Active mass damper

The most recent implementations are combinations of add-on devices. While mass dampers provide the majority of implementation (i. e., tuned mass dampers, active mass dampers, hybrid mass dampers), active stiffening or bracing systems, energy dissipation/absorption dampers and hybrid isolations were also implemented in actual applications or full scale experiments. It was noted in [188] that most of the systems were considered as add-ons and the integration of the systems into structural design is not yet completely developed. That is important in relation to the application of active control from practical (engineering) aspects. 

An active tendon system has been examined by using a six-story steel structure [187]. Figure 8.57 shows that a control force is transmitted to the structure through diagonal braces connected to the first floor by servo-controlled hydraulic actuators. The 600 ton symmetric building, as shown, has been erected in Tokyo, Japan. In fact, two control systems has been tested on the structure (a biaxial active tendon system and a biaxial active mass damper system). 

An example of an active system is described in Figure l.The figure shows a mass damper where Ihe connection with the main frame incorporates apowered actuator able to accelerate the auxiliary mass. Horizontal displacements and accelerations in the main structure are measured by sensors (dashed box) and this information goes (dashed arrows) to Ihe actuator, so governing its operation by means of a controller. Such systems are usually known as active mass dampers. 

Figure 1. Example of active (or semi-active) control system (active mass damper)...

The most famous active control device is the active mass damper (AMD), which uses a mass-spring-damper system combined with... 

Hybrid control refers either to a combination of passive and active systems or, more commonly, to a combination of passive with semi-active systems, aiming at lowering the forces required by active or semi-active systems, respectively. One such device is the hybrid mass damper (HMD), which combines tuned mass dampers with active actuators. The actuator force is mily used to increase efficiency and robustness to changes in structural dynamic characteristics. Also in the category of hybrid mass dampers is the active-passive composite tuned mass damper (APTMD) developed by Ohrui et al. (1994) and named DUOX. This device is composed of an active mass damper mounted on a timed mass damper. Fig. 8. During structural motion, the mass of the AMD is driven in the opposite direction of the TMD, therefore magnifying the motion of the passive device. When the building... 

Preumont A (2002) Vibration control of active structures, an introduction, 2nd edn. Kluwer, The Netherlands Reinhom AM, Soong TT, Lin RC, Wang YP, Fukao Y, Abe H, Nakai M (1989) 1 4 scale model studies of active tendon systems and active mass dampers for aseismic protection, technical report NCEER-89-0026 Slotin JJ, Li W (1991) Applied non linear control. Prentice Hall, New Jersey, USA... 

Restriction of achievable feed bandwidth and performance capability of machines High stiffness and damping with low mass required Active vibration suppression by semi-active and active ancillary systems (e.g., adaptive mass damper, adaptive friction damper)... 

The time delay between the beginning of a dynamic response and the counteraction of TMD is one of the most important topics in structural control (passive and active) from an engineering point of view. Therefore, Koshika et al. [193] have proposed an active-passive composite tuned mass damper (APTMD). The feasibility and the practicability of the theory was confirmed by demonstrating its control effect using an experimental model, as Fig. 8.50 shows. 

Tamura [194] shows several popular mechanisms of active vibration control systems for civil engineering structures. Mass damper systems, which use the inertia force of the auxiliary mass as the reaction force, are most commonly adopted. They need only a small space for installation and they can suppress the response of tall buildings very effectively during strong winds. 

The mass damper systems are classified into four types from the energy supply point of view the passive type (TMD), semiactive type (SAMD), full active type (AMD) and hybrid (HMD). The TMD is effective if the natural period of the device is tuned well to that of the tall building (mostly the fundamental mode). However, if the period of the device or the building gets changed, or the predominant period of the building response differs from the period of the device, the effectiveness of the TMD cannot be maintained. Therefore the other three types are developed to solve this problem. The... 

Koshika, N. et al. Research, development and application of active-passive composite tuned mass dampers. Proc. 4th Int. Conf. on Adaptive Structures, Technomic (1993)... 

Rasouli, S. K., Yahyai, M. (2002). Control of response of structures with passive and active tuned mass dampers. Structural Design of Tall Buildings, 11, 1-14. doi 10.1002/tal.l81... 

SEMI-ACTIVE TUNED MASS DAMPER SYSTEM... 

Most of the above studies have related to the use of dynamic vibration absorbers in mechanical systems. While application ofthese systems in civil engineering structures, frequently known as tuned mass damper (TMD) systems, is expected to be different. In last decades, many research studies have been performed to show the effectiveness of the TMD system and the other control devices, derived from TMD, such as semi-active tuned mass dampers (STMDs) and active tuned mass dampers (ATMDs) in civil engineering community in reducing the structural responses, some of which are reviewed in the following. 

The tuned mass damper (TMD) system is a typical form of control devices including a mass, spring, and a viscous fluid damper, which can be attached to the main structure at one of its degrees offreedom. This system is one ofthe well-accepted devices to control flexible structures, particularly, tall buildings. In this passive control system, if its damping ratio or stiffness of the spring changes with time, then it is called a semi-active tuned mass damper (STMD). 

The equation of motion of the building with a semi active tuned mass damper (STMD) control device is the same as the structure with TMD, but in this case the damping ratio of STMD is a time varying, and can be expressed as which... 

Chey, M. H., Chase, J. G., Mander, J. B., Carr, A. J. (2009). Energy-dissipative semi-active tuned mass damper building systemsfor structural damage reduction. Paper presented at the International Symposium. 

Hrovat, D., Barak, P, Rabins, M. (1983). Semiactive versus passive or active tuned mass damper for structural control. Journal of the Engineering Mechanics Division, 109,691-705. doi 10.1061/ (ASCE)0733-9399(1983)109 3(691)... 

Semi-active tuned mass damper systems. 19 Australasian Conference on Mechanics of Structures and Materials (ACMSM), Christchurch, New Zealand. 

Pinkaew, X, Fujino, Y. (2001). Effectiveness of semi-active tuned mass dampers under harmonic excitation. Engineering Structures, 23(7), 850-856. doi 10.1016/SO141 -0296(00)00091 -2... 

Fukushima, I., Kobori, T, Sakamoto, M., Koshika, N.,Nishimura, I., Sasaki, K. (1996, September). Vibration control of a tall building using active-passive composite tuned mass damper. Paper presented atthe Third International Conference on Motion and Vibration Control, 1-6, Chiba, Japan. 

Liedes, T. (2009). Improving the performance of the semi-active tuned mass damper. University of Oulu. Finland Oulu University Press. 

Semi Active Tuned Mass Damper (STMD) In passive TMD system, if its damping ratio or stififiiess of the spring changes with time, then it is... 

Active devices are able to change the control force, applied to the stmctuie according to the optimal control requirements. They allow more effective control, but external energy source is required for activation of these devices. In other words, active controlled devices externally activated and apply control forces to the stmcture in order to improve its performance. Active devices include active tendons, active tuned mass dampers and actuators. 

Introducing an additional mass-stiffiiess-damping element at the mass to modify the Eigen frequeneies (Figure 3a). There may be passive masses or active or semi-active systems using e.g. eontrol to accelerate the mass to minimise the deflection of the mass niy Such mass-stifl iess-damping systems are called compensators, absorbers or tuned mass dampers. 

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