In virtual environments, spatial discrepancies between visual and haptic scenes negatively impact user performance and experience. This paper shows how spatial discrepancies due to pose differences can occur in a haptic augmented virtuality system with an encountered-type haptic display. To mitigate this problem, we propose visual guidance, an algorithm that dynamically manipulates the visual scene to compensate for discrepancies. The effectiveness of this algorithm was verified in a pair of studies involving a button pressing task and spatial discrepancies between ±150 mm and ±40°. Experimental results show that discrepant trials using the technique yield error rates and a number of speed peaks (representing the number of targeting movements) that are comparable to those attained in trials with zero spatial discrepancy. This result was also achieved without requiring a dedicated adaptation or training process, ensuring the algorithm can be used immediately by users. A pair of follow-up studies also indicates the algorithm has little impact on subjective ratings of simulator sickness, suggesting that sporadic use of the algorithm will not negatively affect user's experience of a virtual environment. We believe that the visual guidance algorithm presented in this paper can be used to create more useful and compelling experiences in various haptic training applications incorporating encountered-type haptic displays.

This paper presents a comprehensive study of the impact of visual-haptic spatial discrepancies on human performance in a targeting task conducted in a visual-haptic virtual and augmented environment. Moreover, it explores whether the impact of this effect varies with two additional variables: 1) haptic wall stiffness and 2) visual cursor diameter. Finally, we discuss the relative dominance of visual and haptic cues during a targeting task. The results indicate that while the spatial discrepancies studied exerted a small effect on the time required to perform targeting, they impacted the absolute errors considerably. Additionally, we report that haptic wall stiffness has a significant effect on absolute errors while the visual cursor diameter has a significant effect on movement time. Finally, we conclude that while both visual and haptic cues are important during targeting tasks, haptic cues played a more dominant role than visual cues. The results of this paper can be used to predict how human targeting performance will vary between systems, such as those using haptically enabled virtual reality or augmented reality technologies that feature visual-haptic spatial discrepancies.

This paper proposes a position and stiffness bounding approach (PSBA) for improving “geometry transparency” in time-delayed teleoperations. The proposed method can rapidly update the local model location in master site to the contact location in the slave site. The proposed PSBA can therefore avoid instability problem due to both discrete force controller and sudden contact location changes (so called “model jump effect”). Effectiveness of the proposed approach is shown by 1-DOF simple contact experiment in 500ms round trip time delayed virtual environment.

With rapid developments in virtual reality (VR), haptics, communications technology and digital multimedia, there has been increasing demand for creation and widespread development of more realistic or immersive display systems. Consumers are eager to experience engrossing contents capable of providing presence, beyond traditional audio-visual media. In response to this demand, tactile and haptic interaction is also becoming increasingly important. Recently, MPEG-V standard (ISO/IEC 23005) has been published. The MPEG-V provides architecture and metadata for interaction and interoperability between virtual worlds and real worlds through various sensors and actuators. The aim of this paper is to provide an overview of MPEG-V standard, particularly regarding haptic and tactile interactions.

This paper presents the convex hull-based power manipulability analysis of robot manipulators. Since the manipulability analysis is essential for the design and performance evaluation of robot manipulators, many researchers have focused on the well-known manipulability ellipsoid and polytope based on the Jacobian analysis to investigate the corresponding information. In spite of the good reputation of the manipulability ellipsoid, it does not provide the adequate information about how fast the manipulators can move along arbitrary direction, and the manipulability polytope also suffers from a physical inconsistency which arise when position and orientation information are combined into a single scalar performance parameter. To overcome the drawback of the physical inconsistency, the power manipulability ellipsoid has been suggested based on a new parameter which does not depend on the physical unit choice of mechanisms [1]. However, it still has the same drawback as the manipulability ellipsoid. Therefore, the purpose of this paper is to develop the convex hull-based power manipulability in order to provide the adequate information with the physical consistency. The proposed approach is applied to a 2-DOF serial manipulator and a 3-DOF planar parallel manipulator by comparing the ellipsoid approach and the polytope one.

This paper presents a preliminary study on a new vibrotactile rendering method which can make smoother directional vibrotactile flows on a thin plate. Both by actuating two piezoelectric actuators sequentially from one side to the opposite side and by controlling amplitude-modulated input excitation frequency from zero to the 1stmode of the resonant frequency of a thin plate, a user can feel a smoother directional vibrotactile flows on his/her palm as he/she touches the surface of the thin plate. Experimental results and a user study show that the proposed vibrotactile flow is smoother than the vibrotactile flow that can be generated by the traditional apparent tactile movement and phantom sensation generation methods. The smooth directional vibrotactile flow may be useful for identifying callers or give directional information in navigation maps in mobile devices.

