Carvajal, Christian

Preferred name

Carvajal, Christian

Main Affiliation

Centro de Investigación de Ciencias Humanas y de la Educación

Ambato

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INDI: A Low-Cost LLM-Enabled Multimodal Campus Guide Robot
(MDPI AG, 2026-09-03)
Varela Aldas, José
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Carvajal, Christian
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Cadena, Josue
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Del-Valle-Soto, Carolina
University technology campuses contain specialized laboratories, academic programs, and services that can be difficult for first-time visitors to identify. This paper presents INDI, a custom mobile campus guide robot that combines spoken interaction, synthesized speech, touchscreen feedback, animated facial states, head motion, and predefined mobile guidance behaviors. The platform retains the modular mechanical concept of an earlier prototype while replacing its Raspberry Pi and open-loop remote-control architecture with an NVIDIA Jetson Nano, an Arduino Uno motor-control bridge, ROS 1 nodes, encoder feedback, and dual PID speed loops. The robot weighs 2.37 kg, measures (Formula presented.) cm, reaches a software-limited maximum speed of 0.4 m/s, and provides 27 min of continuous operation in the reported tests. Ten repetitions of each motion test produced mean displacements of 1.058 m and 2.182 m for 1 m and 2 m commands, respectively, and mean rotations of 89.2° and 180.3° for 90° and 180° commands. Voice trials achieved 90% correct interaction in a quiet environment and 70% under nearby conversational noise. In an exploratory user study with 13 participants, 16 of 20 assigned tasks were completed and the mean overall rating was 4.31/5. The results demonstrate the feasibility of an integrated, modular, physically embodied information service, while also revealing accumulated linear-motion error, sensitivity to ambient speech, limited battery duration, and the need for grounded institutional knowledge and autonomous localization. These findings are presented as preliminary evidence of technical and interaction feasibility rather than as confirmatory evidence of usability or campus-scale autonomous navigation. © 2026 by the authors.
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Virtual Teleoperation System for Mobile Manipulator Robots Focused on Object Transport and Manipulation
(2024)
Fernando J. Pantusin
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Carvajal, Christian
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Jessica S. Ortiz
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Víctor H. Andaluz
This work describes the development of a tool for the teleoperation of robots. The tool is developed in a virtual environment using the Unity graphics engine. For the development of the application, a kinematic model and a dynamic model of a mobile manipulator are used. The mobile manipulator robot consists of an omnidirectional platform and an anthropomorphic robotic arm with 4 degrees of freedom (4DOF). The model is essential to emulate the movements of the robot and to facilitate the immersion in the virtual environment. In addition, the control algorithms are established and developed in MATLAB 2020 software, which improves the acquisition of knowledge to teleoperate robots and execute tasks of manipulation and transport of objects. This methodology offers a cheaper and safer alternative to real physical systems, as it reduces both the costs and risks associated with using a real robot for training.
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A hybrid bio-inspired visual servoing strategy for aerial grasping of static and moving targets
(2026)
Carvajal, Christian
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Víctor H. Andaluz
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Flavio Roberti
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Varela Aldas, José
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Ricardo Carelli
This article presents a bio-inspired visual servo control scheme for aerial grasping of static and moving targets using aerial manipulators (AM). The proposed approach is based on a cascaded control architecture. The first control layer implements a bio-inspired hybrid visual servo strategy that combines Image Based Visual Servoing (IBVS) and Position Based Visual Servoing (PBVS), motivated by the prey capturing behavior of birds of prey. An Aerial-Eye-to-Hand visual configuration is introduced, in which an onboard camera mounted on the aerial platform is used to simultaneously regulate image plane features and spatial variables associated with the target. The grasping task is organized into four autonomous stages, enabling coordinated detection, approach, grasping, and transportation. Exploiting the redundancy of aerial manipulators, the proposed scheme allows the simultaneous fulfillment of multiple control objectives, including target visibility maintenance and accurate end effector positioning. The second control layer consists of a dynamic compensation controller formulated in terms of reference velocities, which facilitates its implementation on aerial platforms with embedded low level controllers. A formal stability and robustness analysis of the cascaded closed-loop system is provided. Experimental results, including real-world aerial grasping of moving ground targets in unstructured environments, demonstrate the effectiveness of the proposed approach. © 2026 The Author(s)
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Immersive Digital Twin for Industrial Control Education
(Springer Nature Switzerland, 2026-08-15)
Andaluz, Víctor H.
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Carvajal, Christian
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Culqui-Tipan, Javier
