Philippe Garrec

ABLE, an innovative transparent exoskeleton for the upper-limb

This paper presents ABLE, an innovative exoskeleton for the upper limb currently under development at CEA-LIST Interactive Robotics Unit. Its distinctive high performance mechanical transmissions - screw and cable patented arrangement - and its integrated architecture makes it the very first of its category. The first 4 axis model is described here but more complete models are already planned: a 7 axis model as well as portable versions. Its back-drivable, high efficiency, low inertia actuators provide a high capacity (around 40 N continuous effort at the hand) and allow hybrid force-position control without requiring any force sensor. Its first application is currently a research program in rehabilitation (BRAHMA project) and professional use is already in view. Assistance tasks for disabled persons (carrying a bottle) are also typical tasks to be performed by ABLE as well as intuitive telerobotics, haptic device for VR, and sport training, etc. Furthermore, its versatility and simple design allow industrial versions to become soon available.

Design and acceptability assessment of a new reversible orthosis

We present a new device aimed at being used for upper limb rehabilitation. Our main focus was to design a robot capable of working in both the passive mode (i.e. the robot shall be strong enough to generate human-like movements while guiding the weak arm of a patient) and the active mode (i.e. the robot shall be able of following the arm without disturbing human natural motion). This greatly challenges the design, since the system shall be reversible and lightweight while providing human compatible strength, workspace and speed. The solution takes the form of an orthotic structure, which allows control of human arm redundancy contrarily to clinically available upper limb rehabilitation robots. It is equipped with an innovative transmission technology, which provides both high gear ratio and fine reversibility. In order to evaluate the device and its therapeutic efficacy, we compared several series of pointing movements in healthy subjects wearing and not wearing the orthotic device. In this way, we could assess any disturbing effect on normal movements. Results show that the main movement characteristics (direction, duration, bell shape profile) are preserved.

Dynamic identification of robots with a dry friction model depending on load and velocity

Usually, the joint transmission friction model for robots is composed of a viscous friction force and of a constant dry sliding friction force. However, according to the Coulomb law, the dry friction force depends linearly on the load driven by the transmission. It follows that this effect must be taken into account for robots working with large variation of the payload or inertial and gravity forces, and actuated with transmissions as speed reducer, screw-nut or worm gear. This paper proposes a new inverse dynamic identification model for n degrees of freedom (dof) serial robot, where the dry sliding friction force is a linear function of both the dynamic and the external forces, with a velocity-dependent coefficient. A new identification procedure groups all the joint data collected while the robot is tracking planned trajectories with different payloads to get a global least squares estimation of inertial and new friction parameters. An experimental validation is carried out with a joint of an industrial robot.

TAO2000 V2 computer‐assisted force feedback telemanipulators used as maintenance and production tools at the AREVA NC–La Hague fuel recycling plant

During a 15-year joint research program, French Atomic Energy Agency Interactive Robotics Laboratory (CEA LIST) and AREVA have developed several remote operation devices, also called telerobots. Some of them are now commonly used for maintenance operations at the AREVA NC (Nuclear Cycle)–La Hague reprocessing plant. Since the first maintenance operation in 2005, several other successful interventions have been realized using the industrial MA23/RX170 telemanipulation system. Moreover, since 2010, the through-the-wall tele-robot named MT200 TAO based on the slave arm of the MSM MT200 (La Calhene TM), has been evaluated in an active production cell at the AREVA NC–La Hague fuel recycling plant. Although these evaluations are ongoing , the positive results obtained have led to an update and industrialization program. All these developments are based on the same generic control platform, called TAO2000 V2. TAO2000 V2 is the second release of the CEA LIST core software platform dedicated to computer aided force-feedback teleoperation (TAO is the French acronym for computer aided teleoperation). This paper presents all these developments resulting from the joint research program CEA LIST/AREVA. The TAO2000 V2 controller is first detailed, and then two maintenance operations using the industrial robot RX170 are presented: the removal of the nuclear fuel dissolver wheel rollers and the cleanup of the dissolver wheel interbucket spaces. Finally, the new MT200 TAO system and its evaluations at the AREVA NC–La Hague facilities are discussed. C 2011 Wiley Periodicals, Inc.

