FIGURE 8 - uploaded by Damien Charles Chablat
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This article presents a new variable actuation mechanism based on the 3-RPR parallel robot. This mechanism is an evolution of the NaVARo robot, a 3-RRR parallel robot, for which the second revolute joint of the three legs is replaced by a scissor to obtain a larger working space and avoid the use of parallelograms to operate the second revolute joi...
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Context 1
... there is only one working mode, the equations of these surfaces are simpler than for the NAVARO I robot for which it is not possible to simply describe these equations. Figures 8 and 9 show all singularities for the eight actuation modes without and with the joint limit conditions. As none of them are superposed, it is possible to completely move through the workspace by choosing a non singular actuation mode for any position of the mobile platform. ...
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Citations
... The NAVARO II robot, whose transmission system is studied here, is a novel variable actuation mechanism based on modified 3-RPR parallel kinematics where the second revolute joint of each leg is replaced by a scissor (Chablat and Rolland, 2018). Such modification gives a number of benefits and allows excluding kinematic parallelograms that are traditionally used in similar manipulators. ...
The paper deals with stiffness modeling of NAVARO II transmission system, which is a novel variable actuation mechanism based on active and passive pantographs. The desired models are obtained using the enhanced matrix structural analysis (MSA) approach that is able to analyze the under-actuated and over-constrained structures with numerous passive joints. Depending on the pantograph type, the models operate with the matrices of size 252x288 and 264x294 suitable for parametric optimization of the entire manipulator.
Parallel manipulators, also called parallel kinematics machines (PKM), enable robotic solutions for highly dynamic handling and machining applications. The safe and accurate design and control necessitates high-fidelity dynamics models. Such modeling approaches have already been presented for PKM with simple limbs (i.e. each limb is a serial kinematic chain). A systematic modeling approach for PKM with complex limbs (i.e. limbs that possess kinematic loops) was not yet proposed despite the fact that many successful PKM comprise complex limbs.
This paper presents a systematic modular approach to the kinematics and dynamics modeling of PKM with complex limbs that are built as serial arrangement of closed loops. The latter are referred to as hybrid limbs, and can be found in almost all PKM with complex limbs, such as the Delta robot. The proposed method generalizes the formulation for PKM with simple limbs by means of local resolution of loop constraints, which is known as constraint embedding in multibody dynamics. The constituent elements of the method are the kinematic and dynamic equations of motions (EOM), and the inverse kinematics solution of the limbs, i.e. the relation of platform motion and the motion of the limbs. While the approach is conceptually independent of the used kinematics and dynamics formulation, a Lie group formulation is employed for deriving the EOM. The frame invariance of the Lie group formulation is used for devising a modular modeling method where the EOM of a representative limb are used to derived the EOM of the limbs of a particular PKM. The PKM topology is exploited in a parallel computation scheme that shall allow for computationally efficient distributed evaluation of the overall EOM of the PKM. Finally, the method is applied to the IRSBot-2 and a 3RR[2RR]R Delta robot, which is presented in detail.
