1. Melak Zebenay > EPOS- A Robotics-Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30, 2010 Slide 1 Control Strategy of Hardware-in-the-Loop Simulator EPOS 2.0 for Autonomous Docking Verification M. Zebenay, T. Boge, R. Lampariello, R. Krenn German Aerospace Center (DLR)

2. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 2 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Content EPOS- European Proximity Operation Simulator facility Docking simulation Concept Control Strategy 1-DOF Docking Modeling Target Impedance parameter Identification Results Conclusion and future work

3. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 3 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide EPOS 2.0 -European Proximity Operation Simulator What is EPOS ? Laboratory simulation of spacecraft proximity operations Real-time, real size and real motion simulation Hardware-in-the-loop simulator Why EPOS? Calibrated test bed for proximity operations on RVD missions quantitative performance tests on equipment level Verification and validation on equipment level verification and validation on system level

4. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 4 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide EPOS 2.0 -European Proximity Operation Simulator EPOS 2.0 Performance data: Motion Ranges: Range:25 m Roll/Pitch/Yaw:360 deg Commanding frequency:250 Hz Natural frequency :8-10Hz Max, Payload:up to 200 kg Position accuracy (3D/3  ) :1.56mm Orientation accuracy (3D/3  ) :0.20deg Coming new feature of EPOS 2.0 : Online measurement system which measures relative position Commands corrections to the robots

5. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 5 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Docking simulation Concept The goal of docking simulation capability: Satellite simulator shall accept the measured force/torque and simulate the corresponding dynamic response of the two satellites EPOS 2.0 facility maneuver the docking hardware to follow the output motion data of the satellite simulator EPOS 2.0 facility shall have the same impedance (or passivity) as the simulated satellites Advanced robotics control is suggested to fulfill above requirements

6. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 6 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Docking simulation Concept Schematic of EPOS facility control architecture :

7. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 7 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Control Strategies (1/2) Control challenges and solution strategies: System time delay problem What: Robot does not physically respond to a command immediately Why:Intrinsic for the industrial robots (not a problem for their industrial applications) Consequence: Unstable simulation process Solution: Energy-based simulation process control

8. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 8 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Control Strategies (2/2) Control challenges and solution strategies: Impedance mismatching problem What: Contact impedance of EPOS does not match that of satellite Why: docking hardware is constrained to the ground via the robot - the active robot will interacts with the docking process Consequence: Simulated docking behavior is inaccurate Solution: Impedance/admittance robot control strategy

9. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 9 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 1-DOF Docking Modeling (1/3) Ideal Satellite 1-DOF docking (contact) modeling 1-DOF Modeling of Satellite Docking using Spring-dashpot contact dynamics model of the contact force

10. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 10 1-DOF Docking Modeling (2/3) Docking conditions using EPOS 2.0

11. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 11 1-DOF Docking Modeling (3/3) Requirements: The approximated docking simulation shall have the same dynamic behavior like the real satellite docking model. Therefore it is required to have the same : Final position and velocity after impact Impact force/torque Contact duration

12. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 12 Target Impedance parameter Identification (1/2) Dynamic equation of the target Impedance model:

13. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 13 Target Impedance parameter Identification (2/2) Determining the unknowns k1, b1, k2,b2 assuming m1=M1 and m2=M2: Computing states t=t1 and t=t2 where t1 and t2 is less than the contact duration.

14. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 14 Results Given M1=750kg, M2=1050Kg, k=500000, b=30 v1(0)=0.3, v2(0)=0 kc=30000, bc=0 Assumed:M1=m1, M2=m1 Unknowns: k1, b1, k2 and b2 Results: k1=8.0571e+005 b1=51.4286 k2=1.1280e+006; b2=72.0

15. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 15 Results Position and velocity comparison between the ideal satellite and chaser satellite impedance model after contact

16. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 16 Results Position and velocity comparison between the ideal satellite and target satellite impedance model after contact

17. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 17 Conclusion and future work Experiment using EPOS 2.0 to investigate the contact duration and contact force using different stiffness material. Testing the target impedance using EPOS 2.0 is in progress Extend the target impedance identification method for 3-DOF Implement the control algorithm using the computed target impedance

18. Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide 18 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Slide Thank You!