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Cooperative Transportation using Multiple Single-Rotor Robots and Decentralized Control for Unknown Payloads

Koshi Oishi, Yasushi Amano, Tomohiko Jimbo

TL;DR

This work tackles cooperative transportation with rigidly connected payloads by multiple aerial robots under unknown payloads and potential failures. It develops a decentralized control framework that first renders the unstable multi-output dynamics SPR via a robust feedback path and shared attachment positions, then extends the autonomous smooth switching controller (ASSC) to four outputs to guarantee asymptotic stability. Stability conditions are derived using LMIs to ensure SPR across uncertain mass $m$, attachment positions $m{r}$, and failure indicators $m{\sigma}$, without requiring COM estimation. The approach is validated through simulations with rectangular and L-shaped payloads and demonstrated on a hardware prototype carrying an unknown payload larger than the robots, including scenarios with a failed robot; results show robust payload stabilization and accurate trajectory tracking, though full decentralization without attachment sharing requires further theoretical guarantees.

Abstract

Cooperative transportation via multiple aerial robots has the potential to support various payloads and reduce the chances of them being dropped. Furthermore, autonomously controlled robots render the system scalable with respect to the payload. In this study, a cooperative transportation system was developed using rigidly attached single-rotor robots, and a decentralized controller was proposed to guarantee asymptotic stability of the error dynamics for unknown strictly positive real systems. A feedback controller was used to transform unstable systems into strictly positive real ones considering the shared attachment positions. First, the cooperative transportation of unknown payloads with different shapes larger than the carrier robots was investigated via numerical simulations. Second, cooperative transportation of an unknown payload (with a weight of approximately 2.7 kg and maximum length of 1.6 m) was demonstrated using eight robots, even under robot failure. Finally, the proposed system was shown to be capable of carrying an unknown payload, even if the attachment positions were not shared, that is, even if asymptotic stability was not strictly guaranteed.

Cooperative Transportation using Multiple Single-Rotor Robots and Decentralized Control for Unknown Payloads

TL;DR

This work tackles cooperative transportation with rigidly connected payloads by multiple aerial robots under unknown payloads and potential failures. It develops a decentralized control framework that first renders the unstable multi-output dynamics SPR via a robust feedback path and shared attachment positions, then extends the autonomous smooth switching controller (ASSC) to four outputs to guarantee asymptotic stability. Stability conditions are derived using LMIs to ensure SPR across uncertain mass , attachment positions , and failure indicators , without requiring COM estimation. The approach is validated through simulations with rectangular and L-shaped payloads and demonstrated on a hardware prototype carrying an unknown payload larger than the robots, including scenarios with a failed robot; results show robust payload stabilization and accurate trajectory tracking, though full decentralization without attachment sharing requires further theoretical guarantees.

Abstract

Cooperative transportation via multiple aerial robots has the potential to support various payloads and reduce the chances of them being dropped. Furthermore, autonomously controlled robots render the system scalable with respect to the payload. In this study, a cooperative transportation system was developed using rigidly attached single-rotor robots, and a decentralized controller was proposed to guarantee asymptotic stability of the error dynamics for unknown strictly positive real systems. A feedback controller was used to transform unstable systems into strictly positive real ones considering the shared attachment positions. First, the cooperative transportation of unknown payloads with different shapes larger than the carrier robots was investigated via numerical simulations. Second, cooperative transportation of an unknown payload (with a weight of approximately 2.7 kg and maximum length of 1.6 m) was demonstrated using eight robots, even under robot failure. Finally, the proposed system was shown to be capable of carrying an unknown payload, even if the attachment positions were not shared, that is, even if asymptotic stability was not strictly guaranteed.

Paper Structure

This paper contains 14 sections, 1 theorem, 12 equations, 19 figures.

Table of Contents

  1. INTRODUCTION
  2. DYNAMICS
  3. DECENTRALIZED CONTROL
  4. Robust feedback controller
  5. ASSC for multiple-output systems
  6. Decentralized control system
  7. SIMULATION
  8. Condition
  9. Results
  10. EXPERIMENT
  11. Prototype
  12. Condition
  13. Results
  14. CONCLUSIONS

Key Result

Theorem III.1

Eq. (eq:st2) is assumed to be transformed into a SPR system by $\bm{U_f}.$ Using the ASSC of eq. (eq:cont), the error $\bm{\eta}$ satisfies $\bm{\eta} \rightarrow \bm{0}$ as $t \rightarrow \infty$.

Figures (19)

  • Figure 1: Rigidly connected robots to a payload
  • Figure 2: Decentralized controlled flight
  • Figure 4: Model of transportation system with multiple rigidly connected robots
  • Figure 5: Switching function $\delta (\varphi_i)$
  • Figure 6: Proposed decentralized control system
  • ...and 14 more figures

Theorems & Definitions (2)

  • Theorem III.1
  • proof