U.S. patent application number 10/137858 was filed with the patent office on 2003-08-07 for systems and methods for radio control and operation of a miniature toy vehicle including interchangeable bodies.
This patent application is currently assigned to XXAP DESIGN, INC.. Invention is credited to Berkowitz, David, Clements, Ron, Montgomery, John, Scott, Ken.
Application Number | 20030148703 10/137858 |
Document ID | / |
Family ID | 27668067 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030148703 |
Kind Code |
A1 |
Scott, Ken ; et al. |
August 7, 2003 |
Systems and methods for radio control and operation of a miniature
toy vehicle including interchangeable bodies
Abstract
A radio control system for a single or multi-controller, single
or multi-receiver independently controlled system providing digital
and proportional control without mutual interference, especially
suited for a miniature toy vehicle. The controller may operate on
multiple frequencies (channels) selected by the user. The receivers
may receive on multiple frequencies (channels) selected by the
user. When the receiver is first turned on, it reads the channel
select switch and sets its receiver accordingly then normal remote
control signals may be received such as speed, steering and digital
commands. Commands are sent in bursts with an error checking
protocol implemented. Commands are not executed by the receiver
unless they are received error free. If the receiver fails to
receive error-free command bursts within a short period of time
(less than one second), it shuts off all motors and controls and go
into a dormant state awaiting an error-free command burst. If
error-free command bursts are not received within an extended
period of time such as two minutes, the receiver completely shuts
off thereby conserving battery power. The receiver includes a
long-life rechargeable battery system that lasts for the normal
lifetime of the car. The vehicle includes a simplified steering
system that provides full proportional control without requiring
position feedback.
Inventors: |
Scott, Ken; (Mountain View,
CA) ; Clements, Ron; (Los Altos, CA) ;
Berkowitz, David; (Arnold, CA) ; Montgomery,
John; (San Jose, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
XXAP DESIGN, INC.
Los Altos
CA
94022
|
Family ID: |
27668067 |
Appl. No.: |
10/137858 |
Filed: |
May 1, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60288684 |
May 3, 2001 |
|
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|
Current U.S.
Class: |
446/456 |
Current CPC
Class: |
A63H 30/04 20130101 |
Class at
Publication: |
446/456 |
International
Class: |
A63H 030/04 |
Claims
What is claimed is:
1. A radio control system comprising at least one control set to
transmit command signals for operation of a remotely controlled
device, the controlled device comprising a receiver to receive the
transmitted control signals and a decoder to decode the control
signals and act upon the control signals as required either
sequentially or concurrently.
2. A radio control system in accordance with claim 1 wherein the
radio control system comprises a plurality of controlled devices,
each controlled device being independently controlled by a
respective receiver such that the receivers do not interfere with
each other.
3. A radio control system in accordance with claim 1, wherein
command bursts are transmitted by the at least one control set
encoded such that the receiver may detect errors in the received
data burst and thereby reject erroneous data.
4. A radio control system in accordance with claim 2, wherein
command bursts are transmitted by the at least one control set
encoded such that the corresponding receiver may detect errors in
the received data burst and thereby reject erroneous data.
5. An apparatus for communicating between a plurality of
controllers and a plurality of receivers in a radio control system
wherein said plurality of receivers are independently controlled by
said plurality of controllers, respectively, said apparatus
comprising: means in each of said plurality of controllers for
generating a radio frequency signal; said controller including
means for a user to set the frequency of operation; said controller
including means of modulating the radio frequency signal; a
receiver in each of said plurality of receivers for receiving said
radio frequency signal; said receiver including means for
demodulating said radio frequency signal; and means of error
control to prevent erroneous response to noise or interference.
6. A radio control system in accordance with claim 1 wherein the
controlled devices comprise a toy vehicle.
7. A radio controlled toy vehicle comprising: at least one front
wheel; at least one rear wheel; a motor coupled to at least one of
the wheels; a receiver including a channel selecter; an antenna
coupled to the receiver; and a steering drive apparatus coupled to
the at least one front wheel, the steering drive apparatus
comprising a stepper motor.
