All the mechanical systems I have designed and developed are based on levers, wheels and screws.

Arm
Basically it is a parallelogram made of aluminum strips, These aluminum strips remain parallel to each other, which allows the arm to move in forward and backward direction. This motion of arm is performed by a nut and a screw, which is derived by a powerful geared motor. This whole mechanism is fitted on anther U shaped strip, which can rotate at the angle of 180 Degrees to move the arm up and down. This operation is performed by another geared motor fitted under the arm.

Hand
Hand of the robot is an ordinary Laboratory iron stand's clamp, which is driven by a geared motor through a soft coiled spring.
 

Driving Wheel
Robot has 2 front wheels and a rear wheel. The rear wheel is responsible for driving the robot on the ground. Rear wheel is driven by a very high power geared motor which is directly connected by the rear wheel of robot. This rear wheel along with the driving motor is fitted on a U shaped clamp which can rotate along the X axis within an angle of 130 Degrees Approximately. This rotation is performed by another geared motor fitted above the rear wheel, which steers the robot. This high turning angle allows the robot to rotate at the angle of 360 Degrees while standing on the same place.