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Patent Title:Automated lawn mower or floor polisher Document Type and
Patent Pending: Harry Jacobson est., Bartsley, UK, under US Patent.
Title:Automated lawn mower or floor polisher Document Type and
Number:United States Patent 4887415 Link to this page:http://
www.freepatentsonline.com/4887415.html Abstract:An automated self
propelled lawn mower utilizes a pair of drive motors for independently
driving left and right hand drive wheels. Each drive motor is coupled
to the respective drive wheel by a double output gear reduction unit.
One side of the output shaft from each gear reduction unit is provided
with a rotary photo encoder for providing speed and position
information relating to each drive wheel. This information from each
rotary photo encoder is fed to a computer control via a computer
interface. Each independent wheel drive motor is computer controlled
through an interface and motor drive relays. An infrared obstacle
detector is mounted on each corner of the mower frame for detecting
obstructions. Grass touch detection switches on the rear of the mower
frame provide an indication of the relative position of the cut or
uncut grass which is fed through the computer via the interface
circuit for providing computer directional control to the independent
wheel drive motors which steer the mower along the proper track. A
separate blade drive motor is turned on or off by a photo switch which
detects uncut grass. The speed of the blade drive motor is controlled
by a manual switch. A floor polishing pad may be substituted for the
lawn mower blade to enable use of the device as an automated floor
polisher. Inventors:Martin, Robert L. (Belleville, IL, US)
Application Number:204886 Filing Date:06/10/1988 Publication Date:
12/19/1989 View Patent Images:Images are available in PDF form when
logged in. To view PDFs, Login or Create Account (Free!) Referenced
by:View patents that cite this patent Export Citation:Click for
automatic bibliography generation Primary Class:56/10.2R Other Classes:
56/DIG15, 180/401 Field of Search:56/10.2, DIG. 15 180/131, 140
250/202 US Patent References:3425197 Feb, 1969 Kita 56/10.
3550714 Dec, 1970 Bellinger 180/79.
3570227 Mar, 1971 Bellinger.
3650097 Mar, 1972 Nokes 56/10.
3924389 Dec, 1975 Kita 56/10.
4180964 Jan, 1980 Pansire 56/10.
4184559 Jan, 1980 Rass 180/131.
4347908 Sep, 1982 Anderson 180/131.
4528804 Jul, 1985 XXXXXXXX 56/10.
4573547 Mar, 1986 Yoshimura et al. 180/131.
4603753 Aug, 1986 Yoshimura et al. 180/131.
4777785 Oct, 1988 Rafaels 56/10.
Primary Examiner:Neuder, William P. Attorney, Agent or Firm:Kearns;
Jerry T. Claims:What is claimed as being new and desired to be
protected by Letters Patent of the U.S. is as follows:
1. A new and improved automated lawn mower, comprising:
a frame having top and bottom surfaces;
a pair of drive wheels mounted for rotation on opposite sides of said
frame, adjacent a front portion of said frame;
each of said wheels mounted for rotation with an axle;
each of said axles connected by a clutch to a gear reduction unit;
each of said gear reduction units having dual output shafts with one
output shaft connected to said clutch;
a second output shaft of each of said gear reduction units mounted by
a bearing block on said frame;
a rotary photo encoder on each of said second gear reduction output
shafts;
a wheel drive motor connected to an input shaft of each of said gear
reduction units;
a photo switch at a front edge of said frame for detecting uncut
grass;
a vertically extending shaft extending through a central portion of
said frame;
a variable speed blade drive motor on said upper frame surface
connected to said vertically extending shaft;
switch means for manually regulating the speed of said blade drive
motor;
a mower blade mounted for rotation with said vertically extending
shaft beneath said frame;
a castor wheel centrally mounted adjacent a rear side of said frame;
a touch grass sensor formed from three metallic strips mounted on a
rear side edge of said frame for detecting cut and uncut grass;
battery means operably connected for powering both of said wheel drive
motors and said blade drive motor;
an infrared obstacle detector mounted at each corner on the upper
surface of said frame;
control means operably connected for stopping said blade drive motor
in response to said photo switch; and
computer control means operably connected for independently
controlling each of said wheel drive motors in accordance with signals
received from said touch grass sensor, said rotary photo encoders and
said infrared obstacle detectors for steering said motor along a
boundary line between cut and uncut grass.
