Abstract:
An accelerometer system comprises an accelerometer, a processor or threshold system connected to the accelerometer to receive electronic signals from accelerometer indicating acceleration and an annunciator connected to the processor or threshold system to receive electronic signals indicating the magnitude of acceleration. The annunciator produces a human discernable signal to notify of acceleration levels. The accelerometer system alerts vehicle operators of acceleration levels. The accelerometer system may be used to train vehicle operators to drive in a manner that reduces excessive acceleration. One embodiment prolongs battery life by turning off components in between measurements based on acceleration activity. Another embodiment packages the accelerometer system to fit into a cigarette lighter plug for vehicle use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the U.S. provisional application Ser. No. 60/933,537 filed Jun. 6, 2007 entitled “Apparatus and Method to Train Drivers to Drive in a Fuel Efficient Manner” by Nenad Markovic. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable 
       SEQUENCE LISTING 
       [0004]    Not applicable 
       FIELD OF THE INVENTION 
       [0005]    The present invention relates to the field of accelerometer systems, and in particular to devices that communicate acceleration levels to a vehicle operator. 
       BACKGROUND OF THE INVENTION 
       [0006]    Internal combustion engines which drive motor vehicles such as automobiles and trucks are relatively inefficient and consume large quantities of hydrocarbon based fuels. It is well known in the field that the efficiency of fuel consumption for vehicles powered by internal combustion engines is related to the manner in which an operator operates such vehicles. 
         [0007]    Thus, operators of vehicles powered by internal combustion engines can decrease fuel consumption by more gradual acceleration and braking. Furthermore, there are additional benefits to encouraging controlled acceleration and braking. Deterring “jack rabbit” stop and go driving and overly aggressive acceleration trains operators of vehicle to become inherently safer drivers. Also, abrupt acceleration and braking places unneeded stress on parts within vehicles such as tires, brake pads, and even the engine itself. 
         [0008]    Acceleration in the forward or rearward directions of a vehicle is not the only source of mechanical wear and tear. Lateral acceleration, from side to side, caused by aggressive turning can also wear vehicle components such as tires, suspension and steering. 
       SUMMARY OF THE INVENTION 
       [0009]    In one embodiment, an accelerometer system uses an accelerometer, a microprocessor connected to the accelerometer to receive electronic signals from the accelerometer indicating acceleration, and an annunciator connected to the microprocessor to receive electronic signals from the microprocessor indicating the magnitude of acceleration. The annunciator produces a human recognizable signal that indicates the magnitude of the acceleration. 
         [0010]    In another embodiment, an accelerometer system uses an accelerometer, a timer, a threshold system, and an annunciator. The threshold system, activated by the timer, compares accelerometer values with a threshold value. If the accelerometer values exceed the threshold, the threshold system activates the annunciator to indicate the magnitude of acceleration. 
         [0011]    In yet another embodiment, a method for operating an accelerometer system energizes the accelerometer while making an acceleration measurement and turns off the accelerometer in between measurements. The time interval between measurements is adjusted based on acceleration activity. This adaptive method extends battery life in battery operated accelerometer systems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The summary above, and the following detailed description will be better understood in view of the enclosed drawings which depict details of various embodiments. It should however be noted that the invention is not limited to the precise arrangement shown in the drawings and that the drawings are provided merely as examples. 
           [0013]      FIG. 1  is a block diagram of one embodiment of an accelerometer system. 
           [0014]      FIG. 2  is a block diagram of one embodiment of a processor system. 
           [0015]      FIG. 3  is a block diagram of an alternate embodiment of an accelerometer system. 
           [0016]      FIG. 4  is a front perspective view of one embodiment of an accelerometer system enclosure. 
           [0017]      FIG. 5  is a front perspective view of an alternate embodiment of an accelerometer system enclosure. 
           [0018]      FIG. 6  is a timing diagram of two pulse rates. 
           [0019]      FIG. 7  is a flow diagram of an exemplary method to operate an accelerometer system. 
