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This paper presents a flight envelope protection system for NASA’s Transport Class Model. The developed protection scheme is based on a command-limiting architecture that accounts for aircraft adverse aerodynamics, unusual attitude, and structural integrity and is designed to augment a standard gain-scheduled flight control law. The scheme also includes an energy protection system, which relies on an automatic throttle control loop that implements a total energy control law. In the setup adopted, the limits of the protected envelopes are actively adjusted to ensure, on the one hand, that the aircraft always stays in a safe flight condition and, on the other hand, that the pilot has enough control authority to perform aggressive maneuvers, if needed. Batch simulations demonstrate the efficacy of the protection system in maintaining the aircraft within desired safe conditions.

Automated manufacturing of large scale parts often involves multiple collaborating robots and requires high positional accuracy. Depending on the layout of the work cell multiple robots may be installed on a common supporting structure such as a shared linear axis. In such layouts the accuracy of each robot is fundamentally limited due to elastic deformations of the supporting structure. For example, moving one robot may introduce position errors to a second robot even if all axes of the second robot are held fixed. Standard robot calibration procedures do not account for these interdependent effects in collaborative robotic work cells. In this article, we propose a concept to compensate for position errors introduced by the compliant behavior of the supporting structure. The concept is based on an elastic multibody simulation model of the work cell. Furthermore, we present a method to detect elastic deformations experimentally. The measurement data is used to calibrate the compliance parameters of the model. Experimental results show that real-time model-based compensation significantly reduces position errors due to elastic deformations.

Reference tracking and vibration suppression are typical goals in motion control systems. Standard feedforward methods to achieve these goals are inversion-based feedforward control and input shaping. The former achieves perfect tracking but lacks robustness to uncertainties in the system dynamics while the latter may account for robustness at the expense of reduced tracking performance. In this work, a continuous time finite-impulse-response (FIR) prefilter design for linear systems is proposed which allows to trade off tracking performance against robustness. The approach is based on a finite time linear quadratic (LQ) optimal control formulation of the filtering task. Robustness is taken into account by penalizing large magnitudes of the trajectory sensitivity. Tracking delay can be reduced by adjusting the filter length which is a free design parameter. With the proposed prefiltering scheme fast and robust tracking can be achieved. An important application is simultaneous tracking and vibration suppression for motion systems with uncertain elasticity parameters which is used as a simulation example.

Subject of this paper is an industrial gantry robot with elastic behavior. To suppress residual vibrations command shaping filters are widely used. These filters, however, change the shape and duration of the originally commanded trajectory. Therefore, a command shaping filter is proposed which is based on the inverse model of the flexible robot dynamics. To that end, a planar dynamics model of the robot is derived which is suitable for control design. It captures the relevant dynamics of vibrations including the non-minimum phase characteristics. Based on the inverse dynamics, a feedforward filter for vibration suppression is developed. The tracking error due to filter delay is reduced compared to other command shaping techniques. The non-minimum phase properties of the flexible dynamics are avoided by using a virtual reference point for plant inversion. Experimental results show the effectiveness of the proposed Inverse Model Command Shaper compared to other types of filters tuned for vibration suppression.

Motivated by the problem of loss-of-control prevention, this paper presents a dynamic flight envelope protection system for NASA’s Transport Class Model. The developed protection scheme is based on a command-limiting approach that accounts for aircraft adverse aerodynamics, unusual attitude, and structural integrity, and is implemented around a standard gain-scheduled flight control law. The scheme also includes an energy protection scheme, which relies on an automatic throttle control system that implements a total energy control law. Preliminary batch and pilot-in-the-loop simulations demonstrate the efficacy of the protection system in maintaining the aircraft within desired safe conditions, without limiting the ability of the pilot to perform aggressive, evasive maneuvers.