System modeling of a piezoelectric energy harvesting module for environments with high dynamic forces

This paper reports the design of a piezoelectric energy harvesting module for a tire based wireless sensor node. System considerations comprise the generator design, material impact and the generator interface circuitry. A design procedure is presented, which allows identifying a geometry design space for the piezoelectric microgenerator consistent with given specifications. For the addressed application a large dynamic force range occurs for a given mass. The acceleration is in the range of some ten up to some thousand units of gravitational acceleration. Therefore, a conventional generator cantilever design with a mass in the gram-range is critical. For our design we use a piezoelectric MEMS generator approach without seismic mass. The intrinsic mass of the cantilever is in the microgram region and the resulting acceleration forces are very small. For the energy transfer from the environment to the generator we suggest a non-resonant excitation scheme. Tire related forces during the period of tread shuffle passage are to be used for a pulsed excitation of the generator. Based on analytical modeling the system parameters are calculated for a given generator geometrical design. The results are utilized to identify a design space consistent with given requirements and operation conditions.