A NOVEL APPROACH TO DYNAMIC FORCE CONTROL

This paper presents a new approach to dynamic force control of mechanical systems, in particular frame structures, over frequency ranges spanning their resonant frequencies. This is achieved using series elasticity and displacement compensation. Most mechanical actuation systems such as hydraulic and electromagnetic actuators are inherently velocity sources, that is, an electrical signal regulates their velocity response. Such systems are therefore by nature high-impedance (mechanically stiff) systems. In contrast for force control, a force source is required. Such a system logically would have to be a low-impedance (mechanically compliant) system. This is achieved by intentionally introducing a flexible mechanism between the actuator and the structure to be excited. In addition, to obtain force control over frequencies spanning the structure’s resonant frequency, a displacement compensation feedback loop is needed. The actuator itself operates in closed-loop displacement control. The theoretical motivation as well as the laboratory implementation of the above approach is discussed along with experimental results. Having achieved a means of dynamic force control, it can be applied to various experimental seismic simulation techniques such as the Effective Force Method and the Real-time Dynamic Hybrid Testin