Parallel robot for knee rehabilitation: Reduced order dynamic linear model, mechanical assembly and control system architecture

In this work we present the development of a dynamic linear model of a 3UPS+1RPU parallel robot for knee rehabilitation, which allows the reduction of the error with respect to simulation carried out based on its non-linear model. Furthermore, the design and implementation of a control algorithm in a real robot is detailed, for which a dynamic linear model has been developed based on inertial parameters including a friction model in Coulomb and viscosity parameters. Subsequently, the linear model has reduced applying the numerical method of decomposition into singular values, resulting in a model expressed as function of base parameters. This method uses a base parameter identification path obtained by finite Fourier series. This path is optimized through minimization algorithms restricted by distance, velocity and acceleration of the linear actuators of the robot, as well as the working space of its spherical joints. Then, the compatibility level of the reduced dynamic model is quantified by estimating mean square error determined between the generalized forces of the independent joints obtained from the model and compared with those resulting from simulations performed in Adams/View software for a trajectory obtained by finite Fourier series. Afterwards, mechanical components involved in the implementation of the prototype are selected and the control system of its actuators is designed. Finally, tests are performed in a laboratory through photogrammetry equipment, in order to validate joints mobility in the robot and study its performance, for this task defined trajectories based on criteria of a physiotherapist are used

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Dynamical modelling of hydraulic excavator considered as a multibody system

This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging operations. The excavator is considered as a rigid body system and detailed governing equations of the mechanical and hydraulic systems are presented. The performed verification and a typical digging task simulation show the applicability of the model for study of the excavator motion simulation. Simulation results of the machine’s response are provided. It is shown that the digging process considerably influences the mechanical and hydraulic system parameters. Such models can be used for training simulators, sizing components and system design.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

Mechatronic modeling of a parallel kinematics multi-axial simulation table based on decoupling the actuators and manipulator dynamics

In this work a mechatronic model was developed for a parallel Multi-Axial Simulation Table (MAST) mechanism. The dynamics of the mechanism was obtained using the principle of energy equivalence and Boltzmann–Hamel equations. In this way, the procedure to obtain the explicit dynamic equations is simplified and has the advantage of being systematic. Also, the actuators and the control were modeled and integrated to simulate and study the system’s positioning and torque. A remarkable contribution of this work is that the mechatronic model developed considers the mechanism as a disturbance to the actuators in a decoupled manner, allowing to easily evaluate alternative designs of whether the actuators, the mechanism or both. Additionally, the procedure taken has been validated with experimental data from an actual MAST prototype.The authors of this paper wish to acknowledge the funding received from the Spanish Government via the Ministerio de Economía y Competitividad (BES-2012-053723 under Project DPI2011-22955 and DPI2015-64450-R), the ERDF of the European Union, the Government of the Basque Country (SAIOTEK 2013 SAI13/245), and the financial support from the University of the Basque Country(UPV/EHU) under the program UFI 11/29

A method for the mechatronico analysis of parallel kinematics manipulators based on decoupling the dynamics of actuators and mechanism

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