Securely stopped vehicle method and apparatus

The braking system of a vehicle is securely engaged in response to the operator of the vehicle causing the vehicle to stop. The vehicle being stopped is determined in response to several conditions including a predetermined time of stopping as well as suspensions settling time. The braking system remains securely engaged in the event of a moving vehicle colliding with the stopped vehicle. The braking system also remains securely engaged even if the foot of the operator is removed from the vehicle's brake pedal. The braking system is disengaged in response to the operator accelerating the vehicle, such as the operator's pressing of the vehicle's gas pedal, release of the vehicle's clutch and/or release of the vehicle's brake pedal. The rate of release of the braking system is responsive to the gas pedal position. The braking system is released rapidly in response to a substantially depressed gas pedal to facilitate a rapid start. The braking system is release gradually in response to a partially depressed gas pedal to facilitate a smooth start.

FIELD OF THE INVENTION
 This invention relates in general to the field of vehicles and more
 particular to the field of vehicle braking systems.
 BACKGROUND OF THE INVENTION
 A vehicle, such as a street driven automobile, often stops at intersections
 in response to traffic lights. While waiting for a traffic light signal to
 indicate a time to accelerate, the vehicle is supposed to remain stopped.
 A problem arises when, contrary to the intention of a vehicle operator,
 the vehicle does not remain stopped. One example of a situation where a
 vehicle may undesirably accelerate from a stopped condition is when an
 operator's foot accidentally slips off of the vehicle's brake pedal.
 Another example is when a vehicle is impacted from the rear, the
 operator's foot may slip off the brake pedal or may not have enough brake
 pressure to prevent forward motion of the vehicle. Such situations can
 result in a collision with another vehicle. Since vehicle collisions are
 undesirable, it is desirable to provide a vehicle that remains securely
 stopped when the operator intends the vehicle to be stopped.
 When the traffic light generates a green light signal, it is desirable to
 provide a securely stopping vehicle which accelerates in a way the
 operator is accustom: fast starts for rapid acceleration and smooth starts
 for normal acceleration. Furthermore, when operating the vehicle in slow
 traffic or approaching a stop light it is desirable that a vehicle with
 secure stopping does not interfere with low speed acceleration and braking
 of the vehicle.

DETAILED DESCRIPTION OF THE INVENTION
 FIG. 1 shows a block diagram of a vehicle operating in accordance with the
 present invention. The vehicle has four wheels, 101-104, each wheel having
 a corresponding brake, 105-108. The brakes 105-108 may be either disk or
 drum or other system for stopping the vehicle. In a front wheel drive
 embodiment, the front wheels 101-102 are driven by an engine 110 and a
 transmission 112. The engine is preferably an internal combustion engine
 as is commonly used in vehicles today. The transmission is either an
 automatic transmission or a manually shifted transmission having a
 manually operated clutch for coupling the engine to the wheels. The engine
 is manually throttled by a throttle or gas pedal 120 and the clutch is
 manually controlled by a clutch pedal 122. A brake controller 130 is
 manually operated by a brake pedal 135. The brake controller may include a
 master cylinder or an anti-lock brake system for controlling the brakes
 105-108. In operation, when a foot of the operator applies increasing
 pressure to the gas pedal, the speed of the vehicle increases. When the
 foot of the operator applies pressure to the brake pedal, the speed of the
 vehicle decreases. The amount of pressure applied to the brake pedal
 regulates the rate at which the speed of the vehicle decreases. When the
 vehicle has stopped, typically very little brake pressure is required to
 maintain the vehicle in a stopped condition. In a vehicle with an
 automatic transmission, the typical user applied brake pressure need only
 be enough to overcome the minimal acceleration of an idling engine which
 is applied to the wheels. In a vehicle with a manual transmission, the
 typical user applied brake pressure need only be enough to overcome
 accelerations due to the vehicle being situated on a hill.
 With such little pressure required to typically maintain a vehicle in a
 stopped condition, an operator may unintentionally provide too little
 brake pressure, enabling the vehicle to move, which may result in a
 collision. Examples of unintentionally providing too little brake pressure
 include: when the operator is excessively tired or sleepy; when the
 operator is tending to other matters while the vehicle is stopped, such as
 caring for children, fetching documents, or operating a radio receiver,
 cassette tape or compact disk; or when the operator is actively engaged in
 conversations on a wireless phone or with fellow passengers or while
 singing a song.
