Kohtaro Ohba

Remote coordinated controls in multiple telerobot cooperation

Various coordinated control schemes are explored in the multi-operator-multi-robot (MOMR) tele-collaborative system through a network with time delay. Multi-robot cooperation has rapidly emerged in many possible applications such as the plant maintenance, construction, and surgery, because it would have a significant advantage over a single robot in such cases. Thus, time-delayed control of a multi-robot system is expected to play an important role in remote operations, too. However, the effect of time-delay would pose a more difficult problem to the MOMR teleoperation systems and seriously affect their performance. In this work, first, we have built an experimental system to investigate the remote cooperation in MOMR teleoperation. Then, different coordinated control methods are proposed to cope with the collision, arising from the time delay over the network. To verify the validity of the proposed schemes, we have carried out various experiments on a planar block arrangement by two slave arms employing graphic simulators and a LAN subject to a significant communication delay.

Design and Performance Tuning of Sliding-Mode Controller for High-Speed and High-Accuracy Positioning Systems in Disturbance Observer Framework

The tuning method of controllers can be used for effectively determining the overall performance of positioning systems. In particular, this method is highly effective in the case of high-speed and high-accuracy positioning systems. In this paper, a sliding-mode controller that uses one of the well-known approaches of robust control methodology is designed for high-speed positioning systems that require a high-accuracy performance. A performance-tuning method based on a disturbance observer (DOB) structure is also proposed. First, a generalized disturbance attenuation framework named robust internal-loop compensator (RIC) is introduced, and a sliding-mode controller based on a Lyapunov redesign is analyzed in the RIC framework. Then, the DOB properties of the sliding-mode controller are presented, and it is shown that the performance of the closed-loop system with a sliding-mode controller can be tuned up by using the structural characteristics of the DOB. These results make the design of an enhanced sliding-mode controller possible. Finally, the proposed algorithm is experimentally verified and discussed with two positioning systems. Experimental results show the effectiveness and the robustness of the proposed scheme.

Web Services Based Robot Control Platform for Ubiquitous Functions

In this paper, we employ Web services, programmable application logic accessible using standard Internet protocol, to enable a robot to access the distributed application logic based on the recent network technologies like XML, SOAP, WSDL, UDDI. Applications can communicate with each other in a platform and programming language independent manner. We first discuss a ubiquitous control platform based on ubiquitous functions to allow a robot the infinitive freedom of movement and knowledge acquirement. We then explain the fundamental ubiquitous functions management framework for a robot. In this framework, the applications are constructed from multiple Web services that work together to provide data and services for the application. Finally, the proposed scheme is applied to the control of the knowledge distributed robot system.

A distributed knowledge network for real world robot applications

We propose a collaborative knowledge network that we call omniscient spaces in the attempt to generate sophisticated robotic behavior with minimal programming effort. New products are manufactured and brought into our daily life everyday. Robots should need a way to easily integrate new products into their existing recognizable environments. Radio frequency identification gains increasing attention to support context and ambient awareness in dynamically changing environments. To solve robot programming difficulties in our environments, the collaborative knowledge network connects heterogeneous knowledge resources to collectively build up the robots knowledge required to accomplish a task. Specifically, a decentralized knowledge acquisition and task specific integration model is proposed, where the proposed knowledge integrator merges specific knowledge with existing knowledge into a task requiring knowledge. For this, manufacturers put their product data tailored to plan robot motions online and robots may access the data without authorization. In this work, the best possible scenario under current technological limitations is proposed for real world robot applications. A detailed analysis of the knowledge flow model is described. To verify the validity of the proposed model, a test bed is built and table clearing task is performed according to the distributed knowledge management framework.

Ubiquitous Localization and Mapping for Robots with Ambient Intelligence

In this paper, a novel approach of knowledge management for the space/location perceiving capacity of robots is proposed. First, the ubiquitous function services composed of smart object, smart logic, and smart discovery service are proposed in order to distribute knowledge flexibly and reliably to changing environment and also for a robot to invoke and merge the distributed knowledge more freely. Next, physical and virtual spaces are merged by RFID tags. Through this, it is shown that ambient intelligence is realized and the space localization and mapping problem of robots can be more easily solved. Finally, the experiment based on an example scenario is carried out to verify the proposed method in the informative space named u-RT space which has two kinds of RFID tags, a virtual space with ubiquitous function services realized by Web services, and a networked robot system which works in these spaces