Stability is a major requirement in haptic interaction since unstable behavior impairs realism and may injure the human operator. In this paper, we propose a force bounding approach by which a robustly stable haptic interaction is made possible for any (linear, nonlinear, delayed etc.) virtual environments. Based on the passivity condition for sampled-data haptic systems, a necessary and sufficient condition for the force that can be passively displayed is derived. It contains, however, memory effect due to the accumulation of past remaining dissipation. In order to avoid contact oscillations by the memory effect, a simple reset rule is applied. In addition, a braking pulse is combined with the force that is bounded by the proposed approach in order to increase initial contact realism for stiff environments. Experimental results are presented to verify that the proposed approach makes the haptic interaction passive and increases haptic realism.

This paper describes investigation on the effectiveness of the haptic feedback in science education, involving 8th grade middle school students. For that study haptically enhanced presentations of the Coriolis Effect have been created based on MPEG-4 framework allowing creating, transmitting and displaying haptically enhanced multimedia educational contents. A special focus of the work is the comparison of the effect of different modalities - i.e. audiovisual feedback only, audiovisual feedback with tactile feedback and audiovisual feedback with kinesthetic feedback - on the learning. The result showed that multimedia contents including haptic feedback can improve student understanding of the Coriolis Effect better than when only the audiovisual feedback content was provided. However, there was no significant difference between tactile and kinesthetic modalities.

This paper presents a frequency-dependent digital damping referred to a digital input shaper (DIS). Compared to the previously proposed analog input shaper, the DIS makes the implementation of damping much more flexible and significantly reduces the electrical noise. Moreover, the DIS can incorporate position control at the initial contact with virtual objects to improve the perceived contact hardness. Through benchmark virtual wall experiments, we show that the DIS can significantly increase the impedance range that a haptic interface can stably display, and that the initial contact hardness that a user perceives can be noticeably improved by using the proposed position control method.

This paper presents an energy-bounding approach to a rate-mode bilateral control of remote vehicles in order to guarantee the system stability in constant time-delayed telecommunication environments. The velocity error between desired and actual remote vehicle velocities is reflected in term of force in order to maintain desired velocities by the operator both during the normal driving in obstacle-free environments and when colliding with a high impedance wall. A rate-mode energy-bounding algorithm is devised for these teleoperation scenarios in order to sensitively feel the velocity difference while keeping interaction stability. Effectiveness of the proposed approach is shown by some experimental results in the simulated constant time-delayed environments for vehicles not only in free space but also in contact motions.

Abstract 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.

This paper analyzes the passivity and transparency of teleoperation systems in the presence of data delays and signal attenuations. To ensure the passivity and perfect transparency of such network systems, this paper makes use of the concept of lossy transmission line. Utilizing the concept of transmission line enables us to intuitively understand the characteristics of lossy network and allows us to consider the data delays and data dropout issues simultaneously. Thus, the key contribution of this paper is to propose of using transmission line concepts to ensure both the passivity and transparency of teleoperation systems with delays and data loss. Through numerical simulations using PSPICE, the validity of the proposed analysis is evaluated.

In this paper, we propose the UbiFloorII, a novel floor-based user identification system to recognize humans based on their stepping pattern, the arrays of the transitional footprints from heel-strike to toe-off. To obtain users' stepping pattern from their gait, we deployed photo interrupter sensors instead of switch sensors used in the UbiFloorI. We developed a software module to extract stepping pattern from users' gait. For user identification, we employed neural network trained with users' stepping samples. We achieved about 92% recognition accuracy using this floor-based approach. The UbiFloorII system may be used to automatically and transparently identify users in a home environment.

An objective of this research is to optimize the designing parameters of a 6-DOF parallel manipulator required the large workspace for the sophisticated and complicated work on the basis of mechanism's compactness. The method uses a genetic algorithm with respect to the maximization of tranlational/rotational workspaces and isotropy of mechanism to obtain the optimal linkage parameters. It is studied for fifteen cases which are divided by combination of translational and rotational workspaces corresponding to the range of translational motion and tilt angle of the end-effector. To decide the best model in the total optimized cases, compactness of mechanism, translational workspace, rotational workspace on the boundary of translational workspace, and global conditioning index (GCI) as kinematic performances, and then kinematic performances of best model are verified by comparing to those of the preexisting model

This paper presents a preliminary test's results for bilateral teleoperation using the energy bounding algorithm that is already proposed for stable haptic interaction control. The preliminary experimental results show that the energy bounding algorithm may generate stable bilateral teleoperation regardless of the amount of constant/variable time delay. The test results are qualitatively compared with the other existing results.

