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The ongoing development of numerous novel vertical takeoff and landing configurations necessitates flight control system design that enables the Simplified Vehicle Operations paradigm. This paper shows flight test results for one subscale lift-plus-cruise and one tilt-wing configuration employing such a flight control system architecture. Pilot inc...
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... second step, a series of short hover tests have been executed to further update and refine the control system gains necessary for stable hover performance. Once each vehicle was ready, a more extensive outdoor flight testing campaign was carried out at Sharpe Field in Tuskegee, Alabama, which has approximately 5,100 ft of runway length (shown in Fig. 1). This location was previously a training base for the Tuskegee Airmen in World War ...
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... four key outputs: (i) wingmounted propulsor thrust command (T /W ) cmd , (ii) wing tilt angle command, (iii) pitch command θ cmd , and (iv) thrust axis inclination θ TAI (used to aid in the generation first three commands only). The conditions that govern TCS switching between VFM, HFM, TFM, and FFM for the TW configuration are summarized in Fig. 10. During acceleration (departure transition), the VFM→HFM switch occurs when ground speed rises above 3 kts. However, during deceleration, the HFM→VFM switch occurs when ground speed drops below 6 kts and when the wing angle command δ w rises above 80 • , indicating that pitch attitudes below 10 • could be efficient for low-speed ...
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... feed-forward control component to approximately track the command using a lower-order equivalent system (LOES) representation. The feedback path includes a classical proportional-integral-derivative (PID) control action that provides stability, robustness, and disturbance rejection (Ref. 35). The general form of the EMF control system is shown in Fig. ...
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... Longitudinal (Pitch) Axis Figure 11. Explicit model-following (EMF) inner-loop control system The pitch axis has an attitude-command/attitude-hold (ACAH) implementation, where the input to the command model is the pitch attitude command θ cmd generated by the TCS algorithm. ...
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... in the field. The RRTV performed a departure and arrival transition maneuver, successfully transitioning from TCS mode 1 (VFM) to TCS mode 4 (FFM) and back to mode 1 (VFM). Throughout this maneuver, the wing angle mechanism had a partial failure, Resulting in the wing getting stuck at around 15 • . The effect of this is seen in the resulting plot (Fig. 13) from t = 45s to t = 60s, where the vehicle assumes a substantial nose-down pitch attitude to combat this and maintain altitude. The vehicle also suffered from GPS failures during the flight, as can be seen in the velocity trace with its multiple dips. This ultimately led to the vehicle landing in an uncontrolled manner. After around t ...
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Citations
... EMF control has been paired with adaptive control schemes 36 and also formed the basis for multi-input-multi-output control design approaches for rotorcraft 37 . Prior work by the authors [38][39][40] showed that rotary-wing and fixed-wing EMF principles could be combined for inner-loop control of a transitioning winged VTOL aircraft. ...
This paper describes a full-envelope Trajectory Control System with explicit model following architecture for a lift-plus-cruise configuration. The flight control system is optimized using a genetic algorithm with constraints on dynamic stability, stability margins, and control response. The optimized architecture is used to perform nonlinear simulations of representative operational maneuvers. In particular, transitions between vertical, hybrid, transition, and forward flight modes along climbing departure and descending arrival profiles are demonstrated both in calm air and turbulence. The results show that the proposed flight control laws and optimization scheme are effective at achieving smooth, accurate, and robust control system performance over the speed envelope of the vehicle.
... TECS adaptations for various configurations have been documented by several researchers: helicopters [59], quadrotors [60], tilt-rotor aircraft [61,62], and lift-plus-cruise VTOL UAVs [63,64]. Comer and Chakraborty have extended a modified TECS architecture to lift-plus-cruise [69,70] and tilt-wing configurations [71,72], successfully flight-testing a subscale lift-plus-cruise vehicle [73,74] with the control system. ...
... Several optimization techniques include similar objectives, including minimizing crossover frequency [32] and actuator usage [103,104]. Previous studies by the authors [74,109] have found that minimizing gain magnitudes influence these metrics. ...
... 7.3, incorporating constraints on dynamic stability, control responsiveness, response characteristics, and robustness. This workflow has been successfully used to optimize lift-plus-cruise, tilt-wing, and vectored-thrust configurations in prior work by the author[69,71,132,133] and also to support flight testing efforts[74]. The objective function (minimize type) employed for inner and middle loops pertains to deviation of the actual system response from the ideal(desired) response and minimization of gain magnitudes. ...
... It is also important to note that this limitation does not exist in R2022a, but it required PX4 ® v1.10.2, which had its limitations and was not feasible. The ACE Lab has developed a similar pipeline on PX4 ® v1.10.2 and deployed it on a tilt-wing aircraft, as outlined in [36]. In this work, however, we used R2023a along with a modified version of the PX4 ® v1.12.3. ...
Real-time (re-)planning is crucial for autonomous quadrotors to navigate in uncertain environments where obstacles may be detected and trajectory plans must be adjusted on-the-fly to avoid collision. In this paper, we present a control system design for autonomous quadrotors that has real-time re-planning capability, including the hardware pipeline for the hardware–software integration to realize the proposed real-time re-planning algorithm. The framework is based on a modified version of the PX4 Autopilot and a Raspberry Pi 5 companion computer. The planning algorithm utilizes minimum-snap trajectory generation, taking advantage of the differential flatness property of quadrotors, to realize computationally light, real-time re-planning using an onboard computer. We first verify the control system and the planning algorithm through simulation experiments, followed by implementing and demonstrating the system on hardware using a quadcopter.
