1.Outline

Agriculture in Japan today is showing a decline in the number of farmers and an increase in the number of aging farmers, which make it hard to find operators with necessary technical skills and abilities. The rice planting operation, which is the aim of this development, requires a high-accuracy, straight line operation while planting the rice along the seedling rows which were planted in the previous procedure. A low-accuracy operation can affect later processes such as maintenance tasks and harvesting operations which will result in lower yields. In recent years, overseas have started to adopt the automated control technologies into agricultural machineries that utilize the Global Navigation Satellite System. However, the high cost and the complex operation have been factors for limited interest in Japan. From these backgrounds, we came up with a concept of “low-cost machine that can keep working locus straightly for everyone” which will be widely accepted by farmers, and make high accuracy rice-planting operation possible by even unskilled operators such as part-time employees. We have developed a unique signal processing technology with an affordable system configuration that calculates highly accurate information on positions and directions. Moreover, we have developed a unique “keeping straight” control technology that will perform an operation equal to that of a skilled operator even in paddy fields with several conditions of uncertain elements. The machine has undergone repeated test runs in paddy fields nationwide and it has been proven to demonstrate a high performance. We have been well accepted by the market since its launch in 2016 due to the affordability of the machine with high spec control functions, namely the auto steering feature.

2.Detail of the technology

The outline of the functions is shown in Figure 1, and the operation interface in Figure 2. For the first straight-line operation, the operator uses the two reference memory switches to register a target line for auto steering. After turning, the auto steering can be activated by switching on the GS switch. After that, we just have to do is turning off the auto steering with GS switch when it had reached at the end of the line, and switch on the auto steering after turning around the machine. By pinpointing the necessary operation, it will reduce the complexity and the users will find it very easy to operate.

Figure 1 System Overviews

Figure 2 Control Interface

Figure 3 shows the system configuration. The steering mechanism consists of a steering assist device (a combination of an electric motor and a transmission mechanism) built just above the power steering device. Moreover, this development has adopted the less costly DGPS instead of the high precision RTK-GNSS which is generally the choice made in the agricultural industry. We have combined the moderate precision DGPS and the inertial measurement unit (IMU) and have implemented the algorithm that accurately calculates the vehicle position and the azimuth angle in real time.

Figure 3 System Configuration

We have examined the operating skills of experienced operators and have implemented these elements in developing the vehicle control. We have developed a keeping straight-line control algorithm (Figure 4) by combining the position correction control of the position adjustment motion and the straight-line motion control towards a target direction. By doing so, we have succeeded in realize a highly robust machine that runs in a straight line even in paddy fields with several conditions of uncertain elements.

Figure 4 Control Diagram

Miyamoto, Jumpei^*1

Kubota, Yuki^*2

Naomoto, Akira^*2

Iwami, Kenichi^*2

Yoshida, Kazumasa^*2

^*1 Regular member，Kubota Corporation (64 Ishizu-kitamachi, Sakai-ku, Sakasi-shi, Osaka-fu 590-0823)

^*2 Kubota Corporation (64 Ishizu-kitamachi, Sakai-ku, Sakasi-shi, Osaka-fu 590-0823)