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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>C. Fromme. A Semi-Autonomous Robot for Stripping Paint from Large
Vessels. The International Journal of Robotics Research</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.1109/IDAACS.2017.8095091</article-id>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Yuriy Kondratenko</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Kai Wang</string-name>
          <email>kevin.wangkai92@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Oleksiy Kozlov</string-name>
          <email>kozlov_ov@ukr.net</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Anatolii Shevchenko</string-name>
          <email>a.i.shevchenko@ipai.net.ua</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>01001</institution>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Institute of Artificial Intelligence Problems of MES and NAS of Ukraine</institution>
          ,
          <addr-line>11/5 Mala Zhytomyrska str., Kyiv</addr-line>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Petro Mohyla Black Sea National University</institution>
          ,
          <addr-line>10 68th Desantnykiv str., Mykolaiv, 54003</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>Yancheng Polytechnic College</institution>
          ,
          <addr-line>No. 285, South Jiefang Road, Yancheng, Jiangsu Province, 224005</addr-line>
          ,
          <country country="CN">China</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2017</year>
      </pub-date>
      <volume>1</volume>
      <issue>1</issue>
      <fpage>27</fpage>
      <lpage>28</lpage>
      <abstract>
        <p>This paper focuses on the advancements in mobile robotics, specifically on universal robotic platforms that have versatile applications in different technological environments and settings within industrial facilities. These platforms exhibit the capability to navigate complex terrains on horizontal surfaces and even ascend vertically on walls and ceilings, making them autonomous and adaptable tools for performing intricate operations in challenging and hazardous areas. The primary challenge addressed in this research pertains to the precise control of adhesion when these robotic platforms traverse inclined planes. To tackle this issue, the authors have developed and analyzed an intelligent adhesion control system. This system harnesses the principles of neural network control to stabilize the required adhesion force for safe and efficient platform movement across varying surface inclinations. The obtained computer simulations results confirm the high effectiveness of the proposed intelligent system. Mobile robotics, universal robotic platform, intelligent adhesion control, neural network</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>control system, NARMA-L2 controller, computer simulation</p>
    </sec>
    <sec id="sec-2">
      <title>1. Introduction</title>
      <p>
        The integration of robotic systems and complexes across diverse sectors of human activity has
experienced significant growth in recent years [
        <xref ref-type="bibr" rid="ref1 ref2">1, 2</xref>
        ]. Nowadays, robots of various types play a pivotal
role in numerous processes, spanning from closed production cycles in heavy industries and
metallurgy to customer service and cargo delivery. The adoption of robotic solutions yields
substantial advantages, notably the elimination of costly human labor, a significant boost in
productivity, accuracy, and operational speed, as well as a reduction in risks to human life and health
when executing tasks in hazardous and detrimental environments [
        <xref ref-type="bibr" rid="ref3 ref4">3, 4</xref>
        ]. Furthermore, the utilization
of robots helps mitigate errors arising from operator fatigue and human factors [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ].
      </p>
      <p>
        In the monograph of T. Braunl [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] the mobile robots and robotic complexes are singled out as a
distinct and widely utilized class of robotic systems. Also, the studies of researchers O. Tosun et al.
[7] confirm that these systems excel in tasks such as monitoring, inspection, reconnaissance, as well
as facilitating the
      </p>
      <p>movement of equipment and tools to execute labor-intensive operations in
challenging and inaccessible locations. Their true effectiveness is witnessed through their ability to
operate in fully automatic modes [8, 9]. For instance, mobile robots developed by M. Sorour [10] and
B. Ross et al. [11] have proven to be highly effective in painting tasks as well as paint removal from
various surfaces. Moreover, notable advancements have been made in the research of Z. -W. Mao et</p>
      <p>2023 Copyright for this paper by its authors.
