Gen-ichiro Kinoshita

A pattern classification by dynamic tactile sense information processing

Abstract This paper describes pattern classification with an artificial tactile sense. In this method, an objects shape is determined by touching, groping and grasping it with an artificial hand with tactile sense. A simplified experiment classifying cylinders and square pillars was performed by an artificial hand with on-off switches instead of pressure sensitive elements. Highly reliable results were obtained. In addition, results of a surface groping experiment are given.

Haptic aspect graph representation of 3-D object shapes

The authors describe the haptic aspects through the graph representations of tactile sensing when exploring the shapes of different objects. The haptic aspects are defined as the topologically equivalent equivalent classes of the tactual images for an object. that is its edges, faces, vertices, and concave features. A high-density optical tactile sensor has been developed to obtain tactual images of an objects surface. Experimental results are given for the haptic aspect graph representation of tactual images by using the prototype tactile sensor.<<ETX>>

New Type of Miniaturized Optical Range-Sensing Methods RORS and RORST

Two types of miniaturized optical range-sensing methods have been developed. The first is called RORS (Riken Optical Range-Sensing Scheme). In this method, a mirror tunnel is first placed between an objective lens and an object to be measured; a bright spot is then projected onto the object through the objective lens. This spot is observed through the objective lens after reflection with the mirror tunnel, and range information is determined by the triangulation. The width of an optical system can be reduced remarkably smaller than the effective base line length of the triangulation. Therefore, it is suitable to miniaturize a range-sensing system such as an optical stylus and a proximity sensor. The second method, RORST (Riken Optical Range Sensing Method for Surface Tracing), projects an axially symmetrical light sheet onto an object and a ring pattern is produced. The ring pattern image is then projected onto the observation plane by the objective lens, radii of the ring pattern image for different azimuths are detected, distances corresponding to the specified azimuths are determined by the triangulation, and thus the information of partial inclination can be obtained.

Haptic Aspect Graph Representation Of 3-D Solid Object Shapes By Tactile Sensing

This paper describes a concept of a haptic aspect(H-aspect) graph representation of the tactile sensing over an objects surface. The H-aspects are defined as the topologically equivalent classes of the tactual images for the tactile sensing of an objects surface. The H-aspect graph representation indicates the structured relationships of the H-aspects for the tactual images of an objects surface, that is, its edges, faces, vertices, and concavity. The acqui- sition of the H-aspects of an object by the tactile sensing requires the extraction of the adequate tac- tile images for the H-aspects. A high density optical tactile sensor has been developed in order to obtain the tactual images of an objects surface. Experimental results are giv- en for the H-aspect graph representation of tactual images by using the prototype tactile sensor.

Dynamic sensing experiments of reaction force distributions on the sole of a walking humanoid robot

This paper describes methods for sensing the reaction forces acting on the foot and on the sole of a humanoid robot during walking. A force sensor is described, which utilizes sensors at each of four corners of the foot to measure the center of pressure during walking. A tactile sensor was also constructed from pressure conductive rubber sandwiched between upper and lower electrode arrays positioned at right angles to each other. This sensor provides information about the force distributions acting on the sole of the foot. Results are presented of measurements of the force distribution acting on the sole of the foot during walking of a humanoid robot on a flat surface and over thin objects on the floor.

Dynamic contact sensing of soft planar fingers with tactile sensors

Focuses on a method of estimating contact force dynamically between environment and an object, which is grasped by the soft planar fingers with tactile sensors. The external contact force acting on the grasped object causes the tactile sensors to generate the displacement distributions and the force distributions. We present a method of dynamic tactual image acquisitions for both distributions at the pseudo video rate. Experimental results show the measurement of the tactual image flows due to the deflection of an object and the magnitude and orientation of force vectors operating on the finger according to the external contact force. The contact position of the external force acting on the grasped object is estimated within 15% from the tactual image distributions.

Robotic range sensor with projection of bright ring pattern

A new type of optical range sensor is being proposed as a robotic sensor. The range sensor consists of the projection subsystem of an axially symmetrical light sheet and the detection subsystem for monitoring the focussing process of a lens. The projection subsystem produces a bright ring pattern through an objective lens on the surface of an object. Next, the distance from the range sensor to the surface of an object is calculated from the position of the lens. The prototype range sensor is able to measure the distance in the range of 430 to 570 mm with an accuracy of 0.3 mm. As the position of the objective lens is controlled so that the ring pattern projected on the surface of an object becomes a fine spot, the detection subsystem finds the position of the objective lens on which the output of photodiode comes to be maximum.

Sensing of contact point between a grasped object and environment by tactile behavior of a parallel two-fingered hand

This paper proposes a method of estimating contact force between the environment and an object grasped by a parallel two-fingered hand with tactile sensors developed by the authors. The sensors can get 2D patterns of pressure distribution and have many potential applications such as recognition of a grasped object, assembly tasks and so on. In order to achieve assembly tasks using multi-fingered hands, two kinds of parameters are essential: one is the geometrical relationship between the coordinate systems of the hand and of the grasped object, and the other is the information about the position of contact point and the contact force between the grasped object and its environment. When the parallel two-fingered hand are used for assembly tasks, the geometrical relationship between the hand and the object can be easily obtained. Thus, this paper describes how to detect the contact point and to measure the contact forces by the tactile sensors. First, the principle of the sensor is explained briefly. Second, the way to use the tactile sensor as a force sensor is shown. Since the information from the sensor is not enough to identify the contact point and the contact force, additional measurements at different positions are needed. The algorithm for the tactile behaviors are proposed.

Optimal grasping for a parallel two-fingered hand with compliant tactile sensors

A method of determining optimal grasping forces for a parallel two-fingered hand with compliant 2D tactile sensors is described. The tactile sensors can get 2D patterns of pressure distribution and have many potential applications such as shape recognition of a grasped object, assembly tasks and so on. In order to achieve assembly tasks using robot hands, information about the position of contact point and the contact force between the grasped object and its environment is essential. When contact force is applied to a grasped object from the environment, the pressure patterns of tactile sensors change according to not only amplitude of the applied force but also the contact position. Thus, a way to derive the contact position and force by tactile sensor data has been studied until now, and it is proven that the maximum measurable contact force from the environment depends on not only sensor characteristics but also grasping force. In the paper a way to determine the optimal grasping force to measure the largest contact force is proposed and some fundamental experiments for testing the derived grasping forces are done.

High compliance sensing behavior of a tactile sensor

Describes the sensing behavior of a high compliant tactile sensor on an objects surface and a formulation of the tactual sensing using methods of differential geometry. The tactile sensor has been manufactured with a function of high compliance, which is achieved with silicone rubber placed on a sensing mechanism organized for the detection of contact patterns. The mechanism is constructed as an optical wave guide which is capable of transmitting the contact pattern to a CCD camera. From the contact pattern, the tactile sensor detects the displacement distribution and the force distribution corresponding to the objects surface shape. By using a method derived from differential geometry, the geometrical contact mechanisms between the sensor and the surface of an object are discussed. The first fundamental form and the second fundamental form are defined by the displacement distribution generated by the tactual sensing. The local shape of the objects surface in, the neighborhood of a contact point is determined from the Gaussian curvature and the mean curvature given by the first fundamental form and the second fundamental form defined by the displacement distribution. Experimental results for estimating an objects local surface shape are presented for a tactile sensor manufactured for trial experiments.