Patent Application
20130079933
The described embodiments relate generally to reducing rotation induced vibrations from associated components in computing systems. In particular, a method and system to avoid operating the components at rotational speeds that can coincide with resonant frequencies of the computer system are described.
One common way to facilitate heat removal from computers is to introduce cooling fans that circulate air into and out of a computer enclosure. Cooling fans were originally designed to simply run the entire time the computer was on. While this made for a predictable, and continuous operating state, it was not energy efficient and resulted in the creation of unnecessary noise and vibrations. In a slightly more advanced configuration, the fan could be switched between on and off states whenever the internal temperature of the computer enclosure exceeded a certain threshold temperature. Further innovations brought Pulse Width Modulation (PWM) control to cooling fans. PWM controllers change the speed of direct current (“DC”) cooling fan motors by modulating the input voltage, which may be represented as a periodic rectangular wave having an alternating sequence of on-time and off-time. The fraction of time that the signal is active equates to the duty cycle of the PWM signal. For example, where the on-time pulse duration (t) is 0.5 seconds and the period (T) of the PWM signal is 1 second, the duty cycle is 50 percent. In this way, fan speed can be modulated between a numbers of speeds which allows a cooling system to more efficiently regulate the internal temperature of a computer system. At low enough rotational speeds a fan might not even be noticeable to the end user of a computer system. While the speed modulation capability allowed by PWM controllers does allow cooling to take place much more efficiently, the high number of different potential frequencies greatly increases the possibility of at least one cooling fan operating speed having a vibration resonance which coincides with a resonant frequency of the structure of the computer system. When these vibration resonances coincide, vibrations can become significantly more pronounced, causing distracting noise and vibration to propagate through the computer enclosure.
Therefore, what is desired is a reliable way to identify and avoid those operating conditions where a system resonance frequency and vibration resonance coincide to produce mechanical vibrations that adversely affect the overall user experience.
This paper describes various embodiments that relate to a computing system having mechanical components, some of which have rotational aspects with vibration resonances. Methods and apparatus for preventing the coincidence of a vibration resonance and a system resonance are described.
A method for operating a computing system having at least one mechanical component having a rotational aspect controlled by a processor is described. In one embodiment, prior to operating the mechanical component with the rotational aspect at a first operating state, it is determined if the first operating state coincides with a resonant frequency of the computing system. When it is determined that the first operating state does coincide with the resonant frequency, then modifying the first operating state of the mechanical component to a second operating state that avoids the resonant frequency of the computing system.
In one aspect of the described embodiment, determining if the first operating state results in the mechanical component having a vibration resonance that coincides with a resonance frequency of the computing system is carried out by a sensor monitoring the physical response of the computing system. If the monitored physical response is greater than a threshold level, then the first operating state is determined to coincide with the resonant frequency of the computing system. The operating state is then avoided during operation of the computing system in the second operating state.
A computing system is described that includes a data storage device for storing data, at least one mechanical component having a rotational aspect and a processor. In the described embodiment, during operation of the computing system, the processor dynamically determines a critical resonance frequency for the at least one mechanical component using a sensor by progressively changing a rotational speed of the rotational aspect of the mechanical component through a range of rotational speeds, using the sensor to monitor a mechanical response of the computing system while the rotational speed is being progressively changed, identifying the rotational speed as a resonant rotational speed when the mechanical response monitored by the sensor exceeds a pre-determined threshold, and storing the resonant rotational speed in the data storage device as, for example, a Look Up Table (LUT). In one aspect of the embodiment, the sensor is disposed within the computing system. In another aspect, the sensor is disposed external to the computing system.
Non-transient computer readable medium for storing computer code executable by a processor in a computer system having at least one mechanical component having a rotational aspect is described. The computer system includes at least one sensor arranged to detect a mechanical vibration of the computer system and a data storage device. The computer readable medium includes computer code for progressively changing a current rotational speed of the rotational aspect of the mechanical component through a range of rotational speeds. Computer code for continuously monitoring by the at least one sensor a physical response of the computer system to the current rotational speed. Computer code for identifying the rotational speed of the rotational aspect as a resonant speed at which the physical response of the computer system exceeds a pre-determined threshold level of physical response. The non-transient computer readable medium also includes code for storing the resonant rotational speed in a data storage device in the computer system. In one aspect of the described embodiment, the resonant rotational speed is embodied as data in a Look Up Table (LUT). In one aspect, the mechanical component is a fan assembly and the rotational aspect is a fan blade/rotor assembly.
