Slave Robot Research Articles

Master-slave robotic system for needle indentation and insertion

Bilateral control of a master-slave robotic system is a challenging issue in robotic-assisted minimally invasive surgery. It requires the knowledge on contact interaction between a surgical (slave) robot and soft tissues. This paper presents a master-slave robotic system for needle indentation and insertion. This master-slave robotic system is able to characterize the contact interaction between the robotic needle and soft tissues. A bilateral controller is implemented using a linear motor for robotic needle indentation and insertion. A new nonlinear state observer is developed to online monitor the contact interaction with soft tissues. Experimental results demonstrate the efficacy of the proposed master-slave robotic system for robotic needle indentation and needle insertion.

Enhanced transparency dual-user shared control teleoperation architecture with multiple adaptive dominance factors

In traditional dual-user shared control teleoperation, the users’ operational transparency is influenced by the dominance factorα. Especially when α = 1 and α = 0 the trainer or trainee cannot receive any information form the slave side. For enlarging the control flexibility and enhancing the system transparency, a novel method with multiple adaptive dominance factors is proposed in this paper. An ideal application of this method is on-line operation and supervision. The supervisor and operator can adjust the factors and switch the operation roles and states freely. Once the slave robot handled by the operator diverges from the planned path, the dominance factors will change adaptive to limit the operator’s movement. The adaptive principles are concluded from the dynamic performance measured by the measuring functions. The conclusions suggest that the varying range of the system dynamic performance is wider than the traditional method. In addition, considering the time delays between the slave and master sides, we proved the system stability conditions covering all the range of dominance factors. Finally, we make a discussion of the applying area of the novel shared control architecture.

Stable Nonlinear Trilateral Impedance Control for Dual-User Haptic Teleoperation Systems With Communication Delays

A new nonlinear adaptive impedance-based trilateral controller is proposed to ensure the absolute stability of multi-degrees-of-freedom (DOFs) dual-user haptic teleoperation systems subjected to communication delays. Using this strategy, reference impedance models are realized for the trilateral teleoperation system represented by a three-port network to facilitate cooperation of two human operators in order to perform a remote physical task. For this purpose, an impedance model defines the desired haptic interaction between the two human operators, while another impedance model specifies the desired behavior of the slave robot in terms of tracking the mater robots' trajectories during interaction with the remote environment. It is shown that different performance goals such as position synchronization and force reflection can be achieved via different adjustments to the impedance parameters. The sufficient conditions for the trilateral haptic system's absolute stability are investigated in terms of the impedance models' parameters. Accordingly, guidelines for modification of the impedance parameters are obtained to guarantee the absolute stability of the trilateral haptic system in the presence of communication time delays. A trilateral nonlinear version of the model reference adaptive impedance control (MRAIC) scheme is developed for implementing the proposed reference impedance models on the masters and the slave. The convergence of robots' trajectories to desired responses and the robustness against modeling uncertainties are ensured using the proposed controller as proven by the Lyapunov stability theorem. The proposed impedance-based control strategy is evaluated experimentally by employing a nonlinear multi-DOFs teleoperated trilateral haptic system with and without communication delays.

Cooperative modalities in robotic tele-rehabilitation using nonlinear bilateral impedance control

A nonlinear model reference adaptive bilateral impedance controller is proposed that can accommodate various cooperative tele-rehabilitation modes for patient–therapist interaction using a multi-DOF tele-robotic system. In this controller, two reference impedance models are implemented for the master and slave robots using new model reference adaptive control laws for the nonlinear bilateral teleoperation system. “Hand-over-hand” and “adjustable-flexibility” are two modes of patient–therapist cooperation that are realized using the proposed strategy. The Lyapunov-based stability proof guarantees the patient’s and the therapist’s safety during the cooperation and interaction with robots, even in the presence of modeling uncertainties of the multi-DOF teleoperation system. The performance of the proposed bilateral impedance controller is experimentally investigated for upper-limb tele-rehabilitation in the two mentioned cooperation modes.

