**1. Introduction**

The main contribution of this paper is the modeling and control of a complex autonomous system (CAS) equipped with a robotic manipulator (RM) and a mobile visual sensor (MVS) to achieve precise positioning in a processing technology on a laboratory mechatronics line (ML). The presented technology allows the recovery of products, through reprocessing, if they partially satisfy the quality requirements. The mechatronics line handles the full manufacturing process of a workpiece, and it has buffering, handling, processing (drilling, boring), sorting, and quality testing facilities. Due to the fact that this technology allows the product retrieval operation for reprocessing, the mechatronics line will be further referred to as P/RML.

This paper presents the integration of multiple subsystems for a laboratory mechatronic line: the P/RML is served by a CAS consisting of an ARS equipped with a 7 DOF RM Cyton 1500 and uses an eye in hand type Mobile Visual Servoing (MVS) located on the

**Citation:** Simion, G.; Filipescu, A.; Ionescu, D.; S, olea, R.; Cernega, D.; Minc ˘a, E.; Filipescu, A. Mobile Visual Servoing Based Control of a Complex Autonomous System Assisting a Manufacturing Technology on a Mechatronics Line. *Inventions* **2022**, *7*, 47. https://doi.org/10.3390/ inventions7030047

Academic Editor: Anastasios Doulamis

Received: 15 May 2022 Accepted: 19 June 2022 Published: 22 June 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

end-effector. Task planning, simulation, monitoring, and real-time control are some of the tools used to fulfill the objectives of this study, like workpiece recovery for reprocessing or the increase of the automation level o for the P/RML so that a human operator is no longer needed after the program is started. Moreover, the CAS improves the reusability feature of the production line [1–5].

The manufacturing line is characterized by the operations to be performed in the workstations using the monitoring and control systems, CAS, ARS, RM, MVS which give reparability and flexibility features for processing and reprocessing operations [4–8]. The structure of the P/RML highlights the system's overall functions: the automatic processing of parts, transport, handling, storing and the automatic control of all the devices integrated in the system using the PLCs in different configurations: centralized or distributed. The processing/reprocessing tasks are the P/RML actions (drilling, reaming, extrusion, bending), operations which are executed in serial or parallel for manufacturing the workpiece until the final product meets the quality requirements. For this, the processing/reprocessing planning also requires complex operations to be performed such as performance measurement and evaluation, kinematics control, system planning, and resources management. For a P/RML assisted by CAS, a preparing strategy adapted to the characteristics of the system is more effective than the techniques used from domain-independent methods [6–11]. If the final workpiece does not pass the quality test, the task planner will provide the optimal sequence to reprocess the product.

Visual servoing systems are robust systems that enhance the accuracy and adaptability of the control architecture based on optical feedback [12]. The purpose of a servoing system is to close the movement control loop for a robotic arm. The robotic arm has to move from an initial point to a destination point. The aim of a MVS is to provide information, based on a visual sensor, regarding the actual position. Based on this information, the robot control is able to improve the interaction with the working environment. The features extracted from the images represent the actual position and also the input for the control architecture. The control architectures corresponding to the servoing systems are divided into three categories:


An important factor for a MVS is the visual features selection, which is related to the speed, accuracy, and performance that control the movement of a RM, taking into consideration the degrees of freedom as shown in [10,18,19].

Other elements of originality and contributions are concentrated in the following areas: assigning, planning, and synchronization tasks of P/RML assisted by CAS, RMs, and MVS, designing the architecture of the entire system to allow flexible manufacturing, multifunctionality, communication, synchronization of signals from sensors, distributed control and image processing for precise positioning eye in hand MVS and real-time control, improving the level of automation and increasing the efficiency of the manufacturing lines using the CAS.

The article is structured as follows:

Section 2 is dedicated to the hardware structure and the functional features of the system:

