REMOTE ROBOT CONTROL AND HIGH AVAILABILITY

Silvia Anton, Florin Daniel Anton and Theodor Borangiu

University Politehnica of Bucharest, Dept. of Automation and Applied Informatics

313 Spl. Independentei, sector 6, RO-060032, Bucharest, Romania

Keywords: Networked robotics, high availability, remote control, flexible manufacturing systems, robot vision.

Abstract: Nowadays production flows are modular, each module in the enterprise being specialized and used to

achieve a particular task. In many cases the modules are connected and materials are sequentially processed

in each module resulting a final, unique product or assembly. One typical such production module is a

flexible cell/system using multiple robots. In this structure, providing continuous service for applications is

a key component of a successful robotized implementing of manufacturing. High availability (HA) is one of

the components contributing to continuous service provision for applications, by masking or eliminating

both planned and unplanned systems and application downtime. A high availability solution in robotized

manufacturing provides automated failure detection, diagnosis, application recovery, and node (robot

controller) re integration. The paper describes a platform which is a software product designed to control

and supervise multiple robot-vision controllers using remote connections with a number of Adept

Technology V+ controllers configured to use a high availability implementation, either located in a local

network or via Internet.

1 INTRODUCTION

In a robotized flexible manufacturing cell, robot (-

vision) controllers are masters over local

workstations or cells, because robot manipulators

connect two important material flows: the

processing flow and the transportation flow. One

solution to integrate these two flows with on-line

quality control in the manufacturing module, further

networked with the design and planning modules, is

to adopt a unified feature-based description of parts

and assemblies, technological operations, geometric

& surface quality control, grasping and manipulating

(Tomas Balibrea, et al., 1997).

The system is configured for high availability .

HA systems are a combination of hardware and

software components configured to work together to

ensure automated recovery in case of failure with a

minimal acceptable downtime (Harris et. al., 2004).

2 THE STRUCTURE OF THE

SYSTEM

The system is composed by the following

applications (Figure 1):

The Server Application (SA): Remote visual

control and monitoring of multiple robot controllers

from mobile and stationary matrix cameras.

• Visual control: the Server Application supports

almost all V+ and AdeptVision program

instructions and monitor commands.

• Monitoring: a Monitoring/Treatment scheme can

be defined for each Client/Station. For each client

a list of events and controller variables to be

monitored according to a user-definable timing

and precedence, and reacted at by user-definable

actions/sequences can be specified in an

Automatic Treatment Window.

• Communication management: the Server

Application manages the communication with the

robot controllers and cameras, transfers real-time

images from the cameras observing the robot

workplace and production environment, reports

status information, stores in a database and

displays images taken by the robot camera.

The eClients Applications (eCA): Java

applications running in web browsers. They provide

portal services and the connection of networked

production agents: image data and RV program /

report management; real-time robot control and cell /

workplace observation. The eCA are composed by

two applications:

229

Anton S., Daniel Anton F. and Borangiu T. (2008).

REMOTE ROBOT CONTROL AND HIGH AVAILABILITY.

In Proceedings of the Fifth International Conference on Informatics in Control, Automation and Robotics - RA, pages 229-232

DOI: 10.5220/0001507002290232

 SciTePress

Figure 1: The System Structure.

• one application which has the function of

retrieving the images from the observation

cameras and display them in real-time and also

gives the user the possibility to change the

orientation and zoom factor of the cameras.

• the second application is a VNC client.

The VNC viewer is a web teleoperation

application which can be executed into a web

browser. The application connects to the Domino

web server which makes a secure connection using a

TCP/IP tunnel with a server having a private IP

address, which cannot be accessed from internet but

only using the Domino server.

The private IP machine has a VNC server that

exports the display, and also the teleoperation

application. Using the exported display the user can

view and use the application as when the application

runs on his own computer. The access is made using

a username and a password, process managed by the

Domino server.

3 ACCESSING THE SYSTEM

To have access to the system, a user must have a

username and a valid password to enter in the

system. First the user must access the portal site

using a java aware browser (like Internet Explorer,

Opera, Firefox, with the JRE installed).

The portal is structured in two zones:

• one zone is a public zone which contains all the

documentation, tutorials courses and so on...,

needed by users to learn how to use the system

this part of the portal can be accessed by anyone.

• and a private zone where the access is based on

username and password. The private zone gives

access to the eClients for teleoperation purposes.

After entering the correct username and

password, the user is allowed in the system and has

access to a the teleoperation application which is a

menu driven interface which allows him to interact

with the system (see Figure 2).

The teleoperation application is composed by

two windows:

A command window where the user can select

the robot system which he want to control and issue

commands from the command line or activate the

vision window.

The robot stations are commanded using the

command line and the menus. When a client is

connected, the IP address is checked and if the client

is accepted, the name attached to the IP address is

added to a drop down list from which the user can

select what client he wishes to command. When a

client who has a video camera attached the VISION

button is enabled and if it is pressed the VISION

Window will open.