Other aspects and advantages 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 principles of the described embodiments.
The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments.
Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting.
In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting. Accordingly, other embodiments may be used and changes may be made without departing from the spirit and scope of the described embodiments.
Computer systems generally incorporate a number of components, some of which can include rotational aspects (such as fan rotors with blades) that can generate unwanted noise and vibration. Components such as optical disc drives (ODD), hard disk drives (HDD) and cooling fans are examples of such components. Cooling fans, in particular, are one of the leading causes of noise and vibrations in modern computer systems. When these cooling fans are driven at a number of different speeds, it becomes increasingly likely that they can generate a vibration at a frequency that has the potential to coincide with a resonant frequency of the computer system. This coincidence can result in noticeable physical response that can manifest as a buzzing sound, noticeable vibration, or in some cases can adversely affect operation of other mechanical components. For example, a sufficiently severe vibration can adversely affect the operation of a hard disk drive (HDD) that relies upon a read/write head to access data stored in a rotating data storage medium.
Obtaining a reliable and accurate vibration profile of the computer system as to the number and location of resonant frequencies can be quite difficult due to, for example, system to system variation and manufacturing tolerances, as well as a potentially large number of different sources of vibration. To further complicate matters, a vibration profile of the computer system can be altered from an original version in many ways. For example, the vibration profile of the computer system can be altered when an end-user modifies the computer system after production. Components can be added to (or removed from) a standard configuration resulting in a number of different configurations each potentially having significantly different vibration profiles, thus making it difficult to provide a reliable list of resonant frequencies that can be used to characterize the behavior of a particular computer system. Furthermore, vibration profiles can be altered due to changes in operational characteristics of the various components due to normal wear and tear, operational upsets such as dropping, changes due to thermal cycling, and so forth. These factors along with tolerance and mounting variation can make it quite difficult to arrive at a list of resonant frequencies that can be relied upon to prevent a component having a rotational aspect from operating coincident with a system resonant frequency.
Unfortunately, however, accurate identification of the resonant frequencies can require analysis that can be quite lengthy and complex especially when there is more than one source of vibration in the computer system. For example, in addition to a cooling fan (or fans), other sources of vibration such as the HDD and/or ODD can interact with each other resulting in a complex physical response that may be very different than a response from a single vibration source. Moreover, the vibrations produced by each of the different operating components can be directly related to a current operating state of the computer system thereby adding additional complexity. For example, during a data read operation, both the HDD and the ODD can be vibration sources. However, during a data write operation, only the HDD can remain as a vibration source (the ODD being placed in stand-by mode).
In order to overcome these obstacles, a testing regime can require at least cycling the cooling fans (or other operational components having rotational aspects) through most or all potential operating modes and speeds in combination with each and every other source of vibration in the computer system. In this way, vibration profiles can be generated for any number of combinations of operating components. For example, the various vibration profiles can reflect operating conditions where with the HDD and ODD are operating (or only one or the other is operating) and so forth. Once a resonant frequency is identified, in a procedure referred to as notching, a controller circuit (such as a fan controller) can direct the associated component to operate in an operating state just above or below the identified resonant frequency if that frequency would otherwise have been selected. For example, when it is determined that a cooling fan assembly operating at a fan speed FS1 coincides with a system resonant frequency (based upon a monitored physical response of the computer system), the cooling fan assembly can be directed to avoid fan speed FS1. In one embodiment, the fan speed FS1 can be “notched” out, or removed, from the operating regime of the cooling fan assembly. By notched out, it is meant that in those situations that would otherwise call for the cooling fan assembly to operate at fan speed FS1, cooling fan assembly would be directed to operate at fan speeds other than fan speed FS1. For example, the cooling fan assembly can be directed to operate at fan speed FS2 where fan speed FS2 has been determined to not coincide with a system resonant frequency. In some cases, fan speed FS2 can be greater than fan speed FS1 in order to avoid any possibility of under-cooling the computer system. However, it should be noted that in order to preserve power, fan speed FS2 can be less than fan speed FS1 when it is determined that this operating state will maintain proper cooling of the computer system. In this way, by operating fan speed FS2 that is less (i.e., slower) than FS1, the cooling fan assembly can operate at a reduced power thereby preserving power resources.
