电子变速器控制，或者称为线控换挡（shift-by-wire），是汽车产业的一项最新技术，它可以替代传统的机械式控制系统。“线控”技术为汽车设计工程师和汽车驾驶者提供了许多优势。对于汽车设计团队来讲，线控换挡消除了像传统机械部件与变速箱联动的约束，从而实现了高度的设计自由度。这种设计的改进使驾驶者换挡变得轻松容易，比如说在停车时，驾驶者只需按一下开关就可以实现停车换挡。

线控换挡系统提高了燃油的效率，同时可以节省约5%以上的燃油。

线控换挡如何工作？
线控换挡齿轮的切换是由一个电机来驱动的。换挡需求通过改变齿轮实现，档位与齿轮间的数据通过一个霍尔效应传感器来记录。这些数据被安全的存储以防突然掉电的发生。如果数据丢失，系统就必须重新调整，齿轮选择也必须在重新校准后才能工作。

为什么使用F-RAM?
齿轮循环的计数必须被写入一个能够适应高频率操作的非易失性存储器内。F-RAM具有几乎无限次读写次数的特性，它是电子变速器系统的理想选择。

在变速箱内，齿轮切换会遇到高温环境，必须通过AEC-1级认证（(-40°C ~ 125°C)。F-RAM带有一个针对这个温度范围的低价加法器，而其他非易失性存储器技术带有更高价格的加法器。

联系F-RAM 应用工程师，发现如何应用F-RAM 改善您的汽车线控设计。
 
Email联系我们 framinfo@ramtron.com 或电话联系 719-481-7000.

一些具有特色的设置在车载导航设备上开始扩展。车载导航系统的最新趋势是在计划路线上提供动态信息或是通过服务器连接显示驾驶员目前的环境。关于导航系统可以提供交通信息和天气预报的功能已被人熟知。导航系统的下一步设计是能够提供周围环境的信息，如餐馆、旅游景点和活动。

一旦服务器连接被建立，导航系统与车载通信的范围将会扩大。当汽车遇到结冰的路面时，它的防抱死制动系统（ABS）和电子稳定控制系统将道路条件传送到导航系统上，同时通知服务器。服务器将会将路面情况通知给其它驾驶员。

为什么使用F-RAM?

• 存储车辆位置：非易失性F-RAM存储器运用了增强型定位技术，即使在没有GPS卫星信号的区域内，例如地下车库或密集的城市中心。利用F-RAM几乎无限次的耐久特性，它可以不间断的存储车辆位置，使导航系统一直保持最新的位置信息。在没有GPS卫星信息号的地点，F-RAM会记得汽车先前的位置使其可以继续航行。这样，在离开地下车库或进入市中心，驾驶员不必等候系统寻找信号以了解选择该走哪条路。
• 存储动态信息：这个有望成为导航系统市场增长的关键特性。大量的且频繁变化的有效数据在总线速度下被无数次的写入F-RAM内，以确保在断电后数据可以立即生效使用。

• 存储DVD读头位置：多数嵌入式导航系统是将地图或其他信息存储到DVD上。F-RAM的高性能表现，是它可以连续不断的存储DVD读头的位置，根本不需要内存支持。如果电源突然中断（比如，发动机失灵），系统可以知道DVD读头在哪并立即恢复读数据，不会受发动起重启的影响。这些防止了导航系统瞬间丢失数据的发生。

联系F-RAM 应用工程师，发现如何应用F-RAM 改善您的车载导航设计。
 
Email us at framinfo@ramtron.com or call 719-481-7000.

Anti-pinch is a technique to prevent an electrically operated window or door from trapping a finger as it closes. This is a standard requirement for all power doors/windows in automotive applications. Anti-pinch is also being applied to industrial applications that use electrically operated doors.

Why use F-RAM?
Storing Position – The anti-pinch mechanism must be active until the door/window is nearly closed. This means that the position of the door/window must be constantly measured. To avoid the use of an expensive position sensor, the system records the position of the door/window when it is either fully opened or fully closed. This is achieved by counting the number of motor rotations and requires that the current position be stored in a nonvolatile memory so that it can be recovered in the event of a power loss. F-RAM is ideal for this purpose as it can be written continuously without reaching its endurance limit.

Resistance Profiling – The anti-pinch system monitors the resistance of door/window movement to determine whether a door/window has trapped something. However, resistance can change with temperature, time, wear, and lubrication. The anti-pinch system must be able to measure whether the resistance is caused by these changes or a trapped appendage. The friction profile must be stored in nonvolatile memory. If F-RAM is used, the profile can be written as often as required. If either flash or EEPROM is used, writing is typically only performed when the power is off, increasing the demand on the system’s power reserve. Another disadvantage to using flash is that flash must erase and rewrite an entire page to change only a small amount of data. This takes a significant amount of time and, again, depletes the system’s power reserve.

Supplementing RAM Requirements – The microcontroller (MCU) industry typically provides 16 bytes of flash for every one byte of RAM. Signal processing for anti-pinch systems requires more RAM than this. As such, the system must incorporate a more costly MCU with more RAM – as well as flash – resulting excessive memory, which the system will not even use. The alternative is to use F-RAM to supplement the missing RAM, combined with a low-cost MCU.

Contact an F-RAM applications engineer to find out how F-RAM can improve your next automotive drive-by-wire design.
 
Email us at framinfo@ramtron.com or call 719-481-7000.