Design, fabrication and characterization of a micro-fluxgate intended for parallel robot application

Abstract

This paper presents a micro-magnetometer based on the fluxgate principle. Fluxgates detect the magnitude and direction of DC and low-frequency AC magnetic fields. The detectable flux density typically ranges from several 10 nT to about 1 mT. The introduced fluxgate sensor is fabricated using MEMS-technologies, basically UV depth lithography and electroplating for manufacturing high aspect ratio structures. It consists of helical copper coils around a soft magnetic nickel-iron (NiFe) core. The core is designed in so-called racetrack geometry, whereby the directional sensitivity of the sensor is considerably higher compared to common ring-core fluxgates. The electrical operation is based on analyzing the 2 nd harmonic of the AC output signal. Configuration, manufacturing and selected characteristics of the fluxgate magnetometer are discussed in this work. The fluxgate builds the basis of an innovative angular sensor system for a parallel robot with HEXA-structure. Integrated into the passive joints of the parallel robot, the fluxgates are combined with permanent magnets rotating on the joint shafts. The magnet transmits the angular information via its magnetic orientation. In this way, the angles between the kinematic elements are measured, which allows self-calibration of the robot and the fast analytical solution of direct kinematics for an advanced workspace monitoring.

MEMS fluxgate magnetometer for parallel robot application

“…The DC motor controller for the stages is connected to a PC via USB. A visual C# program allows intuitive activation and movement of the stages and provides programming of motion-sequences (Kirchhoff et al 2009b). Figure 6 shows a typical characteristic of the presented micro fluxgate magnetometers.…”

“…Details about the HEXA-robot have been discussed in Hesselbach et al 2005;Kirchhoff et al 2009b). The magnet is fixed on the joint shaft and rotates its magnetic direction during robot movement.…”