Control of an automated storage and retrieval system

The Robotics and Automation Laboratory at Virginia Polytechnic Institute and State University contains a Flexible Machining and Assembly System (FMAS) and an Automated Storage and Retrieval System (AS/RS). These systems were developed for educational purposes to emulate a typical flexible manufacturing process in industry. The AS/RS hardware was designed and constructed in a previous project by Mark Eaglesham. His project consisted of hardware development only and did not include control system development.

The objective of this project is to design a set of software primitives to control the AS/RS. This set of primitive control sequences for the AS/RS could be used by future students to further develop the AS/RS control system at the device control level or to integrate the AS/RS with the FMAS at the workcell control level. The set of control primitives were developed in Relay Ladder Logic (RLL) on a Texas Instruments 565 Programmable Logic Controller (PLC). The set of primitives include the following functions: initialize the system, store a pallet, retrieve a pallet, move to a specified location, and shutdown the system.

A communications dialog was developed for command and control interaction between the PLC and the workcell control computer. This protocol includes various functions to manage the AS/RS's operations. These functions commands from the workcell controller indicating what operation is needed and response from the AS/RS indicating its status and system error messages.

In order to test the AS/RS a program to simulate the workcell controller was developed. This project report includes a description of a test program developed using QuickC. Due to hardware difficulties, this test program was not implemented. The AS/RS primitives were tested using Texas Instrument's TISOFT RLL development and monitoring software package.