Applied Mechanics and Materials Vol. 772

Abstract: In the current paper, seven degrees of freedom multibody model of a monocopter air vehicle is developed based on the Newton-Euler approach along with nonlinear simulation in different flight phases. Aerodynamic forces and moments are modeled using blade element momentum theory. The sole control surface is modeled like a conventional flap on a wing. Free flight simulation is performed in MATLAB Simulink environment to evaluate the behavior of the system and to demonstrate the effectiveness and applicability of the proposed model. Simulation results show harmonic oscillations in Euler angles, linear and angular velocities that are consistent with the physics and mathematical foundations. Static stability of the vehicle is evident in free flight by careful choice of initial conditions. The presented multibody model is useful for comparative study and design purposes.

Abstract: This paper presents a design approach for the automatic flight control system of a launch vehicle using a linear quadratic integral technique together with a fixed gain Kalman filter. Its purpose is to analyse the stability and tracking robustness performances of the control system designed via this approach when atmospheric disturbances, modeling uncertainties and structural flexible modes of the launcher are taken into account.

Abstract: The L₁ Adaptive control technique is applied to the F-18 HARV (High Alpha Research Vehicle) aircraft. This control architecture compensates for both the matched and the unmatched uncertainties of the full nonlinear aircraft dynamics. This paper describes the L₁ control architecture used to control the nonlinear dynamics of the aircraft and the final part presents the detailed simulation results for the lateral channel

Abstract: The missions of small flying wing UAVs require maneuver capabilities as well as optimal flight performance to balance the low operating and manufacturing costs. The basic principles in designing aviation structures must be readjusted due to the innovative concepts regarding the use of advanced materials as well as to the perspectives of using alternative energy aboard UAVs. The current paper is a synthesis of the 2D and 3D aerodynamic analysis of small swept flying wing UAVs that offers a global image of the possibilities of a multidimension optimization (miniaturization-scalability, payload-flexibility, minimum performances requirements).

Abstract: A flapping wing mimicking the Black Headed Gull was developed and tested for its kinematics. All the individual joints in the gull wing, namely the shoulder, elbow and wrist joint were mimicked with their corresponding functionalities. The shoulder joint is designed to control the flapping frequency, flapping amplitude, flapping plane and the speed of the upstroke-downstroke. Similarly, the elbow and wrist joints control the upstroke span reduction and twisting of the wing, respectively. Geometry, inertia, mass and frequency data of the gull were used to model the wing. A control input program was designed for the independent control of all the 6 joints (3 per wing). The motion of the manufactured wing system was verified using LASER Displacement Sensor.

Abstract: Natural flyers are the best source of inspiration for making successful MAVs. Hummingbirds are known for their excellent flight characteristics such as long duration hovering, backward flying, high agility, etc. Giant hummingbird is chosen as the bio-inspiration for designing the wing. Wings are required to be light, strong, and fatigue resistant to be used for MAV applications. Carbon nanotubes (CNTs)/Polypropylene (PP) composite is chosen as the wing membrane material whereas carbon fiber (CF)/epoxy (E) composite is chosen for wing frame. Two types of wings are fabricated, one is CNTs/PP wing and another is CF/E frame with CNTs/PP membrane wing. Kinematics, structural dynamics, and aerodynamics are the main component of flapping flight studies. Modal analysis of fabricated wings is done using 3D visual image correlation (VIC-3D) and laser displacement sensor setup. In the end, the results of both type wings are compared with experimental results and a good correlation has been seen. The validation of results is done using Ansys.

Abstract: This paper describes the application of active flow control for the NLR7301 supercritical airfoil/flap configuration at Re = 2.51x10⁶. A parametric analysis is conducted to investigate the effects of jet parameters (jet direction, jet location and momentum coefficient) on the aerodynamic performance of a multi-element airfoil. The results indicate that flow separation is delayed and efficiency of jet can be improved with specific momentum coefficient (the best lift-drag ratio at C_μ=0.16) and jet angle (16°) when the jet is located near the separation point of the airfoil.

Abstract: Spacecraft, irrespective of their mission’s purpose, contain a number of moving mechanical assemblies such as control moment gyros, momentum/ reaction wheels, gyroscopes, scanners, solar array drives, etc. Most problems encountered with these moving systems are related to tribology and, specifically, lubrication. Lubrication problems result from the loss of lubricant from the working zone by evaporation, surface migration, etc. Therefore, to ensure long-term uninterrupted performance of these systems, an efficient lubricant replenishment system is essential. This article describes various lubricating methods and lubrication systems used for the successful operation of some of these systems for the entire mission periods.

Abstract: One of the most precise method solving the inverse kinematics problem in the redundant cases of the robots is the coupled method. The proposed method use the Iterative Pseudo Inverse Jacobian Matrix Method (IPIJMM) coupled with the proper Sigmoid Bipolar Hyperbolic Tangent Neural Network with Time Delay and Recurrent Links (SBHTNN-TDRL). One precise solution of the inverse kinematics problem is very difficult to find, when the degree of freedom increase and in many cases this is impossible because the redundant solutions. In all these cases must be used the numerical iterative approximation, like the proposed method, with artificial intelligence algorithm. The paper describe all the steps in one case study to obtain the space circle curve in different planes by using one arm type robot and the proposed method. The errors of the space movement of the robot end-effecter, after applying the proposed method, was less than 0,01. The presented method is general and it can be used in all other robots types and for all other conventional and unconventional space curves.

Abstract: The paper focuses on problems of the safety operation of service robots on glass facades of high-rise buildings exposed to a local additional load during the robot motion and any subsequent service operation (e.g. cleaning, diagnostics, mounting). Owing to afraid of a possible glass cracking and a subsequent destruction, the authors pay attention to an analysis of the strength of façade glass sheets being in contact with the robot holding-down vacuum system as well as with the supporting steel construction. With a view of appraising a state of stress, a computer model was build up respecting the real composition of façade glass, material properties and contact edge conditions. The paper presents achieved results by means of graphic outputs, and in conclusion, it discusses them with aim to supply owners of service robots from a sphere of the building administration a number of details.