This paper introduces an approach for manipulating bodily self-consciousness, in particular, senses of body ownership and illusory self-touch by using a robotic/haptic technology. This study especially focuses on the rubber hand illusion (RHI). In the classic RHI paradigm, an invisible participant's hand and a visible fake rubber hand are manually stimulated by an experimenter. However, our approach, which is termed active self-touch, allows the participants to administrate the tactile stimulation with variable force feedback by using a robotic master-slave system. Three RHI experiments with active self-touch were performed to demonstrate the utility of the proposed approach for assessment of bodily self-consciousness. The embodiment of a fake hand was assessed with the classic RHI paradigm, and the RHI paradigm with somatic sensation was applied to examine the effect of variable force feedback on the sense of illusory self-touch. These experiments verified that active self-touch allows participants to experience the classic RHI. In addition, the results implied that the sense of illusory self-touch can be induced, even if force feedback is absent in the dynamic self-touch condition, and that illusory sensation is easily modulated by variable force feedback during quasi-static self-touch rather than during dynamic self-touch. These findings suggest that our proposed approach has the potential to reveal relationships between action/haptic perception and the sense of body ownership.

This paper reports a 2-DOF electrostatic actuator with all electrodes made with transparent materials. The actuator is composed of two plastic films, a stator film and a slider film. The two films are sectioned into four-by-four checkerboard patterns, whose squares include fine-pitched strip electrodes arranged in orthogonal directions. A pair of three-phase voltages drives the slider in open-loop, along any preset paths in the 2-D plane. A prototype was fabricated with etched indium tin oxides and screenprinted conductive polymers. With 500 V excitation, the prototype exerted 60 to 100 mN forces in eight directions, and the slider traveled along straight and circular paths within its operating range of 132 mm by 132 mm, at maximum speed of 240 mm/s. With the transparency, the actuator realizes collaboration of an actuated physical object and animated images, on surfaces of flat panel displays.

Our previous study has proposed a novel approach with a robotic/haptic technology to tactile rubber hand illusion (TRHI) paradigm in order to open new discussions about the manipulation of human body-parts ownership. The results demonstrated that the use of master-slave system can cause the TRHI, enabling a unique condition-active self-touch. As an advanced approach, this study examines the effect of force feedback on the TRHI under the active self-touch. We hypothesize that appropriate force feedback plays an important role to determine our body-parts ownership, people would not experience the TRHI if the force feedback from a fake hand largely differs from the contact force on a real hand. This paper, in particular, discusses how the force feedback affects the TRHI under the active self-touch by variously changing force rendering on the master device.

This paper proposes an application of piezoelectric elements as inductors for a resonant electrostatic induction motor. The stator and the slider of the motor are made of plastic films with fine pitched electrodes patterned onto them. The stator electrodes are connected to the three-phase voltage source, whereas the slider electrodes are connected to three piezoelectric elements. At resonant condition, the slider voltage is boosted and maximum thrust force is obtained. A working prototype was constructed and driven with a three-phase excitation voltage of 513 V0-p/13.86 kHz, and traveled at its steady speed of approximately 60 mm/s, in balance with the friction between the films.

This paper presents a new kind of climbing robots whose locomotion and adhesion are both realized by electrostatic force. Two crawler-type robots were prototyped. For both of the prototypes, high-power electrostatic film motors are installed. The slider of the electrostatic motor works as a crawling belt as well as an electrode for electroadhesion. The first prototype that has a rigid mechanical structure is light in weight (49 g) and thin in thickness (14 mm). It can climb on a vertical aluminum board with a speed up to 104 mm/s and horizontally pull a payload of about 3.2 N. The other prototype is equipped with a flexible mechanical structure that consists of a series of passive joints. By smoothly transitioning from a horizontal floor up to a slope, the robot demonstrated its capability to comply with complicated surfaces.

