6-DOF Haptic Device Research Articles

Design and Evaluation of a 3-DoF Haptic Device for Directional Shear Cues on the Forearm.

Wearable haptic devices on the forearm can relay information from virtual agents, robots, and other humans while leaving the hands free. We introduce and test a new wearable haptic device that uses soft actuators to provide normal and shear force to the skin of the forearm. A rigid housing and gear motor are used to control the direction of the shear force. A 6-axis force/torque sensor, distance sensor, and pressure sensors are integrated to quantify how the soft tactor interacts with the skin. When worn by participants, the device delivered consistent shear forces of up to 0.64 N and normal forces of up to 0.56 N over distances as large as 14.3 mm. To understand cue saliency, we conducted a user study asking participants to identify linear shear directional cues in a 4-direction task and an 8-direction task with different cue speeds, travel distances, and contact patterns. Participants identified cues with longer travel distances best, with an 85.1% accuracy in the 4-direction task, and a 43.5% accuracy in the 8-direction task. Participants had a directional bias, with a preferential response in the axis towards and away from the wrist bone.

A Shared-Control Teleoperation Architecture for Nonprehensile Object Transportation

This article proposes a shared-control teleoperation architecture for robot manipulators transporting an object on a tray. Differently from many existing studies about remotely operated robots with firm grasping capabilities, we consider the case in which, in principle, the object can break its contact with the robot end-effector. The proposed shared-control approach automatically regulates the remote robot motion commanded by the user and the end-effector orientation to prevent the object from sliding over the tray. Furthermore, the human operator is provided with haptic cues informing about the discrepancy between the commanded and executed robot motion, which assist the operator throughout the task execution. We carried out trajectory tracking experiments employing an autonomous 7-degree-of-freedom (DoF) manipulator and compared the results obtained using the proposed approach with two different control schemes (i.e., constant tray orientation and no motion adjustment). We also carried out a human-subjects study involving 18 participants in which a 3-DoF haptic device was used to teleoperate the robot linear motion and display haptic cues to the operator. In all experiments, the results clearly show that our control approach outperforms the other solutions in terms of sliding prevention, robustness, commands tracking, and user’s preference.

A position control-based approach to haptic rendering of stiff objects using piece-wise linear model

In traditional force rendering approaches, it is quite popular to model a virtual stiff wall as a spring-damper system to compute the interaction force, which can easily lead to unstable behavior. In this paper, we present an approach to ensure no penetration into the wall by position control. The approach approximates the nonlinear model of a 6-DOF parallel-structure haptic device by a piece-wise linear model to improve the performance compared with a controller designed from a one-point linearized model in haptic rendering. A simulation-based performance comparison study shows that the new controller can render higher stiffness than the previous solution.

Asymmetric Bilateral Telerobotic System With Shared Autonomy Control

The asymmetry in bilateral teleoperation, i.e., the differences of mechanical structures, sizes, and number of joints between the master and slave robots, can introduce kinematics redundancy and workspace inequality problems. In this article, a novel shared autonomy control strategy is proposed for handling the asymmetry of bilateral teleoperation, which has two main contributions. First, to deal with kinematics redundancy, the proposed strategy provides a self-regulation algorithm of orientation that allows the operator to solely use the master position command to simultaneously control the slave's position and orientation. Second, to deal with workspace inequality, the proposed strategy enables the slave's workspace to be dynamically tunable to adapt to various task spaces without influencing the smoothness of the robot's movement. The experiments on a platform consisting of a six-degree of freedom (DoF) UR10 robot and a 3-DoF haptic device are given to validate the effectiveness of the proposed control strategy.

Development and assessment of a haptic-enabled holographic surgical simulator for renal biopsy training

In this paper, a high-immersive surgical training system for renal biopsy using holographic demonstration and haptic feedback is presented to push the limitation of virtual medical training development. Proposed system is including: holographic visual rendering pipeline reconstructed by the patient-specific CT images; haptic rendering pipeline implemented by the dual-hands 6-DOF haptic devices connected with surgical instruments of image guide and immersive 3D display learning operating room environment. Twenty-four medical students and eight experienced thoracic surgeons from the Yunnan First People’s Hospital are invited to evaluate our holographic-based training system through the subjective and objective assessment test, respectively. Experiment result from the face, content, improvement, and construct evaluations demonstrated a high performance than the existing VR-based trainer, especially the puncture accuracy of medical students’ group, was improved by 30.8% after training.

