Andreas Tobergte

DLR MiroSurge: a versatile system for research in endoscopic telesurgery.

PurposeResearch on surgical robotics demands systems for evaluating scientific approaches. Such systems can be divided into dedicated and versatile systems. Dedicated systems are designed for a single surgical task or technique, whereas versatile systems are designed to be expandable and useful in multiple surgical applications. Versatile systems are often based on industrial robots, though, and because of this, are hardly suitable for close contact with humans.MethodTo achieve a high degree of versatility the Miro robotic surgery platform (MRSP) consists of versatile components, dedicated front–ends towards surgery and configurable interfaces for the surgeon.ResultsThis paper presents MiroSurge, a configuration of the MRSP that allows for bimanual endoscopic telesurgery with force feedback.ConclusionsWhile the components of the MiroSurge system are shown to fulfil the rigid design requirements for robotic telesurgery with force feedback, the system remains versatile, which is supposed to be a key issue for the further development and optimisation.

Telemanipulator for remote minimally invasive surgery

The requirements for an ideal telemanipulator (i.e., robot and surgical instrument) are derived. An overview on telemanipulators reported in literature is given. The new robot for telepresence surgery developed by German Aerospace Center (DLR) is presented in detail in the DLR Robot section. Surgical instruments equipped with miniaturized force-torque sensors and additional DoF at the distal end, also developed by DLR, are described in the DLR Instruments section. The last section concludes this article and gives directions for further research.

The sigma.7 haptic interface for MiroSurge: A new bi-manual surgical console

This paper presents the design and control of the sigma.7 haptic device and the new surgical console of the MiroSurge robotic system. The console and the haptic devices are designed with respect to requirements in minimally invasive robotic surgery. Dedicated left and right handed devices are integrated in an operator console in an ergonomic configuration. The height of the whole console is adjustable, allowing the surgeon seated and standed operation. Each of the devices is fully actuated in seven degrees of freedom (DoF). A parallel mechanism with 3 DoF actuates the translational motion and an attached wrist with 3 intersecting axis drives the rotations of the grasping unit. This advantageous design leads to inherently decoupled kinematics and dynamics. Cartesian forces are 20 N within the translational workspace, which is a sphere of about 120 mm diameter for each device. The rotational wrist of the device covers the whole workspace of the human hand and provides maximum torques of about 0.4 Nm. The grasping unit can display forces up to 8 N. An integrated force/torque sensor is used to increase the transparency of the devices by reducing inertia and friction. It is theoretically shown that the non-linear closed loop system behaves like a passive system and experimental results validate the approach. The sigma.7 haptic devices are designed by Force Dimension in cooperation with the German Aerospace Center (DLR). DLR designed the surgical console and integrated the haptic devices in the MiroSurge system.

The DLR MiroSurge - A robotic system for surgery

This video presents the in-house developed DLR MiroSurge robotic system for surgery. As shown, the system is suitable for both minimally invasive and open surgery. Essential part of the system is the MIRO robot: The soft robotics feature enables intuitive interaction with the robot.

Planning and control of a teleoperation system for research in minimally invasive robotic surgery

This paper introduces the planning and control software of a teleoperation system for research in minimally invasive robotic surgery. It addresses the problem of how to organize a complex system with 41 degrees of freedom as a flexible configurable platform. Robot setup planning, force feedback control and nullspace handling with three robotic arms are considered. The planning software is separated into sequentially executed planning and registration procedures. An optimal setup is first planned in virtual reality and then adapted to variations in the operating room. The real time control system is structured in hierarchical layers. Functions are arranged in the layers with respect to their domain and maximum response time. The design is flexible and expandable while performance is maintained. Structure, functionality and implementation of planning and control are described. The prototypic robotic system provides intuitive bimanual bilateral teleoperation within the planned working space.

Robust multi sensor pose estimation for medical applications

In this paper a sensor fusion for pose estimation using optical and inertial data is presented. The proposed algorithm is based on extended Kalman filtering and fuses data from an optical tracking system and an inertial measurement unit. These two redundant sensor systems complement each other well, with the tracking system providing absolute positions and the inertial measurements giving low latency information of derivatives. Models for both sensors are given respecting the different sampling times and latencies. Another key issue is to use information about every landmark, i.e. marker ball, visible for the tracking system, by coupling the two sensor systems tightly together. The algorithm is evaluated in simulation and tested with an experimental hardware platform. The combined sensor system is robust with respect to short time marker occlusions and effectively compensates for latencies in the pose measurements.

