This paper presents MoonWalker, a lower limb exoskeleton able to sustain part of a user's bodyweight. This orthosis can be used for rehabilitation, to help people having weak legs, or to help those suffering from a broken leg, to walk. It can also be used as an assistive device helping people carrying heavy loads. Its main characteristic is that a passive force balancer provides the force to sustain bodyweight. An actuator is also required, but is used only to shift that force the same side as the leg in stance. Consequently, MoonWalker requires very low energy to work on flat terrains. That motor can provide also a part of the energy to climb stairs or slopes. We believe that this approach can help improving energetic autonomy of lower limb exoskeletons.

The property of form-closure of a grasp, as generally defined in the literature, is based on the assumption that contact points between the hand and the object are fixed in space. However, this assumption is false when considering a grasp exerted by an underactuated hand, since, in this case, it is not possible to control the position of each phalanx independently. In spite of researchers' interest in studying form-closure, none of the available published work on this subject takes into consideration the particular kinematics of underactuated hands. Actually, there are few available tools to qualify or quantify the stability of a grasp exerted by an underactuated hand; thus, the design of underactuated hands mostly results from an intuitive approach. This paper aims to reduce this gap. A classification of underactuated hands is proposed, which is based on the expression of contact forces. This highlights the influence of nonbackdrivable mechanisms introduced in the transmission of the closing motion of the hand on the stability of the grasp. After demonstrating that the original definition of form-closure is not suitable for the underactuated grasps, a more general definition is formulated, which checks the stability of the assembly ``object + hand.'' Using this new definition, a geometric method is proposed for the analysis of first-order form-closure of an underactuated grasp, as well as a simple rule to design a hand capable of achieving first-order form-closed grasps. Finally, a method is proposed for the analysis of higher order form-closure of an underactuated grasp, which is based on a first-order model of the grasp.

This paper presents a predictive force control approach to compensate for the physiological motion induced by both respiratory and heart beating motions during cardiac surgery. It focuses on the design and implementation of the control algorithm in the context of robotized minimally invasive surgery. The controller is based on a linear predictive control loop using the force information applied on the heart by the instrument. Experimental evaluation highlights the performance of the algorithm for compensating 3D physiological motion.

This paper describes the design of a gravity balanced spatial orthosis. Previous works introduced planar mechanisms only and neglected friction. They relied on counterweight or auxiliary parallelograms. The main contributions of this paper are: (i) we succeed in designing a spatial (3D) mechanism and (ii) we analyzed the effects of friction. We designed a very simple system made with two pulleys and two springs in order to ensure gravity compensation. The system is in static equilibrium whatever its posture. It has three passive degrees of freedom at the shoulder and two at the elbow. A prototype of this orthosis is presented at the end of the paper.

This paper proposes a new approach to compensate the physiological motion, induced by respiration and heart beating, for robotized minimally invasive cardiac surgery. The control algorithm, based on a linear predictive control, uses the effort information applied on the heart by the instrument.

This paper presents a new pneumatically driven underactuated hand with two fingers and 3 phalanxes per finger. Two evidences have led the design of this hand. Firstly, the use of pneumatic energy facilitates the underactuation of the hand, indeed a single T-connector suffices to share out one input among two outputs. Secondly, non-backdrivable mechanisms have to be used in the transmission of phalanx's motion so that the hand is capable of producing form-closed grasps. This latter design principle is justified using a newly developed method that permits to study the form-closure property of a grasp exerted by an underactuated hand. Moreover, the intriguing ejection phenomenon is avoided thanks to non-backdrivable mechanisms that prohibit any backward motion of phalanxes when correctly positioned. An original mechanism called the "pneumatic parallelogram" is described, it enables the hand to perform fine pinch grasps. Finally, the optimal design of both fingers is addressed with respect to the force-isotropy of the finger and the positiveness of phalanx forces

Many underactuated grippers with fingers have been developed these last years. Their drawback is that they only ensure conditionally grasp stability. This paper presents a study of the grasp stability of an isotropic underactuated finger, which is made by two phalanxes and uses cams and tendon for actuation. The paper presents also a study of the internal forces developed in the transmission chains. The proposed model serves for the gripper using as for part dimensioning.

This paper presents a new method to study the capability of an underactuated hand to produce form-closed grasps. First, the stability behaviours of different underactuated parallel-jaw grippers are analyzed and compared according to their actuation and transmission mechanisms. Then, both notions of 1st order and 2nd order form-closure are revisited for underactuated hands, since in this particular case the assumption of fixed contacts made in the original definition is false. Therefore, constraints imposed by non-backdrivable mechanisms are introduced into the model of the whole grasp. Finally, a simple geometrical condition, necessary and sufficient for 1st order form-closure is proposed. This permits to conclude on the minimum number of non-backdrivable mechanisms required to produce 1st order form-closed grasps using an underactuated hand

This paper discusses the design of a control system for robotic-assisted surgery with haptic feedback. The operational space control has a position-position teleopearation architecture with the phantom in the loop, enabling telepresence in free-space and contact. The null space control guarantees that surgical kinematic constraints are fulfilled. Both task and posture control run active observers (AOBs) in Cartesian domain, taking into account force, velocity and position signals. Experiments with a D2M2 (direct drive medical manipulator) robot are presented

