Pick & Place Using 6 DOF Robotic Arm

As the parts required for the Robotic Arm are available already, now we can start to design and built the second RA. This time we are going to built a 6 degrees of freedom RA. This RA will make full use of 6 pieces of Bizchip 13 kgcm torque servos as well as another 2 pieces of Futaba S3003 servos.

Design Concept
There would be two small conveyors that would be use to simulate the actual production conveyors. The first one is supposed to bring the moon cakes and stop at one position, waiting to be pick up by the RA. The second conveyor would carry the empty tray and stop at waiting position. Once both of the moon cake and tray are ready, the RA arm would be initiated from rest position to pick the moon cake and place it inside the tray. The process would continue on and on. In case of emergency, the RA would be reset to rest position and both of the conveyors would stop running. The whole RA body would use aluminum and the base would be moving on 4 roller weight distribution bearing taken from Tamiya ball caster. The gripper would use single movement as for the time being, the making of double gripper would require quite extensive mechanical job.

Design Objectives
The RA should be able to lift the moon cake load to about 260gm.
The RA should be fast enough to work in picking up the moon cake from one conveyor to another and place it inside a tray.
Whenever the emergency button is pressed, the RA should reset to rest position
The moon cake quality should not be affected by RA gripper

Design Constraints
Since the biggest servo could only lift 13kg for 1cm, thus if the shoulder is about to reach 50 cm, then the RA weight must be zero as the 260gm is the required load. Because of this, the weight of the RA should be minimized to allow maximum lifting capacity.
Due to this reason, we planned to use a couple of servos for shoulder as well as the elbow. For the rest of the freedoms, one servo is enough as the length is minimum.

6 DOF
The 6 degrees of freedom are :
i- Base
ii- Shoulder
iii- Elbow
iv-Wrist
v-Wrist Rotation
vi- Gripper

Softwares & Hardwares
As the previous RA, this RA would use Serial Servo Controller (SSC) to run the mechanism. Instead of running directly through a PC, this RA would use a PIC micro controller chip that has been programmed by EPICA hex code where the source code is being written using MicroCode. With this combination, the RA would only need a 9VDC for SSC and 6VDC for the RA servos to run.
As for laboratory prototype, the control of the small conveyors would be done by relays (MY4N & LY2) hardwires. These relays are wired in such a way that they use sensors as input and use their contacts to send signal to the RA to ON and OFF as well as to switch ON and OFF the small conveyors AUTOMATICALLY.
The DC box power supply would be used to supply the DC to the electronics components as well as the relays. As for the SSC, a separate 6VDC power supply would be used as the servos required a higher rating current to work efficiently.