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Coupled Lateral–Longitudinal Flight Dynamics
Published in Nandan K. Sinha, N. Ananthkrishnan, Advanced Flight Dynamics with Elements of Flight Control, 2017
Nandan K. Sinha, N. Ananthkrishnan
The F-18/HARV data show an order of magnitude difference between the axial and transversal moments of inertia and is therefore prone to inertia-coupling effects in flight. Construct a model for F-18/HARV at a suitable angle of attack in level flight trim to study its roll dynamics using bifurcation analysis technique.Design feedback law for Dutch roll and spiral mode stability augmentation systems.Construct a linear (state-space) model of F-18/HARV trimmed at α = 5 deg in level flight. Design a feedback law for augmenting Dutch roll stability of the aircraft at this trim condition.Using AOA and pitch rate feedback and setting short period mode specifications as that of one of the eigenvalues in Figure 5.8, carry out gain scheduling over the complete range of level flight trim conditions for F-18/HARV.Read about various techniques of gain scheduling.Study the control commands computed in Section 7.5 for each maneuver and discuss the sequence of control inputs as required by a pilot to execute the maneuvers in the absence of a controller. Are they the same?
Multibody system design based on reference dynamic characteristics: gyroscopic system paradigm
Published in Mechanics Based Design of Structures and Machines, 2023
Ayman A. Nada, Abdullatif H. Bishiri
The matrix represents the mass matrix associated with the translational coordinates of the body reference, each diagonal element is equal to the mass of the body (i). The matrix represents the inertia coupling between the rigid body translation and the rigid body rotation, which can be calculated as The matrix is the velocity transformation defined in Eq. (4) and is the skew-symmetric matrix of the first moment of mass of the body. The matrix is associated with the rotational coordinates of the body reference and can be calculated as where is the inertia tensor of the body.
Linear stability analysis of a high-speed rail vehicle concerning suspension parameters variation and active control
Published in Vehicle System Dynamics, 2022
Huailong Shi, Jing Zeng, Sheng Qu
Figure 1 illustrates the simplified lateral dynamic model of a high-speed rail vehicle. It consists of one carbody and two bogies, and each bogie consists of one frame and two wheelsets. This commonly used vehicle model has 17 DOFs in total. The primary suspension consists of springs in parallel with viscous dashpots. Besides springs, the secondary suspension also contains yaw dampers and lateral dampers, represented by a Maxwell model (a spring in series with a viscous dashpot). The wheelset bears the wheel/rail contact forces, primary suspension forces, and gravity. The bogie frame and carbody bear the suspension forces and gravity. The multibody vehicle system is reduced to vibration equations by replacing the constraints equations with force elements and ignoring the inertia coupling items. The appendix notates the vehicle parameters.
Deformation basis and kinematic singularities of constrained systems
Published in Mechanics Based Design of Structures and Machines, 2019
Emanuele Grossi, Ahmed A. Shabana
In the FFR formulation, the deformation basis vectors are defined using the reference conditions, which are also used to eliminate the rigid body modes of the FE shape function matrix. Although some of these deformation basis vectors may have insignificant effect on the solution, such insignificant modes can be effectively used to eliminate the initial-configuration singularity, as it will be demonstrated in this investigation. An FFR multi-degree-of-freedom semianalytical dynamic model was developed to shed light on the important concept of the FE/FFR reference conditions and on the simplifications in the inertia shape integrals that result from using the mean-axis reference conditions (Shabana, Wang, and Kulkarni 2018). It was demonstrated that imposing the mean-axis reference conditions results in a weak inertia coupling between the reference and the elastic displacements because several inertia shape integrals are identically equal to zero. Using the semianalytical slider-crank mechanism model, it was shown that by not properly accounting for all the inertia shape integrals in the FE/FFR analysis, a nonphysical zero deformation response is obtained regardless of the crankshaft angular velocity, even if an appropriate set of reference conditions is used.