Patent Publication Number: US-7214110-B1

Title: Acceleration control system for a marine vessel

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is generally related to an acceleration control system and, more particularly, to a system which allows the operator of a marine vessel to select an acceleration profile according to which the propulsion system of the marine vessel will be controlled, particularly during initial acceleration from a stationary condition to a final velocity. 
   2. Description of the Related Art 
   Many different devices and methods are known to those skilled in the art for controlling the speed of a marine vessel. 
   U.S. Pat. No. 5,074,810, which issued to Hobbs et al. on Dec. 24, 1991, describes an automatic speed control system for boats. The speed of the boat is measured and compared to a desired speed set by the operator and the speed of the boat engine is adjusted to minimize the difference between the desired speed and the actual speed. The device further incorporates features allowing incremental adjustment of the desired speed, storage of several of these speeds for future use, and a safety feature causing the system to behave as though it were a conventional manual type if the operator makes a gross change to the setting of a manual throttle lever. 
   U.S. Pat. No. 5,110,310, which issued to Hobbs on May 5, 1992, describes an automatic speed control system for boats. Actual speed is compared to a desired speed set by the operator and the speed of the boat engine is adjusted to minimize the difference between the desired speed and the actual speed. Engine speed is further adjusted to prevent or minimize changes in the speed of the boat caused by the forces on the boat due to a water skier. The device further incorporates features to reduce the likelihood of speed measurement errors due to a malfunctioning speed measuring device. 
   U.S. Pat. No. 5,700,171, which issued to Horton on Dec. 23, 1997, describes a speed control system. It comprises speed sensors which output to a controller which, in turn, outputs to a servo motor. The servo is connected to the inner cable of a coaxial cable, the outer sheath of which is lodged between a buttress and the engine throttle. The distance between the buttress and the engine throttle lever is, at least when the throttle is closed, shorter than the length of the outer sheath such that the outer sheath obtains a curved configuration. The inner cable extends beyond the engine throttle lever to a support. Accordingly, when the controller operates the servo to draw in the inner cable, the outer sheath is urged to straighten and, thereby, push against the engine throttle lever to open it. Conversely, when the inner cable is paid out, the outer sheath is relaxed to allow the engine throttle lever to close. 
   U.S. Pat. No. 6,109,986, which issued to Gaynor et al. on Aug. 29, 2000, discloses an idle speed control system for a marine propulsion system. The system controls the amount of fuel injected into the combustion chamber of an engine cylinder as a function of the error between a selected target speed and an actual speed. The speed can be engine speed measured in revolutions per minute or, alternatively, it can be boat speed measured in nautical miles per hour or kilometers per hour. By comparing target speed to actual speed, the control system selects an appropriate pulse width length for the injection of fuel into the combustion chamber and regulates the speed by increasing or decreasing the pulse width. 
   U.S. Pat. No. 6,485,341, which issued to Lanyi et al. on Nov. 26, 2002, discloses a method for controlling the average speed of a vehicle. The speed of the vehicle is controlled over a predetermined time period, or indefinitely, or distance length. The system comprises the steps of selecting a desired average speed, measuring an actual speed, and maintaining a cumulative error determined as a function of the difference between the average speed and the actual speed and the time over which the actual speed measurement was taken. Based on the cumulative total or speed time error, a compensatory speed is calculated that will reduce the cumulative speed time error to an acceptable tolerance range within a selected period of elapsed time. Although particularly applicable to competition situations in which an average speed is dictated for use over a particular competition course, the average speed controlling method can be used in other situations where the average speed of a vehicle must be controlled. 
   U.S. Pat. No. 6,738,708, which issued to Suzuki et al. on May 18, 2004, describes an engine speed controller for a marine propulsion engine. An electronically controlled engine speed system for an outboard motor regulates the speed of the engine to insure proper watercraft speed. A remote input device can program the preferred embodiments of the system. The preferred embodiments of the system recognize an engaged transmission and control engine speed by changing the ignition timing, fuel injection amount, and throttle bypass valve. 
