Trends in the agricultural machinery of the future andhow electric linear actuators can be used
Scientific Whitepaper by Dr David Reiser and Prof. Dr Hans W. Griepentrog

LINAK.COM/BUSINESS-AREAS/MOBILE-AGRICULTURE/

The Department of Process
Engineering in Plant Production
at the University of Hohenheim is
testing the possibilities of robotics
in agriculture with the “Phoenix”
experimental vehicle.
2

Abstract
Today’s agriculture is facing major changes caused by digitisation and automation. This white paper is intended to provide an overview of and summarise current developments and tendencies. The focus is on the use ofelectric actuators and their influence on the development of future machines. Only the application and development in agriculture is considered.
For this purpose, a comparison of hydraulic and electric actuators is first
performed, then current applications of linear actuators and control andregulation concepts are dealt with and the necessary power requirementof current tasks is estimated. The trends of the agricultural machinery of
tomorrow are outlined based on this. Future developments and requirements, digitisation, communication and the future of linear actuators inagricultural machinery and robots are presented here. It is to be expectedthat linear electric actuators will further advance the development of agricultural machinery in the future and enable new potential for optimisation.

This white paper was created on behalf of LINAK GmbH by
the University of Hohenheim.
Dr David Reiser and Prof. Dr Hans W. Griepentrog, University of
Hohenheim - Department of Process Engineering in Plant Production(Agricultural Engineering), Garbenstr. 9, 70599 Stuttgart
3

INTRODUCTION

GeneralAgriculture has always been a driver of innovation of new technologies anddevelopments, especially in Germany. Johnson describes a direct link between
the mechanisation of agriculture and the prosperity of a country1. This is particularly evident in the number of people working in the agricultural sector. In
Germany, the number of people employed in agriculture fell from 22.5% in
1950 to 1.5% today. Despite all this, more food is currently being producedin Germany than ever before2. The average yield per hectare of a wheat field
has quadrupled since 1900 from 1.85 tonnes to 7.64 tonnes in 20173.
The mechanisation and automation of production processes had a particular
influence on the advancement in agriculture4 [4]. According to the German
Federal Statistical Office, 6.4 billion euros were spent on new and highly-automated agricultural machinery in 2017 [2]. This high sum underlines thewillingness of the agricultural industry in Germany to invest in new innovative technology. The requirements with regard to agricultural machinery
have changed over time. Some features of earlier agricultural machines are nolonger in demand today, while new skills are required. Typical changes over
the years included absolute machine size, engine power, comfort, safety andmodern automatic steering and driver assistance systems5.
Digitisation does not stop at agricultural engineering and will continue further in the future. “Deep Learning” and “Internet of Things” (IoT) have beenaround for a long time in agricultural research and are now being used in
the first commercial products. Some examples of this in practice are smart
phone apps for determining plant diseases and weeds6. Automated robotics
solutions can now also be purchased and offer added value for the user (e.g.
hoeing weeds in row crops). Robots in the field offer the opportunity to extend digitisation down to individual plants. Therefore, on the level of a “digital twin”, the development of the plants can be examined even more closely7.

4

1

Δ G. Johnson, “Agriculture and the Wealth of Nations” in Papers and Proceedings of the Hundred and Fourth Annal
Meeting of the American Economic Association, 1997, vol. 87, no. 2, pp. 1–12.

2

Statista, “Landwirtschaft in Deutschland”, 2019. [Online]. Available: https://de.statista.com/statistik/studie/id/6455/
dokument/landwirtschaft-statista-dossier/. [Accessed: 04-Sep-2019]3

P Pascher, U. Hemmerling and S. Naß, Situationsbericht 2018/19 „Trends und Fakten zur Landwirtschaft“. Deutscher
Bauernverband e.V., 20184

M Kassler, “Agricultural Automation in the new Millennium” Comput. Electron. Agric., vol. 30, no. 1–3, pp.
237–240, Feb. 2001

5

J. N. Wilson, “Guidance of agricultural vehicles - a historical perspective” Comput. Electron. Agric., vol. 25, no. 1-2,
pp. 3–9, Jan. 2000.

6

A Kamilaris and F. X. Prenafeta-boldú, “Deep learning in agriculture: A survey” Comput. Electron. Agric., vol. 147,
no. February, pp. 70–90, 2018.

7

A Linz, J. Hertzberg and J. Roters, “„ Digitale Zwillinge “ als Werkzeug für die Entwicklung von Feldrobotern in landwirtschaftlichen Prozessen Material und Methoden” in Lecture Notes in Informatics (LNI), Gesellschaft für Informatik,
Bonn, 2019, pp. 125-130.

