Haptic Display System Research Articles

Effects of Physical Hardness on the Perception of Rendered Stiffness in an Encountered-Type Haptic Display.

Rendering stable hard surfaces is an important problem in haptics; current haptic devices cannot render hard objects and free space together. In our previous work, we addressed these limitations using an encountered-type haptic display system, which showed significant improvements compared to traditional rendering methods. In our approach, we attach a plate with the desired hardness to the kinesthetic device's end-effector, which the user interacts with using an untethered stylus. This method allows us to directly change the hardness of the end-effector based on the rendered object. In this paper, we evaluate how changing the hardness of the end-effector can mask the device's stiffness and affect the user's perception of the interaction. Our human subject experiment results indicate that when the end-effector is made of a hard material, it is difficult for users to perceive the stiffness change rendered by the device. On the other hand, this stiffness change is easily distinguished when the end-effector is made of a soft material. These results show promise for our combined hardness-stiffness display in avoiding the limitations of haptic devices when rendering hard surfaces.

Haptic Texture Rendering of 2D Image Based on Adaptive Fractional Differential Method

The fractional differential algorithm has a good effect on extracting image textures, but it is usually necessary to select an appropriate fractional differential order for textures of different scales, so we propose a novel approach for haptic texture rendering of two-dimensional (2D) images by using an adaptive fractional differential method. According to the fractional differential operator defined by the Grünvald–Letnikov derivative (G–L) and combined with the characteristics of human vision, we propose an adaptive fractional differential method based on the composite sub-band gradient vector of the sub-image obtained by wavelet decomposition of the image texture. We apply these extraction results to the haptic display system to reconstruct the three-dimensional (3D) texture force filed to render the texture surface of two-dimensional (2D) images. Based on this approach, we carry out the quantitative analysis of the haptic texture rendering of 2D images by using the multi-scale structural similarity (MS-SSIM) and image information entropy. Experimental results show that this method can extract the texture features well and achieve the best texture force file for 2D images.

Edge-Learning-Enabled Realistic Touch and Stable Communication for Remote Haptic Display

As the basis of Tactile Internet, remote haptic display has been made possible with the development of ultra-reliable low-latency communication in 5G. In this study, edge learning is employed to enable realistic haptic display and stable remote communication. We propose a double-loop control algorithm, which merges decoupling and PID neural network, for magnetic field generation of the electromagnetic haptic device. In addition, a supervised bidirectional LSTM network is constructed for online haptic prediction during remote interaction, thus complementing the missing haptic data on account of time delay and packet loss in network communications. Experiments have been conducted on the built remote haptic display system, where data streams from sensors are gathered, stored, and forwarded in real time. The results show that dynamic and accurate haptic display is achieved through our magnetic field control algorithm for the haptic device, and the error of haptic prediction by step is less than 0.01N. The conclusion is that the service sustainability of remote haptic display can be guaranteed by edge learning effectively.

Evaluation of string-based haptic display using an omnidirectional vehicle and a vacuum

In recent years, it is becoming possible to generate simple touch sensations toward virtual objects by using vibrotactile interfaces in a VR environment. However, they cannot render enough force and the direction of force is limited. In this paper, we propose a haptic display system that presents a static force in virtual space by using an omnidirectional vehicle and vacuum generator. A reaction force is generated in any direction by moving the vehicle to an appropriate position and fixing it to a floor surface.

Calibration and Evaluation for Visuo-haptic Collocation in Haptic Augmented Virtuality Systems

Haptic augmented virtuality systems can provide users with a highly immersive haptic experience by visuo-haptic collocation of physical objects with their corresponding virtual objects. The collocation can be accomplished by an encounter-type haptic display system where a robotic device provides a physical prop that represents a whole or partial virtual object in real-time and in the space occupied by the virtual object in the virtual environment. For efficient and accurate visuo-haptic collocation, this paper proposes a novel yet simple, efficient and accurate calibration method. The method employs a high-accuracy position device such as an industrial robot that can place physical objects quickly and accurately. The transformation between the reference frames of the real (robot) and virtual worlds is obtained by the simple motion of the robot’s end-effector equipped with a real object that is in turn tracked by a VR tracker system such as the HTC VIVE tracker. An evaluation of the proposed method indicates that it is possible to achieve acceptable accuracy with a few data points as compared to existing calibration methods that require a large number of data points.

Fault-Tolerant Control of a Class of Switched Nonlinear Systems With Structural Uncertainties

This brief considers fault-tolerant control of a class of uncertain switched nonlinear systems against partial actuator failures. This brief first presents a fault-tolerant control method by using the common Lyapunov function technique and then applies it to haptic display systems. Compared to the relevant literature results, this proposed method is: 1) invariant to actuator fault modes, in the sense that the proposed controllers are completely independent from the fault modes, and 2) independent of switching policies under certain conditions. Simulation studies on a practical haptic display system with switched virtual environments are carried out to demonstrate the effectiveness of the proposed method.

