*4.1.2 Examples of wheeled robots*

Some examples of wheeled mobile platforms for agriculture are the conventional tractor using the Ackermann steering system (**Figure 2**) with two front passive and steerable wheels and two rear fixed and active wheels.

Skid steering platforms can be found in many versions. For example,


Regarding the independent steering scheme, the robot developed by Bak and Jakobsen [30] is one of the first representative examples (**Figure 4a**). This platform was designed specifically for agricultural tasks in wide-row crops and featured good ground clearance (approximately 0.5 m) and 1-m wheel separation. The platform is based on four-identical wheel modules. Each one includes a brushless electric motor that provides direct-drive power, and steering is achieved by a separate motor.

An example of a mobile platform under development that focuses on performing precision agricultural tasks is AgBot II (**Figure 4c**). This is a platform that follows the skid steering scheme with two front fixed wheels (working in skid or differential mode) and two rear caster wheels. It is intended to work autonomously on both large-scale and horticultural crops, applying fertilizer, detecting and classifying weeds, and killing weeds either mechanically or chemically [31, 32]. Another robot is Robot for Intelligent Perception and Precision Application (RIPPA), which is a light, rugged, and easy-to-operate prototype for the vegetable growing industry. It is used for autonomous high-speed, spot spraying of weeds using a directed micro-dose of liquid when equipped with a variable injection intelligent precision applicator [33]. Another example is Ladybird (**Figure 4b**), an omnidirectional robot powered with batteries and solar panels that follows the independent steering scheme. The robot includes many sensors (i.e., hyperspectral cameras, thermal and infrared detecting systems, panoramic and stereovision cameras, LIDAR, and GPS) that enable assessing crop properties [34]. One more prototype, very close to commercialization, is Kongskilde Vibro Crop Robotti, which is a self-contained track-based platform that uses the skid steering scheme. It can be equipped with implements for precision seeding and mechanical row crop cleaning units. This robot can work for 2–4 hours at a 2–5 km h<sup>−</sup><sup>1</sup> rate and is supplied by captured electric energy [35].

#### **Figure 4.**

*Pictures of several specifically-designed agricultural platforms. (a) Robot for weed detection, courtesy of T. Bak, Department of Agricultural Engineering, Danish Institute of Agricultural Sciences; (b) ladybird, courtesy of J. P. Underwood, Australian Centre for Field Robotics at the University of Sydney [34]; (c) AgBot II, courtesy of O. Bawden, strategic Investment in Farm Robotics, Queensland University of Technology [31].*

These robots are targeted toward fertilizing, seeding, weed control, and gathering information, and they have similar characteristics in terms of weight, load capacity, operational speed, and morphology. Tools, instrumentation equipment, and agricultural implements are connected under the robot, and tasks are performed in the area just below the robot, which optimizes implement weight distribution. These robots have limitations for use on farmland with substantial (medium to high) slopes or gully erosion. Nevertheless, some mobile platforms are already commercially available. Two examples of these vehicles are the fruit robots Cäsar [36] and Greenbot [37].

Cäsar is a remote-controlled special-purpose vehicle that can perform temporarily autonomous operations in orchards and vineyards such as pest management, soil management, fertilization, harvesting, and transport. Similarly, Greenbot is a self-driving machine specially developed for professionals in the agricultural and horticultural sectors who perform regular, repetitious tasks. This vehicle can be used not only for fruit farming, horticulture, and arable farming but also in the urban sector and even at waterfronts or on roadsides.

Despite their current features, the existing robots lack flexibility and terrain adaptability to cope with diverse scenarios, and their safety features are limited. For example:

**83**

**Table 3.**

Vibro Crop Robotti [35]

*\* P-prototype; C-commercial.*

*Robots designed specifically for agriculture.*

*Unmanned Ground Vehicles for Smart Farms DOI: http://dx.doi.org/10.5772/intechopen.90683*

treatment.

themselves.

these platforms.

