設計精確的微型操縱桿

　　便攜式設備通常需要使用一個線性的兩軸位置傳感器或操縱桿，隨著便攜式設備的激增，這種傳感能力的需求也在增加。設計人員的任務是滿足關鍵性能要求，如靈敏度、精確度、低功耗和更平滑的操作，同時也降低成本、減小尺寸和增加諸如觸覺反饋等特性。

　　本文將介紹如何操縱桿功能之前推出的部分代碼需要設計一個低成本、移動設備敏感的操縱桿。

　　如何操縱桿功能

　　視頻游戲中常用的游戲桿由兩個正交的電位計組成，X和Y通過旋轉軸的機構運動，如圖1所示。這些工作很好，價格便宜，但相當大，并有明顯的鞭子圍繞中心位置。此外，電位器觸點容易受到環境因素的影響，從而產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.