Reymond Clavel

The WalkTrainer—A New Generation of Walking Reeducation Device Combining Orthoses and Muscle Stimulation

This paper presents a novel reeducation device for paraplegics that combines hybrid orthoses and closed-loop electrical muscle stimulation. Based on the so called cyberthosis concept, the WalkTrainer enables an active muscular participation of the subject in the walking reeducation process by the mean of closed-loop muscle stimulation. The WalkTrainer is also equipped with a leg and pelvic orthosis, an active bodyweight support, and motorized wheels to allow true over ground deambulation. This paper will focus on the development of the WalkTrainer, the presentation of the control strategies, and also give some preliminary results of the first clinical trials.

Argos: A Novel 3-DoF Parallel Wrist Mechanism:

This article presents a novel parallel spherical mechanism called Argos with three rotational degrees of freedom. Design aspects of the first prototype built of the Argos mechanism are discussed. The direct kinematic problem is solved, leading always to four nonsingular configurations of the end effector for a given set of joint angles. The inverse-kinematic problem yields two possible configurations for each of the three pantographs for a given orientation of the end effector. Potential applications of the Argos mechanism are robot wrists, orientable machine tool beds, joy sticks, surgical manipulators, and orientable units for optical components. Another pantograph based new structure named PantoScope having two rotational DoF is also briefly introduced.

Kinematic calibration of the parallel Delta robot

This article deals with the kinematic calibration of the Delta robot. Two different calibration models are introduced: The first one takes into account deviations of all mechanical parts except the spherical joints, which are assumed to be perfect (“model 54”), the second model considers only deviations which affect the position of the end-effector, but not its orientation, assuming that the “spatial parallelogram” remains perfect (“model 24”). A measurement set-up is presented which allows to determine the end-effectors position and orientation with respect to the base. The measurement points are later be used to identify the parameters of the two calibration model resulting in an accuracy improvement of a factor of 12.3 for the position and a factor of 3.7 for the prediction of the orientation.

Design of parallel robots in microrobotics

During the past few years, there has been an increasing demand in the field of precision engineering for fine motion in multi-degrees of freedom systems. These applications motivated the development of a new robotics field called microrobotics. In this paper, we review both the design guidelines for microrobots and the advantages of using parallel robots in very high precision applications. Parallel micromanipulators using elastic joints as well as structures manufactured in single solid and metallic bellows are introduced.

The PantoScope: a spherical remote-center-of-motion parallel manipulator for force reflection

Force reflecting manual man-machine interfaces can provide the user with useful kinesthetic information in teleoperation tasks and virtual reality applications. In this paper we discuss the design of a novel spherical remote-center-of-motion manipulator for force reflection in a laparoscopic surgery simulation environment. A description of the pantograph-linkage based parallel structure is presented together with a discussion of its direct and inverse geometric models, instantaneous kinematics and statics, and usable workspace.

In Situ Electron Microscopy Mechanical Testing of Silicon Nanowires Using Electrostatically Actuated Tensile Stages

Two types of electrostatically actuated tensile stages for in situ electron microscopy mechanical testing of 1-D nanostructures were designed, microfabricated, and tested. Testing was carried out for mechanical characterization of silicon nanowires (SiNWs). The bulk micromachined stages consist of a comb-drive actuator and either a differential capacitive sensor or a clamped-clamped beam force sensor. High-aspect-ratio structures (height/gap = 20) were designed to increase the driving force of the geometrically optimized actuator and the sensitivity of the capacitive sensor. The actuator stiffness is kept low to enable high tensile force to be exerted in the specimen rather than in the suspensions of the comb drive. Individual SiNWs were mounted on the devices by in situ scanning electron microscopy nanomanipulation, and their tensile properties were determined to demonstrate the device capability. The phosphorus-doped SiNWs, which were grown in a bottom-up manner by the vapor-liquid-solid process, show an average Youngs modulus of (170.0 ± 2.4) GPa and a tensile strength of at least 4.2 GPa. Top-down electroless chemically etched SiNWs, with their long axis along the [100] direction, show a fracture strength of 5.4 GPa.

Study of the sources of inaccuracy of a 3 DOF flexure hinge-based parallel manipulator

In this paper a 3 DOF in translation high-precision parallel manipulator having flexure hinges is considered for the purpose of studying its performances in terms of absolute positioning accuracy in presence of different sources of inaccuracy. Manufacturing errors, gravity and temperature gradients are the sources of inaccuracy analyzed by means of FEM simulation models. The obtained data is used to benchmark the different sources studied and to establish a theoretical limit for the positioning performances of the manipulator. The kinematic analysis is performed using simulation models.

NanoLab: A nanorobotic system for automated pick-and-place handling and characterization of CNTs

Carbon nanotubes (CNTs) are one of the most promising materials for nanoelectronic applications. Before bringing CNTs into large-scale production, a reliable nanorobotic system for automated handling and characterization as well as prototyping of CNT-based components is essential. This paper presents the NanoLab setup, a nanorobotic system that combines specially developed key components such as electrothermal microgrippers and mobile microrobots inside a scanning electron microscope. The working principle and fabrication of mobile microrobots and electrothermal microgripper as well as their interaction and integration is described. Furthermore, the NanoLab is used to explore novel key strategies such as automated locating of CNTs for pick-and-place handling and methods for electrical characterization of CNTs. The results have been achieved within the framework of a European research project where the scientific knowledge will be transfered into an industrial system that will be commercially available for potential customers.

Micropositioners for microscopy applications based on the stick-slip effect

Piezo actuators are widely used for precision positioning purposes where a submicron resolution is needed. Among the possible means to increase the working range of those actuators whose stroke is, depending on the material, usually limited to a small fraction of the actuator length, is a stepping motion of the actuator. We use a stepping motion based on the stick and slip effect in order to achieve a long range while maintaining the advantage of a virtually unlimited resolution. In this paper we introduce miniature x-y-stages dedicated to the manipulation of samples under a microscope. As previous setups and experiments have shown, a parallel kinematic structure for positioning purposes in microscopy or micro assembly is not well suited because x and y motion of the actuators have an influence on each other. A system with a serial kinematic structure has therefore been developed. The proposed device will provide the same capabilities as existing motorized stages, but at a lower cost than manual positioning stages and at a very compact size.

Design of a new lower extremity orthosis for overground gait training with the WalkTrainer

A new set of lower limb orthoses was developed for the WalkTrainer project. This mobile reeducation device for paralyzed people allows overground gait training combining closed loop electrical muscle stimulation and lower limb guiding while walking. An active body weight support system offers precise body weight unloading during locomotion. A 6 DOF parallel robot moves the pelvis in any desired position and orientation. The lower extremity orthosis is composed of two key parts. First, a purely passive lightweight exoskeleton acts as the interface between the human leg and the machine. A 1 DOF knee orthotic joint is also designed to prevent hyperextension. Second, the active part - composed of a mechanical leg equipped with motors and sensors - is located behind each human leg, with its base fixed to the WalkTrainer base frame. The two kinematic chains are connected with appropriate linkages at the thigh and the ankle joint. Actuation of the hip, knee and ankle joints is thus provided for their flexion/extension axis. The active mechanism operates only within the sagittal plane and guides the ankle-foot subsystem. Thigh and shank add/abduction movements are possible and even essential since the pelvis moves in a 3D space. This achievement prevents the scissors effect while allowing natural walking motion at the other joints. This paper describes the design and development of the lower extremity orthosis. Starting from a biomechanical approach, the needed actuation and the mechanical structure are discussed as well as the interface between the patient and the robot.