Research on the Method of Magnetic Liquid Tilt Sensor

This study focuses on the second-order buoyancy mechanism of magnetic liquids and proposes and implements a new type of miniaturized tilt sensor (with a tube length of 80 mm and an inner diameter of 5.5 mm). The paper first systematically reviews the theoretical models and research progress of the first-order and second-order buoyancy of magnetic liquids, pointing out that the second-order buoyancy can achieve the suspension and recovery of permanent magnets without an external magnetic field, providing a new idea for simplifying the structure and reducing the cost of sensors. Subsequently, the expression of the second-order buoyancy of the permanent magnet in the magnetic liquid was derived by using the "double mirror method", and a finite element model was established through COMSOL Multiphysics to simulate and optimize the magnetic field gradient and magnetic stiffness of the restoring magnet. The simulation results show that within the gap range of 0-1 cm, the restoring force rapidly decays from -150 N to -30 N, and the average magnetic stiffness reaches 1.2×10⁴ N/m, verifying the rationality of the magnetic circuit design. The experimental section established a full-range static test platform from 0° to ±40°, which was calibrated based on coal-based magnetic liquid samples. The results show that the output voltage of the sensor is in good linearity with the inclination Angle (fitting curve 0.007x² - 1.12x + 1.9), the hysteresis and repeatability errors are both 2.08%, the comprehensive accuracy is 0.3°, and the size is reduced by more than 20% compared with the traditional structure. This research provides a feasible technical route for the miniaturization and high-precision of magnetic liquid inertial devices.