YANMAR Technical Review

Abstract

Wine grapes are grown on over 7.2 million hectares of land worldwide. Vertical shoot position (VSP) is a widely used trellis system in vineyards, which are sometimes located on steep hills.
Yanmar has developed a spraying robot for use in French vineyards that helps to prevent pesticide exposure and worker injuries on steep slopes.

1. Introduction

Wine grapes are grown on over 7.2 million hectares of land worldwide, producing over 200 million hectoliters of wine^*1. Wine grapes do best in sunny locations with free-draining soils and are often grown on slopes. Most are grown on trellis systems whereby the vines are arranged into rows and the shoots trained to grow up the vertical plane of the trellis.
In the Champagne and Burgundy regions of France, a major wine producing nation, the spacing between rows of grape vines is only about 1 m. Tasks such as spraying are performed using small crawler carriers or a straddle tractor that travels astride the vines. Exposure to high-concentration spray is one of the problems with crawler carriers, which oblige the driver to wear a protective mask and clothing and to work in the full glare of the sun (Fig. 1). Straddle tractors, on the other hand, while able to perform work efficiently, require skill to operate and are often involved in slipping or roll-over accidents when operated on sloped ground (Fig. 2). Labor shortages and factors such as workforce aging mean that skilled operators are becoming difficult to find.
To overcome these problems, Yanmar has developed the YV01 spraying robot that is easy to configure and can operate autonomously and safely on sloped ground (Fig. 3).

• *1International Organization of Vine and Wine, 2023

2. Achieving Operating Stability on Steep Slopes and Difficult Terrain

2.1. Vehicle Design

Fig. 4 shows the main components of the YV01.
The average slope of vineyards in Champagne is 12% (about 7°), with slopes of up to 60% (about 31°) in some places. The mostly chalky soils include a mix of clay and sand, with gravel that contains rocks of up to fist size in some places. To ensure vehicle stability when travelling over such difficult terrain, Yanmar chose a crawler tractor mechanism for its spraying robot.
The robot is propelled by a hydraulic motor located inside the crawlers and driven by a variable-capacity hydraulic pump mounted on the vehicle frame. It has a lightweight, inverted-U shaped design made possible by the highly flexible hydraulic piping. This allows it to straddle vines of up to 1.4 m in height. As the left and right crawlers are able to operate in opposite directions with continuous variability, the robot can be navigated around the confined spaces of vineyards with ease and accuracy.
The engine, hydraulic pump, hydraulic tank, and other heavy parts are positioned low down on the left side of the vehicle frame, and the spray tank, spray pump, and other spraying equipment are on the right side of the frame. This configuration allows the robot to travel up and down 45% (24°) slopes and laterally across 20% (11°) slopes.

2.2. Autonomous Driving Control

The vineyards where the YV01 operates tend to have steep slopes and very slippery soil. Moreover, even a slight deviation from the travel path can result in physical contact between robot and vine. Accordingly, Yanmar adopted model predictive control to ensure that the robot would be able to travel around such vineyards reliably. Model predictive control achieves robust performance by using the control model to predict vehicle behavior at each control cycle and then operating the vehicle accordingly. Its adoption 20% improvement in response performance over the course of the development and provided the robot with a level of performance such that, should it deviate from its path due to uneven terrain or slipping, it can correct itself immediately and avoid coming into contact with the vines (Fig. 5).

Yanmar also adopted model-in-the-loop simulation (MILS) and rapid control prototyping (RCP) to accelerate the control software development process.
MILS is a technique for performing control design on a simulation that combines the characteristics of both the control model and plant model. This allows functions and performance to be assessed in simulations prior to real-world machine testing, including for hazardous operations.
The real-world machine testing, meanwhile, was able to take advantage of rapid prototyping as the control model created using MILS can be downloaded to the RCP controller without further modification. Improvements to functions and performance could also made efficiently by comparing field testing data with the MILS results (Fig. 6).

3. Building a Simple User Interface that is Easy to Understand

3.1. User Interface Concept

The automation of agricultural machinery involves an increasing number of input operations, including setting the parameters for each task being performed and generating the routes for autonomous travel through the vineyard and when performing the assigned tasks. Consequently, operators also need to learn how to do this setup. While the operators, who range in age from young to very experienced workers, may be familiar with how to operate the equipment, one of the challenges is that older workers in particular find it difficult to make the most of the new technology and it often takes them a long time to learn these new input operations. This has led to customer feedback asking for this step to be eliminated so that the equipment will be easy for anyone to operate, so Yanmar has done away with having a dedicated control terminal for the YV021 and instead designed it to be operated using only a smartphone, a generic device with which people are broadly familiar.

3.2. User Control of Robot During Operation

To enable the YV01 to perform tasks in response to simple user control actions, it has been made to operate automatically using its autonomous driving system (Fig. 7).
The vineyard being maintained and the paths to follow when performing tasks are defined beforehand on the web system (vineyard server) at the customer’s request.
The operator then uses their smartphone to specify the vineyard where they want the robot to work, the task they want it to perform, and which robot to use (Fig. 8 and Fig. 9). These settings are forwarded to the YV01 robot automatically and the remote control is used to instruct it to travel to the location and start work.
From this point, the robot performs its task automatically, following a path that is determined based on a precise machine position calculated using the GNSS^*2 receiver on the YV01 and the correction signal from the Ntrip^*3 server.

• *2Global Navigation Satellite System
• *3Networked Transport of RTCM via Internet Protocol (NTRIP) is a positioning system that receives GNSS correction data via the Internet and enhances positioning accuracy by correcting for satellite positioning error and radio signal delay error.

4. Conclusions

Yanmar commenced sales of spraying robots for vineyards in the French market in 2023. An autonomous weeding function was added in 2024 with the addition of a weeder attachment (Fig.10). In the future, Yanmar intends to expand the range of tasks the robot can perform by continuing to supply products and solutions for the French vineyard market that suit local needs. Yanmar also intends to contribute to the sustainability of local industry by extending the autonomous driving technology and system developed for this robot to other localities and crops.

• YV01 product information (English)
  https://www.yanmar.com/fr/viticulture/en/
• Yanmar Vineyard Solutions branding video
  • Japanese
    https://www.youtube.com/watch?v=XxuDAP3YM7Q
  • English
    https://www.youtube.com/watch?v=1xr2ljBA490
  • French
    https://www.youtube.com/watch?v=qeFnirFc2r4
• HANASAKA movie Yanmar Vineyard Solutions
  • Japanese
    https://www.youtube.com/watch?v=UpS94kHzNA4
  • English
    https://www.youtube.com/watch?v=KufNkm0sB1c