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Description:BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to automated lawn mowers, and more
particularly pertains to a new and improved automated lawn mower which
utilizes obstacle sensors and touch grass sensors to control the
direction of movement of a lawn mower through a computer interfaced
feedback control of independent wheel drive motors. The conventional
forms of automated lawn mowers heretofore devised require the setting
of a boundary track or indicator around the plot of land to be mowed.
Alternatively, the conventional forms of automated lawn mowers require
a detailed precise programmed map of the plot of land to be mowed to
enable the mower to follow a proper mowing course. In order to
overcome the disadvantages of providing a programmed lawn plot map or
constructing a boundary track indicator, the present invention
provides an automated self propelled lawn mower which utilizes
infrared obstacle detectors in conjunction with cut or uncut grass
sensors to provide feedback control to independent wheel drive motors
for steering the mower on a proper course.
2. Description of the Prior Art
Various types of automated lawn mowers are known in the prior art. A
typical example of such an automated lawn mower is to be found in U.S.
Pat. No. 3,550,714, which issued to S. Bellinger on Dec. 29, 1970.
This patent discloses an automated self propelled mower which operates
on the principle of random motion within a boundary. The boundary is
established by a signal carried on a conductor which must be installed
around the periphery of the plot of land to be mowed. The mower
includes a sensor for receiving the boundary signal as the mower
approaches the boundary and control circuitry for steering the mower
away from the boundary. U.S. Pat. No. 3,570,227, which issued to S.
Bellinger on Mar. 16, 1971, discloses a self propelled lawn mower for
cutting grass in a random and unattended manner. The mower is
propelled by a battery and comprises a frame supported on a pair of
front castor wheels and a pair of rear drive wheels. The drive wheels
are coupled to a continuously rotating drive shaft by individual
clutch brake mechanisms. When a boundary wire installed around the
perimeter of the plot of land to be mowed is sensed by coils on the
frame, the drive wheel farthest away from the boundary is unclutched
and braked to pivot or turn the mower. U.S. Pat. No. 3,650,097, which
issued to C. Nokes on Mar. 21, 1972, discloses a self propelled lawn
mower for movement over a given land area in a preplanned route. The
mower has a frame and a steering mechanism with a tape extending
between two reels with intermediate elements contacted sequentially by
the tape for providing a programmed tape mechanical control of the
course of the mower. U.S. Pat. No. 3,924,389, which issued to S. Kita
on Dec. 9, 1975, discloses a lawn mower which utilizes a sensor
mounted on the front of the mower to detect the edge of the swath by
sensing the difference in height between uncut and cut grass in the
swath. An electrical signal is produced by the sensors when it
contacts the uncut grass and passes therethrough a minute electrical
current. The current is amplified by a solid state amplifier circuit
and fed to a pair of clutch brake assemblies for steering the mower
along the edge of the swath. These clutch brake assemblies are
connected for selectively braking and or driving the wheels of the
mower. A sensor and control circuit design is disclosed for guiding
the mower along the swath edge with a minimum of hunting even with
grass is damp or growing sparsely. U.S. Pat. No. 4,184,559, which
issued to H. Rass on Jan. 22, 1980, discloses a lawn mower with a
mechanical sensor and piloting mechanisms which enable it to pilot
itself along the edge line between the grass already cut and grass not
yet cut, in a fairly straight course, and then to reverse its
direction at the end of a run, move itself sideways, towards the uncut
grass and proceed with another run. The lawn mower drive wheels are
driven by a planetary gear mechanism which is coupled both to the
motor and to rotatable sensor brushes mounted ahead of the drive
wheels so that the planetary mechanism transmits power to the drive
wheels only when the sensor brushes encounter resistance, such as from
uncut grass, ahead of the drive wheels. The planetary gear mechanism
is mounted on a guide frame that is pivotally mounted to the drive
wheel frame so as to engage a first of two counter rotating gears
linked on the wheel frame to the drive wheels. Forward impact against
the guide frame causes it to pivotally rock so as to engage the second
of the counter rotating gears to reverse direction of travel of the
lawn mower. U.S. Pat. No. 4,347,908, which issued to R. Anderson on
Sept. 7, 1982, discloses a self propelled lawn mower which is caused
to traverse a plot of land to be mowed by following a line arranged
over the land in a predetermined manner. A mechanical follower
mechanism is provided on the lawn mower for following the course line.
