An Experimental Evaluation of Generalized Predictive Control for Tiltrotor Aeroelastic Stability Augmentation in Airplane Mode of Flight

Abstract

The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of Generalized Predictive Control (GPC) for actively controlling the swashplate of tiltrotor aircraft to enhance aeroelastic stability in the airplane mode of flight are presented. GPC is an adaptive time-domain predictive control method that uses a linear difference equation to describe the input-output relationship of the system and to design the controller.The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered I/5-scale semispan aeroelastic model of the V-22 that was modified to incorporate a GPC-based multi-input multi-output control algorithm to individually control each of the three swashplate actuators. Wing responses were used for feedback. The GPC-based control system was highly effective in increasing the stability of the critical wing mode for all of the conditions tested, without measurable degradation of the damping in the other modes. The algorithm was also robust with respect to its performance in adjusting to rapid changes in both the rotor speed and the tunnel airspeed.

Analysis of tiltrotor whirl flutter in time and frequency domain

“…The second quasi-steady aerodynamic model is presented in Eq. (6). It is equivalent to replacing ( ) C k by 1 in Greenberg's aerodynamic model [9,10].…”

“…In the 1990's generalized predictive control (GPC), which is a digital time domain multiinput multi-output predictive control method, was experimentally investigated to evaluate the effectiveness of an adaptive control algorithm. Active control was introduced into the non-rotating swashplate using three high-frequency servo-controlled hydraulic actuators mounted aft of the swashplate inside the pylon fairing [3,6]. The GPC algorithm was highly effective in improving the stability in the critical wing mode tested.…”

Rotary-Wing Aeroelasticity: Current Status and Future Trends

“…A partial exception to this philosophy is represented by a recent experimental study that has evaluated an approach called generalized predictive control (GPC) to augment aeroelastic stability of a tiltrotor operating in the airplane mode. 108 The tests were performed on a 1 5 th scale, semispan aeroelastic model of the V-22, designed and built by Bell in 1981. A special tiltrotor research testbed called the Wing and Rotor Aeroelastic Testing System was used in the Langley Transonic Dynamics Tunnel.…”

Model Predictive Control of A Parafoil and Payload System

“…Using the model predictive control strategy, significant increases in damping of aircraft flexible vibration modes were achieved in a wind tunnel test. 4 The work reported here creates a model predictive control strategy for a parafoil and payload aircraft. Performance of the autonomous flight control system is shown through flight tests of the system under a variety of conditions.…”