al. [12] at the development and successful application of mobile welding robotic complexes capable
of autonomously tracking and performing large fillet welding seams in narrow spaces. Additionally,
robots proposed by D. Souto, et al. [13] and M. Cardona et al. [14] for complex cleaning and
inspection of diverse objects' surfaces have gained widespread usage.</p>
      <p>As the studies of such researchers as M. Karimi, et al. [15], and V. Mazur [16] show, the universal
mobile robotic platforms (UMRP) exhibit even higher levels of efficiency. Their modular structure
enables the integration of various propulsion systems and diverse sets of technological tools, enabling
them to undertake a wide range of tasks across different environments and conditions. These
platforms demonstrate their adaptability on horizontal surfaces with intricate terrains, underwater
environments, as well as vertical and inclined surfaces of various types [17]. Consequently, their
versatility contributes to a considerable increase in task performance speed and a reduction in the
costs associated with diverse technological operations [18]. Nevertheless, the development of such
UMRPs presents considerable challenges for designers in creating highly efficient intelligent control
systems. These control systems must possess a modular structure to automate the control processes of
diverse propulsion devices (for moving above water and underwater, as well as maneuvering on
horizontal and inclined surfaces) and various working tools (for welding, monitoring, inspection,
painting, cleaning, etc.). As recent studies show, it is most advantageous to develop such control
systems based on the methods and approaches of artificial intelligence [19, 20]. For instance, fuzzy
control systems prove highly effective in navigating different types mobile robots capable of moving
on inclined surfaces [21]. Moreover, researchers M. Algabri, et al. [22] proposed an optimized fuzzy
controller for mobile robot navigation that allow avoiding random obstacles when moving in
unknown environments. Neural network (NN) control is also widely utilized, which is confirmed by a
number of its successful applications [23, 24]. In particular, R. Garcia-Hernandez, et al. [23]
developed methods of decentralized neural control and successfully applied it to various mobile
robots. Besides, H.A. Mayer [24] designed an approach to ontogenetic teaching of mobile
autonomous robots with dynamic neurocontrollers.</p>
      <p>Significant emphasis should be placed on the adhesion force control system (AFCS) when the
platform navigates across different types of inclined surfaces. This system holds paramount
importance as it directly influences the safety of movement on inclined and vertical surfaces.
Moreover, precise control of the adhesion force can greatly enhance the overall efficiency of the
motion control system by enabling the optimal distribution of loads. Thus, the development of an
intelligent system for precise control of the adhesion force will solve one of the important automation
tasks of the universal mobile robotic platform.</p>
      <p>The primary objective of this research is to develop and investigate an intelligent system for
stabilizing and automatically controlling the adhesion force of a universal mobile robotic platform.</p>
    </sec>
    <sec id="sec-3">
      <title>2. Structure of the Generalized Hierarchical Control System for the UMRP</title>
      <p>
        Due to the intricate and multifaceted nature of the universal mobile robotic platform, a hierarchical
control system with multiple levels is essential. The hierarchical multi-level control approach
encompasses distinct levels, including the highest, strategic, tactical, and executive levels of control.
The highest level entails the human operator and the human-machine interface [25]. At this level, the
operator is responsible for making informed decisions regarding specific technological operations,
tasks, movements, or maneuvers of the UMRP. These decisions are based on comprehensive
assessments of the environment, prevailing conditions, external disturbances, and other relevant
factors [
        <xref ref-type="bibr" rid="ref7 ref8">26, 27</xref>
        ]. Furthermore, in order to facilitate decision-making, the operator can utilize
embedded simulation models to conduct preliminary simulations of specific situations. These
simulations enable the operator to predict the behavior of the UMRP as well as the state of the
environment, aiding in informed decision-making processes.
      </p>
      <p>
        At the strategic level of control, upon receiving specific commands or control goals from the
highest level, it is necessary to plan the sequence of technological operations, tasks, or movements.
This involves transforming them into a series of elementary actions or subtasks. Depending on the
nature of the operation, various control algorithms can be employed at this level [
        <xref ref-type="bibr" rid="ref7">26</xref>
        ]. The strategic
level then generates commands for the tactical level, which is responsible for executing specific
actions or basic operations. The primary objective of the tactical control level is to convert the
commands received from the strategic level into control programs that dictate the coordinated
functioning and movement of the executive mechanisms and actuators at the executive level of
control. These programs define sequences of desired values for the generalized controlled coordinates
of the UMRP's primary executive mechanisms [
        <xref ref-type="bibr" rid="ref7">26</xref>
        ].
      </p>
      <p>
        The executive level of control comprises the executive mechanisms, actuators, and the sensory
system. Additionally, it includes automatic control subsystems that, through appropriate control
inputs, determine the desired values for the platform's generalized controlled coordinates received
from the tactical level [
        <xref ref-type="bibr" rid="ref7">26</xref>
        ]. The sensory system plays a crucial role in providing feedback and
gathering comprehensive information about the state of the UMRP and its surrounding environment.