It should be noted that while computer system calibration could be quite effective at establishing a good baseline for operation of the computer system components that act as vibration sources, the physical response of the computer system can change for a number of reasons in addition to an end-user modification discussed above. For example, the response of the computer system (also referred to as the vibration profile) can change due to normal wear of mechanical components of the computer system (i.e., rotational components begin to wear out or the effectiveness of lubrication wanes), thermo-mechanical changes (expansion or contraction) due to variation in temperature, pressure, humidity, and so forth. Each of these environmental factors can be included in the stored data and be used to modify the operating state in accordance with an appropriate environmental factor.
More specifically, operational characteristics of mechanical components tend to change over time. For example, a cooling fan can operate at slightly different speeds than originally designed due to, for example, wearing of components, breakdown of lubrication, and so forth. These changes can have the effect of shifting the performance curve of the mechanical component. In some cases, this shift in the performance curve cannot be easily predicted. For at least this reason, a vibration profile that takes into consideration time and wear characteristics of a particular system can be very desirable. In this way, periodically updating the vibration profile of the computer system can be very useful. The updating can be performed manually by an end-user, the updating can be performed by the end-user when prompted by the computer system, or the updating can be performed automatically as determined by the computer system. In any case, the updating of the vibration profiles can greatly enhance the end-user's overall enjoyment of the computer system.
Many computer systems include sensors that can be used to detect and monitor physical reactions of a computer system. These sensors can rely upon mechanical changes in the computer system that can be detected and recorded. In one embodiment, an integrated microphone can be used to detect the auditory noise produced by the vibrations. In another embodiment, a motion or acceleration based sensor (such as a G sensor or an accelerometer) can be utilized for detecting the vibrations. In still other embodiments, the sensors can be bench test type sensors that can be used to create a baseline vibration profile for a representative computer system that can then be stored locally in a data storage device in the computer system. For example, using one or more sensors while operating the fan(s) in a range of expected fan speeds, a vibration profile for the computer system can be created. In one embodiment, the sensors can be part of the bench test environment. In some cases, however, the motion sensors can include sensors incorporated into the computer system (referred to as on-board sensors). In this way, the vibration profile for a particular computer system can be periodically updated using real time data from the on-board sensors.
In any case, it should be noted that when relying upon the sensors, any extrinsic source (i.e., not related to the computer system) of vibration or acceleration should be minimized or at least characterized in order to provide a vibration profile that is as close to the actual operation of the computer system as possible. For example, ambient noise could potentially interfere with an acoustic sensor such as a microphone accurately monitoring acoustic signals from the computer system. Characterizing the physical response of the computer system at an elevated temperature could provide a vibration profile that is substantially different than the vibration profile when the computer system is operating at a lower temperature (due in part to expansion/contraction of components). Therefore, providing vibration profiles at different temperatures is especially useful when the computer system has components that are particularly susceptible to physical changes (such as expansion and contraction) due to temperature, pressure, humidity, and so on. For example, during an assembly process, the physical responses of the computing device can be characterized for resonant frequency interactions using any number and type of external and internal sensors. The computing system can be identified and the resonant frequencies can be stored locally as part of a set of operating data used in the operation of the computing device
When fan controller 106 takes the form of a PWM controller, adjustment of the speed of cooling fan 108 can be accomplished by varying the duty cycle of the signal provided to cooling fan 108. Once cooling fan 108 reduces the internal temperature of computer system enclosure 101, sensor 102 can detect a current temperature within computer system enclosure 101. The controller can also be designed to adjust the operating state of other components in the computer system that have an impact on temperature. If the current temperature is determined to be within an acceptable range of operating temperatures, processor 104 can direct PWM controller 106 to maintain or reduce the speed of cooling fan 108. In this way, the feedback loop between sensor 102 and PWM controller 106 can result in a large number of potential operating states of the fan assembly. Each of these potential operating states must be evaluated for potential coincidence with system resonance frequencies. In addition to variation of the rotational speed of cooling fan 108, when multiple potential vibration sources are present, the computer system can exhibit multiple vibration profiles depending upon the number of and current operating state of each of the multiple vibration sources. In this way, the resonance avoidance data can be related to a single component, such as cooling fan 108, or can be related to multiple components (such as the HDD and ODD) that can operate at the same time as fan assembly 108 under varying operating conditions.
