Akira Mizushima

Automatic Navigation of the Agricultural Vehicle by the Geomagnetic Direction Sensor and Gyroscope

The objective of this research is to develop an automatic guidance system composed of relatively low cost sensors. As a navigation sensor, we used a geomagnetic direction sensor (GDS) and a gyroscope. To increase the accuracy of these sensors outputs and navigation performance, these sensor output were integrated based on sensor fusion technique. In this paper, the precise estimation method of the vehicle orientation was proposed. First, the noise of the GDS and inclinometer were eliminated by the adaptive line enhancer(ALE). As the result of inclination correction of the GDS by ALE, the corrected GDS was consistent with the actual orientation. Second, the drift error of the gyroscope was estimated by least square method(LSM). Third, these sensors output were integrated to obtain the accurate vehicle orientation. Finally, to evaluate the accuracy of the proposed estimation method of orientation, the automatic navigation test was carried out in the actually used field. As a result of the automatic navigation test, it was confirmed that proposed estimation method had the ability to navigate the mobile vehicle with high accuracy.

Development of Robot Tractor Using the Low-Cost GPS/INS System

In this research, low cost navigation sensor unit composed of three vibratory gyroscopes and two inclinometers and the GPS for the agricultural vehicle was developed. The sensor can provide the position corrected by inclination, heading angle and roll/pitch inclinations. The microcomputer (H8S2612) was installed to measure the sensors data and calculate the corrected position, corrected heading and corrected inclination by itself without using laptop computer and high resolution A/D converter. To measure the accuracy of developed sensor unit, the field test was conducted. The developed sensor unit could estimate the heading angle with 1.59° and roll angle with 0.41° and pitch angle with 0.65°. This accuracy was equivalent to the accuracy of RTK-GPS and IMU system using high resolution A/D converter and laptop computer.

3-D GIS Map Generation Using a Robot Tractor with a Laser Scanner

3-D GIS Map Generation is necessary for applying precision agriculture to acquire the information of field environment. This research allows the autonomous robot tractor to gather surrounding spatial information in a field. For instance, soil moisture content and soil organic matter strongly affect crop growth and yield. Thus, it is important to understanding the variability in the field to be able to promote precision agriculture. In this study, a laser scanner, attached with inclination to the roof of the tractor, acquires the 3-D information by scanning in a plane. It was able to detect objects within 80 m radius during tractor’s navigation. In addition, a RTK-GPS measured vehicle position while a posture sensor determined azimuth. This sensing system was able to map in UTM coordinate system the terrain and surrounding components including trees and buildings; moreover it automatically generated a field topography map. This system is promised to be an important tool for future decision makers in agriculture.

Development of navigation sensor unit for the agricultural vehicle

In this paper, low cost navigation sensor unit composed of three vibratory gyroscopes and two inclinometers and the DGPS was developed. The sensor can provide the position corrected by inclination, heading angle and roll/pitch inclinations. And the measured position was interpolated by the dead reckoning, because the sampling rate of the DGPS was 1 Hz. The accuracy of developed sensor unit was evaluated by field test on the flat field, gentle slope and bumpy road.

Automatic Guidance System Composed of Geomagnetic Direction Sensor and Fiber Optic Gyroscope

Abstract The objective of this research is to develop an automatic guidance system composed of relatively low cost sensors. As a navigation sensor, a geomagnetic direction sensor (GDS) and a gyroscope were employed. To increase the accuracy of these sensor outputs and guidance performance, these sensor output were integrated by sensor fusion technique. In the paper, a fiber optical gyroscope (FOG) was applied as a gyroscope. To evaluate the performance of these sensors for utilizing on an automatic guidance, and to confirm the effect of sensor fusion technique, the automatic guidance test was conducted on a paddy field. In the paper, a kalman filter was employed as sensor fusion method. The kinematics of a vehicle was modeled and heading error and lateral offset were estimated by the kalman filter. The developed fusion technique was able to control the vehicle automatically with higher accuracy compared to that using single navigation sensor.

Automatic Guidance System Based on Sensor Fusion with Geomagnetic Direction Sensor and Gyroscope

Abstract In this paper, we proposed the dynamic compensation method for a geomagnetic warp and a gyro drift for constructing the adaptive automatic guidance system. Temporal and spatial geomagnetic variation makes the measurement error of a geomagnetic direction sensor(GDS) larger. On the other hand, drift error can not be ignored for a fiber optic gyroscope(FOG). Therefore, there is a limitation to develop the robust guidance system with fixed desired heading direction which used in conventional system. To resolve these problem, manual operation was carried out before automatic operation and initial desired direction was acquired. In the research, a desired direction and a heading direction was modified gradually by means of weighting by variance of a GDS and FOG during the automatic operation. To evaluate the accuracy and robustness of the developed system, the guidance system using the GDS alone and that using an adaptive guidance system were compared by a field test. From the test, it was confirmed that the accuracy and robustness improved by utilizing the proposed guidance system.