Abstract:
A kit and method converts a conventional gasoline-fueled walk-behind lawnmower to a robotic lawnmower. The existing transmission is replaced with a motorized front wheel drive transmission which can engage and disengage the front wheels independently of each other, thereby steering the vehicle. An electronic control system controls the starter switch, the engine throttle, and the transmission and steering of the vehicle. A navigational system is included which continuously communicates position and direction of travel to the electronic control system. A variety of sensors detect operating conditions, hazards and obstacles in the vehicle&#39;s path which data are also communicated to the control system. A microprocessor in the control system stores these data in a programmable memory as a map of the area to be mowed. During a learning mode, the user utilizes a control panel in operative communication with the electronic control system to control and guide the vehicle along the desired path and create the map. During operating mode, the microprocessor accesses the map and commands the electronic control system to maneuver the vehicle in accordance with the map. The control panel displays the operating status of the vehicle at all times when the vehicle is turned on.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to autonomous “robotic” lawnmowers capable of cutting a predetermined grass area without human intervention, and more particularly a kit and method for converting a conventional walk-behind gasoline-powered mower to a robotic mower.  
         BACKGROUND OF THE INVENTION  
         [0002]    A number of autonomous vehicle inventions are known in the prior art. U.S. Pat. No. 4,600,999 to Ito et al. teaches an autonomous vehicle having a device for defining the outer periphery of a work site and automatically deducing a running course covering the interior of the work site. U.S. Pat. No. 5,925,080 to Shimbara et al. is for an automatic guided vehicle which travels a path established by a path guide laid on the surface to be traveled. U.S. Pat. No. 6,112,143 to Allen et al. is for an automatically controlled vehicle which involves activating a learning mode, positioning the mower at a plurality of locations on a perimeter and recording positioning data at each location. The position data is stored in a data processor which generates a display of th perimeter. U.S. Pat. No. 4,700,301 to Dyke discloses a method for automatically steering a motor vehicle on a programmed course by continuously measuring angles between reference points, suing a microprocessor to calculate the vehicle position and direction of motion.  
           [0003]    Pong et al., U.S. Pat. No. 4,962,453, discloses a vehicle using information derived from contact between bumpers and objects in the environment to sense the geometry of the environment, the data then being used to generate an algorithm to cover the area. U.S. Pat. No. 5,204,814 to Noonan et al., uses an electronically stored path and terrain information as a primary navigation system, and metallic guide path for a secondary navigation system. It incorporates an ultra sonic obstacle detection system for stopping the vehicle if unexpected obstacles are encountered. Diekhans, U.S. Pat. No. 6,101,795, is for an automatic steering mechanism for a self-propelled machine which scans a crop edge, such as the border between mowed and unmowed crops, to produce signals for the steering mechanism. Nelson, U.S. Pat. No. 5,974,347, utilizes a rotating directional loop antenna to determine position within a cutting area by measuring the angle between transmitters placed in a known configuration outside of the cutting area, and then stores the path information. The Angott et al. U.S. Pat. No. 6,009,358, is for a mower controlled y a central processing unit to follow a predetermined route, using first and second locating transmitters to determine the route. No. 5,163,273 to Wojtkowski et al., is for a mower that follows a buried wire.  
           [0004]    These patents illustrate that the overall concept of an automatically controlled lawn mower which has a learning mode to determine cutting area and which stores the path information in a database is well-known in the prior art. None of these patents, however, teaches the conversion of a mass-marketed gasoline-engine walk-behind mower to robotic mower. In fact the robotic mowers that are currently available to the consuming public are electrically powered by batteries, are very time-consuming to set up and train, slow to perform the mowing task, need recharging often, and need frequent battery replacement. Accordingly an object of this invention is to provide a means and method whereby the average homeowner, or manufacture of conventional mowers, can convert his existing walk-behind gasoline-fueled lawnmower to a robotic mower. It is another object of this invention to provide a gasoline-fueled robotic mower which is consequently faster to “train” and faster in accomplishing the mowing task than the electric models now available. Yet another object of the invention is to utilize a dual navigational system of global positioning and dead reckoning to ensure constant monitoring of the mower&#39;s position, thus a high degree of accuracy in accomplishing the mowing task. Still another object of this invention is to provide an autonomous vehicle with a highly maneuverable drive system.  
