Patent Publication Number: US-2006010844-A1

Title: Unmanned utility vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application claims the benefit of U.S. Provisional Patent Application Ser. Nos. 60/584,296 filed Jun. 30, 2004 and 60/609,309 filed Sep. 13, 2004. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The subject invention relates to an unmanned utility vehicle for traversing a plot of land, and more specifically to an unmanned, or autonomous, utility vehicle free of hydraulic and belt drive systems.  
      2. Description of the Related Art  
      Various unmanned utility vehicles, such as autonomous lawn mowers, are known to those of ordinary skill in the art and typically include a carriage having a plurality of drive wheels for moving over the plot of land. The drive wheels are driven by an electric motor powered by batteries. The vehicle also includes at least one tool, such as a cutting assembly, supported by the carriage that is powered by an internal combustion engine. In other words, the internal combustion engine is directly engaging and driving the cutting assembly and the electric motors are only driving the drive wheels to propel the vehicle.  
      One disadvantage of these vehicles is that operation of the internal combustion engines to power the tool is a drain on the internal combustion engine and requires operating the internal combustion engine at various speeds to perform the task. For instance, if the tool is a cutting assembly, the internal combustion engine must operate at different speeds, or revolutions per minute (RPM), in order to cut different thicknesses of grass. The internal combustion engine may operate at lower RPM for thinner grass, but have to operate at higher RPM for thicker grass to prevent stalling of the internal combustion engine. Operating at various RPM uses significantly more gas and also produces different harmonics at each of the different speeds which results in additional noise from the vehicle. Another disadvantage is that if the electrical motors malfunction, the vehicle may continue to operate without the malfimction being detected. When such a malfunction is detected, the complexity of these unmanned systems requires the vehicle to be out of commission for various lengths of time. Further, these systems tend to be quite expensive so additional vehicles are generally not available to continue in place of the malfunctioning vehicle.  
      Various manned vehicles, such as riding lawn mowers, are known to those of ordinary skill in the art and include the electric drive motors for propelling the vehicle, as well as having electric motors for running the cutting assembly. Since the vehicles are manned, the drive motors must be sufficiently large to accommodate the weight of the operator in addition to the weight of the vehicle. This requires the electric motors to be significantly more powerful and larger to propel the vehicle, which results in heavier vehicles. These heavier vehicles are likely to damage terrain by leaving large ruts or gouges during operation. Another disadvantage is that these electrical motors tend not to be modular, such that if one of the motors malfimctions or breaks, a new motor specific for such operation must be utilized on the vehicle. Said another way, the electrical motors of these manned vehicles generally are not modular.  
     SUMMARY OF THE INVENTION AND ADVANTAGES  
      The subject invention provides an unmanned utility vehicle for traversing a plot of land. The vehicle comprises a carriage having first and second drive wheels for moving over the plot of land and first and second electric drive motors operatively connected to first and second drive wheels. A first drive motor controller is operatively connected to the first electric drive motor and a second drive motor controller is operatively connected to the second electric drive motor. The vehicle also comprises at least one tool supported by the carriage for operation, at least one electric tool motor engaging the tool and supported by the carriage, and a tool motor controller operatively connected to the electric tool motor. A power supply is supported by the carriage for powering each of the electric drive motors and the electric tool motor. A main controller communicates with the drive motor controllers and the tool motor controller to control the electric drive and tool motors. A controller area network interconnects the main controller, the drive motor controllers, and the tool motor controller for facilitating communication therebetween to improve operation and modularity of the vehicle.  
      Another embodiment of the subject invention provides an autonomous lawn mower that comprises a carriage, a guidance assembly supported by the carriage for navigating the vehicle, and first and second electric drive motors connected to first and second drive wheels. A first drive motor controller is operatively connected to the first electric drive motor and a second drive motor controller is operatively connected to the second electric drive motor. The lawn mower further comprises at least one mower deck supported by the carriage and at least one electric mower deck motor engaging the mower deck. A mower deck motor controller is operatively connected to the electric mower deck motor. A main controller communicates with the guidance assembly, the drive motor controllers and the mower deck motor controller to control the electric drive and mower deck motors.  
