Hiroyuki Kajimoto

Vision-based sensor for real-time measuring of surface traction fields

The desire to reproduce and expand the human senses drives innovations in sensor technology. Conversely, human-interface research aims to allow people to interact with machines as if they were natural objects in a cybernetic, human-oriented way. We wish to unite the two paradigms with a haptic sensor as versatile as the sense of touch and developed for a dual purpose: to improve the robotic capability to interact with the physical world, and to improve the human capability to interact with the virtual world for emerging applications with a heightened sense of presence. We designed a sensor, dubbed GelForce, that acts as a practical tool in both conventional and novel desktop applications using common consumer hardware. By measuring a surface traction field, the GelForce tactile sensor can represent the magnitude and direction of force applied to the skins surface using computer vision. This article is available with a short video documentary on CD-ROM.

SmartTouch: electric skin to touch the untouchable

Augmented haptics lets users touch surface information of any modality. SmartTouch uses optical sensors to gather information and electrical stimulation to translate it into tactile display. Augmented reality is an engineers approach to this dream. In AR, sensors capture artificial information from the world, and existing sensing channels display it. Hence, we virtually acquire the sensors physical ability as our own. Augmented haptics, the result of applying AR to haptics, would allow a person to touch the untouchable. Our system, SmartTouch, uses a tactile display and a sensor. When the sensor contacts an object, an electrical stimulation translates the acquired information into a tactile sensation, such as a vibration or pressure, through the tactile display. Thus, an individual not only makes physical contact with an object, but also touches the surface information of any modality, even those that are typically untouchable.

Gravity grabber: wearable haptic display to present virtual mass sensation

We propose a wearable haptic display to present the weight sensation of a virtual object, which is based on our novel insight that the deformation on fingerpads makes a reliable weight sensation even when the proprioceptive sensation is absent. This device will provide a new form of ubiquitous haptic interaction.

An Encounter-Type Multi-Fingered Master Hand Using Circuitous Joints

We have developed a new type of master hand to control a dexterous slave robot hand for telexistence. Our master hand has two features. One is a compact exoskeleton mechanism called “circuitous joint,” which covers wide workspace of an operator’s finger. Another is the encounter-type force feedback that enables unconstrained motion of the operator’s finger and natural contact sensation. In this paper, the mechanism and control method of our master hand are introduced and experimental master-slave finger control is conducted.

A Wearable Haptic Display to Present the Gravity Sensation - Preliminary Observations and Device Design

We propose a wearable, ungrounded haptic display that presents the realistic gravity sensation of a virtual object. We focused on the shearing stress on the fingerpads duo to the weight of the object, and found that the deformation of the fingerpads can generate the reliable gravity sensation even when the proprioceptive sensation on the wrist or arm is absent. This implies that a non-grounded gravity display can be realized by reproducing the fingerpad deformation. According to our observations, we had evaluation tests for device design. We implemented the prototype device which has simple structure using dual motors, and then evaluated the recognition ability of the gravity sensation presented on operators fingerpads with this method

Evaluation of a vision-based tactile sensor

Humans can perceive not only the magnitude but also the direction of force applied on the fingertip. When we grasp an object, the weight of it is felt through force that is parallel to the skin of the fingertip, which is how the object can be grasped without slipping. Focusing on this point, we have developed a tactile sensor that can measure a distribution of force vectors. The measurement method is as follows. The tactile sensor consists of a transparent elastic body, blue and red markers inside the elastic body, and a color CCD camera. An applied force on the elastic body results in movements of the markers, which are acquired by the CCD camera. The distribution of force vectors is calculated using this information. This paper reports experimental evaluation results concerning accuracy of determining position of markers, determination of magnitude and direction of force, spatial resolution, and calculation timing.

High‐resolution tactile sensor using the deformation of a reflection image

Purpose – The aim of this paper is to create a sensor that can measure the contact status with high‐resolution than ever.Design/methodology/approach – This paper proposes a new type of optical tactile sensor that can detect surface deformation with high precision by using the principle of optical lever. A tactile sensor is constructed that utilizes the resolution of a camera to the maximum by using transparent silicone rubber as a deformable mirror surface and taking advantage of the reflection image.Findings – It has been found that the sensor can sense the deformation by the object with 1 percent error rate in simulation. In implementation of this time, the error rate results 10 percent.Research limitations/implications – This sensor can be used with broad applications by combining with other devices. As one of future work, the zero method will be used by using active patterns and get more accurate information.Practical implications – Using the transparent silicone rubbers the sensor enables very simple...

Optical torque sensors for implementation of local impedance control of the arm of humanoid robot

This paper describes the recent development of new optical torque sensor in order to replace expensive strain gauge sensor attached at the tip of the anthropomorphic robot arm and realize local impedance control in each jointA round foot controller has a molded cover 75 attached to a molded base 11 by interengaging projections 79 and 16 extending in opposite directions toward each other from the rims of telescoping walls 77 and 13. The wall 77 is near the perimeter of the cover and is concentric with another wall 76 that surrounds the wall 77. The wall 13 concentrically surrounds another wall 14 in the base. The base has openings 96 and the cover has corresponding openings 97 left by the respective molds that form the undersides of the projections 16 and 79. The double-walled structure of the cover telescoping with the double-walled structure of the base prevents inadvertent access to the electrical components in the foot controller. However, the resistence of a variable resistor 21 or 103 in the controller, can be varied by pressure on any part of the cover 75.

Electrotactile Display with Real-Time Impedance Feedback Using Pulse Width Modulation

An electrotactile display is a tactile interface composed of skin surface electrodes. The use of such a device is limited by the variability of the elicited sensation. One possible solution to this problem is to monitor skin electrical impedance. Previous studies revealed a correlation between impedance and threshold, but did not construct real-time feedback loops. In this study, an electrotactile display was constructed using a 1.45 μs feedback loop. Real-time pulse width modulation was proposed, and the relationship between skin resistance and absolute threshold was measured to find a function for determining a suitable pulse width from skin resistance. An evaluation experiment revealed that the proposed algorithm suppressed spatial variation and reduced temporal change.

Optimal design method for selective nerve stimulation and its application to electrocutaneous display

We have developed a tactile display that uses electric current from the skin surface as a stimulus. Our main objective was to independently stimulate a variety of mechanoreceptors and to generate specific sensations by combining stimuli. The key to this goal is selective nerve stimulation. In this paper, a mathematical framework is build for the general design of the selective stimulation. The geometries of electrodes and nerve fibers are arbitrary, and the waveform of the electric current from each electrode is independently controlled. Furthermore, the problem is formulated by linear or quadratic programming, which provides an optimal solution.