Inertial Ferrofluidic Sensor for Vibration, Displacement and Impulse Measurement with a Linear Output Signal

The aim of the work is to develop the uniaxial ferrofluid sensor suitable for use either as an accelerometer for low-frequency vibrations or as a ballistic device or seismic sensor for shock loads. The goal is achieved by solving the following problems: development of a magnetic suspension system with a linear axial gradient of the magnetic field strength, calculation of the viscous friction force of the magnetic fluid filling the coaxial layer between the magnetic cylinder and the non-magnetic body wall, manufacturing of the sensor and its static and dynamic tests. The most significant result of the work is the experimental confirmation of the linearity of the electromechanical system of the sensor, corresponding to the model representations of a linear dissipative oscillating system with one degree of freedom. The significance of the obtained results lies in the appearance of cheap and simple linear inertial sensors. The principle of operation of the sensor is based on the registration of the motion of an inert mass deviating from the equilibrium position under the action of an external force to be measured. The inert mass, consisting of ring permanent magnets, levitates in a coaxial layer of magneto-fluid lubricant. The sensor, depending on its parameters, can measure either quasi-static force, or force impulse, or coordinate displacement, which is in demand in monitoring systems for critical structures and buildings, as well as in navigation systems for vehicles operating under conditions of small, slowly changing accelerations (microgravity).