8. A radio controlled vehicle in accordance with claim 7 further
comprising at least two bodies that may be individually coupled to
a chassis of the vehicle.
9. A radio controlled vehicle in accordance with claim 7 further
comprising dust cones coupled to each wheel.
10. A radio controlled vehicle in accordance with claim 7 wherein
the antenna comprises a substantially flat metallic strip.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 60/288,684 (Attorney Docket No. 020864-000300US)
filed May 3, 2001 which is herein incorporated by reference for all
purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a radio control system in
which a plurality of receivers are independently controlled by a
plurality of radio controllers without mutual interference, and a
toy vehicle including the same.
[0004] 2. Description of the Prior Art
[0005] Radio control systems are well known for many applications
including toys such as, for example, toy cars, toy boats and toy
airplanes. However, such systems are usually large, complex and
require the user to change components to set the operating
frequencies so that they do not mutually interfere with each
other.
[0006] Existing small products have tried to imitate typical/normal
use of a vehicle. They were only successful in providing part of
the experience but could not provide a completely self contained
and independently controlled vehicle. For example, there are
vehicles that receive their energy source from outside the vehicle,
or that can be steered by external sources such as slot cars.
[0007] There are existing remote control cars that have full
digital proportional control of both speed and steering giving
variable movement left/right and forward/reverse. They are
primarily meant for outdoor use as they are large and fast. They
generally do not work well in confined or limited spaces.
[0008] There are also a number of vehicles meant for use indoors.
They range from vehicles with limited control of two or three
functions, to vehicles with limited features. There is also a type
of miniature car for indoor use by racing on a track but it
contains only a motor. Previous inventions were unable to provide
the means to realistically control a vehicle. These cars run on a
track with a slot to control the steering and metal guides to
transfer power to the motor. There was also a wire to connect the
controller to the track or vehicle. In a racing environment,
current playsets allow only two slot cars running on a track with
each vehicle coupled to a groove and power strip in the track.
There is no means to operate the vehicles independently of the
groove in a track. Furthermore, alternative existing systems
designed for large vehicles, require use of matching crystal sets
to be plugged into the transmitter and receiver to allow more than
one to operate simultaneously in a given area.
[0009] Existing remote controlled vehicles which have internal
power sources have used non-rechargeable batteries that required
frequent replacement or rechargeable batteries that were large, had
a limited life span and required frequent recharging.
[0010] There is a very large installed base of miniature cars,
track and play sets. To increase the users enjoyment of these
accessories, there is a need for an indoor vehicle with variable
controls that can work on or independently of a track or a play
set. The problem that until now has not been overcome is to make a
vehicle for confined spaces that is completely controllable and can
be used independently or with any track, play set, or racing
environment.
[0011] Thus, a miniature vehicle with proportional control of the
steering and speed has not been successfully designed. Attempts
have been made over the years to design a controllable vehicle that
works with existing miniature vehicle play sets. A variety of
methods to accomplish parts of this have been developed and
include:
[0012] Make a slot in a track to control the steering and power the
motor through two external contacts;
[0013] Use a solenoid to force the steering left and right. This
provides only limited control since it is not proportional;
[0014] Install a capacitor to charge and provide power to a motor
to drive the wheels. This type does not allow proportional speed
and has no steering function;
[0015] Connect the car to a spring loaded or motor driven external
device that projects the car forward;
[0016] Use a spring to wind up and drive the rear wheels; and
[0017] Drive some of the vehicles on a track with vertical
sides.
SUMMARY OF THE INVENTION
[0018] It is an object of the present invention to provide a
control system for radio controlled devices which overcomes the
limitations of the prior art.
[0019] More specifically, it is an object of the present invention
to provide a control system for a radio controlled device that
permits the proportional and digital control of many functions for
a plurality of systems without mutual interference between
them.
[0020] Still another object of the present invention is to provide
a simplified method for the users to set up the system in a
multiple transmitter and receiver environment.
