Sensor development for estimation of biomass yield applied to Miscanthus Giganteus

Precision Agriculture technologies such as yield monitoring have been available for traditional field crops for decades. However, there are currently none available for energy crops such as Miscanthus Giganteus (MxG), switch grass, and sugar cane. The availability of yield monitors would allow better organization and scheduling of harvesting operations. In addition, the real-time yield data would allow adaptive speed control of a harvester to optimize performance. A yield monitor estimates a total amount of biomass per coverage area in kg/m2 as a function of location. However, for herbaceous type crops such as MxG and switchgrass, directly measuring the biomass entering a harvester in the field is complicated and impractical. Therefore, a novel yield monitoring system was proposed. The approach taken was to employ an indirect measure by determining a volume of biomass entering the harvester as a function of time. The volume can be obtained by multiplying the diameter related cross-sectional area, the height and the crop density of MxG. Subsequently, this volume is multiplied by an assumed constant, material density of the crop, which results in a mass flow per unit of time. To determine the coverage area, typically the width of the cutting device is multiplied by the machine speed to give the coverage area per unit of time. The ratio between the mass flow and coverage area is now the yield per area, and adding GPS geo-references the yield. To measure the height of MxG stems, a light detection and ranging (LIDAR) sensor based height measurement approach was developed. The LIDAR was applied to scan to the MxG vertically. Two measurement modes: static and dynamic, were designed and tested. A geometrical MxG height measurement model was developed and analyzed to obtain the resolution of the height measurement. An inclination correction method was proposed to correct errors caused by the uneven ground surface. The relationship between yield and stem height was discussed and analyzed, resulting in a linear relationship. To estimate the MxG stem diameter, two types of sensors were developed and evaluated. Firstly, a LIDAR based diameter sensor was designed and tested. The LIDAR was applied to scan MxG stems horizontally. A measurement geometry model of the LIDAR was developed to determine the region of interest. An angle continuity based pre-grouping algorithm was applied to group the raw data from the LIDAR. Based on the analysis of the presentation of MxG stems in the LIDAR data, a fuzzy clustering technique was developed to identify the MxG stems within the clusters. The diameter was estimated based on the clustering result. Four types of clustering techniques were compared. Based on their performances, the Gustafson - Kessel Clustering algorithm was selected. A drawback of the LIDAR based diameter sensor was that it could only be used for static diameter measurement. An alternative system based on a machine vision based diameter sensor, which supported the dynamic measurement, was applied. A binocular stereo vision based diameter sensor and a structured lighting-based monocular vision diameter estimation system were developed and evaluated in sequence. Both systems worked with structured lighting provided by a downward slanted laser sheet to provide detectable features in the images. An image segmentation based algorithm was developed to detect these features. These features were used to identify the MxG stems in both the binocular and monocular based systems. A horizontally covered length per pixel model was built and validated to extract the diameter information from images. The key difference between the binocular and monocular stereo vision systems was the approach to estimate the depth. For the binocular system, the depth information was obtained based on disparities of matched features in image pairs. The features were matched based on a pixel similarity in both one dimensional and two dimensional based image matching algorithm. In the monocular system, the depth was obtained by a geometry perspective model of the diameter sensor unit. The relationship between yield and stem diameter was discussed and analyzed. The result showed that the yield was more strongly dependent upon the stem height than diameter, and the relationship between yield and stem volume was linear. The crop density estimation was also based on the monocular stereo vision system. To predict the crop density, the geometry perspective model of the sensor unit was further analyzed to calculate the coverage area of the sensor. A Monte Carlo model based method was designed to predict the number of occluded MxG stems based on the number of visible MxG stems in images. The results indicated that the yield has a linear relationship with the number of stems with a zero intercept and the average individual mass as the coefficient. All sensors were evaluated in the field during the growing seasons of 2009, 2010 and 2011 using manually measured parameters (height, diameter and crop density) as references. The results showed that the LIDAR based height sensor achieved an accuracy of 92% (0.3m error) to 98.2% (0.06m error) in static height measurements and accuracy of 93.5% (0.22m error) to 98.5% (0.05m error) in dynamic height measurements. For the diameter measurements, the machine vision based sensors showed a more accurate result than the LIDAR based sensor. The binocular stereo vision based and monocular vision based diameter measurement achieved an accuracy of 93.1% and 93.5% for individual stem diameter estimation, and 99.8% and 99.9% for average stem diameter estimation, while the achieved accuracy of LIDAR based sensor for average stem diameter estimation was 92.5%. Among three stem diameter sensors, the monocular vision based sensor was recommended due to its higher accuracy and lower cost in both device and computation. The achieved accuracy of machine vision based crop density measurement was 92.2%

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Boundary, Brightness, and Depth Interactions During Preattentive Representation and Attentive Recognition of Figure and Ground

This article applies a recent theory of 3-D biological vision, called FACADE Theory, to explain several percepts which Kanizsa pioneered. These include 3-D pop-out of an occluding form in front of an occluded form, leading to completion and recognition of the occluded form; 3-D transparent and opaque percepts of Kanizsa squares, with and without Varin wedges; and interactions between percepts of illusory contours, brightness, and depth in response to 2-D Kanizsa images. These explanations clarify how a partially occluded object representation can be completed for purposes of object recognition, without the completed part of the representation necessarily being seen. The theory traces these percepts to neural mechanisms that compensate for measurement uncertainty and complementarity at individual cortical processing stages by using parallel and hierarchical interactions among several cortical processing stages. These interactions are modelled by a Boundary Contour System (BCS) that generates emergent boundary segmentations and a complementary Feature Contour System (FCS) that fills-in surface representations of brightness, color, and depth. The BCS and FCS interact reciprocally with an Object Recognition System (ORS) that binds BCS boundary and FCS surface representations into attentive object representations. The BCS models the parvocellular LGN→Interblob→Interstripe→V4 cortical processing stream, the FCS models the parvocellular LGN→Blob→Thin Stripe→V4 cortical processing stream, and the ORS models inferotemporal cortex.Air Force Office of Scientific Research (F49620-92-J-0499); Defense Advanced Research Projects Agency (N00014-92-J-4015); Office of Naval Research (N00014-91-J-4100