Direct force reflecting teleoperation with a flexible joint robot

This paper presents a high fidelity force feedback teleoperation control for surgical applications. Advanced control methods, such as flexible joint tracking control and passivity observation, are introduced in the direct force reflecting control architecture. A full state feedback controller of the flexible joint slave robot controls the motor position, velocity, the joint torque, and the torque derivative. The pose of the haptic device and the first three derivatives are observed to generate reference states for the robot control using the robots inverse dynamics model. Interaction forces of the slave and the environment are measured with a force/torque sensor and directly sent back to the master device. Stability is guaranteed with a passivity observer that monitors the energy in the teleoperation system online and disconnects master and slave if the system operates beyond its stable region. The proposed control architecture is implemented with the sigma.7 haptic device and the MIRO robot. It is experimentally shown, that appropriately considering elasticities with full state reference and control of the slave, increases the dynamic range of the system enabling transparent and stable interaction with hard and soft environments.

Mirosurge----advanced user interaction modalities in minimally invasive robotic surgery

This paper presents MiroSurge, a telepresence system for minimally invasive surgery developed at the German Aerospace Center (DLR), and introduces MiroSurges new user interaction modalities: (1) haptic feedback with software-based preservation of the fulcrum point, (2) an ultrasound-based approach to the quasi-tactile detection of pulsating vessels, and (3) a contact-free interface between surgeon and telesurgery system, where stereo vision is augmented with force vectors at the tool tip. All interaction modalities aim to increase the users perception beyond stereo imaging by either augmenting the images or by using haptic interfaces. MiroSurge currently provides surgeons with two different interfaces. The first option, bimanual haptic interaction with force and partial tactile feedback, allows for direct perception of the remote environment. Alternatively, users can choose to control the surgical instruments by optically tracked forceps held in their hands. Force feedback is then provided in augmented stereo images by constantly updated force vectors displayed at the centers of the teleoperated instruments, regardless of the instruments position within the video image. To determine the centerpoints of the instruments, artificial markers are attached and optically tracked. A new approach to detecting pulsating vessels beneath covering tissue with an omnidirectional ultrasound Doppler sensor is presented. The measurement results are computed and can be provided acoustically (by displaying the typical Doppler sound), optically (by augmenting the endoscopic video stream), or kinesthetically (by a gentle twitching of the haptic input devices). The control structure preserves the fulcrum point in minimally invasive surgery and user commands are followed by the surgical instrument. Haptic feedback allows the user to distinguish between interaction with soft and hard environments. The paper includes technical evaluations of the features presented, as well as an overview of the system integration of MiroSurge.

A peer-to-peer trilateral passivity control for delayed collaborative teleoperation

In this paper a trilateral Multi-Master-Single-Slave-System with control authority allocation between two human operators is proposed. The authority coefficient permits to slide the dominant role between the operators. They can simultaneously execute a task in a collaborative way or a trainee might haptically only observe the task, while an expert is in full control. The master devices are connected with each other and the slave robot peer to peer without a central processing unit in a equitable way. The system design is general in that it allows delayed communication and different coupling causalities between masters and slave, which can be located far from each other. The Time Domain Passivity Control Approach guarantees passivity of the network in the presence of communication delays. The methods presented are sustained with simulations and experiments using different authority coefficients.

Towards accurate motion compensation in surgical robotics

This paper proposes a method for accurate robotic motion compensation of a freely moving target object. This approaches a typical problem in medical scenarios, where a robotic system needs to compensate physiological movements of a target region related to the patient. An optical tracking system measures the poses of the robots end-effector and the moving target. The task is to track the target with the robot in a desired relative pose. Arbitrary motion in 6 DoF is covered. The position controller of the medical light-weight robot MIRO is enhanced by a Cartesian displacement observer. The proposed observer feedback preserves the dynamics of the robot, while achieving high accuracy in task space. The target object is equipped with an inertial measurement unit in addition to tracking markers. Target sensor data is fused by an extended Kalman filter in a tightly coupled approach. The robot control and the target tracking in the task space aim to combine accuracy, dynamic performance and robustness to marker occlusions. The algorithms are verified with the DLR MIRO, an experimental target platform, and a commercial tracking system. The experiments demonstrate rapid convergence to desired Cartesian poses and good dynamic tracking performance even at higher target motion speed.