Development of Architectures for Internet Telerobotics Systems

This paper presents our experience in developing and implementing Internet telerobotics system. Internet telerobotics system refers to a robot system controlled and monitored remotely through the Internet. A robot manipulator with five degrees of freedom, called Mentor, is employed. Client-server architecture is chosen as a platform for our Internet telerobotics system. Three generations of telerobotics systems have evolved in this research. The first generation was based on CGI and two tiered architectures, where a client presents a Graphical User Interface to the user, and utilizes the user＇s data entry and actions to perform requests to robot server running on a different machine. The second generation was developed using Java. We also employ Java 3D for creating and manipulating 3D geometry of manipulator links, and for constructing the structures used in rendering that geometry, resulting in 3D robot movement simulation presented to the users （clients） through their web browser. Recent development in our Internet telerobotics includes object recognition through image captured by a camera, which poses challenging problem, giving the undeterministic latency of the Internet. The third generation is centered around the use of CORBA for development platform of distributed internet telerobotics system, aimed at distributing task of telerobotics system.

Multi-modal human-machine interface of a telerobotic system for remote arc welding

In telerobotic system for remote welding, human-machine interface is one of the most important factor for enhancing capability and efficiency. This paper presents an architecture design of human-machine interface for welding telerobotic system： welding multi-modal human-machine interface. The human-machine interface integrated several control modes, which are namely shared control, teleteaching, supervisory control and local autonomous control. Space mouse, panoramic vision camera and graphics simulation system are also integrated into the human-machine interface for welding teleoperation. Finally, weld seam tracing and welding experiments of U-shape seam are performed by these control modes respectively. The results show that the system has better performance of human-machine interaction and complexity environment welding.

Generation of triangle mesh surface from the disparity map for telerobotic welding

3D reconstruction of environment and weld workpiece can provide geometrical model for telerobotic welding and improve its intelligence. A novel framework of spacetime stereo is employed to overcome the lack of texture of the weld workpiece and obtain subpixel disparity map of the scene. Anisotropic diffusion is adopted to smooth the original subpixel disparity map in order to reduce the noise while preserving the depth discontinuity. A simple algorithm of generation triangle mesh surface from the disparity map of the spucetime stereo is presented. The experimental results of real weld scenes are shown.

Internet-based event synchronization communication driven telerobotics

Based on QoS (quality of service) parameters: time delay, jitter, bandwidth and package loss. As time delay in the Internet is variable, it is hard to compensate it by traditional methods. Event synchronization communication driven method is proposed to overcome the negative effects induced by time delay. This method is a non-time based method and it can get rid of the effects of time in the control loop of telerobotics. Stability, transparency and synchronization can be maintained in it by event-driven method. Multimodal enhanced telerobotics is put forward with its feedback including force, video, audio and temperature etc. The use of multimodal feedback improves the efficiency and safety of the whole system. Synchronization in multimodal feedback is hard to ensure and event-driven method is also good for it. Experiments on an Internet-based shaft-hole assemblage system show good results by using event synchronization communication driven method and UDP protocol.

Stability Analysis and Performance Evaluation of Delayed Bilateral Telerobotic Systems over a Lossy Communication Channel

The focus of this paper is to address a novel control technique for stability and transparency analysis of bilateral telerobotic systems in the presence of data loss and time delay in the communication channel. Different control strategies have been reported to compensate the effects of time delay in the communication channel;however, most of them result in poor performance under data loss. First, a model for data loss is proposed using a finite series representation of a set of periodic continuous pulses.To improve the performance and data reconstruction, a holder circuits is also introduced. The passivity of the overall system is provided via the wave variable technique based on the proposed model for the data loss. The stability analysis of the system is then derived using the Lyapunov theorem under the time delay and the data loss. Finally, experimental results are given to illustrate the capability of the proposed control technique.

