Airspeed Adaptive Cruise Control for Ground Vehicles

Abstract

A system and method for implementing an airspeed adaptive cruise control system on ground vehicles that automatically slows vehicle groundspeed during headwinds and increases groundspeed during tailwinds. This behavior acts to reduce the energy cost associated with headwinds and capture the energy benefit obtained with tailwinds. In the method, multiple operating modes are presented that can be user selected to optimize on minimum energy consumption, fastest average speed while still harvesting energy from tailwinds, and a balance in between the two methods. The system utilizes multiple sensors, such as airspeed, groundspeed, and vehicle proximity detectors to provide reliable system functionality in a wide range of operating conditions. In some implementations, a combined speedometer with groundspeed and airspeed indicator dials is used to quickly communicate the condition and magnitude of headwinds or tailwinds.

Claims

1. A computerized airspeed adaptive cruise control system comprising: a groundspeed sensor configured to measure groundspeed of a vehicle with respect to the ground; an airspeed sensor configured to: receive a magnitude of vehicle headwind defined as a velocity of wind moving in an opposite direction of vehicle travel and a magnitude of vehicle tailwind defined as a velocity of wind moving in the same direction of vehicle travel; receive a measure of ground speed of the vehicle; and calculate a vehicle airspeed defined as vehicle ground speed plus the magnitude of vehicle headwind minus the magnitude of vehicle tailwind; a throttle position actuator configured to actuate a throttle of a vehicle; at least one computerized controller configured to: monitor vehicle airspeed and vehicle groundspeed provided by the groundspeed and airspeed sensors; accept a positive airspeed set point from either a vehicle operator, an autonomous driving computer or a computerized controller wherein said set point is optionally subject to limiting parameters including energy efficiency, arrival time, maximum or minimum acceptable groundspeed, comfort of the vehicle operators or others; instruct a vehicle operator to adjust the throttle position actuator and/or automatically adjust the throttle position actuator to increase vehicle ground speed when an absolute value of the vehicle airspeed is less than the vehicle airspeed set point by more than a first threshold amount and/or decrease vehicle ground speed when an absolute value of the vehicle airspeed is greater than the vehicle airspeed set point by more than a second threshold amount; and a user interface configured to receive an input from the at least one computerized controller and to provide vehicular data to the vehicle operator or an autonomous driving computer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a block diagram illustrating the system architecture in a vehicle for one embodiment of the invention;

[0020] FIG. 2 is a block diagram illustrating the system architecture including adjustable parameters in a vehicle for one preferred embodiment of the invention;

[0021] FIG. 3 is a flowchart showing an overview of an airspeed adaptive cruise control system;

[0022] FIG. 4 is a chart plotting vehicle groundspeed and airspeed versus time as both headwinds and tailwinds are encountered;

[0023] FIG. 5 is a side by side depiction of a speedometer that combines groundspeed and airspeed in a single instrument dial showing headwind and tailwind condition views when a vehicle is operating at 70 MPH groundspeed in both cases;

DETAILED DESCRIPTION

[0024] Disclosed herein is a system and method for adjusting vehicle groundspeed in an adaptive fashion to maintain constant vehicle airspeed and potentially reduce energy consumption compared to maintaining a constant groundspeed. The system is implemented by an electronic programmable control unit, but could also be implemented mechanically. The system performs airspeed adaptive actions when the system determines a conditional threshold, such as strong headwinds and lack of vehicle proximity, has been reached. The system may also perform airspeed adaptive actions in fully driver controlled operating condition where engine throttle sensitivity is modulated in part by vehicle airspeed.

System Architecture

[0025] Referring initially to the drawings, FIG. 1 is block diagram outlining a preferred embodiment of the invention implemented electronically. The airspeed sensor 10 and groundspeed sensor 12 are connected to the primary communication bus. The airspeed sensor 12 could be implemented by pitot tube, paddle wheel or by ultrasonic means. The groundspeed sensor 12 could be implemented with a rotating magnetic sensor, computer vision or using a GPS receiver. The throttle position sensor 14 and vehicle proximity detector 16 is also connected to the primary communication bus. The throttle position sensor could be implemented from the existing vehicle throttle position sensor or using a retrofitted sensor. The vehicle proximity detector 16 could be implemented using computer vision, ultrasonic sensor, laser sensor or radar sensor.