With the expansion of digital infrastructure, these technologies will create
new opportunities for food production of the future. After many innovation
cycles in agriculture such as through mechanisation, pesticide development,
mineral fertilisers, plant cultivation and precision farming, digitisation is credited with the potential for the next innovation cycle. It is expected that byadapting and further developing the technology with the help of digitisation,
new optimisation potential in agriculture can be identified and used8. This
includes automation using drones and robots. If you believe forecasts by experts, many swarm-based robots will do the field work of tomorrow in the
future, which will further relieve farmers. An overall and sustainable change
in agriculture will therefore be promoted. Automation is expected to reduce
the size of future machines and tasks will be distributed9/10/11.
However, for the practical use of these machines and robots, the necessary
technology and infrastructure must first be available. The success of digitisation depends heavily on the actuators used. Because only if information
gained through digitisation can be suitably converted into activities and actions can a benefit be generated for the farmer. Currently, the increase in the
resulting data is exponential. Artificial Intelligence (AI) applications require adoubled computing requirement every 3.5 months on average12. This also
increases the costs for data analysis, data management and the necessary
digital infrastructure. This generates a lot of data that is never used to increase productivity. Even if intelligent algorithms generate added value fromthe data, this knowledge must be put into practice. This is only possible withsuitable automation of the processes. Therefore, the success of digitisation
and AI is directly related to robotics and automation. New information obtained through digitisation should be automated, accurate, energy-efficientand user-friendly in actions and recommendations for action can be transferred. Therefore, the requirement arises for independently operating robots
and machines to take as many decision steps as possible for the user, or atleast to support the user in doing so. The mechanics must be able to convert
the finely resolved data and information practically in order to be able to control sections or even perform an individual plant processing. The future lies inthe direct, local application of sensor data, which is supported by cloud-based
information.

8 BMEL, “Digitalisierung in der Landwirtschaft Chancen nutzen - Risiken minimieren”, 2019.
9 S. M. Pedersen, S. Fountas, H. Have and B. S. Blackmore, “Agricultural robots - system analysis and economic feasibility” Precis. Agric., vol. 7, no. 4, pp. 295–308, Jul. 2006.
10 3 B S. Blackmore, HW Griepentrog and S. Fountas, “Autonomous Systems for European Agriculture” in Automation
Technology for Off-Road Equipment, 2006.
11 T Duckett et al., “Agricultural Robotics: The Future of Robotic Agriculture” UK-RAS White Pap., pp. 36, 2018
12 F Müssig, “AMD- CEO Lisa Su schaut in die Halbleiter-Zukunft” heise online, 2019. [Online]. Available:
https://www.heise.de/newsticker/meldung/AMD-CEO-Lisa-Su-schaut-in-die-Halbleiter-Zukunft-4500699.html.
[Accessed: 04-Sep2019]5

Spending in billions of euros
0

3

6

9

Feed

14,2

Tractors, agricultural machinery

6,4

Fertiliser, crop protection

4

Agricultural buildings

3,5

Fuels, combustibles, electricity

3,4

Repairs, maintenance3,3Agricultural services

14,2

Seeds and seedlings
Veterinarian, medication
Other goods and services
Source: Statista Dossier Landwirtschaft ID6477

Current problems in agriculture
Cuts in subsidies, rising production costs, environmental regulations and a bad social image
pose particular challenges for today’s agriculture. In particular, compliance with drinking water and water conservation as well as counteracting bee mortality and decreasing biodiversity
are expectations for agriculture. There are additional demands for the current climate protection plan to achieve a permanent reduction in CO2 in agriculture by more than 30% by 2030.
This will be implemented through savings on fertilisers and fossil fuels13. Likewise, there isincreasing pressure on national politics to enforce Europe-wide guidelines, as the current
amendment to the Fertiliser Ordinance (2019) shows.
Agricultural technology will have to react to such requirements if agriculture does not want tolose its social acceptance. Overall, the multitude of legal regulations is increasing significantly,
making it difficult for individual farmers to comply with all rules and regulations. Future agricultural machinery will therefore have to act more in co-operation and more networked inorder to meet the various increasing demands. Likewise, the energy efficiency and the carbon
footprint of the machines must be optimised. This includes the automatic adaptation andoptimisation of processes, the integration of external sensors and information sources, aswell as the ability to provide and analyse information about the actual process in real time. In
addition, electrification offers new potential savings, which could be used in an even betterway in the future.

