Validation of Volumetric Contact Dynamics Models

Transcription

1 Validation of Volumetric Contact Dynamics s February 3, 2010 Validation of Volumetric Contact Dynamics s

2 Outline 1 2 Volumetric model 3 4 Validation of Volumetric Contact Dynamics s

3 Outline 1 2 Volumetric model 3 4 Validation of Volumetric Contact Dynamics s

4 Figure: Dextre at the tip of Canadarm2 [1]. Validation of Volumetric Contact Dynamics s

5 Contact s Electrical Connectors Alignment Sleeve 36" Micro Fixture 28" 12" Coarse Alignment Bumper Point contact models Small contact patches only Simple, convex geometries SPDM OTCM Alignment Pins No rolling resistance, spinning friction torque Battery Battery Worksite FEM Worksite Figure: ISS battery box [1]. Too complex for real-time Validation of Volumetric Contact Dynamics s

6 Contact s Point contact models Small contact patches only Simple, convex geometries No rolling resistance, spinning friction torque Falling ISS battery box: real-time FEM Too complex for real-time Validation of Volumetric Contact Dynamics s

7 Goals 1 Experimentally validate the volumetric contact dynamics model for hard-on-hard (metal) contact 2 Demonstrate parameter identification for the model Validation of Volumetric Contact Dynamics s

8 Outline Volumetric model 1 2 Volumetric model 3 4 Validation of Volumetric Contact Dynamics s

9 Volumetric model Volumetric model f N k v Figure: The modified Winkler elastic foundation model [1]. Validation of Volumetric Contact Dynamics s

10 Volumetric properties Volumetric model Bi Kw s fs,j(s) nj ni fs,i(s) Contact Surface S Contact Plate Bj Figure: The contact surface between two deformable bodies [1]. Volumetric properties V - volume of interference n - contact normal J s - surface-inertia tensor J v - volume-inertia tensor Validation of Volumetric Contact Dynamics s

11 Volumetric model V Normal force f n = k v V (1 + av cn )n n v cn S Validation of Volumetric Contact Dynamics s

12 Rolling resistance Volumetric model V Rolling resistance torque τ r = k v a J s ω t n ω t S Validation of Volumetric Contact Dynamics s

13 Friction Volumetric model f t Friction force τ s Spinning friction torque fn 7-parameter model Bristle stiffness and damping (σ o, σ 1 ) Slip-stick effects (µ S, µ C, v S ) Dwell-time dependency (τ dw ) Viscous damping (σ 2 ) Contact sites Figure: Surface asperities ( bristles ) in contact [1]. Validation of Volumetric Contact Dynamics s

14 The Contensou effect Volumetric model v C ω r C Translational friction forces tend to cancel out as angular velocity increases. v A A ω r ω v ω r B v B D v D ω r Figure: v << ωr [2] Validation of Volumetric Contact Dynamics s

15 The Contensou effect Volumetric model ω r v C C ω r Translational friction forces tend to cancel out as angular velocity increases. ω r v A A ω v ω r B v B D v D Figure: v >> ωr [2] Validation of Volumetric Contact Dynamics s

16 The Contensou effect Volumetric model ω r v C C ω r Translational friction forces tend to cancel out as angular velocity increases. ω r v A A ω v ω r B v B D v D Figure: v ωr [2] Validation of Volumetric Contact Dynamics s

17 Volumetric contact model Volumetric model Ball-table simulation: real-time Validation of Volumetric Contact Dynamics s

18 Outline 1 2 Volumetric model 3 4 Validation of Volumetric Contact Dynamics s

19 Contact geometries Focus on simple geometric pairs: Cylinder-on-plane Validation of Volumetric Contact Dynamics s

20 Contact geometries Focus on simple geometric pairs: Cylinder-on-plane Sphere-on-plane Validation of Volumetric Contact Dynamics s

21 Normal force experiments Volumetric stiffness Increase force on payload quasi-statically Measure normal forces and displacements (to calculate volume of interference) f N = k v V Validation of Volumetric Contact Dynamics s

22 Normal force experiments Volumetric stiffness Increase force on payload quasi-statically Measure normal forces and displacements (to calculate volume of interference) Damping f N = k v V (1 + av cn ) Drive the payload into contact plate at set velocities Measure forces and displacements over time Validation of Volumetric Contact Dynamics s

23 Translation Static friction and bristle dynamics 1 Begin with payload at rest 2 Slowly increase force until slipping occurs Peak force can be used to estimate µ S : f t f µ N S t Also, σ o = µ S δz Validation of Volumetric Contact Dynamics s

24 Translation Coulomb friction and viscous damping Drive payload at different constant velocities f t f σ N 2 f µ N C f t f n (µ C + σ 2 v t ) v t Validation of Volumetric Contact Dynamics s

25 Translation Dwell-time dependency τ dw t peak t stop ln( µ S µ C µ S µ peak ) Static friction: Bonds between surfaces form over time when at rest. 1 Drive payload at a constant velocity 2 Bring to a stop for a set period of time 3 Slowly increase force until slipping occurs 4 Repeat, increasing the dwell time, until no change in peak force detected between iterations Validation of Volumetric Contact Dynamics s

26 Rotation Repeat translation experiments, rotating instead of translating Compare parameters for translation and rotation Validation of Volumetric Contact Dynamics s

27 Combined translation and rotation Contensou effect 1 Drive at constant tangential velocity with increasing angular velocity 2 Drive at constant angular velocity with increasing tangential velocity 3 Using parameters identified in previous experiments, model the friction forces to compare with observed Contensou effect Validation of Volumetric Contact Dynamics s

28 Normal force configuration Validation of Volumetric Contact Dynamics s

29 Friction configuration Validation of Volumetric Contact Dynamics s

30 Apparatus Validation of Volumetric Contact Dynamics s

31 Outline 1 2 Volumetric model 3 4 Validation of Volumetric Contact Dynamics s

32 Volumetric contact dynamics model discussed Experimental procedure developed for parameter identification and validation Design of experimental apparatus Validation of Volumetric Contact Dynamics s

33 References Y. Gonthier. Contact Dynamics ling for Robotic Task Simulation. PhD Thesis, University of Waterloo, Y. Gonthier, J. McPhee, C. Lange. On the Implementation of Coulomb Friction in a Volumetric-Based for Contact Dynamics. Proceedings of IDETC 07, Validation of Volumetric Contact Dynamics s

34 Research supported by Validation of Volumetric Contact Dynamics s

35 Questions Validation of Volumetric Contact Dynamics s