As a logical step up of the Tic Tac Toe Playing Robotic Arm I built some years ago I have started building a Chess Playing Robot. The idea is to build not only a Robot Arm that play chess against a human but to add some other components to make the chess playing experience against a machine less dry and boring.
In addition to the Arm, the plan is to add an animatronic face of some sort for the robotic opponent. This face should mimic some behaviors of a real opponent, like tracking with its eyes the pieces being played and to express emotions like concentration when planning moves, happiness when winning and preoccupation when loosing.
Another component will consist of control levers that the human player can use to adjust the robot’s playing level and style on the fly and at any time during the game. For example if after the opening the human player feels that the robot opponent level is to high or to low then using the levers the robot’s level could be adjusted as desired.
There are many technical aspects that will need to be worked out at due time, like which method of chess piece detection will be used, will the robot arm use inverse kinematics or preprogrammed positions, which chess engine and computing platform to use, etc. but to start I will be concentrating first in building a strong and reliable robot arm capable of grabbing and manipulating any standard chess piece in a standard tournament size board.
The robotic arm will have 5 degree of freedom plus a gripper. I am starting the design from the end actuator (the gripper) and continuing with the wrist roll wrist pitch, elbow, shoulder swivel and arm sweep. By starting from the actuator I can evaluate at each step how much torque I need for each subsequent joint. This is important as this time the robot will not be constructed with just servos, it will have servos only for the gripper and wrist and dc motors with encoders for the elbow and shoulder.
For the gripper, after evaluating different mechanisms, like gears and rack and pinion, to convert the servo rotation action to linear action (for three fingers separated at 120 degrees) I settled for this simple design that seems to work very well as the gripper action is fast and the gripping force is strong enough to hold any standard chess piece even if it grabs it off centered or at different height.
The gripper uses one Hobbyking TurnigyTG9e Analog Micro Servo with 1.5kg/cm (4.8V) of Torque. All parts were 3D printed in PLA and assembled with M2.5 screws.
STL files at: http://www.thingiverse.com/thing:1322867
Next post in this series will show the wrist roll mechanism.