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Dynamic Modelling of Multiple Quadrotor Suspended Load Transporting System with Variable Center of Mass via Flexible Cables

Latifi, Alireza | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51106 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Saghafi, Fariborz
  7. Abstract:
  8. Using unmanned aerial vehicles in aerial payload carrying leads many changes requiring significant study and research. In recent years, there has been considerable maturation in Micro Aerial Vehicles (MAV) developement especially quadcopters. In addition to the endurance restriction, considerations on volume and weight that can be carried, and safety issues are also obstacles to the development of unmanned aerial payload carrying in urban environments. One of the ways to make a quadcopter more agile while carrying a load is to hang the cargo from the quadcopter via a cable. In this way, it is possible that quadcopters carry the cargo in a cooperative way, which if properly arranged, increases the safety. It also makes cargo swings to be better controlled. In the modeling of the systems studied, physical characteristics of the cargo, such as c.g. changes, flexibility and mass of the cable, are not taken into account. While the physical characteristics of the cargo and the cable affect the system behavior. In this thesis, the dynamics of the system is comprised of several (arbitrary) quadcopters, which are carrying a cargo via a flexible cable, considering cargo c.g. variations. Modeling is carried out through the Lagrangian equations, using new variations that make it possible to work with Lagrange equations as a tensor. Aerodynamic forces are neglected in modeling. In order to better control cargo swings, cables are attached to the cargo at different points. Changing the center of mass of the cargo is modeled by changing the load within the rigid container. Load is constrained to move in the bottom of the container. The flexible cable is modeled as a chain of attached rigid links, and the cable mass is modeled as point masses at the bottom of the links. Results were verified via standard tests. Finally, effects of flexibility and cable weight on system behavior were studied in the condition that one quadcopter carries a cargo. Results show a 5 to 18 percent increment of the frequency of cargo swings
  9. Keywords:
  10. Lagrangian Method ; Dynamic Modeling ; Flexible Cable ; Aerial Vehicles ; Unmanned Aerial Vehicles (UAV) ; Suspended Load ; Mass Load with Variable Center

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