Tabletop Testbed for Attitude Determination and Control of Nanosatellites

Abstract

In order to simulate the conditions of the space environment at ground, the Laboratory of Application and Innovation in Aerospace Science (LAICA) of the University of Brasília (UnB) is developing a dedicated testbed aiming at reproducing nanosatellite attitude motion. The testbed is composed of an air bearing table and a Helmholtz cage. The air bearing table is a spacecraft simulator that can simulate frictionless conditions with three rotational degrees of freedom. Balancing the simulator is essential in order to make the gravitational torque negligible. The testbed 1 Silva, Approved on June 18th, 2018 is also equipped with a Helmholtz cage whose purpose is to recreate the Earth magnetic field conditions that spacecrafts encounter in orbit. The design and realization of this low-cost testbed is presented in this paper. A simple and efficient automated balancing algorithm based on the Least Squares Method (LSM) is proposed and validated by experiments. The performance of the proposed simulator is evaluated and compared with previous works.

A Dynamic Testbed for Nanosatellites Attitude Verification

“…Despite being one order of magnitude higher than the typical disturbance expected for a CubeSat in LEO (≈10 −6 Nm), our result compares remarkably well with respect to the existing published data [28,29,43,44] (see Table 3), especially when considering the extremely low cost of our implementation, i.e., less than 500 Euro for IMU, actuators, control electronics, and balance masses. Once the balancing is completed, the residual disturbance torque, T D , is estimated, again through the sampling of free platform oscillations, by computing the angular accelerations retrieved from differenced IMU measurements.…”

“…Chesi et al [27] X X Wu et al [30] X X X da Silva et al [28,38] X X Kato et al [39] X X X Tavakoli et al [8] X X This work…”

“…Residual Offset r CM da Silva et al [28] >15 µm Liu et al [29] 5 µm Prado et al [43] ≈17 µm Young [44] <20 µm This work <1 µm…”

“…It can be cancelled only partially by design, and manual balancing does not lead to a guaranteed performance level [21]. Several automatic mass balancing systems have been proposed in the literature [28,29,36,37,43,44], as they can largely reduce the time necessary for the platform tuning while ensuring repeatability, and a more effective reduction of the gravity torque. Even so, the stated disturbance limit for testing nanosatellites can hardly be reached: assuming a total rotating mass (platform with balancing mechanism plus CubeSat) in the order of 10 kg, a matching between the CoR and CoM shall be achieved up to 10 nm level, if we want a torque in the order of 10 −6 Nm.…”

“…Residual Offset ‖ ‖ da Silva et al [28] >15 μm Liu et al [29] 5 μm Prado et al [43] ≈17 μm Young [44] <20 μm This work <1 μm Despite being one order of magnitude higher than the typical disturbance expected for a CubeSat in LEO (≈10 −6 Nm), our result compares remarkably well with respect to the existing published data [28,29,43,44] (see Table 3), especially when considering the extremely low cost of our implementation, i.e., less than 500 Euro for IMU, actuators, control electronics, and balance masses. Table 3.…”