A 6-DOF haptic manipulation system to verify assembly procedures on CAD models

During the design phase of products and before going into production, it is necessary to verify the presence of mechanical plays, tolerances, and encumbrances on production mockups. This work introduces a multimodal system that allows verifying assembly procedures of products in Virtual Reality starting directly from CAD models. Thus leveraging the costs and speeding up the assessment phase in product design. For this purpose, the design of a novel 6-DOF Haptic device is presented. The achieved performance of the system has been validated in a demonstration scenario employing state-of-the-art volumetric rendering of interaction forces together with a stereoscopic visualization setup.

Experiments and assessments of a 3-DOF haptic device for interactive operation

Haptic devices have been applied in interactive operation to perform contact tasks. To explore the haptic perception characteristics of typical push-pull and rotation operation, an experimental system was built by incorporating a three degrees of freedom (3-DOF) haptic device and the virtual environment. In this system, the haptic device is used to provide motion commands to control the avatar in the virtual environment and to exert haptic feedback on the human operator generated by three motors. In order to evaluate the main influential factors of interactive system based on haptic devices, ergonomic assessments are designed and experimentally implemented. Preliminary studies on the factors including restoring force, guidance force, speed of the virtual avatar, and the arm length have been conducted. The results are of great significance for the design of a haptic device and haptic interaction system by analyzing the specific requirements of ergonomics.

DYNAMIC COMPUTATION OF HAPTIC-ROBOT DEVICES FOR CONTROL OF A SURGICAL TRAINING SYSTEM

This paper presents a new control model of the haptic device for the closed loop teleoperation of a minimal surgery training system. Dynamics of a 6-DOF parallel haptic device is computed and compensated to make a decoupled linearization control model. In teleoperation system, the master is the 6-DOF haptic device and the slave is the 6-DOF serial robot. The master haptic device provides the trajectories for the slave serial robot through the operation of user’s hand on the steering handle while the slave robot sends feedback forces on its end effector to the master controller in order to generate forces/moments on the steering handle of haptic master. In this manner the user’s hand will feel the forces/moments as the same those of the robot end effector. The feeling force tracking performances of system can be improved by using dynamic compensation and decoupled linearization controller based on fuzzy PID algorithms. Experiment results indicate that the dynamic compensation and fuzzy control can improve the control performances effectively.

A dynamical system approach to task-adaptation in physical human–robot interaction

The goal of this work is to enable robots to intelligently and compliantly adapt their motions to the intention of a human during physical Human–Robot Interaction in a multi-task setting. We employ a class of parameterized dynamical systems that allows for smooth and adaptive transitions between encoded tasks. To comply with human intention, we propose a mechanism that adapts generated motions (i.e., the desired velocity) to those intended by the human user (i.e., the real velocity) thereby switching to the most similar task. We provide a rigorous analytical evaluation of our method in terms of stability, convergence, and optimality yielding an interaction behavior which is safe and intuitive for the human. We investigate our method through experimental evaluations ranging in different setups: a 3-DoF haptic device, a 7-DoF manipulator and a mobile platform.

Detection of Nuclear Sources by UAV Teleoperation Using a Visuo-Haptic Augmented Reality Interface.

A visuo-haptic augmented reality (VHAR) interface is presented enabling an operator to teleoperate an unmanned aerial vehicle (UAV) equipped with a custom CdZnTe-based spectroscopic gamma-ray detector in outdoor environments. The task is to localize nuclear radiation sources, whose location is unknown to the user, without the close exposure of the operator. The developed detector also enables identification of the localized nuclear sources. The aim of the VHAR interface is to increase the situation awareness of the operator. The user teleoperates the UAV using a 3DOF haptic device that provides an attractive force feedback around the location of the most intense detected radiation source. Moreover, a fixed camera on the ground observes the environment where the UAV is flying. A 3D augmented reality scene is displayed on a computer screen accessible to the operator. Multiple types of graphical overlays are shown, including sensor data acquired by the nuclear radiation detector, a virtual cursor that tracks the UAV and geographical information, such as buildings. Experiments performed in a real environment are reported using an intense nuclear source.

A Multi-Finger Interface with MR Actuators for Haptic Applications.

Haptic devices with multi-finger input are highly desirable in providing realistic and natural feelings when interacting with the remote or virtual environment. Compared with the conventional actuators, MR (Magneto-rheological) actuators are preferable options in haptics because of larger passive torque and torque-volume ratios. Among the existing haptic MR actuators, most of them are still bulky and heavy. If they were smaller and lighter, they would become more suitable for haptics. In this paper, a small-scale yet powerful MR actuator was designed to build a multi-finger interface for the 6 DOF haptic device. The compact structure was achieved by adopting the multi-disc configuration. Based on this configuration, the MR actuator can generate the maximum torque of 480 N.mm with dimensions of only 36 mm diameter and 18 mm height. Performance evaluation showed that it can exhibit a relatively high dynamic range and good response characteristics when compared with some other haptic MR actuators. The multi-finger interface is equipped with three MR actuators and can provide up to 8 N passive force to the thumb, index and middle fingers, respectively. An application example was used to demonstrate the effectiveness and potential of this new MR actuator based interface.

