Patent Application
20100201290
The present invention relates to piezoelectric devices, and more particularly, some embodiments relate to fault control systems in piezoelectric actuators.
Piezoelectric actuators utilize the converse piezoelectric effect to create a mechanical displacement in response to an applied voltage. Such actuators may be used in applications such as machine tools, disk drives, military applications, ink delivery systems for printers, medical devices, precision manufacturing, fuel injection, or any application which requires high precision or high speed fluid delivery.
In most actuators, a single piezoelectric element is used to mechanically actuate the device. Systems requiring a higher degree of precision and predictability may utilize an actuator with multiple piezoelectric elements. In such systems, each individual piezoelectric element may be independently driven. However, when an element of such a piezoelectric actuator fails, the element will behave like a short circuit, and often damage or disable the entire actuator.
According to various embodiments of the invention, a system and method of multi-element piezoelectric actuator fault recovery is presented. A plurality of piezoelectric elements of a piezoelectric actuator and their corresponding driving signals are monitored. If an element fails, it is removed from the list of elements and the driving signals are rerouted so that the driving signal with the least impact on actuator performance is removed.
According to an embodiment of the invention, a method of piezoelectric fault recovery comprises: monitoring a set of operational piezoelectric elements of a piezoelectric actuator; detecting a failure of an element of the set; and removing the failed element from the set.
According to a further embodiment of the invention, the step of removing further comprises disabling the actuator if less than a predeteimined number of elements remain in the set of monitored elements.
Other features and aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the invention. The summary is not intended to limit the scope of the invention, which is defined solely by the claims attached hereto.
The present invention, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the invention. These drawings are provided to facilitate the reader's understanding of the invention and shall not be considered limiting of the breadth, scope, or applicability of the invention. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.
Some of the figures included herein illustrate various embodiments of the invention from different viewing angles. Although the accompanying descriptive text may refer to such views as “top,” “bottom” or “side” views, such references are merely descriptive and do not imply or require that the invention be implemented or used in a particular spatial orientation unless explicitly stated otherwise.
The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the invention be limited only by the claims and the equivalents thereof.
Before describing the invention in detail, it is useful to describe an example environment with which the invention can be implemented. One such example is that of a driver for a multi-element piezoelectric actuator used in a fuel injector.
A more particular example is that of a fuel injector for dispensing fuel into a combustion chamber of an internal combustion engine, wherein injector pressure and temperature is high enough that the fuel charge operates as a super-critical fluid. An example of this type of fuel injector is disclosed in U.S. Pat. No. 7,444,230, herein incorporated by reference in its entirety.
Another such environment is a piezoelectric actuator driver of the type described in U.S. patent application Ser. No. 12/686,247, U.S. patent application Ser. No. 12/652,679, or U.S. patent application Ser. No. 12/686,298, each of which is herein incorporated by reference in its entirety. Another environment is system for defining a piezoelectric actuator waveform of the type described in U.S. Provisional patent application Ser. No. 12/652,674, which is hereby incorporated by reference in its entirety.
Another example is a piezoelectrically actuated fuel injector, for example, of the type disclosed in U.S. Provisional Patent Application No. 61/081,326, having a piezo actuated injector pin having a heated portion and a catalytic portion; and a temperature compensating unit; wherein fuel is dispensed into a combustion chamber of an internal combustion engine.
From time-to-time, the present invention is described herein in terms of these example environments. Description in terms of these environments is provided to allow the various features and embodiments of the invention to be portrayed in the context of an exemplary application. After reading this description, it will become apparent to one of ordinary skill in the art how the invention can be implemented in different and alternative environments.
Unless defined otherwise, all technical and scientific teens used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. All patents, applications, published applications and other publications referred to herein are incorporated by reference in their entirety. If a definition set forth in this section is contrary to or otherwise inconsistent with a definition set forth in applications, published applications and other publications that are herein incorporated by reference, the definition set forth in this section prevails over the definition that is incorporated herein by reference.
Switch 15 is configured to receive the plurality of signals 12, 13, and 14, and to transmit those signals along channels 16, 17, and 18. Switch 15 may comprise, for example, an analog switch or analog switch matrix, or a relay or plurality of relays. Switch 15 is further configured to allow the fault control module 26 to control which signal is sent along which channel and to switch any signal off. For example, in a default state, switch 15 may be configured to transmit signal #112 along channel #116, signal #213 along channel #217, and signal #314 along channel #318. If, for example, piezoelectric element #122 were to meet a fault condition, switch 15 may be configured to reroute signal #1 to channel #2 and to switch signal #2 off at the instruction of the fault control module.
