Smart Icing Systems Review, June 19-20, Aircraft Autopilot Studies Petros Voulgaris Vikrant Sharma University of Illinois

Smart Icing Systems Review, June 19-20, Objectives

Smart Icing Systems Review, June 19-20, Overview of the Talk Autopilot Modes Autopilot structures A few simulations Current and Future work

Smart Icing Systems Review, June 19-20, Autopilots  Longitudinal Modes – Pitch Attitude Hold (PAH) – Altitude Hold (ALH)  Lateral Modes – Roll Attitude Hold (RAH) – Heading Hold (HH)

Smart Icing Systems Review, June 19-20, Block Diagram for PAH K i /s KK KqKq Actuator Dynamics &Comp Delay A/C Dynamics  q PAH integrator  ref eeee

Smart Icing Systems Review, June 19-20, Block Diagram for ALH K i /s KhKh KqKq Actuator Dynamics &Comp Delay A/C Dynamics  q HrHr integrator H KK Washout filter ALH eeee

Smart Icing Systems Review, June 19-20, Block Diagram for RAH A/C Turn Coordination Loop gains  ref KK K i /s Actuator Dynamics & Comp Delay aa rr r  RAH

Smart Icing Systems Review, June 19-20, Heading Hold A/C Dyn. Turn Coordination Loop gains KK K i /s Actuator Dynamics & Comp Delay aa rr r   KK  ref HH

Smart Icing Systems Review, June 19-20, A/P Performance Local designs exhibit good performance and stability margin properties Gains are scheduled on A/C speed Overall A/P performs well over the operational envelope of Twin Otter for clean conditions

Smart Icing Systems Review, June 19-20, Simulation results : Case 1c Aircraft State : Initially trimmed at V = 76 m/s and H = 2300 m No icing Autopilots engaged : Altitude Hold till T = 370 s and then Pitch Hold is engaged. Maneuver made : pitch up by 11.5 degrees at T = 370 s and the pitch back at T = 420 s Velocity response Time (s) Velocity (m/s) Angle of Attack Vs Time Time (s) Angle of Attack (deg)

Smart Icing Systems Review, June 19-20, Case 1c : Pitch Up Case 1 continued : Height Vs Time Time (s) Height (m) Pitch Angle vs Time Time (s) Pitch Angle (deg) Elevator Deflection Vs Time Time (s) Elevator Def (deg)

Smart Icing Systems Review, June 19-20, Case 1i Aircraft State : Initially trimmed at V = 76 m/s and H = 2300 m. Icing : Gets fully iced in 100 seconds Starting at T = 0. Autopilots engaged : Altitude Hold engaged till T = 370 s and then Pitch Hold is engaged. Maneuver made : Pitch up to 17 degrees at T = 370 s and the pitch back at T = 420 s to its trim condition at T = 370 s Velocity Vs Time Time (s) Velocity (m/s) Angle of attack Vs Time Time (s) Angle of Attack (deg)

Smart Icing Systems Review, June 19-20, Case 1i : Pitch Up Height Vs Time Time (s) Height (m) Pitch angle vs Time Time (s) Pitch angle (deg)) Elevator deflection vs Time Time (s) Elevator deflection (deg))

Smart Icing Systems Review, June 19-20, Comparison Case 1c Case 1i Blow up of the pitch response Time (s ) Pitch angle (degrees) Blow up of the elevator response Time (s) Elevator def (deg) Blow up of the pitch response Time (s) Pitch angle (deg) Blow up of the elevator response Time (s) Elevator def (deg)

Smart Icing Systems Review, June 19-20, Case 2c Aircraft State : Aircraft initially trimmed at V = 76 m/s and H=2300m No icing Autopilots engaged : Altitude Hold engaged till T = 370 s and then Pitch Hold is engaged. Maneuver made : Pitch up by 2 degrees at T = 370 s and the pitch back to the initial trim at T = 420 s Velocity vs Time Time (s) Velocity (m/s) Angle of Attack vs Time Time (s) Angle of attack (degrees)

Smart Icing Systems Review, June 19-20, Case 2c : Pitch Up Height vs Time Time (s) Height (m) Pitch angle vs Time Time (s) Pitch angle (degrees) Elevator deflection vs Time Time (s) Elevator deflection (deg)

Smart Icing Systems Review, June 19-20, Case 2i Aircraft State : Initially trimmed at V = 76 m/s and H = 2300 m. Icing : The aircraft is allowed to get fully iced in 100 seconds. Autopilots Engaged : Altitude Hold engaged till T = 370 s and then Pitch Hold is engaged. Maneuver made : Pitch up by 2 degrees at T = 370 s and then pitch back to the trim state just before pitching up at T = 420 s Velocity vs Time Time (s) Velocity (m/s) Angle of Attack vs Time Time (s) Angle of attack (degrees )