612Subject Area
and Structure
In order to limit the scope of this white paper, the focus is on agriculture in
Germany. The focus is on the use of linear movements and actuators for machines in an average German arable farm. The state of the art chapter deals
with the current “actual state” of agricultural machinery and vehicles. The
used technology and control for linear movements and with what purpose
they are used are considered. Machine size, tasks, power and energy requirements are determined and analysed. Current control principles, energy supply
and communication protocols are also described in this chapter. In the following chapter Trends in Agricultural Machinery of Tomorrow, the points of theprevious chapter will be revisited and linked with development and research,
as well as with future perspectives in agriculture. In conclusion, the findings
are summarised and evaluated.

7

STATE OF THE ART FOR LINEAR ACTUATORS IN AGRICULTURE

Hydraulic and Electric Actuators
Currently, linear motions are mainly regulated by hydraulic cylinders in agricultural machinery. Typical examples are the front and rear hitch of the tractor.
The big advantage of hydraulics is that high forces can be generated withspace-saving actuators. These are also very simple in their basic structure.
They consist of a few individual parts and can therefore be produced and repaired cheaply. The additionally required components such as the pump andthe oil tank can be flexibly arranged on the machine. Another advantage isthe simple control, which is implemented via the oil pressure and a suitable
control valve. Likewise, hydraulic systems have a damping effect that can absorb high force peaks. Due to the flexibility of oil, hoses and the pump, theactuators can yield counteracting forces without risking a destruction of themechanism. Disadvantages are the necessary hoses or lines, which must beplaced on the actuator in the machine. These bulky hoses can affect the flexibility of the design and the mechanical properties of the device. This resultsin high maintenance, especially in moving systems. Theoretically, the hosesof mobile construction machinery should be completely renewed every six
years, which is hardly implemented in practice13. Similarly, contamination of
the environment with oil is a problem, as actuators, ports and couplings may“leak” or connections may be leaking. In practice, oil hoses can also burst,
which can lead to an emptying of the entire oil supply (usually over 50 litres)of the machine and represents a safety risk for the user. The precise control
with hydraulics is very complex, since influencing factors such as hysteresis,
seal wear and temperature change the result of the control.
These disadvantages mean that more is being placed on electric actuators.
This form of actuator is on the rise in areas where contamination with oil
is undesirable and unacceptable. Even in areas where low power but highprecision are required, electric actuators have advantages and are already being used today. Electromechanical actuators usually use a ball or roller screw
drive, which is driven by a locally mounted electric motor. Since the entire
drive system is installed in the actuator, this is much more flexible and requires
only a matching power and control line to act. Although electric actuators

13 DGUV, “Hydraulik-Schlauchleitungen - Prüfen und Auswechseln” no. 03, 2018.

Hydraulic cylinder

8

Electric actuatorHYDRAULIC ACTUATORSELECTRIC ACTUATORS

Operating principle:
A pump removes oil from a storage tank andcreates pressure in the line. The pressurised oil
is introduced into the hydraulic cylinder using
a control valve or returned to the oil storagetank. The resulting force is determined by oilpressure and cylinder size.

Operating principle:
An electric motor generates a rotating motion,
which is transmitted into a linear motion via
a mechanical gear. The energy is supplied
via a power line to a power source such as a
generator or an alternator.

+ High forces+ High acceleration+ Lower costs+ High repeat accuracy+ High robustness+ Accurate and easy control+ Low actuator weight+ Cable instead of hoses

÷ High maintenance cost

+ Simple digital control÷ Hysteresis and seal output+ Low maintenance÷ Danger of pollution+ High energy efficiency

÷ Bulkiness through hoses

÷ Limited strength÷ Operator protection, working withhigh pressures

÷ Higher costs
÷ No damping property
÷ Higher actuator weight

are heavier in comparison to their hydraulic partner since they require a motor
and transmission, they have the advantage that they usually have a higher
power range and offer a much higher positioning accuracy. In addition, thepump and pipes are omitted, which increases the flexibility of the drives in
the configuration. The fast response, the precision and the repeatability allow
significantly more precise control and regulation than can be achieved withhydraulic systems. In most cases, however, the costs for the electric drives
are slightly higher than those of the hydraulic competitors. The table above
explains the basic principles of hydraulics and electromechanics and their advantages and disadvantages.