           [0020]      FIG. 8  is a schematic diagram of one embodiment of an accelerometer system. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    In the accelerometer system  10 , of  FIG. 1 , a power supply  12 , powers a processor system  14  via a power connection  120 . The processor system  14  controls a power output  142  to energize the accelerometer  13  via an accelerometer power input  130 . The accelerometer output  132 , of the accelerometer  13  connects to the accelerometer input  144  of the processor system  14 . An annunciator  16  has an annunciator input  162  which is controlled by the threshold comparator output  146  of the processor system  14 . The processor system  14  receives a threshold value  152  from a threshold source  15 . 
         [0022]    In operation, the processor system  14  turns on the accelerometer  13  via the power output  142  and accelerometer power input  130 . The accelerometer  13  generates an electrical value which corresponds to the acceleration experienced by the accelerometer  13 . This value, encoded as a voltage in some embodiments, is available at the accelerometer output  132 . The processor system  14  receives a value from the accelerometer output  132  on the accelerometer input  144  and compares it with a threshold value  152  received from the threshold source  15 . If the threshold value  152  is exceeded by the value at the accelerometer input  144 , the processor system  14  activates the threshold comparator output  146 . When active, the threshold comparator output  146 , connected to the annunciator input  162 , activates the annunciator  16 . The annunciator  16  interfaces with a human through one of the human senses. 
         [0023]    In this application, the term acceleration can mean either an increase of speed or a decrease of speed. The embodiments in this application can be configured to indicate an increase of speed, typically called acceleration in automotive circles, or a decrease of speed due to braking. Depending upon application, the various embodiments can indicate an increase in speed, a decrease in speed or both. 
         [0024]    Each of the components of  FIG. 1  has many possible embodiments. In one embodiment the accelerometer  13  is an integrated circuit with the accelerator output  132  being an analog voltage output responsive to the acceleration experienced by the accelerometer  13 . One example of an integrated circuit accelerometer is the ADXL322 by Analog Devices of Norwood, Mass. Other accelerometers may provide serial or parallel digital outputs with the accelerometer output  132  being serial or parallel bus. Still other accelerometers may provide multiple outputs responsive to acceleration in more than one dimension. An example is an accelerometer with accelerometer outputs for three orthogonal axis typically labeled X, Y and Z. 
         [0025]    In one embodiment, the accelerometer power input  130  of the accelerometer  13  is the power supply of the accelerometer integrated circuit. The power output  142  of the processor system  14  enables the processor system  14  to turn the accelerometer  13  on (energize) and off. While the power output  142  is shown in  FIG. 1  as a simple connection to the accelerometer power input  130 , it can also include a power amplifier or switch in cases where the power output  142  is unable to provide adequate current or voltage to the accelerometer power input  130 . In such cases, the power output controls a switch (not shown) that switches power from the power supply  12  turning the accelerometer  13  on and off. 
         [0026]    The accelerometer input  144  of the processor system  14  receives the accelerometer output  132 . The type of accelerometer output  132  determines the type of accelerometer input  144 . For example, if the accelerometer output  132  is an analog signal, the accelerometer input  144  can be an analog to digital converter input or a comparator input to the processor system  14 . If conversely, the accelerometer output  132  is a digital signal, the accelerometer input  144  is a digital input, serial or parallel, with enough individual signal wires to receive the accelerometer output  132 . If the accelerometer output  132  communicates acceleration information for multiple dimensions, the accelerometer input  144  is chosen to compatibly receive the acceleration values. 
         [0027]    The power supply  12  of  FIG. 1  can take many forms. In one embodiment, power supply  12  is a common 9 volt battery with a voltage regulator or regulators and filtering to supply the correct voltage or voltages to the accelerometer  13 , the processor system  14  and the annunciator  16 . In other embodiments the power supply is a regulator and filter system that connects to a vehicle battery either directly or via a plug such as a cigarette lighter. 
         [0028]    The threshold source  15  can take many forms. In the simplest form the threshold value  152  is encoded into the processor system  14  program. In this case, it is a fixed value or set of fixed values. In other embodiments, the threshold source  15  provides a user adjustable threshold value  152 . Such a user adjustable threshold value  152  enables a user to determine the acceleration level at which the processor system  14  activates the annunciator  16 . In practice, the threshold source can take the form of a potentiometer providing an analog input or a switch system providing a digital input. Depending upon the embodiment, threshold source  152  can represent a single value or a set of threshold values. The processor system  14  uses a set of multiple threshold values  152  to activate multiple threshold comparator outputs  146 . Multiple threshold comparator outputs  146  activate various responses from the annunciator  16 . 