From the VISION window, vision commands

can be issued by selecting the wanted actions from

the menus. The most important functions are:

• selecting the physical and virtual cameras, and

the virtual image buffers;

• selecting the display mode and the resolution;

• image acquisition;

• issuing primary operations;

• displaying the vision system status;

training models;

• switches and parameters configuration for

virtual camera set-up.

ICINCO 2008 - International Conference on Informatics in Control, Automation and Robotics

230

Figure 2: Accessing the system.

4 SOLUTION IMPLEMENTING

FOR NETWORKED ROBOTS

In order to implement the solution on a network of

robots, first a shared storage is needed, which must

be reached by any robot controller from the cluster.

The file system from the storage is limited to

NFS by the operating system of the robots. Five

Adept robot manipulators were considered, each one

having its own multitasking controller.

For the proposed architecture, there is no option

to use a directly connected shared storage, because

Adept robot controllers do not support a Fiber

Channel Host Bus Adapter (HBA). Also the storage

must be high available, because it is a single point of

failure for the Fabrication Cluster (FC).

Due to these constraints, the solution was to use

a High Availability cluster to provide the shared

storage option (NFS Cluster), and another cluster

composed by Adept Controllers which will use the

NFS service provided by the NFS Cluster (Figure 3).

The NFS cluster is composed by two identical IBM

xSeries 345 servers, and a DS4100 storage.

The storage contains a volume named Quorum

which is used by the NFS cluster for communication

between nodes, and a NFS volume which is exported

by the NFS service which runs in the NFS cluster.

The servers have each interface (network, serial, and

HBA) duplicated to assure redundancy (Anton et al.,

2006; Borangiu et al., 2006).

There are three communication routes: the first

route is the Ethernet network, the second is the

Quorum volume and the last communication route is

the serial line. If the NFS cluster detects a

malfunction of one of the nodes and if this node was

the node which served the NFS service the cluster is

reconfiguring as follows:

1. The server which is still running writes in the

Quorum volume which is taking the functions of

the NFS server, then

2. Mounts the NFS volume, then

3. Takes the IP of the other server and

4. Starts the NFS service.

The Fabrication Cluster can be composed by at

least two robot controllers (nodes) – group leader

(GL) and a common node. The nodes have resources

like: robot manipulators (with attributes like:

collision detection, current robot position, etc...),

serial lines, Ethernet adapter, variables, programs,

NFS file system. The NFS file system is used to

store programs, log files and status files. The

programs are stored on NFS to make them available

to all controllers, the log files are used to discover

the causes of failure and the status files are used to

know the last state of a controller.

In the event of a node failure, the production

flow is interrupted. In this case, if there is a

connection between the affected node and the group

leader, the leader will be informed and the GL takes

the necessary actions to remove the node from the

cluster. The GL also reconfigures the cluster so the

fabrication process will continue.

REMOTE ROBOT CONTROL AND HIGH AVAILABILITY

231

Figure 3: Implementing the high availability solution for the networked robotic system.

5 CONCLUSIONS

The project was started at the end of 2005 as part of

the P.R.I.C. research program and is in the final

stage of development.

The research project will provide a

communication and collaboration portal solution for

linking the existing pilot platform with multiple V+

industrial robot-vision controllers from Adept

Technology located in four University Labs from

Romania. This will allow teachers to train their

student using robots and expensive devices which

they do not dispose, and allow students to practice

their skills using specialised labs without

geographical barriers, and even from home. Also the

portal will allow team training and research due to

the messaging feature introduced by Domino.

The high availability solution presented in this

paper is worth to be considered in environments

where the production structure has the possibility to

reconfigure, and where the manufacturing must

assure a continuous production flow at batch level.

The advantages of the proposed solution are that

the structure provides a high availability robotized

work structure with a insignificant downtime.

The project is under development and can be

accessed at: http://pric.cimr.pub.ro.

REFERENCES

Anton F., D., Borangiu, Th., Tunaru, S., Dogar, A., and S.

Gheorghiu, 2006. Remote Monitoring and Control of a

Robotized Fault Tolerant Workcell, Proc. of the 12

IFAC Sympos. on Information Control Problems in

Manufacturing INCOM'06, Elsevier.

Borangiu, Th., Anton F., D., Tunaru, S., and A. Dogar,

2006. A Holonic Fault Tolerant Manufacturing

Platform with Multiple Robots, Proc. of 15

Int.

Workshop on Robotics in Alpe-Adria-Danube Region

RAAD 2006.

Harris, N., Armingaud, F., Belardi, M., Hunt, C., Lima,

M., Malchisky Jr., W., Ruibal, J., R. and J. Taylor,

2004. Linux Handbook: A guide to IBM Linux

Solutions and Resources, IBM Int. Technical Support

Organization, 2

Edition.

Tomas Balibrea, L.M., L.A. Gonzales Contreras and M.

Manu (1997). Object Oriented Model of an Open

Communication Architecture for Flexible

Manufacturing Control, Computer Science 1333 -

Computer Aided System Theory, pp.292-300,

EUROCAST ’97, Berlin.

ICINCO 2008 - International Conference on Informatics in Control, Automation and Robotics

232