Inertial stabilized platforms consisting of a two-axis gimbal assembly are often modelled as two independent SISO systems, describing the dynamics of the elevation axis and the azimuth axis respectively. In reality the state of the elevation channel and the state of the azimuth channel affect each other. Hence, the system is better modelled as a MIMO system with coupled dynamics, which means that the system has multiple inputs and outputs, where each input can affect multiple outputs. Since the couplings between the elevation channel and the azimuth channel have a deteriorating effect on control it is of interest to analyse what gives rise to the coupled dynamics and if control performance can be improved by considering the coupled dynamics. For this purpose, this thesis attempts to derive a dynamic model of the system of interest, both with the aid of physical modeling and system identification. Both modeling methods result in models with similar dynamics which seem to capture the coupled dynamics in the relevant frequency range. From the physical modeling it can be inferred that the degree of coupled dynamics depends on the mass distribution of the two-axis gimbal assembly. For the specific configuration of the system used in this investigation, the degree of coupled dynamics proved to be relatively small with relatively small impact on control. Based on the derived models, three types of controllers were implemented, decentralized control, decentralized control with a decoupler and decentralized control with an inner loop for rejection of mutual disturbances acting between the elevation axis and azimuth axis. Compared to standard decentralized control, the decoupler resulted in a somewhat better reference tracking and in a somewhat worsened disturbance rejection. Compared to standard decentralized control, the inner loop disturbance compensator resulted in a somewhat better performance for reference and disturbance rejection. / Inertialstabiliserade plattformar bestående av en tvåaxlig gimbal modelleras ofta som två oberoende SISO system som beskriver dynamiken för rörelse kring elevationsaxeln respektive azimutaxeln. I verkligheten påverkar tillstånden i elevationskanalen samt azimutkanalen varandra. Därmed kan systemet bättre modelleras som ett kopplat MIMO system, vilket innebär ett system med multipla in och utsignaler, där varje insignal kan påverka flera utsignaler. Eftersom den kopplade dynamiken har en försämrande effekt på systemets reglerprestanda är det av intresse att undersöka varför den kopplade dynamiken uppkommer, samt om reglerprestanda kan förbättras genom att beakta den kopplade dynamiken. För att undersöka detta söker denna rapport att med fysikalisk modellering samt systemidentifiering bygga en modell av systemet som innehåller den kopplade dynamiken. Båda metoderna resulterar i modeller med liknande dynamik, som verkar fånga den kopplade dynamiken i det relevanta frekvensspannet. Från den fysikaliska modelleringen kan det härledas att graden av kopplad dynamik beror på massfördelningen av systemet. För den specifika konfigurationen av systemet som var föremål för denna undersökning visar det sig att den kopplade dynamiken är relativt svag med relativt liten inverkan på reglerprestanda. Baserat på de framtagna modellerna implementerades och undersöktes tre typer av controllers, decentralized control, decentralized control med en decoupler, samt decentralized control med en inre loop för kompensering av störningar mellan elevations- och azimutaxeln. Jämfört med endast decentralized control gav decouplern något bättre reglerprestanda med avseende på reference tracking, men något sämre reglerprestanda med avseende på disturbance rejection. Jämfört med endast decentralized control gav en inre loop för kompensering av störningar mellan elevations- och azimutaxeln något bättre reglerprestanda med avseende på reference tracking samt disturbance rejection.

This work focuses on modeling, parameter estimation, and real-time position control of a two axis Gimbaled Mirror System (GMS) which is designed and manufactured to move an IR spot generated by an Infra Red Scene Generator System (IRSGS) in two orthogonal axes (elevation and azimuth) within the IR scene which is also generated by the IRSGS. Mathematical models of the GMS, the control system, and the disturbance torque originated from the movements of Flight Motion Simulator (FMS), on which the IRSGS will be mounted, are constructed using MATLAB&reg / /Simulink&reg / and MATLAB/Simulink/SimMechanics&reg / . Parameter estimations of the GMS and control system elements are achieved using MATLAB/Simulink Parameter Estimation Tool&reg / . The controller tuning is performed using the developed mathematical models in MATLAB/Simulink environment. Optimized digital PID controllers are implemented in the real-time control system. Performances of the controllers for both GMS axes are evaluated by both real system tests and simulation runs / and the results of these runs are compared. Controller performances under the effect of disturbances are analyzed by using the mathematical models developed in the MATLAB/ Simulink environment.

Nowadays, high portion of tactical missiles use gimbaled seeker. For accurate target tracking, the platform where the gimbal is mounted must be stabilized with respect to the motion of the missile body. Line of sight stabilization is critical for fast and precise tracking and alignment. Although, conventional PID framework solves many stabilization problems, it is reported that many PID feedback loops are poorly tuned. In this thesis, recently introduced robot control method, proxy based sliding mode control, is adopted for the line of sight (LOS) stabilization. Before selecting the proposed method, adaptive neural network sliding mode control and fuzzy control are also implemented for comparative purposes. Experimental and simulation results show a satisfactory response of the proxy based sliding mode controller.

The aim of the thesis was to implement and compare control methods in a model of a main battle tank. Three controllers were implemented in a two axis gimbal model and their performances were compared. The comparisons were performed using step changes in the reference signal, frequency analysis of an oscillating reference signal and disturbances, and turret mass uncertainties. The results showed that the sliding mode controller had the best performance for both reference changes and disturbance attenuation. The PID controller had a better performance for the change in reference, compared to the model predictive controller, but a significantly worse disturbance attenuation. Due to model approximations, such as assuming ideal engines and noise reduction, the results likely show a better performance than what can be expected if applied on a real main battle tank. Therefore, the results show an upper limit of the stabilization performance of turret and barrel control and should only be used to compare the controllers. / Målet med uppsatsen var att implementera och jämföra reglermetoder för en teoretisk modell av en modern stridsvagn. Tre metoder implementerades i ett tvåaxligt gimbalsystem och deras prestanda utvärderades. Mer specifikt utvärderades regulatorernas respons för en referensändring, en referensstörning och osäkerheter i tornets massa och massfördelning. Utifrån dessa resultat jämfördes sedan reglermetoderna. Resultaten visade att sliding mode regulatorn hade bäst prestanda för både referensändring och referensstörningen när man tittar på frekvensanalys av mät- och processstörningar. PID-regulatorn hade en bättre prestanda än MPC-regulatorn för en referensändring men en sämre respons för en referensstö-rning. På grund av modellförenklingar som till exempel antaganden om ideala motorer och brusreduktion visar resultaten troligen en något bättre prestanda än vad som kan uppnås på en riktigt stridsvagn. Det medför att resultaten visar en övre gräns för vad styrsystemet för en stridsvagns torn- och eldrörsrotation kan uppnå.