In
For example, portions of cooling fan assembly 300 that are most sensitive to vibration can be identified for assembly line testing. This information can then be used to ascertain an optimal calibration testing arrangement. Bench calibration testing can include vibration sensing laser 318 and accelerometer 316 that can be used to obtain precise readings for various vibration resonances that otherwise would be difficult for a less sensitive on-board sensor to capture in follow-on recalibrations. In one embodiment, the vibration resonance information can be stored for later use. For example, the vibration resonance information can take the form of a Look Up Table, or LUT, that can be stored in a data storage device such as a non-volatile memory in communication with a processor used to control operations of computer system 100. In this way, the processor can use the information in the Look Up Table to provide operating instructions to a fan controller used to modify the operation of fan assembly 300. In this way, the initial calibration information can be used over an extended period of time.
In one embodiment, various on-board sensors can be used to monitor any changes from the expected response of computer system 100 to a current operating state of cooling fan assembly 300. Having on-board sensors is particularly useful in monitoring any changes in the responses of computer system 100 over the operating life of computer system 100. Periodic updating of the calibration information stored in the data storage device can be carried out either automatically (at pre-determined intervals of operation) or by an end-user calling for a re-calibration procedure. The re-calibration procedure can be based upon the end-user initiating the re-calibration procedure by interacting with an appropriate user interface (i.e. through a trouble shooting menu). The recalibration procedure can then cause cooling fan assembly 300 to operate at various operating states (i.e., varying fan speed, for example) concurrent with an on-board sensor monitoring a corresponding physical response of computer system 100. The monitored physical response of computer system 100 can then be compared to the baseline (or initial) physical response obtained in a factory setting (or at a previous re-calibration). If the comparison indicates a difference in physical response for a given cooling fan assembly operating state greater than a threshold value, then the calibration data stored in the data storage device can be updated with the most recent calibration information. In some cases, if the difference in physical response is greater than a second threshold indicating system response is not acceptable (possibly indicative of a mechanical problem such as a loose fitting or coupling), a notice to the end-user can be provided, indicating that service by an authorized service center may be required.
It should be noted that the width of the frequency response can determine an amount above (or below) the resonant frequency that the cooling fan is directed to operate. In some cases the cooling fan may be directed to operate at a fan speed that is about 50-100 Hz above (or below) a resonant frequency having a relatively narrow width. However, for those resonant frequencies having a somewhat broader width, a slightly larger buffer may be necessary. In addition to variations in the width of the frequency response, an additional guard band may be prudent in those cases where the heat of the computer system can cause small variations in the values of the resonant frequencies and thereby affect their respective widths. It should be noted, however, that in most cases this additional guard band is generally no more than about 10-20 Hz.
In those cases where a computer system has components that are susceptible to changes in temperature, more than one set of calibration data embodied in, for example, the Look Up Table can be provided depending on the range of temperatures at which the computer system is currently operating. For example, if it is determined that a particular component in the computer system has a system resonance at a temperature T1, and then it may be prudent to provide temperature dependent operational instructions to that component when the temperature of the component approaches the temperature T1. For example, if an ODD has an operating state that has been characterized as being associated with a system resonance at disk speed S1 at temperature T1, then a Look Up Table specific to the ODD can provide data for the processor to direct the HDD to spin at a somewhat different RPM than it would otherwise. Moreover, another Look Up Table can be provided for another component (such as an HDD) or even for the ODD at another temperature. Again, the computer system can be calibrated as a function of a single component, or multiple components separately or in combination described in more detail below.
