Page 126 - Robot Design Handbook ROBOCON Malaysia 2019

When ‘startsignal’ function is executed, the led will light up for two seconds, its function is

to give signal to the controller and judges and provides enough time for the participants
leaving the game field. After that, the MR2 will perform the ‘forward (100)’ function, that

is the MR2 will move 100 steps forward. The ‘gamefield1’, gamefield1retry’, ‘gamefield2’,
‘gamefield3’ and ‘gamefield4’ functions are used based on the situations and game fields

that the MR2 are placed. The functions are programmed to tell the MR2 that how many

steps to be moved forward, and when to turn right or left. Figure 6 shows the flow-chart for
resetting the MR2.

3.0 ROBOT TESTING

The design of the MR2 was done using SOLIDWORKS, a CAD software. The
motion of the robot was simulated using the software to ensure the smooth movement of,

and no restriction with its body part. The overall size of the robot is designed to fulfil the

dimension stated in the rulebook.

The design of the MR2 is mainly based on the rotation of four “legs” to move

forward. Each “legs” has two contact points with the ground that could easily cross the
obstacles. The joint of the “legs” is 80 mm and we programmed the two of the “legs” move

in phase and the other two at 180 degree out of phase. Theoretically, this s a total of 320mm
of distance travelled in a complete cycle by all “legs”. The two most outer “legs” is distanced

600mm so that turning angle for one cycle is approximately 30 degrees from the centre of
rotation.

However, in practice, the distance travelled differs slightly from the estimation due
to the slipping of the “legs” as the motor rotate at high speed. We have collected data from

several trials on adjusting the speed of the robot to compromise the slipping effect so that

we optimised the effective distance travelled in the shortest time possible. From the
experiment, we found that the best duty cycle for pulse width modulation (PWM) given to

the motor is 65% which is about 7.8 V out of 12 V fed to the power window. Table 2 shows
the comparison between theoretical distance and the actual travelled distance of the MR2.

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