This paper presents the development and implementation of an immersive Digital Twin for industrial control education, conceived as an experiential learning tool that integrates a real industrial control system, a three-dimensional virtual environment, and a real-time communication infrastructure. The proposed approach follows a layered architecture linking a smart tomato greenhouse as the physical process, a Siemens S7-1500 programmable logic controller, a human–machine interface for supervision and variable adjustment, a Unity-based virtual environment for immersive interaction, and an IoT platform for real-time data transmission and remote visualization. The Digital Twin synchronously replicates the physical process, enabling users to analyze the relationship between environmental variables, control decisions, and system response, as well as to identify normal and critical operating conditions. The system was evaluated through an experimental study with twenty undergraduate engineering students, considering usability and learning outcomes. The System Usability Scale yielded an average score of 82.5 (SD = 6.1), indicating high user acceptance. Learning performance, assessed through a test–retest strategy, increased from 55.3 (pre-test) to 76.8 (post-test), corresponding to a mean gain of 21.5 points after two weeks. Statistical analysis confirmed a significant improvement (p < 0.001) with a large effect size, demonstrating the positive impact of the immersive Digital Twin on understanding industrial control systems. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2027.
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Robust Visual Servoing for Quadruped Robots: ISS-Based Target Tracking With Secondary Formation Objectives
(2026)
Carvajal, Christian
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Chicaiza Claudio, Fernando
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Varela Aldas, José
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Víctor H. Andaluz
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Flavio Roberti
This workpresents the design, implementation, and experimental validation of a visual servo control scheme formulated at the task-space level and applied to a quadruped robot equipped with an active two degree of freedom (2DoF) vision system for continuous tracking of moving targets. The proposed controller is based on a differential kinematic model that maps the robot's task-space velocity references to the kinematic evolution of the active vision system, incorporating a target velocity estimator that enables dynamic compensation of the target motion projected onto the image plane. The control architecture exploits the kinematic redundancy of the robotic system to simultaneously address multiple control objectives within a hierarchical framework. The primary task ensures target centering in the image plane, thereby maintaining visibility within the robot's field of view, while the secondary task regulates relative formation by controlling the distance and orientation between the robot and the target. Quadruped locomotion is handled by a low-level gait controller and is not modified by the proposed scheme. Closed-loop stability is rigorously analyzed using Lyapunov theory, demonstrating Input-to-State Stability properties in the presence of bounded disturbances. Simulation and real-world experimental results obtained with the Unitree Go2 robot confirm the robustness and stability of the proposed approach for dynamic visual tracking in realistic scenarios. © 2020 IEEE.
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Technology-Mediated Collaborative Strategies Among Online University Students
(2025)
Núñez-Naranjo, Aracelly Fernanda
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Quezada-Sarmiento, Pablo Alejandro
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Junta, Christian
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Orly Carvache-Franco
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Lidia Minchenkova
This quasi-experimental study aimed to evaluate the effectiveness of collaborative teaching strategies mediated by digital technologies among online university students. The research was conducted with a sample of 256 participants, divided into an experimental group and a control group. While both groups used technological resources, only the experimental group engaged in structured collaborative strategies using tools such as Genially, Kahoot, Canva, Padlet, and Wordwall, within the framework of the Cátedra Integradora course. The results revealed a significant improvement in the academic performance of the experimental group, with an average increase of 27.4%, compared to 13.2% in the control group. Furthermore, the teacher's perception highlighted higher levels of student engagement, motivation, and collaboration among those who actively participated in the strategies. These findings demonstrate that the intentional use of educational technologies with a collaborative focus fosters active, participatory, and meaningful learning, while also strengthening socio-emotional skills and improving academic achievement in virtual higher education settings. © 2025 IEEE.
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Bidirectional immersive digital twin for real-time monitoring and supervisory interaction in PLC-controlled manufacturing
(Springer Science and Business Media LLC, 2026-09-26)
Ortiz, Jessica S.
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Andaluz, Víctor H.
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Carvajal, Christian
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Llamuca, Marlon A.