[0021] A still further object of the present invention is to enable
the receiving device to be miniaturized in both size and
weight.
[0022] According to an aspect of the present invention, there is
provided a radio control system of the type having a plurality of
receivers that are independently radio controlled by a plurality of
radio controllers comprising the ability in each controller to
repetitively generate command bursts.
[0023] According to a feature of the present invention, the command
burst sent by a controller is encoded in such a way as to contain
error control information without excessive overhead such that the
receiver may easily check the integrity of the received burst and
reject any bursts that are not entirely error free.
[0024] According to a further feature of the present invention, the
receiver shuts off any motors or other operations if it fails to
receive an error free command burst within a specific time
period.
[0025] According to a further feature of the present invention, the
controller normalizes the analog (proportional) control signals to
zero such that when the transmitter is first turned on, the analog
inputs such as, for example, steering or speed, that are assumed to
be in their zero position, are sent as a zero command.
[0026] According to yet a further feature of the present invention,
a radio controlled toy vehicle comprises at least one front wheel,
at least one rear wheel, a motor coupled to at least one of the
wheels, a receiver including a channel selecter, an antenna coupled
to the receiver and a steering drive apparatus coupled to the at
least one front wheel, the steering drive apparatus comprising a
stepper motor.
[0027] In accordance with another feature of the present invention,
the vehicle further comprises dust cones coupled to each wheel.
[0028] In accordance with yet another feature of the present
invention, the antenna comprises a substantially flat metallic
strip.
[0029] In accordance with another feature of the present invention,
a standard chassis of each vehicle type (including but not limited
to) such as Racer, Sedan, Sports car, SUV, Truck, Van, Tank, F1
etc. is utilized, and thus allows multiple styles of color,
appearance, versions, brands, banners on vehicle bodies to be
attached to the chassis.
[0030] The above, and other objects, features and advantages of the
present invention will become apparent from the following
description read in conjunction with the accompanying drawings in
which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic illustration of a radio controlled toy
automobile system in accordance with the present invention;
[0032] FIG. 2 is a schematic illustration of the receiver system
illustrated in FIG. 1;
[0033] FIG. 3 is a schematic illustration of the transmitter system
illustrated in FIG. 1;.
[0034] FIG. 4 is an exploded perspective of a toy automobile in
accordance with the present invention;
[0035] FIG. 5 is a schematic illustration of a toy automobile in
accordance with the present invention illustrating an example of a
dust cone and a portion of an antenna;
[0036] FIG. 6 is a schematic illustration of a toy automobile in
accordance with the present invention further illustrating the
antenna example of FIG. 5; and
[0037] FIG. 7 is a schematic illustration of a toy automobile in
accordance with the present invention further illustrating the dust
cone.
DESCRIPTION OF SPECIFIC EXEMPLARY EMBODIMENTS
[0038] Referring now to FIGS. 1-3, a radio controlled toy
automobile system 10 is illustrated and includes a plurality of
control sets x-1 to x-N that may be simultaneously energized to
transmit command signals to a plurality of toy automobiles 1 to N.
Each control set, for example, controller 1, includes a transmitter
11, a channel select code generator 12 providing a selectable
channel code, such as for example, any one of channels 1-N to
transmitter 11, a speed command generator 13 and a steering command
generator 14. Transmitter 11 repetitively transmits bursts of
command signals containing channel, speed, steering and control
data on antenna 15 that are received only by the automobile tuned
to the particular corresponding transmitter channel. Note, for
simplicity and clarity, the present invention is being described
with reference to a toy automobile. Those skilled in the art will
understand that many features of the present invention are
applicable to other devices and systems. Power is preferably
provided by a battery 16.
[0039] Furthermore, the present invention is generally directed to,
and makes possible, radio controlled miniature toy vehicles that
are typically {fraction (1/58)}-{fraction (1/62)} in scale or
smaller. In real terms, this works out to vehicles that are
generally 3" long or smaller when the toy vehicle is an automobile,
truck, etc.
