@conference{
author = "Vidaković, Jelena and Kvrgić, Vladimir and Lazarević, Mihailo and Stepanić, Pavle",
year = "2019",
abstract = "A development of a robot control system is a highly complex task, and many advanced
control strategies have been used for the purpose of overcoming nonlinear dynamic
coupling between the robot links and uncertainties in robot dynamics. Factors such as
characteristics of the mechanical design, applications for which the robot is designed,
applied actuators, and implementation requirements have great practical value to a choice
of the potential control strategy. The spatial disorientation trainer (SDT), Fig. 1, is a modern
combat aircraft pilot training system which examines a pilot's ability to recognize unusual
flight orientations, to adapt to unusual positions and to persuade the pilot to believe in the
aircraft instruments for orientation, and not in his own senses. This device is modeled as a
4DoF robot manipulator with revolute joints. Regarding a choice of a control strategy for the
SDT, given that advanced robot control strategies often entail difficulties in implementation,
prospective benefits of their application compared with traditional control approaches need
to be analyzed using proper simulation techniques. Herein, computed torque (CT) control, a
single joint feedforward control method that implies cancelation of nonlinear coupled terms
in robot dynamic model, is considered for tracking of SDT’s time‐varying trajectories. The
performance of the traditional PID controller is compared to CT compensation added to the
feedback controller in Simulink. Model of the motor’s mechanical subsystem takes into
account inertia reflected on the rotor’s shaft (effective inertia), calculated from the inverse
dynamic model of the SDT for the programmed trajectory of the device. The structure of PI
speed controller and limitation of its gains in the simulation model is performed to achieve
the fastest response without overshoots and without exciting resonances of the mechanical
structure for all possible values of effective inertia. Gains limitation of PI speed controller
takes into account the lowest structural natural frequency of the SDT device calculated using
CAE software, and saturation is applied at the outputs of controllers on the bases of
maximum torques that chosen motors can achieve. Within CT compensation, the error in
load torque calculation from the dynamic model is assumed to be 5%. The reference speed
values are given as a series of discrete values obtained from the trajectory planner.
In Fig. 2a, trajectory tracking for axes k=1, 2.. 4 using two considered types of controllers are
presented. Reference values are given in blue, the controlled process variables obtained by
PI speed controller and by CT compensation added to PI speed controller are given in red
and green, respectively, and the obtained errors are given in Fig. 2b in the same colors.
The addition of the CT compensator to the PI speed feedback controller achieved
considerable improvement in trajectory tracking in simulation example, for a typical SDT
motion. The simulation results are significant regarding the choice of a control method for
the SDT, but are also useful regarding the design of the mechanical structure of the
manipulator, and consequently the appropriate choice of motors.",
publisher = "Kragujevac: Faculty of Engineering, University of Kragujevac, Department for Mechanical Constructions and Mechanization,",
journal = "Book of Abstracts for the 9th International Scientific Conference [on] Research and Development of Mechanical Elements and Systems, IRMES 2019, 08-10. September, 2022.",
title = "Computed torque control for a spatial disorientation trainer",
pages = "173-172",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4099"
}
