## 1 Introduction  
Base Isolation is a technique that has been successful in mitigating vibrations in the dynamic system [1, 2]. For building structures, it is commonly introduced at the foundation level which isolates the superstructure from earthquake accelerations that can be destructive to the structure [3, 4]. Through base isolation, the superstructure is decoupled from the vibrations and the frequency of the dynamic system is thus modified [5, 6]. Base isolators working on conventional principles are prone to vulnerabilities to far-fault and near-fault earthquakes [7, 8]. Earthquakes from far faults feature low-frequency range vibrations that can induce resonance and amplify the response of the structure [9, 10]. Near-fault earthquakes have vibration characteristics of a high amplitude and long-period velocity pulse resulting in failure of the base isolator itself [11, 12, 13]. Further, the seismic isolators working on conventional principles have been ineffective for near-fault earthquakes, as they cause the structure to operate in its inelastic range for even design level earthquakes [1; 2]. When a structure goes in the inelastic range, several fatigue-related issues [14; 15] have to be considered, which makes the problem of vibration control even more challenging. Then, the passive nature of base isolators working on conventional principles limits the effective operation of the devices to only the predicted earthquakes and renders them ineffective for unprecedented earthquakes in the area [16; 17]. Efforts have been made to overcome the problems associated with conventional vibration control techniques [18; 19]. Active base isolation systems are designed by introducing active control strategies in tandem with passive base isolation [20]. These work by external energy supplied to the system that imparts forces to structure [21]. So far, numerous active control mechanisms and strategies have been adopted by researchers and structural engineers. Consequently, several active base control systems have been proposed and studied [22; 23]. [PERSON] et al. [24] studied the shape control of structures undergoing inelastic deformations by employing an active pulse/force system. [PERSON] et al. [22] proposed the application of robust control in tandem with base isolation to minimize the total structural displacement and velocity. The control forces are designed in a way to overcome the forces generated by the isolation system at the base of the structure. [PERSON] et al. [25] investigated the application of LQG and He\(\infty\) control strategies with hybrid base isolation systems by computer simulations. Additionally, several efforts have been made in parallel to verify the effectiveness of active base isolation systems in minimizing the structural response [23; 26]. Despite a great number of efforts on analytical and experimental research, numerous full-scale structures have still been equipped with active control systems, and the implementation of base isolation with active control around the world has not been adopted yet. The primary reasons for this are the lack of real-time controllable isolation devices, high budget requirements for both implementation and maintenance, the requirement of high external power, system reliability and robustness, and lack of acceptance of non-conventional technology [21]. High power requirements of the actuators being a major challenge necessitated alternative approaches, which led to the developing of semi-active base isolation systems in which supplementary semi-active energy dissipation or displacement control devices are introduced [21]. These devices are adaptable and have low power requirements. Magnetorheological fluid (MRF) dampers have also been explored for base isolation [3; 27; 28]. MRFs are smart materials whose rheological properties can be controlled by changing the applied external magnetic field [29]. MR materials comprise of micro-sized iron particles dispersed in non-magnetic elastic matrix.