Jinwei Shen

Swashplateless Helicopter Rotor with Trailing-Edge Flaps

A helicopter primary control system with trailing-edge flaps was investigated numerically for its potential to replace a conventional swashplate system. Eliminating the swashplate and associated control system can lead to significant reductions in weight, drag, and cost and an improvement of rotor performance. A comprehensive rotorcraft analysis was developed for analyzing the swashplateless rotor configuration and was implemented to examine the actuation requirements for rotor primary control with trailing-edge flaps. A multicyclic controller was implemented with the swashplateless rotor analysis, and the feasibility of trailing-edge flap performing both primary control and active vibration control was examined. Flap control inputs of a swashplateless rotor are presented at several advance ratios. With optimal selection of blade collective pitch index angle, the flap was shown to be able to trim the rotor with moderate flap inputs. Simulations of flaps performing both primary control and active vibration control were carried out, with the conclusion that trailing-edge flaps are capable of trimming the rotor and minimizing vibratory rotor hub loads simultaneously

Swashplateless Helicopter Rotor System with Trailing-Edge Flaps for Flight and Vibration Controls

The objective of this study is to demonstrate the concept of active trailing-edge flaps as primary flight control and vibration reduction devices for a typical full-scale helicopter. A comprehensive rotorcraft analysis based on UMARC was developed to analyze the swashplateless rotor. A parametric study of various key design variables involved in the trailing-edge flap design was carried out. An optimal design of a trailing-edge flap system that provides effective control authority within the complete range of advance ratios as well as minimum actuation requirements was achieved. Trailing-edge flaps demonstrated the capability of performing both primary flight control and active vibration control functions. At a high forward speed (advance ratio of 0.32), the 4/rev vertical force and roll and pitch moments at hub are successfully eliminated (by 90%), and the 4/rev in-plane hub forces are reduced by more than 40%. The half peak-to-peak value of the trailing-edge flap deflection for primary flight control is 7.1 deg, and an additional 4.7 deg is required for active vibration control.

Aeroelastic Modeling of Trailing-Edge-Flap Helicopter Rotors Including Actuator Dynamics

The effect of actuator dynamics on a helicopter rotor with trailing-edge flaps for vibration control is investigated. Trailing-edge flap, actuator, and elastic rotor blade equations of motion are formulated using Hamilton’s variational principle. The coupled nonlinear, periodic equations are solved using finite elements in space and time. The baseline correlation study is based on wind-tunnel test data for a typical five-bladed bearingless rotor system. Good agreement is seen for the blade flap bending, chord bending, and torsion moments. It is shown that actuator dynamics cannot be neglected for a trailing-edge flap system with torsionally soft actuators. The parametric study performed using both coupled flap/actuator model and prescribed flap motion model indicated that the placement of trailing-edge flaps at 78% radius resulted in minimum flap input for this rotor. The vibration reduction level and trend are close between the predictions of both models at different forward speeds. Control inputs predicted by the coupled model show less sensitivity to the forward speed than that of prescribed model.

Swashplateless Helicopter Rotor System with Active Trailing-Edge Flaps for Primary and Vibration Controls

The objective of this study is to demonstrate the concept of active trailing-edge flaps as primary rotor control and vibration reduction devices for a typical full-scale helicopter. A comprehensive rotorcraft analysis based on UMARC is developed to obtain the results for the swashplateless rotor. A parametric study of various key design variables involved in the trailing-edge flap design was carried out. An optimal design of trailing-edge flap system that provides effective control authority within the complete flight envelope as well as minimum actuation requirements was achieved. Trailing-edge flaps demonstrated the capability of performing both primary control and active vibration control functions. At a high forward speed (advance ratio of 0.32), the 4/rev vertical force, and roll and pitch moments at hub are successfully eliminated (by about 90%), and the 4/rev in-plane hub forces are reduced by more than 40%. The half peak-to-peak value of the trailing-edge flap deflection for primary control is about 7.1 ‐ and additional 4.7 ‐ is required for active vibration control.

Actuation Requirements for a Swashplateless Helicopter Control System

A helicopter primary control system with smart trailing-edge flaps was investigated numerically for its potential to replace a conventional swashplate system. Eliminating the swashplate and associated control system may lead to significant reductions in weight, drag and cost and an improvement of rotor performance. A comprehensive rotorcraft analysis based on UMARC was developed for analyzing the swashplateless rotor configuration, and was implemented to examine the actuation requirements for rotor primary control with trailing-edge flaps. A multicyclic controller was implemented with the swashplateless rotor analysis, and the feasibility of trailing-edge flap performing both primary control and active vibration control was examined. The baseline correlation of rotor control settings and blade sectional moments without trailing-edge flaps was carried out successfully with wind tunnel test data for a typical 5-bladed bearingless rotor system. Calculations of blade torsional moments and blade tip pitch, as well as trailing-edge flap hinge moments, were compared satisfactorily with predictions from CAMRAD II with an active trailing-edge flap input. Flap control inputs of a swashplateless rotor are presented at several advance ratios. With optimal selection of blade collective pitch index angle, the flap was shown to be able to trim the rotor with moderate flap inputs. Simulations of flaps performing both primary control and active vibration control were carried out, with the conclusion that trailing-edge flaps are capable of