Digital Twins are increasingly used for monitoring and interaction with automated processes, but integrating immersive environments with active control systems while preserving controller authority remains challenging. This study presents an operational and supervisory immersive Digital Twin for a PLC-controlled automated filling process, enabling bidirectional communication between a physical module and its virtual representation. The architecture integrates a Siemens S7-1200 PLC, OPC UA, MQTT, and a virtual reality environment. PLC-reported process states are mapped to corresponding virtual components, while supervisory commands generated in the virtual environment are returned to the PLC and processed by its control logic before affecting the physical module. Experimental validation was conducted on a laboratory-scale automated bottling module over 100 operating cycles. Process-update latency averaged 78 ms, ranging from 64 to 92 ms, with a system availability of 99.4%. Evaluation of 100 supervisory commands yielded mean command transmission, controlled-process response, and end-to-end round-trip times of 42, 180, and 302 ms, respectively, with a command success rate of 99.0%. An interaction study with 26 participants showed comparable task completion times for WinCC and the immersive Digital Twin, with fewer operational errors, lower NASA–TLX scores, and a System Usability Scale score of 94/100. The results confirm bidirectional supervisory interaction and support physical–digital state correspondence during experimental operation while maintaining PLC control authority. © The Author(s) 2026.
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Bilateral Rate/Position Delayed Teleoperation Control for UAVs: A Performance Evaluation
(2025)
Chicaiza Claudio, Fernando
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Emanuel Slawiñski
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Viviana Moya
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Carvajal, Christian
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Varela Aldas, José
This paper introduces a bilateral teleoperation system for UAVs that employs a hybrid control scheme combining rate and non-linear position modes. By continuously switching between these modes, the system achieves both agile manoeuvring and precise positioning under communication delays. Validation is carried out using a dynamic model for the master robot with a Novint Falcon haptic device and a simplified model for the slave robot in Gazebo-ROS2. Performance metrics including task completion time, mean squared error, and force feedback demonstrate enhanced stability and efficiency, suggesting promising applications in inspection, environmental monitoring and search and rescue
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Digital Twin Integration for Active Learning in Robotic Manipulator Control Within Engineering 4.0
(2025)
Fernando J. Pantusin
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Jessica S. Ortiz
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Carvajal, Christian
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Víctor H. Andaluz
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Lenin G. Yar
Robotic systems play an increasingly significant role in both education and industry; however, access to physical robots remains a challenge due to high costs and operational risks. This work presents a training platform based on Digital Twins, aimed at active learning in the control of robotic manipulators, with a focus on the UFACTORY 850 arm. The proposed approach integrates mathematical modeling, interactive simulation, and experimental validation, enabling the implementation and testing of control strategies in three virtual scenarios that replicate real-world conditions: a laboratory, a service environment, and an industrial production line. The system relies on kinematic and dynamic models of the manipulator, using maneuverability velocities as input signals, and employs ROS as middleware to link the Unity 2022.2.14 graphics engine with the control algorithms developed in MATLAB R2022a. Experimental results demonstrate the accuracy of the implemented models and the effectiveness of the control algorithms, validating the usefulness of Digital Twins as a pedagogical tool to support safe, accessible, and innovative learning in robotic engineering.
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Real-Time Digital Twin Architecture for Immersive Industrial Automation Training
(2026)
Jessica S. Ortiz
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Víctor H. Andaluz
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Carvajal, Christian
Industrial automation laboratories often face limitations related to restricted access to industrial equipment, safety constraints, and limited scalability for hands-on experimentation. To address these challenges, this work proposes a real-time multi-layer Digital Twin architecture integrating a physical Siemens S7-1500 PLC, an immersive Unity-based virtual environment, HMI supervision, and IoT-enabled remote monitoring within a unified communication framework. The architecture is structured into physical, digital, and integration layers, enabling modular scalability and bidirectional synchronization between the physical process and its virtual representation through Ethernet TCP/IP communication. System performance was evaluated using synchronization metrics including communication latency, jitter, deterministic timing deviation, and event synchronization accuracy. Experimental results demonstrated stable PLC–Digital Twin communication with average latencies below 15 ms and jitter below 0.5 ms, ensuring reliable real-time interaction during continuous operation. A comparative evaluation with engineering students also showed improved learning conditions, achieving high perceived usability (SUS = 86/100) and reduced cognitive workload (NASA-TLX = 34/100). These results confirm the effectiveness of the proposed architecture as a scalable platform for Industry 4.0 training environments.</jats:p>
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Carvajal, Christian

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