Árpád Takács

Review of tool-tissue interaction models for robotic surgery applications

Besides the motion control issues and problems arising in general robotic applications, control engineers frequently encounter difficulties in designing robotic surgery systems due to the complex environmental constraints present. One of the most challenging problems is caused by the unique behavior of soft tissues under manipulations such as grabbing, cutting and indentation. The appropriate modeling of the interaction between the tools held by the robotic arm and tissues is essential for precise control, yet no generally applicable, universal model has been developed so far. This paper gives an overview of the existing tool-tissue interaction models and possible approaches to the parameterization problem, listing and reviewing several models found in the literature. We reviewed the problem within the frames of a theoretical master-slave teleoperation surgical robot, where exact mathematical model of the soft tissue is essential for effective control over a time-delayed communication channel.

Nonlinear Soft Tissue Models and Force Control for Medical Cyber-Physical Systems

Robotic telesurgery application could greatly benefit from force control, providing safe and stable application even under time delays and other disturbing conditions. This paper describes a soft tissue model which can be integrated into the control loop of a teleoperational master -- slave robot. Three alternations of the Wiechert model have been implemented and matched against experimental data. A nonlinear model has been proposed to realistically model the properties of liver-type tissues. Based on the model, adequate force control can be designed in the future.

Teacher's Kit: Development, Usability, and Communities of Modular Robotic Kits for Classroom Education

Robotics is becoming a mainstream phenomenon, entering all areas of our lives. In addition to cutting-edge research and development, robotics is becoming equally important in the classroom and home education. Numerous educational kits have appeared on the market recently, ranging from simple toolboxes and toys to complex, configurable R&D sets. Their value in formal teaching lies in modularity and the applicability of the associated curriculum. Some kits have already attracted major crowds of users, forming strong communities. The aim of this article is to review the currently available educational robotics kits along with their possible usability in formal education, focusing the analysis on system capabilities, modularity, and teaching materials available. The summary of these teaching aids should ease the decisions of robotics experts and instructors when choosing their tools for teaching and demonstration.

Nonlinear soft tissue mechanics based on polytopic Tensor Product modeling

Achieving reliable force control is one of the main design goals of robotic teleoperation. It is essential to grant safe and stable performance of these systems, regarding HMI control, even under major disturbing conditions such as time delay or model parameter uncertainties. This paper discusses the systematic derivation of polytopic qLPV model from the nonlinear dynamics of typical soft tissues of the human body based on recent experimental results. The derivation is based on the Tensor Product (TP) Model Transformation. The presented method is a crucial step in laying the foundations of adequate force control in telesurgery. The proposed approach could form the basis of LMI-based controller design.

Surgical robotics — Born in space

With the introduction of telerobotic systems, it has become possible for surgeons to perform medical operations at greater physical distances from their patients. Whether in an adjacent room or on another continent, these systems enable greater flexibility in mitigating adverse surgical conditions. These ideas originally came from the space research, where further needs emerged to advance robots that could resolve surgical cases previously not treatable. The concept of providing surgical aid to astronauts in outer space yielded to telerobotic surgical care on Earth, benefiting around 1 million patients per year. As the field continues to develop and becomes more prevalent, it is worth looking back to the origins of the technology and the early days of robotic telesurgery. While many of the early prototypes and technologies never reached patients, their engineering components and innovative concepts directly lead to the birth of modern surgical robots.

