Semi-active damper

Hybrid Control of a 3-D Structure by Using Semi-Active Dampers... 

Agranovich, G., Ribakov, Y. (2010). A method for efficient placement of semi-active dampers in seismically excited structures. Structural Control and Health Monitoring, 17(5), 513-531. 

Fuzzy logic has been used to vary the mechanical properties of the control device. It has been applied for the reduction of longitudinal bridge displacement due to earthquake or traffic loading with variable dampers or control of structural vibrations with hybrid systems composed of base isolation and semi-active dampers. Fuzzy control is also used to regulate a structure with an MR damper system (Choi Kang-Min et al. 2004, Zhou et al. 2003). 

The clip optimal control has two parts the first part consists of designing a control law assuming that an ideal device is installed to the building. In the second part, a controller is designed allowing the semi-active damper to develop the force that the control law calculated. In the first part, any control law can be chosen. 

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)... 

As a final example of a MR fluid controlled adaptronic system, the smart prosthesis knee developed by Biedermann Motech GmbH [178-181] is presented. This system shown in Fig. 6.91 is a complete artificial knee that automatically adapts and responds in real-time to changing conditions to provide the most natural gait possible for above-knee amputees. The heart of this system is a small magnetorheological fluid damper that is used to semi-actively control the motion of the knee based on inputs from a group... 

The dynamic response of civil engineering structures subjected to earthquake excitation can be reduced by using passive control systems such as energy dissipation devices (e.g. viscous dampers, etc.). The advantage of these systems with respect to active and semi-active control systems consist in the fact that they don t require any power supply, therefore are quite reliable and they require least maintenance. 

Yalla, S. K., Kareem, A., Kantor, J. C. (2001). Semi-active tuned liquid column dampers for vibration control of structures. Engineering Structures, 23, 1469-1479. doi 10.1016/SO141-0296(01)00047-5... 

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. 

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... 

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... 

Other effective mechanical amplifying systems are also used for connecting semi-active and active dampers in order to reduce the control forces and the energy required for activation of control devices (Gluck, 2000, Ribakov, 2000). In this study efficiency of lever arm amplifiers for connection of active controlled devices is studied. First optimal locations of control devices are obtained. The amplifiers are used for further decreasing the number of control devices at each floor. 

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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