      The lawn mower includes a plurality of rechargeable batteries for powering each of the electric drive motors and the electric mower deck motor. An internal combustion engine is used in combination with a generator disposed between the internal combustion engine and the batteries for recharging the batteries. The electric drive and the mower deck motors are brushless electric motors such that the electric drive and the mower deck motors are controlled by the main controller.  
      In another embodiment, the lawn mower includes a fuel cell for powering each of the electric drive motors and the electric mower deck motor.  
      The subject invention overcomes the disadvantages that characterized the related art vehicles. Specifically, the subject invention provides a small, lightweight, and energy efficient vehicle. The vehicle is free of any belt or hydraulic systems resulting in a lighter vehicle with reduced potential for damaging the terrain. The vehicle also has a modular design that is able to adjust operation of various electric motors in real time to reduce or eliminate any down time. Further, if any of the motors become inoperable, the modular design allows any other electric motor to be switched for the defective motor and replaced in order to continue operation. Additionally, the subject invention allows for very precise operation of the vehicle and the tool that has not previously been possible with the related art assemblies at a reasonable cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
       FIG. 1  is a top perspective view of an unmanned utility vehicle according to the subject invention;  
       FIG. 2  is a bottom perspective of the unmanned utility vehicle shown in  FIG. 1 ;  
       FIG. 3  is a top perspective view of the unmanned utility vehicle shown in  FIG. 1  having a cover removed;  
       FIG. 4A  is a top perspective view of one embodiment of a drive assembly, a tool assembly, a lift assembly, and a power supply of the unmanned utility vehicle;  
       FIG. 4B  is a top perspective view of another embodiment of a drive assembly, a tool assembly, a lift assembly, and a power supply of the unmanned utility vehicle;  
       FIG. 5  is a schematic flowchart of the unmanned utility vehicle;  
       FIG. 6  is a side view of the drive assembly;  
       FIG. 7  is a cross-sectional view taken along Line  7 - 7  shown in  FIG. 6 ;  
       FIG. 8  is an exploded view of the drive assembly shown in  FIG. 6 ;  
       FIG. 9  is an exploded view of a drive motor housing including a drive motor and a drive motor controller;  
       FIG. 10  is a cross-sectional view of the drive motor shown in  FIG. 9 ;  
       FIG. 11  is an exploded view of the drive motor shown in  FIG. 9 ;  
       FIG. 12  is an exploded view of a gear assembly shown in  FIG. 9 ;  
       FIG. 13  is a side view of the tool assembly;  
       FIG. 14  is a cross-sectional view of the tool assembly shown in  FIG. 13 ;  
       FIG. 15  is an exploded view of the tool assembly shown in  FIG. 13 ;  
       FIG. 16  is an exploded view tool motor housing including a tool motor and a tool motor controller;  
       FIG. 17  is an exploded view of the tool motor shown in  FIG. 16 ;  
       FIG. 18  is an exploded view of the lift assembly including a lift mechanism and a lift motor housing;  
       FIG. 19  is an exploded view of the lift mechanism shown in  FIG. 18 ;  
       FIG. 20  is an exploded view of the lift motor housing including a lift motor and a lift motor controller;  
       FIG. 21  is a partial sectional view of the power supply shown in  FIG. 4 ;  
       FIG. 22  is an exploded view of a generator; and  
       FIG. 23  is a top perspective view of the unmanned utility vehicle having a user interface mounted into the cover.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, an unmanned utility vehicle  30  for traversing a plot of land is shown generally at in  FIG. 1 . The unmanned utility vehicle  30  may include, but is not limited to, an autonomous lawn mower, vacuum cleaner, sweeper, or scrubber, polisher, sander, or buffer, beach cleaner, ice groomer, or line painter.  