   U.S. Pat. No. 6,855,020, which issued to Kaji on Feb. 15, 2005, describes a running control device for a watercraft. The device for a watercraft with a propulsion device capable of controlling propulsion, comprises a propulsion control section which controls propulsion, based on predetermined input information, the propulsion control section comprises a target propulsion calculation module for determining a target propulsion, based on predetermined input information including at least velocity of the watercraft and an operation amount calculation module for determining the amount of operation of the propulsion device, based on predetermined input information so as to obtain the target propulsion determined by the propulsion calculation module. 
   The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
   In certain applications of marine vessels, such as towing a water skier or wake boarder, the rate of acceleration from a standstill position to a final velocity condition is often as important or more important than maintaining a steady velocity for the water skier. If the acceleration is too rapid, novice or intermediate water skiers may not be able to satisfactorily move from a resting position to a water skiing position wherein the skier is being towed at a final velocity behind the marine vessel. An expert water skier, on the other hand, may wish to accelerate more rapidly from a resting position in the water to a position and condition in which the water skier is being pulled at a final velocity behind the marine vessel. 
   It would therefore be significantly beneficial if the acceleration of the watercraft can be controlled precisely to perform according to a preselected acceleration curve and repeat that curve during subsequent accelerations of the marine vessel from a resting condition to a final velocity condition. 
   SUMMARY OF THE INVENTION 
   An acceleration control method for an engine of a marine vessel, in accordance with a preferred embodiment of the present invention, comprises the steps of receiving a start command, selecting an acceleration profile, and controlling the speed of the engine according to the selected acceleration profile. The acceleration profile can comprise a first segment associated with a first period of time and a second segment associated with a second period of time. The first segment of the acceleration profile extends from an initial engine speed to a speed which is generally equal to a desired final speed. The second segment of the acceleration profile extends from the desired engine speed, at the end of the first period of time, to a speed which is greater than the desired final speed by a preselected magnitude and then to the desired engine speed at the end of the second period of time. The second segment can comprise an acceleration portion and a deceleration portion which both occur during the second period of time. The start command can be caused by a sudden movement of a manually operated throttle handle. When the manually operated throttle handle is suddenly moved from a first position to a second position at a rate of movement which exceeds a preselected magnitude, this action can be interpreted as the start command by the present invention. 
   The acceleration during the first segment can be generally constant. The method of the present invention, in a preferred embodiment, can further comprise the step of receiving a signal representing a selection of the acceleration profile from a plurality of potential acceleration profiles. This signal can typically be provided by the operator of the marine vessel as the operator makes the selection from the plurality of potential acceleration profiles. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment of the present invention in conjunction with the drawings, in which: 
       FIG. 1  is a graphical representation of an exemplary acceleration profile; 
       FIG. 2  is a schematic representation of a marine vessel with the various components used to perform the method of the present invention; 
       FIG. 3  is a table showing the parameters used to describe various acceleration profiles; and 
       FIG. 4  is a graphical representation of the rate of movement of a throttle handle in combination with five acceleration profiles. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
     FIG. 1  is a graphical representation of an exemplary acceleration profile  10  for a marine vessel. The acceleration profile  10 , illustrated as engine speed as a function of time, comprises a first segment  12  and a second segment  14 . The first segment  12  is associated with a first period of time  21  and the second segment  14  is associated with a second period of time  22 . The first segment  12  of the acceleration profile  10  extends from an initial engine speed  31  to an engine speed  32  which is generally equal to a desired engine speed, or final engine speed, which is represented by dashed line  36 . The second segment  14  of the acceleration profile  10  extends from that desired engine speed, at point  32 , which occurs at the end of the first period of time  21  represented by dashed line  38 , to a speed which is somewhat greater than the desired final speed  36 . This greater engine speed is identified by dashed line  40  in  FIG. 1 . The greater speed  40  is of a greater magnitude than the desired final engine speed  36  by a preselected magnitude which is illustrated by arrow  42 . 
