This model shows how the performance of a rotational energy scavenger can be explored using a simple representative model. Electrical energy is produced from an off-center mass attached to the shaft of a DC motor. The mass, geometry, motor and electrical parameters must be matched to the expected mechanical excitation. The generated electrical power is less than the extracted mechanical power primarily due to motor winding losses and viscous damping for the rotor. This example is based on Nunna, K. "Constructive interconnection and damping assignment passivity-based control with applications", Imperial College London (2014). The model here is simplified in that the DC-DC converter is omitted.
The plot below shows the dynamometer and suspended mass speeds along with generated and load currents plus battery charge.