Title: Tetrahedral redundant accelerometer block with geometry-consistent fault detection and isolation for strapdown inertial navigation systems

Authors: Van-Minh Doan; Van-Thinh Nguyen; Quoc-Dat Dang; Dinh-Dung Nguyen

Addresses: Institute of Control Engineering, Le Quy Don Technical University, Hanoi, Vietnam ' Faculty of Aeronautical Engineering, Air Defense-Air Force Academy, Hanoi, Vietnam ' Institute of Control Engineering, Le Quy Don Technical University, Hanoi, Vietnam ' Faculty of Aerospace Engineering, Le Quy Don Technical University, Hanoi, Vietnam

Abstract: Strapdown inertial navigation systems (SINS) on small UAVs and emerging eVTOL platforms are vulnerable to bias drift, measurement noise, and intermittent sensor faults - conditions that can rapidly erode navigation integrity when GNSS is unavailable or degraded. This paper presents a non-orthogonal, redundant accelerometer block and a geometry-consistent fault detection and isolation (FDI) method that jointly hardens SINS against single-sensor anomalies. Four accelerometers are mounted at the vertices of a regular tetrahedron; mounting angles are selected to minimise the trace of the measurement-error covariance, yielding an algebraic residual constraint across the four outputs. A two-level monitoring scheme is then applied: 1) a block-level residual test to flag abnormal behaviour, followed by 2) a cross-comparison that localises the faulty unit and distinguishes hard failures (signal loss) from deterministic drift, enabling exclusion or compensation while maintaining three-axis acceleration reconstruction. A laboratory prototype using low-cost MEMS devices (ADXL345) and real-time processing software demonstrates reliable single-sensor fault localisation and continued acceleration estimation during induced loss-of-signal and drift events. The combined sensor geometry and FDI logic provide a practical, lightweight approach to improving navigation resilience for cost-constrained air vehicles operating in GNSS-denied or contested environments, supporting safer and more sustainable autonomous flight operations.

Keywords: strapdown inertial navigation system; SINS; tetrahedral non-orthogonal sensor geometry; fault detection and isolation; FDI; GNSS-denied navigation; MEMS inertial sensors.

DOI: 10.1504/IJSA.2026.156039

International Journal of Sustainable Aviation, 2026 Vol.12 No.3, pp.292 - 307

Received: 22 Jan 2026
Accepted: 06 May 2026
Published online: 01 Sep 2026 *

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