This paper describes the system development of an admittance-controlled 2-dof haptic device using electrostatic motors. The unique point of the device is that all components including the motors and sensors are fabricated using non ferromagnetic materials to realize operation in a strong magnetic field. The device consists of an operation handle, two electrostatic motor units and two optical force sensors, and is an improved version of our previous development. The new device has stiffer platforms, improved force sensors, and newly fabricated driving electronics. The employed electrostatic motor is one of the strongest electrostatic actuators and can generate thrust force of several newtons. To operate a motor unit, two three-phase signals are required and they have to be amplified to over 1 kV. In our previous development, the signals were amplified by six large commercial amplifiers, which was not practical enough considering the portability of the system. This work developed an original driving electronics for the motor using Field Programmable Gate Array (FPGA) and step-up transformers to reduce the system size. The device was implemented on one of the major haptic toolkits, CHAI 3D. To be able to run sample impedance-type programs without any modifications, we implemented our device to behave like impedance-type on CHAI 3D.

This paper introduces a novel approach to the manipulation of body-parts ownership, using the tactile rubber hand illusion (RHI) paradigm. In the conventional studies on the RHI, participant's invisible hand and the visible rubber hand are manually tapped or stroked by an experimenter. Differently, in our approach, a bilateral master-slave system is applied to provide tactile stimulations in a novel interactive manner—active self-touch. Here, we present a 3-DOF master-slave system based on human self-touch characteristics and a validation experiment using an arranged version of the conventional RHI paradigm. In this new version, participants can contact with the rubber hand by manipulating the master device with their right hand and actively touch their own left hand through the slave device. The results demonstrate that the master-slave system can be successfully used to manipulate body-parts ownership, opening up the way to new studies concerning self-touch and body representation.

This paper presents a 2-DOF controlled softness display and its application to a tactile tele-presentation system. It has been reported that softness feelings can be displayed by reproducing contact area, or contact width, on a fingertip. Several softness displays based on the contact area control have been reported in past studies, but all of them had only one degree-of-freedom (DOF) for their contact area control. Resultantly, the reproduced contact area was symmetric, which could only produce uniform surface feelings. In some practical deformable surfaces, however, the contact conditions are not uniform over fingertip surfaces; for example, if there is a small lump beneath a soft deformable surface, resultant contact area can become asymmetric. To reproduce such asymmetric contact conditions, a softness display should have more controlled DOFs. This paper reports our trial to realize a multi-DOF controlled softness display. As a first step, this particular paper describes a 2-DOF controlled display. The display has two DC motors which independently control both sides of the contact area. Resultant asymmetric contact area can facilitate, e.g., discrimination of lump location in soft deformable surfaces. The display was integrated into a tactile tele-presentation system together with a contact width sensor, which measures asymmetric contact condition. Using the tele-presentation system, discriminations of lump location are demonstrated.

Levitation systems allow delicate objects to be handled without contact by actively controlling a levitation force that suspends the object. A drawback of levitation systems for thin objects is that the lateral force can not be controlled actively and is much weaker than the levitation force. This is a problem for non-contact manipulation systems as the object may loose its alignment with the levitator (and drop) because of the inertial forces coming from the lateral accelerations. In earlier work, a solution was proposed using Tilt Control in which lateral accelerations are compensated by the levitation force by tilting both the object and the levitator. This concept has been verified in an experimental setup that was capable of tilting around only one axis. In this paper, a new and unique design is presented of a tilting actuator that is capable of rotating around two axis, so that full 3D-space manipulation is possible. A key aspect of the Tilt Control strategy is that the center of rotation is at the center of mass of the levitated object and, for the tilting actuator, this means that it should have a remote center of rotation. A spherical cap or dome-shaped structure supported by three ball bearings, is used as the fundamental principle for the tilting actuator design as it has a natural remote center. The design and realization of this tilting actuator are described in this paper and a pilot experiment was carried out in which the tilting actuator, with a magnetic levitator installed, was attached to a linear motor. The results showed successful tilting action as relative lateral motion of the levitated object were significantly reduced on two axis.

Currently, the concept of ergonomically designed workplace using 3D graphic mannequins is gaining wide acceptance among the design engineers. However, predicting the human operational feeling level (i.e., comfort or discomfort level) during an ergonomic analysis of a virtual work situation is still in immature level. The current study is an attempt in that direction. This paper presents an approach that estimates the degree of comfort or discomfort felt by an operator during a lever manipulation task by using limb anthropometric and kinematic data. In this study, a haptic lever has been developed that emulates a lock-ball type lever action. Experiments were carried out with healthy male subjects under two different torque characteristics of the haptic lever. Using multiple regression analysis it has been found that the subjects operational feeling level can be estimated by means of shoulder flexion-extension angle and manipulability measure.