 Furthermore, with such little pressure required to typically maintain a
 vehicle in a stopped condition an operator is unlikely to be providing the
 significant brake pressure needed to prevent the vehicle from colliding
 with a third vehicle in the event of being impacted by a second moving
 vehicle. This is particularly true if the operator's vehicle is impacted
 from either from the rear or front by the second vehicle. Such collisions
 are typical when a vehicle is stopped at an intersection.
 When acceleration from a stopped condition is desired, because a traffic
 light turns green for example, the foot of the operator of a vehicle with
 an automatic transmission is typically removed from the brake pedal and
 applied to the gas pedal. A small delay results from the time the light
 turns green and the foot is moved from the brake pedal to the gas pedal.
 The operator of a vehicle with a manual transmission typically has one
 foot an the clutch pedal and one foot on the brake pedal waiting for the
 traffic light to turn green. A triple movement is required when the light
 turns green, one foot is removed from the brake pedal and then applied to
 the gas pedal while the second foot releases the clutch pedal. This can be
 a complex operation, particularly when the vehicle is directed up a hill
 because the vehicle tends to unintentionally roll backwards between the
 time when the brake pedal is released, the gas pedal is pressed and the
 clutch pedal is released.
 The invention provides for the problems with a secure stop controller 150
 and a stop detector 155. The secure stop controller 150 receives signals
 from the gas pedal 120, clutch pedal 122, brake pedal 135 and stop
 detector 155 and applies an additional signal to brake controller 130 to
 apply or release brakes 105-108. The stop detector 155 is coupled to a
 velocity detector such as a speedometer. Alternately, the stop detector
 155 may be used in conjunction with a slip detector, an anti-lock brake
 system or other vehicle component that is able to determine if the vehicle
 is stopped. In the preferred embodiment the stop detector 155 generates a
 vehicle stopped signal shortly after the vehicle has stopped.
 FIG. 2 shows a basic flow diagram for a method of securing a motor vehicle
 in a stopped condition in accordance with the present invention. Refer
 also to FIG. 1. When step 160 determines that the vehicle has stopped,
 stop detector 155 generates a vehicle stopped signal. Most normal driving
 functions are performed during step 160, until the vehicle is stopped. In
 response, secure stopping is engaged at step at step 162 where the secure
 stop controller 150 sends a secure stop signal to the brake controller 130
 to engage the brakes 105-108 with a force equivalent to significant brake
 pedal pressure. If the brake controller is an anti-lock brake system, the
 brake controller may modulate the brakes to provide improved stopping
 power in the event of a collision with the second moving vehicle. Since
 the vehicle is stopped, the operator is unaware of any significant braking
 force applied to brakes by the secure stop controller. Then step 164
 determines if the operator intends for the vehicle to accelerate. In
 various embodiments this determination is made in response to the operator
 applying pressure to the gas pedal, releasing the clutch pedal or
 releasing the brake pedal, or a combination thereof. In response, step 166
 disengages secure stopping. Secure stop controller 150 terminates the
 secure stop signal and the brake controller 130 disengages the brakes
 105-108 allowing the speed of the vehicle to increase.
 FIG. 3 shows a detailed flow diagram of the step of determining if a
 vehicle has been stopped. This corresponds to step 160 of FIG. 2. After
 entry at step 170, a timer is reset at step 172. The timer continues to be
 reset if vehicle velocity is not zero at step 174 and the brake pedal is
 not pressed at step 176. If however, the velocity is zero and while the
 brake pedal remains pressed for preferably two seconds at step 178, then
 the vehicle stopped signal is generated and the flow exits at step 180 to
 proceed to step 162 of FIG. 2. Thus, the vehicle is stopped for a
 predetermined time of two seconds with the brake applied before the secure
 stop signal is generated at step 162. Other predetermined times may be
 used. Alternately, the vehicle stopped signal could be generated when the
 velocity is zero for a different predetermined time. Or the vehicle
 stopped signal could be generated after the vehicle has stopped and the
 suspension settles out from the typical front end dive and consequential
 rocking motion resulting from the vehicle stopping. This settling could be
 sensed by a vehicle with active suspension or suspension motion sensors or
 accelerometers. This embodiment automatically compensations for aging
 suspension components such as shock absorbers that may increase the
 suspension settling time with age. These methods are an improvement over
 generating the vehicle stopped signal simply in response to the speed
 equaling zero because the secure stopping system is typically not engaged
 in stop and go traffic where a vehicle crawls along at a low speed with
 abrupt applications of the brake which may temporarily bring the vehicle
 to a stop. In such cases it may be desirable to not engage the secure
 stopping.
