Julian Seidel

Piezoelectric MEMS energy harvesting module based on non-resonant excitation

The paper reports the system design of a piezoelectric energy harvesting module for a tire based wireless sensor node application. Impacts of material propertie, generator design and power management circuitry are considered. In context of a non-resonant generator excitation scheme, dissipative damping mechanisms are investigated. In particular air damping is measured, simulated and modeled. A design procedure is presented to identify a geometry design space for the microgenerator consistent with application specific requirements.

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.

A novel MEMS design of a piezoelectric generator for fluid-actuated energy conversion

In this paper a novel MEMS design of a piezoelectric generator for fluid-actuated energy conversion is presented. An exemplary energy scavenging scenarios is introduced. Moreover, the electro-mechanical properties of different piezoelectric thin films (PZT, AlN, ZnO) are introduced and compared to each other. Depending on the specific load scenario optimum piezoelectric cantilever shapes are investigated. A point load at the free-end of a cantilever requires a triangular cantilever shape. Compared to a classical rectangular shape the electrical area energy density is three times larger. A maximum area energy density value of 35 nJ/mm2 is measured for the triangular cantilever shapes. A uniform load as occurring for fluid-actuated energy harvesting calls for a triangular-curved cantilever shape and is also superior to classical geometries.

Systementwurf eines MST basierten piezoelektrischen Versorgungsmoduls für energieautarke Anwendungen

Zusammenfassung Der Systementwurf eines piezoelektrischen Versorgungsmoduls für ein energieautarkes Reifendruck-Kontrollsystems (RDKS) wird beschrieben. Hierfür werden der Generatorentwurf unter Einbeziehung des piezoelektrischen Materialsystems sowie die Auslegung der spezifischen Schnittstellenschaltung betrachtet. Die vorgestellte, auf einer analytischen Modellierung beruhende Entwurfsmethode, erlaubt es einen geeigneten Parameterraum für die Generatorgeometrie zu identifizieren. Abstract The system design of a piezoelectric MEMS energy harvesting module based on analytical modelling is described. The application example of a wireless sensor node for tire pressure monitoring system (TPMS) is considered. System considerations comprise the generator design, material impact and the generator interface circuitry. A design procedure is presented, which allows to identify a suitable geometry design space for the piezoelectric microgenerator.

MEMS-based piezoelectric energy harvesting modules for distributed automotive tire sensors

This article presents the realization of a new energy self-powered sensor node. The wireless node is supplied by 10 μW of electrical power and is able to send three measured values in intervals of 80s. The power supply is carried out with a MEMS-based piezoelectric vibration converter. A specially developed ASIC for this type of generator takes over the energy management. The wireless connection to a base station is established by a microcontroller predestinated for energy autonomous applications in conjunction with a standard IEEE 802.15.4 RF-frontend. The used Route Under MAC wireless protocol is specifically designed for energy-saving operations. The protocol supports the IPv6/6LoWPAN standard whereby multiple sensor nodes can be integrated in a wired network.

A new approach of a shape-optimized piezoelectric MEMS generator for fluid-actuated energy scavenging

In this paper a new approach of a shape-optimized piezoelectric MEMS generator for fluid-actuated energy scavenging is presented. Different energy scavenging scenarios are introduced. Depending on the specific load scenario optimum piezoelectric cantilever shapes are investigated. A point load at the free-end of a cantilever requires a triangular cantilever shape. Compared to a classical rectangular shape the electrical area energy density is three times larger. A maximum area energy density value of 35 nJ/mm2 is measured for the triangular cantilever shapes. A uniform load as occurring for fluid-actuated energy harvesting calls for a triangular-curved cantilever shape and is also superior to classical geometries.

System design and modeling of a piezoelectric energy harvesting module

Energy harvesting systems (EHS) use externally-derived energy to power small autonomous devices. They provide unique capabilities for numerous applications, such as tire pressure monitoring systems (TPMS). Conventional TPMS are powered by batteries and are mounted on a wheel rim. Assembling the monitoring system on the inner liner of the tire enables additional parameters to be detected,1 such as tire temperature, friction, wear, and side slip. These parameters are useful for optimized tracking and engine control. However, this innovative use of EHS sets severe requirements for implementation. For instance, the EHS must be robust within the tire environment, weigh less than seven grams to avoid tire imbalance, and last at least eight years. Implementing these last two requirements is especially challenging with a battery-based approach, and favors implementation of energy harvesting microelectromechanical systems (MEMS). MEMS implementation faces numerous challenges. Large dynamic forces can occur within the tire environment, ranging from tens to thousands of gravitational acceleration units. Movable parts of the generator device must be designed to tolerate these forces. Therefore, a conventional mass-loaded cantilever design2 with a seismic mass in the gram range is critical. Furthermore, there is no stable frequency spectrum available within the tire environment. Therefore, the conventional concept of tapping mechanical energy by stimulating the generators’ seismic mass with an excitation at the resonant frequency is not suitable. Alternative generator concepts must be developed that exhibit a minimum of mass and operate with a non-resonant excitation scheme. The harvesting module should also be less than 100mm2 in area to replace the battery. Figure 1. MEMS piezo cantilever generator. (a) Device schematic. (b) Scanning electron microscope image of a test structure.