         [0029]    The annunciator  16  is interface between the processor system  14  and a human user (not shown). The annunciator can take many forms depending upon the embodiment. The main types are: light, sound, voice, vibration and smell. Thus the term annunciator, as used in this application means one or a combination of the types listed above. Each of these types has several variations and exemplary embodiments are given in the following paragraphs. 
         [0030]    In one embodiment, the processor system  14  uses three threshold values corresponding to mild, moderate and harsh acceleration. Consequently, the annunciator  16 , has three levels of enunciation to indicate the levels of mild, moderate, and harsh acceleration. The threshold comparator output  146  and annunciator input  162  also have an encoding to activate the annunciator  16  accordingly. The encoding to indicate multiple threshold values  146  can be any number of systems, including, but not limited to, parallel signal lines, pulse width modulation, frequency modulation, a command structure on a serial or parallel bus or others. Those skilled in the art can devise a system to implement the threshold comparator output  146  and annunciator input  162  for the various types described below. 
         [0031]    An LED or light emitting diode is a simple example when light is used for the annunciator  16 . Multiple forms of light output are possible. Examples include a single LED that changes in intensity or flashing frequency as successive threshold values are reached. Other examples include a system of LEDs that light up progressively or change color, for example, from green to yellow to red. One multi-LED embodiment lights a green LED when the driver is in an optimal range of acceleration. An optimal acceleration range results in a smooth, gentle acceleration and less fuel consumption. Accelerating too quickly results in more fuel consumption, with first the yellow and then the red LEDs illuminating. 
         [0032]    A sound based annunciator can use a speaker, beeper, or buzzer to notify a human of acceleration levels. When multiple levels of acceleration are indicated, the sound can be modulated by frequency, amplitude or duration. 
         [0033]    The annunciator can use spoken notifications or warnings as various levels of acceleration are reached. These spoken warnings are recorded voice outputs that can be permanently recorded or recordable by the user. When multiple threshold values are used, the voice can vary in volume, tone or urgency with spoken messages such as; “Easy.”, “Slowly!” or “Back Off”. Integrated circuit voice record/playback devices are known to those skilled in the art. One example is the ISD1740 series by Winbond Electronics Corporation America of San Jose, Calif. 
         [0034]    A vibration annunciator can vibrate a vehicle control such as the steering or accelerator pedal to notify the operator of acceleration levels. 
         [0035]    As an example of aversion therapy, an olfactory (smell) based annunciator can emit disagreeable odors to notify and discourage the operator from excessive acceleration. 
         [0036]      FIG. 2  shows an exemplary processor system  14 . An embodiment using this processor system  14  has an analog accelerometer input  144  which connects to the accelerometer output  132  of  FIG. 1 . An A/D (analog to digital converter)  21  receives the voltage of the analog acceleration value at the accelerometer input  144  and converts it to a digital accelerometer value  220 . 
         [0037]    The filter  22  is any number of digital filter types such as a finite impulse response (FIR), infinite impulse response (IIR), or moving average filter (MA). Combinations and variations are possible such as a weighted moving average. One embodiment uses a moving average of eight samples in one to two seconds. The filter acts as a low pass filter to remove the brief acceleration spikes due to pot holes and uneven roadway. Such brief spikes do not usually indicate driver acceleration and are therefore filtered to reduce false annunciations. The filter output is a filtered accelerometer value  230 . In other embodiments, an analog filter is placed ahead of the A/D. Thus either an analog or digital filter or a combination is possible. In some embodiments, a program of the processor system  14 , implements the digital filter. In other embodiments, dedicated hardware implements the digital filter. 