[0040] Each toy automobile, for example, toy automobile x-1,
contains a receiver 20 that is tuned to the respective transmitter
channel by means of a selector switch 21 and receives a signal from
an antenna 22, and that in turn feeds the demodulated signals to a
command decoder 23. When a command burst received in the receiver
and applied to the command decoder is correct, the command decoder
stores the steering, speed and control signals and begins
producing: a) steering pulses for the steering motor that is
coupled to a steering apparatus 24; b) a pulse width modulated
drive signal that is applied to a drive motor 25; and c) digital
control signals that may operate devices such as lights, horns,
etc. (Not shown). Power is preferably provided by a battery 26.
[0041] In FIG. 4, selector switch 21 is illustrated as a switch or
button on the receiver printed circuit board. In an alternative
embodiment, a push button is provided with an LED on the bottom of
the vehicle. The default channel is one. To change the channel, the
push button is depressed a corresponding number of times for a
desired channel. The LED flashes the corresponding number of
times.
[0042] Preferably, proportional steering is accomplished by means
of a stepper motor 27 included with the toy vehicle. This permits
precise control of the steering mechanism with a low power
requirement, which could be by means of a worm gear turning other
gears or a spur gear turning other gears and/or the addition of a
steering rack. Preferably, the wheel hubs are an integral part of
the mechanism to help keep it simple and small.
[0043] The steering signal fed from the command decoder to a
steering drive apparatus 28 is converted to a 2-phase stepper motor
drive signal. When the vehicle is first turned on, it centers its
steering by driving the steering to one end of its travel then
returning a preset number of stepper motor steps. Steering commands
are then executed to turn the vehicle right or left by sending the
appropriate number of pulses to the stepper motor. The controller
keeps track of the position of the steering mechanism by storing
the pulse count. Such a control system which responds directly to
commands is known as an "open-loop" control system.
[0044] The speed signal fed from the command decoder to the drive
apparatus is converted to a pulse-width modulated signal, which is
applied to a direct current motor and determines the speed at which
the toy vehicle is driven. It may be seen in FIG. 1 that no
feedback line is provided from drive apparatus to the command
decoder. Such a control system which responds directly to commands
is known as an "open-loop" control system.
[0045] The command decoder preferably responds only to a command
burst which is correct in every respect. Command bursts received
with any errors are preferably rejected by the command decoder that
continues to execute the last properly decoded command burst it
received. Preferably, an entire set of channel, speed command,
steering command and control signals is transmitted in a command
burst. As previously noted, the command decoders preferably reject
all command bursts that are not correct in every respect.
Preferably, the command decoder stores, and continues to execute,
the last properly decoded command signals until the next properly
decoded command burst occurs. Thus, when interference causes
rejection of one or two command bursts, execution of the most
recent command continues for one or more additional periods until
the next properly decodable signal is received. By making the burst
repetition frequency high enough, the loss of one or a few
consecutive command bursts has little or no noticeable effect on
the performance of the controlled vehicle.
[0046] The command burst may have any format capable of
transmitting the required information including time, frequency,
position and width coding, but in a preferred embodiment, digital
coding sent and received by a standard UART (Universal Asynchronous
Receiver/Transmitter) in NRZ format is employed. Preferably, seven
bytes are sent in each command burst. Obviously, more or less bits
may be sent as needed or desired. The first byte, called the
preamble, is used by the receiver demodulator to set the slicing
level and as an indication that this is the first byte in the
burst. This byte has a unique value that never occurs in any other
byte. The next byte is the channel number and is used only to
verify that the receiver is set to the same channel as the
transmitter. Only eight channels are allowed and are encoded in the
four least significant bits (low nibble) of the byte. The four most
significant bits (high nibble) are set to the compliment of the
least significant bits and is used for error detection by the
receiver as well as maintaining the slicing level for the
demodulator. The speed command which is an eight bit value is
encoded into the next two command burst bytes. The first byte
contains the low nibble of the speed command in its low nibble and
the compliment of it in the high nibble. The second byte contains
the high nibble of the speed command in its low nibble and the
compliment of it in the high nibble. As with the channel byte, this
system is used for error detection by the receiver as well as
maintaining the slicing level for the demodulator. The steering
command, which is preferably an eight bit value, is encoded into
the next two command burst bytes in a similar manner to the speed
command. The last byte is the control command and is used to
control functions such as lights or a horn on the vehicle. Only
four bits are used and are encoded in the four least significant
bits (low nibble) of the byte. The four most significant bits (high
nibble) are set to the compliment of the least significant bits as
with the previous command bytes.