      The vehicle  30  includes a carriage  32  having first and second drive wheels  34 ,  36  for moving over the plot of land, a bumper  38 , and a cover  40 . With reference to  FIG. 1 , the cover  40  is movable between an open position and a closed position with the cover  40  being shown in the open position. The vehicle  30  may also includes at least one non-drive, or dummy, wheel  42  that is driven by the drive wheels  34 ,  36 . For example, the non-drive wheel  42  may be a caster-type wheel that is capable of swiveling in multiple directions. Alternatively, the vehicle  30  have each of the wheels being driven, i.e., three or more wheels that are driven to improve accuracy.  
      A guidance assembly  44  is supported by the carriage  32  for guiding the vehicle  30  about the plot. The guidance assembly  44  may be selected from at least one of a laser navigation system, a radio frequency navigation system, a GPS navigation system, and a camera navigation system. The guidance assembly may also include a platform roll pitch controller  43  and a turret rotation controller  45 . However, it is to be appreciated that other guidance assemblies  44  may be employed with the subject invention so long as the vehicle  30  is autonomous or unmanned. Such guidance assemblies  44  are disclosed in U.S. Pat. Nos. 6,556,598 and 6,598,692, which are commonly assigned to assignee of the subject invention and which are incorporated herein by reference. As discussed above, the related art assemblies have additional weight due to an operator having to ride the vehicle  30  and due to the vehicle  30  needing to be sufficiently large to support the operator. Since the subject invention is unmanned, the vehicle  30  has lesser weight and does not need to be as heavy, thereby reducing the amount of damage that may be done during operation. Still another advantage is that the vehicle  30  has reduced fuel consumption as well.  
      Depending upon the particular type of vehicle  30 , the vehicle  30  includes at least one tool  46  supported by the carriage  32  for performing an operation. It is to be appreciated that the tool  46  may be carried by the carriage  32 , pulled behind the carriage  32 , or pushed in front of the carriage  32 . Referring to  FIG. 2 , the vehicle  30  is illustrated as a lawn mower and the tool  46  is a mower deck having three mower assemblies. The mower deck may have more or fewer decks depending upon a desired width of cut, such as 2 or 5. The mower assemblies include three individual domes  48  that house a blade  50  for mowing and cutting grass. For clarity, the subject invention will be described for use with a lawn mower without limitation. It is to be appreciated that reference numerals may be used in connection with the same component even though the identifier is different, i.e., both the vehicle and lawn mower may be numeral  30  and the tool and mower deck are both numeral  46 . However, the tool  46  may be selected from at least one of a mower assembly, a sweeping assembly, a cleaning assembly, and a painting assembly for the particular application. The vehicle  30  may further include an electric lift motor  52  operatively connected to the tool  46  for positioning the tool  46  for use, such as by raising or lowering.  
       FIG. 3  is a top perspective view of the vehicle  30  having the cover  40  removed. The vehicle  30  includes a main controller  54  for controlling the vehicle  30  as will be described in more detail below. Referring to  FIG. 4A , the carriage  32  and cover  40  of the vehicle  30  have been removed to more easily describe the additional components. The vehicle  30  includes a first electric drive motor  56  and a second electric drive motor  58  operatively connected to the first drive wheel  34  and the second drive wheel  36 . The vehicle  30  also includes at least one electric tool motor  60  engaging the tool  46  that is also supported by the carriage  32 . In  FIG. 4A , the vehicle  30  includes three tool motors for driving each of the mower decks. A wiring harness  62  interconnects each of the motors  52 ,  56 ,  58 ,  60  to the main controller  54 .  
