Improving autonomous orchard vehicle trajectory tracking performance via slippage compensation

Transcription

1 Improving autonomous orchard vehicle trajectory tracking performance via slippage compensation Dr. Gokhan BAYAR Mechanical Engineering Department of Bulent Ecevit University Zonguldak, Turkey This study was conducted under the Supervision of Dr. Marcel Bergerman in the Field Robotics Center of Robotics Institute of Carnegie Mellon University, Pittsburgh, PA, USA.

2 Objective of the Research Development of a slippage estimation procedure and performing a desired trajectory tracking control. 1

3 a single set of controller parameters or a unique equation of motion to guarantee a desired performance and accuracy Due to changing the characteristics Of wheel-ground interaction 2

4 the simple assumptions which are generally used in the mobile robot / autonomous vehicle applications: ideal transmission ideal rolling no slippage no lost of traction control no external wheel forces no surface change behavior no disturbance, etc. 3

5 Desired task [f(x,y,t)] [f(x,y)] Vehicle Model Controller Forward Velocity Steering Angle <Mobile Robot> Unmanned Ground Vehicle x,y,θ,v,δ Wheel-Ground Interaction Surface Information 4

6 Trajectory Tracking Control of an Autonomous Vehicle X Error (t)= X Desired (t) - X Actual (t) Y Error (t)= Y Desired (t) - Y Actual (t) θ Error (t)= θ Desired (t) - θ Actual (t) f(x,y,t) desired Vehicle desired (t) Vehicle actual (t) Y f(x,y,t) actual X 5

7 Desired Trajectory Generator Dynamic approaches Kinematic/Car like robot approach Point mass model Dubins curves 6

8 Car like robot model 7

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10 Desired trajectory tracking controller X desired + - X PS Σ X e Controller V c Vehicle V Φ x, y Φ c Y desired + Σ Y e V Φ - Y PS θ desired + Σ θ e - θ PS 9

11 Lyapunov Functions 10

12 Working Environment of an Orchard Robot Vehicle w 1 trees w 2 11

13 Reference Trajectory

14 Turning Geometry 13

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16 Experimental Orchard 15

17 1. Experiments to test the behaviour of the proposed model Slippage information is not taken into consideration. RTK-GPS is used for position feedback. 16

18 4 km autonomous drive achieved in the orchard 17

19 Desired and actual steering angles for 4 km autonomous drive 18

20 Video 19

21 2. Experiments to test the behaviour of the proposed model. Slippage information is not taken into consideration. Row Detection System (via Laser Scanning RangeFinder) is used. 20

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27 Experimental results obtained in the first row of the orchard Experimental results obtained in the first row. Width = 4.44 m, Length = m. (a) Steering angles, (b) Lateral errors 26

28 Video First Row Width = 4.44 m, Length = m 0.5 m/s Forward Velocity Forward Camera Front Camera 27

29 3. Experiments to test the behaviour of the proposed model. Slippage information is taken into consideration. RTK-GPS is used for position feedback. 28

30 Odometer RTK-GPS Steering System 29

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32 Car Like Robot Model Without Slippage Car Like Robot Model With Slippage It is assumed that 31

33 Slippage Experiments on Snow 32

34 Reference Trajectory Tracking Control on Snow 6 4 Desired Real Vehicle Control Without Slip Estimation Y-Direction [m] X-Direction [m] Vehicle Control With Slip Estimation Y-Direction [m] Desired Real X-Direction [m] 33

35 30 20 w/o Estimation w/ Estimation Steering Angle [deg] Time [s] Forward Speed [m/s] w/o Estimation w/ Estimation Time [s] 34

36 4. Orchard Experiments. Slippage information is taken into consideration. Row Detection System (via Laser Scanning RangeFinder) is used. 35

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39 E1 results obtained by using RTK GPS feedback without using slippage estimation. E2 results obtained by using the slippage estimation procedure that uses RTK GPS feedback. E3 results obtained by using feedback information coming from dead reckoning algorithm. No slippage estimation procedure is adapted into the system model. E4 results obtained by using the slippage estimation process that uses the dead reckoning feedback information. 38

40 39 Video Turning control without slippage estimation

41 40 Video Turning control with slippage estimation

42 Special thanks to the co-authors of the paper: Gokhan Bayar*, Marcel Bergerman 1, E. ilhan Konukseven 2, A. Bugra Koku 2, Improving the trajectory tracking performance of autonomous orchard vehicles using wheel slip compensation, Biosystems Engineering, vol. 146, pp , Field Robotics Center, Robotics Institute, Carnegie Mellon University, Pittsburgh, PA, USA 2 Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey

43 Thanks for your attention