you may look for RF tags. These devices can be attached to each object and a second unit (ore more) will read/write the object properties. Then you can transfer them trough a serial port into your PLC/PC.
Start with GE's line of products and then you can expand your search after the tutorial phase.
I do have the following motion problem:
Let's supose that two belt conveyors (chained) are running at V1 and V2 (V1<V2). A parcels travels from CV1 to CV2. When reaches the junction point between conveyors, it will acelerate from V1 to V2. "t" is the requiered time to be fully...