The BRIGIT project (Bone Resection Instrument Guidance by Intelligent Telemanipulator) aims at developing a surgical robot for orthopedic surgery. This robot should be used as a positioner of a guide providing a mechanical support during bone sawing or drilling. The planned position of the guide is obtained after a registration procedure consisting in collecting anatomical landmarks on the surface of the patient's bone. This can be done in a cooperative mode, by grabbing the tool tip, through an appropriate force control, or in a teleoperated mode via a master device. In order to facilitate the installation of the robot in the operating theatre and to improve its performance, a procedure based on interval analysis has been developed to optimize the robot placement with respect to the patient, the surgical staff, and the obstacles of the environment.

This paper deals with the use of an original dynamic task/posture decoupling control algorithm that allows a robot to achieve motions under the constraint of moving through a fixed point. This work takes place in the context of minimally invasive surgery where the tool is telemanipulated by the surgeon through a penetration point: the trocar fixed on the patient. The algorithm is based on the dynamic control in the operational space of a redundant robot: the total control torque is decoupled into a task behavior torque and a posture behavior torque. By minimizing the contact force applied to the trocar (or equivalently, by forcing to zero the distance between the instrument passing through the trocar and the current location of the trocar), we compute the posture behavior torque guaranteeing that the trocar constraint is satisfied. Simulation results highlight the performance of this algorithm for various trajectories such as straight lines and circles.

The new generation of implanted neuroprostheses allows muscles to be controlled with fine accuracy, high selectivity and the repeatability of the muscle's response can be achieved. Thus, the closed loop control of such systems becomes possible. The SUAW project succeeded in the implantation of an advanced neuroprosthetic device on two patients, but the movement generation remains open loop and is tuned empirically. Nevertheless, the good results obtained give us the opportunity to envisage the system evolves towards closed loop control and automatic synthesis of the stimulation patterns generating the desired movement. To achieve this goal, some preliminary researches have to be carried out, beginning with a specific modelling that can be used in the context of functional electrical stimulation (FES). The main issues concern muscle modelling including the interaction with the skeleton, fatigue, FES parameters as inputs, and the identification of dynamic parameters, and afterwards, the motion synthesis and the closed loop control based on this model. Besides, the scientific approach is the same as in robotics so that the theoretical tools used in the control theory are the same and directly applicable. This paper describes the results obtained in the previous project SUAW and how we attempt, through the new project DEMAR, to enhance the global performances of the system.

This paper presents a novel and safe robotic system for skin harvesting, the first one in reconstructive surgery. It is intended to significantly improve the performance of surgeons who do not regularly perform this operation; the tool, called dermatome, is mounted at the tip of a dedicated robot that precisely controls the pressure on the skin and the harvesting velocity. In this paper, the harvesting task is analyzed and the safety constraints are summarized. Then, the mechanical structure and the functions of the control system are described. Finally, in vivo experimental results on pigs are reported and discussed.

This paper deals with a path planning algorithm for an anthropomorphic robot that must achieve motions (straight line, circle, helix) under the constraint of passing the forearm through a fixed point. This point simulates the penetration point (trocar) in minimally invasive surgery. It has to remain fixed with respect to the patient's body. The modeling and resolution of the constraint are presented. The geometric model and path planning are proposed. Simulation results validate the algorithm.

The paper presents an ongoing research program in robotized reconstructive surgery. We first analyze the action of surgeons harvesting skin, in terms of speed and forces. Then we present the control strategies we have selected and implemented on a redundant robot arm. Finally we present the first experimental results obtained on an animal: this shows that robotized skin harvesting is a possible task.

We have developed a robotic system to assist doctors when they are moving ultrasonic probes on the patient's skin while exerting a given effort. The probes are used to monitor arteries for cardiovascular disease prevention, namely to reconstruct the 3D profile of arteries. A preliminary feasibility study making use of an industrial robot has been made to validate the force control scheme. It has proven the interest of the robotized approach for such a medical application. In order to comply with safety constraints, a dedicated robotic system HIPPOCRATE has been designed. The paper describes the arm and the controller architectures, with emphasis on design strategies selected to meet safety requirements.

A two stage calibration method for the parallel robot Delta 4 is presented. It allows one to identify the offsets on the three first joints and the absolute location of the robot base. It involves a cheap displacement sensor and dedicated targets which can be easily moved on the work area. Intensive simulations show the robustness of the protocol and experimental results validate this procedure.

Nowadays, several general purpose CAD/CAM systems including robotics applications are commercially available. They require large computers facilities and sophisticated graphics workstations. Currently, trends is in dedicated systems which are implemented on micro or minicomputers and are devoted to specific applications. In this paper, such a dedicated interactive system is described with emphasis on the 3D data- base design specifications. Real-time and memory size constraints are keys requirements in the design. So far, this CAD/CAM software is intended for robot programming and CAD of workcells. A specific application involving synthetic vision generated by the system is also described.