Page 218 - Mechatronics for Safety, Security and Dependability in a New Era

Ch42-I044963.fm Page 202 Tuesday, August 1, 2006 3:57 PM
Ch42-I044963.fm
202
202 Page 202 Tuesday, August 1, 2006 3:57 PM
The objective of the present research is to develop an integrated process planning and scheduling system
applicable to the holonic manufacturing system. In the previous papers (3H<5) , integration of process planning and
scheduling was carried out, wherein the scheduling system for multi-products as a whole uses the process plan
information of a set of individual products to generate a suitable schedule. But, there is not any feedback
information from the scheduling system to the process planning system. This paper deals with the integration of
the process planning and the scheduling systems where there is a scheduler driven modification of the process
plans of the products. A systematic method is proposed to generate modified sequences of machining equipment
for the individual products based on the feedback information of the scheduling results, and to generate a modified
production schedule for the whole manufacturing system.

PROCESS PLANNING AND SCHEDULING

The process planning system generates suitable process plans for the individual products to be manufactured. The
process plans give suitable sequences of manufacturing equipment needed to manufacture the machining features
of the products, and machining time of the machining features. The scheduling system determines suitable
production schedules of manufacturing equipment in the HMS for manufacturing a set of products. The
production schedules give the loading sequences of the products to the manufacturing equipment and the starting
times of the individual machining processes of the products. The production schedules are verified based on the
objective functions such as the make span and the tardiness against due date.

SCHEDULING BY SCHEDULING HOLON

Input Information
The input information of the scheduling holon is summarized here. The following production management
information is the requimements to the scheduling process.
(1) Starting time and due time of job holons.
(2) Candidate machining sequence of machining features and candidate sequences of machining equipment.
(3) Machining time of machining features.
(4) Alternative machining equipment for each machining feature.
(5) Machining time by alternative machining equipment.

Objective Functions

This research deals concurrently with both the process planning of the individual jobs and the scheduling of all the
jobs to be manufactured in the HMS. The following objective functions are considered for the scheduling task of
(5)
theHMS .
(1) Make span: MS
(2) Total machining cost: TMC
(3) Weighted tardiness cost: WT