In robotic teleoperation, it is crucial to be able to dynamically adjust interactions with the environment. Drawing inspiration from human behavior during interactions, Variable Impedance Control (VIC) has been widely adopted to enhance robotic flexibility and adaptability. However, maintaining the passivity of such control systems remains a critical safety concern. This paper introduces an optimization-based framework for passive variable impedance control in bilateral teleoperation, combining the advantages of Passivity Filters (PFs), Time-Domain Passivity (TDP) control, and Passive-Set-Position-Modulation (PSPM). The method solves an optimization problem aimed at dissipating the energy that could lead to a lack of passivity. The proposed method is assessed through experiments, illustrating its ability to keep the teleoperation system passive and safe under a variable impedance profile.

In application domains such as surgical robotics, fully autonomous control remains a long-term ambition and the systems are mostly teleoperated. In this article, the presence of an operator in-the-loop is exploited to perform the online registration of an initially inaccurate haptic guidance and the calibration of robot kinematic models using operator’s intention instead of relying on exteroceptive sensors. This is used to improve online haptic guidance in the context of shared control, or to progress toward automatic task completion after an initial learning phase. The method presented in this article is based on an optimization in the task space to minimize the errors between the executed and desired trajectories, both estimated from models. This approach is particularly relevant when the execution of a planned task would suffer from errors that exteroceptive measurements could not fully correct, because of sensor inaccuracy or unavailability. A user study realized for a drawing task is detailed to illustrate that initially inaccurate task registration and robot models can be corrected from user inputs only. The results show that the proposed algorithm can learn the correct models, which in turns significantly improves the quality of the haptic guidance and decreases path deviations during the teleoperated task.

In this work, we use recent developments in the field of adaptive robust Model Predictive Control (MPC) to build a controller for bilateral teleoperation systems. To guarantee robust constraint satisfaction, we incorporate polytopic tube controllers in the MPC design. In addition, we use online learning methods to learn the environment model. Namely, we use set membership learning to learn the parametric uncertainty bounds and reduce the conservatism of the robust controller, and we combine it with least mean square method to learn a point estimate of the model parameters, which enhances the controller performance. Our simulation demonstrates the effectiveness of the proposed approach in maintaining robust constraint satisfaction and enhancing performance by learning during teleoperation tasks.

This paper deals with the problem of needle steering in deformable tissues subject to physiological motions. A novel shared control method is proposed, which combines an automatic needle steering algorithm with the motions applied by the radiologist, in order to place the needle tip at the desired location. The core motivation is to leave potentially dangerous decisions and actions to the practitioner, whereas complex non-intuitive manipulations of the needle are performed automatically, in particular to compensate for breathing motions. The most original part of the present work lies in the method used to combine user inputs with a closed-loop automatic needle steering control method based on inverse Finite Element simulations. The method is evaluated with a realistic virtual environment using 2D X-ray projection images. The results are compared with those obtained with a fully teleoperated system, on the one hand, and with a fully automatic solution, on the other hand. These experiments show that the shared control solution allows for a better needle tip placement when only projection imaging is available.

Haptic guidance can improve accuracy and dexterity during the teleoperation of a robot, but only if the model of the task used to provide the assistance is accurate. In medical robotics, the registration of a task from pre-operative planning from medical images to the robot’s task-space can be erroneous. Additionally, the deformability of the environment can require online correction of a planned task. Therefore, we propose a method to update the geometry and the registration of a pathfollowing task online. This model is simultaneously used to physically guide the user during the teleoperation. Experimental results obtained on a haptic interface show the validity of the approach for a simulated 2D task.

Bilateral teleoperation under rate mode is known to be a difficult problem in terms of stability, especially when the slave manipulator interacts with a time-varying environment. This paper presents an energy based variable admittance control approach, whose principle combines the monitoring and the regulation of the energy exchanges with a passivity tank. It allows stable interactions with force feedback for any desired inertia, damping and stiffness parameters. Experiments are conducted to assess the efficiency of the proposed approach using an experimental setup with a variable stiffness environment. The obtained results illustrate the ability of the proposed strategy to stabilize a system otherwise unstable, with little effect on the transparency of the teleoperation system.

This paper introduces a method for robotic steering of a flexible needle inside moving and deformable tissues. The method relies on a set of objective functions allowing to automatically steer the needle along a predefined path. In order to follow the desired trajectory, an inverse problem linking the motion of the robot end effector with the objective functions is solved using a Finite Element simulation. The main contribution of the article is the new constraint-based formulation of the objective functions allowing to: 1) significantly reduce the computation time; 2) increase the accuracy and stability of the simulation-guided needle insertion. The method is illustrated, and its performances are characterized in a realistic framework, using a direct simulation of the respiratory motion generated from in vivo data of a pig. Despite the highly non-linear behavior of the numerical simulation and the significant deformations occurring during the insertion, the obtained performances enable the possibility to follow the trajectory with the desired accuracy for medical purpose.

