Publications
Here you will find the scientific publications (journal articles and conferences) directly related to the research project that have been produced by the members of the research team.
Journal articles and book chapters
The scientific articles published in journals and book chapters developed within the scope of this research project are the following:
2023
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![[DOI]](http://roboprop.ai2.upv.es/wp-content/plugins/papercite/img/external.png)
J. L. Pulloquinga, R. J. Escarabajal, Á. Valera, M. Vallés, and V. Mata, «A type ii singularity avoidance algorithm for parallel manipulators using output twist screws,» Mechanism and machine theory, vol. 183, p. 105282, 2023.
[Bibtex]@article{PULLOQUINGA2023105282, title = {A Type II singularity avoidance algorithm for parallel manipulators using output twist screws}, journal = {Mechanism and Machine Theory}, volume = {183}, pages = {105282}, year = {2023}, issn = {0094-114X}, doi = {https://doi.org/10.1016/j.mechmachtheory.2023.105282}, url = {https://www.sciencedirect.com/science/article/pii/S0094114X23000551}, author = {José L. Pulloquinga and Rafael J. Escarabajal and Ángel Valera and Marina Vallés and Vicente Mata}, keywords = {Singularity avoidance, Trajectory planning, Parallel robots, Output twist screws}, abstract = {Parallel robots (PRs) are closed-chain manipulators with diverse applications due to their accuracy and high payload. However, there are configurations within the workspace named Type II singularities where the PRs lose control of the end-effector movements. Type II singularities are a problem for applications where complete control of the end-effector is essential. Trajectory planning produces accurate movements of a PR by avoiding Type II singularities. Generally, singularity avoidance is achieved by optimising a geometrical path with a velocity profile considering singular configurations as obstacles. This research presents an algorithm that avoids Type II singularities by modifying the trajectory of a subset of the actuators. The subset of actuators represents the limbs responsible for a Type II singularity, and they are identified by the angle between two Output Twist Screws. The proposed avoidance algorithm does not require optimisation procedures, which reduces the computational cost for offline trajectory planning and makes it suitable for online trajectory planning. The avoidance algorithm is implemented in offline trajectory planning for a pick and place planar PR and a spatial knee rehabilitation PR.} } - R. J. Escarabajal, J. L. Pulloquinga, Á. Valera, V. Mata, M. Vallés, and F. J. Castillo-García, «Combined admittance control with type ii singularity evasion for parallel robots using dynamic movement primitives,» Ieee transactions on robotics, pp. 1-16, 2023.
[Bibtex]@ARTICLE{10037759, author={Escarabajal, Rafael J. and Pulloquinga, José L. and Valera, Ángel and Mata, Vicente and Vallés, Marina and Castillo-García, Fernando J.}, journal={IEEE Transactions on Robotics}, title={Combined Admittance Control With Type II Singularity Evasion for Parallel Robots Using Dynamic Movement Primitives}, year={2023}, volume={}, number={}, pages={1-16}, doi={10.1109/TRO.2023.3238136}} - R. J. Escarabajal, J. L. Pulloquinga, V. Mata, Á. Valera, and M. Díaz-Rodríguez, «Model-based control of a 4-dof rehabilitation parallel robot with online identification of the gravitational term,» Sensors, vol. 23, iss. 5, 2023.
[Bibtex]@Article{Escarabajal2023, author = {Escarabajal, Rafael J. and Pulloquinga, José L. and Mata, Vicente and Valera, Ángel and Díaz-Rodríguez, Miguel}, journal = {Sensors}, title = {Model-Based Control of a 4-DOF Rehabilitation Parallel Robot with Online Identification of the Gravitational Term}, year = {2023}, issn = {1424-8220}, number = {5}, volume = {23}, abstract = {Parallel robots are being increasingly used as a fundamental component of lower-limb rehabilitation systems. During rehabilitation therapies, the parallel robot must interact with the patient, which raises several challenges to the control system: (1) The weight supported by the robot can vary from patient to patient, and even for the same patient, making standard model-based controllers unsuitable for those tasks since they rely on constant dynamic models and parameters. (2) The identification techniques usually consider the estimation of all dynamic parameters, bringing about challenges concerning robustness and complexity. This paper proposes the design and experimental validation of a model-based controller comprising a proportional-derivative controller with gravity compensation applied to a 4-DOF parallel robot for knee rehabilitation, where the gravitational forces are expressed in terms of relevant dynamic parameters. The identification of such parameters is possible by means of least squares methods. The proposed controller has been experimentally validated, holding the error stable following significant payload changes in terms of the weight of the patient’s leg. This novel controller allows us to perform both identification and control simultaneously and is easy to tune. Moreover, its parameters have an intuitive interpretation, contrary to a conventional adaptive controller. The performance of a conventional adaptive controller and the proposed one are compared experimentally.}, article-number = {2790}, doi = {10.3390/s23052790}, pubmedid = {36905000}, url = {https://www.mdpi.com/1424-8220/23/5/2790}, }
2022
- N. Farhat, P. Zamora, D. Reichert, V. Mata, A. Page, and A. Valera, «A computationally efficient musculoskeletal model of the lower limb for the control of rehabilitation robots: assumptions and validation,» Applied sciences, vol. 12, iss. 5, 2022.