         [0038]    Referring to  FIG. 1 , when the accelerometer system  10  is placed in a vehicle, the system is placed so that the axis of the accelerometer  13  aligns with the desired dimension. For example, if indication of acceleration in a forward and rearward direction is desired, the accelerometer  13  is aligned along the front to rear axis of the vehicle. If lateral (side to side) indication is desired, the accelerometer  13  is aligned to measure side to side acceleration. If the accelerometer  13  is mounted or placed in a vehicle with a slight initial tilt, there will be an offset error due to gravity. That is to say, the accelerometer  13  will indicate acceleration even when the vehicle is not moving. Returning to  FIG. 2 , the tilt compensation  23  removes this error by subtracting or otherwise removing the effects of the tilt from the measured acceleration. This is accomplished in a number of ways. In a one embodiment, the accelerometer system  10  ( FIG. 1 ) is first turned on when the vehicle is on a level surface. At power up, the tilt compensation stores the accelerometer reading when the vehicle is stopped on a level surface. This reading corresponds to tilt and is used to compensate subsequent accelerometer values. The tilt compensated output  250  more truly represents acceleration. In some embodiments, the tilt compensation  23  is implemented by a program of the processor system  14 . 
         [0039]    The comparator  24  inputs the tilt compensated output  250  for comparison with one or more threshold values  152 . Threshold Source  15  provides the threshold values  152 . Threshold source  15  may be a user adjustable input device or one or more values stored in the program of the processor system  14 . If the acceleration represented by the values on the tilt compensated output  250  exceed one or more threshold values  152 , the comparator  24  activates one or more corresponding threshold comparator outputs  146 . In one embodiment, the threshold source provides three threshold values encoded into the program of the processor system  14 . As the tilt compensated value  250  exceeds each of the threshold values  152 , a corresponding threshold comparator output  146  activates the annunciator  16  ( FIG. 1 ). In this example embodiment, the threshold comparator output  146  has three signal lines which each energize a distinct response of the annunciator  16 . In some embodiments, the comparator  24  is implemented by a program of the processor system  14  and the threshold comparator output  146  is implemented by one or more general purpose outputs of the processor system  14 . 
         [0040]    The power output control  25  depicted by a simple switch in  FIG. 2  represents an output of the processor system  14  which controls the power output  142 . The power output  142  acts to provide power to the accelerometer  13  of  FIG. 1 . This implementation enables the program of the processor system  14  to turn on (energize) or turn off the power to the accelerometer  13  ( FIG. 1 ). Turning the accelerometer power off in between acceleration measurements prolongs battery life in battery powered applications. 
         [0041]    The timer  27  in one embodiment is a part of the processor system  14 . The timer  27  under control of the program of the processor system  14  triggers operations such as that of the A/D  21 , the filter  22 , power output control  25 , and the comparator  24 . The program can also use the timer to control the duration of the threshold comparator output  146  and thus the duration of the annunciator output. 
         [0042]    While  FIGS. 1 and 2  showed a processor based accelerometer system,  FIG. 3  shows an alternate embodiment of an accelerometer system  30 . The accelerometer system  30  can be implemented with discrete analog or digital electronics. Other embodiments of accelerometer system  30  can be implemented with field programmable gate arrays (FPGAs) or custom integrated circuit technologies in either analog or digital methodologies. 
         [0043]    The power supply  12 , accelerometer  13 , threshold source  15 , annunciator  16 , filter  22 , and tilt compensation  23  perform similar functions as those in  FIG. 1  or  2 . The threshold system  34  is made of digital or analog comparators depending upon the technology or methodologies chosen. Power supply  12  provides power to the reset  32  and timer  27 . The timer output  274  provides power to the threshold system  34  and to the accelerometer  13  via the accelerometer power input  130 . The accelerometer output  132  provides a measurement of the acceleration value. The acceleration value at accelerometer output  132  can be further filtered or compensated by filter  22  and tilt compensation  23 . The threshold system  34  receives the accelerometer value after filtering and compensation. Depending upon implementation, filtering and compensation is not always performed. The threshold source  15  connects to the threshold system providing the threshold value  152 . The threshold comparator output  146  from the threshold system  34  connects to the annunciator input  162  of the annunciator  16 . The threshold comparator output  146  also connects to the timer input  272  of timer  27 . 
         [0044]    In operation, the threshold system  34  receives an acceleration value at the accelerator input  144  and makes one or more comparisons against one or more threshold values  152 . If a threshold value  152  is exceeded, the threshold system activates a corresponding threshold comparator output  146 . 
