Abstract:
An engine control module, and method for operating the same for controlling an internal combustion engine. The engine control module comprising a processor for executing instructions to controlled the engine. The engine control module partitioning its memory used to store calibration data. The memory is partitioned into user-changeable and non-user-changeable portions. Only the user-changeable portions are repeatedly backed up. These portions are backed up such that the engine control module can recreate valid calibration data when a memory failure has occured and the engine control module.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to engine control modules, and in particular, to recreating valid calibration data when a non-volatile memory failure has occurred, for example, due to worn out memory locations. 
   2. Background Art 
   Engine control modules typically include volatile memory and non-volatile memory for storing calibration data. A microprocessor within the engine control module executes the stored calibration data to control an engine. 
   In operation, the non-volatile memory are copies typically used as back ups to the volatile memory copy. When needed, the calibration data values stored in the non-volatile memory can be copied to the volatile. A user can make changes to the calibration data in volatile memory, however, the user cannot typically change the non-volatile memory directly. 
   In the past, changes to the volatile memory calibration data prompted the engine control module to copy the entire volatile memory to the non-volatile memory. The engine control module would then verify the copied data, and if valid, another copy of the data would be made to a second non-volatile memory area. If not valid, implying that the first volatile memory may be faulty or power was removed during the copy process, etc., the data stored in the second non-volatile memory can be used to restore the volatile memory calibration data in order to maintain functionality. In this manner, a verified copy of the calibration data is available even if one of the non-volatile copies are invalid. 
   The copying of the calibration data causes repeated writing to the memories. Eventually, the memory will fatigue and fail. This is a problem. As such, there exists a need to provide a means to recreate valid data even if portions of the non-volatile memory fails. 
   In addition to memory wear-out problems, engine control modules are becoming more complex and require larger memories. The increased memory demand increases costs. This is also a problem. As such, there exists a need to limit memory while providing the necessary back-up protection in a cost effective manner. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to cost effectively limit the amount of non-volatile memory needed to provide adequate back-up protection for the calibration data. 
   One aspect of the present invention relates to an engine control module and corresponding method for operating the engine control module which copies only portions of the calibration data stored in the engine control module memory. Because only a portion of the calibration data is copied, only a portion of the total memory is repeatedly backed up, reducing the size and cost of the back up memory required. 
   The present invention includes partitioning a volatile memory and a first non-volatile memory of the engine control module. The partition separates the memory into user-changeable and non-user-changeable portions. Calibration data for engine control is stored on both the changeable and non-changeable portions, however, only the calibration data stored on the changeable portion can be changed by an end user. 
   The present invention only copies the changeable portion of the volatile memory to the first non-volatile memory if changes are made. The copying generally comprises copying the entire changeable portion of the volatile memory to the corresponding changeable portion of the first non-volatile memory. 
   Once the changes are copied, the engine control module verifies the changes, and may reboot. The user-changeable and non-user-changeable portions of the first non-volatile memory, i.e. the entire first non-volatile memory, are then copied back to the volatile memory for execution after rebooting if the data stored in the non-volatile memory is valid. 
   In addition, the user-changeable portion of the first non-volatile memory is copied to a second non-volatile memory for storage back up after rebooting. If a defect occurs to the changeable portion of the first non-volatile memory, proper operation can be maintained by copying to the volatile memory both (i) the data stored on the second non-volatile memory, which include the calibration data associated with the changeable portion of the memory, and (ii) the non-changeable instructions from the first non-volatile memory. 
   Optionally, data compression can also be used to further limit the amount of memory needed in the second non-volatile memory. The data is compressed when written to the second non-volatile memory and decompressed when read from it. The added time it takes to compress and decompress the data is negligible to the engine controller since writes and reads only occur right before a reboot or right after a reboot, not during engine operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an exemplary engine system controlled by an engine control module in accordance with the present invention; and 
       FIG. 2  illustrates a partitioning of the engine control module memory unit in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  illustrates an exemplary engine system  10  controlled by an engine control module  14  in accordance with the present invention. The engine system generally relates to controlling an internal combustion engine  16 . Engine  16  includes a plurality of cylinders disposed in an engine block. 
   In a preferred embodiment, engine  16  is a multi-cylinder compression-ignition internal combustion engine, such as a 4, 6, 8, 12, 16, or 24 cylinder diesel engine, for example. As will be appreciated by those of ordinary skill in the art, engine may be used in a wide variety of equipment for applications including on-highway trucks, construction equipment, marine vessels, and generators, among others. 
   While the present invention is described with reference to a diesel engine, one of ordinary skill in the art will recognize that the present invention is not necessarily limited to compression-ignition engines and may be easily applied to a variety of internal combustion engine technologies. 
   Engine includes an engine control module (ECM)  14 . In operation, the engine control module  14  receives signals from various vehicle sensors and executes control logic embedded in hardware and/or software to control the engine. In a preferred embodiment, the engine control module is a DDEC controller available from Detroit Diesel Corporation, Detroit, Mich. Various other features of this control module are described in detail in a number of different U.S. patents assigned to Detroit Diesel Corporation. 
   Various sensors are in electrical communication with the engine control module  14  via input ports  22 . Engine control module  14  preferably includes a microprocessor in communication with various computer readable storage media  28  via data and control bus  30 . Computer readable storage media may include any of a number of known devices, including memory unit  34 . 
