Soft tissue force control using active observers and viscoelastic interaction model

Current cardiac surgery faces the challenging problem of heart beating motion even with the help of mechanical stabilizer which makes delicate operation on the heart surface difficult. Motion compensation methods for robotic-assisted beating heart surgery have been proposed recently in literature, but research on force control for such kind of surgery has hardly been reported. Moreover, the viscoelasticity property of the interaction between organ tissue and robotic instrument further complicates the force control design which is much easier in other applications by assuming the interaction model to be elastic (industry, stiff object manipulation, etc.). In this work, we present a three-dimensional force control method for robotic-assisted beating heart surgery taking into consideration of the viscoelastic interaction property. Performance studies based on our D2M2 robot and 3D heart beating motion information obtained through Da Vinci™ system are provided.

The ability to control index finger and elbow flexion forces was measured while subjects used either haptic feedback or both haptic and visual feedback to control the forces exerted. Over a 120-s time period subjects were able to control the finger forces ranging from 2 to 6 N to within 1 N using only haptic feedback, and elbow flexion forces to within 4.5 N over a force range of 10-30 N. At the same force amplitude there was no significant difference between the two muscle groups in the precision or accuracy with which the force could be controlled, suggesting that there is not a proximal to distal gradient in force control as has been found for the control of limb movement and position.

The focus of this research is on the perception and control of forces produced by the hand. It is known that the change in force that subjects can reliably discriminate is approximately 6%, and that subjects are able to match forces generated by two corresponding muscle groups with an accuracy of approximately 15%. The present study was concerned with measuring the ability to control finger force using only haptic feedback and both haptic and visual feedback. It was found that subjects were surprising good at controlling forces for up to 120 s using only haptic feedback with mean absolute errors of less than 0.3 N over a force range of 2–6 N. The variation in force averaged 10.5% when haptic feedback was available and decreased to 6% when visual feedback was also provided. These results provide a framework for specifying the characteristics of force-reflecting haptic interfaces that should optimize human perception.

Two different control schemes, position model referenced control (PMRC) and force model referenced control (FMRC), are developed for a simplified two robots model with one interacting axis. The dynamic stability of the position (or force) control under the FMRC (or PMRC) is analyzed. Results indicate that PMRC, although providing better dynamic performance of the position control, may degrade the dynamic performance of the force control. However, FMRC can provide better dynamic performance of both position and force control.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Nowadays, robotic-assisted surgery does not allow beating heart surgery with autonomous motion compensation functionalities. This paper tackles this problem, based on a robotic control architecture that relies on force feedback. The algorithm merges two cascade loops. The inner one is based on the Kalman active observer (AOB), performing model-reference adaptive control to impose a well-defined stable plant. The outer one, based on a model predictive control (MPC) approach, generates control references for beating heart motion compensation. Two robots are used in the experiments. A lightweight 4-DoF surgical robot generates desired surgical forces and a 3-DoF robot equipped with an ex vivo heart at the end-effector reproduces realistic heart motion. Additionally, robustness to cardiac stiffness mismatches is analyzed.

Robotic systems have significantly transformed the landscape of minimally invasive surgery, offering enhanced precision, reduced recovery times, and improved patient outcomes. These systems have evolved from simple mechanical tools to sophisticated platforms integrating advanced control algorithms and real-time feedback mechanisms. This paper provides a comprehensive overview of the role of robotic systems in minimally invasive surgery, exploring the various benefits, inherent risks, and the challenges associated with their adoption and development. We examine the technical aspects of robotic control systems, such as kinematics, force control, and haptic feedback, which enable greater surgical accuracy. Despite these advantages, challenges such as system complexity, high costs, and ethical concerns remain significant barriers to widespread adoption. The future of robotic surgery lies in overcoming these obstacles, with advancements in system miniaturization and further refinement of control systems poised to enhance the efficacy and accessibility of robotic platforms. This paper explores the role of robotic systems in minimally invasive surgery, focusing on three key areas: bronchoscopy and ureteroscopy. By reviewing the benefits, risks, case studies, and future directions of these technologies, the paper seeks to provide an in-depth understanding of how robotic systems are shaping the future of surgery. Key words: Robotic Surgery, Minimally Invasive Surgery, Robotic Control Systems, Surgical Precision, PID Control, Kinematics, Inverse Kinematics, Forward Kinematics, Dynamic Control, Force Control, Impedance Control, Surgical Robotics, Haptic Feedback, Robotic Arm, Robotic Surgery Benefits, Robotic Surgery Risks, Robot-Assisted Surgery, Surgeon Console, Real-Time Feedback, Surgical Training, Robotic System Development, System Testing, Clinical Trials, Surgical Robot Performance, Robotics in Urology, Telepresence Surgery, Robotic Surgery Cost, Robotic Surgery Future Directions.

