Etienne Dombre

HIPPOCRATE: an intrinsically safe robot for medical applications

We have developed a robotic system to assist doctors when they are moving ultrasonic probes on the patients 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 calibration procedure for the parallel robot Delta 4

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.

Image Based Visual Servoing through Nonlinear Model Predictive Control

Image based visual servoing (IBVS) is a vision sensor based control architecture. In classical approach, an image Jacobian matrix maps image space errors into errors in Cartesian space. Then a simple proportional control law can be applied guaranteeing local convergence to a desired set point. One of the main advantage of IBVS is its robustness w.r.t camera and robot calibration errors and image measurement errors. Nevertheless, this scheme can not deal with nonlinear constraint such as joint limits and actuator saturation. Visibility constraint is not ensured with classical IBVS. A new IBVS scheme based on nonlinear model predictive control (NMPC) is proposed considering the direct dynamic model of the robot, its joint and torque limits, the camera projection model and the visibility constraint. Simulations exhibit the efficiency and the robustness of the proposed solution to control a 6 degrees of freedom mechanical system

Ultrasound Image-Based Visual Servoing of a Surgical Instrument Through Nonlinear Model Predictive Control

Ultrasound image-guided interventions are widespread in surgery because of the non-invasive character of the procedures. However, hand/eye synchronization is relatively difficult for a surgeon. Ultrasound image-based visual servoing is one way to perform this kind of surgery. In this work, the control of instrument motion based on ultrasound images through nonlinear model predictive control is investigated. This new scheme ensures the convergence of the instrument to the desired position and also offers the possibility of satisfying constraints such as joint limits, actuator saturation and visibility preserving. This paper describes the proposed controller. The efficiency and the robustness of the proposed solution to control a six degree-of-freedom mechanical system is first illustrated by simulation. Experiments on a Mitsubishi PA10 robot highlight the efficiency of the vision control scheme to handle constraints of ultrasound image-based visual servoing.

Dermarob: A safe robot for reconstructive surgery

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.

MoonWalker, a lower limb exoskeleton able to sustain bodyweight using a passive force balancer

This paper presents MoonWalker, a lower limb exoskeleton able to sustain part of a users 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.

Modeling, performance analysis and control of robot manipulators

Chapter 1. Modeling and Identification of Serial Robots (Wisama KHALIL and Etienne DOMBRE). 1.1. Introduction. 1.2. Geometric modeling. 1.3. Kinematic modeling. 1.4. Calibration of geometric parameters. 1.5. Dynamic modeling. 1.6. Identification of dynamic parameters. 1.7. Conclusion. 1.8. Bibliography. Chapter 2. Modeling of Parallel Robots (Jean-Pierre MERLET and Francois PIERROT). 2.1. Introduction. 2.2. Machine types. 2.3. Inverse geometric and kinematic models. 2.4. Direct geometric model. 2.5. Bibliography. Chapter 3. Performance Analysis of Robots (Philippe WENGER). 3.1. Introduction. 3.2. Accessibility. 3.3. Workspace of a robot manipulator. 3.4. Concept of aspect. 3.5. Concept of connectivity. 3.6. Local performances. 3.7. Conclusion. 3.8. Bibliography. Chapter 4. Trajectory Generation (Moussa HADDAD, Taha CHETTIBI, Wisama KHALIL and Halim LEHTIHET). 4.1. Introduction. 4.2. Point-to-point trajectory in the joint space under kinematic constraints. 4.3. Point-to-point trajectory in the task-space under kinematic constraints. 4.4. Trajectory generation under kinodynamic constraints. .4.5. Examples. .4.6. Conclusion. 4.7. Bibliography. Appendix: Stochastic Optimization Techniques. Chapter 5. Position and Force Control of a Robot in a Free or Constrained Space (Pierre DAUCHEZ and Philippe FRAISSE). 5.1. Introduction. 5.2. Free space control. 5.3. Control in a constrained space. 5.4. Conclusion. 5.5. Bibliography. Chapter 6. Visual Servoing (Francois CHAUMETTE). 6.1. Introduction. 6.2. Modeling visual features. 6.3. Task function and control scheme. 6.4. Other exteroceptive sensors. 6.5. Conclusion. 6.6. Bibliography. Chapter 7. Modeling and Control of Flexible Robots (Frederic BOYER, Wisama KHALIL, Mouhacine BENOSMAN and George LEVEY). 7.1. Introduction. 7.2. Modeling of flexible robots. 7.3. Control of flexible robot manipulators. 7.4. Conclusion. 7.5. Bibliography. List of Authors. Index.

Three-dimensional heart motion estimation using endoscopic monocular vision system: From artificial landmarks to texture analysis

In robot-assisted beating heart surgery, motion of the heart surface might be virtually stabilized to let the surgeon work as in on-pump cardiac surgery. Virtual stabilization means to compensate physically the relative motion between the instrument tool tip and the region of interest on the heart surface, and to offer surgeon a stable visual display of the scene. To this end, motion of the heart must be estimated. This article focusses on motion estimation of the heart surface. Two approaches are considered in the paper. The first one is based on landmark tracking allowing 3D pose estimation. The second is based on texture tracking. Classical computer vision methods, as well as a new texture-based tracking scheme has been applied to track the heart motion, and, when possible, reconstruct 3D distance to the heart surface. Experimental results obtained on in vivo images show the estimated motion of heart surface points.

Computer-assisted and robot-assisted technologies to improve bone-cutting accuracy when integrated with a freehand process using an oscillating saw

BACKGROUND In orthopaedic surgery, many interventions involve freehand bone cutting with an oscillating saw. Such freehand procedures can produce large cutting errors due to the complex hand-controlled positioning of the surgical tool. This study was performed to investigate the potential improvements in cutting accuracy when computer-assisted and robot-assisted technologies are applied to a freehand bone-cutting process when no jigs are available. METHODS We designed an experiment based on a geometrical model of the cutting process with use of a simulated bone of rectangular geometry. The target planes were defined by three variables: a cut height (t) and two orientation angles (beta and gamma). A series of 156 cuts were performed by six operators employing three technologically different procedures: freehand, navigated freehand, and robot-assisted cutting. After cutting, we measured the error in the height t, the absolute error in the angles beta and gamma, the flatness, and the location of the cut plane with respect to the target plane. RESULTS The location of the cut plane averaged 2.8 mm after use of the navigated freehand process compared with 5.2 mm after use of the freehand process (p < 0.0001). Further improvements were obtained with use of the robot-assisted process, which provided an average location of 1.7 mm (p < 0.0001). CONCLUSIONS Significant improvements in cutting accuracy can be achieved when a navigation system or an industrial robot is integrated into a freehand bone-cutting process when no jigs are available. The procedure for navigated hand-controlled positioning of the oscillating saw appears to be easy to learn and use.

Design and preliminary in vivo validation of a robotic laparoscope holder for minimally invasive surgery.

Manual manipulation of the camera is a major source of difficulties encountered by surgeons while performing minimally invasive laparoscopic surgery.