Thierry Laliberté

Simulation and design of underactuated mechanical hands

Abstract The design of underactuated mechanical hands is addressed in this article. The objective of the research is to design a robust mechanical hand capable of performing industrial tasks involving the grasping of a wide variety of objects with large forces. To this end, the taxonomy of the grasps is first reviewed. Then, the principle of underactiation—which leads to shape adaptation of the hands—is introduced and a review of the existing underactuated mechanical hands is provided. Architectures of two-degree-of-freedom underactuated fingers are then proposed and a simulation tool is designed to analyze their behavior. It is shown that underactuation is a very promising avenue when only grasping is required (no manipulation). Simulation results are given and discussed in order to illustrate the usefulness of the simulator and general design guidelines are proposed. Finally, an underactuated finger is selected and this finger is used in the design of a three fingered hand. Grasp—chosen from the taxonomy—which can be performed with this hand are then illustrated. The design presented here demonstrates that the use of underactuation can lead to versatile grasping capabilities with reduced complexity.

An anthropomorphic underactuated robotic hand with 15 dofs and a single actuator

This paper presents the design and experimental validation of an anthropomorphic underactuated robotic hand with 15 degrees of freedom and a single actuator. First, the force transmission design of underactuated fingers is revisited. An optimal geometry of the tendon-driven fingers is then obtained. Then, underactuation between the fingers is addressed using differential mechanisms. Tendon routings are proposed and verified experimentally. Finally, a prototype of a 15-degree-of-freedom hand is built and tested. The results demonstrate the feasibility of a humanoid hand with many degrees of freedom and one single degree of actuation.

SHaDe, a new 3-DOF haptic device

This paper presents a new type of haptic device using spherical geometry. The basic idea of haptic devices is to provide users with feedback information on the motion and/or force that he or she generates. Haptic devices have several potential applications such as, for example, fine compliant assembly, VR environment simulation, and high-precision teleoperation, especially in hazardous or hostile areas. The particular architecture of the spherical haptic device developed here will be presented and its advantages will be highlighted. Then, its basic kinematic properties, which shall be used for control and geometric optimization purposes, will be reviewed. The design optimization itself will then highlight some important features of the mechanism. The control scheme and real-time force feedback issues will then be presented. Finally, the results obtained with the prototype will be discussed.

Static balancing of 3-DOF planar parallel mechanisms

The static balancing of planar 3-DOF parallel mechanisms is addressed in this paper. Static balancing is defined as the set of conditions on mechanism dimensional and inertial parameters which, when satisfied, ensure that the weight of the links does not produce any torque (or force) at the actuators for any configuration of the mechanism, under static conditions. For the mechanisms studied here, conditions for static balancing are obtained, and it is shown that balancing is generally possible, even when the dimensional parameters are imposed, which is a useful property since dimensional parameters are usually obtained from kinematic design or optimization. Then, the conditions for the static balancing of the same mechanisms are derived for designs in which elastic elements are included. Finally, examples of balanced mechanisms are given. A dynamic study is performed.

Static Balancing of Spatial Parallel Platform Mechanisms—Revisited

This article discusses the development of statically balanced spatial parallel platform mechanisms. A mechanism is statically balanced if its potential energy is constant for all possible configurations. This property is very important for robotic manipulators with large payloads, since it means that the mechanism is statically stable for any configuration, i.e., zero actuator torques are required whenever the manipulator is at rest. Furthermore, only inertial forces and moments have to be sustained while the manipulator is moving. The application that motivates this research is the use of parallel platform manipulators as motion bases in commercial flight simulators, where the weight of the cockpit results in a large static load. We first present a class of spatial parallel platform mechanisms that is suitable for static balancing. The class of mechanisms considered is a generalization of the manipulator described by Streit (1991, Spatial Manipulator and Six Degree of Freedom Platform Spring Equilibrator Theory, in Second National Conference on Applied Mechanisms and Robotics, VIII.B, pp. 1-1-1-6). Then sufficient conditions on the kinematic parameters that guarantee static balancing are derived for this class. Finally a particular mechanism is studied in more detail to show the practicability of its design.