         SUMMARY OF THE INVENTION  
         [0005]    The foregoing objects of the invention are achieved by providing a kit and method for converting a conventional gasoline-fueled walk-behind lawnmower to a robotic lawnmower. The existing transmission is replaced with a motorized front wheel drive transmission which can engage and disengage the front wheels independently of each other, thereby steering the vehicle. An electronic control system is provided which controls the starter switch, the engine throttle, and the transmission and steering of the vehicle. A navigational system is included which continuously communicates position and direction of travel to the electronic control system. A variety of sensors detect operating conditions, hazards and obstacles in the vehicle&#39;s path which data are also communicated to the control system. A microprocessor in the control system stores these data in a programmable memory as a map of the area to be mowed. During a learning mode, the user utilizes a control panel in operative communication with the electronic control system to control and guide the vehicle along the desired path and create the map. During operating mode, the microprocessor accesses the map and commands the electronic control system to maneuver the vehicle in accordance with the map. The control panel displays the operating status of the vehicle at all times when the vehicle is turned on. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1. is a side elevational view of a conventional, gasoline-powered, walk-behind lawnmower without the kit of this invention.  
         [0007]    [0007]FIG. 2 is top plan view of the mower of FIG. 1  
         [0008]    [0008]FIG. 3 is a side elevational view of the mower of FIGS. 1 and 2 converted to a robotic mower by the kit of this invention.  
         [0009]    [0009]FIG. 4 is a top plan view of the robotic mower of FIG. 3  
         [0010]    [0010]FIG. 5 is a perspective view of the mower of FIGS. 3 and 4.  
         [0011]    [0011]FIG. 6 is a system data-flow diagram of the invention  
         [0012]    [0012]FIG. 7 is a top plan view of the detachable operator panel of this invention  
         [0013]    [0013]FIG. 8 is a side elevational view of the panel of FIG. 7  
         [0014]    [0014]FIG. 9 is a perspective view of the drive transmission of this invention  
         [0015]    [0015]FIG. 10 is a top plan view of the drive transmission of FIG. 9.  
         [0016]    [0016]FIG. 11 is a front elevational view of the drive transmission of FIGS. 9 and 10.  
         [0017]    [0017]FIG. 12 is a block diagram of the mechanical system of this invention.  
         [0018]    [0018]FIG. 13 is a block diagram of the power distribution system of this invention.  
         [0019]    [0019]FIG. 14 is a block diagram of the data connections system of this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    A typical gasoline-powered walk-behind lawnmower, suitable for conversion to a robotic mower using the kit of this invention, is represented in FIGS. 1 and 2. One such mower available on the market is the Sears Model 37720. It has a 6¾ horsepower gasoline engine  40 , an electric starter  41 , 12-volt battery  11 , and front wheel drive  42 . To install the elements of the kit of this invention, the rear handle  44  with throttle control cable  43  and starter switch  41 , the handle&#39;s mounting brackets  47 , front wheels  45 , transmission  42 , and rear wheels  46  are removed and saved. The engage lever  48  and transmission control cable  49  are removed and replaced with various electrical, mechanical, and electronic elements of this invention, to be described later.  