Teleoperation Control Based on Combination of Wave Variable and Neural Networks

In this paper, a novel control scheme is developed for a teleoperation system, combining the radial basis function (RBF) neural networks (NNs) and wave variable technique to simultaneously compensate for the effects caused by communication delays and dynamics uncertainties. The teleoperation system is set up with a TouchX joystick as the master device and a simulated Baxter robot arm as the slave robot. The haptic feedback is provided to the human operator to sense the interaction force between the slave robot and the environment when manipulating the stylus of the joystick. To utilize the workspace of the telerobot as much as possible, a matching process is carried out between the master and the slave based on their kinematics models. The closed loop inverse kinematics (CLIK) method and RBF NN approximation technique are seamlessly integrated in the control design. To overcome the potential instability problem in the presence of delayed communication channels, wave variables and their corrections are effectively embedded into the control system, and Lyapunov-based analysis is performed to theoretically establish the closed-loop stability. Comparative experiments have been conducted for a trajectory tracking task, under the different conditions of various communication delays. Experimental results show that in terms of tracking performance and force reflection, the proposed control approach shows superior performance over the conventional methods.

Improved Delay-Dependent Stability Criteria for Telerobotic Systems With Time-Varying Delays

This paper addresses the synchronization problem of telerobotic systems, in which the master and slave robots are assumed to be serial manipulators and the communication-delays are assumed to be time-varying and nonsymmetric with known lower and upper bounds. Proportional derivative, proportional, and position-force control structures are considered for passive and nonpassive human operator. Using the Lyapunov-Krasovskii methodology, delay-dependent stability conditions of the closed-loop system are established in the form of linear matrix inequalities. The stability criteria derived in this paper is shown to be less conservative than some of the existing results within the literature, and they amend the calculation of the control parameters and ensure the stability and transparency of the system for larger bounds of communication-delays. Simulation studies are performed to demonstrate the effectiveness of the proposed stability criteria in obtaining a larger stability region for the system.

A Single-Port Robotic System for Transanal Microsurgery—Design and Validation

This letter introduces a single-port robotic platform for transanal endoscopic microsurgery (TEMS). Two robotically controlled articulated surgical instruments are inserted via a transanal approach to perform submucosal or full-thickness dissection. This system is intended to replace the conventional TEMS approach that uses manual laparoscopic instruments. The new system is based on master-slave robotically controlled tele-manipulation. The slave robot comprises a support arm that is mounted on the operating table, supporting a surgical port and a robotic platform that drives the surgical instruments. The master console includes a pair of haptic devices, as well as a three-dimensional display showing the live video stream of a stereo endoscope inserted through the surgical port. The surgical instrumentation consists of energy delivery devices, graspers, and needle drivers allowing a full TEMS procedure to be performed. Results from benchtop tests, ex vivo animal tissue evaluation, and in vivo studies demonstrate the clinical advantage of the proposed system.

A Hierarchical Optimization Approach to Robot Teleoperation and Virtual Fixtures Rendering

This paper presents a novel controller for bilateral teleoperation based on hierarchical constrained optimization techniques, that exploits motion constraints for the definition of virtual fixtures and haptic rendering. Our method allows the description of both rigid and compliant virtual fixtures, without the need of relative weight tuning as in previous approaches. Moreover, kinesthetic feedback due to each active constraint can be directly evaluated from the dual solution of the optimization algorithm, removing constraint penetration typical of penalty-based approaches and critical for telemanipulation where high accuracy is required. A transparency and stability analysis in case of communication delays is provided by relying on the classical two-port network formalism and linear control theory. An experimental evaluation of the approach for an object tracking task is carried out on a teleoperation system consisting of a 7-axis position-controlled slave robot with an eye-in-hand camera, and a 3 d.o.f. force-controlled master device.