Penalty-based haptic rendering technique on medicinal healthy dental detection

We present a penalty-based haptic rendering analysis method for medicinal dentistry diagnose simulation. The method is based on the locally optimized generalized penetration computation algorithm which computes the minimum translational and rotational motion to separate two overlapping objects. The essence of penalty-based haptic rendering method is computing an amount of penetration depth, and the output force magnitude is following the Hooke's law. We use the virtual coupling method to calculate the output force and analysis the damping and stiffness coefficient in order to get a rendering force which optimizes the haptic feedback value and resolves the instability problems in haptic rendering system. Furthermore, we introduce friction force on different surface textures of the interacting objects. And successfully mapped the virtual contact results to force feedback and integrated the algorithm into the off-the-shelf 6Dof haptic device. The experiment result shows that our method can generate stable and realistic haptic feedback in dentistry diagnose simulation near ideal update rate.

Data analysis on virtual stiffness in 6DoFs haptic rendering system

We present an optimization analysis method for virtual stiffness in 6-DoFs haptic rendering system. The method is based on the locally optimized generalized penetration computation algorithm which computes the minimum translational and rotational motion to separate two overlapping objects. The essence of penalty-based haptic rendering method is computing an amount of penetration depth, and the output force magnitude is following the Hooke׳s law. We use the virtual coupling method to calculate the output force and analysis the damping and stiffness coefficient in order to get a rendering force which optimizes the haptic feedback value in haptic rendering system. We mapped the virtual contact results to the feedback force and torque, and successfully integrated the algorithm into the off-the-shelf 6Dof haptic device. Our rendering algorithm can handle highly complexity polygon models and make no assumption about the underlying geometry topology. The experiment result shows the optimization analysis method can generate stable and realistic haptic feedback.

Development of a Haptic Interface for Natural Orifice Translumenal Endoscopic Surgery Simulation.

Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, which utilizes the body's natural orifices to gain access to the peritoneal cavity. The NOTES procedure is designed to minimize external scarring and patient trauma, however flexible endoscopy based pure NOTES procedures require critical scope handling skills. The delicate nature of the NOTES procedure requires extensive training. Thus, to improve access to training while reducing risk to patients, we have designed and developed the VTEST, a virtual reality NOTES simulator. As part of the simulator, a novel decoupled 2-DOF haptic device was developed to provide realistic force feedback to the user in training. A series of experiments were performed to determine the behavioral characteristics of the device. The device was found capable of rendering up to 5.62N and 0.190Nm of continuous force and torque in the translational and rotational DOF, respectively. The device possesses 18.1 and 5.7Hz of force bandwidth in the translational and rotational DOF, respectively. A feedforward friction compensator was also successfully implemented to minimize the negative impact of friction during the interaction with the device. In this work, we have presented the detailed development and evaluation of the haptic device for the VTEST.

RETRACTED: Graphic and haptic simulation for transvaginal cholecystectomy training in NOTES

Natural Orifice Transluminal Endoscopic Surgery (NOTES) provides an emerging surgical technique which usually needs a long learning curve for surgeons. Virtual reality (VR) medical simulators with vision and haptic feedback can usually offer an efficient and cost-effective alternative without risk to the traditional training approaches. Under this motivation, we developed the first virtual reality simulator for transvaginal cholecystectomy in NOTES (VTEST™). This VR-based surgical simulator aims to simulate the hybrid NOTES of cholecystectomy. We use a 6DOF haptic device and a tracking sensor to construct the core hardware component of simulator. For software, an innovative approach based on the inner-spheres is presented to deform the organs in real time. To handle the frequent collision between soft tissue and surgical instruments, an adaptive collision detection method based on GPU is designed and implemented. To give a realistic visual performance of gallbladder fat tissue removal by cautery hook, a multi-layer hexahedral model is presented to simulate the electric dissection of fat tissue. From the experimental results, trainees can operate in real time with high degree of stability and fidelity. A preliminary study was also performed to evaluate the realism and the usefulness of this hybrid NOTES simulator. This prototyped simulation system has been verified by surgeons through a pilot study. Some items of its visual performance and the utility were rated fairly high by the participants during testing. It exhibits the potential to improve the surgical skills of trainee and effectively shorten their learning curve.

