Kostas Vlachos

Design and implementation of a haptic device for training in urological operations

Virtual reality is becoming very important for training medical surgeons in various operations. Interfacing users with a virtual training environment requires the existence of a properly designed haptic device. This paper presents the design and implementation of a new force feedback haptic mechanism with five active degrees of freedom (DOFs), which is used as part of a training simulator for urological operations. The mechanism consists of a 2-DOF, 5-bar linkage, and a 3-DOF spherical joint, designed to present low friction, inertia and mass, and to be statically balanced. The device is suitable for the accurate application of small forces and moments. All five actuators of the haptic device are base-mounted dc motors and use a force transmission system based on capstan drives, pulleys, and tendons. The paper describes the overall design and sizing considerations, the resulting kinematics and dynamics, the force feedback control algorithm, and the hardware employed. Experimental results are provided.

Transparency maximization methodology for haptic devices

In this paper, a design methodology is presented aimed at maximizing haptic device transparency, as seen from the user side. The methodology developed focuses on endpoint side fidelity, and optimizes not only mechanism dimensions, but also all relevant design parameters including relative position of endpoint desired path to device location, motor transmission ratios, and rotor inertias or motor sizes. The methodology is applied to a 5-degree-of-freedom (5-DOF) haptic device, part of a training medical urological simulator, and is applicable to any haptic mechanism. The transparency maximization is achieved using a multivariable optimization approach and an objective function including mechanism-induced parasitic torques/forces and motor and transmission parameters, as seen from the user side, under several constraints. The objective function and the kinematical and operational constraints are described and discussed. A new 5-DOF haptic mechanism is constructed according to the developed procedure, resulting in a substantially improved device with respect to an existing one, developed with a standard optimization method.

Design of a 5-dof haptic simulator for urological operations

A haptic feedback mechanism with five active degrees of freedom (dof), part of a training simulator for urological operations, is presented. The mechanism consists of a 2-dof 5-bar linkage, and a 3-dof spherical joint. To reproduce very small forces and moments, the mechanism has low friction, inertia and mass, is statically balanced, and has a simple mass matrix. Roll-pitch-yaw motions of the tool result in motions of the corresponding actuator. Force feedback transmission is achieved via capstan drives and idler pulleys. The computation of the currents and the structure of the control loop are described.

Analysis and Motion Control of a Centrifugal-Force Microrobotic Platform

This paper presents the analysis, design, and closed-loop motion control of a mobile microrobotic platform capable of micrometer positioning on a plane. The mobile microrobot, including chassis, actuators, drives, microprocessor, and electronics, is of low cost (less than

A haptic tele-manipulation environment for a vibration-driven micromechatronic device

20), can be fabricated rapidly and is made of commercially available components. Its motion is induced by centrifugal forces generated by two vibration motors installed inside the platform body. The asynchronous operation of the vibration motors is shown by simulation to result in planar motions of two degrees-of-freedom locally, with micrometer resolution. A motion controller has been designed to generate controlled motions using sets of motor angular velocities. A prototype has been developed and used to validate the motion principle and the controller efficacy. Open loop experiments show that the platform motion resolution is approximately 20 μm, while its speed is greater than 2 mm/s. Closed-loop experiments demonstrate a 5 μm resolution, i.e., a fourfold improvement compared to the open loop experiments. The low cost, the rapid fabrication, and the micrometer motion resolution suggest that this microrobotic platform is a promising solution for low-cost microfactories, where a group of such robots performs high throughput, advanced microassembly of microsystems.

Analysis and Experiments of a Haptic Telemanipulation Environment for a Microrobot Driven by Centripetal Forces

In this paper, a novel haptic tele-manipulation environment is presented. This includes an interface between a master haptic mechanism and a slave mechatronic mechanism for biomedical operations. The novelty stems from the fact that the environments slave is a micromechatronic device driven by two inexpensive centripetal force vibration micromotors. The unique characteristics and challenges that arise during the haptic micromanipulation of the specific device are described and analyzed. The developed solutions are presented and discussed. The environment employs three input modes and two force control phases, which are described in detail. The haptic tele-manipulation environment is illustrated by several examples. These show that, while the interaction between the haptic mechanism and the vibration driven device is complicated, the micromanipulation of the device can be successful and appear to the operator as simple.

Mass/inertia and joint friction minimization for a low-force five-dof haptic device

This paper presents the analytical and experimental results on a new haptic telemanipulation environment for microrobot control. The proposed environment is comprised of a 5DOF force feedback mechanism, acting as the master, and a 2DOF microrobot, acting as the slave. The fact that the slave microrobot is driven by two centripetal force vibration micromotors makes the presented telemanipulation environment exceptional and challenging. The unique characteristics and challenges that arise during the haptic micromanipulation of the specific device are described and analyzed. The developed solutions are presented and discussed. Several experiments show that, regardless of the disparity between the master and slave, the proposed environment facilitates functional and simple microrobot control during micromanipulation operations. DOI: 10.1115/1.2988385

A real-time graphic environment for a urological operation training simulator

This work presents a design methodology, which aims at the minimization of the mass, inertia and joint friction for a low - force five - dof haptic device. The haptic device is optimized along a typical path with proper tolerances, rather than at some workspace operating point. The device, part of a training medical simulator for urological operations, consists of a two dof, 5-bar linkage and a three dof spherical joint. The requirement for reliable reproduction of low torques and forces lead to the need for minimization of device induced parasitic forces and torques. The multiobjective optimization employed is based on two objective functions that include mass/ inertia properties and joint friction. The kinematical and operational constraints are taken into account. The resulting optimized mechanism is substantially improved with respect to an existing device.

ON THE DESIGN OF A LOW - FORCE 5 - DOF FORCE - FEEDBACK HAPTIC MECHANISM

An OpenGL/C++ real-time graphic environment, part of a training simulator for urological operations, is presented. The graphic environment simulates endoscope insertion in a small diameter deformable tube and is used with a low-force 5-dof force-feedback haptic mechanism. Piecewise Bezier interpolations are used for smooth urethra deformations. A novel particle-based model computes the forces and torques fed to the haptics. Realistic textures from medical databases are employed and a 25 fps refresh rate is achieved using the Rendering Thread method. The overall simulator software is made of three processes running on two distinct platforms, communicating via Ethernet and TCP/IP.

Backstepping control with energy reduction for an over-actuated marine platform

Virtual reality is becoming very important for training medical surgeons in various operations. Interfacing users with a virtual training environment, requires the existence of a properly designed haptic device. This paper presents the design of a new force feedback haptic mechanism with five active degrees of freedom (dof), which is used as part of a training simulator for urological operations. The mechanism consists of a two dof, 5Ðbar linkage and a three dof spherical joint, designed to present low friction, inertia and mass, to be statically balanced, and have a simple mass matrix. The device is suitable for the accurate application of small forces and moments. All five actuators of the haptic device are basemounted DC motors and use a force transmission system based on capstan drives, pulleys and miniropes. The paper describes the chosen design, and its kinematics, dynamics, and control algorithm and hardware employed.