Robots are more and more often designed in order to perform tasks in synergy with human operators. In this context, a current research focus for collaborative robotics lies in the design of high-performance control solutions, which ensure security in spite of unmodeled external forces. The present work provides a method based on Model Predictive Control (MPC) to allow compliant behavior when interacting with an environment, while respecting practical robotic constraints. The study shows in particular how to define the impedance control problem as a MPC problem. The approach is validated with an experimental setup including a collaborative robot. The obtained results emphasize the ability of this control strategy to solve constraints like speed, energy or jerk limits, which have a direct impact on the operator's security during human-robot compliant interactions.

While impedance control is one of the most commonly used strategies for robot interaction control, variable impedance control is a more recent preoccupation. If designing impedance control with varying parameters allows increasing the system flexibility and dexterity, it is still a challenging issue, as it may result in a loss of passivity of the control system. This has an important impact on the stability and therefore on the safety of the interaction. In this paper, we propose methods to design passivity filters that guarantee passivity of the interaction. They aim at either checking whether a desired impedance profile is passive, or modifying it if required.

Surgeons performing laparoscopic surgery experience distortion when perceiving the stiffness of a patient's tissues. This is due to the lever effect induced by the introduction of instruments in their patient's body through a fulcrum. To address this problem, we propose to use the comanipulation paradigm. A robotic device is connected to the handle of the instrument while simultaneously being held by the surgeon. This device applies a force on the handle that reflects the force measured at the tool tip, with a gain that depends on the lever ratio. The implementation of this method is presented on an experimental setup and a preliminary assessment experiment is presented.

In this paper, we present a novel identification approach to model the EMG-Force relationship of the human arm, reduced to a single degree of freedom (1-DoF) for simplicity. Specifically, we exploit the Linear Parameter Varying (LPV) framework. The inputs of the model are the electromyographic (EMG) signals acquired on two muscles of the upper arm, biceps brachii and triceps brachii, and two muscles of the forearm, brachioradialis and flexor carpi radialis. The output of the model is the force produced at the hand actuating the elbow. Because of the position-dependency of the system, the elbow angle is used as scheduling signal for the LPV model. Accurate modeling of the human arm with this approach opens new possibilities in terms of robot control for physical Human-Robot Interaction and rehabilitation robotics.

This paper presents a new actuator designed to produce forces under short stroke displacements. Two variants of the prototype have been manufactured using Multi-Material Additive Manufacturing process, based on a flexible origami-inspired architecture. The structure consists of an airtight chamber constituted by rigid plates combined with flexible hinges and surfaces in order to allow the generation of motion. We propose several insights on integration issues such as limited material resistance and maximum range of motion. Both versions of the prototype are then tested to assess their performances for single strokes and cyclic loading.

Automatic robot / Computed Tomography (CT) scanner registration is an important feature for robot-assisted percutaneous needle placement under CT-scanner. This registration can be done using 3D images, but for fast, low X-ray radiation it is interesting to be able to perform the registration with a single slice. In this paper, a new marker is proposed, which allows to estimate the pose of a device using a single slice. This marker, called ZCM, consists of three circles or ellipses arranged in a Z-shape configuration. It is shown that it provides a larger workspace (i.e. a larger set of visible configurations) for pose measurement than the standard Brown-Roberts-Wells, while maintaining a good accuracy. A closed-form method is proposed for solving the pose estimation with this marker. Simulations and experimental tests using a mock-up patient-mounted robot are presented and confirm the theoretical analysis.

The design of intrinsically safe systems is an important issue in the development of physical human-robot interactions, in particular in the medical field. In this paper, we explore a new approach, motivated by a medical robotic application framework. The system is statically balanced, in any configuration. Its actuation results from a controllable modification of the balancing. This notably limits the interaction forces between the robot and its environment, but yet authorizes important features like accurate positioning or tracking while in contact, which are key characteristics for the application. In this paper, the robotic device principle is introduced, together with its original actuation, which is developed and experimentally assessed for a one DOF system. Capabilities such as trajectory tracking in the free space, reaction to unexpected collision and tracking of a moving environment are reported. The generalization to more DOF, as required to complete medical tasks, is also discussed.

In this paper, we focus on the technology issues to be solved to develop a cable-driven robot compatible with Magnetic Resonance Imaging constraints. This study is based on the design of a new compact cable-driven manipulator with remote actuators, initially developed for prostate interventions. One of the originalities of the system is to use an instrumented structure to evaluate the cable tensions and lengths in order to perform an adequate control. The sensors assessment has been experimentally achieved and the necessity to introduce a new control strategy using the developed sensors has been demonstrated.

In this paper a bilateral teleoperation scheme is proposed to compensate force perturbations due to repetitive motions of the environment. Based on a Repetitive-Generalized Predictive Controller (R-GPC), it allows to reject periodical disturbances as those generated by respiration motion under breathing apparatus while in contact with the environment. The proposed method is detailed and experimental results are presented for the first time, using a 1-DOF teleoperation testbed.

