An autonomous robot playing the board game checkers

International Journal of Electrical Engineering Education, Jan 1998 by Zribi, M, Sung, E

4.4 The feeder

In order to set up the board or to change a seed to a 'king' seed, the robotic arm needs to pick the seeds easily and accurately. Two feeders are needed for the robot (one for 'man' and one for 'king'). In addition, two feeders are needed for the human player.

Several considerations were taken into account when designing the feeder. For example, the feeder must be able to store at least twelve seeds and the size of the feeder should be minimised because the workspace of the robot is limited.

In addition, only one seed must be present at the pick up point because the electromagnet is capable of picking up three seeds at once. After some experimentation, it was decided that a purely mechanical feeder could do the job. The designed feeder is very easy to use, see Fig. 5(a) and (b). To obtain a seed from the feeder, the push and pull method is used.

4.5 The solenoid

The picking up of a seed by the robotic arm is done by means of a solenoid. The seeds are modified so that a metal piece is embedded in each seed. When the solenoid is energised, the seed can be picked up because of the electromagnetic force generated by the solenoid. It should be noted that the energising and de-energising of the solenoid is controlled by the output relay of the controller of the robot.

4.6 Implementation of the HAND module

The main task of the HAND module is to move the appropriate seed from the starting position to the desired position. After the BRAIN has generated the appropriate move, a program will output it to the 8255 I/O card in binary form and in turn transfer the data to the controller. The ACL program will then decode the obtained data and instruct the robot to perform the movements as required by the BRAIN.

Several subroutines are needed to implement this module. A brief description of some of these subroutines is given next. The subroutine 'home' is used to bring the robot to the home position; the home position is the position where the camera will take the picture of the board. The subroutine 'set' is used to set the board intelligently. The BRAIN will identify the seeds left on the board after the game and will only replace and take away the necessary seeds. The subroutine 'setup' is called to set up an empty game board. The subroutine 'trans' transfers a seed from one point to another. This includes two types of movements: within the board movements and the clearing up of the seeds.

These two movements are similar; the only difference is the speed of the robot. The speed of the robot is different for the two moves because the distances travelled are very different. The 'read' subroutine gets the binary input data from the BRAIN and converts it to a decimal number. The calculated decimal value is then used in 'main'. The subroutine `change_king' is used to change seeds (from man to king). It should be noted that the human player is expected to change a 'man' to a 'king' by himself/herself. The subroutine `cass_on' is used to switch on the cassette player which will then play some background music. The subroutine `cass_oft" is used to switch off the cassette player.