectral method that was superior in computational efficiency to iterative numerical integration. This also enabled the fine-plotting of an operating stability chart indicating stability regions where bit-bounce and stick-slip are avoided. The proof-mass-damping concept was extended to the flywheel to be an active proof-mass-damper (APMD) where simulations indicated functionality for a light-weight BHA.

This thesis discuss the possibility to position control a rotor levitated with active magnetic bearings. The controller type considered is model predictive control which is an online strategy that solves an optimization problem in every sample, making the model predictive controller computation-intense. Since the sampling time must be short to capture the dynamics of the rotor, very little time is left for the controller to perform the optimization. Different quadratic programming strategies are investigated to see if the problem can be solved in realtime. Additionally, the impact of the choices of prediction horizon, control horizon and terminal cost is discussed. Simulations showing the characteristics of these choises are made and the result is shown. / Det här examensarbetet diskuterar möjligheten att positionsreglera en rotor som leviteras på aktiva magnetlager. Reglerstrategin som används är modellbaserad prediktionsreglering vilket är en online-metod där ett optimeringsproblem löses i varje sampel. Detta gör att regulatorn blir mycket beräkningskrävande. Samplingstiden för systemet är mycket kort för att fånga dynamiken hos rotorn. Det betyder att regulatorn inte ges mycket tid att lösa optimeringsproblemet. Olika metoder för att lösa QP-problem betraktas för att se om det är möjligt att köra regulatorn i realtid. Dessutom diskuteras hur valet av prediktionshorisont, reglerhorisont och straff på sluttillståndet påverkar regleringen. Simuleringar som visar karakteristiken av dessa val har utförts.

Thesis deals with active magnetic bearing (AMB) levitation control design. Its prototype was done in FSI collaboration with FEKT VUT Brno. The research is focused on communication tools and mathematical model making as well as general AMB issues. Based on this the control design is done an experimentally verified.