Fast Stiffness Estimation using Acceleration-based Impedance Control and its Application to Bilateral Control

Communication delay between a master and a slave robot destabilizes a bilateral control system. Recent researches showed that an adaptive controller that dynamically determines the master’s controller gain according to the stiffness of the contact object is effective in improving stability. As the stability depends on the convergence speed of the estimated stiffness, this paper utilizes an acceleration-based impedance control for fast stiffness estimation. The validity of the proposed estimation method is verified by simulations. The convergence speed of the estimated stiffness is improved, and the control performance of bilateral control is improved accordingly.

Bilateral Control Between Electric and Hydraulic Actuators Using Linearization of Hydraulic Actuators

In this study, bilateral control between electric and hydraulic actuators is investigated. Bilateral control realizes telemanipulation of remote robots with the sense of touch. We focus on the system of local (master) robots, manipulated by operators that are driven by electric actuators, and slave robots, which work in remote places that are driven by hydraulic actuators. To obtain bilateral control in this situation, we find that combination of three key techniques is necessary. The first key is oblique coordinate control, which can decouple position and force controllers of bilateral control. The second key is linearization of hydraulic actuators as third-order systems including oil compression by using disturbance observers. In the absence of linearization, the design becomes practically impossible because of the need to apply complicated models. Since the master robots are second-order systems, and the slave robots are linearized as third-order systems, oblique coordinate control cannot be implemented. Then, the last key is the agreement of system order of electric and hydraulic actuators by using a pseudodifferentiator. Two conventional controllers and the proposed method are experimentally and analytically compared. The proposed method shows the best tracking performance and is the most stable in contact control among the three controllers.

Tele-echography of moving organs using an Impedance-controlled telerobotic system

A novel impedance-controlled teleoperation system is developed for robot-assisted tele-echography of moving organs such as heart, chest and breast during their natural motions (beating and/or breathing). The procedure of devising the two impedance models for the master and slave robots is developed such that (a) the slave robot holding the ultrasound (US) probe follows the master trajectory but complies with the oscillatory interaction force of the moving organ, and (b) the sonographer receives feedback from the non-oscillatory portion of the slave-organ interaction force via the master robot similar to the haptic feedback received in echography of a stationary organ. These goals are achieved via appropriate parameter adjustment in the desired impedance models without requiring any direct measurement and/or online prediction of the organ's motions. The stability and tracking convergence of the teleoperation system in the presence of communication delays and modeling uncertainties are proven in a Lyapunov-based framework. The performance of the proposed tele-echography system is evaluated experimentally using a master-slave telerobotic system, a US imaging system and a mechanical moving-organ simulator.

Shadow and Mirror Mode Bilateral Control for a Tele-Operated Robot System

This paper proposes the development of haptic robot system for rehabilitation exercises. Recently, haptic communication is widely applied in a robot system for sensing the force between robot and human operator. The bilateral control which consists of master and slave robot is used to transfer and receive action/ reaction force and position information. In this paper, the controlling of robot has been designed by considering the specification requirements of user. This master-slave robot system can be controlled by two different approaches: 1) by using the shadow mode and 2) by using the mirror mode. In the force control designed, such force sensor can use to measure the external force. It is shown that the reaction force response can be controlled. However, the problem of sensor noise and bandwidth are deteriorated the performance not only at the master or slave side but also at the whole control system. Thus, disturbance observer (DOB) has been proposed and used instead of force sensor for improve the performance and robustness of the whole system. In this study, the shadow and mirror mode of bilateral control is used with the master-slave robot for rehabilitation exercise. On the shadow mode slave robot is controlled according to the master robot like a shadow while mirror mode, slave robot has moved in the opposite direction like a reflection image. The results of each mode are represented in an experimental result. By using the proposed robot system, it is possible to apply in the rehabilitation process.

Research of the master-slave robot surgical system with the function of force feedback.

Surgical robots lack force feedback, which may lead to operation errors. In order to improve surgical outcomes, this research developed a new master-slave surgical robot, which was designed with an integrated force sensor. The new structure designed for the master-slave robot employs a force feedback mechanism. A six-dimensional force sensor was mounted on the tip of the slave robot's actuator. Sliding model control was adopted to control the slave robot. According to the movement of the master system manipulated by the surgeon, the slave's movement and the force feedback function were validated. The motion was completed, the standard deviation was calculated, and the force data were detected. Hence, force feedback was realized in the experiment. The surgical robot can help surgeons to complete trajectory motions with haptic sensation.

