Compact energy-efficient magnetoresistive sensors for angle-, length and electrical current measurement in space applications

When?

Friday 21 September 2012, 11:30 to 13:30

Where?

SSC U13/15 BA 01

Open to:

Staff, Students

Speaker:

Dr. Rolf Slatter, CEO, Sensitec GmbH, Lahnau, Germany

Abstract

The Mars Science Laboratory launched from Cape Canaveral on 26th November 2011. On board is the Mars Rover “Curiosity” with over 40 magnetoresistive (MR) sensors that will be used for a variety of position sensing tasks. After the landing planned for August 2012 these sensors will join the 70 sensors that are already on Mars since 2004 on the rovers “Spirit” and “Opportunity”. What is less well known is that these sensors are developed and built in Germany.  Magnetoresistive sensors are now commonly found in automotive applications (e.g. for the wheel speed sensors for in ABS-system, or for the steering angle sensors in the ESP-system) as well as in industrial applications (e.g. position measurement systems in machine tools or industrial robots).  The advantages of this sensor technology are now beginning to be exploited in aerospace applications. The magnetoresistive effect offers a unique combination of bandwidth, resolution, miniaturization and robustness, that enables system developers to solve dynamic or precise measurement tasks in a wide variety of applications. This presentation will present this new sensor technology and describe the user benefits in a number of different space applications.  

The presentation will be structured as follows:

Basics of MR-Technology

The principle of operation, features and benefits of MR sensors will be described. This will be followed by comparisons with other sensor principles (optical, capacitive, inductive) as well as with other magnetic sensor principles (Hall, AMR, GMR and TMR).

Manufacturing Process

The wafer-, thin-film manufacturing and assembly processes used to produce MR sensors will be described briefly.

Design of MR Sensors

The design of a typical MR sensor will be explained, using the example of an angle sensor from a positioning system on a Mars Rover. Furthermore, the signal processing and particular design variants will be outlined.

Advantages and Benefits of MR Sensors

The compact dimensions, low weight and high robustness make MR sensors an interesting alternative to established technologies, such as resolvers and synchros.

Application Examples

A number of practical applications will be described. MR sensors have already been successfully applied in a number of space missions:
• Angle sensors for wheel drives, steering drives and robot arms on Mars Rovers (Fig. 1, Fig. 2)
• Positioning of a mechanical shutter in a spectrometer (Fig. 3, Fig. 4)
• Current measurement in the power electronics of a satellite

Outlook

Until now almost all aerospace applications have used MR sensors based on the anisotropic MR effect (AMR). Newer technologies such as Giant MR (GMR) or Tunneling MR (TMR) open up more applications due to a further decrease in size, higher sensitivity, as well as much reduced power consumption. The possibilities offered by these new MR technologies will be explained.