      </p>
      <p>Fig. 1 illustrates the basic structure of the generalized hierarchical control system for the UMRP,
with the following notations being used: HMI is the human-machine interface; CATO1, CATO2, …,
CATOl are the control algorithms of the 1st, 2nd, …, lth technological operations; CMPD1, CMPD 2,
…, CMPDn are the control modules of the 1st, 2nd, …, nth propulsion devices; CMTT1, CMTT 2, …,
CMTTm are the control modules of the 1st, 2nd, …, mth technological tools; USS is the vector of
sensory system outputs; USL is the vector of control signals for the strategic level; UTL is the vector of
control signals for the tactical level; UEL is the vector of control signals for the executive level; XR is
the vector of controlled and technological variables of the UMRP.</p>
      <p>Within this hierarchical control system, at the highest level the operator utilizes a dedicated
human-machine interface to relay control signals USL to the strategic control level, while also
receiving signals USS regarding the platform's state and environmental conditions from the sensory
system.</p>
      <p>In turn, the strategic level incorporates a collection of l control algorithms (CATO1, CATO2, …,
CATOl) designed to facilitate control over a range of technological operations (such as inspection,
ultrasonic diagnostics, welding, painting, rust removal, cleaning, etc.) achievable with the robotic
platform. Furthermore, different combinations of propulsion devices and technological tools available
on the mobile platform can be employed for executing these technological operations. Additionally,
the control system allows for the inclusion of new control algorithms at the strategic level to
accommodate novel types of technological operations.</p>
      <p>To facilitate direct control over diverse propulsion devices (such as wheeled, caterpillar, propeller,
gravity-based, walking, etc.) and technological tools (including manipulators, video cameras, welding
machines, cleaning cutters, and more) during the execution of various operations, the system
incorporates corresponding control modules (CMPD1, CMPD2, …, CMPDn, CMTT1, CMTT2, …,
CMTTm) at the tactical control level. When introducing new propulsion devices or technological
tools to the UMRP, it is necessary to design and integrate the relevant control modules into the
system's tactical control level beforehand. These control modules, possessing a complex structure, are
responsible for the coordinated control of all executive mechanisms, drives, and actuators associated
with specific propulsion devices and technological tools. Lastly, dedicated stabilization and automatic
control subsystems are employed at the executive level (depicted directly on the UMRP in Fig. 1) of
this system to govern the variables of individual drives and actuators. These subsystems operate as
subordinate control systems to the tactical-level control modules.</p>
      <p>Among the numerous propulsion devices and working tools utilized by the mobile robotic
platform, the adhesion device (AD) holds notable significance. Its incorporation expands the scope of
tasks and technological operations, enabling work in challenging and inaccessible locations on
inclined and vertical surfaces (such as sheer walls and ceilings). The AD can be realized based on
diverse physical principles, including magnetic, electromagnetic, propeller, vacuum, and others,
depending on the tasks and operational conditions. Consequently, for the effective utilization of
various types of adhesion devices on the UMRP across different operating modes, the development of
a suitable universal control module is imperative. Subsequently, we delve into the development of a
functional structure, control algorithms, and key components of the adhesion device control module,
specifically focusing on the specialized adhesion force control system.</p>
    </sec>
    <sec id="sec-4">
      <title>3. Structure of the Control System for the UMRP’s Adhesion Force</title>
      <p>The primary objective of the adhesion device on the mobile robotic platfor m is to generate the
required adhesion force on inclined or vertical surfaces, ensuring the platform's safe and effective
movement while conducting necessary technological operations. While it is possible to maximize the
adhesion force in all operating modes to securely hold the UMRP, this approach would result in
heightened energy consumption by the adhesion device and introduce substantial resistance to the
propulsion devices. Consequently, overall efficiency of the UMRP and the performance of specific
operations would be significantly diminished. Therefore, to achieve optimal utilization of the
adhesion device while conserving energy, it is imperative to implement a flexible control system for
the adhesion force that adapts to different platform movement modes, diverse technological
operations, and various influencing factors. Simultaneously, the AFCS is responsible for determining
the desired (preset) adhesion force and ensuring its automatic maintenance and stabilization. Various
parameters heavily influence the set value of the adhesion force, including the surface inclination
angle, friction coefficient of the working surface, total mass of the robotic platform, technological
tools, and the traction force exerted by the propulsion devices. Furthermore, it is essential for the
control system structure to be universally applicable to any type of adhesion device.</p>
      <p>
        Considering the aforementioned conditions and specific characteristics, as well as the intricacy of
mathematically describing the process of the platform moving on various types of inclined surfaces, it
is advisable to develop the adhesion force control system using artificial intelligence principles [
        <xref ref-type="bibr" rid="ref10 ref9">28,
29</xref>
        ]. This system should comprise two levels of control: tactical and executive. At the tactical level,
the desired adhesion force value between the platform and the surface is determined based on
parameters such as the surface inclination angle, friction coefficient, and traction force of the
propulsion devices. On the other hand, the executive level focuses on the automatic control of the
adhesion force, ensuring the stabilization of the desired value in the presence of various disturbances.