[0026] Also referring to FIG. 1, the system memory 18 and system central processing unit 20 are both connected to the primary system communication bus. The central processing unit 20 provides automatic generation of appropriate outputs to perform airspeed adaptive behavior such as maintaining a constant airspeed, harvesting tailwinds, or minimizing the impact of headwinds.

[0027] Also referring to FIG. 1, an interface 22 for communication with other vehicle systems or other external outside connections such as updating firmware is provided. A keypad 24 allows the vehicle driver to configure settings such as adjustable control parameters shown in FIG. 2 or customize operating modes to fit the desired operating behavior, control system calibration, or interact generally with the adaptive airspeed cruise control.

[0028] The display device 26 is used to show real time feedback on system operation, and in some embodiments provide guidance on optimizing fuel consumption with respect to vehicle airspeed. The display device 26 in some embodiments will contain the speedometer shown in FIG. 5 that combines groundspeed and airspeed in a single instrument dial. In some embodiments, the headwind/tailwind status 28 will be displayed via a dashboard light or other simplified display system to minimize cost and provide intuitive visual cues about current airspeed conditions with respect to vehicle groundspeed.

[0029] In other embodiments of an airspeed adaptive cruise control shown in FIG. 1, a vehicle operator may not use the automatic active control directly, but have the throttle control pedal or equivalent, that results in throttle output being modulated in part by the amount of headwind or tailwind detected. This could be referred to as having a soft accelerator pedal that does not respond as sharply when strong headwinds are present, and a sharp accelerator pedal that responds more quickly when tailwinds are present.

[0030] In this partially manual operating mode, the operator avoids unnecessarily consuming energy by accelerating with the throttle into headwinds or maintaining speed into headwinds. This partially manual mode operates without the driver directly selecting an airspeed setpoint, but by the cruise system taking continuous measurements of current ground speed and airspeed conditions. In this embodiment, the vehicle operator can also benefit from increased vehicle speed without a fuel economy penalty when tailwinds occur. Also in this embodiment, the vehicle operator can benefit from full control over vehicle groundspeed for complex traffic scenarios, with a minimized fuel economy penalty due to headwinds. Also in this embodiment, the throttle output modulation can be overridden by the driver requesting a throttle position greater than a certain threshold that can be customized based upon performance requirements of the ground vehicle.

[0031] In all embodiments, the airspeed sensor is critical to enabling airspeed adaptive cruise control behavior. A number of methods exist to measure airspeed such as a pitot tube, hot wire resistance, rotating paddle wheel, and ultrasonic time-of-flight. On a ground vehicle, accurately measuring airspeed can be challenging due to local disturbances from nearby vehicles, cross wind effects, environmental conditions (e.g., dust, rain and snow), corrosive salt environments and biological residue such as from insects and birds. Other debris encountered on roads such as tire rubber, vehicle parts, trash, sand, brush, trees, and others objects are all potential sources of error and damage to a vehicle based airspeed sensor. For these reasons, pitot tube and ultrasonic based airspeed measurement are generally more reliable methods. However, for cost minimization, other airspeed measurement systems could be used such as mechanical systems.

[0032] In some embodiments, multiple speed sensors in different vehicle positions will be used to consolidate airspeed data into a single estimated value. In all embodiments, proper maintenance of the airspeed sensor is important to the accurate function of the airspeed adaptive cruise control system.

[0033] Positioning of the airspeed sensor is important for reliable functioning of an airspeed adaptive cruise control system on ground vehicles. In some embodiments, multiple airspeed sensors will be used to reduce the effects of positioning on measured airspeed. Placement at the highest feasible point on a vehicle is desirable to have undisturbed air and prevent excessive variability in measured airspeed due to vehicles ahead slowing down measured airspeed. High placement is also desirable to provide a better overall sense of the large scale prevailing wind direction. Placement of the airspeed sensor at the furthest forward position that is feasible is also desirable to minimize airspeed disturbances caused by the vehicle such a system is mounted upon.

[0034] In some embodiments, particularly where the airspeed sensor is mounted low or towards the rear of the vehicle, calibration of the airspeed sensor is necessary to account for vehicle specific airspeed variations caused by bodywork, antennas, large scale vehicle aerodynamic effects, rotating wheels and other variables. A typical calibration routine would include using a GPS based groundspeed meter along with calm environmental wind conditions to do a velocity sweep across the range of vehicle airspeeds to determine a correlation matrix of measured airspeed versus actual airspeed. It is also necessary to calibrate the airspeed sensor to ensure that the derived measurement of headwind and tailwind speed reflect actual conditions.

