Design of a Real-Time Test Bench for UAV Servo Actuators

Abstract

Reliable flight operations of Unmanned Aerial Vehicle (UAV) in the class above 25 kg impose strict requirements on the flight control and propulsion system. Research demonstrators however, evolve around unique aircraft configurations, while fulfilling unconventional missions. These properties increase the complexity of the on-board electromechanical devices. The latter usually rely upon Commercial off-the-shelf (COTS) components, instead of sufficiently documented, verified products. Insight into individual performance and reliability figures of these components must therefore be obtained by conducting ground-based laboratory tests. The presented test bench resembles a dynamometer for emulating aerodynamic loads on UAV servo actuators under pre-defined conditions, with the capability of monitoring and recording the relevant test parameters.

Identification and Modeling of the Airbrake of an Experimental Unmanned Aircraft

“…In order to assist the identification of the airbrake servo actuator performance and allow for the derivation of a mathematical model representing its operating characteristics, a dynamometer test bench was developed [4]. It offers two main testing modes: a force-free configuration (see Fig.…”

“…The results of the first two campaigns (Test campaign I & II) and a detailed description of the test setup are found in [4] while results of Test campaign III are newly generated applying gradually increasing load as the servo Table 2 for different loads and the same deflection command (97.5 • ). Later Test campaign III data is applied to verify the realistic behavior of the servo model.…”

“…To identify the servo dynamics the test bench presented briefly in Section 3 and in detail in [4] was applied making measurements with different frequency doublet servo angle setpoint inputs and different loads. The parameters of the whole measurement campaign are summarized in Table 4.…”

“…One to test the whole airbrake mechanism under load including the servo motor, the opening linkages and the airbrake with artificial aerodynamical load [9]. The second is to test the dynamics of the servo motor with different load levels [4]. A preliminary identification of the system dynamics was done in [9] which is extended and refined with several new contributions in this article.…”

“…Identification of the servo dynamics itself is a challenge as the literature sources also show. First a servo test bench was developed and measurements with doublet series servo angle references on different frequencies and with different load torque levels were carried out (see [4] and [9]). In our case system identification is complicated by saturation in the inner servo controller (control saturation also considered in [13]) and load dependent maximum angular velocities of the servo which differ if servo travels against or with the load (similar load issue is considered in [18]).…”