      </p>
      <p>
        After analyzing various methods and approaches in artificial intelligence, it is concluded that
developing the tactical-level subsystem to determine the desired adhesion force using fuzzy or
neurofuzzy models is most appropriate [
        <xref ref-type="bibr" rid="ref11 ref12">9, 30, 31</xref>
        ]. Fuzzy and neuro-fuzzy systems allow effective
generalization of expert knowledge and experimental data, formalization of human thought processes,
creation of linguistic models for complex phenomena, and approximation of nonlinear
multidimensional relationships [
        <xref ref-type="bibr" rid="ref13">32</xref>
        ]. These systems can be synthesized based on expert assessments
and subsequently easily optimized using experimental data or simulation models based on effective
algorithms [
        <xref ref-type="bibr" rid="ref14 ref15 ref16">33-35</xref>
        ]. Furthermore, the executive-level subsystem for automatic control of the adhesion
force should be designed with a neural network controller [
        <xref ref-type="bibr" rid="ref17">36</xref>
        ]. Neural network controllers enable
effective training based on experimental models and provide precise control over complex nonlinear
systems in the presence of uncertain disturbances [
        <xref ref-type="bibr" rid="ref18 ref19">37, 38</xref>
        ]. Considering these factors, the basic
structure of the two-level adhesion force control system for the UMRP is established, as depicted in
Fig. 2.
      </p>
      <p>In Fig. 2, the following notations are used: SCAF is the subsystem for calculating the UMRP’s
adhesion force set value; ANNC is the adhesion neural network controller; AS and FS are the angle
and force sensors; PC is the power converter; uμ is the signal indicating the current value of the
coefficient of friction of the contact parts of the UMRP and the working surface; uF is the signal
indicating the current value of the traction force of the UMRP propulsion devices; uγ is the signal
indicating the current value of the angle of inclination of the working surface; uFS is the SCAF output
signal which corresponds to the set value of adhesion force; uFR is the FS output signal which
corresponds to the real value of adhesion force; uAC is the ANNC output control signal; uPC is the PC
output signal; γR is the current value of the angle of inclination of the working surface; FR is the
adhesion force real value.</p>
      <p>As depicted in Fig. 2, the SCAF operates at the tactical level and calculates the set value of the
adhesion force using signals such as the current coefficient of friction uμ, the current traction force of
the UMRP propulsion devices uF, and the current angle of inclination of the working surface uγ. The
signals uμ and uF are obtained from the strategic level of control, while the signal uγ is acquired from
the angle sensor measuring the working surface's inclination. The current coefficient of friction is
determined through experimentation or preset by the operator, taking into account the type and
material of the working surface. The current traction force of the UMRP propulsion devices is
provided by the platform's propulsion device control system. Subsequently, the SCAF employs a
fuzzy inference engine with a predefined rule base or a neuro-fuzzy system (previously trained) to
calculate the signal uFS, which represents the required value of the adhesion force.</p>
      <p>At the executive level, the adhesion force stabilization is achieved through the implementation of
the neural network controller. The ANNC compares the signal uFS received from the SCAF with the
force sensor signal uFR. Utilizing its embedded algorithm based on a neural network, the ANNC
autonomously controls the adhesion force of the UMRP. The output control signal uAC generated by
the ANNC is amplified by a power converter and directly applied to the adhesion device. It is
important to note that the ANNC needs to be trained beforehand for a specific adhesion device,
utilizing training data, simulation, or experimental models.</p>
      <p>In this paper, the processes of developing and researching the effectiveness of the executive-level
neural network subsystem are considered in detail.</p>
    </sec>
    <sec id="sec-5">
      <title>4. Development of the Neural Network Subsystem for Stabilization and</title>
    </sec>
    <sec id="sec-6">
      <title>Automatic Control of the UMRP Adhesion Force</title>
      <p>
        The neural network subsystem for stabilization and automatic control of the UMRP adhesion force
(Fig. 2) has two inputs (uFS, uFR) and one output (uAC). Analyzing various types of neural network