[0035] In FIG. 2, the system architecture including key system tuning parameters is shown. These adjustable parameters may be enabled to be adjusted by the end user or may be pre-selected to provide certain behaviors required by vehicle operators. First, with respect to the primary airspeed sensor 10 shown in FIG. 2, the headwind/tailwind airspeed threshold 52 is a critical operating parameter that is selected to provide a reasonable balance between sensitivity and lag in triggering airspeed adaptive behavior such as acceleration or deceleration of vehicle groundspeed. The headwind/tailwind airspeed threshold 52 also controls how aggressively the airspeed adaptive cruise control system responds to headwinds or tailwinds. For example, in one embodiment, a 5 MPH detected headwind change from calm wind should not trigger airspeed adaptive behavior to improve occupant comfort.

[0036] Second with respect to the primary airspeed sensor 10 shown in FIG. 2, the length of time to ignore temporary airspeed fluctuation parameter 58 is a critical operating parameter that is selected to avoid overly frequent changes in vehicle groundspeed that could actually increase energy consumption.

[0037] Third with respect to the primary airspeed sensor 10 shown in FIG. 2, the length of time to calculate a running average of vehicle airspeed 60 is a critical parameter to ensure the air adaptive cruise control gradually adapts to changing headwind/tailwind conditions as opposed to short fluctuations caused by vehicles ahead, trees, road barriers, road signs, bridges, oncoming traffic, wind, bodies of water, open expanses of terrain and other factors that do not represent sustained headwind/tailwind effects.

[0038] In FIG. 2, with respect to the throttle position actuator 14, the acceleration/deceleration rate 54 is a key parameter to control overly sensitive vehicle movement that disturbs occupants or cargo as adaptive airspeed behavior occurs. The acceleration/deceleration rate 54 parameter also prevents excess energy consumption from unnecessarily high rates of acceleration or deceleration as groundspeed adapts to changing airspeed condition.

[0039] In FIG. 2, with respect to the vehicle proximity detector 16, the variable distance ahead threshold 56 is a key parameter to control unnecessary groundspeed changes when in the wake of a vehicle ahead. The variable distance ahead threshold 56 sets the minimum distance from the driver's vehicle to the next vehicle ahead to ignore vehicle airspeed measurements. In a condition where a vehicle is in close proximity ahead of the driver's vehicle, measured vehicle airspeed will likely indicate significantly below the prevailing vehicle airspeed and could incorrectly trigger airspeed adaptive behavior temporarily resulting in slow groundspeed.

[0040] The variable distance ahead threshold 56 parameter also allows the system to function robustly in heavy traffic and close proximity driving while still providing some of the benefits of an airspeed adaptive cruise control system when opportune conditions exist.

Overview of Operation

[0041] In FIG. 3, a flowchart showing an overview of an airspeed adaptive cruise control system provides a detailed view of the airspeed adaptive behavior. First, vehicle groundspeed 30, as well as vehicle airspeed 32 is tracked at a specific interval and is stored in memory. The currently active vehicle airspeed setpoint 34 is also stored in memory and generally is an important input to the goal seeking baseline that controls the airspeed adaptive behavior.

[0042] When vehicle airspeed is lagging behind the airspeed setpoint at decision point 36 the next step is to check for vehicle proximity ahead at decision point 38. This prevents an unnecessary change in groundspeed 40 when driving in close proximity of other vehicles. If no vehicles are detected in close proximity, the system behaves according to tailwind conditions and increases groundspeed 42 to take advantage of the favorable tailwind operating conditions until measured airspeed is equal to the vehicle airspeed setpoint 34. This behavior results in greater vehicle groundspeed without an energy penalty.

[0043] With respect to decision point 36, if vehicle airspeed is not lagging behind the airspeed setpoint, then decision point 44 is evaluated to determine if vehicle airspeed is rising above the airspeed setpoint. If decision point 44 is evaluated true, then decision point 46 is evaluated to check for vehicle proximity. If vehicle proximity is not detected, the airspeed adaptive behavior of decreasing groundspeed 50 occurs until measured airspeed is equal to the vehicle airspeed setpoint 34. This behavior results in lesser vehicle speed to prevent an energy penalty due to headwinds. If vehicle proximity is detected then existing vehicle groundspeed 48 is maintained and the vehicle groundspeed continues until another operating iteration is evaluated to check for variable conditions that may occur.