         [0021]    [0021]FIGS. 3, 4 and  5  show wheels  45  and  46  re-installed with the kit&#39;s mechanical components, which provide the means to attach an electronic control system board  21 , a detachable operator panel  10 , and the mounting of a replacement transmission  29 . The transmission components comprise two major assemblies. The first assembly is a heavy-duty aluminum mounting bracket  60  located between the lawnmower handle mounting brackets  47 . It is installed on the lawnmower by using existing holes used for the old rear wheel brackets, in the deck plate. Drilling holes in the lawnmower will not be required for mounting this assembly. Bracket  60  extends the rear wheels  46  back about 10 inches and allows each wheel  46  to rotate through 360 degrees. Access to the battery  11 , gas, oil, and blade for maintenance is still available. The electronic control system board  21  is attached directly to the mounting bracket  47  cross member shelf. The detachable operator panel  10  is clip-mounted directly on top of the electronic control system board  21 . A removable tow handle  61  can be mounted on the rear of the mounting bracket  47  cross member shelf. The removable tow handle  61  is used to transport the lawnmower from its storage area to the starting position in the landscape to be cut. This assembly is pre-assembled with the electronic control system board  21 , the detachable operator panel  10 , removable tow handle  61 , and four cables to cable control motors  18 ,  19 ,  20  and  33  involving gear selection, steering, and throttle control, which will be more fully described later. To install the mechanical components, first this pre-assembled first assembly is bolted on the lawnmower. Next, cables to the four control motors  18 ,  19 ,  20  and  33  and electrical power cables  51 , from the battery to the electronic control system board  21 , and  52 , from the control board  21  to the electric starter  28 , are connected. Lastly, the rear wheels  46  are reinstalled.  
         [0022]    The second major assembly of mechanical components provides the steering action of the lawnmower. This is accomplished with a replacement transmission  29 , shown in FIGS. 4, 9,  10   11  and  12 , which selects forward, neutral or reverse gears, and engages or disengages each wheel separately or together. Control motor  18  moves gear selector  30  among the three gears. Control motor  19  moves the engage/disengage lever  31  for the left front wheel  45 , and control motor  20  moves the engage/disengage lever  32  for the right front wheel  45 . The method of steering involving engaging either or both front wheels to the drive shaft is virtually the same as that of the lawnmower prior to conversion. Cable control motor  33  operates the engine throttle  43 .  
         [0023]    Sensory features shown in FIG. 4 include four bumper tactile sensors  13  and three object sensors  14  disposed on each side and at the front and rear of the mower. Bumper tactile sensors  13  sensors are micro switches based with ‘probes’ that extend out beyond the deck housing of the lawnmower. These positioned about four inches off the ground. Hitting a low-level object activates the bumper bumble sensors  13 . The object sensors  14  are optic type sensors mounted on the lawnmower twelve inches off the ground, with a detection range of four feet. These sensors  14  are activated when an undefined object is detected in its field of view. A wet grass sensor  15  is mounted in the front section of the lawnmower housing deck, extending down to blade level. This sensor  15  is activated during wet grass conditions.  
         [0024]    A major sensory feature of the invention is the navigational system which determines the location of the robotic mower. In the preferred embodiment, the invention has two navigation systems, to provide an accurate position of the self-propelled walk behind lawnmower while in operation. The first one is a differential global positioning system (DGPS)  23 , and the second one is a dead reckoning system (DRS)  24 . Both navigation systems  23  and  24  are located in the electronic control system board  21 , as shown in FIG. 6, the system data flow block diagram. When a signal from DGPS  23  signal is not available, DRS  24  is used until the DGPS  23  signal becomes available. At least one of the navigation positioning systems,  23  or  24  must be available at all times. DGPS  23  could be a commercial chip set type or GPS module for mobile products such as the M-Loc™ MPM™ module manufactured by Trimble Navigation LtdA minimum of four tracking satellites are required for the desired DGPS  23  position accuracy, which should be measured in inches. DRS  24  is a system using a compass to determine heading and a real time clock chip in combination with wheel-revolution counters  16  to measure distance traveled by the lawnmower. It should have a position accuracy that is measured in inches. Preferably the compass is a commercial model which contains ‘roll’ and ‘pitch’ functions that serve as a tilt/dropoff sensor  50 , indicated in FIG. 5. This sensor  50  is activated when either ‘roll’ or ‘pitch’ values exceed five degrees. The dual navigation position systems  23  and  24  provide lawnmower position, roll, pitch, heading, GPS coordinates data, and real time in both the ‘run’ and ‘learn’ modes.  
