This paper presents a vision-based relative pose estimation algorithm and its validation through both numerical and hardware experiments. The algorithm and the hardware system were simultaneously designed considering actual experimental conditions. Two estimation techniques were utilized to estimate relative pose; one was a nonlinear least square method for initial estimation, and the other was an extended Kalman Filter for subsequent on-line estimation. A measurement model of the vision sensor and equations of motion including nonlinear perturbations were utilized in the estimation process. Numerical simulations were performed and analyzed for both the autonomous docking and formation flying scenarios. A configuration of LED-based beacons was designed to avoid measurement singularity, and its structural information was implemented in the estimation algorithm. The proposed algorithm was verified again in the experimental environment by using the Autonomous Spacecraft Test Environment for Rendezvous In proXimity (ASTERIX) facility. Additionally, a laser distance meter was added to the estimation algorithm to improve the relative position estimation accuracy. Throughout this study, the performance required for autonomous docking could be presented by confirming the change in estimation accuracy with respect to the level of measurement error. In addition, hardware experiments confirmed the effectiveness of the suggested algorithm and its applicability to actual tasks in the real world.

1. INTRODUCTION
 2. VISION-BASED MEASUREMENT SYSTEM
  2.1 Vision System
  2.2 LED Configuration
  2.3 Image Processing
  2.4 Gyro Sensor
  2.5 Laser Distance Meter
 3. VISION-BASED RELATIVE POSE ESTIMATION
  3.1 Nonlinear Least Squares Method
  3.2 Extended Kalman Filter
  3.3 Dynamic Model
 4. RESULTS
  4.1 Numerical Simulation
  4.2 Hardware Experiment
 5. CONCLUSION
 REFERENCES

• Jeonghoon Hyun(Department of Astronomy, Yonsei University)
• Youngho Eun(Department of Astronomy, Yonsei University)
• Sang-Young Park(Department of Astronomy, Yonsei University) Corresponding Author