The process of harvesting mechanical energy from the environment and converting it to usable electrical energy can be illustrated as shown in the block diagram of Fig. 2.1. The input mechanical energy to be converted to electrical energy may be in the form of potential energy and/or kinetic energy. The mechanical system providing the mechanical energy for harvesting is hereinafter referred to as the “host system.” The host system may be capable of providing mechanical energy in a number of ways, for example, through linear or rotatory vibration of its structure; through a rocking motion such as experienced in a boat, ship, or buoy; through random relative motion between relatively rigid machine components, such as the motion between different links of a car suspension system; or through shock loading experienced by a weapon platform during firing or target impact.
In many cases, and depending on the mechanical-to-electrical energy transducer (electrical generator) being employed, an interfacing mechanism is needed for effective transfer of mechanical energy to the energy-harvesting device. Such interfacing mechanisms may, for example, be needed to amplify force or motion, vary the input force or motion frequency, convert a shock loading impulse to oscillatory or vibratory motion, etc. The interfacing mechanism may perform more than one function depending on the application, the host system, and the transducer characteristics. For example, in many cases, the interfacing mechanism is desired to maximize the rate or amount of mechanical energy transferred to the transducer. In other cases, this mechanism is used to “condition” the available mechanical energy to make the energy transfer possible while protecting the transducer and/or the host system. An interfacing mechanism may connect the structure or a component of the host system directly to the energy-conversion transducer or indirectly via certain intermediate elements such as vibrating structures or magnetic coupling elements.
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