How rotary position sensing lifts aerospace designs to new heights


As a little kid, I loved claiming the window seat of an airplane. Watching the city shrink as we took off was fascinating, and I was captivated by the castles of clouds that seemed within arm’s reach. As I got older, I experienced the thrill of watching the sunset span the horizon. Now an airplane’s window seat offers an even more fascinating view: a glimpse into how a 300-passenger airplane flies.

Looking out the window during takeoff and landing, you’ve probably been mesmerized as pieces on the wings of the airplane move and adjust. The piece at the front of the wing is called the slat, while the piece at the rear is called the flap (Figure 1). During takeoff and landing, the slats and flaps extend to increase the area of the wing, which increases the aerodynamic lift. This is necessary for the airplane to take off at a slower speed and helps create drag during landing. Slats and flaps are critical parts of an airplane’s high-lift system.

 Figure 1: Aircraft slats and flaps

The movement of the slats and flaps on each wing must be symmetric, and the control system robust and redundant. Due to the extreme environments that an aircraft faces, resolver sensors – which are known for their performance in rugged environments such as automotive, industrial and aviation applications – are often used to monitor the position of the slat and flap surfaces. A resolver sensor interface integrated circuit (IC) is used to convert the sine and cosine signal to a digital signal that can then be interpreted by the microcontroller (MCU).

A new chip from TI, the PGA411-Q1 resolver-to-digital converter (RDC) is a highly integrated resolver interface that simultaneously excites the coils of a resolver sensor and calculates the angle and velocity of a rotating motor shaft for the motors driving aircraft slats and flaps (Figure 2). This is completed without many of the external components required by competitive solutions, thus minimizing printed circuit board (PCB) size and cost, and enabling increased scalability for multiple design platforms.

 Figure 2: High-lift system block diagram

Resolver rotary position sensing technology can help make an airplane soar. Watch from the window seat and enjoy the view of how these designs enhance the way we fly.

What considerations do you face when designing for resolver-to-digital conversion in automotive, industrial and aviation applications? Log in to post a comment below.

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