Fault control module 26 is configured to monitor the plurality of piezoelectric elements 22, 23, and 24 and control the signal routing in case of a fault. Fault control module 26 may monitor the piezoelectric elements using lines 19, 20, and 21. The monitoring may comprise any inspection that may indicate a failure or impending failure of a piezoelectric element. For example, fault control module 26 may determine that a fault has occurred if the voltage across a piezoelectric element drops below a certain predetermined threshold voltage. The predetermined threshold voltage may vary depending on the application of the embodiment. For example, in a multi-element piezoelectric actuator using lead zirconate titanate to actuate a fuel injector, the predetermined threshold voltage may be approximately 130 volts. In this case, fault control module 26 may be configured to reroute the signal previously sent to the failed piezoelectric element or to turn that signal off using switch 15. In further embodiments, fault control module 26 may be configured to send an error message or code to the device or environment employing the piezoelectric actuator. For example, in an embodiment used in a piezoelectric actuated fuel injector, the fault control module 26 may be configured to provide an error code to the vehicle's electronic control unit.
In further embodiments, fault control module 26 may be coupled to signal source 11, and may be configured to control or modify the signals provided by signal source 11 in the case of a fault. For example, if it detects a fault event, fault control module 26 may instruct the signal source 11 to cease sending the signal that was previously being sent to the failed piezoelectric element. In embodiments employing a piezoelectric driver of the type disclosed in copending U.S. patent application Ser. No. 12/686,247, fault control module 26 may be configured to cause signal source 11 to provide new signals to the remaining functional piezoelectric elements. For example, signal source 11 may have a predetermined plurality of preprogrammed contingency signals that allow the piezoelectric actuator 25 to continue operation until it can be repaired.
At inquiry 47, while the piezoelectric actuator is not actuating, the voltage across the first piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the drive to the first piezoelectric element is disabled at step 48 and the system performs the first piezoelectric element recovery routine 49, as described with respect to
At inquiry 50, the voltage across the second piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the drive to the second piezoelectric element is disabled at step 51 and the system performs the second piezoelectric element recovery routine 52, as described with respect to
At inquiry 53, the voltage across the third piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the drive to the third piezoelectric element is disabled at step 54 and the system performs the third piezoelectric element recovery routine 55, as described with respect to
After the remaining drive signals have been rerouted to the remaining piezoelectric elements, operation 72 involves transmitting the drive signals to the piezoelectric elements. At inquiry 74, while the piezoelectric actuator is not operating, the voltage across the second piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. In the particular illustrated embodiment, the system cannot continue to operate with only one operating piezoelectric element. For example, the system may be employed in a fuel injector, where two piezoelectric elements are required for the injector to operate at a low power setting. Accordingly, if failure occurs, the drives to the second and third piezoelectric elements are disabled at step 73. At step 75, the system suspends operation. In some embodiments, suspending operation may also include transmitting a signal, for example a message to a vehicle's electronic control unit indicating the system failure. Having suspended operations, the method ends at step 76. If failure does not occur, the system proceeds to inquiry 77. At inquiry 77, the voltage across the third piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the method proceeds to step 73, as described herein. If inquiry 77 indicates that the third piezoelectric element is still functional, then the system repeats the method beginning with operation step 72.
After the remaining drive signals have been rerouted to the remaining piezoelectric elements, operation 85 involves transmitting the drive signals to the piezoelectric elements. At inquiry 86, while the piezoelectric actuator is not operating, the voltage across the first piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. In the particular illustrated embodiment, the system cannot continue to operate with only one operating piezoelectric element. For example, the system may be employed in a fuel injector, where two piezoelectric elements are required for the injector to operate at a low power setting. Accordingly, if failure occurs, the drives to the first and third piezoelectric elements are disabled at step 87. At step 88, the system suspends operation. In some embodiments, suspending operation may also include transmitting a signal, for example a message to a vehicle's electronic control unit indicating the system failure. Having suspended operations, the method ends at step 89. If failure does not occur, the system proceeds to inquiry 90. At inquiry 90, the voltage across the third piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the method proceeds to step 87, as described herein. If inquiry 90 indicates that the third piezoelectric element is still functional, then the system repeats the method beginning with operation step 85.
After the remaining drive signals have been rerouted to the remaining piezoelectric elements, operation 96 involves transmitting the drive signals to the piezoelectric elements. At inquiry 97, while the piezoelectric actuator is not operating, the voltage across the third piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. In the particular illustrated embodiment, the system cannot continue to operate with only one operating piezoelectric element. For example, the system may be employed in a fuel injector, where two piezoelectric elements are required for the injector to operate at a low power setting. Accordingly, if failure occurs, the drives to the first and second piezoelectric elements are disabled at step 98. At step 99, the system suspends operation. In some embodiments, suspending operation may also include transmitting a signal, for example a message to a vehicle's electronic control unit indicating the system failure. Having suspended operations, the method ends at step 100. If failure does not occur, the system proceeds to inquiry 101. At inquiry 101, the voltage across the third piezoelectric element is measured. If the voltage is less than a predetermined threshold voltage, then the element is considered to have failed. If failure occurs, the method proceeds to step 98, as described herein. If inquiry 101 indicates that the third piezoelectric element is still functional, then the system repeats the method beginning with operation step 96.
