Koyu Abe

Verification of an advanced space teleoperation system using Internet

In our previous work, several system elements for space teleoperation were introduced: a Singularity Consistent (SC) teleoperation system, a mixed force and motion commands based space teleoperation system, and a 6-DOF haptic interface (Y. Tsumaki and M. Uchiyama, 1997; Y. Tsumaki et al., 1998). We introduce an advanced space teleoperation system which includes all the above elements. As a result, the system realizes safety against the singularities and excessive force, with good perception for the operator. In addition, to verify the effectiveness of this system, we conducted experiments through the Internet between DLR in Germany and Tohoku University in Japan in January 1999.

Design and evaluation of an encountered-type haptic interface using MR fluid for surgical simulators

A novel encountered-type haptic interface for surgical simulators is proposed. This interface has a container of MR (Magneto–Rheological) fluid, and an operator puts a surgical instrument into the fluid and can feel resistance force. The advantage of this interface is that an operator can move an instrument freely when it does not contact with MR fluid and change instruments easily. If an instrument is mounted mechanically on a haptic interface driven by servomotors, it is difficult to change surgical tools. On the other hand, the developed device does not require a procedure for changing tools and can increase a sense of reality. However, MR fluid cannot display large deformation of a tissue since its elastic region is small. Therefore, a container of the fluid is moved by servomotors. In this paper, concept and design of the interface and performance evaluations are described. In order to specify required display force, cutting force of a liver is analysed, and the maximum force is about 1.6 [N]. The device is designed based on this required force. Relationship between coil current and display force is measured, and the interface can exert 2.7 [N] when the current is 1 [A]. In addition, the validness of the proposed scheme using servomotors is evaluated.

Development of a haptic interface using MR fluid for displaying cutting forces of soft tissues

In open abdominal surgical procedures, many surgical instruments, e.g., knives, cutting shears and clamps, are generally used. Therefore, a haptic interface should display reaction force of a soft biological tissue through such a surgical instrument. Simplest solution for this difficulty is that an actual instrument is mechanically mounted on the traditional haptic interface driven by servomotors. However, operators lose a sense of reality when they change the instrument since they must perform a procedure which is not required in actual surgery for attaching/detaching the instrument to/from the haptic interface. Therefore, a novel haptic interface using MR (Magneto-Rheological) fluid is developed in this research. Rheological property of MR fluid can be changed in a short time by applied magnetic flux density. By cutting the fluid using a surgical instrument, operators can feel resistance force as if they cut tissue. However, MR fluid cannot display large deformation of soft tissues since elastic region of MR fluid is small. Therefore, a container of the fluid is moved by a motion table driven by servomotors. In this paper, concept and design of the haptic interface and performance evaluations are described.

Displaying feeling of cutting by a micro-scissors type haptic device

In this paper, a method for displaying feeling of cutting by a micro-scissors type haptic device is described. Micro-scissors are a type of surgical instrument, which is frequently used in brain surgery under a microscope. A prototype of a micro-scissors type haptic device consists of three components: an interface, a drive member, and force sensors. The interface is designed to equip features of a pair of micro-scissors and has a blade spring on its end. The drive member is composed of two DC-motors and two crank-lever mechanisms as decelerators. The force sensors are composed of strain gauges with H-slits, and implemented into each handle of the interface. For the aid of applying the force sensors to feedback control of cutting resistance forces, compensation for influence of a blade spring on the force sensors is added. Evaluation experiment for basic performance of the device is carried out, and the device is proved to be able to generate the computed cutting resistance forces. Virtual cutting experiment by six subjects is carried out, and it is proved that the device is able to display feeling of cutting.

A plantar H-slit force sensor for humanoid robots to detect the reaction forces

This paper addresses a plantar H-slit force sensor for humanoid robots to detect the reaction force. The zero moment point (ZMP) is calculated from the detected reaction force balance. The H-slit force sensors are structuralized on a plantar frame. Since a H-slit beam unidirectionally deforms, only the normal force from the ground is selectively detected without being affected from the friction force between the sole and ground. The plantar H-slit force sensors are developed for a humanoid robot. A model is proposed to simulate the sensor output. The simulated outputs are compared with results of the finite element analysis (FEA) and the experimentation results.

A directional deflection sensor beam for very small force/torque measurement

We proposed an H-slit type parallel beam, which can be effectively utilized to achieve a highly unidirectional deformable structure for force/torque sensors. The structure is an extension of the parallel beam structure. And hence, the proposed design structure will result in 4-bar link closed mechanism the joints of which are deformable, so the strain gauges are fixed at these positions. This is the basic idea and unique feature of our proposed design. The H-slit beam can be used to measure very small-generated forces. In this paper, we present above characteristics of the both beam structures with finite element method (FEM) analysis, and outline of a small force/torque sensor using H-slit beams. Moreover reported in this article is over load protection mechanism, which exhibits beams effectiveness and its ability, to withstand overload conditions without much deformation. This is due to the protection provided in the cross section of the beam.

A human assistant robot system for handling heavy mechanical parts in assembly lines

Recently, industrial robots are widely employed in various fields. However, some assembly tasks are still manually completed because of complicate assembly sequences and requirements of high accuracy positioning. Therefore, we propose a new system in which human workers cooperate with assistant robot complementarily in assembling a heavy mechanical part. This paper describes the prototype of a gravity compensation mechanism and a gripper employed in this robot. The gravity compensation mechanism is designed to relieve the burden of worker for holding the mechanical part. The developed gripper is characterized by its implementation of non-force closure grasping. It allows to change the attitude of the payload in the envelope of the gripper closure.

Identification of physical properties of swine liver for surgical simulation using a dynamic deformation model

In recent medical field, surgical simulators with the technique of virtual reality are expected to provide a new means to support the surgical front. We have developed a simulation for brain surgery using a dynamic deformation model. Most of physics models, including the dynamic deformation model, are required to identify the physical properties of target tissues. In this research, we identified physical properties of swine liver. Youngs Modulus, Poissons Ratio and damping coefficient is necessary for the simulation. There are previous researches about identification of Youngs Modulus, but that about identification of Poissons Ratio and damping coefficient are few. Therefore, in this research, we conduct tension experiments to measure Youngs Modulus and Poissons Ratio, and vibration experiments to measure damping coefficient.

A cooperative industrial partner robot for handling heavy parts

Recently, industrial robots are widely employed in various fields for automation. However, some assembly tasks still need intervention of human workers, because of the complicated assembly skills involved. In order to assist the assembly tasks, some industrial partner robot have been introduced into the assembly line. These devices are designed merely for supporting the weight of the heavy parts, and sometimes they embarrass the human work from applying their skills. In this research we propose a new system in which robots and human workers cooperate complementarily in an assembly task. This paper describes a prototype robot designed following this idea.

Overload Protection Mechanisms for Force Detecting Beam in a Force Sensor

Overload prevention is important for a force sensor in order to avoid fatal damage due to unexpected external forces. Until now, some mechanisms have been proposed which prevent damage of the sensor structure using screw and straight pin. However, nothing has been no reported regarding the utility of this mechanism. We proposed a unidirectional force sensor based on the H-slit type parallel beam structure in our previous work. This sensor structure alone can be realized for overload protection without any other parts and can be embedded as overload protection mechanism in the structure. In this paper, we verify the utility of conventional mechanisms and evaluate the usefulness of the slit type one which we have developed.