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RESEARCH PAPERS

Dynamics and Control of a Helicopter Carrying a Payload Using a Cable-Suspended Robot

[+] Author and Article Information
So-Ryeok Oh

Mechanical System Laboratory, Department of Mechanical Engineering, University of Delaware, Newark, DE 19716-3140oh@me.udel.edu

Ji-Chul Ryu

Mechanical System Laboratory, Department of Mechanical Engineering, University of Delaware, Newark, DE 19716-3140ryu@me.udel.edu

Sunil K. Agrawal

Mechanical System Laboratory, Department of Mechanical Engineering, University of Delaware, Newark, DE 19716-3140agrawal@me.udel.edu

J. Mech. Des 128(5), 1113-1121 (Dec 02, 2005) (9 pages) doi:10.1115/1.2218882 History: Received May 12, 2005; Revised December 02, 2005

In this paper we present a study of the dynamics and control of a helicopter carrying a payload through a cable-suspended robot. The helicopter can perform gross motion, while the cable suspended robot underneath the helicopter can modulate a platform in position and orientation. Due to the underactuated nature of the helicopter, the operation of this dual system consisting of the helicopter and the cable robot is challenging. We propose here a two time scale control method, which makes it possible to control the helicopter and the cable robot independently. In addition, this method provides an effective estimation on the bound of the motion of the helicopter. Therefore, even in the case where the helicopter motion is unknown, the cable robot can be stabilized by implementing a robust controller. Simulation results of the dual system show that the proposed control approach is effective for such a helicopter-robot system.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

A helicopter operation for a ship replenishment in midsea

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Figure 2

A schematic of Helicopter Dynamics

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Figure 3

A geometric model of the helicopter: the helicopter frame OA, the end-effector frame OB, and the inertial frame N

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Figure 4

A sketch of a cable system along with geometric parameters

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Figure 5

Time scale separation based outer-loop and inner-loop autopilot structure

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Figure 6

The Cartesian states’ and the Euler angles’ time trajectory. In the first figure, the outer loop controller is designed to move the helicopter from the initial postion (x,y,z)0=(0,0,0) to the destination (x,y,z)r=(0,0,0.3). In the second figure, the attitude command is computed by the outer loop controller every 0.2second to which the attitude of the helicopter converes. This is achieved by using high control gain Kω.

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Figure 7

The control inputs. These values are computed by solving a set of algrebraic equations, Eqs. 25,30 at each sampling time.

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Figure 8

State and input trajectories of the cable robot. In the first figure, the target’s motion is prescribed as a square signal with its amplitude 0.2(m) and frequency 0.2(Hz). The end effector starting from 1.9(m) tracks the desired signal, showing the settling time 1.5(s). States are updated every 0.2s to which the attitude of the helicopter converges. In the second figure, the cable tensions denoted by T1,T2,…,T6 are control inputs to the cable robot. These values are computed by solving Eq. 37. The stability of the cable robot subject to the unknown motion of the helicopter is achieved by using a fixed gain k in Eq. 40.

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