      The vehicle  30  further includes a power supply  64  supported by the carriage  32  for powering the electric lift motor  52 , the electric drive motors  56 ,  58 , and the electric tool motor  60 . In the embodiment shown in  FIG. 4A , the power supply  64  comprises a plurality of batteries  66  for running the electric lift motor  52 , the electric drive motors  56 ,  58 , and the electric tool motor  60 . An internal combustion engine  68  and a generator  70  may be used to charge the batteries  66 . An engine controller  87  may be used to monitor the performance of the internal combustion engine  68 , the generator  70 , and the batteries  66 . The batteries  66  may also be used as an electric starter for the internal combustion engine  68 . A fuel tank  72  ( FIG. 3 ) stores the fuel for operating the internal combustion engine  68 . A side view of the internal combustion engine  68  is shown in  FIG. 21 . The generator  70  is preferably an alternator and is shown in  FIG. 22 . Since the internal combustion engine  68  only charges the batteries  66 , the internal combustion engine  68  may be operated at a constant revolutions per minute (RPM). One advantage of operating the internal combustion engine  68  at constant RPM is that noise and fuel consumption is reduced. Further, the subject invention includes a muffler  74  connected to the internal combustion engine  68  that muffles a predetermined harmonic. Because the internal combustion engine  68  operates at a nearly constant RPM, the muffler  74  is designed to eliminate the specific harmonic, which results in the vehicle  30  being significantly quieter. Another embodiment of the power supply  64  is illustrated in  FIG. 4B . The power supply  64  comprises a fuel cell  76  that powers the electric drive motors  56 ,  58  and the electric tool motor  60 .  
      With reference to  FIG. 5 , a schematic flowchart representing the unmanned utility vehicle  30  is shown. The electric lift motor  52 , the electric drive motors  56 ,  58 , and the tool motor  60  are brushless electric motors. Brushless electric motors are typically high endurance and have long run times without requiring maintenance. For example, brushless motors have an operating life of approximately 5,000 to 10,000 hours whereas the brush-type motors have an operating life of about 1,000 to 1,500 hours. Another advantage of the subject invention is that the vehicle  30  is free of belts and hydraulic units for operating such vehicles  30 . The belts are replaced by the electric tool motor  60  and the electric drive motors  56 ,  58  and the hydraulic unit is replaced by the lift motors  52 . The brushless motors  52 ,  56 ,  58 ,  60  are also about 30% lighter than the brush-type motors. This is advantageous because the vehicle  30  is lightweight and will not compact the grass that results in a better cut.  
      Each of the above motors  52 ,  56 ,  58 ,  60  also includes a motor controller operatively connected thereto. For example, a lift motor controller  78  is operatively connected to the lift motor  52 , a first drive motor controller  80  is operatively connected to the first electric drive motor  56 , a second drive motor controller  82  is operatively connected to the second electric drive motor  58 , and a tool motor controller  84  is operatively connected to the electric tool motor  60 . As one example, the controllers may include printed circuit boards having the necessary components to receive signals from the main controller  54  through the wiring harness  62  and then interpret the signal from the main controller  54  and generate and transmit a signal to operate the respective motor.  
      The main controller  54  communicates with the lift motor controller  78 , the drive motor controllers  80 ,  82  and the tool motor controller  84  to control the lift, electric drive, and tool motors. Further, each controller may include a unique identifier to identify the controller and motor to the main controller  54 . A controller area network  86 , commonly referred to as CAN BUS, interconnects the main controller  54 , the drive motor controllers  80 ,  82 , and the tool motor controller  84  for facilitating communication therebetween to improve operation of the vehicle  30 . The CAN BUS also communicates with a data collection system  88  for collecting various information relating to each of the motors  52 ,  56 ,  58 ,  60  and a user interfaces  90 . A chassis control  92 , including a global positioning system receiver, is also in communication with the CAN BUS. Multiple sonar sensors  94  are positioned about the carriage  32  and bumper sensors  96  communicates with the chassis control  92  and with the CAN BUS to provide safety.  