... The characteristics of the respective sensors are selected based on flight test settings [26,27]. ...
... Figure 12 represents a general setup, including the generalized outputs from the TCS, inverse propulsor models, and EMF inner-loop controllers. This architecture has been used to optimize LPC, TW, and VT configurations in prior work by the authors [8,9,10,11,27,35] .The classification of the four Control Levels is identical for all vehicle configurations considered. • Control Level 2 (CL-2): Includes inner-loop stabilization and command tracking via the EMF controllers, which track pitch angle command θ cmd , bank angle command φ cmd , and yaw rate command r cmd . ...
... Several optimization techniques include similar objectives, including minimizing crossover frequency [29] and actuator usage [36,37]. Previous studies by the authors [27,35] have found that minimization of the gain magnitudes directly influence these metrics. The constraints employed during optimization are listed in Table 10. ...
To enable the Simplified Vehicle Operations paradigm for the upcoming urban/advanced air mobility vertical takeoff and landing concepts, their flight control system architectures must be designed to provide largely standardized control responses to pilot inceptor inputs. This paper demonstrates such a flight control system for three dissimilar vehicle configurations. It utilizes a novel Trajectory Control System for controlling longitudinal dynamics coupled to explicit model following inner-loop control. The Modular Aircraft Dynamics and Control Algorithm Simulation Platform is used to implement the flight control laws and optimize them to provide consistent responses for all three vehicles, as demonstrated through representative maneuver simulations.
... Previous work by the authors analyzed the LPC configuration through (i) simulation at the full scale [11,12], (ii) simulation at the subscale [13], and (iii) flight testing at the subscale [14,15]. These prior studies demonstrated favorable performance for a Total Energy-based FCS, the precursor of the proposed Trajectory Control System. ...
... To validate this novel FCS, a subscale LPC aircraft developed by the Vehicle Systems, Dynamics, and Design Laboratory (VSDDL) was flight tested with the TCS control architecture. This subscale vehicle along with other VTOL configurations, developed following the research and development pipeline shown in Fig. 1, have enabled rapid and cost-effective flight testing capabilities of novel FCS architectures [14,15]. ...
... Ganguli and Balas [35] examined these gains in NASA TSRV simulations, noting enhanced response times but potential transients. These insights have been incorporated into TCS for Forward Flight Mode (FFM) operations [15,36], with Comer and Chakraborty [11,12,33,37] enhancing vertical flight mode responsiveness using feed-forward gains. ...
This paper describes the flight test validation of a Trajectory Control System on a subscale lift-plus-cruise vertical takeoff and landing urban air mobility aircraft concept. The aircraft was sized using the Parametric Energy-based Aircraft Configuration Evaluator framework. A simulation model was developed using the Modular Aircraft Dynamics and Control Algorithm Simulation Platform. The flight control system was developed and optimized using a genetic algorithm optimization algorithm. The developed flight control system architecture was deployed to a Pixhawk flight controller for flight test validation. Flight testing was conducted at Sharpe Field, near Tuskegee, Alabama, which was a training airfield used by the Tuskegee Airmen during World War II. Piloted flights were performed to validate the flight control system and simulation model. The results demonstrated the successful implementation of Simplified Vehicle Operations design philosophies within the proposed flight control system through a series of flight tests, including manually piloted transition flights.
... Previous work by the authors analyzed the LPC configuration through (i) simulation at the full scale [11,12], (ii) simulation at the subscale [13], and (iii) flight testing at the subscale [14,15]. These prior studies demonstrated favorable performance for a Total Energy-based FCS, the precursor of the proposed Trajectory Control System. ...
... To validate this novel FCS, a subscale LPC aircraft developed by the Vehicle Systems, Dynamics, and Design Laboratory (VSDDL) was flight tested with the TCS control architecture. This subscale vehicle along with other VTOL configurations, developed following the research and development pipeline shown in Fig. 1, have enabled rapid and cost-effective flight testing capabilities of novel FCS architectures [14,15]. ...
... Ganguli and Balas [35] examined these gains in NASA TSRV simulations, noting enhanced response times but potential transients. These insights have been incorporated into TCS for Forward Flight Mode (FFM) operations [15,36], with Comer and Chakraborty [11,12,33,37] enhancing vertical flight mode responsiveness using feed-forward gains. ...
The complex vertical takeoff and landing configurations currently under development necessitate flight control system design that enables substantial reductions of pilot workload through Simplified Vehicle Operations. This paper shows optimization and simulation of such a flight control system architecture for a subscale vectored thrust aircraft configuration. A full-envelope Trajectory Control System for longitudinal dynamics was coupled with explicit model-following inner-loop controllers, and a scheduled control allocation logic. Control system parameters were determined using a genetic algorithm optimization scheme subject to dynamic stability, robustness, and control responsiveness constraints. Flight simulation results for a series of representative maneuvers including departure and arrival transitions and forward flight maneuvers are presented to demonstrate the effectiveness of the proposed flight control system architecture.