On the Design of a Mechanically Programmable Underactuated Anthropomorphic Prosthetic Gripper

This paper introduces a novel underactuated anthropomorphic gripper for prosthetic applications. In order to extend the grasping capabilities of underactuated prosthetic grippers and improve the force transmission ratio, a mechanical lever is mounted inside the palm that allows a proper distribution of the forces and provides mechanical advantage. A static model is developed and the possibilities offered by the lever transmission are investigated. Also, a compact mechanism is introduced to synchronize the motion of the four fingers. Additionally, a mechanical selector is designed that functions as a means of mechanically programming the motion of the fingers by selectively blocking their closing motion. Finally, a prototype, including all the above features, is described and experimental validation is briefly reported. [DOI: 10.1115/1.4025493]

Singularity-Free Kinematically Redundant Planar Parallel Mechanisms With Unlimited Rotational Capability

This paper introduces a novel family of singularity-free kinematically redundant planar parallel mechanisms that have unlimited rotational capabilities. The proposed mechanisms are akin to conventional three-degree-of-freedom planar parallel mechanisms. By introducing a novel kinematically redundant arrangement, four-degree-of-freedom parallel mechanisms are obtained that can completely alleviate singularities and provide unlimited rotational capabilities. The kinematics of the mechanisms are derived, and the Jacobian matrices are obtained. It is shown that the singularities of this type of mechanism are governed by the orientation of a passive link connecting the redundant leg to the platform and that the latter orientation is easily controlled using the kinematic redundancy, thereby alleviating all direct kinematic singularities. An example mechanism is proposed, and a prototype is demonstrated. Example trajectories that include full cycle rotations are shown. The prototype also illustrates the use of the kinematic redundancy for an auxiliary task, namely grasping.

A Compliant Rolling Contact Joint and Its Application in a 3-DOF Planar Parallel Mechanism With Kinematic Analysis

This paper first presents the concept and the fabrication of a new type of compliant rolling joint which combines the advantages of compliant mechanisms with those of rolling link mechanisms. In this joint, flexible bands create the necessary constraints to enforce a rolling movement between two links. Then, the rapid prototyping techniques used for the compliant rolling joint fabrication are described. The kinematics of one application of this joint in a 3-DOF planar parallel mechanism are then presented. A semigraphical method was used to find the solutions to the inverse kinematic problem. Finally, the workspace analysis and the velocity equations are presented.Copyright

A Friendly Beast of Burden: A Human-Assistive Robot for Handling Large Payloads

This article presents a novel robotic assistive device for the handling of large payloads. The design of the robot is based on the application of the following fundamental mechanical principles: inertia is minimized, a parallel closed-loop cable/belt routing system is used to kinematically decouple the transmission from fixed actuators and to the end-effector, and variable static balancing is used to minimize the actuation forces required for vertical motion. As a result, the device requires only low power, thereby improving safety, and can be operated manually, even in the event of a power failure (with minimum backup power for brake release). A novel force/torque sensor is also introduced along with a control algorithm based on variable admittance that provides a very intuitive interface for physical human-robot cooperation. Finally, a full-scale prototype integrating all of the above concepts is presented.

A First Semimanual Device for Clinical Intramuscular Repetitive Cell Injections

Intramuscular cell transplantation in humans requires so far meticulous repetitive cell injections. Performed percutaneously with syringes operated manually, the procedure is very time consuming and requires a lot of concentration to deliver the cells exactly in the required region. This becomes impractical and inaccurate for large volumes of muscle. In order to accelerate this task, to render it more precise, and to perform injections more reproducible in large volumes of muscle, we developed a specific semimanual device for intramuscular repetitive cell injections. Our prototype delivers very small quantities of cell suspension, homogeneously throughout several needles, from a container in the device. It was designed in order to deliver the cells as best as possible only in a given subcutaneous region (in our case, skeletal muscles accessible from the surface), avoiding wasting in skin and hypodermis. The device was tested in monkeys by performing intramuscular allotransplantations of beta-galactosidase-labeled myoblasts. During transplantations, it was more ergonomic and considerably faster than manually operated syringes, facilitating the cell graft in whole limb muscles. Biopsies of the myoblast-injected muscles 1 month later showed abundant beta-galactosidase-positive myofibers with homogeneous distribution through the biopsy sections. This is the first device specifically designed for the needs of intramuscular cell transplantation in a clinical context.