After reading this description it will be apparent to one of ordinary skill in the art how to extend the described example recovery system and method to piezoelectric actuators employing fewer or more piezoelectric elements. For example, in an actuator employing four elements, if one of the elements failed, there would be three remaining elements. The recovery subroutine for a four-element actuator would then be substantially similar to the fault recovery method of a three-element actuator according to
As used herein, the term module might describe a given unit of functionality that can be performed in accordance with one or more embodiments of the present invention. As used herein, a module might be implemented utilizing any form of hardware, software, or a combination thereof. For example, one or more processors, controllers, ASICs, PLAs, logical components, software routines or other mechanisms might be implemented to make up a module. In implementation, the various modules described herein might be implemented as discrete modules or the functions and features described can be shared in part or in total among one or more modules. In other words, as would be apparent to one of ordinary skill in the art after reading this description, the various features and functionality described herein may be implemented in any given application and can be implemented in one or more separate or shared modules in various combinations and permutations. Even though various features or elements of functionality may be individually described or claimed as separate modules, one of ordinary skill in the art will understand that these features and functionality can be shared among one or more common software and hardware elements, and such description shall not require or imply that separate hardware or software components are used to implement such features or functionality.
Various components and modules of the invention may be implemented using digital signal processing techniques. Where components or modules of the invention are implemented in whole or in part using software, in one embodiment, these software elements can be implemented to operate with a computing or processing module capable of carrying out the functionality described with respect thereto. One such example-computing module is shown in
Referring now to
Computing module 200 might include, for example, one or more processors, controllers, control modules, or other processing devices, such as a processor 204. Processor 204 might be implemented using a general-purpose or special-purpose processing engine such as, for example, a microprocessor, controller, or other control logic. In the example illustrated in
Computing module 200 might also include one or more memory modules, simply referred to herein as main memory 208. For example, preferably random access memory (RAM) or other dynamic memory, might be used for storing information and instructions to be executed by processor 204. Main memory 208 might also be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 204. Computing module 200 might likewise include a read only memory (“ROM”) or other static storage device coupled to bus 202 for storing static information and instructions for processor 204.
The computing module 200 might also include one or more various forms of information storage mechanism 210, which might include, for example, a media drive 212 and a storage unit interface 220. The media drive 212 might include a drive or other mechanism to support fixed or removable storage media 214. For example, a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a CD or DVD drive (R or RW), or other removable or fixed media drive might be provided. Accordingly, storage media 214 might include, for example, a hard disk, a floppy disk, magnetic tape, cartridge, optical disk, a CD or DVD, or other fixed or removable medium that is read by, written to or accessed by media drive 212. As these examples illustrate, the storage media 214 can include a computer usable storage medium having stored therein computer software or data.
In alternative embodiments, information storage mechanism 210 might include other similar instrumentalities for allowing computer programs or other instructions or data to be loaded into computing module 200. Such instrumentalities might include, for example, a fixed or removable storage unit 222 and an interface 220. Examples of such storage elements 222 and interfaces 220 can include a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, a PCMCIA slot and card, and other fixed or removable storage elements 222 and interfaces 220 that allow software and data to be transferred from the storage unit 222 to computing module 200.
Computing module 200 might also include a communications interface 224. Communications interface 224 might be used to allow software and data to be transferred between computing module 200 and external devices. Examples of communications interface 224 might include a modem or softmodem, a network interface (such as an Ethernet, network interface card, WiMedia, IEEE 802.XX or other interface), a communications port (such as for example, a USB port, IR port, RS232 port Bluetooth® interface, or other port), or other communications interface. Software and data transferred via communications interface 224 might typically be carried on signals, which can be electronic, electromagnetic (which includes optical) or other signals capable of being exchanged by a given communications interface 224. These signals might be provided to communications interface 224 via a channel 228. This channel 228 might carry signals and might be implemented using a wired or wireless communication medium. These signals can deliver the software and data from memory or other storage medium in one computing system to memory or other storage medium in computing system 200. Some examples of a channel might include a phone line, a cellular link, an RF link, an optical link, a network interface, a local or wide area network, and other wired or wireless communications channels.
In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to physical storage media such as, for example, memory 208, storage unit 220, and media 214. These and other various forms of computer program media or computer usable media may be involved in storing one or more sequences of one or more instructions to a processing device for execution. Such instructions embodied on the medium, are generally referred to as “computer program code” or a “computer program product” (which may be grouped in the form of computer programs or other groupings). When executed, such instructions might enable the computing module 200 to perform features or functions of the present invention as discussed herein.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the invention, which is done to aid in understanding the features and functionality that can be included in the invention. The invention is not restricted to the illustrated example architectures or configurations, but the desired features can be implemented using a variety of alternative architectures and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations can be implemented to implement the desired features of the present invention. Also, a multitude of different constituent module names other than those depicted herein can be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise.
Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.
The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.
Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.
This application claims priority from U.S. Provisional Patent Application Ser. Nos. 61/144,265, filed Jan. 13, 2009, which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61144265 | Jan 2009 | US |