Levitation techniques allow delicate objects, such as silicon wafers, to be manipulated without contact. In case of electrostatic and magnetic levitation, the object can be levitated by actively controlling the electric/magnetic field based on the measured air gap between the object and the levitator. Multiple degrees of freedom are controlled by several electric/magnetic actuators. For thin flat objects, the surface area is large enough for suspending the object in vertical direction, but the side surface is too small to realize active control for lateral motions. For stability, the levitation system relies on a passive lateral restoring force that will keep the object aligned with the levitator. The drawback of this passive force is that it is far weaker than the controlled suspension force. As a result, allowable accelerations in the horizontal plane have to be limited in a manipulation task to prevent loosing the object during motion. In this paper, a solution is proposed based on compensating the acceleration by Tilt Control. For both an electrostatic and a magnetic levitation system, the significant improvement of tolerance to lateral acceleration due to feedforward tilt control is presented. It is shown that not only for automated motion but also for human operated motion, the tilt control strategy is applicable. In the human operated motion, haptic technology such as the admittance control scheme, are used to realize satisfactory manipulation.

This paper describes the development of a 2-DOF electrostatic haptic joystick designed for neuroscience studies in an MRI/fMRI. The joystick is fabricated using non-magnetic materials and actuated by two high-power electrostatic motor units which produce various force fields in the horizontal plane. The electrostatic motor is a synchronous drive and thus the positioning of the joystick is achieved in an open-loop control. As for force sensing, a 2-DOF force sensor is developed using non-magnetic materials and optical fibers so as to measure interaction force with a user; hence, the haptic rendering is based on the admittance control scheme that respects the rule of force-in and position-out. The operation of both the actuators and force sensor respects non-magnetic principles. Thus, the haptic joystick into which these components are integrated is expected to have high MR compatibility, although the evaluation of the MR compatibility is beyond the scope of this paper. In this paper, the device performance is evaluated in the normal environment, which verifies the operation of the unique electrostatic haptic device.

This paper presents a tele-presentation system for tactile softness. Tactile softness was estimated at a remote site, which was then reproduced at a master site, by focusing on change of contact width between a fingertip and an object. To realize the tele-presentation system, a new contact width sensor was developed based on an optical principle. The sensor was designed to have a soft structure to resemble human fingers. The prototype sensor was evaluated for five different samples. The result showed that the sensor could discriminate five samples from the contact width variation, although one pair of samples showed only a slight difference. The tele-presentation system that integrates the developed contact width sensor and a newly designed softness display was developed and evaluated. The evaluation result showed that a user can discriminate softness of a remote object using this system, although the perceived softness feelings did not perfectly match the real feelings of the remote objects, which would be due to insufficient optimization of the contact width sensor. This would be improved by improving the sensor to have a similar dimensions and stiffness as real human fingers, which will be addressed in our future work.

In electrostatic levitation systems, thin flat objects, such as silicon wafers, can be levitated by controlling the electric field between object and an electrode pattern, depending on the measured gap between them. This allows to manipulate these objects without making physical contact. As the gap between object and electrodes is actively controlled, the system is fairly robust for accelerations perpendicular to the objects surface. However, the restoring force for any lateral disturbance is much lower, as it is not actively controlled. This restricts the allowable lateral accelerations and poses a serious limitation on practical implementation of electrostatic levitation system as a good non-contact object handler. In this paper, the allowable lateral accelerations are increased by tilting the electrodes and object during lateral acceleration. Experimental results show how with tilting control, a levitated aluminium disk always remains aligned with the electrodes, while without tilt control it oscillates around the central point.