**4.2 Wheel-legged robots**

being done in the smart factory concept.

*4.2.1 Structures of wheel-legged robots*

steerable powered wheels as illustrated in **Figure 5**.

• They focus only on orchard and vineyard activities.

• They must be manually guided to the working area rather than freely and autonomously moving to different working areas around the farm.

• They possess no advanced detection systems for weed or soil identification, which limits their use to previously planned tasks related to selective

• They lack dynamic safety systems capable of recognizing or interpreting safety issues; thus, they are incapable of rescheduling or solving problems by

In addition, existing UGVs for agriculture lack communication mechanisms for providing services through cloud technologies, CPS, and IoT techniques, crucial instruments to integrate decision-making systems based on big data analysis, as is

**Table 3** summarizes the diverse robotic platforms, and **Figure 4** depicts some of

The structure of a wheel-legged mobile platform depends on (i) the number of legs, (ii) the leg type, and (iii) the leg arrangement. The feet consist of 2-DOF

*Number of legs*: The minimum number of legs required for statically stable walking is four-three legs providing support in the form of a stable tripod while the other leg performs the transference phase [38]. Combining sequences of leg

AgBot II [32] P 2014 A platform that follows the skid steering scheme with two front

Ladybird [34] P 2015 An omnidirectional robot powered with batteries and solar

Greenbot [37] C 2015 A self-driving robot for tasks in agriculture and horticulture Cäsar [36] P 2016 A remotely controlled platform for temporary, autonomous use

RIPPA [33] P 2016 A light, rugged, and easy-to-operate prototype for the vegetable

fixed wheels (working in skid or differential mode) and two rear caster wheels

panels that uses the independent steering scheme

in fruit plantations and vineyards

growing industry

scheme

C 2017 A self-contained track-based platform that uses the skid steering

**Vehicle Type\* Year Description**

• They are unsuitable for rough terrain or slopes.

• They have ground clearance limitations.

*Agronomy - Climate Change and Food Security*

**82**

**Figure 4.**

*Pictures of several specifically-designed agricultural platforms. (a) Robot for weed detection, courtesy of T. Bak, Department of Agricultural Engineering, Danish Institute of Agricultural Sciences; (b) ladybird, courtesy of J. P. Underwood, Australian Centre for Field Robotics at the University of Sydney [34]; (c) AgBot II, courtesy of O. Bawden, strategic Investment in Farm Robotics, Queensland University of Technology [31].*

examples of these vehicles are the fruit robots Cäsar [36] and Greenbot [37].

urban sector and even at waterfronts or on roadsides.

These robots are targeted toward fertilizing, seeding, weed control, and gathering information, and they have similar characteristics in terms of weight, load capacity, operational speed, and morphology. Tools, instrumentation equipment, and agricultural implements are connected under the robot, and tasks are performed in the area just below the robot, which optimizes implement weight distribution. These robots have limitations for use on farmland with substantial (medium to high) slopes or gully erosion. Nevertheless, some mobile platforms are already commercially available. Two

Cäsar is a remote-controlled special-purpose vehicle that can perform temporarily autonomous operations in orchards and vineyards such as pest management, soil management, fertilization, harvesting, and transport. Similarly, Greenbot is a self-driving machine specially developed for professionals in the agricultural and horticultural sectors who perform regular, repetitious tasks. This vehicle can be used not only for fruit farming, horticulture, and arable farming but also in the

Despite their current features, the existing robots lack flexibility and terrain adaptability to cope with diverse scenarios, and their safety features are limited. For example:


In addition, existing UGVs for agriculture lack communication mechanisms for providing services through cloud technologies, CPS, and IoT techniques, crucial instruments to integrate decision-making systems based on big data analysis, as is being done in the smart factory concept.

**Table 3** summarizes the diverse robotic platforms, and **Figure 4** depicts some of these platforms.
