Vincent Nabat

Optimal Design of a 4-DOF Parallel Manipulator: From Academia to Industry

This paper presents an optimal design of a parallel manipulator aiming to perform pick-and-place operations at high speed and high acceleration. After reviewing existing architectures of high-speed and high-acceleration parallel manipulators, a new design of a 4-DOF parallel manipulator is presented, with an articulated traveling plate, which is free of internal singularities and is able to achieve high performances. The kinematic and simplified, but realistic, dynamic models are derived and validated on a manipulator prototype. Experimental tests show that this design is able to perform beyond the high targets, i.e., it reaches a speed of 5.5 m/s and an acceleration of 165 m/s2. The experimental prototype was further optimized on the basis of kinematic and dynamic criteria. Once the motors, gear ratio, and several link lengths are determined, a modified design of the articulated traveling plate is proposed in order to reach a better dynamic equilibrium among the four legs of the manipulator. The obtained design is the basis of a commercial product offering the shortest cycle times among all robots available in todays market.

Par4: very high speed parallel robot for pick-and-place

This paper introduces a four-degree-of-freedom parallel manipulator dedicated to pick-and-place. It has been developed with the goal of reaching very high speed. This paper shows that its architecture is particularly well adapted to high dynamics. Indeed, it is an evolution of Delta, H4 and 14 robots architectures: it keeps the advantages of these existing robots, while overcoming their drawbacks. In addition, an optimization method based on velocity using adept motion has been developed and applied to this high speed parallel robot. All these considerations led to experimentations that proved we can reach high accelerations (13 G) and obtain a cycle time of 0.28 s.

A high-speed parallel robot for Scara motions

This paper introduces a new 4 degree-of-freedom parallel robot. It presents its architecture inspired by FlexPicker, an ABB machine based on the Delta architecture, while overcoming its drawbacks. This paper exposes the way to get the geometrical models, and particularly the forward position relationship which can be obtained in a closed form. In a third part, a detailed study of the robot singularities is made by taking into account the not-so-classic internal singularities. Design conditions are obtained for isostatic and over-constrained cases. The robot optimization and its workspace are finally presented.

Schoen flies Motion Generator: A New Non Redundant Parallel Manipulator with Unlimited Rotation Capability

Nowadays an important research effort is devoted to lower mobility parallel manipulators. The existing solutions often suffer from parallel mechanisms drawbacks, i.e. small workspace and limited rotation capability. A new concept of parallel manipulators providing Schoen flies motions (motions of well-known SCARA robot) is introduced in this paper. The proposed manipulator, based on the idea of articulated traveling plate explored by the authors, has an unlimited rotation capability without using motion transformation, ampli fication neither redundancy.

Above 40g acceleration for pick-and-place with a new 2-dof PKM

This paper introduces a new two-degree-of-freedom parallel manipulator producing two translations in the vertical plane. One drawback of existing robots built to realize those dof is their lack of rigidity along the transversal axis, another one being their limited ability to provide very high acceleration. Indeed, these architectures cannot be lightweight and stiff at the same time. The proposed architecture is a spatial mechanism which guarantees a good stiffness along the transversal axis. This parallel architecture is composed by two actuated kinematic chains, and two passive chains built in the transversal plane. The key feature of this robot comes from the passive chains which are coupled for creating a kinematic constraint: the platform stays in one plane. A stiffness analysis shows that the robot can be lighter and stiffer than a classical 2 dof mechanism. A prototype of this robot is presented and preliminary tests show that accelerations above 40 g can be achieved while keeping a low tracking error.

Simplified dynamic modelling and improvement of a four-degree-of-freedom pick-and-place manipulator with articulated moving platform

Abstract This paper deals with high-speed robots for pick-and-place applications with a high rate of output. After mentioning the families of robot architectures that meet the specifications of pick-and-place, parallel kinematics architectures with articulated moving platform are introduced and described. Indeed, this concept seems very promising for this kind of application. After presenting the reasons to select the PAR4 architecture, it is fully described and modelled: position relationships, velocity relationships, and simplified dynamic model. Experimental results from extensive testing show a high performance potentiality. By analysing the experimental results, an improvement is proposed to have a better dynamic balance among the actuators. The improved version of the robot is the one chosen for the industrial development of the QUATTRO parallel robot.

On the Design of a Fast Parallel Robot Based on Its Dynamic Model

A high-speed, four-degree-of-freedom (dof), parallel robot is analysed by considering in detail its dynamic model as well as issues directly linked to its practical design. A small change in its kinematics is then proposed that lead to a dramatic change in its dynamic behaviour, providing room for a radical improvement and a new version of the robot.

Dynamic Modeling and Identification of Par4, A Very High Speed Parallel Manipulator

This paper introduces the dynamic modeling and the identification of Par4, a four-degree-of-freedom parallel manipulator producing Schonflies motions (three translations and one rotation about a fixed axis). First of all, this paper presents how this robot is developed with the goal of reaching very high speed. Indeed, it is an evolution of Delta, H4 and I4 robots architectures: it keeps their advantages while overcoming their drawbacks. Experimentations done with the prototype prove that the robot is able to reach very high accelerations (15 G) and to perform an adept cycle in 0.25 s. In order to improve its dynamic accuracy, a dynamic control could be necessary. Thus, this paper presents the dynamic modeling of the manipulator using a simplified Newton-Euler approach. The originality of this computation is to model the traveling as two separated parts and to determine the dynamic effects applied on each of them. Finally, since a dynamic control requires a good evaluation of dynamic parameters, an experimental dynamic identification is presented

Very fast Schoenflies motion generator

This paper introduces a four-degree-of-freedom parallel manipulator producing Schonflies motions (three translations and one rotation). It has been developed with the goal of reaching very high speed. This paper shows that its architecture is particularly well adapted to high dynamics. Indeed, it is an evolution of delta, H4 and I4 robots architectures: it keeps the advantages of these existing robots, while overcoming their drawbacks. In addition, this paper shows the dynamic modelling of the architecture that is useful for a future dynamic control. Finally, experimental results are shown, and prove that the robot is able to reach high accelerations (13 G) and obtain a cycle time of 0.28 s