On the Dynamic Properties of Flexible Parallel Manipulators in the Presence of Type 2 Singularities

International audienceIn the present paper, we expand information about the conditions for passing through Type 2 singular configurations of a parallel manipulator. It is shown that any parallel manipulator can cross the singular configurations via an optimal control permitting the favourable force distribution, i.e. the wrench applied on the end-effector by the legs and external efforts must be reciprocal to the twist along the direction of the uncontrollable motion. The previous studies have proposed the optimal control conditions for the manipulators with rigid links and flexible actuated joints. The different polynomial laws have been obtained and validated for each examined case. The present study considers the conditions for passing through Type 2 singular configurations for the parallel manipulators with flexible links. By computing the inverse dynamic model of a general flexible parallel robot, the necessary conditions for passing through Type 2 singular configurations are deduced. The suggested approach is illustrated by a 5R parallel manipulator with flexible elements and joints. It is shown that a 16 th order polynomial law is necessary for the optimal force generation. The obtained results are validated by numerical simulations carried out using the software ADAMS

Dynamic Balancing of the SCARA robot

International audienceThis paper deals with the complete shaking force and shaking moment balancing of the four degrees of freedom SCARA robot. Dynamic reaction forces on the frame of the manipulator are eliminated by traditional approach making the total mass center of the moving links stationary. Reaction moments on the frame of the manipulator are eliminated by optimal control of the end-effector, which rotates with prescribed acceleration. A numerical simulation carried out on the software ADAMS illustrates that such a balanced SCARA robot transmits no inertia loads to surrounding, i.e. the sum of all ground bearing forces and their moments are eliminated

On the Dynamic Properties of Rigid-Link Flexible-Joint Parallel Manipulators in the Presence of Type 2 Singularities

International audienceIn our previous work [1], the dynamic properties of rigid-link parallel manipulators, in the presence of Type 2 singularities, have been studied. It was shown that any parallel manipulator can pass through the singular positions without perturbation of motion if the wrench applied on the end-effector by the legs and external efforts of the manipulator are orthogonal to the twist along the direction of the uncontrollable motion. This condition was obtained using symbolic approach based on the inverse dynamics and the study of the Lagrangian of a general rigid-link parallel manipulator. It was validated by experimental tests carried out on the prototype of a four-degrees-of-freedom parallel manipula-tor. However, it is known that flexibility of the mechanism may not always been neglected. Indeed, joint flexibility is the main source contributing to overall manipulator flexibility and it leads to the trajectory distortion. Therefore, in this paper, the condition for passing through a Type 2 singularity of parallel manipulators with flexible joints is studied. The suggested technique is illustrated by the example of a 5R parallel manipula-tor with flexible joints. It is shown that passing through singularity is possible if the twelfth order polynomial trajectory planning is applied. The obtained results are validated by numerical simulations carried out using the ADAMS software

On The Dynamic Properties of Flexible Parallel Manipulators in the Presence of Payload and Type 2 Singularities

International audienceIt is known that a parallel manipulator at a singular configuration can gain one or more degrees of freedom and become uncontrollable. In our recent work [1], the dynamic properties of rigid-link parallel manipulators, in the presence of Type 2 singularities, have been studied. It was shown that any parallel manipulator can pass through the singular positions without perturbation of motion if the wrench applied on the end-effector by the legs and external efforts is orthogonal to the twist along the direction of the uncontrollable motion. This condition was obtained using symbolic approach based on the inverse dynamics and the study of the Lagrangian of a general rigid-link parallel manipulator. It was validated by experimental tests carried out on the prototype of a four-degrees-of-freedom parallel manipulator. However, it is known that the flexibility of the mechanism may not always been neglected. Indeed, for robots, joint flexibility can be the main source contributing to overall manipulator flexibility and can lead to trajectory distortion. Therefore, in our second paper [2], the condition of passing through a Type 2 singularity for parallel manipulators with flexible joints has been studied. In the present paper, we expand information about the dynamic properties of parallel manipulators in the presence of Type 2 singularity by including in the studied problem the link flexibility and the payload. The suggested technique is illustrated by a 5R parallel manipulator with flexible elements (actuated joints and moving links) and a payload. The obtained results are validated by numerical simulations carried out using the software ADAMS

Complete Shaking Force and Shaking Moment Balancing of the Position-Orientation Decoupled PAMINSA Manipulator

International audienceThis paper deals with the complete shaking force and shaking moment balancing of the position-orientation decoupled PAMINSA manipulator. The dynamic reaction forces on the manipulator's base are eliminated by making the total mass center of the moving links stationary. The reaction moments on the frame are eliminated by optimal control of the end-effector, which rotates with prescribed velocity. The numerical simulations carried out using ADAMS software demonstrate that the balanced manipulators transmit no inertia loads to their bases

Complete Shaking Force and Shaking Moment Balancing of In-line Four-bar Linkages by adding a Class-two RRR or RRP Assur Group

International audienceThis paper deals with the complete shaking force and shaking moment balancing of planar in-line four-bar linkages with constant input speed. A new solution is discussed, which is carried out without counter-rotations. The complete shaking force and shaking moment balancing is obtained by using a coupler link, which is a physical pendulum and by adding a class-two Assur group with prescribed geometrical and mass parameters. Two types of Assur group are examined: two links group with three revolute joints (RRR) and two links group with two revolute and one prismatic joints (RRP). Numerical simulations carried out using ADAMS software validate the proposed balancing technique and illustrate that the obtained six-bar mechanism is reactionless, i.e. the sum of all ground bearing forces and their moments are eliminated

Singularity Analysis of PAMINSA Manipulators

International audiencePAMINSA (PArallel Manipulator of the I.N.S.A.) is a new family of parallel manipulators from four to six degrees of freedom (DOF), which have been developed at the I.N.S.A. in Rennes. The particularity of these manipulators is the decoupling of displacements in the horizontal plane from its translation along the vertical axis. Such a decoupling improves some mechanical properties of the manipulator making it more efficient. In this paper a singularity analysis of PAMINSA with four, five and six degrees of freedom is presented. The nature of each kind of singularity is discussed

A New Decoupled Parallel Manipulator with Four Degrees of Freedom

International audienceA new 4-DOF parallel manipulator, called the PAMINSA 1 , is presented in this paper. The invented parallel structure consists of two (or three) legs, each one of which is a pantograph mechanism. The architecture of the PAMINSA is such that the platform displacements in the horizontal plane are independent of the translation along the vertical axis. The advantages of this architecture are the simplification of the vertical control based on the linear input-output equation and the improvement of positioning accuracy in the horizontal plane

On the Kinematic, Kinetostatic and Dynamic Properties of Parallel Manipulators in the Presence of Singularity

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Simultaneous Inertia Force/Moment Balancing and Torque Compensation of Slider-Crank Mechanisms

International audienceThis paper proposes a design concept which allows the simultaneous shaking force/shaking moment balancing and torque compensation in slider-crank mechanisms. At first, the shaking force and shaking moment are cancelled via a cam mechanism carrying a counterweight. Then, the spring designed for maintaining contact in this balancing cam mechanism is used for torque minimization. For this purpose, the spring is jointed with a second cam mounted on the input crank. The proposed design concept allows the development of only one device for solving the both mentioned problems. The suggested solution is illustrated by numerical example carried out by using ADAMS software