This paper presents a project that aims at fabricating a biologically inspired robotic fish. The robotic fish is designed to be capable of propelling itself through oscillations of a flexible caudal fin, like a real underwater fish. In this paper, we describe the design features that underlie the operation of the robotic fish. These features include a unique actuator referred to as electrostatic film motor and a light and flexible power transmission system. The electrostatic film motor is made of two pieces of flexible printed circuit film and can be utilized as a new-type artificial muscle. The power transmission system permits reciprocating power to be converted to periodic oscillations and distributed to the caudal fin. Based on several design considerations inspired by biological concepts, we propose several open-loop swimming control strategies for the constructed robotic fish to accomplish fish-like motion (i.e., cruising, turning, and diving). Experiments of Seidengyo I, the first prototype of our electrostatic fish family, are carried out to confirm the validity of the original design and control. We further design Seidengyo II to improve on Seidengyo I and show the results of the experiments.

This paper focuses on a practical application of handling contact sensitive objects such as silicon wafers or hard disk media without any contact using electrostatic levitation. Stable electrostatic levitation can be realized by controlling an electrostatic force on the basis of measured suspension air gaps. Two control approaches, namely centralized and decentralized control and the influence of an integrator in the controller, are discussed with regard to the specific tasks of Pick Up and Place. The final goal is to realize a handling tool that allows human operators to perform these object handling tasks. In this paper a linear motor is used to perform the pick up and place task to allow a controllable and reproducible motion. The experimental results show a stable pick up and place motion, where placing is realized without any external control commands.

This paper describes a voltage-induction type electrostatic film motor that operates by feeding electric power to the slider by electrostatic induction. In electrostatic film motors, feeding power to slider is important for better output capability and positioning performance. However, the power feeding using electric cables sometimes cause mechanical disturbance to the motor motions. In the new electrostatic motor, the power to the slider is fed by electrostatic induction, thus removing electric cables that can cause mechanical disturbances. The proposed motor has a two-phase electrode in the slider and a four-phase electrode in the stator. In addition, both stator and slider have the induction electrodes so that electric power is transferred to the slider through the induction electrodes. The paper first analyzes the thrust force characteristics of the proposed driving-electrode configuration, and then analyzes the characteristics of voltage induction, both based on capacitance-network analysis. The analyzed result is verified by experiments that showed good agreements with the provided analysis

This paper presents a project that aims at constructing a biologically inspired fish-like robot. The robot is designed to be capable of propelling itself through oscillations of a flexible caudal fin, like a real underwater fish. In particular, the caudal fin is driven by a mechanism actuated by a unique actuator called electrostatic film motor. In this paper, the dynamics of the electrostatic film motor are briefly introduced so as to well understand its characteristics and behavior. Based on the theoretical analysis and several design considerations inspired by biological concepts, we realize the fish-like robot actuated by an electrostatic film motor and propose swimming control methods for it. Experiments are carried out to confirm the validity of the original design and control. The current robot achieves fish-like maneuvering and approximate velocity of 0.018 m/s in dielectric liquid.

This paper focuses on a practical application of handling contact sensitive objects, such as silicon wafers or hard disk media by a human operator, without any mechanical contact using electrostatic levitation. Stable electrostatic levitation can be realized by controlling the electrostatic attractive force based on measured air gaps. A haptic device is combined with the electrostatic levitation system to minimize human disturbances to the levitated object. Especially during the picking up or placing of the object, where human disturbance is largest, instabilities can be prevented. For the human operator, the handling is easy and intuitive as the objects can be handled by simply moving the tool to the object. The interaction between operator, haptic device, and electrostatic levitation is described in detail. Experimental results show the characteristics of both the pick up task, as well as the place task, which is realized automatically without any external control command.

The present paper proposes an electrostatic actuator that realizes two-degree-of-freedom (DOF) motion of various sheet-like objects. The actuator utilizes electrostatic actuation technology based on induced charges. The technology can directly handle sheet objects, such as papers and plastic films with a particular surface resistance. The structure of the actuator is flat and thin, and thus it can be easily embedded on any desktop so that the desktop can have a function to physically interact with users. With the function, the desktop can be automated in such a way that it drives various objects on it to help users perform various desktop tasks. The prototype actuator presented here uses wire mesh as its electrode panel to realize two-DOF motion. The structure of the wire mesh and basic driving principle of two-DOF actuation are described. The challenge that arises when utilizing wire mesh panel is that actuations for objects can be sometimes coupled if there are multiple objects on the panel; for example, if we try to move only one object, the other objects nearby would move together unexpectedly. To solve this problem, the paper proposes a selective actuation technique that realizes handling of any one object with keeping other objects at rest

A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. The display is incorporated into a tactile telepresentation system to realize explorations of remote surface textures with real-time tactile feedback. In the system, a PVDF tactile sensor and a DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile telepresentation system was evaluated in texture discrimination tests and demonstrated a 79 percent correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.