   Memory unit  34  includes engine calibration data stored thereon. The data is executable by the engine control module  14  to perform methods of controlling the engine  16 , including exhaust gas recirculation (EGR) valve  36  and turbocharger  38 . 
   The programmable calibration data direct engine control module  14  to control the various systems and subsystems of the vehicle, with the instructions being executed by microprocessor  26 . Input ports  22  receive signals from various sensors, and engine control module  14  generates signals at output ports  40  that are directed to the various vehicle components. A data, diagnostics, and programming interface  42  may also be selectively connected to engine control module  14  via a plug  44  to exchange various information therebetween. 
   As is appreciated by one of ordinary skill in the art, control logic may be implemented in hardware, firmware, software, or combinations thereof. Further, control logic may be executed by engine control module  14 , in addition to by any of the various systems and subsystems of the vehicle cooperating with engine control module. Further, any of a number of known programming and processing techniques or strategy may be used to control an engine in accordance with the present invention. 
   Turbocharger  38  includes a turbine  48  and a compressor  50 . The pressure of the engine exhaust gases causes the turbine  48  to spin. The turbine  48  drives the compressor  50 , which is typically mounted on the same shaft. The spinning compressor  50  creates turbo boost pressure which develops increased power during combustion. The exhaust gases pass from engine  16  through exhaust passage and are selectively routed to turbine at inlet  54 . 
   An exhaust gas recirculation system introduces a metered portion of the exhaust gases into intake manifold  56 . The EGR system dilutes the incoming fuel charge and lowers combustion temperatures to reduce the level of oxides of nitrogen. The amount of exhaust gas to be recirculated is controlled by EGR valve  36 . It is appreciated that embodiments of the present invention may be employed in engines with or without an EGR system. 
   In some embodiments, it may be desirable to provide a cooler  60  to cool the charge air coming from compressor  50 . Similarly, in some embodiments, it may be desirable to provide a cooler  62  to cool the flow through the EGR system prior to reintroduction to engine  14  of the gases at intake passage  56 . 
     FIG. 2  illustrates a partitioning of the engine control module memory unit  34  in accordance with the present invention. In general, the memory used by the memory unit  34  is partitioned into user-changeable and non-user-changeable portions. In addition, the memory unit  34  includes a dedicate software program  68  which controls microprocess  26  access to the separate memory or portions of memory in the memory unit  34 . 
   The user-changeable portion relates to the calibration data that the user is permitted to modify. For example, vehicle road speed limits, cruise control parameters, engine protection data, vehicle specification data. The non-changeable portion relates to the calibration data that the user is not permitted to change. For example, fuelling maps, timing data, diagnostics, engine governing characteristics, and others as understood so those skilled in the art. Typically, the engine operation controlled by the calibration data determines whether it is user-changeable or non-user-changeable. 
   The partitioning permits the back up copying to be limited to only the user-changeable portions so that less memory is required. This limits memory fatigue and prolongs memory operation. In addition the partitioning permits the back up memory to be smaller as it is only required to back up the changeable portion, and not the entire memory. This limits the cost of the back up system. 
   The foregoing features and benefits are described below with respect to the memory unit  34  including volatile memory  70 , first non-volatile memory  72 , and second non-volatile memory  74 . The memories  72 ,  74 ,  76  can be protected and unprotected portions of a single memory or separate memory units. This is typically controlled through the dedicated software program  68 . Together, the memories  70 ,  72 ,  74  provide a redundant memory system which permit recreation of the calibration data when a non-volatile memory failure has occured, commands due to worn out memory locations. 
   The memory unit  34  may comprise a single memory or multiple memories which can be used by the engine control module  14 , including static random access memory (SRAM), dynamic random access memory (DRAM), fast page mode dynamic random access memory (FPM DRAM), extended data-out dynamic random access memory (EDO DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), and ferroelectric random access memory (FRAM). In addition, read only memories (ROM) having write capabilities could be used. 
   The calibration data stored in volatile memory  70  is used via bus  30  by engine control module  14 . Non-volatile memory  72 ,  74  provide backup versions of the calibration data and are used to load volatile memory  70  after the engine control module  14  has rebooted. 
   Changes to the calibration data can be made by a user applying the changes directly to the volatile memory. The engine control module  14  copies these changes to first non-volatile memory  72  and reboots engine control module  72 . 
   After rebooting, the changes in first non-volatile memory  72  are verified/validated by engine control module  14 . This typically comprises running a checksum program, as is appreciated by one having ordinary skill in the art. The verified changes can then be copied to second non-volatile memory  74  for additional back up. Typically, the entire user-changeable portion of first non-volatile memory  72  is copied to save memory demanded for second non-volatile memory  74 . Optionally, the calibration data can be compressed prior to copying to second non-volatile memory  74  to further reduce memory requirements. 
   If the checksum program shows that the calibration data in non-volatile memory  72  is not valid, those changes are not copied to second non-volatile memory  74 . Rather, the calibration data from second non-volatile memory  74  can be copied back to first non-volatile memory  72  to overwrite the previous changes. Then, the verified back up calibration data can be copied from first non-volatile memory  72  (if now valid) to volatile memory  70 . If the first copy is still not valid, the calibration data can be copied directly from second non-volatile memory  74  to volatile memory. This process allows the engine control module  14  to function normally with a valid calibration even though one memory  72 ,  74  has failed. A diagnostic is logged instructing the user to have the engine control module replaced when convenient to do so. 
   While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.