Detection systemDetection system

Using ultrasonic sensors for on-line weed detectionUsing ultrasonic sensors for on-line weed detectionD. Andújar 1, A Escolà-Agustí 2, C. Fernández-Quintanilla 1, J. Dorado 1

1 Instituto de Ciencias Agrarias, CSIC, Serrano 115B, 28006 Madrid, Spain2 Universitat de Lleida, Av. Rovira Roure 191, 25195 Lleida, Spain

ObjectiveObjective

ResultsResults

• Two maize fields, assessed at two dates (May 6 and May 25, 2010)

• Fields infested with one grass species (Sorghum halepense), and various broadleaf weeds (Datura ferox, Datura stramonium and Xanthium strumarium)

• In each date, static ultrasonic readings were taken in 180 points with different weed composition of pure and mixed grasses and/orbroadleaves. The system was also tested to acquire dynamic ultrasonic readings

• The validation of the ultrasound readings were performed in all the 180 static points as well as in 87 points for dynamic mapping validation, using plant height and weed biomass

• Two maize fields, assessed at two dates (May 6 and May 25, 2010)

• Fields infested with one grass species (Sorghum halepense), and various broadleaf weeds (Datura ferox, Datura stramonium and Xanthium strumarium)

• In each date, static ultrasonic readings were taken in 180 points with different weed composition of pure and mixed grasses and/orbroadleaves. The system was also tested to acquire dynamic ultrasonic readings

• The validation of the ultrasound readings were performed in all the 180 static points as well as in 87 points for dynamic mapping validation, using plant height and weed biomass

ConclusionsConclusions

The use of ultrasonic sensor readings proved useful to discriminate grasses (Sorghum halepense) (up to 81.1% of success) and broadleaf weeds (Datura sp. and/or Xanthium strumarium) (up to 98.5% of success)The use of ultrasonic sensor readings proved useful to discriminate grasses (Sorghum halepense) (up to 81.1% of success) and broadleaf weeds (Datura sp. and/or Xanthium strumarium) (up to 98.5% of success)

Experimental setupExperimental setup

To assess the use of ultrasonic sensors to detect weeds growing between crop lines, exploring their capabilities and limitations to discriminate weed species of different heights To assess the use of ultrasonic sensors to detect weeds growing between crop lines, exploring their capabilities and limitations to discriminate weed species of different heights

Grasses: dominance of Sorghum halepense(about 40 cm high)

Broad-leaves: dominance of

Datura stramonium (about 20 cm high)

Mixture of grasses and broad-leaves

weeds

GPS antenna

GPS antenna

Wire mesh to avoid crop

interference

Wire mesh to avoid crop

interference

Ultrasonic sensor

Ultrasonic sensor

Canonical Discrimination Analysis of ultrasonic readings, separating three groups depending on the type of weeds

Canonical Discrimination Analysis of ultrasonic readings, separating three groups depending on the type of weeds

5

Func

tion

2

Function 12.50-2.5

2.5

0

-2.5

GrassesMixtureMixtureBroad-leaves

Percentage of correct predictions using ultrasonic sensor to discriminate grasses from broadleaf weeds (2 groups) and considering also a mixture (three groups), on two different dates with static and dynamic readings

Percentage of correct predictions using ultrasonic sensor to discriminate grasses from broadleaf weeds (2 groups) and considering also a mixture (three groups), on two different dates with static and dynamic readings

Two groups Three groups

Dominance of grasses

Dominance of broad-leaves

Dominance of grasses

Mixture Dominance of broad-leaves

Static date1 81.1 98.5 57.5 (17.5*) 38.2 (20.0*) 97.0 (0.0**)

Static date 2 79.6 97.0 71.4 (7.1*) 46.2 (26.9*) 93.9 (0.0**)

Dynamic 77.8 97.0 71.4 (10.7*) 53.8 (23.1*) 87.9 (0.0**)

(*) % of cases misclassified as “broadleaf weeds”; (**) % of cases misclassified as “grasses”