Siemens_MS120 pages

MEMS ENERGY HARVESTERS

Special Advertising Section

RIM

MODELING
OPTIMIZES A
PIEZOELECTRIC
ENERGY
HARVESTER
USED IN
CAR TIRES
Siemens is using fluid-structure interaction simulation
to ensure the cost effective
optimization of a cantilever
in a MEMS generator
designed to power a tire
pressure monitoring system.
By JENNIFER HAND

THE DESIRE TO eliminate batteries and power lines is motivating a wide range of research. In the quest for systems
that are energy autonomous, the concept of energy harvesting is attracting a great deal of attention. Combine this
idea with operation at the micro level, and the “what if”
scenarios become even more enticing.
For researchers at Siemens Corporate Technology in
Munich, exploring the potential of an energy-harvesting
microelectromechanical system (MEMS) generator holds
strong appeal. As Ingo Kuehne, a senior engineer explains,
“Our mandate is broad. We are looking to develop platform
technologies for tomorrow rather than specific products;

S–

12

COMSOL MULTIPHYSICS

JUNE 2012

At the rim
valve hole
TPMS MOUNTING
On inner liner
of the tire

TREAD
SHUFFLE

TIRE

FIGURE 1: Two TPMS mounting options: on the rim or on the inner
lining of the tire.

CANTILEVER

PIEZO
CARRIER

FIGURE 2: Schematic of the piezoelectric MEMS generator energy

harvester. The cantilever is made of two materials, and electrical
energy is transferred through the circuit from the cantilever.

however, it makes sense to
demonstrate the value of
our research. Together with
our partner Continental
AG, we decided to focus on
an application with clear
commercial potential. Our
ultimate goal is to design
the MEMS generator to be
as small, light, and strong
as possible, with enough
energy to power a system under a range of conditions.” The researchers
chose to design a microgenerator for an innovative tire
pressure monitoring system

(TPMS) driven by motion.
TPMSs are traditionally powered by batteries,
they tend to be mounted
on the wheel rim. With
no reliance on a battery, such a system could
be placed inside the tire
(see Figure 1) and would
be in a position to measure much more than
pressure. It could monitor temperature, friction,
wear, and torque; assist
with optimal tracking and
engine control; and convey all this critical infor-

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