[0044] Beyond the established flow chart behavior from FIG. 3, several user configurable operating modes can be selected to reflect the specific needs of the driver. Depending on the desired system behavior, three operating modes may be selected: compensate for headwind only, compensate for headwind and tailwind, compensate for tailwind only.

[0045] If operating mode compensate for headwind only is selected, then airspeed adaptive cruise control will never increase vehicle groundspeed, and only decrease groundspeed when headwinds occur. The operating mode generally provides the minimal energy consumption and slowest average vehicle groundspeed.

[0046] If operating mode compensate for headwind and tailwind is selected the airspeed adaptive cruise control will speed up for tailwinds and slow for headwinds. This operating mode generally provides a balance between groundspeed and minimal energy conservation, but depends upon actual headwind or tailwind encountered.

[0047] If operating mode compensate for tailwinds only is selected the airspeed adaptive cruise control will only speed up when tailwinds occur. This operating mode generally provides the fastest average vehicle groundspeed and can automatically harvest energy from tailwinds to be used to increase vehicle groundspeed without an energy penalty.

[0048] It is also desirable to have an upper and lower limit on the total change in vehicle groundspeed. For all the operating modes, a maximum groundspeed deviation can be selected. For example, it generally will not be desirable for the vehicle to slow below minimum posted groundspeed limits nor would it be desirable for the vehicle to exceed the maximum posted groundspeed limit. This upper and lower limit is individually selectable to allow the driver to configure the system to meet specific operating requirements.

[0049] In FIG. 4, a graphical depiction of the airspeed adaptive cruise control behavior is plotted over an extended time period 64 of more than 30 minutes. Vehicle groundspeed 86 is plotted on the left hand axis 62 while vehicle airspeed 70 is plotted on the right hand axis 66. In the middle of the chart, the 65 MPH airspeed setpoint 82 is plotted in a dashed horizontal line to give a reference of the airspeed adaptive cruise control system goal. The system goal 70 is highlighted as being roughly constant because the system does not instantaneously adjust to changes in airspeed.

[0050] In FIG. 4, peak tailwind 72 is identified as the point of maximum vehicle groundspeed at 75 MPH which correlates to a 10 MPH tailwind. Note that at this point, vehicle airspeed is still equal to the 65 MPH airspeed setpoint 82. The tailwind labels 80 show the region of tailwind functionality 36 by the airspeed adaptive cruise control system.

[0051] To further clarify when headwinds or tailwinds exist, and the specific functionality triggered during those time periods, the chart has tailwind behavior regions 76 and headwind behavior regions 88 labeled.

[0052] In FIG. 4, peak headwind 84 is identified at 45 MPH vehicle groundspeed, while simultaneously encountering a 20 MPH headwind. At this point, the airspeed adaptive cruise control has slowed vehicle groundspeed until the target airspeed setpoint is achieved. To clarify the operation in headwind conditions, the sum of the 45 MPH groundspeed and 20 MPH headwind result in the target airspeed setpoint of 65 MPH. The headwind labels 78 show the region of headwind functionality 44 by the airspeed adaptive cruise control system.

Visual Display

[0053] In FIG. 5, a speedometer that combines groundspeed and airspeed in a single instrument 90 is depicted. The instrument 90 may be implemented mechanically, electromechanically, or fully digitally using a display screen. The groundspeed dial 99 and markers occupy the outer ring, as well as the corresponding longer groundspeed dial indicator 92. The airspeed dial 91 and markers occupy the inner ring, as well as the corresponding shorter airspeed dial indicator 94.

[0054] In the headwind case of FIG. 5 shown on the left hand side, the shaded region 96 represents the magnitude of the airspeed penalty in an easily visualized method. The shaded region 96 may be colored differently than the shaded region 98 on the right hand side showing the tailwind case. Such colors as red for the headwind shaded region 96 and green for the tailwind shaded region 98 may be selected and actively displayed on a mechanical, electromechanical or fully digital representation of the speedometer 90.

[0055] Also, the area of the shaded region 96 will increase with an increasing headwind and the highlighted area of shaded region 98 will increase with an increasing tailwind. The area of the shaded regions 96 and 98 will be updated in real time, or close to real time depending on the configuration of system parameters and operating modes selected.