This paper presents kinematic calibration of parallel manipulators with partial pose measurements, using a device that measures a rotation of the end-effect or along with its position. The device contains a linear variable differential transformer, a biaxial inclinometer, and a rotary sensor. The device is designed in a modular fashion, and links of different lengths can be used. Two additional kinematic parameters required for the measurement device are discussed, kinematic relations are derived, and cost function is established to perform calibration with the proposed device. The study is performed for a six-degree-of-freedom fully parallel HexaSlide mechanism (HSM). Experimental results show significant improvement in the accuracy of the HSM.

This paper presents a novel reconfigurable ankle rehabilitation robot to cover various rehabilitation exercise modes. The designed robot can allow desired ankle and foot motions including toe and heel raising as well as traditional ankle rotations since the mechanism can generate relative rotation between the fore and rear platforms as well as pitch and roll motions. In addition, the robotic device can be reconfigured from a range of motion (ROM)/strengthening exercise device to a balance/proprioception exercise device by simply incorporating additional plate. Further, the action of the device is two folded in the sense that while a patient’s foot is fastened firmly to the ROM/strengthening device for task specific training, s/he can also stand on the balance/proproception device. The suggested ankle rehabilitation robot is expected to substitute not only the traditional therapy in various exercise modes but also supply the advanced functional exercises.

This paper presents walking control of a novel omni-directional locomotion interface with a dual-planar parallel robot. The suggested interface can generate infinite floor on planar surfaces, allowing user's upright and turning walking motions. To provide continuous walking in a confined area, a walking control algorithm is suggested for planar surfaces. For continuous walking, each independent platform of the locomotion interface will follow a human foot during the swing phase, while the platforms will move back during single stance phase. For accurate foot tracking control, magnetic trackers are attached on each shoe with careful calibration and transition phases between the swing and the stance phases are detected by using switch system, which is composed of light steel plate, spring, and micro switch. For double limb support, two platforms will manipulate neutral positions to compensate the offset errors generated by velocity change. This algorithm can satisfy natural walking conditions for any directions of planar surfaces. From experimental results, a subject can walk naturally for upright motions without significant limitations, while limitations of maximum yaw angle of 20/spl deg/ are applied to each platform to prevent the collisions of two platforms during turning motions. By using the suggested interface, it is anticipated that a user can interact with virtual normal pathways by real walking including upright and turning motions.

Stability is one of the important considerations in the design and control of haptic simulation systems because unstable behavior may cause damage on human operator or deterioration of realistic haptic feeling. In this paper, a basic theory on the passivity condition for the sampled-data system has been reviewed and energy relations on each subsystem of haptic simulation have been investigated. Based on this, we propose a novel energy bounding algorithm for stable haptic interaction control. The proposed energy bounding algorithm restricts the energy that is generated by the sample and holds within the energy consumable by the physical damping in a haptic device and makes the virtual environment and controller passive as well. This algorithm, therefore, guarantees the passivity condition of the haptic simulation regardless of sampling frequency. Experimental validation with a commercial haptic device has been presented.

Development of optimal design methods for parallel manipulators is important in obtaining an optimal architecture or pose for the best kinetostatic performance. The use of performance indexes such as the condition number of the conventional Jacobian matrix that is composed of nonhomogeneous physical units, however, may lack in physical significance. In order to avoid the unit inconsistency problem in the conventional Jacobian matrix, we present a new formulation of a dimensionally homogeneous Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points that are coplanar with the mobile platform joints. The condition number of the new Jacobian matrix is then used to design an optimal architecture or pose of parallel manipulators for the best dexterity. An illustrative design example with a six-degree-of-freedom Gough-Stewart platform parallel manipulator by using the proposed formulation is shown to generate the same optimal configurations as those from using the other existing dimensionally homogenous Jacobian formulation methods.

