Synthesis and Control of a 3 Degrees of Freedom Inherently Dynamically Balanced Manipulator for an Unmanned Aerial Vehicle

Abstract

In aerial manipulation, Unmanned Aerial Vehicles (UAVs) are equipped with manipulators to perform a variety of tasks such as inspections of critical infrastructure at heights. A fundamental issue is that the shaking forces and moments of the manipulator cause the UAV to tip-over and become unstable. Control based methods have been applied in which the UAV provided a compensation force or moment at the propellers. However, the dynamic model required was too complex to compute on-board in real time and simplifications led to poor performance. This thesis resolves the issue of shaking forces and moments by creating a new manipulator using inherent dynamic balancing principles. The advantage of these principles is that the manipulator architecture achieves both functions of supporting and positioning the end effector as well as balancing. This helps to reduce the weight of the manipulator. The result of the synthesis work is a manipulator which is reactionless, lightweight, has 3 degrees of freedom, and is compatible with a UAV. First a manipulator is designed using inherently force balanced architectures. Next, active moment balancing is developed through a novel control scheme. Finally, a simulation is performed to prove the dynamic balancing and control method. It shows the manipulator is reactionless. However, the control scheme’s tracking still needs improvement. This work is useful to enable UAVs with manipulators to perform a variety of tasks such as inspections of surfaces at height.