Interaction model between elastic objects for haptic feedback considering collisions of soft tissue

Mantis is a highly scalable system architecture that democratizes haptic devices by enabling designers to create accurate, multiform and accessible force feedback systems. Mantis uses brushless DC motors, custom electronic controllers, and an admittance control scheme to achieve stable high-quality haptic rendering. It enables common desktop form factors but also: large workspaces (multiple arm lengths), multiple arm workspaces, and mobile workspaces. It also uses accessible components and costs significantly less than typical high-fidelity force feedback solutions which are often confined to research labs. We present our design and show that Mantis can reproduce the haptic fidelity of common robotic arms. We demonstrate its multiform ability by implementing five systems: a single desktop-sized device, a single large workspace device, a large workspace system with four points of feedback, a mobile system and a wearable one.

This paper presents the control of a pneumatically actuated master–slave system intended for teleoperated needle insertion in the liver under magnetic resonance imaging (MRI) guidance. It addresses the challenge of achieving accurate needle positioning and force feedback to the operator in the case of pneumatic actuation with significant friction. Using time-delay position control as the basis, we investigate force feedback via impedance control and admittance control. For impedance control, we propose a new adaptive friction compensation algorithm that only requires a single tuning parameter. Experiments on a 1-degree of freedom prototype system using silicone rubber phantoms with distinct densities highlight the differences between impedance control and admittance control, and demonstrate superior performance compared with a traditional impedance control scheme.

Haptic devices need to render accurate force to a human operator in order to create a virtual environment from a remote real environment. Existing end-effector type haptic devices employ parallel mechanisms to achieve force interaction in multiple degrees-of-freedom (DoF). Those parallel mechanisms have non-constant Jacobian matrices that create difficulties in the actuator and controller design for accurate haptic force interaction. This paper presents a 3-DoF translational parallel manipulator (TPM) with a constant Jacobian matrix to facilitate the force and impedance controller design. Instead of using external force sensors, series elastic actuators (SEAs) are used for the proposed device to realize the force rendering. SEAs can render more accurate output force and stiffness while the inertia and friction problems of using a gearhead can be ignored. In this paper, the modeling, design, and control of the haptic device are established to show the merits of the proposed TPM. Initial force control experiments demonstrate the accuracy and speed of SEA-based force control. We expect that this novel haptic device can serve as an alternative for robotic teleoperations requiring accurate force sensing and control.

Haptic rendering is a highly device-dependent process. Accordingly, haptic rendering algorithms should be designed regarding the specific physical features of a haptic device. The Immersion CyberGrasp is a force feedback device which can provide an individual force roughly perpendicular to the fingertip of each finger. In this paper, we propose a novel force rendering algorithm for the Immersion CyberGrasp considering the feature of area contacts between the virtual hand avatar and target geometric models. Line segment clusters are used as haptic proxies for the real-time collision detection between the fingertips and target geometric models. Force computations are conducted directly using the collision detection results. Spatial subdivision is performed on target geometric models to facilitate real-time collision detection. Experimental results show that our algorithm can provide stable and realistic force feedback.

Percutaneous medical procedures rely upon clinicians performing precise needle insertion in soft tissue. The utility of haptic simulation systems in training clinicians for these procedures is highly dependent upon the ability to render accurate insertion force feedback. This paper presents a piecewise mathematical model for insertion force that does not require tissue material properties, detailed mechanical approximations, or complex computations. With manipulation of model parameters, a wide variety of insertion tasks and clinical scenarios can be modeled. Through needle insertion experiments and parameter estimation, this model was demonstrated to replicate the insertion forces associated with a variety of needle and tissue types. In 11 of 12 needle and tissue combinations tested, the model replicated the insertion force with an average absolute mean error of less than 0.065 N.

Robot-assisted minimally invasive surgery (MIS) offers several advantages over traditional surgery, including reduced trauma and faster recovery times, leading to its increasingly widespread application. In robot-assisted MIS, the direct contact between surgical instruments and the patient's tissues demands higher precision in movement and enhanced sensing capabilities. This paper focuses on investigating the critical technologies of time delay and gripping force feedback in laparoscopic surgery robot. We propose an actuators-driven surgical robot equipped with gripping force feedback. An experimental system was constructed and control parameters were optimized to achieve ± 180° rotation and 0-60° gripping freedom in primary-secondary control. The experimental measurements indicated that the time delay of the primary-secondary robotic system was maintained at approximately 10ms. To evaluate the gripping force feedback, three different materials-silicone simulated skin, silicone rubber, and ceramic-were used to simulate human tissue, tumors, and bones, respectively. Sensor measurements of the gripping force feedback revealed that the force required to grip ceramic was twice that needed for gripping the silicone rubber and four times that for gripping the silicone simulated skin. The proposed actuators-driven surgical robot system demonstrates precise primary-secondary synchronous control and accurate gripping force feedback, offering significant potential for the further development of advanced surgical systems.

Smooth haptic force feedback is an important task for multirate 6-DOF haptic rendering for both rigid and deformable objects. The update rate of the haptic force may be too low and changed during the simulation as the high computation time is required for complex physical simulation. Therefore, to implement a stable and smooth haptic rendering, we need a method to update the force in a higher regular rate during the physical simulation. We propose a prediction method using interpolation to calculate smooth haptic interaction force in a high update rate. The auto-regressive model is used to predict the force value based on the previous haptic force calculation. In addition, we introduce a spline function to interpolate force values for the haptic force output. We demonstrate that the proposed method can provide smooth and accurate haptic force feedback in a high update rate during a low frequency physical simulation of complex and deformable models. In the experiments, we show the feasibility of the proposed method and compare its accuracy and stability with the linear force prediction algorithm.