9Linear actuators in agricultural
machinery and attachments
The following tasks typically occur in an arable farm over the year:• Tillage• Sowing• Stand care (weed and pest control, fertilisation)• Harvest• Transport / storage

These tasks are implemented in the combination of tractors with suitable attachments or with a specially made self-propelled machine such as a combine
harvester. Most of the attachments are only used for a small amount of timeeach year, which means that they should save the user money. For example,
the cost of deployed mineral fertilisers is many times higher than the initialcost of the spreader itself. Large and expensive self-propelled machines suchas combine harvester or field chopper are only purchased by larger companies. For medium-sized and small businesses, these are booked and provided
through machinery contractors or machine pool. The individual tasks of anarable farm and the typical tasks and optimisation parameters are described
below.
Tillage (T): In the case of tillage, the focus is on the uniform and, dependingon the target, specific processing of the area. Typical optimisation parameters
are the processing quality (e.g. crumbling and soil loosening), the minimisation of the energy input and the optimisation of the speed. In addition, soil
erosion due to processing adapted to the site must be minimised. In practice, the arrangement of the processing equipment into its position, angle
and depth is set manually. The depth guidance is controlled mechanically via
rollers and trailing wheels. In order to ensure that the tools ease off in theevent of obstacles (e.g. stones), the tools usually have spring suspension. The
spring strength, the tools and the arrangement are manually adjusted to thespecific location. Only the lifting and digging is controlled by the rear powerhitch of the tractor. However, there are first machines with “Section Control”
for the insertion and removal of individual ploughshares and the automatic
adjustment of cutting widths and row spacing. Likewise, the automatic andsite-specific adjustment of the tool pressure is possible.
Sowing (S): When sowing, the influencing factors such as the sowing depth,
the row spacing and the singling or even distribution of the seed are important. If these are guaranteed, the focus will be on a conventional attachment
to allow more area to be processed in less time. Standard machines usually

10

only allow a manual parameter setting. Changes in sowing strength are now
also automatically adjustable on new machines. Tillage is often combinedwith the sowing. The no-till and strip-till techniques are interesting variations.
The latter works only on the area of sowing and leaves the rest of the field
untouched. Here, too, the desire is to be able to flexibly control the influencing factors specified without having to carry out a lot of manual adjustment
work.
Stand care (SC): All work which serves the preservation and the care of thestand after its establishment is summarised under stand care. This includes
fertilisation, weed control, and pest and disease control. Different requirements arise depending on the task and the stock. Basically, it is important to
act in a particularly plant-friendly manner and to carry out the process optimally and precisely. Precision agriculture offers the greatest potential here.
On the one hand, this is due to the possible material and cost savings and on
the other hand to the legal regulations which mainly regulate this area of agriculture (plant protection regulations, fertiliser regulations, water protection,
insect protection, etc.). The variable application of mineral fertiliser was oneof the first practical precision agricultural applications. Other examples areactive field sprayer section control and control of hoeing equipment. In addition, this area covers the largest period of time over the year. While sowing
and harvesting have only small working windows, stock management must
be carried out and adapted over several months (in small distributed time
windows). Likewise, correct stock management improves yield and quality
by supporting the stock in its development (e.g. through weed control, pest
control and fertilisation).
Harvest (H): Basically, it is important to harvest as much area and crop as
possible in a short window of time/weather when harvesting in arable farming. In addition, the harvest should be collected and transported in good quality. For these reasons, harvesters are the largest and most expensive machines
in agriculture. For some time, these have already reached the maximum permitted sizes for road traffic. The main focus for development in recent years
has been on further optimising crop quality (sensor-assisted machine setting)and minimising harvest losses. Further focal points are the reduction of damage caused by ground pressure and the use of driver assistance systems. At
harvest time, some of these machines are operated around the clock in orderto recoup the high machine costs. For this reason, higher demands are placedon durability and robustness (ultimately reliability) than in other areas.

11Transport / Storage (TS): Especially during harvesting, transportation is essential for the smooth running of a harvest chain. Usually several vehicle combinations are required to transport the harvest from the harvesting machine.
There is potential for optimisation in approach, overloading time, overloading
position and loading quality. For example, when chopping maize, the tractor
with loader wagon must be able to drive parallel to the forage harvester
during the overloading period so that no crop is lost. This can partly alreadybe done with sensor support, e.g. by means of a camera. The “machine tomachine” communication for controlling the tractor speed is also already implemented during the overloading period. Ingredient measurements usingnear-infrared spectroscopy systems can now be used to determine the dry
matter and nutrient content on a site-specific basis. This can be used for billing and storage optimisation.
Currently, many parameters, especially for attachments, are only manually
adjustable and cannot be manipulated via actuators. The direct automatic
manipulation of these parameters using sensors and actuators offers highoptimisation potential and an increase in the ease of use for machines and attachments of the future. The following table lists some examples of machines
for individual work steps and evaluates the influencing variables according topower requirement, setting frequency, optimisation potential and cost savings for the farmer. For the evaluation, these were each divided into threeclasses (high/frequent, medium, low/rare). The following guide values wereused to determine the classes:
The table shows that, while there are many possible controls in current
machines, the usage potential is very different. In most cases, the greatest
benefit is the increased comfort and faster setting of the machineparameters. Process optimisation and direct cost savings are possible if thequality of the process can be improved by precise control. Precise control can
reduce the loss of material (e.g. spray, fertiliser, seed) and crop. This effectcan be further enhanced by autonomous machines and robots.