Novel Design of a Model Reference Adaptive Controller for Soft Tissue Operations

Model Reference Adaptive Controllers (MRAC) have dual functionality: besides guaranteeing precise trajectory tracking of the controlled system, they have to provide an “external control loop” with the illusion that it controls a physical system of prescribed dynamic properties, i.e., the “reference system”. The MRACs are designed traditionally by Lyapunovs 2nd method that is mathematically complicated, requiring strong skills from the designer. Adaptive controllers alternatively designed by the use of Robust Fixed Point Transformations (RFPT) operate according to Banachs Fixed Point Theorem, and are normally simple iterative constructions that also have a standard variant for MRAC design. This controller assumes a single actuator that is driven adaptively. Master-Slave Systems form a distinct class of practical applications, in which two arms-the master and the slave-operate simultaneously. The movement of the master must be tracked precisely by the slave in spite of the quite different forces exerted by them. In the present paper, a soft tissue-cutting operation by a master-slave structure is simulated. The master arm has a simple torque-reference friction model, and is driven by the surgeon. The obtained master arm trajectory has to be precisely tracked by the electric DC motor driven slave system, which is in dynamic interaction with the actual tissue under operation. It is shown via simulations that the RFPT-based design can efficiently solve such tasks without considerable mathematical complexity.

A novel methodology for usability assesment of rheological soft tissue models

The task to distinguish between soft tissues by testing their mechanical properties is often referred to as the primary cognitive role of haptic devices. It is a common view that todays surgical simulators that are using haptic interfaces should rely on simple mechanical models of soft tissues, instead of complex, parameterized finite element models, thus enhancing real-time operation and focusing on the most representative mechanical effects. This paper proposes a user-trial validation method for tissue models and their polytopic representation by creating an experimental framework for soft tissue characterization, using the da Vinci Research Kit. The characterization methdodology relies on haptic feedback from the manipulated real tissue, extending the functionality of surgical simulators using virtual tissue models created by the previously proposed soft tissue modeling method. Results showed that the tissue model represents the tissue behavior sufficiently well for use in haptic simulators, based on user experience. Furthermore, it was concluded that silicon phantoms can mimic the behavior of real tissues in various surgical scenarios, especially when using teleoperation manipulation.

Polytopic model based interaction control for soft tissue manipulation

Reliable force control is one of the key components of modern robotic teleoperation. The performance of these systems, in terms of safety and stability, largely depends on the controller design, as it is desired to deal with various disturbing conditions, such as uncertainties of the model parameters or latency-induced problems. This work presents a polytopic quasi-linear parameter-varying (qLPV) model derived from a previously verified nonlinear soft tissue model, along with a model-based force control scheme that involves a tensor product polytopic state feedback controller. The derivation is based on the Tensor Product (TP) Model Transformation. The proposed force control scheme is verified and evaluated through numerical simulations.

Reaction force and surface deformation estimation based on heuristic tissue models

Advanced surgical robotic systems aim to offer improved capabilities through automated low-level functions. In the applications, soft tissue mechanics and tool-tissue interaction modeling play an important role in achieving optimal control, relying on model-based control methods. This approach allows for addressing crucial issues during teleoperation, such as time-delay, state observation or stability. This paper presents a novel approach for modeling the behavior of soft tissue during surgical interventions, relying on the widely-employed concept of rheological models. The nonlinear Wiecher model is used for reaction force estimation during tissue indentation, tested on beef liver samples for acquiring mechanical parameters from experimental data. Curve fitting methods were used in both stress relaxation and constant indentation speed compression phases. Reaction forces are estimated using the proposed model, followed by verification tests on ex-vivo beef liver samples. The results of this research showed that the proposed novel rheological soft tissue model is capable of estimating the reaction forces acting on the tool, if the shape of the deformed tissue is known in time. This model can be successfully integrated into closed-loop surgical robot controllers.

Joint Platforms and Community Efforts in Surgical Robotics Research

Abstract In modern medical research and development, the variety of research tools has extended in the previous years. Exploiting the benefits of shared hardware platforms and software frameworks is crucial to keep up with the technological development rate. Sharing knowledge in terms of algorithms, applications and instruments allows researchers to help each other’s work effectively. Community workshops and publications provide a throughout overview of system design, capabilities, know-how sharing and limitations. This paper provides sneak peek into the emerging collaborative platforms, focusing on available open-source research kits, software frameworks, cloud applications, teleoperation training environments and shared domain ontologies.