Computer system 500 in the form of laptop 500 can include a number of components each of which can individually become a vibration source independent of each other or in some situations as a result the operation of other components (such as a cooling fan spinning up to remove excess heat generated by an HDD or ODD). For this example, laptop 500 can include a cooling system embodied as cooling fan 502 and cooling fan 504 whereas a data system can be embodied as HDD 506 and ODD 508 each of which can operate independent of or in conjunction with each other. For example, HDD 506 can access a large amount of stored data by rapidly rotating a disk concurrent with a cooling fan(s) changing fan speed(s) in order to maintain a proper operating temperature of the computer system. In order to obtain an accurate Look Up Table for a system of this sort, each contributing source of vibration should be operated simultaneously, as they might during regular computing operations. One possible scenario could include cycling each cooling fan slowly through its range of speeds, while the other components operate in various operating states. For example while cooling fan 502 cycles through its numerous possible operating speeds, cooling fan 504 can be set at a speed of 2500 RPM, HDD 506 spins at 5400 RPM and ODD 508 spins at 5000 RPM. As discussed above, beating frequencies can develop when two (or more) vibrating or rotating bodies are operated at similar but not quite the same frequency. Therefore, in order to avoid generating beating frequencies when more than one vibration source is present, additional data can be provided indicating operation conditions that can lead to the generation of a beating frequency. For example, data associated with cooling fan 502 and cooling fan 504 can be provided for access by the processor when both fans are operating, raising the possibility of generating a beating frequency. In order to reduce this possibility, the fan speeds of cooling fan 502 and 504 can be altered in such a way that a beating frequency is generally avoided.
In some situations, it may be desirable to recalibrate the physical response of laptop 500. For example, if a first calibration has been performed using motion vibration detectors during which an extraneous vibration source unrelated to the physical response of the laptop has been introduced, the resulting calibration data can be less than optimal. Therefore, in some situations it can be desirable to perform multiple calibration tests in order to affirm the results of the first calibration test. If the calibration data of the first and second calibration tests match within an acceptable tolerance, then the calibration data can be stored in a memory device either on-board the laptop and/or in an external testing device, otherwise the calibration should be redone.
In another example where an acoustic detection mechanism, such as microphone 510, is used to characterize the physical response of the laptop computer, a test location having little ambient noise should be selected to prevent erroneous readings. One way to do this would be for microphone 510 to sample the ambient noise level prior to initiating the calibration procedure. In this way accurate data can be more reliably obtained. Furthermore, any external ambient noise in the test environment (such as a door closing shut) during a calibration can be grounds for re-starting the calibration. A second sampling could be accomplished at the end of the calibration in order to characterize any change in ambient noise levels during the calibration process. Any changes in the ambient noise can be accounted for in the acoustic calibration data prior to being stored in a memory device for later use in modifying the operation of the laptop.
In another embodiment, an end-user can initiate a calibration procedure. In one embodiment, the end-user can take advantage of a user interface that can include, for example, a menu of selectable items at least some of which can be related to troubleshooting the computing system. Additionally, the end-user can be instructed to calibrate the computer system (or re-calibrate if need be) in a quiet environment in order to avoid disrupting the calibration process. The end-user can also be instructed to calibrate the computer system in a number of different locations having different environmental conditions (such as ambient noise level, temperature, and so forth). The end-user initiated calibration procedure can be used by the end-user in any situation where, for example, unwanted vibrations can be sensed. This can be due to a number of factors such as normal wear and tear affecting the physical response of the computer system, modifying the physical attributes (adding or removing components) of the computer system, and so on. In one scenario, the end user can call up a user interface on the computer system that can then be used to initiate the end user calibration procedure. The resulting calibration data can then be used by the processor to alter the operation of the computer system. In some cases, the physical response of the computer system to the updated calibration data can be subjectively evaluated by the end-user. The subjective evaluation can then form a basis for either running another calibration procedure if the subjective results are deemed unacceptable or retain the updated calibration data otherwise.
The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data in both a volatile as well as non-volatile manner which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, HDDs, or solid state memory (such as FLASH). The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.
| Number | Date | Country | |
|---|---|---|---|
| 61460772 | Sep 2011 | US |