U.S. Pat. No. 4,528,804, which issued to T. XXXXXXXX on Jul. 16, 1985,
discloses a sensing unit for a row crop harvester guidance system
which comprises a rotatably mounted crop engaging arm biased into a
crop engaging position by a torsion spring. The spring tension is
adjustable to vary the amount of force required to actuate the crop
engaging arm. Variation of the force is desirable to permit the
sensing unit to operate reliably in a variety of crop and field
conditions. U.S. Pat. No. 4,603,753, which issued to S. Yoshimura et
al on Aug. 5, 1986, discloses an automated lawn mower which utilizes a
pair of spaced photo sensors for detecting the swath boundary between
cut and uncut grass. Control circuitry actuated by these photo sensors
operate electro-magnetic valves which operate hydraulic cylinders for
steering the front and rear wheels of the mower.
While the above mentioned devices are suited for their intended usage,
none of these devices provide an automated self propelled lawn mower
which utilizes independent feedback controlled drive motors for
independently driving the drive wheels of the lawn mower in accordance
with information provided by touch grass sensors and infrared
obstacles sensors. Inasmuch as the art is relatively crowded with
respect to these various types of automated lawn mowers, it can be
appreciated that there is a continuing need for and interest in
improvements to such automated lawn mowers, and in this respect, the
present invention addresses this need and interest.
SUMMARY OF THE INVENTION
In view of the foregoing disadvantages inherent in the known types of
automated lawn mowers now present in the prior art, the present
invention provides an improved automated lawn mower or floor polisher.
As such, the general purpose of the present invention, which will be
described subsequently in greater detail, is to provide a new and
improved automated lawn mower or floor polisher which has all the
advantages of the prior art automated lawn mowers and none of the
disadvantages.
To attain this, a representative embodiment of the concepts of the
present invention is illustrated in the drawings and makes use of a
pair of drive motors for independently driving left and right hand
drive wheels. Each drive motor is coupled to a respective drive wheel
by a double output gear reduction unit. One side of the output shaft
from each gear reduction unit is provided with a rotary photo encoder
for providing speed and position information relating to each drive
wheel. This information from each rotary photo encoder is fed to a
computer control via a computer interface. Each independent wheel
drive motor is computer controlled through an interface and motor
drive relays. An infrared obstacle detector is mounted on each corner
of the mower frame for detecting obstructions. Grass touch detection
switches on the rear of the mower frame provide an indication of the
relative position of the cut or uncut grass which is fed through the
computer via the interface circuit for providing computer directional
control to the independent wheel drive motors which steers the mower
along the proper track. A separate blade drive motor is turned on or
off by a photo switch which detects uncut grass. The speed of the
blade drive motor is controlled by a manual switch. A floor polishing
pad may be substituted for the lawn mower blade to enable use of the
device as an automated floor polisher.
There has thus been outlined, rather broadly, the more important
features of the invention in order that the detailed description
thereof that follows may be better understood, and in order that the
present contribution to the art may be better appreciated. There are,
of course, additional features of the invention that will be described
hereinafter and which will form the subject matter of the claims
appended hereto. In this respect, before explaining at least one
embodiment of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced and
carried out in various ways. Also, it is to be understood that the
phraseology and terminology employed herein are for the purpose of
description and should not be regarded as limiting. As such, those
skilled in the art will appreciate that the conception, upon which
this disclosure is based, may readily be utilized as a basis for the
designing of other structures, methods and systems for carrying out
the several purposes of the present invention. It is important,
therefore, that the claims be regarded as including such equivalent
constructions insofar as they do not depart from the spirit and scope
of the present invention.
