The development needs of handling and ride vehicle dynamic characteristics are constantly evolving, crucial for safety and comfortable commute since many active safety and driver assistance systems depend on these characteristics. Ride improvements enhance passenger comfort, which plays a significant role in quality and brand value. Chassis and suspension systems greatly influence these vehicle dynamic characteristics. These systems should provide stability, high precision and a high degree of adaptive performance with quick response time. One of the ways to achieve these demands is by incorporating mechatronics suspension systems. Semi-active and fully active mechatronics suspension systems offer passengers a more comprehensive range of vehicle characteristics in terms of driving experience than vehicles with purely mechanical suspension systems. The efficient implementation of mechatronics suspension systems depends on the controller type and how its commands are realised. A typical control strategy is to decide a desired behaviour on the vehicle body and realise that behaviour with the help of the semi-active or active actuators. This work focuses on the realisation of the modal coordinate controller commands that counteracts the undesired body motions. The commands are in vehicle body coordinates with respect to the COG of the vehicle. The biggest challenge is to translate these counteracting forces and torques into semi-active damper vertical forces. This challenge is addressed with different algorithms with different levels of complexity and capability. The complexity ranges from the linear system of equations to real-time optimisation. Essentially, the algorithms will fragmentise and distribute the centralised command among different actuators and finally realise them back as close as commanded by taking the actuator and other physical limitations into account. This work also focuses on developing relative weights tuning methods, which play a significant role in the cost function formation and optimisation solution. The algorithms are evaluated in three different road conditions to incorporate typical driving environments related to primary and secondary rides. The enhancements in the ride performance are visualised by comparing against the existing methodology. The conclusions strongly support the optimisation-based force allocation algorithm over the existing method. It enables significant improvements in the ride performance and a high degree of flexibility by efficiently distributing commands among four actuators, which results in utilising the full potential of the semi-active dampers. / Utvecklingsbehoven för fordons dynamiska egenskaper med avseende på åkkomfort och köregenskaper är ständigt föränderliga och är avgörande för säkerheten och bekväm pendling eftersom många aktiva säkerhets- och förarassistanssystem är beroende av dessa egenskaper. Åkkomfortförbättringar förbättrar passagerarnas komfort, vilket spelar en betydande roll för kvalitet och märkesvärde. Chassi och fjädringssystem påverkar i hög grad dessa fordonsdynamiska egenskaper. Dessa system ska ge stabilitet, hög precision och en hög grad av adaptiv prestanda med snabb responstid. Ett av sätten att uppnå dessa krav är genom att införliva mekatroniska fjädringssystem. Semiaktiva och fullt aktiva mekatronikfjädringssystem erbjuder passagerare ett mer omfattande utbud av fordonsegenskaper när det gäller körupplevelse än fordon med rent mekaniska upphängningssystem. Ett effektivt genomförande av semiaktiva eller aktiva fjädringssystem beror på styrenhetstypen och hur styrenhetens kommandon är realiserade. En typisk reglerstrategi är att bestämma ett önskat beteende på fordonets kaross och realisera det beteendet med hjälp av de semiaktiva eller aktiva dämparna. Detta arbete fokuserar på förverkligandet av de modala koordinatstyrkommandon som motverkar oönskade kroppsrörelser. Kommandona beskrivs i fordonskroppens koordinater med avseende på fordonets tyngdpunkt (COG). Den största utmaningen är att översätta dessa motverkande krafter och vridmoment till vertikala krafter för stötdämparna. Denna utmaning hanteras med olika algoritmer med olika nivåer av komplexitet och kapacitet. Komplexiteten sträcker sig från det linjära ekvationssystemet till optimering i realtid. I huvudsak kommer algoritmerna att fragmentera och distribuera det centraliserade kommandot bland olika dämpare och slutligen förverkliga dem tillbaka så nära kommandot som möjligt genom att ta hänsyn till ställdonet och andra fysiska begränsningar. Studien fokuserar också på att utveckla justeringsmetoder för relativa vikter, som spelar en viktig roll i kostnadsfunktionsbildningen och optimeringslösningen. Algoritmerna utvärderas under tre olika vägförhållanden för att inkludera typiska körmiljöer relaterade till primär och sekundär åkkomfort. Förbättringarna i körprestandan visualiseras genom att jämföra mot den befintliga metoden. Slutsatserna stöder starkt en optimeringsbaserad kraftallokeringsalgoritm över den befintliga metoden. Algoritmen möjliggör betydande förbättringar av prestandan och en hög grad av flexibilitet genom att effektivt fördela kommandot bland fyra ställdon, vilket resulterar i att utnyttja den fulla potentialen för de semiaktiva dämparna.

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Researchers have offered a variety of solutions for overcoming the old and challenging problem of undesired vibrations. The optimum vibration-control solution that can be a passive, semi-active or active solution, is chosen based on the desired level of vibration-control, the budget and the nature of the vibration source. Mechanical vibration-control systems, which work based on variable stiffness control, are categorized as semi-active solutions. They are advantageous for applications with multiple excitation frequencies, such as seismic applications. The available mechanical variable stiffness systems that are used for vibration-control, however, are slow and usually big, and their slowness and size have limited their application. A new semi-active variable stiffness solution is introduced and developed in this thesis to address these challenges by providing a faster vibration-control system with a feasible size. The new solution proposed in this thesis is a semi-active variable stiffness mount/isolator called the antagonistic Variable Stiffness Mount (VSM), which uses a variable stiffness spring called the Antagonistic Variable stiffness Spring (AVS). The AVS is a kinematically singular prestressable mechanism. Its stiffness can be changed by controlling the prestress of the mechanisms links. The AVS provides additional stiffness for a VSM when such stiffness is needed and remains inactive when it is not needed. The damping of the VSM is constant and an additional constant stiffness in the VSM supports the deadweight. Two cable-mechanisms - kinematically singular cable-driven mechanisms and Prism Tensegrities - are developed as AVSs in this thesis. Their optimal configurations are identified and a general formulation for their prestress stiffness is provided by using the notion of infinitesimal mechanism. The feasibility and practicality of the AVS and VSM are demonstrated through a case study of a typical engine mount by simulation of the mathematical models and by extensive experimental analysis. A VSM with an adjustable design, a piezo-actuation mechanism and a simple on-off controller is fabricated and tested for performance evaluation. The performance is measured based on four criteria: (1) how much the VSM controls the displacement near the resonance, (2) how well the VSM isolates the vibration at high frequencies, (3) how well the VSM controls the motion caused by shock, and (4) how fast the VSM reacts to control the vibration. For this evaluation, first the stiffness of the VSM was characterized through static and dynamic tests. Then performance of the VSM was evaluated and compared with an equivalent passive mount in two main areas of transmissibility and shock absorption. The response time of the VSM is also measured in a realistic scenario.

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