[Bibtex]@Article{app12052654, author = {Farhat, Nidal and Zamora, Pau and Reichert, David and Mata, Vicente and Page, Alvaro and Valera, Angel}, journal = {Applied Sciences}, title = {A Computationally Efficient Musculoskeletal Model of the Lower Limb for the Control of Rehabilitation Robots: Assumptions and Validation}, year = {2022}, issn = {2076-3417}, number = {5}, volume = {12}, abstract = {We present and validate a computationally efficient lower limb musculoskeletal model for the control of a rehabilitation robot. It is a parametric model that allows the customization of joint kinematics, and it is able to operate in real time. Methods: Since the rehabilitation exercises corresponds to low-speed movements, a quasi-static model can be assumed, and then muscle force coefficients are position dependent. This enables their calculation in an offline stage. In addition, the concept of a single functional degree of freedom is used to minimize drastically the workspace of the stored coefficients. Finally, we have developed a force calculation process based on Lagrange multipliers that provides a closed-form solution; in this way, the problem of dynamic indeterminacy is solved without the need to use an iterative process. Results: The model has been validated by comparing muscle forces estimated by the model with the corresponding electromyography (EMG) values using squat exercise, in which the Spearman’s correlation coefficient is higher than 0.93. Its computational time is lower than 2.5 ms in a conventional computer using MATLAB. Conclusions: This procedure presents a good agreement with the experimental values of the forces, and it can be integrated into real time control systems.}, article-number = {2654}, doi = {10.3390/app12052654}, url = {https://www.mdpi.com/2076-3417/12/5/2654}, }
Congress proceedings
The scientific articles published in congresses and conferences developed within the scope of this research project are the following:
2022
- J. L. Pulloquinga, R. J. Escarabajal, M. Vallés, Á. Valera, and V. Mata, «Trajectory planner for type ii singularities avoidance based on output twist screws,» in Advances in robot kinematics 2022, Cham, 2022, p. 445–452.
[Bibtex]@InProceedings{10.1007/978-3-031-08140-8_48, author = {Pulloquinga, Jos{\'e} L. and Escarabajal, Rafael J. and Vall{\'e}s, Marina and Valera, {\'A}ngel and Mata, Vicente}, booktitle = {Advances in Robot Kinematics 2022}, title = {Trajectory Planner for Type II Singularities Avoidance Based on Output Twist Screws}, year = {2022}, address = {Cham}, editor = {Altuzarra, Oscar and Kecskem{\'e}thy, Andr{\'e}s}, pages = {445--452}, publisher = {Springer International Publishing}, abstract = {Motion planning of manipulators is a major discipline in robotics that involves the generation of feasible trajectories within the workspace so that neither collisions nor singularities are encountered during its execution. The singularity issue is of paramount importance in parallel robots (PRs) which, despite their capability of performing very accurate movements, suffer from the so-called Type II singularities. These singular configurations occur within the workspace, and a PR loses control when approaching such configurations. In this paper, an algorithm for Type II singularities avoidance in PRs is proposed that allows to i) create a new trajectory from an initial to a final configuration that is non-singular, and ii) adapt an existing trajectory that goes through singular configurations so that the new generated trajectory evades them with minimum modifications of the original path. The new trajectory may serve as a reference position for safe control of a PR, and it is used in an experiment on a real 4-DOF PR meant for knee rehabilitation, with a position controller to follow the trajectory. The results show how the initially unstable behavior when following an original singular trajectory can be fixed after modifying that trajectory with the proposed algorithm.}, isbn = {978-3-031-08140-8}, } - J. L. Pulloquinga, M. Ceccarelli, V. Mata, and Á. Valera, «Experimental identification of singularities in parallel manipulators,» in Syrom & robotics 2022 joint international conference of the 13th iftomm international symposium on science of mechanisms and machines (syrom 2022) and the xxv international conference on robotics (robotics 2022), 2022.
[Bibtex]@InProceedings{2, author = {Pulloquinga, Jos{\'e} L. and Ceccarelli, Marco and Mata, Vicente and Valera, {\'A}ngel}, booktitle = {SYROM & ROBOTICS 2022 Joint International Conference of the 13th IFToMM International Symposium on Science of Mechanisms and Machines (SYROM 2022) and the XXV International Conference on Robotics (ROBOTICS 2022)}, title = {Experimental Identification of Singularities in Parallel Manipulators}, year = {2022}, address = {}, editor = {}, pages = {}, publisher = {Federacion Iberoamericana de Ingenieria Mecanica}, abstract = {} isbn = {}, } - J. L. Pulloquinga, O. Altuzarra, V. Petuya, A. Hernandez, V. Mata, and Á. Valera, ,» in XV Congreso Iberoamericano de Ingeniería Mecánica (CIBIM 2022)} title = {Estudio Del Contacto Cuasi-Estático De Un Robot Paralelo Flexible En Tareas Colaborativas, 2022.
[Bibtex]@InProceedings{3, author = {Pulloquinga, Jos{\'e} L. and Altuzarra, Oscar and Petuya, Victor and Hernandez, Alfonso and Mata, Vicente and Valera, {\'A}ngel}, booktitle = {XV Congreso Iberoamericano de Ingeniería Mecánica (CIBIM 2022)} title = {Estudio Del Contacto Cuasi-Estático De Un Robot Paralelo Flexible En Tareas Colaborativas}, year = {2022}, address = {}, editor = {}, pages = {}, publisher = {IFToMM}, abstract = {} isbn = {}, }
