Sebastian Matich

A new single-port robotic system based on a parallel kinematic structure

In this paper we present a new single port robotic system particularly designed for single port access surgery in the field of colon cancer. In contrast to most state of the art systems the two intracorporeal manipulator arms are set up using a parallel kinematic structure with 5DOF, which are integrated into a shaft of 38mm in diameter. The parallel kinematic structure and its workspace are discussed in detail. As a unique feature, the kinematics uses the translation and rotation of three rods per manipulation arm. Using a parallel kinematic approach enables dynamic, stiff and precise movements which are needed to generate a realistic haptic feedback. The results of several performed circle tests are presented showing the ability of performing precise and dynamic movements with speeds of up to 327 mm/s and under load condition of 4 N.

Pseudo-Haptic Feedback in Teleoperation

In this paper, we develop possible realizations of pseudo-haptic feedback in teleoperation systems based on existing works for pseudo-haptic feedback in virtual reality and the intended applications. We derive four potential factors affecting the performance of haptic feedback (calculation operator, maximum displacement, offset force, and scaling factor), which are analyzed in three compliance identification experiments. First, we analyze the principle usability of pseudo-haptic feedback by comparing information transfer measures for teleoperation and direct interaction. Pseudo-haptic interaction yields well above-chance performance, while direct interaction performs almost perfectly. In order to optimize pseudo-haptic feedback, in the second study we perform a full-factorial experimental design with 36 subjects performing 6,480 trials with 36 different treatments. Information transfer ranges from 0.68 bit to 1.72 bit in a task with a theoretical maximum of 2.6 bit, with a predominant effect of the calculation operator and a minor effect of the maximum displacement. In a third study, short- and long-term learning effects are analyzed. Learning effects regarding the performance of pseudo-haptic feedback cannot be observed for single-day experiments. Tests over 10 days show a maximum increase in information transfer of 0.8 bit. The results show the feasibility of pseudo-haptic feedback for teleoperation and can be used as design basis for task-specific systems.

Investigation of the usability of pseudo-haptic feedback in teleoperation

Pseudo haptic sensation is an illusion based on visual stimuli. In virtual environments the principle of pseudo haptic feedback is used to simulate material properties such as stiffness, mass and friction. Transfering the principle of pseudo haptic feedback to real haptic teleoperation systems can provide a haptic sensation for properties of material, manipulated without active haptic feedback. Hence, the implementation of pseudo haptic feedback to teleoperation systems reduces the requirements for kinematic structures and actuators of the used haptic user interface .In this work, we discuss the usability of pseudo haptic feedback for its application in teleoperation systems. The mechanisms of pseudo-haptic feedback are theoretically explained for an exemplary teleoperation task. Options to vary the intensity of the users pseudo haptic sensation are derived. The effect of pseudo haptic feedback for teleoperation is based on changing the input-output ratio by actual measured interaction forces at the end-effector. A one degree of freedom teleoperation system is used for first experiments with pseudo haptic feedback in teleoperation. The used teleoperation system couples users input force to a defined displacement of an end-effector. Our results prove the validity of pseudo-haptic feedback in teleoperation by a compliance discrimination experiment.

3-D force measurement using single axis force sensors in a new single port parallel kinematics surgical manipulator

Single port surgery is an innovative approach in the field of minimally invasive surgery. Although several telemanipulators exist to perform operations through only a single incision they all suffer from the lack of haptic feedback. To generate kinesthetic feedback the intracorporeal forces need to be measured, which is a challenging task. To overcome these limitations we investigate in this paper the force sensing capability of a new single port robot that has two parallelkinematic manipulators. Because of the rigidity and excellent controllability the tip force is measured using proximally arranged force sensors. To minimize friction effects a longitudinal vibration of 6 Hz with an amplitude of 20 μm is applied to the manipulator while the tip force is varied in the three main coordinate axes. Within the analysis 32320 values are investigated showing that a vibration has a significant impact and dramatically improves the signal quality by minimizing the crosstalk by a factor of up to 12.7 enabling to measure the tip force exactly.

A New 4 DOF Parallel Kinematic Structure for use in a Single Port Robotic Instrument with Haptic Feedback.

This paper presents a parallel kinematic structure for use in a Single Port Robotics system. To derive good haptic feedback, design is accomplished considering haptic aspects like stiffness and dynamic positioning, thus a parallel kinematic setup is chosen. By appling a kinematic diagram a parallel kinematic structure is identified that enables a spatial movement of an intracorporal end effector with 4 degrees of freedom (DOF). The central design variables are identified and specified. A first technical design for the manipulator is presented.

NEW DEVICE FOR ERGONOMIC CONTROL OF A SURGICAL ROBOT WITH 4 DOF INCLUDING HAPTIC FEEDBACK

Loss of haptic feedback is one major drawback of robotic systems. Motivated by this fact this paper presents a new user interface with haptic feedback for controlling a surgical robot with 4 degrees of freedom (DOF) and haptic grasping. Therefore, a kinematic structure with confined workspace matching the robot’s workspace is chosen; thus, the user interface can be handled like a forceps with thee point precision grip.

