An Autonomous Crop Treatment Robot: Part I. A Kalman Filter Model for Localization and Crop/Weed Classification

Abstract

This work is concerned with a machine vision system for an autonomous vehicle designed to treat horticultural crops. The vehicle navigates by following rows of crop (individual cauliflower plants) that are planted in a reasonably regular array typical of commercial practice. We adopt an extended Kalman filter approach where the observation model consists of a grid which is matched to the crop planting pattern in the perspective view through the vehicle camera. Plant features are extracted by thresholding near infrared images of the scene evolving before the camera. A clustering method collects the features into groups representing single plants. An important aspect of the approach is that it provides both localization information and crop/weed discrimination within a single framework, since we can assume that features not matching the planting pattern are weeds.

Off-line tests with two image sequences are carried out to compare the tracking with assessment by three different humans. These show that the extended Kalman filter is a viable method for tracking and that the model parameters derived from the filter are consistent with human assessment.

We conclude that the performance will be good enough for accurate in-field navigation.

Keywords

vision guidance localization Kalman filter agriculture

Get full access to this article

View all access options for this article.

References

Bar-Shalom, Y. , and Fortmann, T. 1988. Tracking and Data Association. New York: Academic Press.

Biller, H.R. 1998. Reduced input of herbicides by use of optoelectronic sensors , Journal of Agricultural Engineering Research 71:357-362.

Billingsley, J. , and Schoenfisch, M. 1997. The successful development of a vision guidance system for agriculture, Computers and Electronics in Agriculture 16:147-163.

Brady, M. , Durrant-Whyte, H. , Hu, H. , Probert, P. , and Rao, B.S.Y. 1990. Sensor-based control of AGVs, Computing and Control Engineering Journal 64-70.

Marchant, J.A. , and Brivot, R. 1995. Real time tracking of plant rows using a Hough transform , Real Time Imaging, 1:363-371.

Brivot, R. , and Marchant, J.A. 1996. Segmentation of plants and weeds for a precision crop protection robot using infrared images, IEE Proc.-Vis. Image Signal Process 143(2).

Curwen, R.M. , and Blake, A. 1992. Dynamic Contours: Real-time active splines, In Active Vision, eds. A. Blake and A. Yuille , chap. 3, MIT Press.

Freeman, H. 1961. On the encoding of arbitrary geometric configurations , IEEE Trans. Elec. Computers EC- 10, 260- 268.

Hague, T. , Marchant, J.A. , and Tillett, N.D. 1997. Autonomous robot navigation for precision horticulture , IEEE International Conference on Robotics and Automation, Albuquerque.

10.

Hague, T. , and Tillett, N.D. 1996. Navigation and control of an autonomous horticultural robot, Mechatronics 6(2):165- 180.

11.

Leclerc, Y.G. , Luan, Q.-T. , and Fua, P. 1999. Self-consistency: A novel approach to characterizing the accuracy and reliability of point correspondence algorithms, In ICVS Workshop on the Performance Characterization and Benchmarking of Vision systems, eds. A. F. Clark and P. Courtney, 1-19. BMVA.

12.

Leonard, J.J. , and Durrant-Whyte, H.F. 1991. Mobile robot localization by tracking geometric beacons, IEEE Trans. Robotics and Automation 7(3):376-382.

13.

Marchant, J.A. 1996. Tracking of row structure in three crops using image analysis , Computers and Electronics in Agriculture 159:161-179.

14.

Maybank, S.J. 1990. Filter based estimates of depth, In Proceedings BMVC, 349-354.

15.

McLellan, J.F. , and Friesen, L. 1996. Who needs a 20 cm precision farming system?, Position Location and Navigation Symposium 426-432. IEEE .

16.

Ollis, M. , and Stentz, A. 1997. Vision-based perception for an automated harvester, In Proceedings IEEE/RSJ International Workshop on Intelligent Robots and Systems, IROS '97 3:1838-1844.

17.

Pratt, W.K. 1991. Digital image processing. 2nd ed., John Wiley.

18.

Preparata, F.P. , and Shamos, M.I. 1985. Computational Geometry-An Introduction, New York: Springer-Verlag.

19.

Reynard, D. , Wildenberg, A. , Blake, A. , and Marchant, J.A. 1996. Learning dynamics of complex motions from image sequences . In Lecture Notes in Computer Science, Computer Vision - ECCV `96, eds. B. Buxton and R. Cipolla, Springer.

20.

Sanchiz, J.M. , Pla, F. , Marchant, J.A. , and Brivot, R. 1996. Structure from motion techniques applied to crop field mapping, Image and Vision Computing 14:353-363.

21.

Southall, B. , Buxton, B.F. , Marchant, J.A. , and Hague, T. 2000. On the performance characterization of image segmentation algorithms: A case study, In Proceedings 6th European Conference on Computer Vision, ed., David Vernon. Springer Verlag.

22.

Southall, J.B. 1999. The Development and Evaluation of Computer Vision Algorithms for the Control of an Autonomous Horticultural Vehicle, PhD thesis, University of London, Dept. Computer Science, University College London , UK.

23.

Stafford, J.V. 1996. Spatially variable field operations, Computers and Electronics in Agriculture Special Issue on Spatially Variable Field Operations 14(2-3):99-100.

24.

Stevens, A. , Stevens, M. , and Durrant-Whyte, H.F. 1995. OXNAV: Reliable autonomous navigation, In Proceedings of the 1995 IEEE International Conference on Robotics and Automation 3:2607-2612.

25.

Tillett, N.D. , Marchant, J.A. , and Hague, T. 1996. Autonomous plant scale crop protection, AgEng, Madrid.

26.

Torr, P.H.S. , and Zisserman, A. 1997. Performance characterization of fundamental matrix estimation under image degradation, Machine Vision and Applications 9:321-333.

27.

Tsai, R.Y. 1986. An efficient and accurate camera calibration technique for 3D machine vision, In Proc. IEEE Computer Soc. Conf. Comp Vis Patt Recog, Miami Beach, FL.

28.

van Trees, H.L. 1968. Detection, Estimation and Modulation Theory, Part I, John Wiley and Sons.

29.

Yoshida, J. , Okuyama, S. , and Ito, K. 1988. Automatic control of agricultural machines, In Proceedings of the International Congress On Transportation Electronics '88.

30.

Zwiggelaar, R. 1998. A review of spectral properties of plants and their potential use for crop/weed discrimination in row-crops, Crop Protection 17(3):189-206.