[0047] The table below shows the equivalent decimal ranges
available for the channel code, speed command, steering command and
control command signals.
1 NUMBER NOMINAL DECIMAL RANGE COMMAND OF BYTES MINIMUM CENTER
MAXIMUM PREAMBLE 1 85 85 85 CHANNEL 1 0 N/A 7 SPEED 2 0 128 254
STEERING 2 0 128 254 CONTROL 1 0 N/A 15
[0048] The 8-bit speed command signal has 254 possible decimal
values, the nominal range employed is from 0 (maximum reverse
speed) through 127 (stopped) to 254 (maximum forward speed). The
8-bit steering command signal has 254 possible decimal values, the
nominal range employed is from 0 (full left) through 127 (straight
ahead) to 254 (full right). An automatic bias correction is
generated in the command encoder to produce operation centered on
decimal numeral 128. More channels may be included depending upon
the requirements and the design.
[0049] A speed command generator preferably comprises a manually
controllable speed variable resistor between a voltage supply +V
and ground with the wiper an input of a speed A/D converter input
to the processor. Similarly, the steering command generator
includes a manually controllable steering variable resistor
connected between a voltage supply +V and ground with the wiper an
input of a speed A/D converter input to processor.
[0050] The channel select switch is optionally an octal rotary
switch connected to inputs of the transmitter controller. Any octal
number from 0 may be applied to the transmitter controller. Other
techniques for providing a channel select code to transmitter
controller should be considered within the scope of the present
invention.
[0051] The controller preferably sends a seven byte command burst
approximately every 15 milliseconds. The command bursts are
generated by the microcontroller and coupled to the transmitter IC.
The transmitter IC then generates a frequency modulated, radio
frequency signal and transmits this signal via antenna. Other forms
of modulation may be considered within the scope of the present
invention.
[0052] When the controller is first turned on, the microcontroller
reads the channel select switch and sends control signals to the
transmitter to set its frequency to the selected channel. The
microcontroller then reads the analog inputs for speed and
steering, converts their respective inputs to an eight bit digital
byte then applies an offset to them that when added to the digital
value converts that digital value to a decimal value of 128. It is
assumed that when the transmitter is first turned on, the speed and
steering controls are in their neutral position; in other words
motion stopped and steering straight ahead.
[0053] When the receiver is first turned on, the microcontroller
tunes the RF receiver IC to the channel selected by the user. The
receiver is now ready to receive command bursts from the
controller. A timer is also preferably implemented such that if no
acceptable signal is received within a preset period of time, the
receiver turns off all of its power, thus conserving battery
life.
[0054] The user selects a desired channel on the receiver and
transmitter before turning on their respective power switches.
Preferably, there are eight channels and thus, the user selects any
channel between 0 and 7.
[0055] Once the receiver and transmitter are both turned on and set
to the same channel, the system is ready for normal operation.
[0056] In a preferred embodiment, the radio system is operating in
the 800 MHz to 1000 MHz band. Operation in any other frequency
range may be considered within the scope of the present
invention.
[0057] Referring now to the vehicle system shown in FIG. 1, command
bursts received from a transmitter are coupled from the antenna to
the receiver which was previously set to the transmitter channel
during startup.
[0058] The steering signal fed from the command decoder to the
steering drive apparatus is converted to a 2-phase stepper motor
drive signal. The steering stepper motor applies mechanical force
to control the angle to which steering wheels, not shown, are
turned to deflect them toward the left or the right. When the
vehicle is first turned on, it centers its steering by driving the
steering to one end of its travel then returning a preset number of
stepper motor steps. Steering commands are then executed to turn
the vehicle right or left by sending the appropriate number of
pulses to the stepper motor. The controller keeps track of the
position of the steering mechanism by storing the pulse count.
