Patrice Lambert

A Novel 5 DOF Fully Parallel Robot Combining 3T1R Motion and Grasping

This paper presents an innovative 5 DOF robot that generates 3T1R motion (3 translations + 1 rotation) plus a linear grasping motion. To generate this type of grasping motion, a robot needs two end-effectors. Grasping motions are usually generated by adding a grasping device at the top of an already existing robot or by coordinating two distinct robots. We propose in this paper a new robot architecture which includes the grasping degree of freedom as a part of the mechanism itself. The two end-effectors of the mechanism are mounted on an articulated platform and can move together in a 3T1R motion and their distance to each other can be controlled to generate the grasping capability. The 5 actuators are located on the base and are connected with five identical legs to the two end-effectors using only mechanical links, forming a fully parallel robot with 5 DOF. The architecture of the robot will be presented in detail. Then, we will describe the kinematics needed for the control of the robot. Finally, geometric optimization results will be presented and discussed.© 2010 ASME

A Haptic Tele-operated System for Microassembly

A tele-haptic system for microassembly applications is currently being developed at the Delft University of Technology, with the goal of achieving superior performance by providing enhanced feedback to the human operator. Assembly of a micro-harmonic drive is used as a benchmark to fully evaluate the proposed tele-haptic system by investigating the control strategies and the individual subsystems: master device, microgrippers and slave system. The master device will be comprised of a parallel robot with a built-in gripper. The slave system and end effector are focused on providing efficient and effective force feedback of the interactions on the microenvironment to the human operator, in addition to detecting position and orientation of the object being grasped. Novel control strategies are also investigated to allow the transmission of high frequency transients to the operator, carrying information from hard contact interactions between the microgripper and the part to be assembled.

Jacobian-based stiffness analysis method for parallel manipulators with non-redundant legs

Stiffness is an important element in the model of a parallel manipulator. A complete stiffness analysis includes the contributions of joints as well as structural elements. Parallel manipulators potentially include both actuated joints, passive compliant joints, and zero stiffness joints, while a leg may impose constraints on the end-effector in the case of lower mobility parallel manipulators. Additionally, parallel manipulators are often designed to interact with an environment, which means that an external wrench may be applied to the end-effector. This paper presents a Jacobian-based stiffness analysis method, based on screw theory, that effectively considers all above aspects and which also applies to parallel manipulators with non-redundant legs.

Self Dual Topology of Parallel Mechanisms with Configurable Platforms

This paper presents first an analysis of the topology of mechanisms via Graph Theory and Screw Theory and next the principle of dual mechanisms in terms of their mobility and overconstraints. Using dual graphs, the graph representations of the mechanisms that are dual to hybrid and Delta mechanisms are revealed. The concept of parallel mechanisms with configurable platforms (PMCPs) is introduced and it is shown that the graph reduction of PMCPs always results in a wheel graph, which has the interesting property of being self-dual. In case of self dual topology, it is then possible to directly convert any method developed for their mobilty analysis into an overconstraint analysis method and vice versa. This self dual topology property can also be exploited to create new PMCPs and is an important aspect in the future development of a type synthesis method that includes PMCPs.

A novel parallel haptic device with 7 degrees of freedom

This paper introduces a novel parallel architecture that provides 6 DOF motion and 1 DOF grasping capabilities while all the motors are located at the base. Parallel robotic devices are widely used now in haptic applications, thanks to their high stiffness and low inertia, which improve the mechanical bandwidth of the device. Classical parallel haptic devices usually do not provide grasping capabilities since all motors are located on the base. Grasping capabilities is sometime desirable to allow the operator to feel the shape and stiffness of the manipulated objects. Thanks to a novel configurable platform, the grasping capability of this haptic device is part of the mechanical architecture itself and can be fully controlled by base-located motors.

Kinematic Design of Two Elementary 3DOF Parallel Manipulators with Configurable Platforms

Parallel Manipulators with Configurable Platforms (PMCPs) have platforms with internal degrees of freedom and form a class of manipulators that is not covered by existing type synthesis methods. Because the minimum number of legs for a PMCP is three, fully parallel 3DOF PMCPs may be considered an elementary subset of PMCPs. To support the extension of type synthesis methods to PMCPs, this paper presents the first kinematic designs of manipulators from this subset. A structured design method has led to the kinematic design of two spatial manipulators that are both capable of independently performing one translation, one rotation and one internal platform motion.

Parallel robots with configurable platforms: Fundamental aspects of a new class of robotic architectures

This paper introduces general and fundamental aspects of a new class of parallel robots termed “parallel robots with configurable platforms”. The concept behind parallel mechanisms with configurable platforms is that the rigid link (non-configurable) end-effector is replaced by an additional closed-loop chain (the configurable platform). Some of the links of this closed loop are attached to the limbs so both the position and the configuration of the platform can be fully controlled from the motors located on the base. They retain the advantages of classical parallel robots, i.e. that all the motors are grounded on the base, while offering mechanical grasping capabilities via multiple contact points. Despite the few studies that have been done yet on the subject, the possible range of applications for this type of architecture is promising since it would be suitable for any application requiring both controlled grasping capabilities and high dynamic performance. This paper provides some preliminary results regarding the topology, mobility, overconstraints, Jacobian matrix, singularities and type synthesis of parallel robots with configurable platforms.

An Adjustable Constant Force Mechanism Using Pin Joints and Springs

This paper presents a novel constant force mechanism based on a 11-revolute joints spatial linkage using simple pin joints and two regular springs. Passive linear sliders with ball bearings are not suitable for certain applications such as in medical environment or for miniaturization. Using only revolute joints in the mechanism allows for replacing all ball bearings with PTFE pin joints, which can be made smaller than ball bearings and are bio-compatible. Pin joints however have the disadvantage of generating friction, which can affect the quality of the constant force at the output link. This paper introduces the new pin joints constant force mechanism and presents an analysis of the effect of the friction generated by the joints on the output force.

Static Balancing of Translational Parallel Mechanisms

Static balancing is a technique to create static equilibrium throughout a certain range of motion. Static balancing for spatially moving parallel manipulators tends to result in considerable added complexity which hampers application. This paper presents a simple static balancing technique for the subclass of translational parallel manipulators such as the Delta robot. Mathematically perfect static balance is achieved without addition of links. Only springs need to be added. The concept and the balancing conditions will be presented. A prototype is being manufactured at the time of writing which demonstrates the feasibility of the concept.

Generalized Jacobian Analysis of Parallel Manipulators With Multiple End-Effectors

This paper presents a methodology for the Jacobian analysis of parallel manipulators with multiple end-effectors (PMxE). The end-effector velocity state of a PMxE is described by one twist of a principal end-effector with respect to the base and a set of relative twists of the remaining end-effectors with respect to the principal end-effector The twist of each terminal link with respect to the principal end-effector is then expressed as a linear function of the relative twists, which enables an extension of the generalized Jacobian analysis to PMxE. The presented methodology is detailed for parallel manipulators with two end-effectors, where a planar 6-RRR manipulator with a 2-RRR internal closed-loop is used as an example.Copyright