Kinematic calibration is a process whereby the actual values of geometric parameters are estimated so as to minimize the error in absolute positioning. Fully autonomous methods of calibration are cost effective, fast and easy to implement. The paper presents a fully autonomous calibration technique that can be applied to a 6 degree-of-freedom fully parallel Hexa Slide manipulator. The main idea is to lock the mobile platform at a specific point with a device so that the platform has only 3 degrees of freedom, i.e. rotations about the locked point. The measurement data, however, is collected from six actuator sensors. This redundancy of sensory information is utilized for calibrating geometric parameters. Simulations show that the presented technique is the most effective with large range of orientation angles.

Development of optimal design methods for general 6 degree-of-freedom parallel manipulators is important in obtaining an optimal architecture or pose for the best kinematic performance. Use of a performance index such as the condition number of the Jacobian matrix that is composed of nonhomogeneous physical units may lack physical significance. In order to avoid unit mismatch in the Jacobian matrix, the paper presents a new Jacobian formulation by use of three point generalized coordinates, which results in a (9/spl times/9) dimensionally homogeneous Jacobian matrix. The condition number of the new Jacobian matrix is used to design an optimal architecture or pose of parallel manipulators for best dexterity. A design example with a Gough-Stewart platform parallel manipulator by using the proposed formulation is shown to generate the same optimal configuration as from using the other Jacobian formulation methods.

Presents a design optimization method of parallel manipulators for best accuracy. An accurate kinematic error model that relates every structural error source in the manipulator's structure to end-effector pose errors is derived for a HexaSlide type parallel manipulator. Based on the error model, a measure of accuracy, error amplification factor, is introduced for an optimum design formulation with constraints on workspace and design variable limits. Then, design optimization for best accuracy has been performed by using a nonlinear optimization technique. Optimization results have been validated by Monte Carlo statistical simulation technique. The optimized design shows smaller error than the initial design.

This paper presents a new closed-form solution of the direct kinematic problem of nearly general parallel manipulators by using three linear extra sensors. The sensors are disposed at optimal location, connecting the planar base and the planar mobile platform at distinct points. The basic idea is to use the coordinates of the three distinct anchor points of the extra sensors on the mobile platform to represent the pose of the mobile platform. Thus, the extra sensory data enable one to reduce the problem to the solution of a system of six linear equations in six of the nine generalized coordinates. The other three coordinates are obtained directly from the extra sensory data. In addition, an optimal location of the extra sensors is sought by minimizing the condition number of the linear equations for the least sensitivity to sensor measurement errors. A numerical example is presented for optimal sensor location and the error behavior of the proposed solution scheme by computer simulation.

Presents the design and analysis of a 6 degree-of-freedom new haptic device for interfacing with virtual reality by using a parallel mechanism. The mechanism is composed of three pantograph mechanisms that are driven by ground-fixed servomotors and stand perpendicularly to the base plate, three spherical joints between the top of the pantograph mechanisms and connecting bars, and three revolute joints between connecting bars and a mobile joystick handle. Forward and inverse kinematic analyses have been performed and the Jacobian matrix is derived. Performance indices such as GPI (global payload index), GCI (global conditioning index), translation and orientation workspaces, and sensitivity are evaluated to find optimal parameters in the design stage. The proposed haptic mechanism has better load capability than those of pre-existing haptic mechanisms due to the fact that motors are fixed at the base. It has also wider orientation workspace mainly due to a RRR type spherical joint.

Presents the control and evaluation of a haptic device with a 6-DOF parallel mechanism for interfacing with virtual reality. This haptic device has low inertia, high bandwidth, and high output force capability mainly because of base-fixed motors. In addition, it has large orientation workspace due to RRR type spherical joints. A control method is presented with gravity compensation and with force feedback by a F/T sensor to compensate for the effects of unmodeled dynamics such as friction and inertia. Also, dynamic performance has been evaluated for force characteristics such as maximum applicable force, static-friction force, minimum controllable force, and force bandwidth by experiments. Virtual wall simulation with the developed haptic device has been demonstrated.

Describes a virtual environment for developing automotive electronic power steering (EPS) and steer-by-wire (SBW) systems. In this virtual environment, a feedback uniaxial dynamic rack force for the EPS system or a steering column feedback torque for the SBW system is applied physically to the EPS or SBW hardware by a pneumatic or electric actuator. A command signal for the actuator is generated from a virtual vehicle handling dynamics model that is simulated in real time by a very fast digital signal processor. The inputs to the real-time vehicle dynamic simulation model are steering angles driven through a steering system by a driver. By a simple force-feedback experiment it is shown that the proposed virtual environment may be used as a useful development tool for EPS and SBW systems.