人工指による触知覚解析に基づく硬軟感および摩擦感推定法

To achieve more realistic haptic rendering, it requires the haptic modeling based on the haptic sensing and analyzing of the physical phenomenon which occur between objects in the real world and requires the control of haptic device at real-time. In the field of the robotics, bilateral control is used to transmit the haptic information between multipoint. In our previous work, we developed a friction sensing and rendering system based on the bilateral control with ONE 3DOF haptic device. However, it was difficult to measure and represent the haptic perception with human finger. Therefore, we propose an estimate method of the haptic perception such as the hardness and friction of the target object based on the bilateral control with ONE 3DOF haptic device and an artificial finger.

An Optimization Approach Toward a Robust Design of Six Degrees of Freedom Haptic Devices

This work presents an optimization approach for the robust design of six degrees of freedom (DOF) haptic devices. Our objective is to find the optimal values for a set of design parameters that maximize the kinematic, dynamic, and kinetostatic performances of a 6-DOF haptic device while minimizing its sensitivity to variations in manufacturing tolerances. Because performance indices differ in magnitude, the formulation of an objective function for multicriteria performance requirements is complex. A new approach based on Monte Carlo simulation (MCS) was used to find the extreme values (minimum and maximum) of the performance indices to enable normalization of these indices. The optimization approach presented here is formulated as a methodology in which a hybrid design-optimization approach, combining genetic algorithm (GA) and MCS, is first used. This new approach can find the numerical values of the design parameters that are both optimal and robust (i.e., less sensitive to variation and thus to uncertainties in the design parameters). In the following step, with design optimization, a set of optimum tolerances is determined that minimizes manufacturing cost and also satisfies the allowed variations in the performance indices. The presented approach can thus enable the designer to evaluate trade-offs between allowed performance variations and tolerances cost.

Haptic rendering method based on generalized penetration depth computation

We present a new haptic iterative technology of 6-DoF haptic rendering based on the generalized penetration computation method. Generalized penetration depth is the minimum translational and rotational motion to separate two overlapping rigid objects; we used an iterative, local optimization method to approximate generalized penetration depth, and map the computation results to compute the virtual contact haptic feedback, force and torque. We successfully integrated the algorithm into an off-the-shelf 6-DoF haptic device (Phantom Premium). Our rendering algorithm can handle highly complex polygon models and make no assumption about the underlying geometry and topology. In order to resolve the instability problems, we use an optimization method to decrease the subtle rotation motion and think about the feedback force direction in the physical environment. The experimental result shows that our rendering method can generate stable and realistic haptic feedback.

Jacobian Matrix Normalization - A Comparison of Different Approaches in the Context of Multi-Objective Optimization of 6-DOF Haptic Devices

This paper focuses on Jacobian matrix normalization and the performance effects of using different criterion and techniques. Normalization of the Jacobian matrix becomes an issue when using kinematic performance indices and the matrix contains elements with non-homogenous physical units, i.e. representing both translational and rotational motions. Normalization is necessary in multi objective optimization if kinematic performance indices are used based on the full Jacobian matrix. Different methods have been proposed in literature for defining a scaling factor used to normalize the Jacobian. Based on a comparison of a few of these methods, we conclude that it is better to have the scaling factor as a design variable in the multi objective optimization. However, as an alternative, a new scaling factor is proposed based on the relationship between linear actuator motion range in joint space and rotational end effector motion in task space, a proposal underpinned by simulation, analysis and comparison of optimization results using existing normalization techniques. For optimization, performance indices for workspace, kinematic sensitivity, device isotropy and inertia are considered. To deal with the multi-objective optimization problem, genetic algorithms are employed together with a normalized multi-objective optimization function. The performances of different device configurations (depending on the normalization method and the global isotropy index used) are presented in this article.

Partial dynamic balancing of a 6-DOF haptic device

This article presents the partial dynamic balancing of a 6-DOF (degree of freedom) haptic device. At first, the motion of the 3-DOF rotational part is decoupled with the motion of the 3-DOF translational part, because the former has no effect on the baseplate, so it can be considered as a whole and only discusses the 3-DOF translational part in the process of calculating dynamic balancing. The main feature of this mechanism is that the system is symmetric about the Cartesian coordinate, so the dynamic balancing of the 3-DOF translational part can be simplified to the dynamic balancing of 1-DOF translational part. The conditions of shaking force balancing can be obtained by keeping the linear momentum constant, and the conditions of shaking moment balancing can be get by minimizing the rate of the angular momentum. Finally, simulation examples are given to verify that the centre of mass of the partial dynamically balanced mechanism is fixed, and the global reaction forces on the baseplate are zero, and the global reaction moments on the baseplate decrease about five times at all times and for arbitrary trajectories.