[0059] A pulse width modulated speed signal is applied from the
command decoder to a speed control circuit. The pulse width
modulated speed signal is applied to a speed drive circuit which,
in turn, applies the pulse width modulated speed signals to a speed
drive motor. The speed drive motor produces either a forward
torque, a rearward torque according to the input from the speed
drive circuit. It should be noted that there is no signal fed back
to the command decoder representative of the speed at which the
drive wheels are rotated.
[0060] If a vehicle fails to receive an error free command burst in
a predetermined period of time, suitably from about 0.1 to about
0.3 seconds, the command decoder stops the drive motor. This avoids
the toy vehicle running away and becoming lost or damaged when the
control signal is lost due to distance, malfunction or turning off
the control set.
[0061] In a preferred embodiment, the power from the rechargeable
battery is split into two sources. The first source (Vbat) is used
for logic control and the second source (Vbat-P) is used for drive
and steering. Partitioning of the power sources in this way permits
relatively tight regulation of the DC power employed in logic
control without placing unnecessary limitations on the relatively
high current power sources required by the steering motor and the
speed drive motor. Thus, the drive systems are capable of operating
with an unregulated battery source that may be isolated from the
regulated logic DC source.
[0062] Preferably, a battery fabricated with a technology that
allows it to be made very thin is used. Preferably, it is designed
in some degree to fit the shape of the vehicle. In an alternative
embodiment, the battery is an integral part of the mechanical
construction of the car. By designing the battery to the desired
shape of the product, one may optimize the energy capacity and no
longer be hindered by its conventional shape. The product may be
designed as required and the battery shaped to be an integral part
of the design.
[0063] Preferably, as may be seen in FIG. 4, each vehicle has a
removable body 30. Thus, various chassis 31 have several common
bodies. For example, NASCAR shaped cars are quite similar in
chassis although there are a few brands and many
advertisers/drivers. By making removable bodies, people may retain
their existing chassis (and their investment in the
mechanical/electrical portion of the vehicle) and change bodies
based on their favorite drivers and advertisers each year. Another
example is an SUV chassis as well that may take various branded
bodies.
[0064] With reference to FIGS. 5 and 6, an example of an antenna 40
may be seen. Typical radio controlled cars have very large and
disproportionate to scale antennas. The present invention
preferably uses a higher frequency signal (900 Mhz range) to reduce
the need for a larger antenna. Due to the extremely small scale of
vehicles in accordance with preferred embodiments of the present
invention, a larger or longer antenna would look out of scale.
Thus, in accordance with a preferred embodiment of the present
invention, the antenna is located under the car, mounted to the
bottom of chassis 31. Additionally, preferably antenna 40 comprises
a metallic strip. Such a design provides better performance than
just using a traditional wire antenna. Furthermore, the design
doesn't detract from the appearance of the vehicle.
[0065] With reference to FIGS. 5 and 7, a dust cone 50 is
illustrated. Radio controlled vehicles often pick up lint and
carpet fibers etc., that wrap around the axles, tighten up and
usually cause the vehicles to run slower or even stop. The dust
cone is preferably in the form of a "lint ring" that extends from
the chassis into an inner portion 51 of wheel hubs 52.
[0066] Thus, the present invention provides a miniature remote
control vehicle with variable control that operates independently
by means of wireless operation. Advantages include:
[0067] 1) Uses a high frequency thus reducing the size of antenna
to maintain proportionality of scale;
[0068] 2) Controlled with variable steering preferably using a
stepper motor (Alternative methods include servo or sensors
combined with new motor design or shape, such as piezo, or two
coils (motors) connected together like a stepper motor);
[0069] 3) Battery designed to the required shape of the vehicle.