Modeling and Control of Telerobotic Systemswith Time-delays

Telerobotic systems become more and more important due to emerging hi-technologyand practical requirement in modern society. This paper studies+ and integrates the modeling, taskscheduling, action planning and control of telerobot systems. Such hybrid syStems often involve coalmunication, command and control, and are so complex that no efficient and simple method could befound to analyze and design systems. To increase the efficiency, reliability and safety oftelrobot syStems,the consideration of task scheduling and action planning in a unified framework could be an importantstep. The discrete-event dynamics is modeled as a linear state-spare equation in Mad-Algebra sense.Performance evaluation can be carried out efficiently. Then analysis about time-delay continuous-timedynamics is given for the scheduling and control, which shows that, to simplify the design procedure,it is necessary to present a good delay scheduling, for example, by changing multi-time-delays to singleones in advance. Robustness conditions are derived using graph theory for dipcrete-event dynamics andmatrix analysis for continuous-time dynamics.

NEURAL NETWORK SMITH PREDICTIVE CONTROL FOR TELEROBOTS WITH TIME DELAY

A neural network Smith predictive control strategy is proposed to deal with inpu t and feedback time delays in telerobot systems. The delay time is assumed to b e invariant and unknown. The proposed control structure consists of a slave syst em and a master controller. In the slave system, a recurrent neural network (RNN ) with on-line weight tuning algorithm is employed to approximate the dynamics of the time-delay-free nonlinear plant, which is used to linearize the slave s ystem. The master controller is a Smith predictor for the linearized slave syste m, which provides prediction and maintains the desirable tracking performance. S tability propriety is guaranteed based on the Lyapunov method. A simulation of a two-link robotic manipulator is provided to illustrate the effectiveness of th e proposed control strategy.

Identification and Control of Bilateral Telerobot with Time Delay Using Genetic Algorithm

Bilateral telerobot can help human operator feel and control the remote pre unknown environment as if he/she is at the remote site, which is usually called “telepresence”. However, the transmission time delay between master manipulator and slave manipulator causes instability of the telerobot system and bad “telepresence” of human operator. In this paper, a new adaptive and passive control scheme based on active impedance matching is proposed to guarantee stability and transparency of the bilateral telerobot system. A genetic algorithm (GA) is used in this control scheme to directly identify parameters of the environment impedance.

Research on Master-slave Telerobot Force Telepresence Technology

A 3 DOF master-slave telerobot system is established for study on force telepresence technology. A force feedback and position control scheme is adopted in the bilateral force response control system,and force fidelity and controllability experiments demonstrate feasibility of the con-trol system.

An Internet-based Telerobot Design and Implementation

A PUMA562 robot has been connected to the Internet and can be controlled through the web browser. The remote user receives still images of robot workspace, coordinates and gripper state and can control the gripper to pick up blocks and place them to build a structure. An Internet server and a robot server were built to implement this telerobot system. This two-layer server architecture can be used in other Internet-based telerobot system without changing most part of the system.

HeterBot:A heterogeneous mobile manipulation robot for versatile operation

This study presents the overall architecture of HeterBot,a heterogeneous mobile manipulation robot developed in our lab,which is designed for versatile operation in hazardous environments.The most significant feature of HeterBot is the heterogeneous design created by adopting the idea of‘big arm+small arm’and‘big car+mini car’.This combination has the advantage of functional complementation,which achieves performance promotion in both locomotion and manipulation capabilities,making HeterBot distinguished from other mobile manipulation robots.Besides,multiple novel technologies are integrated into HeterBot to expand its versatility and ease of use,including Virtual Robot Experimentation Platform-based teleoperation,reconfigurable end effectors,laseraided grasping,and manipulation with customised tools.Experimental results validate the effectiveness of HeterBot in various locomotion and manipulation tasks.HeterBot displays huge potential in future applications,such as searching and rescue.

Control Schemes for Passive Teleoperation Systems over Wide Area Communication Networks with Time Varying Delay

In this paper,the problem of time varying telecommunication delays in passive teleoperation systems is addressed.The design comprises delayed position,velocity and position-velocity signals with the local position and velocity signals of the master and slave manipulators.Nonlinear adaptive control terms are employed locally to cope with uncertain parameters associated with the gravity loading vector of the master and slave manipulators.Lyapunov-Krasovskii function is employed for three methods to establish asymptotic tracking property of the closed loop teleoperation systems.The stability analysis is derived for both symmetrical and unsymmetrical time varying delays in the forward and backward communication channel that connects the local and remote sites.Finally,evaluation results are presented to illustrate the efectiveness of the proposed design for real-time applications.