A teleoperated platform for transanal single-port surgery: Ergonomics and workspace aspects

We present a new teleoperation setup for minimally invasive single-port surgery through natural orifices. The system consists of an intra-corporal parallel slave robot with two instrument arms and a corresponding master interface with four degrees of freedom and grasping. The master interface mimicks the slave robot kinematics to prevent non-achievable movements. With a workspace of ⊘ 60 mm × 85 mm, interaction forces of up to 5 N and mean speeds of up to 327 mm/s the robot is designed to perform a rectum resection intervention, an operation hardly possible with conventional laparoscopic instruments. In this work, we address several ergonomic aspects of the setup, including surgeons pose, movement scaling, visual feedback, and haptic feedback. Two experiments were performed to investigate the accuracy and dexterity of the robotic system compared to conventional single-port systems. We found a significant decrease of errors in a point-and-touch-task when using the robot, but no effect on the duration of the task. Surgeons were able to perform suturing and knotting tasks as well as a gall bladder extraction in a porcine model with the robot in an hands on experiment. These experiments showed a good intuitivity and a high instrument control precision as described by the participants.

Miniaturized multiaxial force/torque sensor with a rollable hexapod structure

Abstract Miniaturized force/torque sensors are relevant components for robotic interaction with humans and unknown environments. This paper presents a disruptive manufacturing process for multiaxial force/torque sensors based on a Stewart-Gough platform. The deformation element consists of a hexapod geometry with six sensing elements with a total diameter of 9 mm. The sensor manufacturing process is divided into three steps: 1. Milling a planar arrangement of sensing elements out of a 2 mm steel (1 .4301) plate, 2. applying twelve strain gauges in half-bridge configuration and 3. rolling the elements into a hexapod structure. The dimensions of the sensing elements are scalable to adjust the size and nominal measurement range of the sensor. The first prototype has a measuring range of 4 N and 66 mNm. The characterization of the sensor shows a maximal linearity and hysteresis error of 1.16% and a cross-sensitivity smaller than 2.76% . Zusammenfassung Miniaturisierte Kraft-Momenten-Sensoren sind notwendige Komponenten für die Interaktion von Robotern mit Menschen und unbekannten Umgehungen. In dieser Arbeit wird ein neuartiger Ansatz zur Fertigung solcher Sensoren auf Basis einer Stewart-GoughPlattform präsentiert. Der so gefertigte Sensor basiert auf einem sechseckigen Verformungskörper mit einem Durchmesser von 9 mm. Der Fabrikationsprozess besteht aus drei Schritten: 1. Fräsen einer planaren Struktur mit aus einer Stahlplatte mit einer Dicke von 2 mm, 2. Applikation von zwölf Metallfolien-DMS in einer Halbbrücken-Konfiguration und 3. Aufrollen des Verformungskörpers. Die Größe des Verformungskörpers kann dabei einfach an verschiedene Messbereiche angepasst werden. Der erste so gefertigte Prototyp weist einen Messbereich von 4N bzw. 66 mNm auf. Der Linearitäts- und Hysteresefehler beträgt 1,16%, das Übersprechen maximal 2,76%.

Pseudo-Haptic Feedback in Medical Teleoperation

Abstract Pseudo-haptic feedback is a haptic illusion based on a mismatch of haptic and visual perception. It is well known from applications in virtual environments. In this work, we discuss the usabiliy of the principle of pseudo-haptic feedback for teleoperation. Using pseudo-haptic feedback can ease the design of haptic medical tele-operation systems. Thereby a user’s grasping force at an isometric user interface is used to control the closing angle of an end effector of a surgical robot. To provide a realistic haptic feedback, the coupling characteristic of grasping force and end effector closing angle is changed depending on acting end effector interaction forces. With an experiment, we show the usability of pseudo-haptic feedback for discriminating compliances, comparable to the mechanical characteristic of muscles relaxed and contracted. The provided results base upon the data of 10 subjects, and 300 trails.

User-interface for teleoperation with mixed-signal haptic feedback

Haptic feedback for minimally invasive surgery is a widely debated topic, especially force sensors for this kind of application are thoroughly researched. The current state-of-the-art includes several realization options, but none of them are suitable to be integrated in small diameter instruments. In this work, we present a new approach for the generation of haptic feedback by using two separate feedback mechanisms for spatial kinesthetic and unidirectional tactile feedback in a teleoperation system with a parallel kinematic slave robot and the design of the corresponding user interfaces. Kinesthetic forces are measured with proximal sensors in the robot kinematic and displayed with a delta-type kinematic mechanism. Tactile signals are acquired with an acceleration sensor placed closely at the tip of the robot manipulator and conveyed open-loop by a vibrating cylinder to the users palm. Kinesthetic forces up to 15 N can be displayed up to a frequency of 50 Hz. The tactile interface displays accelerations up to 15m/s for frequencies from 50 Hz to 1000 Hz. The combination of the two interfaces allows the display of high-fidelity haptic feedback with greatly reduced requirements on the interface components.