Home‎ > ‎

Dynamic controller module

a)   Serial communication

    To establish serial communication successfully between the PC and the robot’s built-in controller, some of the I/O parameters on the robot’s X-SEL controller need to be edited using the “PC interface software for X-SEL controller”. The figure below shows a snapshot of the I/O parameter window on the software.

 

    The table below lists the X-SEL controller remote communication parameters and their set values. A USB cable is used to connect the PC to the robot.

 

 

Parameter No.

Value

Description

90

2

Select IAI Protocol B

91

153

Set the station number to 153

92

2

Set the baud rate to 38.4 kbps

93

8

Set the data length to 8

94

1

Set the stop bit length to 1

95

0

Set the parity type to None

 

The command sent from the PC has to follow the format shown in the figure below. 

For example, if we want to move the axes to home position, the command string

‘!992330700000000@@’ will be sent,

and if we want to move X and Y axes to coordinates 200 and 200 mm, the command string 

‘!9923403001E001E012C00030D4000030D40@@’ will be sent.

The X-SEL controller commands are described in [ X-SEL Serial Communication Protocol Specification,IAI AMERICA Inc., Ninth Edition, 2010].

 

Header

(start)

Station

number

Massage ID

Content of command

SC

(checksum)

CR

(End)

LF

(End)

 

 

b)   Controlling program

 

The controller program is designed to work as an open-loop control system. In this system we do not request the current position from the robot. By doing so we reduced the system complexity and the required time to complete the process. In general the control program is designed to do the following:

 

·         Establish serial communication with the robot.

·         Turn on the axes’ motors.

·         Move the end-effector to home position.

·         Load the image matrix file.

·         Scan the matrix and draw the picture.

 The scanning of the binary image matrix is done row by row. Based on the pixel value from the matrix, a command string is dynamically generated and sent to the robot. The pen is moved down on the paper for every black pixel and moved up for every white pixel, unless the pen has been down or up previously. The next flowchart demonstrates the algorithm of the control program. 

 
And the table below explains the axes’ arrangement.

Robot axis

Function

Target

X

Moving the paper forward and backward

Pictures’ rows

Y

Moving the pen right and left

Pictures’ columns

Z

Moving the pen up and down

Pen down and up

The robot speed is chosen to be coordinated with pauses in the control program. These pauses will allow the previous command to be executed before the next command is sent. The table able below presents the moving characteristics of the commands.

 

Speed

Acceleration

Deceleration

500 mm/s

0.3G

0.3G

 

Comments