A Dynamic Testbed for Nanosatellites Attitude Verification

To enable a reliable verification of attitude determination and control systems for nanosatellites, the environment of low Earth orbits with almost disturbance-free rotational dynamics must be simulated. This work describes the design solutions adopted for developing a dynamic nanosatellite attitude simulator testbed at the University of Bologna. The facility integrates several subsystems, including: (i) an air-bearing three degree of freedom platform, with automatic balancing system, (ii) a Helmholtz cage for geomagnetic field simulation, (iii) a Sun simulator, and (iv) a metrology vision system for ground-truth attitude generation. Apart from the commercial off-the-shelf Helmholtz cage, the other subsystems required substantial development efforts. The main purpose of this manuscript is to offer some cost-effective solutions for their in-house development, and to show through experimental verification that adequate performances can be achieved. The proposed approach may thus be preferred to the procurement of turn-key solutions, when required by budget constraints. The main outcome of the commissioning phase of the facility are: a residual disturbance torque affecting the air bearing platform of less than 5 × 10−5 Nm, an attitude determination rms accuracy of the vision system of 10 arcmin, and divergence of the Sun simulator light beam of less than 0.5° in a 35 cm diameter area.

Design of a Reconfigurable Dynamic Testbed for Co-Design Method Validation

Physical testing as a technique for validation of engineering design methods can be a valuable source of insights not available through simulation alone. Physical testing also helps to ensure that design methods are suitable for design problems with a practical level of detail, and can reveal issues related to interactions not captured by physics-based computer models. Construction of physical and testing of physical prototypes, however, is costly and time consuming so it is not often used when investigating new design methods for complex systems. This gap is addressed through an innovative testbed presented here that can be reconfigured to achieve a range of different prototype design properties, including kinematic behavior and different control system architectures. Thus, a single testbed can be used for validation of numerous design geometries and control system architectures. The testbed presented here is a mechanically and electronically reconfigurable quarter-car suspension testbed with nonlinear elements that is capable of testing a wide range of both optimal and sub-optimal design prototypes using a single piece of equipment. Kinematic suspension properties can be changed in an automated way to reflect different suspension linkage designs, spring and damper properties can be adjusted in real time, and control system design can be changed easily through streamlined software modifications. While the specific case study is focused on development of a reconfigurable system for validation of co-design methods, the concept extends to physical validation using reconfigurable systems for other classes of design methods.