Electronic transmission control, or shift-by-wire, is a new technology in the automotive industry that replaces traditional mechanical control systems. “By-wire” technology has many advantages—both for the auto designer as well as the driver.  For the design team, shift-by-wire eliminates constraints associated with the conventional mechanical linkage to the transaxle, allowing greater freedom of design. This design enhancement translates into improved ease of shifting for the driver. For example, during parking, the driver can engage the parking mechanism of the transaxle at the touch of a switch.

Shift-by-wire systems also offer better fuel efficiency through improved shifting performance, which can yield fuel savings upwards of 5%.

How shift-by-wire works
The shift-by-wire gear change mechanism is driven by an electric motor. A number of rotations will be required to change a gear. The number of rotations is counted by a Hall Effect sensor. The count must be stored in order to safeguard the data from sudden power loss that may occur. If the count is lost, the system must be recalibrated and gear selection is not possible until recalibration is complete.

Why use F-RAM?
The gear rotation count must be written to a nonvolatile memory with great frequency. Only F-RAM nonvolatile memory has unlimited number of write cycles, making it the memory of choice for electronic transmission systems.

In transmissions, the gear change mechanism encounters harsh temperature conditions that requires AEC-Grade 1 qualification (-40°C to 125°C). F-RAM has a small price adder for this temperature range, but other nonvolatile memory technologies have a much larger price adder.

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.

Feature sets on navigation devices are starting to expand. The latest trend in navigation systems is to provide dynamic information on the planned route or the driver’s immediate surroundings via a server connection. We are already familiar with navigation systems that provide traffic information and weather warnings. The next step is to offer information on the surroundings, such as restaurants, attractions, and activities.

Once a server connection is established, the scope of communication between the navigation system and the vehicle broadens significantly. For example, when a car encounters icy roads, its antilock brake system (ABS) and electronic stability control system will communicate the road conditions to the navigation system, which will, in turn, inform the server. The server will then notify other drivers of the problematic road conditions.

Why use F-RAM?

• Stores Vehicle Position: Nonvolatile F-RAM memory enables enhanced position technology even in areas without a GPS satellite signal such as underground garages or dense city centers. Making use of its virtually unlimited endurance, F-RAM continuously stores the vehicle’s location so that the navigation system always has the most current location information. And in spots where a GPS satellite signal is unavailable, F-RAM remembers the car’s previous position so navigation can continue. This way, upon leaving an underground garage or entering a city center, the driver does not have to wait for the system to find a signal in order to know which way to turn.
• Stores Dynamic Information: This feature is poised to be the most significant contributor to the growth of the navigation system market. The mass of constantly changing data available today can be written to F-RAM trillions of times at bus speed, ensuring that this information is immediately available after a power interruption.

• Stores DVD Head Position: Many embedded navigation systems store maps and other information on a DVD. Because of its high endurance, F-RAM can continuously store the position of the DVD reading head without wearing out the memory. If power is suddenly interrupted (for instance, if the engine stalls), the system knows where the DVD head is and can immediately resume reading data without interruption when the engine restarts. This prevents the navigation system from being momentarily lost.

Contact an F-RAM applications engineer to find out how F-RAM can improve your next automotive onboard navigation design. 
 
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.

The Ramtron Automotive System Design Blog exists to help system designers understand the benefits of using F-RAM memory in demanding automotive applications. Hosted by Ramtron Applications Engineer, Duncan Bennett, the blog features product updates, design articles, and application spotlights. To maintain the quality of the the blog experience, comments are moderated but always welcome from system designers.

About Duncan Bennett

Ramtron's Automotive System Design Blog is hosted by Duncan Bennett, Ramtron's autotmotive applications expert. Duncan holds degree in Electronics, Computing and Communications from Bradford University. In his early career, he was as a senior design engineer at several large semiconductor companies where he designed products ranging from control systems to high-end graphics processors. Duncan currently defines and specifys new F-RAM memory products for Ramtron and supports the development of Ramtron’s automotive business wordwide.

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