Download Template for submissions

Poster
Contact-free electro-magnetic reactance based mechanical
tension sensors
Authors:
Phillip Coerlin; Christian Leiser; Tobias Kitzler; Tobias Senkbeil;
Anatol Schwersenz; Sebastian Schwiertz
TRAFAG GmbH Sensors & Controls, Kelterstrasse 59, 72669 Unterensingen, Germany
[email protected]; [email protected]; [email protected];
[email protected] [email protected]; [email protected];
Abstract
Movement determines our life. Therefore it is substantially to know the forces we need to
get in movement. By electro-magnetic stimulation of the bulk material in mechanical
components like shafts and pull rods it is possible to conclude onto the mechanical tension
situation. Through inductive sensors in a specific geometric constellation to the transmitter
the sensor signals can be used to measure torsional moments or tensile and compressive
stress.
The system integration of planar coil systems, magnetic flux conductors and advanced
calculation algorithm regarding the transmitter- and sensors signal results in an advanced
contactless sensor adaptable for any mechanical stress measurements.
Due to the perfect laterally reversed arrangement of the sensor coils to the transmitter the
stress strength can be recalculated into their components. Hereby arises a new contact-free
sensor for numerous applications.
Figure 1.
Principle of the measurement
In shafts and rods without permanent magnetization the magnetic domains are in random
orientation (Figure1.). With the rising strain the magnetic domains arrange more and more.
Whereas compressive and tensile strain leads to common mode orientation to the force axis
torque moments will result in a screw-line arrangement.
The stimulation with an alternating magnetic field leads to a response of the domains.
These responses will be measured simultaneously by quadrant-sensors. With the
measurement of the four signals and calculation in the implemented electronic the strain is
determinate.
In Figure2- Figure5 is shown how the different stress situations e.g.in a shaft can result in
different arrangements of the magnetic domains.
Orientation of the magnetic domains
without torque, compressive or tensile
stress.
Figure2.
Change in the orientation of the
magnetic domains under compressive
stress. (Common Mode)
Figure3.
Change in arrangement under tensile
stress.
Figure 4.
Torque as a superposition of tensile
(green) and compressive (red) stress
lines.
Figure 5.
Hardware integration
By integrating of all coils into planar PCB-based coil
system the repeatability and geometric precision were
achieved to make the sensor working without any
balancing and producible in high volumes. The integration
of the complete sensor electronic into the sensor head
makes the system vastly compact and robust against
external influences. (Figure6)
The result is an ultra-compact sensor for all mechanical
strain situations. They can be used as scales, torque
meter, force sensors and further various measurements
where mechanical stress is involved.
Figure 6.