An Automated Conversion Between Selected Robot Kinematic Representations

This paper presents a methodology that forms an automated tool for robot kinematic representation conversion, called the RobKin Interpreter. It is a set of analytical algorithms that can analyze an input robot representation, express the joints globally in matrix form, and map to other representations such as standard Denavit-Hartenberg parameters, Roll-Pitch-Yaw angles with translational displacement, and Product of Exponentials with a possibility to generate a URDF (Universal Robot Description Format) file from any of them. It works for revolute and prismatic joints and can interpret even arbitrary kinematic structures that do not have orthogonally placed joints

Identification of Inertial Parameters for Position and Force Control of Surgical Assistance Robots

[EN] Surgeries or rehabilitation exercises are hazardous tasks for a mechanical system, as the device has to interact with parts of the human body without the hands-on experience that the surgeon or physiotherapist acquires over time. For various gynecological laparoscopic surgeries, such as laparoscopic hysterectomy or laparoscopic pelvic endometriosis, Uterine Manipulators are used. These medical devices allow the uterus to be suitably mobilized. A gap needs to be filled in terms of the precise handling of this type of devices. In this sense, this manuscript first describes the mathematical procedure to identify the inertial parameters of uterine manipulators. These parameters are needed to establish an accurate position and force control for an electromechanical system to assist surgical operations. The method for identifying the mass and the center of mass of the manipulator is based on the solution of the equations for the static equilibrium of rigid solids. Based on the manipulator inertial parameter estimation, the paper shows how the force exerted by the manipulator can be obtained. For this purpose, it solves a matrix system composed of the torques and forces of the manipulator. Different manipulators have been used, and it has been verified that the mathematical procedures proposed in this work allow us to calculate in an accurate and efficient way the force exerted by these manipulators.The authors wish to thank the "Agencia Valenciana de la Innovacio" (Generalitat Valenciana) for the partial funding of this study under the project with reference INNCON00/20/002. We also want to thank the "Instituto Universitario de Automatica e Informatica Industrial (ai2)" of the "Universitat Politecnica de Valencia" for its financial support under the program "Plan de ayudas a la I+D+I del Instituto ai2".Zamora-Ortiz, P.; Carral-Alvaro, J.; Valera Fernández, Á.; Pulloquinga-Zapata, J.; Escarabajal-Sánchez, RJ.; Mata Amela, V. (2021). Identification of Inertial Parameters for Position and Force Control of Surgical Assistance Robots. Mathematics. 9(7):1-16. https://doi.org/10.3390/math9070773S1169

Forward Kinematics Based Prediction for Bending Motion of Soft Pneumatic Actuators with Various Air Chambers

This study proposes a forward kinematic model for soft actuators that utilize pneumatic control to predict their bending motion, which is simulated using Ansys software. Firstly, a bending motion test is conducted with a 2-air chamber actuator to derive an equation that establishes the relationship between the bending angle and input pressure. Next, a serial model for the overall soft actuator is developed using forward kinematics with the DH method. The angle variables in the soft actuator are then replaced with an equation that relates the deformed angle and compressed air. Finally, the proposed serial model is used to predict the bending motion of 4-air and 6-air chamber actuators, and the results are compared to simulations and real experiments. The comparison shows that the proposed model could accurately predict the bending motion of the real actuators within an acceptable tolerance of 10%

Fuzzy Model-Reference Adaptive Control Method For An Underwater Robotic Manipulator

Pengendali robotik dalam air (URM) adalah berbeza jika dibandingkan dengan pengendali robotik biasa atau yg berada di permukaan. Dinamiknya mempunyai ketidakpastian yang besar bergantung kepada daya apungan, daya yang dihasilkan oleh jisim tambahan/momen luas kedua dan daya geseran. Tambahan lagi, ia juga dipengaruhi oleh gangguan luaran yang penting seperti arus dan ombak. The underwater robotic manipulators (URMs) are different with the ordinary or landbased robotic manipulators. Its dynamics have large uncertainties owing to the buoyancy, force induced by the added mass/moment of inertia and the drag force. Moreover, they are also affected by the crucial external disturbances such as currents and waves

Validation of the Estimated Torques of an Open-chain Kinematic Model of the Human Body

The standing human body is frequently modeled as an inverted double pendulum restricted to a single plane. In order to capture the coordination efforts and interplay between spatial dimensions, the model has to capture motion and joint torques in all spatial dimensions. Our two-segment model covers two degrees of freedom (ML and AP revolutions) at the ankle and the hip level and utilizes the Denavit-Hartenberg convention. This work aimed to validate the model's torque estimation on a diverse group of participants (11 women, 22–56 years, 11 men, 22–61 years). The inverse dynamic calculations provide estimated joint torques for a motion capture recorded trial, while standing on a force platform enables the indirect measurement of ankle torques. A 60-second-long visually guided balancing task was recorded and repeated three times. The estimated and the indirectly measured torques were compared, and offset and variance type errors ( normalized RMSE and R2 ) were analyzed. The R2-values were excellent (R2 > 0.90) 64 out of the 66 cases (97%) for AP torques and 58 out of the 66 cases (88%) for ML torques. Normalized RMSE values were dominantly under the 0.35 value with some outliers. RMSE showed no evident connection with age, body height, body mass, or BMI. An open-chain kinematic model with two segments, following the Denavit-Hartenberg convention, is well suited to estimate the control torque traces of the human body during standing balancing and needs only three tracked positions

