Katsunari Sato

Finger-Shaped GelForce: Sensor for Measuring Surface Traction Fields for Robotic Hand

It is believed that the use of haptic sensors to measure the magnitude, direction, and distribution of a force will enable a robotic hand to perform dexterous operations. Therefore, we develop a new type of finger-shaped haptic sensor using GelForce technology. GelForce is a vision-based sensor that can be used to measure the distribution of force vectors, or surface traction fields. The simple structure of the GelForce enables us to develop a compact finger-shaped GelForce for the robotic hand. GelForce that is developed on the basis of an elastic theory can be used to calculate surface traction fields using a conversion equation. However, this conversion equation cannot be analytically solved when the elastic body of the sensor has a complicated shape such as the shape of a finger. Therefore, we propose an observational method and construct a prototype of the finger-shaped GelForce. By using this prototype, we evaluate the basic performance of the finger-shaped GelForce. Then, we conduct a field test by performing grasping operations using a robotic hand. The results of this test show that using the observational method, the finger-shaped GelForce can be successfully used in a robotic hand.

Haptic telexistence

Haptic Telexistence provides highly realistic haptic interaction among humans and objects located in remote places. We have developed innovative devices and constructed a master-slave system to realize Haptic Telexistence. Human interaction will be dramatically improved by this concept that perceives us the properties of an object.

ExoInterfaces: novel exosceleton haptic interfaces for virtual reality, augmented sport and rehabilitation

We developed novel haptic interfaces, FlexTorque and FlexTensor that enable realistic physical interaction with real and Virtual Environments. The idea behind FlexTorque is to reproduce human muscle structure, which allows us to perform dexterous manipulation and safe interaction with environment in daily life. FlexTorque suggests new possibilities for highly realistic, very natural physical interaction in virtual environments. There are no restrictions on the arm movement, and it is not necessary to hold a physical object during interaction with objects in virtual reality. Because the system can generate strong forces, even though it is light-weight, easily wearable, and intuitive, users experience a new level of realism as they interact with virtual environments.

Measurement of force vector field of robotic finger using vision-based haptic sensor

It is expected that the use of haptic sensors to measure the magnitude, direction, and distribution of a force will enable a robotic hand to perform dexterous manipulations. Therefore, we have developed a new type of finger-shaped haptic sensor that can measure a three-dimensional force vector field over a contact surface. The sensor consists of a transparent elastic body, two layers of internal blue and red markers, and a CCD camera to capture the movements of the markers. Using the elastic theory, we can calculate the force vector field from the captured movements of the markers. However, the elastic theory cannot be applied to the finger-shaped sensor because of its complicated shape. Therefore, we use actual measurements for the calibration in order to develop a prototype of the sensor. Then, we evaluate its basic performance. The result shows that the sensor performance can be improved further, and the sensor can be successfully used in a robotic hand.

Electrotactile Display for Integration with Kinesthetic Display

The goal of this study is to develop a haptic interface for dexterous manipulation. To achieve this, we proposed electrotactile-kinesthetic integration. Our electrotactile display presents natural touch sensations of objects. In addition, this display is so small that it is considered to not affect the moving range of fingers. The haptic interface for dexterous manipulation is realized by mounting it on a kinesthetic display having a wide workspace. The electrotactile display on the integrated haptic interface is used actively. Therefore, we actively evaluated the performances of the electrotactile display on the single-fingered prototype system. The results revealed the present performance of the system. Subsequently, it also shows the possibility of further improving of the haptic interface by devising an electrotactile rendering method.

Design of electrotactile stimulation to represent distribution of force vectors

Transmission of the distribution of force vectors on a fingertip improves the stability of a given operation in a tele-operation system. As such, we seek the representation of the distribution of force vectors via an electrotactile display. The electrotactile display directly activates nerve fibers connected to mechanoreceptors, thereby representing a tactile sensation. The system has a simple structure, is easily controlled and, it has seen a number of different applications. However, the majority of the conventional electrotactile displays only present a symbolic sensation of contact. In this paper, we propose the design of electrotactile stimulation for the distribution of force vectors, on the basis of the concept of “tactile primary colors”. Considering that a selective stimulation of mechanoreceptors enables the representation of the distribution of force vectors, we evaluate the proposed design in terms of the distribution, magnitude, and direction of a force vector. The results demonstrate that the proposed design is a viable approach to representing the distribution of force vectors.

FlexTorque: innovative haptic interface for realistic physical interaction in virtual reality

Kinesthetic stimulations, produced by forces exerted on the body, are sensed by mechano-receptors in the joints, tendons, and muscles. When a human hand holds a heavy object, its weight produces torques in the wrist, elbow, and shoulder joint. Each muscle generates a torque at a joint that is the product of its contractile force and its moment arm at that joint. The idea behind FlexTorque is to reproduce human muscle structures that allow us to perform dexterous manipulations and interactions. The result is a wearable haptic interface that presents realistic kinesthetic stimulus to the human arm.

Improvement of Shape Distinction by Kinesthetic-Tactile Integration

The sensation of touch is divided into kinesthetic and tactile sensation. It is important for a touch sensation device to present both types of sensations. We mounted an electrotactile display on a kinesthetic display, and realized a compact display of touch sensation. This system can improve the ability to identify objects. In this paper, we evaluate the effect of integrating kinesthetic and electrotactile sensations for identifying the shape of an object

Development of grip-type master hand “MeisterGRIP”

We propose a novel grip-type master hand called MeisterGRIP that measures grip force in terms of a force vector distribution. This device is expected to allow intuitive robot manipulation using vision-based haptic-sensing technology. Furthermore, it can be used for general-purpose manipulation and is tolerant to individual differences in hand size and grasping posture. We constructed MeisterGRIP and evaluated the accuracy of the measured grip force. Furthermore, we constructed and exhibited a complete robot manipulation system using MeisterGRIP to demonstrate the possibility of using MeisterGRIP as a general-purpose master hand.

Electrotactile Stimulation Based on Strain Energy Density of the Fingertip

The shape recognition of an object is important for dexterous manipulation by humans. Therefore, we have developed a haptic display that integrates both electrotactile and kinesthetic sensations to present shape information. However, the electrotactile display only presents the contact field between the object and the fingertip. Therefore, we propose a method of electrotactile stimulation using the strain energy density model at the fingertip to generate the tactile sensation of the fingertip deformation. The result of the shape recognition experiment verifies the efficiency of the proposed method.