controllers, we can say that in this case, the most appropriate is the development of the adhesion force
control system based on the NARMA-L2 controller [
        <xref ref-type="bibr" rid="ref20">39</xref>
        ]. This controller has a fairly high efficiency in
controlling complex nonlinear plants with a relatively simple processes of designing and further
implementation [
        <xref ref-type="bibr" rid="ref21 ref22">40, 41</xref>
        ]. NARMA-L2 controller uses the nonlinear autoregressive with moving
average model of control process [
        <xref ref-type="bibr" rid="ref20">39</xref>
        ]. For the synthesis of this controller it is necessary to construct a
discrete nonlinear model of the control process as auto regressive model with moving average. The
control signals of this controller are generated as follows:
u AC k  1 
      </p>
      <p>u FS k d 
g u FR k  ,u FR k  1 ,...,u FR k n  1 ,u AC k  1 ,...,u AC k m  1

f u FR k  ,u FR k  1 ,...,u FR k n  1 ,u AC k  1 ,...,u AC k m  1
g u FR k  ,u FR k  1 ,...,u FR k n  1 ,u AC k  1 ,...,u AC k m  1
where d is the number of prediction cycles; g(∙) and f (∙) are the nonlinear operators.</p>
      <p>The equation (1) is used when d ≥ 2. The functional diagram of the control process and structure of
the neural network controller NARMA-L2 are shown in Fig. 3 and Fig. 4, respectively. Blocks of
delay lines DL memorize the corresponding input and output sequences. The dual-layer neural
networks form the estimations of nonlinear operators and calculates the control signal in the form (1).</p>
      <p>The procedure of the synthesis of this controller represents the process of control plant
identification and designing of the controller in the form of the neural network NARMA-L2-model
(Fig. 4).</p>
      <p>The control plant identification process for NARMA-L2 controller is conducted in the following
way. Various control signals are sequentially applied to the control plant within predetermined
operating ranges in terms of amplitude and time. Herewith, the ranges of change of the control signal
in amplitude and time are set taking into account the real dynamic characteristics and operating
conditions of the plant. Moreover, in most cases, it is advisable to apply random control signals within
the established limits. These control signals, as well as the output response of the plant, are recorded
and form a training sample with the required number of lines. At this point, the identification process
is considered complete, and this generated sample can be used to train the neural network controller.</p>
      <p>The development of this subsystem must be carried out directly for a specific type of adhesion
device, since the neural network controller must be correctly trained on a specific simulation model.</p>
      <p>
        In this paper, an electromagnetic adhesion device was chosen for research, which allows the
robotic platform to move along inclined and vertical ferromagnetic surfaces. This device uses an
electromagnet with the possibility of smooth control to create the required value of the adhesion force
to the ferromagnetic surface. The mathematical model of the adhesion device of this type is presented
in detail in the paper [
        <xref ref-type="bibr" rid="ref23">42</xref>
        ]. This device is applied to the robotic platform with a maximum mass (with
equipment) of 90 kg and is capable of developing a maximum adhesion force of 6000 N. In the
identification process of the control plant (electromagnetic adhesion device) for the NARMA-L2
controller, the training sample of 10,000 points was formed. The dynamics of changes in the input and
output signals of the electromagnetic adhesion device as a control plant in the identification process is
shown in Fig. 5. In the process of synthesizing the considered neural network controller, the following
parameters were chosen: the number of neurons of the hidden layer is 9, the number of delay elements
at the model input is 2, the number of delay elements at the model output is 3.
      </p>
      <p>
        The dynamics of the training error change and the testing on the validation and testing samples are
shown in Fig. 6. The number of training cycles was 200. Training of the neural network was
conducted using the obtained training sample with 10,000 points and the Levenberg-Marquardt
training algorithm [
        <xref ref-type="bibr" rid="ref24 ref25">43, 44</xref>
        ]. At the same time, the given sample was divided into three different
subsamples for training, validation and testing in the following proportions: 70%, 15% and 15%. The
results of the neural network training, validation and testing are shown in Fig. 7-9.