Power requirement:”high” - over 700 W; “medium” - 700-300 W; “low” - under 300 W
Setting frequency: “high” - continuous; “Medium” - 1x per headland; “Low” - 1x per operation
Optimisation potential: ”high” - over 5 %; “medium” - 5-1 %; “low” - under 1 %12

Selected examples of process parameters with anestimate of power requirement, setting frequency
and optimisation potential

MachineCause variable

Power requirement

Adjustment
frequency

Optimisation potential/
cost savings

T

Cultivator, disc harrow

Machining depth

mediuminfrequentlow

TPloughPull point
adjustment

highinfrequentlow

TPloughWorking width

mediumoften

mediumS

Single grain sowing
machineSingling

low

infrequentmediumS

Single grain sowing
machinePlacement depth

mediuminfrequentmediumS

Seed drill

Track marker control

mediummediumlow

SSingle grain sowing
machineCoulter pressure

mediumoften

mediumSC

Field sprayer

Boom control

mediumoften

mediumSC

Weed hoe

Cross adjustment

medium

often

high

SC

Weed hoeWorking width
aggregateslowinfrequentmediumSC

Weed harrow

Intensity (incline oftines)

low

often

high

SC

Centrifugal spreader

Distribution

lowmediumhighSCCentrifugal spreader

Dosage

low

often

high

H

Combine harvester

Adjustment ofcomponents

mediumoften

mediumTS

Overload control

Quality

low

often

high

Process

13

Control and regulation concepts,
power requirement
The communication between different devices in agricultural machinery isvery uniform, so almost all machines use the CAN bus protocol (SAE J1939). It
serves as a machine bus system and in a special variant for communication between the machine and attachments, or terminals and sensors, the so-called
ISOBUS (ISO 11783)14. These protocols are supplemented with proprietarysystems, e.g. for the transmission of video signals or sensor data. Standard
interfaces such as USB and RS232 are still used for the integration of external
data (e.g. georeferenced map material). New models can already access external data via WLAN or mobile network. These are not used for direct control
and regulation of the machines, but serve as a transitional interface between
sensors, servers and “cloud services”.
The advantages of the CAN bus system are the wide distribution and the possibility of message prioritization. It is also possible to track whether a signal
has been successfully transmitted to the receiver. However, the data rate islimited to approx. 1 Mbit/s, which limits the transmission of video and sensor
data. For this reason, only information, pre-processed signals and commands
are usually transmitted which generate low data rates and do not lead to an
overflow of the bus system. In addition, other protocols are in use for the datatransmission of sensor information such as from reverse cameras. However,these protocols have not been used for direct control so far, but only for additional monitoring for the driver.
The standard power supply from the tractor alternator is 14 V, which is basedon the charging voltage of the 12 V nominal battery voltage used. This voltage can be obtained directly from the connectors and usually supplies a rated
current of 200 A via the alternator. The sockets are designed for a power ofup to 60 A, which enables a power transmission of 840 W (= 14 V*60 A)15.
For higher motor powers, the energy supply of the machine must be adjusted.
Since a higher power consumption of the actuators requires a higher current

14 Δ S. Paraforos, G. M. Sharipov and H. W. Griepentrog, “ISO 11783-compatible industrial sensor and control systems
and related research: A review” Comput. Electron. Agric., vol. 163, no. June, pp. 104863, 2019.
15 T Agrar, “Schlepper unter Strom” Top Agrar, 2010. [Online]. Available: https://www.topagrar.com/technik/aus-demheft/schlepper-unter-strom-9694009.html. [Accessed: 23-Aug-2019].

14

CAN bus protocol
The CAN bus protocol SAE J1939
is often usedstrength, the cross-section of the cables must also be increased as the power
consumption increases. This results in increased costs for the plug connections and the risk of contact corrosion16. One way to obtain more electrical
power is to use additional PTO generators. They use the PTO shaft of the
tractor as the generator drive to provide enough energy for the electric drives.
The integration of actuators can already be done very easily using control
signals and power supply. Control can be via standard CAN controllers, CAN
controls or the tractor terminal. The integration of sensors in the drives makes
maintenance and servicing easier. Malfunctions can be detected and rectified
via remote maintenance services. The replacement of entire actuators makes
it possible to carry out repairs quickly and easily.