Microscopic vision system with all-in-focus and depth images

Abstract.In this paper, a high-speed digital processed microscopic observational system for telemicrooperation is proposed with a dynamic focusing system and a high-speed digital-processing system using the “depth from focus” criterion. In our previous work [10], we proposed a system that could simultaneously obtain an “all-in-focus image” as well as the “depth” of an object. In reality, in a microoperation, it is not easy to obtain good visibility of objects with a microscope focused at a shallow depth, especially in microsurgery and DNA studies, among other procedures. In this sense, the all-in-focus image, which keeps an in-focus texture over the entire object, is useful for observing microenvironments with the microscope. However, one drawback of the all-in-focus image is that there is no information about the objects’ depth. It is also important to obtain a depth map and show the 3D microenvironments at any view angle in real time to actuate the microobjects. Our earlier system with a dynamic focusing lens and a smart sensor could obtain the all-in-focus image and the depth in 2 s. To realize real-time microoperation, a system that could process at least 30 frames per second (60 times faster than the previous system) would be required. This paper briefly reviews the depth from focus criterion to Simultaneously achieve the all-in-focus image and the reconstruction of 3D microenvironments. After discussing the problem inherent in our earlier system, a frame-rate system constructed with a high-speed video camera and FPGA (field programmable gate array) hardware is discussed. To adapt this system for use with the microscope, new criteria to solve the “ghost problem” in reconstructing the all-in-focus image are proposed. Finally, microobservation shows the validity of this system.

Multioperator teleoperation of multirobot systems with time delay: part I--aids for collision-free control

In this paper, various coordinated control schemes are explored in Multioperatormultirobot (MOMR) teleoperation through a communication network with time delay. Over the past decades, problems and several notable results have been reported mainly in the Single-OperatorSingle-Robot (SOSR) teleoperation system. Recently, the need for cooperation has rapidly emerged in many possible applications such as plant maintenance, construction, and surgery, because multirobot cooperation would have a significant advantage over a single robot in such cases. Thus, there is a growing interest in the control of multirobot systems in remote teleoperation, too. However, the time delay over the network would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, our recent efforts devoted to the coordinated control of the MOMR teleoperation is described. First, we build a virtual experimental test bed to investigate the cooperation between two telerobots in remote environments. Then, different coordinated control aids are proposed to cope with collisions arising from delayed visual feedback from the remote location. To verify the validity of the proposed schemes, we perform extensive simulations of various planar rearrangement tasks employing local and remote graphics simulators over an ethernet LAN subject to a simulated communication delay.

Design of 3-DOF parallel mechanism with thin plate for micro finger module in micro manipulation

A dexterous micro manipulation system was developed for applications such as assembling micro machines, manipulating cells, and micro surgery. We (1996, 1999) have proposed a concept of a two fingered micro hand, and designed and built a prototype. We succeeded in performing basic micro manipulations, including the grasp, release, and rotation of a microscopic object. The two-fingered micro hand prototype needs to be more miniaturized for higher accuracy and use in the small chamber of SEM. In this paper, we propose a new 3-DOF parallel mechanism for the micromanipulator in order to achieve low cost and small size. The new mechanism is only used for punching holes and bending a thin plate. The two-fingered micro hand with the mechanism was designed and a prototype developed. An experiment shows the excellent micro capability of the mechanism.

Motion planning for hand-over between human and robot

In the future, robots may perform cooperative tasks with humans in daily life. In this paper, the authors focus on a hand-over motion as an example of cooperative work between a human and a robot, and propose an algorithm which enables a robot to perform a human-like motion. First the authors analyze trajectories and velocity patterns of a hand-over motion performed by two humans. The experimental results show that a receivers motion during hand-over has some typical characteristics. The authors then confirm that a human-like motion can be generated using these characteristics. Finally, the authors plan the robots motion considering these results. Initially, two kinds of potential fields are used to generate a motion command which leads the robot along a trajectory similar to that followed by the human. In addition, more precise motion is considered at the end of the hand-over operation to guarantee accurate positioning and to soften the shock of contact. Simulation results show the validity of the proposed method.

Virtual repulsive force field guided coordination for multi-telerobot collaboration

The Intelligent Systems Laboratory (ISL) has been developing coordinated control technologies for multitelerobot collaboration, in a common environment remotely controlled from multiple operators physically at a distance from each other. We have built a test bed and conducted a series of experiments, where we learned more about how the transmission delay over the network deteriorates the performance of telerobots. Previously, to overcome the problems arising from the throughput of the network such as the operators delayed visual perception, we have suggested several coordination approaches in the local operator site. Likewise, this paper discusses the use of virtual repulsive force field in the online predictive simulator to assist the operator to cope with the collision between telerobots in remote environments. In the test bed, the operators control their master robot to get remote telerobots to work cooperatively with the other telerobots in a task. Specifically, the operator detects a priori the possibility of collision in the predictive simulator that runs in near real-time and the use of virtual force field prevents the telerobots from coming into collision. We have demonstrated various tasks by two telerobots and two operators via an Ethernet local area network (LAN) subject to simulated communication delays and evaluated the validity of the virtual force field guided approach in multi-operator-multi-robot (MOMR) tele-collaboration.