   With continued reference to  FIG. 1 , it can be seen that the second segment  14  can comprise an acceleration portion, during the time period identified by arrow  50 , and a deceleration portion during the time period represented by arrow  52 . Both the acceleration portion and the deceleration portion occur during the second period of time  22  in a preferred embodiment of the present invention. 
     FIG. 2  is a schematic representation of the environment in which a preferred embodiment of the present invention can typically be used. Dashed line box  60  represents the environment of a marine vessel in which an engine  62 , with a tachometer  64 , provides marine propulsion for the vessel. A manually controllable throttle mechanism  68  allows the operator of the marine vessel to control the operating speed of the engine  62 . A microprocessor  70 , such as an engine control module, controls the operating speed of the engine  62  in conformance with signals received from the position of a throttle handle  74  of the manually controlled throttle mechanism. Also shown in  FIG. 2  is a control panel  76  which allows the operator of the marine vessel, in certain embodiments of the present invention, to provide additional information to the microprocessor  70 . Shown in dashed lines in  FIG. 2  is a speedometer  78  which provides signals to the microprocessor  70  in certain embodiments of the present invention. However, it should be understood that the speedometer  78  is not required in all embodiments of the present invention and that a GPS device is also an alternative if velocity measurement is desired. 
   With reference to  FIGS. 1 and 2 , a start command is received by the microprocessor  70  from the manually operated throttle mechanism  68  in a preferred embodiment of the present invention. This can be the sudden movement of the throttle handle  74 , as indicated by the arrow, from a neutral position or idle speed position to a higher speed command with a relatively sudden movement of the handle  74 . The control panel  76  allows the operator of the marine vessel to select an acceleration profile, typically from a portfolio of potential profiles, and provide that selection to the microprocessor  70  for future application when a start command signal is received. 
   With continued reference to  FIGS. 1 and 2 , several characteristics of a preferred embodiment of the present invention can be observed. For example, the first segment  12 , of the acceleration profile  10 , during the first time period  21 , is generally constant. The graphical representation in  FIG. 1  shows this first segment as representing a slightly increasing acceleration rate as the engine speed changes from point  31  to point  32 . However, this acceleration rate can be much more constant than is shown in  FIG. 1 . In other words, the first segment of the acceleration profile can be virtually a straight line extending between points  31  and  32 . After the expiration of the first period of time  21 , an overshoot condition is intentionally provided in a preferred embodiment of the present invention. After achieving the desired final engine speed  36 , at point  32 , the engine speed is increased beyond that desired engine speed  36  to achieve the overshoot represented by arrow  42 . This results in the achievement of the speed represented by dashed line  40 . This continued acceleration occurs in the time period identified by arrow  50 . Then, according to a preselected procedure, the engine speed is decelerated during time period  52  to the desired final engine speed which is achieved at point  80  in  FIG. 1 . 
   The information relating to the acceleration profile, in a particularly preferred embodiment of the present invention, is represented by three parameters for each of five potential acceleration profiles. The information is shown in  FIG. 3 . In this exemplary table of  FIG. 3 , five skill levels are represented. For each level, the rate of acceleration, represented as Δ Demand/sec or Δ Thrust/sec, is stored along with an associated percentage overshoot magnitude. The percentage overshoot magnitude is equivalent to the percentage of the magnitude represented by arrow  42  in  FIG. 1  to the magnitude represented by arrow  86  in  FIG. 1 . If the final desired speed is 3400 RPM, for example, the level three illustration in  FIG. 3  would describe a 10% overshoot, or 340 RPM for three seconds, which would be the difference represented by arrow  42  in  FIG. 1 . In  FIG. 3 , the duration for each level is also stored. This duration represents the magnitude of arrow  21 , measured in seconds, for each of the skill levels. The operator of the marine vessel would select a skill level (e.g. 1–5) prior to providing the next start signal which occurs when the operator rapidly moves the manually operated throttle handle  74  from an initial speed position to a higher speed position. 