Human Detection and Discrimination of Tactile Repeatability, Mechanical Backlash, and Temporal Delay in a Combined Tactile-Kinesthetic Haptic Display System

Many of the devices used in haptics research are over-engineered for the task and are designed with capabilities that go far beyond human perception levels. Designing devices that more closely match the limits of human perception will make them smaller, less expensive, and more useful. However, many device-centric perception thresholds have yet to be evaluated. To this end, three experiments were conducted, using one degree-of-freedom contact location feedback device in combination with a kinesthetic display, to provide a more explicit set of specifications for similar tactile-kinesthetic haptic devices. The first of these experiments evaluated the ability of humans to repeatedly localize tactile cues across the fingerpad. Subjects could localize cues to within 1.3 mm and showed bias toward the center of the fingerpad. The second experiment evaluated the minimum perceptible difference of backlash at the tactile element. Subjects were able to discriminate device backlash in excess of 0.46 mm on low-curvature models and 0.93 mm on high-curvature models. The last experiment evaluated the minimum perceptible difference of system delay between user action and device reaction. Subjects were able to discriminate delays in excess of 61 ms. The results from these studies can serve as the maximum (i.e., most demanding) device specifications for most tactile-kinesthetic haptic systems.

Fault-tolerant control of a class of switched systems with strong structural uncertainties with application to haptic display systems

This paper presents a robust fault-tolerant control method for a class of uncertain switched systems with strong structural uncertainties and applied it to haptic display systems. The proposed controller can stabilize the switched systems containing strong uncertainties with actuator faults and its nominal systems (i.e., without actuator faults) without necessarily changing any structures and/or parameters of the proposed controllers, and treats faulty and healthy actuators in a unified way. The proposed method is independent of arbitrary switching laws. A practical haptic display system with switched virtual environments shows the effectiveness of the proposed method.

A Method for Motion Abstraction Based on Haptic Information Directionality and an Application to Haptic Motion Display System

Robots working in the human environment have been researched in the field of motion control. For the next-generation robot, human and robot interaction technologies are needed. In particular, learning and displaying of human haptic motion are important. Therefore, the authors have proposed a method for abstracting haptic motion and designed a haptic motion display system. The motion abstraction method divides a measured motion to each action from the point of force and position. Then, action modes have been defined for expressing each divided action. Action modes are expressing force directionality or position directionality. By utilizing the proposed motion abstraction method, various kinds of human motion are abstracted as action modes. The designed haptic motion display system is trying to show these various kinds of human motion. This paper defines human action modes and environmental action modes from action modes. Human action modes are expressing human action force directionality, while environmental action modes are expressing environmental position response directionality. Furthermore, the haptic motion display system is redesigned. This system is redesigned based on human action modes and environmental action modes. The validity of the proposed method is confirmed by the experimental results.

The Proactive Desk: A New Haptic Display System for a Digital Desk Using a 2-DOF Linear Induction Motor

The Proactive Desk is a new digital desk with haptic feedback. The concept of a digital desk was proposed by Wellner in 1991 for the first time. A typical digital desk enables a user to seamlessly handle both digital and physical objects on the desk with a common GUI standard. The user, however, handles them as virtual GUI objects. Our Proactive Desk allows the user to handle both digital and physical objects on a digital desk with a realistic feeling. In the Proactive Desk, two linear induction motors are equipped to generate an omnidirectional translational force on the user's hand or on a physical object on the desk without any mechanical links or wires, thereby preserving the advantages of the digital desk. In this article, we first discuss applications of a digital desk with haptic feedback; then we mention the design and structure of the first trial Proactive Desk, and its performance.

WEARABLE HAPTIC DISPLAY FOR IMMERSIVE VIRTUAL ENVIRONMENT

Recently a number of immersive displays that project virtual environment on large-sized screens have been developed. In applications of virtual reality technology for such large immersiveenvironments, it is important to develop some haptic display that gives a real feedback sensation such as forceor tactile to users from the virtual environment. Especially, it is necessary to develop small, light and safety actuators for the wearable haptic display. In this paper, the haptic display system using pneumatics for theimmersive virtual environment is proposed and developed. The system consists of a tactile and a force reflecting type wearable haptic displays using pneumatic pressure control. Experiments for grasping virtual objects in the virtual environment are performed by the wearable haptic displays using pneumatic actuators. It is experimentally verified that the performance of the haptic display system is effective to touch and grasp the virtual objects.

A Study on the Accuracy of Haptic Display System for NURBS Surface

A Study on the Accuracy of Haptic Display System for NURBS Surface