ABSTRACTA robot interacting with the environment requires that the end effector \\hboxposition is tracked and that the forces of contact are kept below certain reference values. For instance, in a rehabilitation session using a robotic device, the contact forces are limited by the allowed strength of the human limbs and their complex-joints. In these cases, a control scheme which considers both position and force control is essential to avoid damage to either the end effector or the object interacting with the robot. This paper therefore develops a real-time force/position control scheme for a three-DOF parallel robot whose end effector holds a DOF one translation (1 T) and two rotations (2 R). The implemented hybrid force/position control considers, as a reference, the normal force on the mobile platform, which is measured by means of a load cell installed on the platform. The position control is designed to track the orientations of the robot either in joint or task space using a model-based control scheme with identified parameters. Moreover, the force control is based on a PD action. The control scheme is developed through simulations, before being applied to an actual parallel robot. The findings show that with the implemented controller, the actual robot accomplishes the reference values for the normal force on the mobile platform, while at the same time the platform accurately follows the required angular orientation.

Slip feedback is an important cue in everyday object manipulation, but it is generally missing in tele-operation systems. To test the usefulness of simple, abstract types of feedback that warn the user about slip events, we tested the effect of auditory and haptic vibration feedback in a tele-operation task. Participants were asked to hold an object in a remote robot hand, and the force profiles that they exerted in response to slip events were measured. Haptic feedback did not significantly change the response characteristics, but auditory feedback did significantly improve response latency. A small but significant difference between haptic and auditory reaction times (60 ms) found in our control experiment might explain the difference between the feedback types.

In the recent assembly lines, the frequency of changing processes has been increasing in line with high mix production, but because these changes are carried out by operator, the burden of changing processes has increased as well. This situation has arisen because of the fact that since the robots being used at present automatic assembly lines are based on a simple teaching and playing back method, human workers must renew instructions for each act of changing a work object and also that dedicated machines are necessary due to the inability of making precision assembly,thereby inviting declines in total operational rates and increases in cost. These facts are limiting the use of robot based automation itself and are one of the important factors for the declining international competitive power. Under these circumstances, with the aim of constructing sophisticated production systems that are capable of dealing with process changes automatically without the use of human labor, a project called ""Research &amp; Development of Process Adaptive Flexible Robots""was proposed and was adopted to the Regional Consortium Research and Development Enterprise supported by the Ministry of Economy, Trade and Industry and by the New Energy and Industrial Technology Development Organization, and was adopted. The research period was to be 3 years from the fiscal year 1997 to the fiscal year 1999, and the total research fund was to be 360 million yen. In more specific terms, an engine assembly line and a semiconductor testing process were chosen as research subjects; and developmental research was carried out for elemental techniques that are necessary for the flexible execution of tasks such as piston insertion causing no damage to walls even with a minute clearance, or IC chip insertion causing no plastic deformation even with positional dislocation, though these tasks must be carried out when works change in type, size, etc.; and the researchers started the work of developing system integration technology that would achieve these task objectives in the optimal manner. Attention was focused rather on ""force control"" of which humans make skillful use than on developmental work based on the conventional position control technology, and development objectives were set not only to achieve a breakthrough for putting force control technology into practice by way of the integration of flexible force control and high aprecision position control and also by way of controlling the vibrations of complex machine systems, but also to demonstrate the research results by means of two prototypes of a flexible robot for assembly lines and an inserter for IC chip testing. The present special issue is a collection of results achieved by the participating research organization in the present research and development work, and it will be a great pleasure for its editors if this issue contribute seven a little. toward the future practical use of force control. Finally, sincere appreciation is expressed to the Ministry of Economy, Trade and Industry and the New Energy and Industrial Technology Development Organization for providing an opportunity for carrying out this research and development work, as well as to all the organizations for their participation in the project.