     FIG. 4  is a graphical representation of several characteristics. Line  90  represents the throttle position, or position of the handle  74 , represented by the left axis as percentage of the maximum engine speed command. In addition, five acceleration profiles are shown with respect to the right axis in  FIG. 4 . 
   As shown in  FIG. 4 , this particular embodiment of the present invention responds to a rapid movement of the throttle handle  74 , as represented by line  90 , from a zero speed command to a demand greater than the demand, or thrust, needed to achieve the set point throttle command in a relatively short period of time. When this rapid movement of the handle  74  is detected by the microprocessor  70 , one of the illustrated acceleration profiles is followed. It should be understood that, although five profiles are shown simultaneously in  FIG. 4 , only one profile would be applied. That acceleration profile would typically have been previously selected from a choice of potential acceleration profiles by the operator of the marine vessel. In  FIG. 4 , acceleration profile  91  conforms generally with the level one profile in  FIG. 3 , acceleration profile  92  in  FIG. 4  conforms generally with the second level shown in  FIG. 3 , and so on. 
   With reference to  FIGS. 1–4 , it should be understood that the use of a marine vessel to tow a skier can be significantly aided by the preferred embodiment of the present invention which provides consistency during the initial acceleration from a standing position to a final desired boat speed. In the tow sports, such as wake boarding and water skiing, a high degree of precision is often required on the part of both the water skier and the operator of the marine vessel. Cruise control systems, such as those discussed above, are generally known to those skilled in the art and have provided significant help in these endeavors. While known cruise control systems address the steady state, or final desired speed issues for providing the predetermined boat speed, one of the remaining challenges for most tow sports, is the challenge of achieving repeatability and control in the process of “getting up” from a stationary position in the water to a position wherein the water skier is in a standing position and moving at the desired final speed of the marine vessel. Significant variation can occur in the engine torque needed to bring a skier from a stationary position in the water to an “on plane” condition. This engine torque can vary from approximately fifty foot pounds to approximately three hundred fifty foot pounds, depending on the weight of the skier. Repeatability in the acceleration profile during the beginning of the process is significantly important. 
   By using the preferred embodiment of the present invention, the operator of a marine vessel is able to select the skier&#39;s target speed and acceleration profile. The acceleration profiles, as described above, could vary from a relatively delicate starting process to a more aggressive starting process, wherein virtually the full power of the engine can be applied very rapidly. 
   In a preferred embodiment of the present invention, the acceleration profile comprises the initial acceleration portion, or first segment, and an overshoot portion, or second segment. The overshoot portion is perceived by the water skier as a more robust or aggressive start from a stationary position to an “on plane” position. This is a result of the vessel speed lagging the engine speed. 
   Seen in  FIG. 4 , all five levels,  91 – 95 , begin at the same initial engine speed and end at the same final engine speed, but vary significantly in the acceleration rate of the first segment and the overshoot of the second segment. 
   The processes by which the microprocessor  70  shown in  FIG. 2  controls the operating speed of the engine  62  can vary from application to application and according to the various embodiments of the present invention. In a typical application, during the first segment of the acceleration profile and subsequent to a start command, the microprocessor  40  would repeatedly schedule the maximum demand, or thrust, ramp by increasing the opening of the throttle plate of the engine  62 . Adjustments, to increase the rate of throttle plate movement or decrease the rate of throttle plate movement, would be made as a function of the launch intensity level. This limiting function would continuously be performed during the first segment of the acceleration profile. Then, after determining the desired percentage of overshoot for the second segment of the acceleration profile, the microprocessor would perform a generally similar function in order to achieve the desired shape of the acceleration profile, as discussed above in conjunction with  FIG. 1 . Alternatively, the microprocessor of the engine control module could vary the fuel injected into the cylinders of the engine, such as in a direct fuel injected engine, to achieve the desired demand at each instant during the time period of the acceleration profile. It should be understood that those skilled in the art of engine control have many alternative processes that are well known for controlling the engine speed at any particular instant in time. These processes can be performed at each instant in time over the time period of the acceleration profile to achieve the desired profile. 
   Although the present invention has been described in considerable detail and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope.