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Control Strategy of Hardware-in-the-Loop Simulator EPOS 2.0 for Autonomous Docking Verification

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). Content. EPOS- European Proximity Operation Simulator facility Docking simulation Concept Control Strategy

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Control Strategy of Hardware-in-the-Loop Simulator EPOS 2.0 for Autonomous Docking Verification

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

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

  4. 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/3s) : 1.56mm • Orientation accuracy (3D/3s) : 0.20deg • Coming new feature of EPOS 2.0 : • Online measurement system which measures relative position • Commands corrections to the robots Slide Slide Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010 Melak Zebenay >EPOS-A Robotics- Based Hardware in-the-Loop Simulator for Simulating Satellite RvD Operations >Aug 30,2010

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

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

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

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

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

  10. 1-DOF Docking Modeling (2/3) • Docking conditions using EPOS 2.0

  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. Target Impedance parameter Identification (1/2) • Dynamic equation of the target Impedance model:

  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. 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. Results • Position and velocity comparison between the ideal satellite and chaser satellite impedance model after contact

  16. Results • Position and velocity comparison between the ideal satellite and target satellite impedance model after contact

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

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