Low-cost piezoresistive sensors can be of great interest in robotic applications due not only to their advantageous cost but to their dimension as well, which enables an advanced mechanical integration. In this paper, a comparison of two commercial piezoresistive sensors based on different technologies is performed in the case of a medical robotics application. The existence of significant nonlinearities in their dynamic behavior is demonstrated, and a nonlinear modeling is proposed. A compensation scheme is developed for the sensor with the largest nonlinearities before discussing the selection of a sensor for dynamic applications. It is shown that force control is achievable with these kinds of sensors, in spite of their drawbacks. Experiments with both types of sensors are presented, including force control with a medical robot.

In this paper, we study a class of one degree-of-freedom mechanisms in order to design linear haptic interfaces. They allow to perform straight line motions with only revolute joints, thus limiting the friction that characterizes linear bearings. We particularly describe the characteristics of these systems and their good properties to design haptic displays: parallel architecture, very good linearity, good use of the actuator torque. The Hoeken's mechanism which has the best characteristics to build a direct drive general purpose haptic display is selected. We present the fabricated prototype and its evaluation in terms of bandwidth, Coulomb friction and apparent mass.

In this paper, nonlinear modeling of low cost force sensors is considered for force control applications in robotic or biomechanical applications. Commercial force sensors are often expensive, with a limited use in severe conditions such as the presence of a strong magnetic field. On the contrary, thin film piezoresistive sensors such as the Tekscan Flexiforce and the Interlink FSR sensors are of low cost and can be considered in such an environment. Only a few information is however available on their dynamic properties. We therefore provide an experimental study of their dynamic behavior, showing nonlinear properties. Identification is then achieved, and a compensation model is proposed. A force control experiment is finally presented to evaluate the compensation scheme.

The development of new medical therapies often require experiments on small animals. In order to improve the medical protocol during treatments with needles, we propose a new robotic needle insertion system using CT-scan imaging and visual servoing. The biologist defines the skin entry point and the target to be reached in the CT-image. The needle target is then expressed in the robot frame thanks to a 3D registration between the 3D structured light reconstruction of the animal bed and the 3D model obtained from the CT-scan data. Finally the needle pointing is performed thanks to a 2D visual servoing. This approach is independent of the needle model and allows a high positioning accuracy: less than 0.5 pixel for the tip of the needle and less than 10-3rad for the direction. Experiments show promising results: a needle with a diameter of 0.72 mm can be inserted through two holes with diameters of 2 mm.

This paper addresses the influence of human operators on telemanipulators bilateral control. A method to deal with the user variability is proposed, based on the auto-tuning of the force controller at the master side. First, the approach is evaluated experimentally with a group of users in the context of nonlinear interactions with soft tissues, showing very good tracking performances, for both force and position. Second, a robustness analysis is presented that allows to prove the stability of the system for large variations of the behavior of both the environment and the user. This analysis is based on an original uncertain model of the user.

The commercial development of haptic devices is very promising. Existing systems are often 6-degree-of-freedom mechanisms equipped with a stylus that acts as a tool. They exhibit force feedback for 3 or 6 degrees of freedom of their end-effector, depending on whether only forces or both forces and torques are rendered. Some planar devices are also used but oddly, one-degree-of-freedom linear haptic devices are quite rare. This lack can probably be explained by the necessary mechanical transformations that are required to achieve linear motions with rotary motors. In this paper, we review several possible structures and present the design of a new one-degree-of-freedom linear haptic device with a limited number of joints and a compact design, compatible with rotary actuation. We evaluate this device in the telemanipulation context.

Medical robotics is a field where dedicated mechanisms have an increasing importance. The strong operating room constraints, both medical and practical, lead to heavily customized solutions. In this paper, we consider the practical problems that must be solved to build a robotic system dedicated to medical interventions under CT-scan guidance. This compact robotic assistant is placed on the patient what raises new generic robotic design problems. Practical solutions together with the evaluation of a prototype are presented in this paper

We propose a systematic modelling of the nonholonomic mobile manipulators built from a robotic arm mounted on a wheeled mobile platform. It extends the fundamental notions of nonholonomy, mobility and maneuverability to the case of these hybrid holonomic/nonholonomic systems. It offers unambiguous definitions and models to the designer of kinematic control laws.

We propose a generic scheme to solve the kinematic control problem of wheeled mobile manipulators when the operational motion is imposed. We generalize the Additional Task Method to solve the control problem of these redundant nonholonomic systems.

We extend the standard definition of manipulability to the case of a nonholonomic mobile manipulator built from an n joint robotic arm and a nonholonomic mobile platform. The effects of mounting the arm on a nonholonomic platform are shown through the analysis of the manipulability thus defined. Applications of criteria inherited from manipulability considerations are given to justify design and to generate the controls of our system.