Smart Icing Systems Review, June 19-20, Case 2i : Pitch Up Height vs Time Time (s) Height (m) Pitch angle vs Time Time (s) Pitch angle (degrees) Elevator deflection vs Time Time (s) Elevator deflection (deg)

Smart Icing Systems Review, June 19-20, Comparison Case 2c Case 2i Blown up pitch angle response Time (s) Pitch angle (degrees) Blow up of the pitch angle response Time (s) Pitch angle (degrees)

Smart Icing Systems Review, June 19-20, Case 3c Aircraft State : Initially trimmed at V = 60 m/s and H = 2300 m. No icing Autopilots Engaged : Altitude Hold engaged throughout and RAH is engaged after T = 370 s. Maneuver made : Roll by 10 degrees at T = 370 s and then roll back at T = 420 s Velocity vs Time Time (s) Velocity (m/s) Angle of Attack vs Time Time (s) Angle of Attack (degrees)

Smart Icing Systems Review, June 19-20, Case 3c : Roll Height vs Time Time (s) Height (m) Roll angle vs Time Time (s) Roll angle (degrees) Yaw Angle vs Time Time (s) Yaw angle (degrees) Pitch Angle vs Time Time (s) Pitch Angle (degrees)

Smart Icing Systems Review, June 19-20, Case 3c : Control deflections Elevator deflection vs Time Time(s) Elevator deflection (deg) Rudder deflection vs Time Time (s) Rudder deflection (deg) Aileron Deflection vs Time Time (s) Aileron deflection (deg)

Smart Icing Systems Review, June 19-20, Case 3i Aircraft State : Initially trimmed at V = 60 m/s and H = 2300 m. Icing : Aircraft gets fully iced in the first 300 s. Autopilots Engaged : Altitude Hold engaged throughout and RAH is engaged after T = 370 s. Maneuver made : Roll by 10 degrees at T = 370 s and then roll back at T = 420 s Velocity vs Time Time (s) Velocity (m/s) Angle of attack vs Time Time (s) Angle of Attack (degrees)

Smart Icing Systems Review, June 19-20, Case 3i : Roll Height vs Time Time (s) Height (m) Pitch angle vs Time Time (s) Pitch angle (degrees) Yaw angle vs Time Time (s) Yaw angle (degrees) Roll angle vs Time Time (s) Roll angle (degrees)

Smart Icing Systems Review, June 19-20, Case 3i : Control deflections Elevator deflection vs Time Time (s) Elevator deflection (deg) Rudder deflection vs Time Time (s) Rudder deflection (deg) Aileron deflection vs Time Time (s) Aileron deflection (deg)

Smart Icing Systems Review, June 19-20, Comparison Case 3cCase 3i Blowup of the Roll response for the clean case Time (s) Roll angle (degrees) Blowup of the roll response for the Iced case Time (s) Roll angle (degrees)

Smart Icing Systems Review, June 19-20, Some Conclusions Icing can cause saturation of control surfaces Icing can cause severe degradation in A/P performance Altitude cannot be held with elevator only There is a need to adapt overall A/P structure

Smart Icing Systems Review, June 19-20, Adaptation Three levels - Level 1 : Envelope Protection - Level 2 : Adapt current FCS gains - Level 3 : Augment with new FCS design

Smart Icing Systems Review, June 19-20, Level 1 : Pilot Command Module Adaptation A/C Dynamics Icing Characterization A/P & SAS K=K(V) Envelope Protection Module Pilot Control Inputs Ref. Comm. Inputs Aircraft Icing Parameters Sensor Meas.

Smart Icing Systems Review, June 19-20, Level 2 : Pilot Command Module & A/P Adaptation A/C Dynamics Icing Characterization A/P & SAS K=K(V, ) Envelope Protection Module Pilot Ref. Comm. Inputs Aircraft Icing Parameters Control Inputs Sensor Meas.

Smart Icing Systems Review, June 19-20, Level 3 : Augment with New A/P Design A/C Dynamics Icing Characterization A/P & SAS K=K(V, ) Envelope Protection Module Pilot Ref. Comm. Inputs Aircraft Icing Parameters Control Inputs New A/P Design Sensor Meas. + +

Smart Icing Systems Review, June 19-20, Envelope protection module Account for peak transient values Use of robust control methods Want for all t What is the maximum allowable ? A/C & A/P ypyp r Pilot inputs Variables to be limited

Smart Icing Systems Review, June 19-20, Our Approach to EP A Fact for all t iff for all t where : L 1 norm A simple bound on pilot stick commands G(s,  ) r ypyp Pilot inputs Variables to be limited A/C & A/P linearized dynamics

Smart Icing Systems Review, June 19-20, Concepts for new design Use robust control methods G(s,  ) depends on A/P Can find limits of A/P performance : want for What is maximum allowable Overall possible A/P’s ? Leads to guidelines for new A/P design A/C & A/P ypyp Variables to be limited r Pilot inputs } G(s,  ) w Disturbances

Smart Icing Systems Review, June 19-20, Current and future work