Design and Evaluation of Laparoscopic Forceps with Accurate Force Feedback

In this paper the effect of force control in the fidelity of a low-force five degree-of-freedom (dof) haptic mechanism is investigated. Strict conditions that guarantee stability are presented. Our effort focuses on haptic devices, able to reproduce accurate low forces in a soft virtual environment, rather than large forces in stiff virtual environments. Open and closed loop controllers are applied to a haptic mechanism, which is a part of a training medical simulator for urological operations, and consists of a two-dof, five bar linkage and a three-dof spherical joint. The force control algorithm is described and discussed. Open and closed loop schemes are compared. Simulation and experimental results of the force control law applied to the five-dof mechanism are presented and discussed. It is shown that the use of closed loop force control law increases the haptic device fidelity and the realism of the simulation. It is also shown that in case of haptic devices used in soft virtual environments, issues like signal noise and device stiffness are more critical than maintaining system stability.

To provide more realistic feedback force for training during surgery simulation, a novel model of interaction between a virtual surgical tool and surface of soft tissue was created based on experimental data. Using a self-designed device, normal contact force and tangential friction were tested. A generalized Kelvin-element was introduced to model the nonlinear and relaxation characteristics of the contact force. The parameters of the model were obtained by the least square curve fitting of experimental data. A surgical tool and deformable skin model were constructed in a virtual environment. Phantom Desktop interface allows the operator perceive the feedback force during interacting the virtual skin model.KeywordsVirtual surgeryFeedback forceMass-spring model

In this paper, a novel haptic interaction framework for deformable objects is introduced and discussed. Unlike existing frameworks, the proposed approach is based on point-based mechanics framework. Contrary to the finite-element method, the method of this paper does not rely on any predefined mesh representation, and it also incorporates real material properties in the modeling framework. As a result, the haptic interaction produces realistic model behaviour and force feedback. In addition, the framework can be constructed using the actual 3D volume data obtained from various imaging modalities. In this paper, preliminarily implementation issues of this new frame work are discussed and experimental data are compared to the FEM.

Haptic devices that provide robust and realistic force feedback are generally grounded to counterweight the applied force, prohibiting their use in mobile devices. Many ungrounded force-feedback devices rely on the gyro effect to produce torques on the human body, but their active control systems render them extremely bulky for implementation in small mobile devices. We present GyroTab, a relatively flat handheld system that utilizes the gyro effect to provide torque feedback. GyroTab relies on the user to produce an input torque and provides feedback by opposing that torque, making its feedback reactive to the user's motion. We describe the implementation of GyroTab, discuss the kinds of feedback it generates, and explore some of the psychophysical results we obtained from a study with the device.

Virtual reality training simulations to acquire surgical skills are important for increasing patient safety and save valuable resources, e.g., cadavers, supervision and operating room time. However, as surgery is a craft, simulators must not only provide a high degree of visual realism, but especially a realistic haptic behavior. While such simulators exist for surgeries like laparoscopy or arthroscopy, other surgical fields, especially where large forces need to be exerted, like total hip arthroplasty (THA; implantation of a hip joint protheses), lack realistic VR training simulations. In this paper we present for the first time a novel VR training simulation for the five steps of THA (from femur head resection to stem implantation) with realis-tic haptic feedback. To achieve this, a novel haptic hammering device, an upgraded version of the Virtuose 6D haptic device from Haption, novel algorithms for collision detection, haptic rendering, and material removal are introduced. In a study with 17 surgeons of diverse experience levels, we confirmed the realism, usefulness and usability of our novel methods.

Most surgical simulators leverage virtual or bench models to simulate reality. This study proposes and validates a method for workspace configuration of a surgical simulator which utilizes a haptic device for interaction with a virtual model and a bench model to provide additional tactile feedback based on planned surgical manoeuvers. Numerical analyses were completed to determine the workspace and position of a haptic device, relative to the bench model, used in the surgical simulator, and the determined configuration was validated using device limitations and user data from surgical and nonsurgical users. For the validation, surgeons performed an identical surgery on a cadaver prior to using the simulator, and their trajectories were then compared to the determined workspace for the haptic device. The configuration of the simulator was determined appropriate through workspace analysis and the collected user trajectories. Statistical analyses suggest differences in trajectories between the participating surgeons which were not affected by the imposed haptic workspace. This study, therefore, demonstrates a method to optimally position a haptic device with respect to a bench model while meeting the manoeuverability needs of a surgical procedure. The validation method identified workspace position and user trajectory towards ideal configuration of a mixed reality simulator.

Network delay in haptic-based CVEs (collaborative virtual environments) severely deteriorates the haptic interaction quality (e.g., larger force feedback than real). In order to compensate this delay effect, existing studies dynamically change spring and damper coefficients according to the network delay. However, it is difficult to choose proper coefficients to offset the delay effect by precisely reflecting virtual object characteristics. In this paper, a new delay-compensation scheme based on the force feedback prediction is proposed to improve the force feedback experience. By predicting the virtual object movements and force feedback, the proposed scheme in client side provides timely force feedback to a user. Then, it gradually converges to real (but delayed) information from the server in order to maintain the consistency of virtual environment. According to the experiment results, the proposed scheme can improve the haptic interaction quality by providing more realistic force feedback similar to that of no network delay.