A method of acquiring reaction force distributions on a sole of a walking humanoid robot from ground is developed. The tactile sensors are embedded on the soles of a humanoid robot for the acquisition of the ground reaction force distributions. The tactile sensor consists of a pressure conductive rubber sheet put between upper and lower electrode arrays and was able to measure the reaction forces from 0.00 MPa to 0.05 MPa at all of the sensing elements. Force distribution data including 30 /spl times/ 16 points can be obtained at a period of 20 ms by using RTLinux. It is shown that the ground reaction force distributions can experimentally be obtained by a humanoid robot "HOAP-I" and the locus of ZMP along walking of a humanoid robot is given. This information is useful for constructing feedback control loops or generating a new walking gait.

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.

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.

Describes the sensing behavior of a high compliant tactile sensor on an object's 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 object's 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 object's 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 object's local surface shape are presented for a tactile sensor manufactured for trial experiments.

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.

This paper proposes methods of fusing tactual and visual data for a hand-eye cooperation system, and realizes the methods using a developed tactile sensor. Since tactual and visual data convey information with different characteristics, smart fusion of these two sensor data is expected to provide useful additional information. In this paper, visually identified edges and planar regions or edges from tactual data are utilized and three fusion methods are introduced (1) measurement of a 3D edge when a tactile sensor contacts a plane, (2) measurement of a 3D edge when a tactile sensor contacts a plane at the edge and (3) measurements of a cylinder when a tactile sensor contacts the cylinder at an edge.

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 object's surface. Experimental results are given for the haptic aspect graph representation of tactual images by using the prototype tactile sensor.>

This paper describes a concept of a haptic aspect(H-aspect) graph representation of the tactile sensing over an object's surface. The H-aspects are defined as the topologically equivalent classes of the tactual images for the tactile sensing of an object's surface. The H-aspect graph representation indicates the structured relationships of the H-aspects for the tactual images of an object's surface, that is, it's 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 object's surface. Experimental results are giv- en for the H-aspect graph representation of tactual images by using the prototype tactile sensor.