         [0025]    Other sensors indicated in FIG. 6 include a balance/vibration sensor  26  mounted inside the electronic control system board  21 . This sensor  26  is activated if the lawnmower has excessive vertical and or horizontal movement. Examples would be a broken blade or continuous ramming of an object if a bumper tactile sensor  13  failed. A battery low voltage sensor  25  prevents operating the lawnmower when the battery  11  voltage is too low to reliably operate the cable control motors  18 ,  19 ,  20 ,  33  and sensors  13 - 17 ,  25 , and  26 .  
         [0026]    The electronic control system  21  receives power from the lawnmower battery  11  and information as to its location from navigation systems  23  and/or  24 . The electronic control system board  21  has a micro controller processor  22  which receives data from the navigational systems  23  and  24 , and sensors  13 - 17 ,  25 , and  26 . These data are acquired in both ‘learn’ and ‘run’ modes. The processor  22  receives instructions from the detachable operator panel  10  during its ‘learn’ mode and stores them in the programmable memory card  27  as a map of the landscape area to be mowed. Memory card  27  could have as an option enough storage area to store two maps for two separate landscapes, as well as the data necessary to handle two full tanks of gasoline. During the ‘run’ mode, wherein the lawnmower is robotic, the mower receives instructions from processor  22  according to the map stored in the memory card (database)  27 . Processor  22  controls the movements of the mower in its ‘run’ mode by means of transmission cable control motors  18 ,  19 , and  20 , which connect the electronic control system  21  to the replacement transmission  29  of this invention. Cable control motor  33  connects the processor  22  to the engine throttle  43  This allows the controller processor  22  to shut off the fuel to the gas engine  40 , thus stopping the lawnmower.  
         [0027]    Processor  22  informs status displays  80 - 85 , located on the detachable operator panel  10  represented in FIG. 7, whether or not sensors and systems are operating properly.  
         [0028]    A more detailed description of the operator panel  10  follows later herein. Processor  22  also controls the mower electric starter  28 .  
         [0029]    [0029]FIGS. 7 and 8 depict the detachable operator panel  10 . Panel  10  displays the current status of the lawnmower operating conditions, and manually controls the lawnmower during the mapping of a landscape area. The detachable operator panel  10  receives its power from, and communicates with, the electronic control system board  21  via an electrical cable  54 . Panel  10  allows the user to walk beside the lawnmower, operating it without touching it, during the mapping of a landscape area. The detachable operator panel  10  and connecting cable  54  are attached to the electronic control board  21  during storage and when cutting the landscape area. The panel  10  should be watertight in all areas.  
         [0030]    The operating status is always displayed whether in the landscape mapping or grass cutting mode. As a minimum, the status is displayed using seven individual light emitting diodes (LEDs)  81 ,  82 ,  83 ,  84 ,  85 ,  86 , and  87  and ten LEDs arranged as a ten-segment bargraph  80 . The bargraph  80  is used to show the battery voltage level, from 20 to 0 volts DC, the number of navigation channels currently being used, from 10 plus to 0, free memory remaining in the memory card  27 , from 100 to 0 per cent, estimated time remaining based on fuel remaining, from 100 to 0 minutes, any faulted on board sensors  12 , from 10 to 0.  
         [0031]    Each of the bargraph  80  displays is shown for one second in continuous rotation. The five individual status LEDs next to the bargraph  80  LEDs to indicate when the battery voltage  81 , navigation channels  82 , free memory  83 , fuel remaining  84 , and faulted sensors  85  status is being shown. For unscheduled lawnmower stops, the bargraph  80  will freeze and hold the faulted sensor display  85 . The sixth individual LED  86  displays the status of optical object sensors  14 . It will come on when any of the four object sensors  14  are activated The seventh individual LED is the navigational marker  87 . It will flash each time when recording location data point from the dual navigation positioning system  23 ,  24  or when using a location data point from the database. It will remain on when not recording or reading the location data from the database.  
