Seiichi Teshigawara

Grasping force control of multi-fingered robot hand based on slip detection using tactile sensor

To achieve a human like grasping with a multi- fingered robot hand, the grasping force should be controlled without using information from the grasped object such as its weight and friction coefficient. In this study, we propose a method for detecting the slip of a grasped object using the force output of Center of Pressure (CoP) tactile sensors. CoP sensors can measure the center position of a distributed load and the total load applied on the surface of the sensor, within 1 ms. These sensors are arranged on the fingers of the robot hand, and their effectiveness as slip detecting sensors is confirmed in tests of slip detection during grasping. Finally, we propose a method for controlling grasping force to resist tangential force applied to the grasped object using a feedback control system with the CoP sensor force output.

Highly sensitive sensor for detection of initial slip and its application in a multi-fingered robot hand

Tactile sensors for slip detection are essential for implementing human-like gripping in a robot hand. In previous studies, we proposed flexible, thin and lightweight slip detection sensors utilizing the characteristics of pressure-sensitive conductive rubber. This was achieved by using the high-frequency vibration component generated in the process of slipping of the gripped object in order to distinguish between slipping of the object and changes in the normal force. In this paper, we design a slip detection sensor for a multi-fingered robot hand and examine the influence of noise caused by the operation of such a hand. Finally, we describe an experiment focusing on the adjustment of the gripping force of a multi-fingered robot hand equipped with the developed sensors

Development of high-sensitivity slip sensor using special characteristics of pressure conductive rubber

Even with the eyes closed, humans are able to grip an object with minimal force without such information as the coefficient of friction or the weight. Tactile sensors capable of detecting slippage are necessary for this gripping action to be realized in a robot hand. Heretofore, many slip sensors were developed and produced, but there was not a slip sensor of simple structure practical for installation on fingertips of a robot hand. Therefore, we propose a low-profile/lightweight slip sensor of simple structure. The special properties of pressure conductive rubber are utilized as a detection device in this sensor. In this paper, we discuss the results of trial manufacture and of slip detection property testing of this sensor. Moreover, we will report the results of slip prevention experiments by this prototype slip sensor, and indicate that the pressure conductive rubber is promising as a material of slip sensor.

High sensitivity initial slip sensor for dexterous grasp

Slip-detecting tactile sensors are essential for achieving human-like gripping motion with a robot hand. In previous research, we developed a flexible, thin and lightweight slip sensor that exploits the characteristics of pressure conductive rubber. However, using this sensor, it was difficult to distinguish between object slip and a change in the normal force. Therefore, in the present research, we investigated a method for identifying object slip by analyzing the frequency components of the output signal from the sensor. As a result, we found that high-frequency components of 1 kHz or more are included in the complex voltage signal generated by object slip. Therefore, by using this high-frequency component, we developed a simple sensor that distinguished between both contact and initial slip with high sensitivity.

A net-structure tactile sensor covering free-form surface and ensuring high-speed response

A tactile sensor is developed with the aim of covering a robots entire structure, while reducing wiring requirement and ensuring high-speed response. The sensor detects the center point of load distribution on 2-dimensional surfaces as well as the overall load. There are only 4 signal wires from the sensor. The sensor response time is nearly constant (within 1ms) regardless of the number of detection elements, their placements or sensor areas. In this paper, the principles behind the operation of this sensor and the results of experiments using the sensor are described. Further, a developed tactile element composed of pressure-sensitive materials and chip-resistors is described.

Development of high speed and high sensitivity slip sensor

Slip detecting tactile sensors is essential to achieving a human-like gripping motion with a robot hand. Up until now, we have developed flexible, thin and lightweight center of pressure (CoP) sensor. The sensor, constructed of pressure conductive rubber sandwiched between two sheets of conductive film, is able to detect the center position of the load distribution and the total load. Recently, detection of initial slip has been shown to be possible. However the detection principles are unclear. Therefore, we carried out verification experiments of the slip detection properties of the CoP sensor and the detection principle. In the results, we found a change in electrical conductivity produced with a shear deformation of the pressure conductive rubber. In this paper, we will discuss the slip detection properties of the CoP sensor and detection principle.

High sensitivity slip sensor using pressure conductive rubber

Slip detecting tactile sensors are essential to achieve a human-like gripping motion with a robot hand. In previous researches, we have proposed flexible, thin and lightweight slip sensor utilizing characteristics of pressure conductive rubber. However, It was hard for this sensor to distinguish between the object slip and the normal force change. Therefore, we consider the separative method using high frequency elements generated by object slipping. In this paper, we design the information processing method and developed the sensor detecting both contact and initial slip in high sensitivity and a simple composition.

High sensitivity slip sensor using pressure conductive rubber for dexterous grasp and manipulation

Slip-detecting tactile sensors are essential for achieving human-like gripping motion with a robot hand. In previous research, we developed a flexible, thin and lightweight slip sensor that exploits a resistance change of the pressure conductive rubber. This sensor distinguishes between both contact and initial slip by using a complicated resistance change just before slippage of object is generated. In this study, we evaluate the stability of the output in the case of differing initial normal forces and changing surface properties of an object. Finally, we describe an experiment on adjustment of the gripping force by a multi-fingered robot hand.

Study of high speed and high sensitivity slip sensor characteristic of conductive material

Slip detecting tactile sensors are essential to achieving a human-like gripping motion with a robot hand. Up until now, we have developed flexible, thin and lightweight center of pressure (CoP) sensor. The sensor, constructed of pressure conductive rubber sandwiched between two sheets of conductive film, is able to detect the center position of the load distribution and the total load. Recently, detection of initial slip has been shown to be possible. However the detection principles are unclear. Therefore, we carried out verification experiments of the slip detection properties of CoP sensor and the detection principle. In the results, we found a change in electrical conductivity produced with a shear deformation of the pressure conductive rubber. In this paper, we will discuss the slip detection properties of CoP sensor and detection principle. We will also apply these principle to describe the structure of high speed/high sensitivity slip sensor.