Tomohiro Takigawa

Development of Auto-Hitching Navigation System for Farm Implements Using Laser Range Finder

Automatic hitching is a challenging task in agricultural automation that could potentially improve safety and reduce drudgery for farmers during coupling of farm implements with tractors. In this study, we attempt the automatic hitching of an implement and tractor using discriminated and localized landmarks and a laser range finder (LRF). Reflectors were used as landmarks, and field experiments were carried out to discriminate among and localize three different shapes of reflector: rectangular, cylindrical, and trapezoidal. The rectangular reflectors were easy to attach to the implement, and accuracy was satisfactory at longer distances. In contrast, the cylindrical and trapezoidal reflectors had the respective drawbacks of fitting data into the regular shape of a circle and template matching of multiple lines from a longer distance. The average errors of rectangular reflectors at the target position were less than 2 cm in x-y coordinates from a distance of 10 m from the LRF. In the second experiment, navigation of the tractor and automatic hitching were done based on localization of reflectors by the LRF, which was investigated using an actual-size autonomous tractor. The results of the experiments confirmed that the autonomous tractor could navigate to the implements position within an average final lateral error of 3 cm and a directional error of 2° for single reflector and double reflector positioning methods on a concrete surface and on a soft, undulating grass field. We found that the number of successful automatic hitching trials was higher with the double-reflector positioning method as compared to the single-reflector positioning method on the concrete surface. For the undulating grass field surface, we attached a guide rail to increase the tolerance of lateral deviation on this surface and noted a higher number of successful trials of automatic hitching with the double reflectors. It can be concluded that automatic hitching is possible using reflectors as an artificial landmark attached to the implement to ensure safe coupling of heavy farm implements with a tractor.

Simple and rapid determination of free fatty acids in brown rice by FTIR spectroscopy in conjunction with a second-derivative treatment.

A simple and rapid method for the determination of free fatty acid (FFA) content in brown rice using Fourier transform infrared spectroscopy (FTIR) in conjunction with second-derivative treatment was proposed. Ground brown rice (10g) was soaked in toluene (20mL) for 30min, and the filtrate of the extract was placed in a 1mm CaF2 liquid cell. The transmittance spectrum of the filtrate was recorded using toluene for the background spectrum. The absorption band due to the CO stretching mode of FFAs was detected at 1710cm(-1), and the Savitzky-Golay second-derivative treatment was performed for band separation. A single linear regression model for FFA was developed using the 1710cm(-1) band in the second-derivative spectra of oleic acid in toluene (0.25-2.50gL(-1)), and the model displayed high prediction accuracy with a determination coefficient of 0.998 and a root mean square error of 0.03gL(-1).

Vision-Based Leader Vehicle Trajectory Tracking for Multiple Agricultural Vehicles.

The aim of this study was to design a navigation system composed of a human-controlled leader vehicle and a follower vehicle. The follower vehicle automatically tracks the leader vehicle. With such a system, a human driver can control two vehicles efficiently in agricultural operations. The tracking system was developed for the leader and the follower vehicle, and control of the follower was performed using a camera vision system. A stable and accurate monocular vision-based sensing system was designed, consisting of a camera and rectangular markers. Noise in the data acquisition was reduced by using the least-squares method. A feedback control algorithm was used to allow the follower vehicle to track the trajectory of the leader vehicle. A proportional–integral–derivative (PID) controller was introduced to maintain the required distance between the leader and the follower vehicle. Field experiments were conducted to evaluate the sensing and tracking performances of the leader-follower system while the leader vehicle was driven at an average speed of 0.3 m/s. In the case of linear trajectory tracking, the RMS errors were 6.5 cm, 8.9 cm and 16.4 cm for straight, turning and zigzag paths, respectively. Again, for parallel trajectory tracking, the root mean square (RMS) errors were found to be 7.1 cm, 14.6 cm and 14.0 cm for straight, turning and zigzag paths, respectively. The navigation performances indicated that the autonomous follower vehicle was able to follow the leader vehicle, and the tracking accuracy was found to be satisfactory. Therefore, the developed leader-follower system can be implemented for the harvesting of grains, using a combine as the leader and an unloader as the autonomous follower vehicle.

