# Autonomous and Safe Navigation of Mobile Robots in Vineyard with Smooth Collision Avoidance
## 1 Introduction  
In recent years, autonomous robots have extensively been used to lower the burden of farmers. In several countries, demographic changes are a major factor behind this trend. For instance, the proposed research was carried out in vineyards in Japan where there is an increase in the old-age population in Japan. Moreover, the number of farmers is steadily decreasing. This makes it difficult to sustain agriculture and related industries. Figure 0(a) shows the population and average age of farmers in Japan from year 2000 to year 2014 based on a survey by Japan's Ministry of Agriculture, Forestry and Fisheries (MAFF) [1]. It is clear that the farming population in Japan is steadily declining from 2.4 million in the year 2000 to 1.68 million in the year 2014. On the contrary, it is also evident that the average age of the farmers is steadily increasing. The average farmer's age in Japan was 62.2 years in the year 2000, which was already an alarming situation. The situation worsened in the year 2014 when the average farmer's age reached 66.8 years. Figure 0(b) shows the gender wise comparison of the farming population in Japan. A similar trend can be seen from this figure. Most of the male and female farming population is concentrated around the 65\(\sim\)69 years age-group. What is alarming is that a significant farming population can be seen in the 70\(\sim\)74 years age-group and above. In Japan, the younger population is reluctant to engage in laborious farming activities and instead prefer office work. The situation becomes graver as Japan faces fierce competition from low-cost products from abroad, andis often forced to either reduce costs or to find a way to add value to their products. This trend is seen in other countries too, where there is also a problem of shortage of farmers. It should be noted that apart from the aging population, there are several other factors that necessitate the incorporation of field robots in agriculture. However, since this research was conducted in Japan, which faces severe demographic challenges, this effect has been emphasized. A major concern with agricultural activities is that they involve mostly labor-intensive tasks. Such tasks are difficult to perform for old people. Robotic technology has a large potential to support agricultural activities by automating many tasks. Such efforts to lower the burden of farmers by automating tasks to reduce labor are highly desirable as they directly lead to an increase in production and sustainable agriculture. In recent years, autonomous agricultural robots have shown remarkable progress to support different activities autonomously or semi-autonomously. However, many challenges still remain as open problems. In order to autonomously perform tasks in the farms, autonomous navigation is a quintessential component of robots. Generally, GPS is used in outdoor farms to localize the robot and enable it to navigate autonomously. Lidars have also been  
Figure 1: (**a**) Population and average age of farmers in Japan. Data from Japan’s Ministry of Agriculture, Forestry and Fisheries (MAFF) [1]. (**b**) Census of agriculture in Japan [1]. used extensively. Both GPS and Lidar have their own merits and demerits. The cost of these sensors generally vary a lot depending on various factors such as precision, accuracy and robustness. Accurate GPS (centimeter level precision) is expensive. On the other hand, an inexpensive GPS generally has an error in the order of tens or hundreds of centimeters, which is unfit for robot navigation in a vineyard with a lane width of approximately 2.5 m. Three-dimensional Lidars such as Velodyne VLP-16 and VLP-32 are expensive; however, a 2D Lidar is relatively cheaper with good accuracy. Since our research is focused in Japan, the QZSS (Quasi-Zenith Satellite) system, also called 'Michibiki', that launched in 2018 is worth mentioning [2; 3].