16 G. Edwards, D. Bochtis and C. G. Søresen, “Multi-machine Coordination: Scheduling Operations based on Readiness
Criteria and using a modified Tabu Search Algorithm” in 4th IFAC Conference on Modelling and Control in Agriculture,
Horticulture and Post Harvest Industry, 2013, pp. 191–195..

15

TRENDS IN THE AGRICULTURAL MACHINERY OF TOMORROW

Machine sizes and automation level
In the near future, many farmers will probably continue to rely on existing
technology and only slowly use new systems such as robotics, remote sensing using drones or cloud-based IT structures. However, social change canvery soon lead to a situation in which only robotics can maintain economic
viability. Due to the fact that chemical pest and weed controls may soon berequired by law, more crossings with chippers or similar will be necessary in
the future17. If the trend continues and the effectiveness of a farmer must
increase further, this cannot be achieved by even larger machines, but only bypartial automation and optimisation of the tasks.
The current machines have reached the maximum size to be driven and transported on public roads. It is therefore to be expected that in the future themachines will not be any larger. When robots take over the tasks, the absolute
size of the units only depends on the technical possibilities such as the range,
the running time and the controllability of the machines. It is to be expectedthat soil cultivation requires the highest power requirement and therefore
defines the lower possible limit of the machines. However, miniaturisation will
not work up to the level of a garden mower, as the necessary power, running
time and terrain mobility can only be guaranteed at a certain size.
Robotics as a solution is already offered for sale by several companies (e.g.
Naio and Agrointelli). These robots can work autonomously, but must be supervised by the user. In order to work with these machines, the fields must
be adapted to the characteristics of the robots. This includes e.g. planningsuitable routes and providing the infrastructure (e.g. electricity, mobile internet). Purely battery-powered and electrically operated machines are withinreach. At the moment, the range of conventional fuel driven machinery is still
significantly higher than that of their electrified competitors. However, there
are already applications where complete electrification can be implemented.
This mainly concerns small plots which are well integrated into the local infrastructure. Basically, it can be assumed that the switch to electric motors willlead to an increase in the efficiency of the machines18. However, it is not yet
possible to predict how energy storage can be meaningfully implemented,
whether with batteries, hydrogen or other synthetic fuels.
It is also to be expected that automation will not only enable machines androbots to copy conventional technology and replace the driver, but also adapt
the tools to the size, speed and range of the robots. This depends on the task,
power and required safety of the machines. In addition, the use of robots
creates new working windows, as the machines can theoretically work continuously, even at night.

17 G. Edwards, D. Bochtis and C. G. Søresen, “Multi-machine Coordination: Scheduling Operations based on Readiness
Criteria and using a modified Tabu Search Algorithm” in 4th IFAC Conference on Modelling and Control in Agriculture, Horticulture and Post Harvest Industry, 2013, pp. 191-195.
18 G. P. Moreda, M. A. Muñoz-García and P. Barreiro, “High voltage electrification of tractor and agricultural machinery– A review” Energy Convers. Manag., vol. 115, pp. 117-131, 2016.

16

Working at night offers considerable advantages for weed, pest and disease
control, which can be better harnessed with robotics. Likewise, the probability of coming across people at night is lower, which could prevent serious
accidents. The autonomous performance of simple activities at night could
also improve the effectiveness between man and machine. For example, thefarmer could send the final instructions to the machine at the end of theworking day to check the quality of the work the next morning. In order towork effectively, the fields must be adapted to the characteristics of the robots. This includes e.g. the pre-planning of suitable paths, the calibration offield boundaries and the provision of infrastructure (e.g. power supply andmobile internet).
Autonomous driving in agriculture is already possible and feasible today, but
it is not without risks. In the future, there will always be a certain probabilityof malfunctions caused by incorrect operation, external influences, software
errors or faulty sensors and mechanics. Therefore, the implementation will be
determined by the case law19. To a certain extent, the legal framework can betransferred from the field of autonomous driving to agriculture. The current
legal situation is such that the protection of people always has priority. Liability is divided between the driver, the owner and the manufacturer20. A clear
distinction is made here between the reasons why an accident could occur
and the question of guilt. The case that there is no driver is not yet included
in case law. Therefore, automated systems are legally covered, but autonomous systems are not. It is therefore likely that in the near future only systems
monitored by a user will be available. This means that the user must takethe machine into the field and not allow it to travel autonomously across thefield. The most conceivable solution is a small-scale implementation of machines that have enough power to work and do not cause too much damage
in the event of a malfunction. It is also possible to monitor several machines
using suitable telemetry systems. A major advantage of agriculture is that
agricultural areas are subject to a legal prohibition of access during cultivation(example: Baden-Württemberg: Section 44 of the State Nature Conservation
Act). However, first precedents need to be clarified as to how this will affectcase law.

