Control of redundant mechanical systems in the presence of external disturbances

Finished: 2022-07-08

BSc assignment

Background

The control of aerial manipulators outdoor is still challenging especially in the presence of external disturbance forces generated by wind gusts.
A typical goal is that of controlling the robot to perform accurate tracking of its end-effector. If the aerial manipulator is redundant, i.e., the number of control inputs is greater than the dimension of the task, the additional control inputs can be exploited so to find an optimal solution that, e.g., minimizes the overall control effort.

Project Description

This assignment focuses on a simplified linear system with the aim of gaining some insights that may be useful also to the more complex aerial manipulation system. The considered system is composed of two moving masses connected by elastic and damping elements. One of the two masses is considerably greater than the other and represents the aerial robot body, while the smallest one represents its end-effector. While an external force acts on the greatest mass (under the hypothesis that it is bigger and offers greater resistance to the wind), the goal is that of accurately controlling the small mass while minimizing the control effort.

The assignment includes:

  • writing the dynamic model of the system
  • applying LQR control techniques in extensive numerical tests to gain insights on the effect of changing gains.
  • investigating the role of different stiffness and damping parameters.
  • possibly, in a second phase, introducing constraints on the position of the greater mass to model joint limit constraints of the real robot.