A Simplified Model, Dynamic Analysis and Force Estimation for a Large-scale Orinthopter in Forward Flight Based on Fligh
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Journal of Bionic Engineering http://www.springer.com/journal/42235
A Simplified Model, Dynamic Analysis and Force Estimation for a Large-scale Orinthopter in Forward Flight Based on Flight Data Mohammad Ali Amini, Moosa Ayati*, Mohammad Mahjoob School of Mechanical Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran, Iran
Abstract Similarities and differences of a large-scale flapping-wing robot with fixed-wing UAVs in equations of motion, trim curves, and aerodynamic forces in forward flight are discussed in this paper and a simplified model for flapping flight is presented. Due to the high Wing to Total Weight (WTW) ratio of large-scale ornithopters, simple rigid body dynamics is not accurate enough for flight dynamics modeling. On the other hand, the multi-body dynamics associated with flapping gives little insight into the behavior of the resulting model due to complexity of equations. It is also difficult to design proper controllers for such complicated models. In this paper, the effects of different terms of multi-body equations of ornithopter on the estimated aerodynamic forces are studied via experimental flight data. A simpler but yet accurate set of equations is obtained by removing less effective terms from original relations. The presented model is in the form of normal aircraft equations plus some additional terms which can be used in different control and estimation processes. In addition, trim conditions of forward flight are extracted using several flight tests, and corresponding periodic behavior of states and forces are studied. These studies are applicable for identifying time-periodic models. Keywords: flapping wing robot, bionic robot, ornithopter, trim condition analysis, low-order modeling, aerodynamic force estimation Copyright © Jilin University, 2020.
Nomenclature
Ω
mj M ρ
Mass of the jth body (kg) The total mass of the system (kg) Wing to total weight ratio = mwings / M
Ωj
aG j
Acceleration vector of the CG of the jth body (m·s−2) Displacement vector from location B to Location A represented w.r.t main body coordinate (m) Displacement vector from location B to location A represented w.r.t A’s body coordinate (m) Total external force vector acting on the system (N) The total external moment about point o acting on the system (N·m) Transformation matrix from jth body coordinate to main body coordinate Angular rate about x, y and z axes of the main body represented w.r.t main body coordinate (rad·s−1)
rA/B
lA/B
F
To Rj p, q, r
*Corresponding author: Moosa Ayati E-mail: [email protected]
γ γmean u, v, w
V
IG j
Ijxx, Ijyy, Ijzz Ijxz
Angular rate vector of the main body represented w.r.t main body coordinate (rad·s−1) Angular rate vector of the jth body represented w.r.t main body coordinate (rad·s−1) Wing angle (rad) The angle between the middle position of the wings and the horizontal plane of the body. (rad) Velocities of the main body in x, y and z direction of the main body represented w.r.t main body coordinate (m·s−1) The velocity vect
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