Development of Virtual Factory Using Supervisory Control Theory

设想一个有六条腿的机器人在泥滩上行走，收集环境数据。在PARI(港口和机场研究所)，这样的机器人已经开发了3年。我们还使用6个CPU的MINDSTORMS实现了它的原型，如图所示。在控制系统的设计中，我们需要两种控制器：(1)伺服控制器，用于执行每个腿的每个关节发出的命令；(2)步态控制器，用于发出命令，以协调六条腿。在本文中，我们关注的是后一种情况。众所周知，步态是通过三脚架法顺利实现的。然而，在紧急情况下，为了避开一些障碍，一条腿可能会与下一条腿发生争执。由于存在大量突发事件驱动的复杂情况，用常规的三脚架方法生成多个情况下的运动数据不能很好地解决这一问题。在我们看来，这个问题应该被看作一个离散事件驱动系统(DES)控制问题。通过以上讨论，我们将DES控制理论应用于机器人系统(即由机器组成的制造系统)的监督控制器设计。然而，通常情况下，DES控制器的计算很难手工计算，这意味着有必要开发一种计算机辅助设计工具。本文介绍了我们基于C.G.Cassandras和S.LaFortune的教材，用MatLab开发的DES分析和综合工具箱，并展示了它在狭小空间中两台机器工作的避碰问题中的应用。利用MINDSTORMS和Real-Time shop Embedded Coder成功地完成了实验实现。

Consider a robot with six legs to walk around a mudflat for collecting environmental data. In PARI (The Port and Airport Research Institute), such a robot has been developed for the last 3 years. We have also realized its prototype using MINDSTORMS with six CPUs as shown. In the control system design, we need the two kinds of controllers, which are (1) servo controller for following a command given for each joint in each leg, and (2) gait controller to give the command to collaborate the six legs. In the paper, we are concerned with the latter case. It is well known that the gait is smoothly realized by the tripod method. However, in an emergency case to avoid some obstacle, there is a possibility that the one leg would get into a hassle with the next legs. The problem could not be solved very well by the ordinary way of generating the motion data of tripod method for several cases because there are a number of complicate cases driven by unexpected events. In our opinion, the problem should be treated as a DES (Discrete Event-driven System) control problem. From the above discussion, we are motivated to apply DES control theory to supervisory controller design for a system of robots (legs in the above), that is, a manufacturing system consisting of machines. In general, however, it is hard to calculate DES controllers by hand calculation, which means the necessity to develop a computer-aided design tool. In the paper, we present DES Analysis and Synthesis Toolbox that we developed as a collection of our original M-files using MATLAB based on the textbook by C.G.Cassandras and S.Lafortune, and show its application to a collision avoidance problem related to two machines working in a narrow space. The experimental implementation was successfully done by utilizing MINDSTORMS and Real-Time Workshop Embedded Coder.