19 B Gogarty and M. Hagger, “The Laws of Man over Vehicles Unmanned: The Legal Response to Robotic Revolution on
Sea, Land and Air” J. Law, Inf. Sci., vol. 19, pp. 73-145, 2008.
20 Daimler, “Automatisiertes und autonomes Fahren. Rechtlicher Rahmen”,2019. [Online]. Available: https://www.
daimler.com/innovation/case/autonomous/rechtlicher-rahmen.html. [Accessed: 27-Aug-2019].

17

Electric actuators are also used in
the “Phoenix” test vehicle.
18Requirements for actuators such as
power, control and interfaces
Automated and autonomous machines require intelligent sensors and actuators. Actuators of the future will therefore not only be pure controllers, butwill also provide feedback on their actions. This includes characteristics suchas position, action, performance, load and cycles. If this information is placedin the right context, additional added value can already be generated withthis information. Therefore, in the future, the load and wear could be independently recognised and evaluated in intelligent actuators. Maintenanceand service could be carried out efficiently and with little effort. The absolute
position of the actuator must always be known for automated processes. An
intelligent action of the actuator is also desired, so that e.g. a resistance ora blocking of the actuator is automatically detected and reported and thecontroller can react to it. The information that is collected, such as force andinteraction, can be used to determine additional information about the environment when the data is placed in the right context. This information can beused, for example, to optimise machining or even to plan the next work steps
in order to minimise machining peaks. Similar to human workers, autonomous robots will need haptic feedback systems in the future, ideally directly
integrated into the actuators. This makes it possible to “feel” the environment and actively interact with it.
In the electrification of cars, high-voltage motors have long been used, e.g.
the prototype of a wired agricultural robot of the GridCon project, whichworks with a voltage of 700 V21. This enables significantly higher performance, but also increases the risk of injuries during repair and maintenance.
One solution is to switch to a 24 V on-board power supply system, which isused in lorries and construction machinery. This results in a doubling of thetransferable power. In order to be able to work in a “touch-safe” area, it ispossible to extend the system to a nominal voltage of 48 V (possibly 42 V tokeep the charging voltage below 50 V). At 60 A a usable power of 2.8 kW
already results here. This power is already more than sufficient for most tasks.
This would also be sufficient to replace most linear hydraulic cylinders withelectric actuators. With the miniaturisation and automation of the machines
it is to be expected that the required performance will decrease.

21 BMWi, “Gridcon Project”, 2019. [Online]. Available: http://www.gridcon-project.de/. [Accessed: 28-Aug-2019].

19

Digitisation of the machines
The future machine will develop into a “smart device” by continuously recording measurement data with the aid of sensors. The main objective of
automated machines and robots in agriculture is to understand and react tothe behaviour of the environment and plants. This is made possible by intelligent actuators. This increases the required data rate, which also indicatesthe limits of the current protocols for internal communication with actuators.
Since the exchange of image material from camera sensors is also best sent
via the same interface, the implementation with CAN bus is not realistic dueto the maximum possible data rate of 1 Mbps. Alternatives include Flexray,
Automotive Ethernet, MOST bus or EtherCAT, which all enable higher transfer
rates. It is also possible to install several bus systems on the same device andto divide them according to safety-relevant parameters and data transmission
rates. In modern passenger cars, more than 150 control devices are alreadynetworked with each other and there will certainly be more in the future.
Agricultural machinery is also being assembled with an increasing numberof individual components, control units and actuators. Currently, some automotive manufacturers rely on the Flexray Bus. It is possible that this will
also become established in agriculture due to the higher transmission rate of
10 Mbps. However, in the next 5-10 years there will probably not be muchchange in the common protocols J1939 and ISOBUS for the classic tractor

20

combination. As product life cycles in agriculture are significantly longer thanin other industries, the change will be slow.
It is different with autonomous robots. Since the communication between
the attachment and the machine is not in the foreground here, an isolated
solution can be implemented. The main possible approaches are industrial
automation and the use of intelligent sensors to keep the data rate between
the individual components as low as possible. A robot is more likely to be a“computer on wheels” than a conventional “tractor with computer”.
The service of the future will differ from the practice of today. Working hours
for repairs will become more and more expensive and therefore unprofitable.
Therefore, the trend is to replace entire parts and components instead ofrepairing individual details. This will also be the case more and more frequently in agricultural machinery. It is also possible to use new technologies
such as virtual reality and remote maintenance. A central service technician
gives instructions to the user to carry out the repair with their instructions.
By determining the service life and load of drives, a new part can be ordered
and delivered even before the drive fails. Therefore, breakdown risks can be
minimised in advance.