      </p>
      <p>As can be seen from Fig. 7-9, the trained neural network has a sufficiently high accuracy, which
makes it possible to ensure the stabilization of the set value of the adhesion force of the robotic
platform by the NARMA-L2 controller with a sufficiently high efficiency. To confirm the
performance and efficiency of the developed adhesion force stabilization subsystem based on the
neural network controller, the Fig. 10 shows the transients of automatic control of the adhesion force
value in case of an accidental change in the set point. In turn, the following designations are adopted
in Fig. 10: 1 is the given adhesion force value, which comes from the tactical level subsystem; 2 is the
real value of the adhesion force, which is provided by the neural network subsystem of the executive
level. Based on Fig. 10 we defined the quality indicators of transients of the adhesion force automatic
control based on the developed neural network stabilization subsystem. The given quality indicators
are presented in Table 1.</p>
      <p>As can be seen from Fig. 10 and Table 1, the developed automatic control subsystem based on the
trained NARMA-L2 neural network controller has sufficiently high indicators of control quality in
case of random changes in the set values of the adhesion force. In particular, the maximum overshoot
value and the maximum control time are 59.12% and 0.625 seconds, respectively, at the largest jump
(1st step) in the adhesion force set point. Moreover, when working out each set value, the subsystem
provides a zero static error in the adhesion force automatic control. In general, we can conclude that
the developed neural network subsystem has a sufficiently high accuracy and speed of the adhesion
force control, as well as, at the same time, a sufficiently large overshoot value. This fully satisfies the
requirements for the adhesion force automatic control systems of universal robotic platforms, since a
large overshoot value does not seriously affect the quality of control, energy efficiency, reliability and
overall performance. The main requirements of systems of such type are high accuracy and speed,
which, in general, provides reliable adhesion to the working surface.</p>
    </sec>
    <sec id="sec-7">
      <title>5. Conclusions</title>
      <p>This work focuses on the development and investigation of an intelligent system for the automatic
control of adhesion in the universal mobile robotic platform. The proposed system for adhesion
automatic control in the universal mobile robotic platform adopts a two-level structure, consisting of
tactical and executive levels of automatic control. It leverages the principles of artificial intelligence
to enable adaptable automatic control of the adhesion force, considering different platform movement
modes, various technological operations, and other influencing factors. The tactical-level subsystem
plays a key role in determining the required adhesion force based on real-time measurements of
surface inclination, friction coefficient, and propulsion device traction force.</p>
      <p>The executive-level subsystem is developed on the basis of the neural network and allows
implementing proper stabilization and automatic control of the UMRP adhesion force. In particular,
the NARMA-L2 neural network controller is designed and trained on the previously obtained training
data that gives the opportunity to provide effective automatic control of the adhesion force value at
different values of input and disturbing actions. In turn, the development of this subsystem is carried
out for the electromagnetic adhesion device, which allows the robotic platform to hold and move
along inclined and vertical ferromagnetic surfaces due to the smooth control of the electromagnet.
The obtained simulation results in the form of transients of the adhesion force automatic control
during the random changes in the set values show that the developed control subsystem based on the
trained NARMA-L2 neural network controller has sufficiently high quality indicators of control.
Namely, the proposed executive-level subsystem provides a sufficiently high accuracy and speed of
the adhesion force automatic control (the maximum overshoot and the maximum control time are
59.12% and 0.625 seconds, respectively, at the zero value of the static error).</p>
      <p>The developed executive-level subsystem based on the NARMA-L2 neural network controller can
be successfully applied in practice for real universal mobile robotic platforms of various types, sizes
and configurations that move on inclined surfaces. In particular, this version of the system can be used
not only for electromagnetic adhesion devices, but also for other types of devices: propeller, vacuum,
etc. Herewith, it will first be necessary to train the NN controller for the selected clamping device and
UMRP with specific parameters on a simulation model with further adjustment on a real plant.</p>
      <p>Further research should be conducted towards the optimization of the proposed intelligent system
of the adhesion control, development of its software and hardware as well as performing experimental
studies on real universal robotic platforms when carrying out various technological operations.</p>
    </sec>
    <sec id="sec-8">
      <title>6. Acknowledgements</title>
    </sec>
    <sec id="sec-9">
      <title>7. References</title>
      <p>This study is financially supported by the National High Level Foreign Experts Introduction
Project, China (G2022014116L).</p>
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