Projeto de mecanismos de costura com acesso unilateral usando síntese do número e do tipo

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2013.O projeto de novos dispositivos mecânicos depende da experiência e conhecimento do projetista. Metodologias de projeto foram desenvolvidas visando diminuir essa dependência. Neste trabalho, algumas metodologias de projeto de mecanismos são analisadas e comparadas. Em seguida, uma nova metodologia é proposta, com foco na determinação das características estruturais e no uso dos requisitos de projeto para eliminar mecanismos inviáveis. Outro objetivo da metodologia proposta e sistematizar o projeto de mecanismos de modo a reduzir decisões subjetivas por parte do projetista. Por fim, a metodologia proposta e aplicada no projeto de mecanismos de costura. Os mecanismos de costura podem ser classificados em dois tipos: com acesso bilateral e com acesso unilateral. A costura com acesso unilateral apresenta grande potencial para diversas aplicações, tanto na indústria têxtil quanto em áreas menos tradicionais, como a medicina. Entretanto, poucos dispositivos para a costura com acesso unilateral foram desenvolvidos com sucesso. Neste trabalho, o mecanismo de costura projetado é do tipo com acesso unilateral. O desenvolvimento do projeto segue a metodologia proposta. Assim, faz-se inicialmente um levantamento do estado da arte de mecanismos de costura com acesso unilateral. Utilizando o levantamento do estado da arte, listam-se os requisitos necessários para tal mecanismo. Em seguida, faz-se a síntese de mecanismos de costura com acesso unilateral. Após a eliminação de mecanismos inviáveis, apresentam-se dois mecanismos de costura com acesso unilateral. Finalmente, notou-se que a metodologia utilizada tornou o projeto independente do projetista visto que nenhuma decisão foi subjetiva.Abstract : The design of new mechanical devices depends on the designer's experienceand knowledge. Design methodologies were created in an effort tomake the design process less dependent on the designer. In this work, afew mechanisms design methodologies are analysed and compared. Then,a new methodology is proposed, concentrating on the determination of structuralcharacteristics and on the use of the design requirements to eliminateunfeasible mechanisms. Another objective of the proposed methodology is tosystemise the design of mechanisms in order to reduce subjectives decisionsfrom the designer. The proposed methodology is then applied to the designof stitching mechanisms.Stitching mechanisms can be classified in two types: two-side access andone-side access. Stitching with one-side access has a great potential for manyapplications, such as textile industries or even medicine; although, few ofsuch designed devices were successfully developed. In this work, the stitchingmechanism designed is with one-side access.The development of the mechanism follows the proposed methodology. Initially,a state of the art survey for one-side stitching devices is carried out.Once the survey is done, all design and structural requirements for an onesidestitching device are listed. Then, the synthesis of mechanisms for a onesidestitching device is done. After unfeasible mechanisms are eliminated,two solutions for stitching devices with one-side access are presented. Finally,the proposed methodology made the design process independent fromthe designer since no subjective decision was taken

Initial estimation of kinematic structure of a robotic manipulator as an input for its synthesis

Researchers often deal with the synthesis of the kinematic structure of a robotic manipulator to determine the optimal manipulator for a given task. This approach can lower the cost of the manipulator and allow it to achieve poses that might be unreachable by universal manipulators in an existing constrained environment. Numerical methods are broadly used to find the optimum design but they often require an estimated initial kinematic structure as input, especially if local-optimum-search algorithms are used. This paper presents four different algorithms for such an estimation using the standard Denavit-Hartenberg convention. Two of the algorithms are able to reach a given position and the other two can reach both position and orientation using Bezier splines approximation and vector algebra. The results are demonstrated with three chosen example poses and are evaluated by measuring manipulability and the total link length of the final kinematic structures.Web of Science118art. no. 354

Implementing efficient concerted rotations using Mathematica and C code

In this article we demonstrate a general and efficient metaprogramming implementation of concerted rotations using Mathematica. Concerted rotations allow the movement of a fixed portion of a polymer backbone with fixed bending angles, like a protein, while maintaining the correct geometry of the backbone and the initial and final points of the portion fixed. Our implementation uses Mathematica to generate a C code which is then wrapped in a library by a Python script. The user can modify the Mathematica notebook to generate a set of concerted rotations suited for a particular backbone geometry, without having to write the C code himself. The resulting code is highly optimized, performing on the order of thousands of operations per second