Design of a novel robotic system for minimally invasive surgery

PurposeRobot-assisted system for minimally invasive surgery (MIS) has been attracting more and more attentions. Compared with a traditional MIS, the robot-assisted system for MIS is able to overcome or reduce defects, such as poor hand-eye coordination, heavy labour intensity and limited motion of the instrument. The purpose of this paper is to design a novel robotic system for MIS applications.Design/methodology/approachA robotic system with three separate slave arms for MIS has been designed. In the proposed robot, a new mechanism was designed as the remote centre motion (RCM) mechanism to restrain the movement of instrument or laparoscope around the incision. Moreover, an improved instrument without coupling motion between wrist and grippers was developed to enhance its manipulability. A control system architecture was also developed, and an intuitive control method was applied to realize hand-eye coordination of the operator.FindingsFor the RCM mechanism, the workspace was analyzed and the positioning accuracy of the remote centre point was tested. The results show that the RCM mechanism can be applied to MIS. Furthermore, the master-slave trajectory tracking experiments reveal that slave robots are able to follow the movement of the master manipulators well. Finally, the feasibility of the robot-assisted system for MIS is proved by performing animal experiments successfully.Originality/valueThis paper offers a novel robotic system for MIS. It can accomplish the anticipated results.

Real-time control of bilateral teleoperation system with adaptive computed torque method

PurposeThis paper aims to use the adaptive computed torque control (ACTC) method to eliminate the kinematic and dynamic uncertainties of master and slave robots and for the control of the system in the presence of forces originating from human and environment interaction.Design/methodology/approachIn case of uncertainties in the robot parameters that are utilized in teleoperation studies and when the environment where interactions take place is not known and when there is a time delay, very serious problems take place in system performance. An adaptation rule was created to update uncertain parameters. In addition to this, disturbance observer was designed for slave robot. Lyapunov function was used to analyze the system’s position tracking and stability. A visual interface was designed to ensure that the movements of the master robot provided a visual feedback to the user.FindingsIn this study, a visual interface was created, and position and velocity control was achieved utilizing teleoperation; the system’s position tracking and stability were analyzed using the Lyapunov method; a simulation was applied in a real-time environment, and the performance results were analyzed.Originality/valueThis study consisted of both simulation and real-time studies. The teleoperation system, which was created in a laboratory environment, consisted of six-degree-of-freedom (DOF) master robots, six-DOF industrial robots and six-DOF virtual robots.

An MRI-Guided Telesurgery System Using a Fabry-Perot Interferometry Force Sensor and a Pneumatic Haptic Device.

This paper presents a surgical master-slave teleoperation system for percutaneous interventional procedures under continuous magnetic resonance imaging (MRI) guidance. The slave robot consists of a piezoelectrically actuated 6-degree-of-freedom (DOF) robot for needle placement with an integrated fiber optic force sensor (1-DOF axial force measurement) using the Fabry-Perot interferometry (FPI) sensing principle; it is configured to operate inside the bore of the MRI scanner during imaging. By leveraging the advantages of pneumatic and piezoelectric actuation in force and position control respectively, we have designed a pneumatically actuated master robot (haptic device) with strain gauge based force sensing that is configured to operate the slave from within the scanner room during imaging. The slave robot follows the insertion motion of the haptic device while the haptic device displays the needle insertion force as measured by the FPI sensor. Image interference evaluation demonstrates that the telesurgery system presents a signal to noise ratio reduction of less than 17% and less than 1% geometric distortion during simultaneous robot motion and imaging. Teleoperated needle insertion and rotation experiments were performed to reach 10 targets in a soft tissue-mimicking phantom with 0.70 ± 0.35 mm Cartesian space error.

