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Propeller Based Robots
Published in Ferat Sahin, Pushkin Kachroo, Practical and Experimental Robotics, 2017
When the main rotor rotates, it creates a torque on the entire helicopter. To prevent the helicopter from spinning due to that torque, the tail rotor is used that provides a counter torque to balance the rotating torque. If we need to create a yaw motion of the helicopter, we can change the thrust from the tail rotor. This is shown in Figure 10.33 below. A gyroscope is used to sense the rotation, so that it can be balanced by counter-torque. Without a gyro, the RC helicopter might spin out of control.
UAS Airframe Design
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
Michael T. Most, Michael Stroup
Torque effect is present in both fixed-wing and rotary-wing designs, but much more dominant in the latter. Torque effect develops as the result of Newton’s 3rd law, “for every action there is an equal and opposite reaction.” Power delivered to the rotor causes the fuselage to display the propensity to rotate in the direction opposite the rotor. This tendency varies linearly,—increase power, increase torque effect. Torque effect is countered on single-rotor helicopters, both manned and unmanned, by the tail rotor (aka, antitorque rotor). If the thrust produced by the tail rotor is less than torque effect, the fuselage will yaw in the direction opposite main rotor blade rotation; if thrust produced by the antitorque rotor is greater than the torque effect force, the fuselage will yaw in the direction of main rotor rotation. Using two rotors affords the advantage of torque cancellation, whereby the two rotor systems rotate in opposite directions and thus the torque of one cancels that of the other and no other antitorque system (e.g., a tail rotor) is necessary. Examples of UASs with two main rotor systems include both coaxial, contra-rotating, and tandem, counterrotating designs. The difference is that in the former example, the blades rotate around a common axis, while in the latter, rotation occurs about two independent axes. The first rotary-wing UAS, the QH-50 DASH, developed by Gyrodyne for the Navy in the late 1950s and early 1960s, was a coaxial, contrarotating design powered by a Boeing turboshaft producing 300 shaft horsepower. During the late 1980s and early 1990s, Sikorsky experimented with a coaxial unmanned design known as the Cipher and Cipher II, which subsequently evolved into the USMC’s Dragon Warrior UAS. Currently produced examples of a tandem, counterrotating UAS rotor system may be found on the unmanned version of the Kaman K-MAX, a helicopter capable of lifting an external load equal to its own weight, and the IAI Ghost, which resembles a Chinook manned helicopter in configuration. The K-MAX rotor system, wherein the blades mesh, much like those of an old-fashioned, mechanical egg beater, is also referred to as a synchropter or intermeshing rotor design.
Hybrid composite shaft of High-Speed Rotor-Bearing System - A rotor dynamics preview
Published in Mechanics Based Design of Structures and Machines, 2021
Thimothy Harold Gonsalves, Mohan Kumar Garje Channabasappa, Ramesh Motagondanahalli Rangarasaiah
Composite material has been one of the most researched materials in the last two to three decades for its excellent material properties. The potential use of composite material in the automotive and helicopter tail rotor drive shafts are established based on the extensive theoretical and experimental investigations. The prominent investigations of Zinberg and Symonds (1970), Singh and Gupta (1996), Hajianmaleki and Qatu (2012) and others used equivalent modulus beam theory (EMBT), layer-wise beam theory (LBT), first order shear deformation beam theory (FSDBT), etc., to perform the dynamic study of rotating composite shaft. The results of these investigations facilitated many automotive drive shaft and rotorcraft tail rotor shaft applications to use composite material to increase the shaft bending stiffness to push the bending natural frequency above the operating speeds.
Quadrotor Attitude Dynamics Identification Based on Nonlinear Autoregressive Neural Network with Exogenous Inputs
Published in Applied Artificial Intelligence, 2021
Alexander Avdeev, Khaled Assaleh, Mohammad A. Jaradat
A quadrotor is comprised of a thin cross structure with four propellers at its ends. Unlike a helicopter, the quadrotor does not require a tail rotor, due to the four-propeller cross configuration. Front and rear propellers rotate in a clockwise direction, while right and left propellers spin in the opposite (counter-clockwise) direction. Control of a quadrotor is performed by changing the rotation rate and thus the thrust of each rotor individually. Although control is achieved through changing rotation rates of individual motors, this approach is very counterintuitive for humans. Due to this reason, four so-called channels are used, namely throttle, roll, pitch, and yaw.
Fast finite-time backstepping for helicopters under input constraints and perturbations
Published in International Journal of Systems Science, 2020
In (2) and (4), and are the external forces and torque exerted on fuselage in BRF, respectively. The control force and torque of traditional helicopters are dependent on the main rotor , , tail rotor and the flapping angles , . Following the analysis in Mettler (2003) and He et al. (2014), the simplified expression is given as is the control input vector, whose elements denote the collective pitch of the main rotor, longitudinal cyclic, lateral cyclic and collective pitch of the tail rotor, respectively. and represent the lumped force and moment disturbances in BRF, respectively, which caused by the external disturbances, parameter uncertainties and unmodelled dynamics. The constant matrix is expressed as follows (Mettler, 2003): where the coefficients , , , , , , and depend on the helicopter structure. The accurate values of these parameters can be obtained via system identification technique. However, the identification experiments of the rotorcrafts are complicated. Furthermore, the frequent replacements of the configuration of small-scale helicopters may cause the large parameter variations. Thus we need to develop a quick and easy way to design the control system for helicopters with parameter uncertainties and unmodelled dynamics.