[0056] Although the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. For example, the invention could be adapted for use in an aircraft or on a bicycle with certain modifications. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.

Speed Governor Implementation

[0057] In other embodiments of the airspeed adaptive cruise control, a system using a speed governor may be implemented. Speed governors or sometimes referred to as speed limiters, are a technology used on ground vehicles, and particularly on commercial trucks. One benefit of a speed governor is that of increased fuel economy by limiting maximum vehicle groundspeed, even when the accelerator pedal is fully depressed. However, a limitation of the current state of speed governor art is that it is manually set by the owner of the ground vehicle to a specific groundspeed and is not frequently changed. For example, in commercial truck fleets, the maximum allowable speed governor set point is occasionally changed by increasing maximum groundspeed to improve retention of employee vehicle operators.

[0058] The major benefit of airspeed adaptive cruise control with a speed governor is ease of implementation and improved safety. Fuel economy benefits are likely to be reduced somewhat compared to a non-speed governor based approach. Fuel economy benefits are reduced because the change in speed governor setting may not be immediate when aerodynamic force of headwind or tailwind changes. For safety, it is also not ideal for speed governor changes to occur at a short interval, such as 30 seconds. However, speed governor changes at 15 minute intervals for example, would be less intrusive to the vehicle operator. It should also be understood that this is only an example, and changes at other intervals on the order of minutes or hours are also contemplated.

[0059] The reduction in fuel economy from a speed governor based approach is somewhat offset by benefits of relatively low cost installation of airspeed adaptive cruise control technique in a vehicle that already posses a speed governor and vehicle wireless data connection. In addition, the ability to remotely change a speed governor set point via a wireless data connection from a centralized computer server is highly desirable for an owner of a truck fleet. This adaptive functionality allows the owner of a truck fleet to centrally manage the fuel economy of an entire truck fleet on a real time basis.

[0060] For example, high fuel economy could be attained by the owner of a truck fleet setting all the speed governors for the entirety of the truck fleet to 60 miles per hour. In another situation, during a time of high tailwinds, the owner of a truck fleet could set all the speed governors for the entirety of the truck fleet to 70 miles per hour. This tuning of the fleet speed governor is accomplished manually or via an automated system depending upon specific optimization parameters desired by the owner of a truck fleet. A truck fleet owner could also set the speed governor based upon certain regions or individual states.

[0061] This adaptive functionality also allows the owner of a truck fleet to adapt to other variables such as market supply and demand conditions, freight rates, vehicle operator pay, vehicle operator bonuses, vehicle operator penalties, driver retention, driver hours of service limitations, autonomous vehicle regulations, autonomous vehicle maintenance requirements, regional speed limits, regional weather conditions, and other factors important to truck fleet and vehicle owners.

[0062] Another major benefit offsetting the reduced fuel economy of the speed governor approach is vehicle operator familiarity, and particularly with operators of commercial trucks. This is a major safety enhancement of the system because of vehicle operator familiarity. Because basic functions of a speed governor are well understood by vehicle operators, the speed governor change on a regular interval will not cause undue confusion or difficulty in vehicle operation.

[0063] While regular speed governor updates are used in the example above, the update interval can be adjusted by the vehicle owner or in certain cases the vehicle operator to satisfy their specific requirements such as fuel economy, vehicle operator feedback and time critical delivery requirements.

[0064] Another major benefit of speed governor based airspeed adaptive cruise control is in allowing increased employee vehicle operator satisfaction through unlocking of a speed governor increase during periods of favorable tailwinds. This boost of the speed governor set point is potentially an enjoyable and positive reinforcement to employee vehicle operators, while simultaneously improving overall fuel economy for a truck fleet owner over the vehicle lifetime. The simultaneous fuel economy benefit occurs because the speed governor boost condition may be deactivated during times of headwind or zero wind velocity. The deactivation of the boost condition is accomplished by reducing the speed governor setpoint from a higher groundspeed to a lower groundspeed.

[0065] This accomplishes a similar effect to slowing the vehicle during headwind conditions, but with less vehicle operator frustration by actively slowing into headwinds. Instead, only a boosting of speed occurs during opportune tailwind conditions and then a return to the default lower speed governor set point. In this mode of operation, the lower default speed governor set point is also an adjustable parameter selected to optimize truck fleet owner requirements.