Manufacturing Cell Monitoring Process

This paper describes all the manufacturing cell monitoring process particularities, and its several features. It is also done a brief presentation of the data structure used to monitor the manufacturing cell status, and it is explained its achievement and its philosophy by a complete flowchart. 1.Introduction and brief description The monitoring process of the manufacturing cell deals with the visualisation in real time of the manufacturing orders evolution, which are running at the moment, as well as the current state of the several machines (Kondia, Lealde and Kuka). Figure 1 Monitor appearance For each manufacturing order we can see the time spent in the last states, as well as the time spent in the current state. In a moment, we can have a maximum of 2 orders (see figure 1). When an order finishes, all the status times are added, and it is shown the total execution time. At that moment, all the information about that order are transferred to a display zone called “Last Order Parameters”, liberating the display zone that was occupied by that ended order. Those information are the order’s identification, the machine associated with that order, the time spent in the several states (processing, waiting for container, waiting for robot, loading, machining, piece turning around, waiting for robot to make the unload or the turning around operation, waiting for container to unload and unloading) and the total execution time. Synchronised with the order’s evolution, it is possible to observe the machine ́s status and associate them with the orders. For instance (see figure 1): while a piece is being loaded in the Lealde by the Kuka robot, we can see in the “Loading” state of an hipotetic order “pd001op04”, the time running, and at the same time, observe that the Lealde’s state is “Loading” and that the Kuka’s state is also “Loading”, and observe on the bottom of these messages “Executing Order: pd001op04”. Simultaneously, it exists a display’s zone called “System Messages”, where are shown all the error and warning messages, associated with possible manufacturing cell controller abnormal situations, as file opening errors, MMS errors, password incorrect introducing, and so on. This zone has the capacity to show the eight most recent messages. Another feature of this monitoring process is the “Command Editor”, which makes possible to send commands by the user to the main controller (in a mailbox), after the introduction of the security password. This editor permits, for instance, stop a machine, stop the manufacturing cell, make a setup or alter the security password. When the user strikes any key, the monitoring process creates automatically a child process, that begins by verifying if the command is valid. If it is not valid, it is generated a related error message, and the child process kills itself. If it is valid, the user must insert a password. If it doesn’t exist any password selected, the user must insert one before the execution of any other command, otherwise it is generated an error, and the child process kills itself. If the user takes more than 20 seconds on entering the password, it is generated an error, and the child process kills itself. After the introduction of the correct password, it is sent a message in a mailbox to the main controller, except if the command is an introduction of the first password, or a simply alteration of the current. The child kills itself in both situations. While the child process of the command editor is executing its own tasks, the monitoring process continues its job, altering its variables, which are a virtual image of the manufacturing cell status. As soon as the child process finishes, the monitoring process refreshes all the display. If the child process doesn’t exist, any alteration in the manufacturing cell can be observed in the display, in real time. 2. Programmation strategiy used in the monitoring process 2.1 Messages types changed between main controller and monitoring processes The messages sent by the main controller to the monitoring process may be grouped into three classes, according to their semantics: 1. an order that is running on the manufacturing cell changed its actual status; 2. an system error or warning occurred (problem on opening a file, for example); 3. the manufacturing cell controller is going down. The message is composed of a structure of type t_mensagem, declared as follows: typedef struct t_mensagem{ int num1; int num2; int num3; int label_erro; char frase[50]; } t_mensagem; and a variable “mtype” of type long. The resulting message is a structure of type msgbuf1:. typedef struct msgbuf1{ long mtype; t_mensagem mensagem; } msgbuf1;