Further, the purpose of the foregoing abstract is to enable the U.S.
Patent and Trademark Office and the public generally, and especially
the scientists, engineers and practitioners in the art who are not
familiar with patent or legal terms or phraseology, to determine
quickly from a cursory inspection the nature and essence of the
technical disclosure of the application. The abstract is neither
intended to define the invention of the application, which is measured
by the claims, nor is it intended to be limiting as to the scope of
the invention in any way.
It is therefore an object of the present invention to provide a new
and improved automated lawn mower or floor polisher which has all the
advantages of the prior art automated lawn mowers and none of the
disadvantages.
It is another object of the present invention to provide a new and
improved automated lawn mower or floor polisher which may be easily
and efficiently manufactured and marketed.
It is a further object of the present invention to provide a new and
improved automated lawn mower or floor polisher which is of a durable
and reliable construction.
An even further object of the present invention is to provide a new
and improved automated lawn mower or floor polisher which is
susceptible of a low cost of manufacture with regard to both materials
and labor, and which accordingly is then susceptible of low prices of
sale to the consuming public, thereby making such automated lawn
mowers economically available to the buying public.
Still yet another object of the present invention is to provide a new
and improved automated lawn mower or floor polisher which provides in
the apparatuses and methods of the prior art some of the advantages
thereof, while simultaneously overcoming some of the disadvantages
normally associated therewith.
Still another object of the present invention is to provide a new and
improved automated lawn mower or floor polisher which utilizes a pair
of drive wheels which are independently driven by feedback controlled
wheel drive motors in response to information obtained from touch
grass sensors and infrared obstacle detectors.
Yet another object of the present invention is to provide a new and
improved automated lawn mower or floor polisher which utilizes a pair
of drive wheels, each coupled to an independent drive motor by a
double output gear reduction unit having a rotary photo encoder for
indicating the speed and position of each drive wheel.
Even still another object of the present invention is to provide a new
and improved automated lawn mower or floor polisher which provides
touch grass detectors for determining the boundary between cut and
uncut grass and utilizes infrared detectors for avoiding obstacles.
These together with other objects of the invention, along with the
various features of novelty which characterize the invention, are
pointed out with particularity in the claims annexed to and forming a
part of this disclosure. For a better understanding of the invention,
its operating advantages and the specific objects attained by its
uses, reference should be made to the accompanying drawings and
descriptive matter in which there are illustrated preferred
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and objects other than those
set forth above will become apparent when consideration is given to
the following detailed description thereof. Such description makes
reference to the annexed drawings wherein:
FIG. 1 is a top view of the automated lawn mower of the present
invention.
FIG. 2 is a bottom view of the automated lawn mower of the present
invention.
FIG. 3 is a side view of the automated lawn mower of the present
invention.
FIG. 4 is a schematic diagram illustrating a photo switch control
circuit for activating or deactivating the blade drive control motor
of the lawn mower of the present invention.
FIG. 5 is a diagrammatic illustration of the manner of operation of
the photo switch blade control of the present invention.
FIG. 6 is another diagrammatic illustration of the manner of operation
of the blade control photo switch of the lawn mower of the present
invention.
FIG. 7 is a schematic diagram illustrating the touch grass sensor
switch of the automated lawn mower of the present invention.
FIG. 8 is a schematic diagram further illustrating the touch grass
sensor switch of the automated lawn mower of the present invention.
FIG. 9 is a perspective view of a portion of the lawn mower frame,
illustrating the mechanical assembly of the touch grass sensors of the
automated lawn mower of the present invention.
FIG. 10 a front view of the touch grass sensors of FIG. 9.
FIG. 11 is a cross sectional view, taken along line 11--11 of FIG. 10,
illustrating the touch grass sensors.
FIG. 12 is a schematic diagram illustrating the drive wheel motor
relay control circuits of the automated lawn mower of the present
invention.
FIG. 13 is a block diagram illustrating the control circuits of the
automated lawn mower of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference now to the drawings, and in particular to FIG. 1
thereof, a new and improved automated lawn mower or floor polisher
embodying the principles and concepts of the present invention and
generally designated by the reference numeral 10 will be described.