         [0032]    The detachable operator panel  10  has ten switches used for manual control of the lawnmower during the mapping of a landscape area when in the ‘Learn’ mode. Switch  70  is a keylock start switch. Turning the switch all the way over and releasing it to the run position will electrically start the lawnmower. The keys for the start switch, along with the memory card  27  make up the security system for the lawnmower. Both items are required to operate the lawnmower. Switch  71  is a push button. Pushing the switch down engages a ‘dead man’ feature, which allows the key start switch to work. Holding the switch allows the lawnmower engine  40  to run. Releasing this switch will stop the lawnmower engine  40  as per the ‘dead man’ feature. Switch  72  is a push button switch for selecting the forward drive direction. Releasing this switch will place the drive direction in neutral. Switch  73  is a push button switch for selecting the reverse drive direction. Releasing this switch will place the drive direction in neutral. Switch  74  is a push button switch for selecting the left turning drive direction. Releasing this switch will place the steering to the center direction. Switch  75  is a push button switch for selecting the right turning drive direction. Releasing this switch will place the steering to the center direction. To make a left forward turn, switch  72  (forward) must be pressed simultanously with switch  74  (left turn). Switch  74  is released to stop turning left. Switch  76  is a centered three-position toggle switch. One position starts recording the navigation locations, one position is off for no recording, and in the third position, recording is resumed if the current lawnmower navigation position has been previously recorded. The resume feature will also erase all navigation positions in the memory card (database)  27  later than the current navigation position. The resume feature allows the user to ‘back-up’ while mapping a target area, instead of starting over from the beginning. Switch  77  is a two-position toggle switch for placing the lawnmower in the ‘learn’ or ‘run’ modes of operation. When in the ‘learn’ mode, the detachable operator panel  10  can be detached from the electronic control system board  21 . When in the ‘run’ mode, the detachable operator panel  10  must be attached to the system board  21 . With its on board sensors  12  it becomes a ‘dead man’ feature. Switch  78  is a push button type switch, which is only active during the ‘learn’ mode, and when the object sensor LED  86  is on. If a stationary valid object (tree, rock, fence, etc.) is detected during the ‘learn’ mode, the user can press and hold the object override switch  78  until the object detect LED  86  goes out. This information will be recorded in the memory card (database)  27 , which will allow the lawnmower to continue cutting the grass in this area during the ‘run’ mode. Switch  79  is a two-position toggle switch for selecting the mapping or cutting of two separate landscapes, labeled as ‘Map  1 ’ and ‘Map  2 ’.  
         [0033]    All the detachable operator panel  10  components such as switches and displays are connected to a micro controller processor chip  55  located inside the detachable operator panel  10 . This micro controller processor chip  55  communicates with the micro controller processor  22  located in the electronic system board  21  via panel  10 . System board  21  and operator panel  10  must communicate once every second, otherwise the lawnmower engine  40  is shut down.  
         [0034]    As shown in FIG. 13, all sensors are connected to the micro controller processor  22  located in the electronic control member  21 . Activating any sensor will cause the micro controller processor  22  to update the LED ten-segment bargraph  80 , turn on the faulted display LED  81 ,  82 ,  83 ,  84 , or  85 , and shut off the gas engine  40 . Any activated sensor acts as a ‘dead man’ feature when the lawnmower is in the ‘run’ mode. The memory card  27  and the dual navigation positioning system  23  and  24 , not being in agreement, within tracking limits of the lawnmower current position, cause Navigation Error, displayed by the bar graph  80 . The operator panel  17  sensor switch prevents operating the lawnmower in the ‘run’ mode with the detachable operator panel  10  detached. If the detachable operator panel  10  is detached during the ‘learn’ mode, it will cause the Operator Panel Error. The Dead Man function error is the failure of not holding the dead man switch  71 , on the detachable operator panel  10 , in the down position during the ‘Learn’ mode. Prior to using the lawnmower for the first time, the user must manually test the sensors  13 ,  14 ,  15 ,  26 , and  50 , as instructed in the user operator manual which is included in the kit. The processor  22  will record the results in the memory card  27 . The lawnmower will start only when the memory card  27  contains data that the sensors were satisfactorily tested.