Towards Point-Based Haptic Interactions With Deformable Objects

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.

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.

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

Haptic interactions have become increasingly important as an interface to computer-generated simulations in virtual-reality (VR) applications. Many haptic devices are designed to be used as a force feedback mouse, where the user's hand is in contact with the haptic device while the object contact and force generation occur on a computer screen. In this paper, we present an approach using a “virtual probe” to interact with the environment and introduce a new method to generate impedance-based haptic forces based on the use of a virtual manipulator. The virtual probe is connected directly to the haptic device and is projected from the hand to the environment, much like a scalpel or sword. As the probe comes in contact with the environment, the haptic device generates appropriate forces on the hand. We extend this approach to include underactuated haptic devices, which do not have fully powered joints. We show that the approach compensates for missing joint actuation in the underactuated haptic devices. We show experimental results for a simple case of haptic interaction; we also present an experimental implementation in six degrees of freedom (DOF) using one of the most popular devices: the PHANTOM.

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.

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.

One of the major concepts in business analytics is to identify the anomalies over time, also called as trend analysis. This can be easily done in pivot tables by using time as one of the dimensions, usually across columns. However, the trending information itself is insufficient to make any quick and insightful observations. Ranking the time series to identify the similar units of information can accelerate the analysis process. Similarly projection of the time series to the future will help the decision maker to proactively build alternate plans for differing scenarios. For doing such an analysis and modeling it becomes necessary to have aggregated data on demand. Current breed of row store database have limited capabilities to provide the response time required for such an analysis and modeling. Hence, column store database are expected to be better alternatives, for these types of problems. In this work the attempts made by the authors to develop such a system named as 'rePivot' are presented. The proposed frame work consists of three modules namely - a column store database to provide quick access to data, a time series ranking module and a probabilistic forecasting module. A case study of the proposed frame work in churn analysis and modeling in telecom has been carried out to test the suitability of framework for industrial applications. Application of the framework has shown promising results. Work is under progress to develop additional modules for survival analytics of individual entities in the database.

This paper introduces networked tank gunnery skill training based on haptic interaction. “Hand in hand” training mode is implemented by constructing a networked haptic display system. A teacher and a trainee can respectively manipulate his own haptic device to realize skill transferring. In this process, the trainee can experience the teacher's motor skill and can be corrected by the teacher. A local network is built to connect two haptic devices and computers. Two modes for tank gunnery skill training are designed in this system: haptic guidance and real-time correction. A prototype system is established to testify the effectiveness of such a new type “Hand in hand” training system.

Multi-dimensional force sensor for haptic interaction: a review

In haptic interaction, friction caused by slip on the fingertip is a key factor for manual manipulation as well as exploration of texture and shape. From the moment of contact, the friction contains vertical and tangential skin deformations and vibrations, not all of which have been simultaneously supported by previous portable/wearable haptic devices. We propose a portable haptic device that has the ability to present skin deformation and vibration with two degrees of freedom by using two types of motors: a voice coil motor (VCM) for vertical motion and vibration, and direct current motors for tangential skin stretch. The VCM also achieves encounter-type haptic interactions. A combination of these motions encompasses most cutaneous cues for realistic friction.

Haptic-based tissue stiffness perception is essential for palpation training system, which can provide the surgeon haptic cues for improving the diagnostic abilities. However, current haptic devices, such as Geomagic Touch, fail to provide immersive and natural haptic interaction in virtual surgery due to the inherent mechanical friction, inertia, limited workspace and flawed haptic feedback. To tackle this issue, we design a novel magnetic levitation haptic device based on electromagnetic principles to augment the tissue stiffness perception in virtual environment. Users can naturally interact with the virtual tissue by tracking the motion of magnetic stylus using stereoscopic vision so that they can accurately sense the stiffness by the magnetic stylus, which moves in the magnetic field generated by our device. We propose the idea that the effective magnetic field (EMF) is closely related to the coil attitude for the first time. To fully harness the magnetic field and flexibly generate the specific magnetic field for obtaining required haptic perception, we adopt probability clouds to describe the requirement of interactive applications and put forward an algorithm to calculate the best coil attitude. Moreover, we design a control interface circuit and present a self-adaptive fuzzy proportion integration differentiation (PID) algorithm to precisely control the coil current. We evaluate our haptic device via a series of quantitative experiments which show the high consistency of the experimental and simulated magnetic flux density, the high accuracy (0.28 mm) of real-time 3D positioning and tracking of the magnetic stylus, the low power consumption of the adjustable coil configuration, and the tissue stiffness perception accuracy improvement by 2.38 percent with the self-adaptive fuzzy PID algorithm. We conduct a user study with 22 participants, and the results suggest most of the users can clearly and immersively perceive different tissue stiffness and easily detect the tissue abnormality. Experimental results demonstrate that our magnetic levitation haptic device can provide accurate tissue stiffness perception augmentation with natural and immersive haptic interaction.

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.

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

The well known property of haptic interaction is the high refresh rate of the haptic loop that is necessary for the stability of the interaction. Therefore, only simple computations can be done within the loop. On the other hand, physically-based deformation modeling requires heavy computations. Moreover, if realistic behavior is desired, the models are non-linear and iterative solution is necessary. In this paper, the technique for haptic interaction with non-linear complex model is presented. Our approach, based on approximations of configuration space, is described and the accuracy of the approximation is experimentally determined.

In multi‐modal interactions including haptics, problems such as input sensor noise, temporal mismatch between graphics and haptics, and non‐constant refresh rates may cause non‐smooth force/torque display. This paper proposes temporal smoothing technique for haptic interaction using a sensing glove in multi‐modal applications. The proposed technique employs two processes: (1) a noise reduction method is applied to reduce jitter noise at the sensors in the sensing glove and (2) an adaptive force extrapolation is applied for time‐varying haptic and video frame rates. To demonstrate the performance of the proposed method, we developed a test platform to assess a simple box model and relatively complex models such as gamephone, portable media player (PMP). It was subsequently demonstrated that the proposed method can support smooth haptic interactions in multi‐modal applications where a haptic device and a sensing glove are used. Copyright © 2009 John Wiley & Sons, Ltd.