More specifically, it will be noted that the first embodiment 10 of
the invention includes a generally rectangular frame base plate 12. A
pair of ten inch diameter drive wheels 14 and 16 are mounted for
rotation on opposite sides at a front portion of the frame 12. The
drive wheels 14 and 16 are driven independently by wheel drive motors
18 and 20. The wheel drive motors 18 and 20 are variable speed DC
motors; Dodge Omni radiator fan motors were utilized in the
construction of a prototype. The drive wheels 14 and 16 are mounted
for rotation with axles connected by clutches 22 and 24 to gear
reduction units 26 and 28. The clutches 22 and 24 may be manually
actuated shaft couplings. A 5/8 inch to 1/2 inch Black and Decker
arbor was utilized in the construction of the prototype. The purpose
of the clutches 22 and 24 is to enable the drive wheels 14 and 16 to
be disconnected from the motors 18 and 20 to allow the mower to be
operated by manual pushing. Various other conventional forms of
manually actuated or electrically actuated clutches may be utilized
without departing from the scope of the present invention. The gear
reduction units 26 and 28 are Boston double output series 300, model
number 310-50-H1 having a fifty to one gear reduction ratio. The
second output shaft of each of the gear reduction units 26 and 28 is
journalled for rotation in axle bearing blocks 30 and 32. A pair of
rotary photo encoders 27 and 29 are provided on these output shafts
for providing speed and position indications of the drive wheels 14
and 16 to a computer control unit. The rotary photo encoders 27 and 29
are of the type utilizing an infra red LED disposed in spaced relation
to an FPT100 photo transistor. A circular disc is connected for
rotation between the stationary LED and photo transistor, with the
secondary output shaft of each of the gear reduction units 26 and 28.
A circular array of spaced holes are formed in the disc, for allowing
light to be transmitted from the LED to the photo transistor. This
provides a series of pulses at a frequency dependent upon the speed of
rotation of the drive wheels 14 and 16. The number of pulses may be
counted by a computer control unit to provide an indication of the
position of each drive wheel 14 and 16. A drive shaft extends
vertically through a central portion of the frame 12 and is driven
directly by a blade drive motor 48. A Dodge Omni radiator fan motor
was utilized as the blade drive motor in the construction of a
prototype. A manually actuated variable resistance switch 52 regulates
the voltage supplied to the blade drive motor 48, thus providing a
variable speed control. A pair of twelve volt batteries 44 and 46 are
mounted on the upper surface of the frame 12. One of these batteries
44 is utilized to power the blade drive motor 48 and the other 46 is
utilized to power the wheel drive motors 18 and 20. Four infrared
obstacle detectors 64, 65, 66 and 67 are mounted at the corners of the
upper surface of the frame 12. These infrared obstacle sensors may be
of the type available from Mark V electronics (Mark V Electronics,
Inc. 8019 E. Slauson Avenue Montebello, CA 90640 http://www.markvelectronics.comTel:
800-423-FIVE (orders outside Canada) 800-521-MARK (orders in Canada)
213-888-8988 (catalog/info) Fax: 213-888-6868 ) designated as TY-401
MK III. They have a set range of one foot and each is tuned to a
different lock frequency to prevent internal or external interference.
A collimated LED source 38 is mounted on the front portion of the
frame 12. The collimated LED source 38 cooperates with a photo switch
mounted on the bottom of a computer interface housing 34. This photo
switch serves to detect uncut grass at the front edge of the frame 12.
If no uncut grass is detected, the battery 44 is disconnected from the
blade drive motor 48. A touch grass sensor unit 68 is mounted adjacent
the rear edge of the frame 12 for detecting the boundary between cut
and uncut grass. These signals are fed to a computer control unit
which controls the wheel drive motors 18 and 20 to steer the mower 10
on the proper course. A castor mount plate 50 extends from a central
portion of the rear edge of the frame 12. A rear castor wheel extends
downwardly from the castor mount plate 50 to support the rear portion
of the mower 10. The castor mount plate 50 also provides a mounting
surface for the blade motor speed control switch 52. The axle bearing
blocks 30 and 32 also provide upstanding vertical supports for
mounting a computer control unit. Additional upstanding vertical
supports 40 and 42 are provided adjacent the rear edge of the frame
12. The interface 34 provides a five volt regulated power supply for
the infrared detectors 64, 65, 66, 67, the rotary photo encoders 27,
29, the collimated LED source 38 and the associated photo switch.