New dry friction model with load- and velocity-dependence and dynamic identification of multi-DOF robots

Usually, the joint transmission friction model for robots is composed of a viscous friction force and of a constant dry sliding friction force. However, according to the Coulomb law, the dry friction force depends linearly on the load driven by the transmission, which has to be taken into account for robots working with large variation of the payload or inertial and gravity forces. Moreover, for robots actuating at low velocity, the Stribeck effect must be taken into account. This paper proposes a new inverse dynamic identification model for n degrees of freedom (dof) serial robot, where the dry sliding friction force is a linear function of both the dynamic and the external forces, with a velocity-dependent coefficient. A new sequential identification procedure is carried out. At a first step, the friction model parameters are identified for each joint (1 dof), moving one joint at a time (this step has been validated in [23]). At a second step, these values are fixed in the n dof dynamic model for the identification of all robot inertial and gravity parameters. For the two steps, the identification concatenates all the joint data collected while the robot is tracking planned trajectories with different payloads to get a global least squares estimation of inertial and new friction parameters. An experimental validation is carried out with an industrial 3 dof robot.

Dedicated and standard industrial robots used as force-feedback telemaintenance remote devices at the AREVA recycling plant

CEA LIST and AREVA have been developing remote operations devices, also called telerobotics for 15 years. These tools were designed for interventions in the AREVA nuclear spent fuel facilities hot cells. From these 15 years of joint research and development, several technological bricks have been industrialized and used at the AREVA La Hague facilities. This article presents some of these bricks and their industrial developments. The “TAO2000” CEA LIST telerobotics generic software controller will be first discussed. This controller has been used to teleoperate dedicated slave arms like the MT200 TAO (an evolution of the conventional wall-transmission mechanical telemanipulator (MSM) [3]) as well as industrial robotic arms like the Stäubli RX robots. Both the MT200 TAO and Stäubli RX TAO telerobotics systems provide force-feedback and are now ready to be used as telemaintenance tools at the AREVA La Hague facilities. Two recent maintenance operations using these tools will be detailed at the end of this paper.

A New Force-Feedback, Morphologically Inspired Portable Exoskeleton

This paper presents a new portable exoskeleton design for superior limbs by the CEA-LIST laboratories. The first model described here (4 axis) is designed to apply forces in 3 directions. The first application is foreseen as an assistance device to enable a disabled person to carry an object such as a teapot or water bottle. It is designed as a base for more complete systems. A partial realization of it is presented for the first time. The high potential of the actuators used both in terms of back drivability and force capacity, allows hybrid force-position control laws making it possible to cover a broad range of applications: rehabilitation, assistance, force feedback master arm for telerobotics, sport training, and a virtual reality workbench

EMY: a dual arm exoskeleton dedicated to the evaluation of Brain Machine Interface in clinical trials

EMY (Enhancing MobilitY) is an exoskeleton dedicated to the evaluation of Brain Machine Interface during clinical trials. This paper presents the first version of EMY restricted to upper limbs with four actuated joints per arm. Since an evaluation of a BMI controlled exoskeleton by a disabled person requires clinical trials, a risk management process should be conducted with medical standards as references. More than an exhaustive architecture description of EMY, this paper details relationships between risk management and the proposed technical solutions in order to justify design options. EMYs design is upgradable and future versions of EMY will concern the addition of lower limbs and prehension capability to ultimately obtain a full-body exoskeleton suitable for testing brain controlled locomotion and manipulation tasks.

Dynamic modeling and identification of joint drive with load-dependent friction model

Friction modeling is essential for joint dynamic identification and control. Joint friction is composed of a viscous and a dry friction force. According to Coulomb law, dry friction depends linearly on the load in the transmission. However, in robotics field, a constant dry friction is frequently used to simplify modeling, identification and control. That is not accurate enough for joints with large payload or inertial and gravity variations and actuated with transmissions as speed reducer, screw-nut or worm gear. A new joint friction model taking dynamic and external forces into account is proposed in this paper. A new identification process is proposed, merging all the joint data collected while the mechanism is tracking exciting trajectories and with different payloads, to get a global LS estimation in one step. An experimental validation is carried out with a prismatic joint composed of a Star high precision ball screw drive positioning unit.