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Observer-based Controller Design for Oscillation Damping of a Novel Suspended Underactuated Aerial Platform

Hemjyoti Das, Minh Nhat Vu, Tobias Egle, Christian Ott

TL;DR

This work addresses energy-efficient damping of oscillations in a cable-suspended aerial platform modeled as a spherical double pendulum. It combines an onboard IMU–based extended Kalman filter with two control strategies: an optimal state-feedback LQR and a PD+ task-space controller, applied to three platform variants (omnidirectional, planar-thrust, and minimal-actuated). The underactuated designs achieve damping with reduced actuator count and lower energy consumption, demonstrated through numerical simulations and outdoor experiments, including energy reductions of $50.9\%$ and $52.8\%$ for planar-thrust and minimal-actuated platforms relative to the omnidirectional baseline. The results indicate practical benefits for energy-efficient aerial manipulation, with future work including manipulation tasks, additional sensing, and learning-based disturbance rejection.

Abstract

In this work, we present a novel actuation strategy for a suspended aerial platform. By utilizing an underactuation approach, we demonstrate the successful oscillation damping of the proposed platform, modeled as a spherical double pendulum. A state estimator is designed in order to obtain the deflection angles of the platform, which uses only onboard IMU measurements. The state estimator is an extended Kalman filter (EKF) with intermittent measurements obtained at different frequencies. An optimal state feedback controller and a PD+ controller are designed in order to dampen the oscillations of the platform in the joint space and task space respectively. The proposed underactuated platform is found to be more energy-efficient than an omnidirectional platform and requires fewer actuators. The effectiveness of our proposed system is validated using both simulations and experimental studies.

Observer-based Controller Design for Oscillation Damping of a Novel Suspended Underactuated Aerial Platform

TL;DR

This work addresses energy-efficient damping of oscillations in a cable-suspended aerial platform modeled as a spherical double pendulum. It combines an onboard IMU–based extended Kalman filter with two control strategies: an optimal state-feedback LQR and a PD+ task-space controller, applied to three platform variants (omnidirectional, planar-thrust, and minimal-actuated). The underactuated designs achieve damping with reduced actuator count and lower energy consumption, demonstrated through numerical simulations and outdoor experiments, including energy reductions of and for planar-thrust and minimal-actuated platforms relative to the omnidirectional baseline. The results indicate practical benefits for energy-efficient aerial manipulation, with future work including manipulation tasks, additional sensing, and learning-based disturbance rejection.

Abstract

In this work, we present a novel actuation strategy for a suspended aerial platform. By utilizing an underactuation approach, we demonstrate the successful oscillation damping of the proposed platform, modeled as a spherical double pendulum. A state estimator is designed in order to obtain the deflection angles of the platform, which uses only onboard IMU measurements. The state estimator is an extended Kalman filter (EKF) with intermittent measurements obtained at different frequencies. An optimal state feedback controller and a PD+ controller are designed in order to dampen the oscillations of the platform in the joint space and task space respectively. The proposed underactuated platform is found to be more energy-efficient than an omnidirectional platform and requires fewer actuators. The effectiveness of our proposed system is validated using both simulations and experimental studies.
Paper Structure (16 sections, 22 equations, 11 figures)

This paper contains 16 sections, 22 equations, 11 figures.

Table of Contents

  1. Introduction
  2. System Overview and Modelling
  3. System Dynamics
  4. Omnidirectional Platform
  5. Planar-thrust Platform
  6. Minimial-Actuated Platform
  7. Observer Design
  8. Controller Design
  9. Linear Quadratic Regulator (LQR)
  10. PD+ Controller
  11. Omnidirectional Platform
  12. Planar-thrust and Minimial-actuated Plaforms
  13. Results
  14. Numerical Simulations
  15. Experimental Results
  16. ...and 1 more sections

Figures (11)

  • Figure 1: Proposed planar-thrust suspended aerial platform.
  • Figure 2: Suspended aerial platform represented as a spherical double pendulum.
  • Figure 3: Top-view of the proposed (a) planar-thrust platform with six rotors and (b) minimal-actuated platform with four rotors. The arrows depict the direction of propulsion, whereas $M_i$ is used to denote the $i^{th}$ motor.
  • Figure 4: Joint-angles for the LQR-controlled system, using the omnidirectional platform (denoted as OD), planar-thrust platform (denoted as PT), and minimum-actuated platform (denoted as MA).
  • Figure 5: Wrenches commanded by the LQR controller.
  • ...and 6 more figures