This paper reports a new MRI (Magnetic Resonance Imaging) compatible actuator that can operate near an MRI without degrading its imaging quality. A high-power electrostatic motor is introduced and its MR-compatibility is examined, both experimentally and theoretically. The proposed motor was fabricated with only paramagnetic materials, and its MR-compatibility was evaluated by measuring the output performance of the motor and the signal-to-noise ratios of the MRI images. The experimental results showed that motor’s thrust force while positioned within the MRI is almost the same as that in normal operation. The signal-to-noise investigation indicated that the motor did not affect the MRI images when it was operated over 60 cm away from the MRI’s RF coil. The theoretical calculations showed that the magnetic field generated by the motor is relatively small and the effect of the MRI’s magnetic fields on the motor is negligible, suggesting that the motor is MR-compatible.

In this paper, a new tactile telepresence system is developed. The new system consists of a multi-channel polyvinylidene fluoride (PVDF) tactile sensor, a friction-type electrostatic tactile display, and a master-slave control system. The tactile sensor, which is situated in the slave site, is equipped with a contact force control unit to reproduce a finger-object contact condition at the master site. Also, the tactile sensor works with a linear motor stage to reproduce the operator's finger motion while exploring a surface. The finger's exploring motion and contact force are measured by sensor systems embedded in the tactile display at the master site. With these units, the system realizes master-slave surface texture presentation. In past research, the electrostatic tactile display showed good performance in displaying uniform and periodic surface textures, or surface roughness. In this research, it was demonstrated that the electrostatic tactile display is also able to display localized or non-uniform surface textures, such as a bump or a step, by extending its control scheme.

Thermal sensation is one of the most important factors for material recognition in virtual environments. Thermal display functions must be embedded into tactile feeling display for satisfactory realism. Since our skin sensors are sensitive to rapid change of temperature and rapid changes occur on the moments of contacts, we need to precisely simulate thermal conditions for the moments, at which contacts occur, to display materials with satisfactory realism. The authors have proposed a thermal model for finger-object contact and principles of thermal tactile display based on the thermal model. In this paper, we mainly report experimental aspects of our thermal tactile display. Prototype thermal tactile display and results of discrimination experiments to evaluate device realism are reported.

A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. This paper reports on the application of the new tactile display in a tactile tele-presentation system. In the system, a PVDF tactile sensor and DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile tele-presentation system was evaluated in texture discrimination tests and demonstrated a 79% correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.

The authors first analyze dynamic properties of rapidly adapting mechanoreceptors in order to derive a principle of tactile displays. It is shown that Meissner corpuscles with coiled axons and Pacinian corpuscles with layered lamellae are suited to detect equivoluminal distortion of skin. Combining these analyses with a model of a contact and a relative motion between an object and the skin, it is shown that a prerequisite for tactile displays is to generate sources of shear stress that can be spatially dispersed at the skin surface and temporally modulated with a stick-slip frequency determined by parameters of the object to be displayed. As a device that satisfies this prerequisite, we propose a tactile display using Surface Acoustic Waves (SAW). The roughness of the surface can be changed continuously by controlling the burst frequency of the SAW.

A micropositioning system for automatic precision assembly is introduced. The proposed precision assembly system is aimed at automation of precision assembly of precision optical or magnetic components, which was previously performed by specially trained technicians. The positioning system is based on the motion mechanism driven by impact force made by piezoelectric actuator; it utilizes dry friction and impulsive inertial force. The motion mechanism consists of the main body, a piezoelectric actuator, and a weight. The motion mechanism can make minute motion of several nanometer and has an unlimited movable range at the same time. The proposed assembly system uses the motion mechanism as a source of impact force. The motion mechanism is proved to have the advantage of positioning resolution, range, and flexibility. An industrial application of this device is also presented.