Fuzzy Predictive Algorithms Applied to Force Control of Robotic Manipulators

Compensation for the respiratory motion is a major challenge in the control design of medical robot ultrasound for accurately scanning the liver. Therefore, this paper presents an adaptive fuzzy proportional–integral–derivative (PID) force control of robot-assisted ultrasound to improve the guidance performance for anatomical or pathological structures of the liver under free breathing. A six degree-of-freedom robotic arm equipped with a 2-D ultrasound probe and a force sensor is simulated to perform the guidance procedure of the liver. The respiratory motion is also modeled and synchronized with retrospective liver ultrasound images. Without a priori knowledge of the nonlinear dynamic characteristics or mathematical modeling of the robot, the developed force controller exploits the advantages of fuzzy logic to directly auto-tune the PID controller gains for manipulating the robotic ultrasound probe on the patient’s abdomen at desired force levels in real time. A simulation framework has been developed to test the robotic force controller using four ultrasound image sequences of the liver. Compared to conventional PID controller with fixed gains, the adaptive fuzzy PID controller showed significantly better performance by resulting minimum tracked force errors of approximately 0.3 and 0.01 N with and without force sensor noise, respectively, for all tested image datasets. This simulation study presents potentially a good solution to accomplish the tracking task of desired probe forces during the robotic liver ultrasound guidance based on the developed fuzzy PID controller.

In this work, an ultrasound force control strategy for autonomous dry contact ultrasonic inspection of an object having rough surfaces is proposed. A fuzzy rules emulated network (FREN) controller with adaptation based on IF-THEN rules obtained from the physical system is developed. The control scheme is implemented on a three degree of freedom Cartesian manipulator robot that carries a soft contact hemispherical end effector equipped with an ultrasonic sensor. This allows smooth regulation of the transmitted ultrasound energy through the contact interface between the hemispherical probe and the rough surface. The controller is a pure model-free controller which does not require a mathematical model of the contact interaction. The effect of roughness condition at the contact interface, Hertzian interaction and the hysteretic effect due to nonlinearity of the elastomer material of the probe, on the performance of the controller is studied. The system was tested on five samples with surfaces having different values of roughness. It was shown that the system using the proposed scheme with adaption parameters is stable during the transition from noncontact to contact conditions. Also, it is shown that the developed ultrasound amplitude-force controller is able to reach and maintain a desired constant ultrasonic energy transfer to the test objects under variations of surface roughness conditions.

While previously proposed hardware on pin-based shape display has improved various technical aspects, there has been a clear limitation on the haptic quality of variable 'force' feedback. In this paper, we explore a novel haptic interaction design space with 'force' controlled shape display. Utilizing high performance linear actuators with current reading functionality, we built a 10 x 5 'force' shape display, named inFORCE, that can both detect and exert variable force on individual pins. By integrating closed-loop force control, our system can provide real-time variable haptic feedback in response to the way users the pins. Our haptic interaction design space includes volumetric haptic feedback, material emulation, layer snapping, and friction. Our proposed interaction methods, for example, enables people to press through'' computationally rendered dynamic shapes to understand the internal structure of 3D volumetric information. We also demonstrate a material property capturing functionality. Our technical evaluation and user study assesses the hardware capability and haptic perception through interaction with inFORCE. We also discuss application spaces that 'force' shape display can be used for.

Among the prevalent methods in linear bilateral teleoperation systems with communication channel time delays is to employ position and velocity signals in the control scheme. Utilizing force signals in such controllers significantly improves performance and reduces tracking error. However, measuring force signals in such cases, is one of the major difficulties. In this paper, a control scheme with human and environment force signals for linear bilateral teleoperation is proposed. In order to eliminate the measurement of forces in the control scheme, a force estimation approach based on disturbance observers is applied. The proposed approach guarantees asymptotic estimation of constant forces, and estimation error would only be bounded for time-varying external forces. To cope with the variations in human and environment force, sliding mode control is implemented. The stability and transparency condition in the teleoperation system with the designed control scheme is derived from the absolute stability concept. The intended control scheme guarantees the stability of the teleoperation system in the presence of time-varying human and environment forces. Experimental results indicate that the proposed control scheme improves position tracking in free motion and in contact with the environment. The force estimation approach also appropriately estimates human and environment forces.

In this paper, two novel adaptive finite-time control schemes are proposed for position tracking of nonlinear teleoperation system, which dynamic uncertainties, actuator saturation, and time-varying communication delays are considered. First, a novel auxiliary variable is designed to provide more stable performance. The radial basis function (RBF) neural network is introduced to estimate dynamic uncertainties. Second, two adaptive finite-time control schemes are investigated. In control scheme I, the RBF neural network and the gain switching strategy are applied to compensate the actuator saturation. In control scheme II, an auxiliary compensation filter and the compensation adaptive update laws, which contain the finite-time structure, are developed for dealing with saturation. Third, the finite-time adaptive controller is designed in each of these two control schemes. Based on the multiple Lyapunov function method, the closed-loop teleoperation system with these two control methods is proved to be bounded and finite-time stability. Finally, the simulation experiments are performed and the comparisons with other control methods are shown. The effectiveness of the proposed control schemes is demonstrated.