设计精确的微型操纵杆

　　设计精确的微型操纵杆

　　便携式设备通常需要使用一个线性的两轴位置传感器或操纵杆，随着便携式设备的激增，这种传感能力的需求也在增加。设计人员的任务是满足关键性能要求，如灵敏度、精确度、低功耗和更平滑的操作，同时也降低成本、减小尺寸和增加诸如触觉反馈等特性。

　　本文将介绍如何操纵杆功能之前推出的部分代码需要设计一个低成本、移动设备敏感的操纵杆。

　　如何操纵杆功能

　　视频游戏中常用的游戏杆由两个正交的电位计组成，X和Y通过旋转轴的机构运动，如图1所示。这些工作很好，价格便宜，但相当大，并有明显的鞭子围绕中心位置。此外，电位器触点容易受到环境因素的影响，从而产生噪音并降低可靠性。

　　Figure 1： The 27800 from Parallax is a good example of a joystick that uses two rotational potentiometers mounted at right angles to each other. （Image source： Parallax）

　　The once ubiquitous “pointing sticks” embedded in PC laptop keyboards used force sensitive or strain gauge resistors as the sensing element （Figure 2）。 These resistors are placed on four sides of the stick. Moving the stick compresses one or more of the resistors changing their value. They are very small， reliable， and provide haptic force feedback that is proportional to displacement. Pressing down on the stick changes the value on all four resistors allowing for measurement of Z-axis displacement. The problem is that these pointing sticks are no longer manufactured in high volume. What is currently available is very expensive and can cost tens and even hundreds of dollars.