NTN Develops the World's First “Magnetic Array Type Rotation Sensor”

Makes High-Precision Rotation Angle Detection Possible with a Compact Sensor

NTN Corporation (Osaka) in cooperation with Shizuoka University has jointly developed a “magnetic array type rotation sensor” that is compact yet can detect rotation angles with a precision of 0.36° (1/1000^th of one rotation).

With conventional rotation sensors it is difficult to establish both compact size and high precision due to difficulties in the manufacturing precision of the magnetic encoder rings with alternating north and south poles and the fact that a separate signal processing circuit is required for detecting absolute angles.

The newly developed sensor is based on a concept by Shizuoka University Research Institute of Electronics Professor Shoji Kawahito. By integrating over 500 magnetic sensor elements arranged into a rectangular shape magnetic sensor array on the surface of a semiconductor chip, the rotation angle of the corresponding magnet is detected without contact.

The absolute rotation angle of the magnet is calculated via arithmetic processing of the magnetic field profile measured by each magnetic sensor element. Consequently, the detection resolution increases and the need for high-precision positioning of the magnet is eliminated. The magnetic sensor elements, AD conversion circuit(*), and angle calculation circuit are integrated on a 4.2mm square sensor chip to simultaneously compact size and improve functionality.

Potential applications include compact equipment that requires high-precision positioning and robot joints that require absolute angle information immediately after power is supplied. NTN will move forward with licensing the results of this research and opening up applications for bearings with rotation sensors and angle sensors in cooperation with Shizuoka University and the Hamamatsu Foundation for Science and Technology Promotion Shizuoka TLO (STLO), which operates technology transfer projects.

This technology won the Beatrice Winner Award for Editorial Excellence, at the International Solid State Circuit Conference (ISSCC2005). This conference, known as the Olympics of integrated circuits, was held this February in San Francisco.

(*) AD conversion circuits convert analog signals into digital values.

[Features]

1. New compact, high-precision angle detection technique using a magnetic sensor array
2. Can detect absolute angles (Can judge the angle immediately after power is supplied)
3. Eliminates the need for high-precision positioning of the magnet and sensor (tolerance ±0.4 mm)
4. Can be manufactured with standard semiconductor processes

Left: Magnetic array type rotation sensor Right: The rotation sensor-integrated ball bearing(#608)

[Features of Developed Product]