This paper studies the dynamics of the proposed vibration energy harvester to develop the method of designs and controls for the system. The harvester converts vibrational energy into electrical energy through rotational motion of a mechanical pendulum or a so-called parametric pendulum. The rotation is maintained for periodic vibration with appropriate amplitude and frequency. However, such appropriate vibration is not always supplied from nature. For this reason, reasonable energy conversion requires system designs including the electrical circuit for output power and control methods to establish and maintain the rotation against vibrations of nature. The study on the load characteristics of the system indicates the possibility to control the behavior of the mechanical pendulum by regulating the electrical load and to improve the mechanical characteristics by designing the load.