(Use of a battery as an integral part of the design of the product,
i.e. making the vehicle where the form/shape of the battery is made
to a structural part of the design, such as making the battery the
shape of the vehicle chassis. This allows maximizing the energy
capacity and making the vehicle smaller/thinner/lighter);
[0070] 4) Additional functions besides variable speed and steering
permitted through coding design. (for example light and sound);
[0071] 5) Uses internal frequency calculation and channel selector
switch to permit simultaneous operation of multiple vehicles;
and
[0072] 6) Small size allows car to be used in conjunction with
large base of existing miniature tracks and play sets.
[0073] Following are examples of receiver and transmitter operation
in outline form:
2 RECEIVER OPERATION 1. General initialization a. Initialize I/O
ports b. Initialize variables c. Turn on 2.8 V to RF section d.
Initialize pulse-width-modulator for speed control e. Initialize
A/D converter for battery voltage checking (AN3) and
steering-centering pulse count value (AN0) f. Initialize software
serial port for receive g. Read address switch h. Initialize
frequency synthesizer per address switch setting i. Get steering
centering step count (AN0) j. Center steering k. Initialize and
start no-data-timer l. Wait for good data packet m. Center steering
again (an indication that good data is being received) 2. Main loop
a. Perform no-data test i. If no good-data packets received in 1/4
second, shut off motors and control outputs b. Execute steering
control commands i. Convert steering command to number of steps for
stepper motor. To prevent wheels from going to end stops (either
left or right), scale steering input such that wheels turn only a
fixed percentage of maximum (presently 88%) ii. Test if steering
command has changed by at least 2 counts 1. If not, do nothing 2.
If changed, get value of change and move stepper motor in
appropriate direction c. Execute speed control commands i. If speed
command too small (less than 4) assume zero speed and stop motor
and perform battery voltage check ii. If speed command greater than
4, test for direction (forward or backward) and set pulse-
width-modulator and direction control (PC7) as required to run
motor d. Execute digital control commands i. Set control outputs
PA4 or PB4 as requested by control byte e. Check battery voltage
and shut-down vehicle when battery voltage is too low to provide
reliable operation. 3. Interrupt functions (background tasks) a.
Check UART for received data and if available: i. Assemble received
data into complete packet and check for integrity ii. If data
packet check OK, set new speed, steering and control bytes for use
in main loop iii. If data packet bad, reject all data and do not
change speed, steering and control bytes used in main loop b. Timer
interrupt used for no-activity timer i. No-activity timer reset
when good data packet is received. ii. On no-activity timeout,
turned off power to the RF chip, shut off motors and control
outputs, set the processor I/O for lowest current drain and put
processor into sleep mode TRANSMITTER OPERATION 1. General
initialization a. Initialize I/O ports b. Initialize variables c.
Initialize software serial port d. Initialize timer 1 for use as
no-activity timer e. Set up interrupts f. Initialize A/D converter
g. Read address switch h. Initialize the frequency synthesizer i.
Read the controller potentiometer center settings j. Normalize
potentiometer settings to 80 h k. Enable global interrupts 2. Main
loop a. Read potentiometer (steering and speed) inputs and reset
no-activity timer if potentiometers have been moved. Limit speed
and steering outputs to 0 and FEh b. Check battery voltage i.
Provide indication to user of low battery. ii. Shut off transmitter
when battery voltage is too low for reliable operation. c. Send
data packet i. Send preamble byte (55 h) ii. Send address switch
setting as one byte iii. Send speed setting as two bytes iv. Send
steering setting as two bytes v. Read and send control bits as one
byte 3. Interrupt functions (background tasks) a. UART interrupt to
send data. b. Timer interrupt used for no-activity timer i.
No-activity timer reset when potentiometer movement is detected.
ii. On no-activity timeout, power is turned off to the RF chip and
the processor I/O is set for lowest current consumption and
processor is placed into sleep mode
[0074] Having described specific preferred embodiments of the
invention with reference to the accompanying drawings, it is to be
understood that the invention is not limited to those precise
embodiments and that various changes and modifications may be
effected therein by one skilled in the art without departing from
the scope or spirit of the invention as defined in the appended
claims.
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