机械设计的基本原理1.1

Design Contests

设计竞赛

Since the 1960’s, sophomores in MIT’s Department of Mechanical Engineering have been taking the hands-on Introduction to Design course“2.70” (which evolved into course 2.007 in 1995). The course teaches the fundamentals of mechanical design process and machine elements via hands-on engineering challenges. Lectures assume students have done the reading (this book!) so they can focus on potential solutions to the homework design problems. The homework helps guide the students the design and build a remote controlled machine for use in an end-of-term celebration (contest!).

自从上世纪60年代以来，MIT的大二学生就已经开始学习机械设计入门的实验课程“2.70”（后来于1995年变成了2.007）。该课程不仅教授机械设计及其过程的基本原理，并且还通过实验类的实际问题帮助学生掌握这些理论知识。本课程要求学生们预先阅读完教材（也就是本书），这样学生们就可以集中精力解决家庭作业中的一些设计问题。家庭作业的目的，主要还是为了指导学生实施设计，从而搭建自己的遥控机器人用以学期末的设计竞赛。

A new contest is created each year by students who have just completed the class, and they use the design process learned in class. About 10% of the previous year’s students become current year’s Undergraduate Assistants (UAs), who help run the class, and this helps generate a feeling of student ownership. Student participation is a key element in the design of good contests, for what teachers may think is most excellent, students may find boring. It is critical to incite students’ passion and sense of ownership, while providing a rich environment for teaching fundamental principles. It is also important for students and teachers alike to have fun! 

每年的设计竞赛都是由上一届参赛的学生来设计的。通过设计竞赛，他们也把在课程中学到的原理应用于竞赛设计本身。大约10%的上一届学生会变成下一届的本科助教，有他们的帮助才使得整个课程成功进行。他们的参与，也使得学生们的主人翁意识凸显，提升了学习氛围。有时候对于教师来说，设计竞赛的主意很棒，但是学生们可能会有抵触情绪，觉得竞赛非常无聊。所以，激发和引导学生的兴趣以及主动性就变得非常重要，只有在良好的氛围下，学生才能好好学习机械设计的基本原理，并且师生还能寓教于乐。

To help illustrate the principles and ideas presented in this text, the 2002 MIT 2.007 design contest The MIT and the Pendulum will be used as a case study. In this type of design contest, the playing field has a variety of obstacles and scoring methods, and students drive their radio controlled machines in one-on-one contests to see who can score the most points. 

为了便于理解，现拿2002年的设计比赛作为案例说明。学生们必须设计一种遥控的机器人在固定的场地进行一对一的竞赛，得分多的人胜出。场地中会有各种各样的障碍物，得分方式也各有不同。

Put yourself into the mind of a student creating a machine for The MIT and the Pendulum, which is of course a geek twist on Poe’s The Pit and the Pendulum. The table is symmetrical with a scoring bin on each end and a rigid pendulum on each side in the middle of the table. Each pendulum is made from a square hollow plastic tube half-filled with blue street hockey balls. Its center of gravity is below its pivot point either with or without the balls. On the table, there are also street hockey pucks and balls. 

赶快投入到设计比赛中来吧，像极客一样“反转”爱伦.坡的《陷阱与钟摆》。竞赛场地是对称的长方形，前后两端各有一个得分框，中间位置的左右两端各有一个钟摆。每个钟摆是由方形截面的塑料管做成的，其中盛放着半满的曲棍球。无论有球还是无球，钟摆的重心永远低于其旋转中心。此外，场地桌面上也会有一些小球。

The pendulums start hanging straight down in the middle of the designated starting area for each contest machine (robot). As shown, your score is a function of the total mass of balls and pucks collected in the bins and the total angular distance traveled on the pendulum. Each term of the scoring equation has a small constant to increase the richness of potential winning strategies! 

在比赛开始前，钟摆竖直立在双方机器人的出发点处。如图所示，计分方式和得分框内球的质量以及钟摆的旋转角度有关。为了该竞赛的丰富性，计分公式中增加了一些常数，来保证得分方式的多样性。

The question is how to use the pendulum to your advantage, without your machine getting bashed by the swinging pendulum? There are a lot of balls in the pendulum and if it is swung just right, the balls will empty and bounce into the end scoring bin. 

问题就是，你的机器人将怎么利用该场地中的钟摆优势，而不是被钟摆运动阻挡。此外，钟摆中有很多小球，如果钟摆摆动得当，可以把所有的小球弹回你的得分框内。

What Would You Do!? 

你会怎么设计你的机器人呢？