Hideo Fujimoto

Impact of network time-delay and force feedback on tele-surgery

ObjectWe have developed a robotic minimally invasive surgical system within a tele-surgery capability and conducted several times of tele-surgery experiments including Japan–Thailand and Japan–Korea tele-surgery experiments by using conventional network infrastructures. In these experiments, laparoscopic cholecystectomies have been successfully performed on pigs. On the other hand, repetitive task evaluation studies are also crucial for further studies on tele-surgery applications. Nowadays, task evaluations of tele-robotic system within network time-delay have been studied in past years by many researchers. These experiments have been mostly focused on simplified tasks such as a peg-in-hole task. However, most of surgical procedures in minimally invasive surgery are based on medical specific skills such as anatomical knowledge and past experiences of surgeons. From these perspectives, a trial experiment within two tasks including surgery oriented manipulations was conducted to study the impact of network time-delay and force feedback on tele-surgery.Materials and methodsThe experiment was conducted by using the minimally invasive surgical system. As the experimental setup, a research and development Internet, JGN2 (Japan Gigabit Network 2) was used as a network infrastructure, and two tasks were performed by 15 subjects including 5 medical doctors. The trial conditions were given by changing time-delay (on the both tasks) and force feedback (on the first task). The first task was configured to test a simple surgical procedure, which is commonly performed in a laparoscopy as translational motions of surgical tools. The subjects were instructed to touch four columns located on points of a square. The second task was configured to test integrated surgical procedures. The subjects were instructed to perform a part of suturing procedures by using the robotic bending forceps.ResultsIn the first task, the completion time was increased approximately 50% by time-delay. By using force feedback, the applied force was decreased. However, the effectiveness of force feedback was not strongly shown in MD group. On the other hand, the effectiveness of the force feedback was strongly shown in the applied force on the tip of surgical tool in both MD and non-MD groups. In the second task, the adverse impact of time-delay was not strongly shown in MD group. From the analysis of the motion records found that a skill of experienced surgeons on “occlusion problem” could be related in the results. These results indicate that skilful operators on surgical procedures can overcome the adverse impact of time-delay by introducing their skills depending on required surgical tasks. However, the drawback of time-delay still remains concerning on safety issues. The effectiveness of the force feedback was strongly shown in the first task in terms of the applied force on the surrounding environment.ConclusionsForce feedback is an essential technology for further applications of tele-surgery. In addition, the force feedback technology can be partially used for compensating the drawback of time-delay.

Dissociation of 5-S RNA from 50-S ribosomal subunits of Escherichia coli by phosphate treatment

Abstract The detailed conditions of the phosphate-induced conformational change in Escherichia coli ribosomes were studied. For the maximum conformational change mediated by phosphate, the concentration of ribosomes should be less than 50 A260 nm units/ml. An incubation for at least 10 min at 37° is required. 50-S subunits are converted into conformationally changed particles independently of the presence or absence of 30-S subunits. Oligonucleotides, previously added to the incubation mixture to prevent RNA degradation, are not essential. It was examined whether or not 5-S RNA was released from 50-S subunits during phosphate-induced, conformational changes in ribosomes. When treated with phosphate, purified 50-S subunits were shown to be converted into 25-S particles with release of 5-S RNA. In the presence of 30-S subunits, on the other hand, 50-S subunits were converted into 25-S particles without releasing appreciable amounts of 5-S RNA. Poly(U)-dependent polyphenylalanine synthesis was examined using 50-S subunits treated with phosphate in the presence or absence of 30-S subunits. In the absence of 30-S subunits, phosphate-treated 50-S subunits exhibited no polyphenylalanine formation even if 5-S RNA was added, while those treated in the presence of 30-S subunits retained 10–20 % of the protein-synthesizing activity of normal 50-S subunits.

COMPLIANCE CONTACT CONTROL OF MECANUM WHEELED MOBILE ROBOT FOR IMPROVING SAFETY

Recently, robots sharing spaces with humans have been spreading. Therefore, since the situations in which the robots physically contact with humans and/or environments will increase inevitably, the kinetic control in consideration of the circumference is needed. In general, the non-contact sensor is used on mobile robots. However, since such a sensor has a dead angle and it may break down, another way improving the safety is required. Although a force or tactile sensor may be another solution, a lot of sensors are needed in order to compensate a dead angle. Therefore, in this paper, we propose a method to improve the safety by estimating the external force applied on the wheeled mobile robot and by using compliance control based on virtual conveyor. The proposed method doesn’t need an additional cost of sensor, and has an advantage because of having no dead angle about driving directions of the robot.