Shuttleworth Conveyor

The Shuttleworth conveyor is a roller-type conveyor system for material handling and is presently being used in the TAMCAM laboratory. The conveyor has a set of closed loop paths along which the pallets travel. The flow of the pallets, which may be empty or loaded with a part to be processed, can be guided by some hardware devices available on the conveyor system such as:

• Infrared eyes
• Lift and Transfer racks
• Blade stops
• Proximity switches
• Pin stops

The conveyor is divided into 4 lanes with alternating direction of flow. There are 8 stations at which the pallets can be brought to a halt with the blade stops. The 4 stations in the 2 outer lanes are located in proximity to the work cells and the robots such that the part can be picked off the pallet by the robot and loaded on the workcell. After the processing of the part is completed in the work cell, the robot can unload the processed part onto the empty pallet at the respective station. There are lift and transfer racks available on the two ends and one in the middle. These facilitate the movement of the pallets in a direction perpendicular to the movement of the conveyor.

The Shuttleworth conveyor is controlled by a Programmable Logic Controller (PLC). The PLC used is a MODICON PLC Type 785 E manufactured by AEG Automation. The PLC is programmed using ladder logic rungs, a powerful and graphical language that emulates relay-equivalent symbology and this is done using the MODSOFT software package. The instructions are drawn from a large set of calculation, data transfer(DX), matrix and special application functions.

Specifications:

Hardware Implementation - Slot mounted
Logic Solve (ms/Kword) - 1.5
CPU size - 24 bits
User Logic Size - 16K/32K

State RAM
Regs - 9999
Discretes - 8192

Maximum I/O Bits/ Drop - 512in/ 512out
Maximum I/O Bits/ System - 16384in/16384out
Total Discrete I/O - 8192in/8192out
Max. Drops/ System - 1 Local, 31 Remote

Control Architecture:

The architecture of the controller is as follows:

• A memory section that stores user logic, state RAM, and system overhead in a battery-backed CMOS RAM and holds the system's Executive firmware in a non-volatile ROM.
• A CPU section that solves the user logic program based on the current input values in the state RAM, then updates the output values in the state RAM.
• An I/O processing section that directs the flow of signals from the input modules to the state RAM and provides a path over which the output signals from the CPU's logic solve are sent to the output modules.
• A communications section that provides one or more port interfaces. These interfaces allow the controller to communicate with programmable panels, host computers, hand-held diagnostic tools, and other nodes on a communication network.

The communication with the PLC is established from a PC through a OMEGA 24 bit Parallel Digital I/O Interface. The features of the I/O board are as follows:

• 24 TTL/ DTL Digital I/O lines
• 12V, 5V power from IBM PC
• Uni-directional, Bi-directional strobed I/O
• Interrupt Handling
• Handshaking

Last updated on Monday November 08, 1999.