In FIG. 2, a bottom view of the mower is provided. A rubber skirt 58
extends downwardly from the bottom peripheral edge of the frame 12 and
serves to prevent rocks, grass, and other debris from being hurled
outwardly by the mower blade 54. A castor 56 is mounted on the bottom
surface of the castor mount plate 50. A photo switch 35, mounted on
the bottom surface of the interface 34, cooperates with the collimated
LED source 38 at the front edge of the mower 12 to provide an
indication of cut or uncut grass.
In FIG. 3, a side view of the mower is provided. A mounting plate 60
is supported by the upstanding vertical supports 30, 32, 40 and 42.
This mounting plate 60 serves to support a computer control unit 62.
The computer control unit 62 may be a Radio Shack model 100. The
computer interface 34 may be an Alpha products model AR135 A-bus which
includes an MB-120 motherboard and an IN-141 digital input card. The
castor 56 is mounted to the castor mounting plate 50 by a yoke 5.
FIG. 4 provides a schematic diagram of the grass detection photo
switch 35. Light from the collimated LED source 38, when not
obstructed by uncut grass, acuates the photo transistor T1 which
energizes the diode D1. The diode D1 is a GaAs LED infrared emitter
which dissipates 150 mW of power. The diode D1 has a peak forward
current of 3.0 A during a 300 usec pulse and a continuous forward
current of 80 mA. The diode D1 is optically coupled inside a light
sealed DIP 4N33 package to an NPN Photo Darlington transistor T2. The
transistor T2 is connected to an ECG251 switching transistor T3 which
disconnects the ground lead of the blade drive motor 48 when
energized, thus stopping blade rotation. The positive terminal of the
blade drive motor 48 is connected by the variable resistor dimmer
switch 52 to the battery 44. This enables the speed of the motor 48 to
be manually adjusted in accordance with the grass density.
FIG. 5 provides a diagrammatic illustration of the operation of the
photo grass detector. In the absence of uncut grass, light from the
collimated LED source 38, which utilizes a single heterojunction GaAs
Laser Diode 39 collimated by a reverse focused 20 mm wide angle
projection lens 41, enters the photo switch housing 35 through a small
aperture 37, striking the photo transistor T1 (FIG. 4).
FIG. 6 provides an isometric view illustrating the operation of the
LED source 38 and photo switch 35.
FIG. 7 is a schematic diagram illustrating the construction of the
grass touch sensor control circuit 68. Current conducted through moist
grass between metallic conducting grass contact strips 69 and 70 is
fed via the IClA section of a dual LF353 JFET operational amplifier 73
to a TY-38 switch 72. The switch 72 contains an amplifier and a
normally closed relay. The output of the switch 72 is connected to an
input port of the interface 34.
As shown in FIG. 8, the second IClA stage 73' of the dual LF353 JFET
operational amplifier is connected to another metallic grass
conducting strip 71.
With reference now to FIGS. 9-11, the operation of the grass touch
switch 68 will now be described. Three metallic strips 69, 70 and 71
are secured to the rear edge of the frame plate 12. Each of the strips
69, 70 and 71 has a central slot for the reception of a screw utilized
to attach the strips to the frame 12. The strips 69, 70 and 71 are
electrically insulated from the frame 12 and from each other. The back
surface of each strip which faces the edge of the frame 12 is provided
with a non-stick paint finish to guard against false inputs by grass
sticking to the strips. Strip 70 is a common ground and strips 69 and
71 are connected to separate inputs 73 and 73' of the operational
amplifier. When the mower is on the proper course, the longer strips
69 and 70 are in contact with grass that is already cut (shorter
grass), and the shorter strip 71 is in contact with uncut grass
(longer grass). Thus, current is conducted through the moist grass to
both inputs 73 and 73' of the grass touch switch control 68. When
strip 69 is nonconducting (out of contact with grass), the mower will
be steered alternately from left to right and right to left by
computer control of the wheel drive motors 18 and 20. When strip 71 is
nonconducting (over already cut grass), the mower will be steered to
the right.