         [0045]    The timer  27  produces a pulse stream at the timer output  274 . Referring to  FIG. 6 , the pulse stream takes one of two forms, a first faster pulse rate  276  or a second slower pulse rate  278 . Both pulse rates  276  and  278  have an active portion  282 . The first faster pulse rate  276  has shorter inactive period  284  while the second slower pulse rate  278  has a longer inactive period  286 . Returning to  FIG. 3 , the timer  27 , has a timer input  272  that controls whether the timer  27  produces the first faster pulse rate  276  ( FIG. 6 ) or second slower pulse rate  278  ( FIG. 6 ). 
         [0046]    At power up or reset, the reset  32  initializes the tilt compensation  23 , threshold system  34  and the timer  27  via the reset output  322 . Upon reset, the timer output  274  outputs the first faster pulse rate  276  ( FIG. 6 ). The active pulse  282  ( FIG. 6 ) activates the accelerometer  13  to make a measurement and threshold system  34  to set the threshold comparator output  146  based on a comparison between the value at the accelerometer input  144  and a threshold value  152 . When the timer output  274  outputs the longer inactive period  286  ( FIG. 6 ) the accelerometer  13  and threshold system  34  go into a lower power state. This lower power state reduces power consumption and prolongs battery life in battery powered systems. 
         [0047]    Threshold comparator output  146  also controls the timer input  272 . If the threshold comparator output  146  remains inactive for a period of time, the timer input  272  directs the timer  27  to provide the second slower pulse rate  278  ( FIG. 6 ) on timer output  274 . The slower pulse rate has a longer inactive period  286  ( FIG. 6 ) and reduces the power consumption of the accelerometer system  30 . If the threshold system activates the threshold comparator output  146  due to a value at the accelerometer input  144  exceeding a threshold value  152 , the timer input  272  directs the timer to output the first faster pulse rate  276  ( FIG. 6 ). In this manner, the timer  27  activates the accelerometer system  30  components less frequently during periods of lesser acceleration activity and more frequently during periods of greater acceleration activity. This adaptive nature of the timer  27  prolongs battery life during less active periods of acceleration without sacrificing responsiveness during active periods. 
         [0048]    Many packaging alternatives are available for the accelerometer system  10  of  FIG. 1  or accelerometer system  30  of  FIG. 3 .  FIG. 4  shows a box enclosure  40  which contains a printed circuit assembly  404  (PCA) holding accelerometer system  10  ( FIG. 1 ) or  30  ( FIG. 3 ) components. In the embodiment depicted in  FIG. 4 , the annunciator  16  is made of three LEDs  410 ,  412 , and  414 . A switch  402 , turns on and off the accelerometer system and also serves as a way to initiate a reset of the accelerometer system. The PCA  404  is oriented in the box enclosure  40  such that the when the LEDs  410 ,  412 , and  414  face the rear of the vehicle, the accelerometer axis  406  is oriented to measure the forward or rearward acceleration of the vehicle. 
         [0049]    Several mounting systems are available to mount the box enclosure  40  of  FIG. 4  to a vehicle. Examples include simply sitting the box enclosure on the dash with small feet  408  or a pad to reduce sliding. Other methods include a suction cup  416  for attachment to the inside of the windshield. Other example methods include, but are not limited to adhesives and hook and latch fasteners  418 . 
         [0050]      FIG. 5  shows another embodiment of an accelerometer system enclosure. In  FIG. 5 , a cigarette lighter enclosure  50 , is adapted to contain the accelerometer system PCA  502  and a speaker  510 . The cigarette lighter enclosure  50  fits into the 12 volt power outlet or cigarette lighter location found in most vehicles. This embodiment enables the accelerometer system to use the vehicle power supply in place of dedicated batteries. When the cigarette lighter enclosure  50  plugs into the dash of a vehicle, the accelerometer axis  506 , mounted to the printed circuit assembly  502 , is oriented to measure acceleration along the desired dimension. In the embodiment of  FIG. 5 , the speaker  510  is part of an annunciator embodiment that uses sound or voice to alert the operator to acceleration. 
