Nicolas Garcia

Kinematics of a robotic 3UPS1S spherical wrist designed for laparoscopic applications

Current robotic orientation surgical devices used to be large, in order to cover the needed workspace and to be rigid enough to resist the forces that occur during surgery. The disadvantages of the large size of the devices are the ergonomics, collisions and interference with the surgeons. This paper presents the first steps that have been carried out on the development of a small spherical wrist for laparoscopic applications.

Visual Control of Robots with Delayed Images

This research develops a control scheme for visual servoing that explicitly takes into account the delay introduced by image acquisition and processing. For this purpose, a predictor block, i.e., an estimator that predicts several samples ahead of time, is properly included in the scheme. The proposed approach is analytically analyzed in terms of dynamics and steady-state errors, and compared to previous approaches. Furthermore, several simulations are comparatively shown in order to illustrate the benefits and limitations of the proposed control scheme. Finally, some experimental results using a turntable and a 3-d.o.f. Cartesian robot are provided in order to validate the analytical and simulation results.

Performance evaluation of spherical parallel platforms for humanoid robots

This paper presents a simple methodology for the quantitative and qualitative analysis of the performance of spherical parallel platforms. The quaternion formulation is used to represent the possible rotations, showing the workspace as a three-dimensional (3-D) solid object. The singularities of the platform intersect graphically with its workspace, allowing a graphical study of the mechanism kinematics. The performance criterion considered here has been the local dexterity of the manipulator. This methodology has been used to study and analyze three known orientation parallel platforms: 3- R RR, 3-U P U-wrist, and 2-U P S-1- R U. The objective of this study is to analyze the ability of these platforms to be utilized as mechanisms for the neck and shoulders of humanoid robots. Finally, the forces on actuators in some typical motions for neck and shoulder are plotted.

Haptic simulator for training of Total Knee Replacement

This paper presents a novel orthopaedic surgery simulator, capable of analyzing, processing and displaying medical images. These newly added capabilities allows the reconstruction of multiple three-dimensional models, and their integration into a virtual environment. The main contribution of this work is the developement of a new mixed graphical model (surface and volumetric) that allows simulation of bone machining in real time.

Bilateral Control of Teleoperation Systems Through State Convergence

This chapter describes a new bilateral control method of teleoperation systems. This method is based on the state space formulation and it can be applied to any teleoperation system where the master and the slave would be represented by nth-order linear differential equations. The control system allows that the slave manipulator follows the master. The tracking is achieved by state convergence between the master and the slave. The method is able also to establish the desired dynamics of this convergence and the dynamics of the slave manipulator. Furthermore a simple design procedure is provided to obtain the control system gains. The advantage of this design procedure is that it is only necessary to solve a set of equations to calculate the control system gains. The control by state convergence can be also applied to teleoperation systems with communication time delay. In this case, the Taylor expansion is used to approximate the time delay. The state convergence allows that the slave manipulator follows the master in spite of the time delay in the communication channel. Experimental results with a teleoperation system of one DoF are presented to verify the control method.

Control strategies of an assistive robot using a Brain-Machine Interface

In this paper, two control strategies to move a planar robot arm with a non-invasive spontaneous brain-machine interface (BMI) have been compared. The BMI is based on the correlation of EEG maps and allows differentiating between two mental tasks related to motor imagery. Using the BMI, the user is able to control 2D movements of the robot arm in order to reach several goals. The first control strategy is based on a hierarchical control and the second one uses a directional control of the movement. The robot arm used is the PuParm, a force-controlled planar robot designed and developed by the nBio research group at the Miguel Hernández University of Elche (Spain). Three goals have been placed on the experimental setup. After performing the tests, time taken to reach the goals and errors have been presented and compared, showing the advantages and disadvantages of each strategy. The evidence from this study suggests that the control of a planar robot is possible with both strategies. The hierarchical control is slower but more reliable, while the directional control is much faster and more relaxing for the user, but less precise. These findings indicate that future assistive applications like grasping daily objects in a realistic environment could be performed with this system.

Design and analysis of a spherical humanoid neck using screw theory

This paper presents a simple methodology for the quantitative and qualitative analysis of the performance of spherical parallel platforms. The presented method is oriented to get a mimetic relation between the human motions and the spherical mechanism motion. The quaternion formulation is used to represent the possible rotations, showing the workspace as a tridimensional solid object. The graphical intersection of the singularities of the platform with its workspace allow an study of the mechanism kinematics. To explain this method, the kinematics of the human neck is plotted, and the analysis of a suggested 2UPS-1RU (with two legs with Universal, Prismatic, Spherical kinematic chain and one leg with a Rotational-Universal kinematic chain) parallel platform is presented. Finally, some results about the forces on actuators for the resulting design of the spherical platform are shown

Kinematics correspondence & scaling issues in virtual telerobotics systems

This paper describes how to establish a kinematic correspondence between the workspaces of master and slave devices using a virtual environment and its implementation on a teleoperation simulator. The virtual environment incorporates the kinematic and dynamic model of the slave robot and the remote environment. Mapping and scaling of workspaces have been added to the teleoperation simulator in order to give the operator a more natural interface having the possibility of changing his viewpoint of the remote scene. Experimental results are presented to verify the kinematic algorithms implemented

Bilateral Control Architecture for Telerobotics Systems in Unknown Environments

This paper presents a bilateral control architecture for teleoperation systems where the environment must not be identified to design the control gains. In this control scheme, the interaction force of the slave with the environment is an external input. This force is not modeled by gains inside the control architecture. In the paper, the state convergence methodology is used to design the control gains of the teleoperation system. The control system allows that the slave state follows the master state and to establish the desired dynamics of the teleoperation system. Several simulation results are shown to verify the performance of the control scheme.

Experimental bilateral control by state convergence

This paper presents a discrete design and control method of teleoperation systems. The design method is based on the state space formulation and it allows to obtain the control gains for any teleoperation system where the master and the slave manipulators would be represented by nth-order discrete linear transfer functions. The control method allows that the slave follows the master through the state convergence between the master and the slave. The method is able also to establish the desire dynamics of this convergence and the dynamics of the slave manipulator. The advantage of this method is that it can be applied to control a teleoperation system where the master and the slave are modeled by transfer functions of different order. In order to validate the control method, simulation results are shown considering a teleoperation system where the master and the slave are modeled by discrete transfer functions of different order