Estimation of stochastic environment force for master–slave robotic system

The aim of this work is to obtain the maximum likelihood estimate (MLE) of controller-gain parameters \(\widehat{K} \) of the slave robot to determine the stochastic environment force. This is accomplished by measuring the joint positions of master and slave for a known master torque using stochastic difference equation. Here, the environmental force is modelled as a zero-mean white Gaussian random process. Therefore, the joint probability distribution function (pdf) of the slave angle over a given time duration can be computed as a function of the parameters ‘K’. This pdf is maximized with respect to ‘K’ to obtain the MLE of controller-gain parameters. Subsequently, convergence analysis of error in the estimates is performed. Also, an expression of the Cramer–Rao lower bound (CRLB) is derived to measure accuracy of the estimation. Comparison of CRLB with variance of MLE supports that our estimates are asymptotically efficient. The estimation performance is validated analytically and through simulations carried out on a two-link master–slave robotic system.

Telemanipulation of cooperative robots: a case of study

ABSTRACTThis article addresses the problem of dexterous robotic grasping by means of a telemanipulation system composed of a single master and two slave robot manipulators. The slave robots are analysed as a cooperative system where it is assumed that the robots can push but not pull the object. In order to achieve a stable rigid grasp, a centralised adaptive position-force control algorithm for the slave robots is proposed. On the other hand, a linear velocity observer for the master robot is developed to avoid numerical differentiation. A set of experiments with different human operators were carried out to show the good performance and capabilities of the proposed control-observer algorithm. In addition, the dynamic model and closed-loop dynamics of the telemanipulation is presented.

Exoskeletal master device for dual arm robot teaching

Dual arm robots are used as humanoid or industrial robots for assembly work. Each arm of these robots is generally composed of 7-DOF to mimic the human arm. For motion teaching of this 7-DOF robot arm, upper limb exoskeletal master devices can be used, and each arm of the upper limb exoskeletal master device can also be composed of 7-DOF. However, the motions of the human shoulder are complex and the lack of DOF in the exoskeletal master device limits the wearer's motions and makes the wearer feel uncomfortable. We propose a compact-sized exoskeletal master device, each of whose arms are composed of two serially connected parts. One is a 6-DOF shoulder–elbow mechanism and the other is a 3-DOF wrist mechanism. The 6-DOF mechanism serially connects the base frame near the shoulder to a point on the forearm, and the center of rotation of the shoulder joint is shifted to the outside of the human shoulder. In addition, the 6-DOF mechanism includes a long stroke but short reduced-length prismatic joint. This 6-DOF mechanism enables unconstrained and comfortable shoulder motions. The 3-DOF wrist mechanism corresponds to forearm pronation/supination, wrist flexion/extension, and wrist adduction/abduction. The closed-loop inverse kinematic scheme is applied for the dual arm robot control in the task space. The performance of the exoskeletal master devices and control strategies are verified through experiments using a 14-DOF dual arm slave robot.

Force-Controlled Exploration for Updating Virtual Fixture Geometry in Model-Mediated Telemanipulation

This paper proposes an approach for using force-controlled exploration data to update and register an a priori virtual fixture geometry to a corresponding deformed and displaced physical environment. An approach for safe exploration implementing hybrid motion/force control is presented on the slave robot side. During exploration, the shape and the local surface normals of the environment are estimated and saved in an exploration data set. The geometric data collected during this exploration scan are used to deform and register the a priori environment model to the exploration data set. The environment registration is achieved using a deformable registration based on the coherent point drift method. The task-description of the high-level assistive telemanipulation law, called a virtual fixture (VF), is then deformed and registered in the new environment. The new model is updated and used within a model-mediated telemanipulation framework. The approach is experimentally validated using a da-Vinci research kit (dVRK) master interface, a dVRK patient side manipulator, and a Cartesian stage robot. Experiments demonstrate that the updated VF and the updated model allow the users to improve their path following performance and to shorten their completion time when the updated path following VF is applied. The approach presented has direct bearing on a multitude of surgical applications including force-controlled ablation.