      In one embodiment, each of the motors  52 ,  56 ,  58 ,  60  may operate using sinusoidal control. To ensure accuracy of the vehicle  30 , at least the drive motors  56 ,  58  should operate using sinusoidal control. The sinusoidal control allows the main controller  54  to precisely control the operation of each of the motors  52 ,  56 ,  58 ,  60 . This is particularly advantageous because the movement of the vehicle  30  can be precisely controlled. Another advantage is that the tool motors  60  can be adjusted for varying types and thickness of grass. For example, if the grass is overly thick, then the main controller  54  may operate the tool  46  at a faster RPM, whereas if the grass is a very thin grass, then the tool  46  may operate at a slower speed. The main controller  54  is also able to detect when any one of the tool motors  60  fails. If the tool motor  60  fails, then the main controller  54  recalculates the cutting pattern for the specified area with the remaining tool motors  60 . In this manner, the vehicle  30  assembly is still able to complete the cut even if the tool motor  60  fails.  
      The user interface  90  may be used for programming a route to be followed by the vehicle  30  as best shown in  FIG. 23 . A remote control (not shown) may also be used to interface with the user interface  90 /main controller  54  to program the route into the vehicle  30 . The remote control may be a wired module, a wireless module, or both. The user interface  90  may mount into the rear of the cover  40  and may be removable therefrom. Alternatively, the user interface  90  may be permanently formed into the cover  40 . The user interface  90  and the main controller  54  may be formed as a single, integral unit removable from the carriage  32 . In this manner, the user interface  90  may be used on different vehicles  30 , if such vehicles  30  should become inoperable. If multiple vehicles  30  are owned and operated, then the user interface  90  for each one of the vehicles  30  may include relevant information and data about each of the other vehicles  30 . For example, the positioning data for achieving various cutting patterns may be stored on each one of the user interfaces  90 . If one of the interfaces fails, then any one of the other interfaces may be connected to the vehicles  30  to transfer the information respectively.  
      The vehicle  30  also includes a communication device  98  supported by the carriage  32  and in communication with the main controller  54  for wirelessly transmitting signals from the vehicle  30  to a base (not shown). The communication device  98  may be used to alert the operator of an error or problem with the vehicle  30 . One such communication device  98  is disclosed in copending U.S. patent application Ser. No. 10/179,558 titled “Automatic billing system for a lawn mowing service using GPS”, which is incorporated herein by reference.  
       FIG. 6  is a side view of a drive motor assembly  100 . The drive motor assembly  100  shown may be for either the first or second drive motors  56 ,  58 .  FIG. 7  is a cross-sectional view of the drive motor assembly  100  and  FIG. 8  is an exploded view of the drive motor assembly  100 . The drive motor assembly  100  includes a drive motor housing  102 , a reduction gear assembly  104 , and a wheel connector assembly  106 . Both of the first and second drive motors  56 ,  58  and the respective drive motor controllers  80 ,  82  are disposed in the respective drive motor housings  102 . The reduction gear assembly  104 , as understood by those of ordinary skill in the art, is used to reduce the relatively high RPM of the electric drive motor to a lower RPM suitable for the drive wheels  34 ,  36 .  
      The drive motor assemblies  100  are spaced from the main controller  54  such that the main controller  54  communicates with the drive motor controllers  80 ,  82  via the wiring harness  62 . The subject invention provides the vehicle  30  having each of the motors  52 ,  56 ,  58 ,  60  being modular such that if any one of the motors  52 ,  56 ,  58 ,  60  becomes inoperative, any other motor may be substituted in a different motor assembly. The motor controllers  78 ,  80 ,  82 ,  84  drive the motors  52 ,  56 ,  58 ,  60  thereby reducing any maintenance or repair time by being able to switch out one motor for another in a short period of time. Further, the subject invention does not require specialized motors.  
