Grazvydas Kazokaitis
Kaunas University of Technology, Lithuania
Title: Spherical magnetic drive for attitude control on nano satellites
Biography
Biography: Grazvydas Kazokaitis
Abstract
Small satellites are great tools for various research and analysis tasks. They can work like standalone units or to be modular and combined together to the clusters. Depending on their missions and provided exercises, various orientation and positioning systems are needed. Attitude control systems can be with active or passive elements. Typically, these systems are driven by: gravitational forces, permanent or electromagnets, reactions wheels or thrusters. Small satellites have limited capabilities and many restrictions for size, composition, energy consumptions. Nowadays most popular systems consume significant amounts of energy, takes a lot of volume. As a possible option for alternative attitude control mechanism spherical magnetic drive was submitted. Spherical permanent magnet has stable dipole and when it orientates with the Earth’s magnetic field, attitude control can be achieved. This developed drive combines advantages of active and passive systems. The drive is fairly simple: permanent magnetic sphere is inserted between two ring-shaped piezoelectric actuators. Electrodes of the piezoelectric rings are divided into three equal sectors and are excited by separate harmonic signal. The out-of-plane bending and radial vibration modes of the piezoelectric rings are excited to obtain elliptical motion of the contacting points and rotate magnetic sphere about three axes. Amplitude and duration of the applied signal depends on rotation or motion trajectory of the sphere. In addition, it must be mentioned that actuator can be driven by burst type signal in order to achieve very high resolution. Using this technique, controlled movement of magnetic sphere is achieved. Numerical and experimental studies were performed to verify operating principle and output characteristics of the actuator. The aim of study was to investigate vibration modes of the piezoelectric actuators and identify resonance frequencies at which these piezoelectric actuators generate 3-DOF rotational motion of a spherical rotor with high resolution, determinate further development steps.