Several contributions to soil compactibility induced by cyclic loading test

Abstract To investigate the soil compactibility during the cyclic loading, three different kinds of paddy field soils were prepared so as to clarify interrelationships among stress amplitude ratio, bulk density, soil water content and pore water pressure. The presetting values of specimen include the soil water content(percent dry basis) and bulk density of 25% d.b. and 1.1 Mg/m 3 respectively. The relation between the number of cyclic loading and axial strain exhibited an asymptotically increasing trend, converging toward a specific value for each experimental condition. Possible effect caused by elastic–plastic characteristics could be recognized, when axial strain for 0.5 Hz excitation becomes greater than the one of 1.0 Hz under same stress amplitude ratio. When the stress amplitude ratio took 0.1, the absolute value of axial strain of 0.5 Hz was greater than the one of 1.0 Hz, whereas its decreasing trend was recognized in the sequence of silt, clay and silty sand. The qualitative relations between pore water pressure and number of cyclic loading were also examined to scrutinize the effect of effective water pressure to the soil compactibility.

Truck allocation planning for cost reduction of mechanical sugarcane harvesting in Thailand: an application of multi-objective optimization

In Thailand, the chopper-type mechanical sugarcane harvester is widespread. This type of harvester usually operates with some trucks. When sufficient numbers of trucks are available, the chopper can carry out continuous harvest operation. However, there are not enough trucks in the surveyed region to cover the transportation needs. Hence, effective allocation planning of trucks is vital. By determining the optimum number of trucks needed for the sugarcane fields, it is possible to make efficient use of the chopper.

On-the-Go Laser-based Sensing System for Measuring Plants Height Using an Autonomous Tractor

Laser-based technologies are recently recognized for their impact on improving agricultural productivity and non-destructive measurement to the environment. The high temporal and low spatial resolutions have the limitations in implementing space and airborne aerial remote sensing methods for site specific management of crops. On the other hand, the ground-based sensing has immense potential for plant growth monitoring and becomes popular for site-specific management. Thus, the objectives of this research were to develop the operational scenario by an autonomous tractor and monitor plant growth based on the reflection height using laser range finders. In this regard, two Laser Range Finders (LRFs) were installed at the back of the autonomous tractor to conduct field experiments. First, LMS 211 LRF for relative positioning to approach the farm implement, coupling the implement and navigated at the field using artificial landmarks. Second, URG 04-LX LRF for quick assessment of crop status. The calibration of laser sensors was conducted for successful landmarks detection and plant canopy sensing. The autonomous tractor was used in this experiment with Programmable Logic Control (PLC) unit, hydraulic actuators for gear shifting and steering mechanism, LRF for relative positioning and RTK GPS for absolute positioning of the tractor. The operational scenario for field operations was developed including coupling, parking, and forward-backward movement using LMS211 LRF. The 2D laser cloud scan points were analyzed to measure reflection height from plants using URG 04-LX LRF. The reflection heights were used as a reference to develop surface map of plant growth under the tree canopy. Different types of plant’s reflection height were measured from the cluster of scan points reflected from the plant canopies at the Agricultural and Forest Research Center, University of Tsukuba. Further experiments will be presented to correlate plant growth and yield of plant biomass over the growing seasons.

Simulation of a Steering Aid Method for an Agricultural Tractor-Trailer System

This paper presents a method of man-machine system to help a driver to steer an agricultural tractor-trailer system, in which the tractor has a hitching bar. Since backing-up motion of the tractor-trailer system is unstable, steering the system backwards tends to be a difficult task. Consequently, a skilled driver is required. The objective of the proposed method is to enable a driver to steer the tractor-trailer system backwards as though the driver steered only the tractor. The feedback control is designed simply. A wheel joystick is used to specify a desired orientation of the tractor-trailer system. The performance of the control system is examined through computer simulations using a kinematic model of the tractor-trailer system. Simulation results confirm that the proposed method is able to help a driver to steer the tractor-trailer system to the given orientations as intended.