      For clarity, the following description is directed toward the first drive motor assembly and it is to be appreciated that the other drive motor assemblies  100  are substantially identical.  FIG. 9  is an exploded view of the first drive motor housing  102 . The first drive motor housing  102  includes the first drive motor  56 , the first drive motor controller  80 , and a drive sensor  108  disposed between the first drive motor  56  and the first drive motor controller  78 . The drive sensor  108  senses operation of the first drive motor  56  and is used to determine RPM of the first drive motor  56 . The drive sensor  108  may be a Hall effect sensor or an optical sensor. For example, the optical sensor emits a beam of light that is blocked by a rotating disc having an opening to allow the light to pass through. Every rotation of the disc is detected by a light detector detecting the light passing through the disc.  
       FIG. 10  is a cross-sectional view of the first drive motor  56  and  FIG. 11  is an exploded view of the first drive motor  56 . The first drive motor  56  includes a main motor housing  110 , a motor hub  112 , a rotor  114 , and a stator  116 . As discussed above, each of the motors  52 ,  56 ,  58 ,  60  are preferably brushless motors. The first drive motor controller  80  and drive sensor  108  are housed within the main motor housing  110 .  FIG. 12  is an exploded view of the wheel connector assembly  106 . The wheel connector assembly  106  includes another gear reduction assembly and a drive hub assembly  118 . The drive hub assembly  118  connects the drive wheel to the drive motor assembly  100 .  
       FIG. 13  is a side view of a tool assembly  120  and  FIG. 14  is a cross-sectional view of the tool assembly  120 . The tool assembly  120  includes a tool housing  122  and the tool  46  mounted thereto as shown in the exploded view of  FIG. 15 . An exploded view of the tool housing  122  is shown in  FIG. 16 . The tool housing  122  includes the tool motor  60 , the tool motor controller  84  disposed therein, and a tool sensor  124  disposed between the tool motor  60  and the tool motor controller  84 . The tool sensor  124  senses operation of the tool motor  60  and is used to determine RPM. The tool sensor  124  may be a Hall effect sensor or an optical sensor, as described above for drive motor assembly  100 . The subject invention senses tool, or blade, speed and, when it encounters tall grass, wet grass, or a heavy load, the main controller  54  slows the vehicle  30  down causing the tool motors  60  to operate at the peak of their efficiency curve. This also improves quality of cut because the cutting blades  50  are always cutting through the grass at the correct and optimum speed.  FIG. 17  is an exploded view of the tool motor  60  being an electric brushless motor and having the rotor  114  and the stator  116 . A tool connector  126  connects to the tool  46  to the tool motor  60 .  
      Referring to  FIG. 18 , a lift assembly  128  is shown and includes a lift motor housing  130  and a lift mechanism  132 . The lift mechanism  132  connects the tool  46  to the carriage  32  via a yoke linkage  134 . One embodiment of the lift mechanism  132  includes a worm gear assembly  136  shown in  FIG. 19 . As the lift motor  52  operates, the worm gear assembly  136  raises and lowers the tool  46 .  FIG. 20  is an exploded view of the lift motor housing  130  having the lift motor  52  and the lift motor controller  78  disposed therein.  
      The subject invention provides additional advantages such as the vehicle  30  is more energy efficient by a ratio of 3:1 because the vehicle  30  uses small, electric motors  52 ,  56 ,  58 ,  60  that use less power than a gas engine. For exanple, a 360-watt electric motor (Toro battery powered 18-inch mower) can produce the equivalent cutting power of a 5-Horsepower gas engine, or about 3,700 watts (there are about 740 watts per HP). Therefore, the electric motor is more efficient because gas engines that are used have considerably more power than what is actually required to cut grass. Still another advantage of electric motors  52 ,  56 ,  58 ,  60  is that they can temporarily exceed their rated capacity by drawing more current, whereas the gas engine is limited to its rated capacity. In fact, when the gas engine encounters a situation requiring more power than it can produce, it bogs down and becomes less powerful because it slides off its maximum point on the power curve.  
      While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In addition, the reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.