21

The future of linear actuators in futuremachines
Some tasks will also be implemented by conventional machines with drivers
in the near future. It is therefore to be expected that no fully autonomous
combine harvesters will drive across the fields for the time being. The reasonsfor this are the already high efficiency of harvesting machines of today, safety
and the low share of labour costs in the total costs. Here solutions with telemetry approach are possible, so that a driver controls and cares for a fleet
of vehicles. In such cases, the use of linear actuators serves to ensure flexible
and user-friendly operation. Likewise, the expert knowledge of a driver canbe transferred to a downstream remote-controlled vehicle or a less experienced driver. In addition, occurring forces can be determined via the current
consumption of the actuators and used for additional analysis of the process.
The situation is different in tasks such as tillage, sowing and maintenance. It
is to be expected that semi-autonomous systems will be used very soon. It is
not yet clear how flexible the machines and robots of the future will be. Either
they are specialised in one task or they are generalist machines which can
carry out several tasks throughout the year. Generalist machines must offer
the user as much variability as possible. Specialised machines are operated bylarge companies and contractors in order to recoup the costs. Contractors can
specialise in individual tasks and therefore use high machine costs profitably.
This also changes the requirements for built-in linear actuators.
It is to be expected that the miniaturisation of the machines will make hydraulics less relevant as lower power levels are required. In a fully electrified
machine, it makes more sense to work with electric linear actuators if thepower range permits. Therefore, the power loss can be reduced by the energy
conversion. In addition, the sensor information can be used in the future togain added value from the automation of individual settings, e.g. when theactuator position is logged along with the position, it can be used to automatically control the machine. The automation of machines and robots requires
significantly more adjustment options than is currently the case with conventional machines, as the farmer previously had to make the adjustments manually. In the future, the machine should be able to adjust itself independently,
but this requires more actuators.

22

CONCLUSION
The implementation of autonomous field management will trigger a disruptive change in agriculture over the next few years. Robots will probably only
be used in parallel with existing systems and machines and then graduallytake on new tasks. In addition, driver assistance systems in existing agricultural machinery will continue to be expanded. The start of robotics will presumably be the use in inventory maintenance and will then be extended to othertasks. Autonomous robots will become economically interesting as soon as
the costs for the machines are affordable and the effort is worthwhile for the
farmer or contractor to transport the machine to the field and remove it again
after the work is done. A possible scenario could be that the farmer has several machines, all of which can be transported on a trailer. The tasks are definedand planned in advance by the farmer based on weather and remote sensing
data. The machines are then taken to their working area. On a large scale, thework can be taken over by several machines of the same construction in orderto provide sufficient power. The conclusion is therefore that the machine sizemust be as small as possible and as large as necessary.
The electrification of agriculture will be socially demanded in the future andwill initially be implemented in agricultural robotics. In an electrically operated
system, which should work in a minimally invasive way, it makes little sense
to rely on hydraulic drives, if the required power can also be provided byelectric actuators. By using higher voltages, the power range of existing linear
actuators can be extended, therefore offering a wider range of applications.
Intelligent, linear drives will have an important role in the implementationof automated systems in the future. They will create opportunities to collectdata that is not yet considered today. This will expand the future agricultural
machine into a “smart device”, which will continuously generate data about
the process, with which new optimisations will be possible in the future.

Photo credits
Cover photo: ©Yuriy Kulik - stock.adobe.com, page 8 (hydraulic cylinder): Ramona Heim, page 20-21 Illustration: © muchmania, © j-mel; Bild: © jimbophotoart, All other images: LINAK GmbH, LINAK A/S

23

More information about TECHLINE:
LINAK.COM/BUSINESS-AREAS/MOBILE-AGRICULTURE/

LINAK® accepts no responsibility for possible errors or inaccuracies in catalogues, brochures, and other material. LINAK reserves the right to change its products without prior notice. LINAK cannot guarantee product availability andreserve the right to discontinue the sale of any product. User is responsible for determining the suitability of LINAK products for a specific application. All sales are subject to the ‘Standard Terms of Sale and Delivery’, available on
LINAK websites.
LINAK and the LINAK logotype are registered trademarks of LINAK A/S. All rights reserved.

LINAK.COM
24

Innovation is in our core. We have thecuriosity to think innovatively and thepower to make it real on all levels.

We are responsible in what we do –towards customers, employees andenvironment. Creating trust and taking
care is in our DNA.

From global presence to local
understanding. We believe inworld-wide support and being
close to our customers.

MA M9-02-812-A - 2020.12

Built on state-of-the-art technologies
and refined processes by competentpeople, you can expect the same quality
worldwide.