In FIG. 12, a schematic diagram illustrating the contents of the relay
box 36 is provided. Inputs 1 and 2 are connected to output terminals
of the interface 34. R8 is a self-variable nichrome resistor which
serves as a ballast to prevent surge and transient high current damage
to the power transistors T8, T9, T10, T11, caused by sudden high loads
on the drive wheels 14 and 16. D6 and D7 are snap back diodes which
prevent back EMF damage to the transistors. The two pairs of power
transistors T8, T9 and T10, T11 and their corresponding opto-isolators
T4, T5 and T6, T7 are wired in an "or" configuration to provide power
boosting and signal feedback removal. Wheel drive motors 18 and 20 are
independently actuated by two ten ampere contact double pole relays
74, 75. These relays 74, 75 may be of the type sold by Radio Shack as
model number 275-218. Relays 74, 75 are independently actuated by
control signals from the computer 62 through interface 34 to control
the operation of the wheel drive motors 18 and 20. This independent
control enables precise steering control of the mower by drive wheels
14, 16.
The following table lists the values of the various resistors, diodes
and transistors of the schematic diagrams of FIGS. 4,7,8 and 12.
__________________________________________________________________________
RESISTOR
VALUE (ohms)
DIODE
TYPE
TRANSISTOR
TYPE
__________________________________________________________________________
R1 56K D1 LED T1 FT100 Photo
R2 10K D2 LED T2 4N33
R3 10K D3 LED T3 ECG251
R4 1K D4 LED T4 4N33
R5 47K D5 LED T5 4N33
R6 47K D6 1N4001
T6 4N33
R7 100 D7 1N4001
T7 4N33
R8 2 ohms nichrome T8 TIL101
self-variable T9 TIL101
T10 TIL101
T11 TIL101
__________________________________________________________________________
In FIG. 13, a block diagram illustrates the control circuitry of the
automated lawn mower of the present invention. The signals from the
infrared obstacle sensors 64, 65, 66, and 67 are fed to the computer
62 through the interface 34. The touch grass sensor 68 detects the
boundary between the cut and uncut grass and feeds these signals
through the interface 34 to the computer 62. The computer 62
determines the steering signals to be fed to the wheel drive motors 18
and 20 through the motor drive relay 36. The motor drive relay 36
independently energizes the wheel drive motors 18 and 20 to steer the
mower on the proper course. The speed and position of each drive wheel
is determined by rotary photo encoders 27 and 29 and fed to the
computer 62 through the interface 34. Thus, the wheel drive motors 18
and 20 are controlled by two separate feedback control loops. The
photo grass sensor 35 at the front of the lawn mower determines
whether the mower is approaching cut or uncut grass. If the sensor 35
does not detect uncut grass, the blade drive motor 48 is switched
off.
While the invention has been described with reference to lawn mowing
operations, by substituting a floor polishing pad for the blade 54,
the device of the present invention may be utilized as an automated
floor polisher. In this mode of operation, the touch grass sensors 68
and the photo grass sensor 35 are deactivated, and the steering is
controlled by the infrared obstacle sensors 64, 65, 66 and 67.
With respect to the above description then, it is to be realized that
the optimum dimensional relationships for the parts of the invention,
to include variations in size, materials, shape, form, function and
manner of operation, assembly and use, are deemed readily apparent and
obvious to one skilled in the art, and all equivalent relationships to
those illustrated in the drawings and described in the specification
are intended to be encompassed by the present invention.
Therefore, the foregoing is considered as illustrative only of the
principles of the invention. Further, since numerous modifications and
changes will readily occur to those skilled in the art, it is not
desired to limit the invention to the exact construction and operation
shown and described, and accordingly, all suitable modifications and
equivalents may be resorted to, falling within the scope of the
invention.
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