         [0051]      FIG. 7  is a flow chart of a method for operating the accelerometer system of  FIG. 1  or  3 . Although shown as a set of sequential steps, not all the steps are necessary to operate the accelerometer system, nor is it always necessary to perform the steps in the given order. The steps shown in  FIG. 7  can be implemented as steps in a program of processor system  14  ( FIGS. 1 and 2 ) or as parts of a more hardware implemented accelerometer system  30  ( FIG. 3 ). 
         [0052]    Step  702  provides and initializes an accelerometer system as described in previous paragraphs. Step  704  turns on or energizes the accelerometer in preparation for an acceleration measurement in  705 . After a measurement is acquired, the accelerometer is turned off in  706  to prolong battery life. Step  708  compensates the measurement for tilt while step  710  filters out noise and  712  obtains one or more threshold values in preparation for comparison. 
         [0053]    Steps  714  and  716  measure the acceleration value against one or more threshold values. If the acceleration value exceeds a threshold value, the system actives the annunciator at  718  and sets the timer to a first value at  722  corresponding to more frequent measurements. 
         [0054]    If the acceleration value does not exceed a threshold value, the system sets the timer to a second value at  724  corresponding to less frequent measurements and therefore less energy consumption. A counter at  720  can be used to require a given number of passes before the timer is set to the second value. Counting out the number of passes that the measurement does not exceed a threshold value can be used to delay setting the timer to the second value. In some embodiments the timer or counter can be set to progressively longer times between measurements if there is no acceleration activity. 
         [0055]    After the timer is set, the system goes into a low power state at  726 . A low power state can be a sleep mode in a processor, or a power off state in a component such as an accelerometer, an annunciator or a threshold system. The timer controls the length of time that the system is in the low power state. Step  728  checks the timer condition. If the timer has not yet expired, the system remains in the low power state. If the timer expires, the system powers up at  730  and proceeds to make another measurement beginning at  704 . 
         [0056]      FIG. 8  is a schematic of an embodiment of the accelerometer system  10  ( FIG. 1 ). The power supply  12  is made of a battery  802 , a voltage regulator  804  and a switch  806 . The battery  802  may be a dedicated battery or part of a vehicle electrical system. The power connection  120  from the power supply  12  connects to the processor system  14  and the annunciator  16 . The accelerometer  13  provides an accelerometer output  132  which is buffered by an amplifier  816 . The output of the amplifier connects to the accelerometer input  144  of the processor system  14 . The processor system  14  has a power output  142  which provides power to the amplifier  816  and the accelerometer power input  130 . Three outputs from the processor system make up the threshold comparator output  146 . The threshold comparator output  146  connects to the annunciator input  162 . In this embodiment three LEDs  810 ,  812 ,  814  and their transistor drivers make up the annunciator  16 . 
         [0057]    In operation, the battery  802  and voltage regulator  804  provide a suitable voltage for the other accelerometer system components. The processor system  14  initializes when the switch  806  of the power supply  12  turns on. During initialization, internal registers are set up, a value is established for tilt compensation and threshold values are established. The processor system  14  under program control then turns on the accelerometer  13 , via the power output  142  and the accelerometer power input  130 . The accelerometer input  144  of the processor system  14  receives the accelerometer output  132 , buffered by amplifier  816 . Internally the processor system  14 , under program control, performs filtering, tilt compensation and comparison of the measured accelerometer value against three threshold values. The three comparisons determine the state of the three lines which make up the threshold comparator output  146 . If a threshold is exceeded by the acceleration value, the program activates the corresponding signal of the threshold comparator output  146 . The annunciator  16  illuminates an LED  810 ,  812 ,  814  if the corresponding signal in the annunciator input  162  is activated by a signal in the threshold comparator output  146 . The processor program then sets an internal timer and/or counter based on acceleration activity, turns off the accelerometer  13  and goes into a low power sleep state until the timer expires. At timer expiration, the program again turns on the accelerometer  13  and repeats the process. 
         [0058]    It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various other embodiments, changes, and modifications may be made therein without departing from the spirit or scope of this invention and that it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention, which is defined in the following claims.