 FIG. 4 shows a detailed flow diagram of the step of determining if a
 vehicle is to accelerate. This corresponds to step 164 of FIG. 2. After
 entry at step 190 step 192 checks if the clutch is released. This step is
 always "NO" for an automatic transmission. Step 194 checks if the gas
 pedal is pressed. This is an optional step for a manual transmission. This
 process effectively causes the system to remain in the secure stop mode
 until the operator either releases the clutch or presses on the gas pedal.
 Upon detection of either event, the process exits through step 192 to step
 166 of FIG. 2 to disengage the secure stop mode. In the preferred
 embodiment, once the secure stop mode is engaged, the vehicle will remain
 stopped if the brake pedal pressure is reduced or even if the operator's
 foot is removed from the brake. This prevents unintentional movement of
 the vehicle. Furthermore if the vehicle is on a hill, it will not roll
 backwards. This simplifies the problem of accelerating from a stopped
 condition with a manual transmission while on a hill because the vehicle
 does not start to move as soon as the operator's foot is removed from the
 brake. In an alternate embodiment where the secure stop mode is released
 only in response to release of the clutch. In this embodiment the operator
 may even begin to rev the engine before the secure stop mode releases
 brakes in response to the operator releasing the clutch, thereby assuring
 that the engine is producing sufficient power to begin climbing the hill
 as the clutch is released. A further step may be added to ensure that the
 transmission is not in a neutral condition before disengaging the secure
 stop mode.
 FIG. 5 shows a detailed flow diagram of the step of disengaging the secure
 stop mode. This corresponds to step 166 of FIG. 2. The flow enters at step
 200. Step 202 checks if the throttle or gas pedal 120 is more than halfway
 depressed. This step corresponds to determining the magnitude of a desired
 acceleration signal. If true then step 204 causes the secure stop signal
 to terminate in such a way as to cause the brake controller 130 to rapidly
 disengage the brakes 105-108. In this embodiment, the operator
 substantially depresses the throttle indicating a desire for rapid
 acceleration. In response, the brakes are rapidly released. However, if
 the throttle is less than half depressed, it is presumed that the operator
 desires a smoother transition from a stopped vehicle to a moving vehicle
 and the brakes are gradually released. Step 208 releases the brakes by 20%
 of the maximum secure stop setting every one hundred milliseconds until
 the brakes are released at step 210. This process occurs so long as the
 operator's foot remains on the gas pedal at step 212. Assuming the secure
 stop mode provides a maximum engagement of the brakes, steps 202, 208, 210
 and 212 gradually release the brakes of a predetermined time as the gas
 pedal is depressed. In the preferred embodiment, the brakes transition
 from fully engaged to fully disengaged over a one-half second interval. If
 at any time during that one-half second interval throttle is depressed to
 more than one half at step 202, the brakes are entirely disengaged at step
 204, allowing for more rapid acceleration. FIG. 5 shows one example of a
 release of the brakes corresponding to an amount of desired acceleration.
 Predetermined values other than those shown in FIG. 5 are anticipated.
 Other variations are also anticipated including a more direct relationship
 between throttle position and release rate of the brakes wherein the rate
 may be non-linear. Alternately, the brakes could be released according to
 a predetermined process that is independent of the throttle position,
 including a simple rapid release of the brakes.
 For the vehicle operator desiring rapid acceleration from a traffic light,
 steps 200-206 adds no delay over a vehicle that does not have a secure
 stop mode. Indeed the secure stop mode enables even more rapid starts by
 reducing the time from the appearance of a green light to when the vehicle
 is accelerated. This is because the operator's foot may rest upon the gas
 pedal waiting for the green light while the secure stop mode applies the
 brakes for the operator. This eliminates the delay encountered by
 requiring the operator's foot to move from the brake pedal to the gas
 pedal in response to the green light.
 For the vehicle operator desiring a smooth transition from a vehicle
 stopped mode to a vehicle moving mode, the gradual release of the brakes
 by steps 200,202, 208 and 210 eliminate any sudden jerking acceleration
 experienced by a rapid release of the brakes. Furthermore, the process
 recovers from an accidental light punching of the gas pedal while waiting
 at a traffic light without necessarily having to reapply the brakes. If
 during the one half second gradual brake release process, the operator's
 foot is removed from the gas pedal as determined at step 212, then
 releasing of the brake of step 208 is discontinued until the velocity of
 the vehicle returns to zero at step 214. Alternately, brake pressure can
 be gradually increased to further facilitate stopping of the vehicle.
 Thereafter, the process returns to step 162 of FIG. 2 to enable the secure
 stop mode. Thus, a short tap on the gas pedal slightly releases the brakes
 allowing a slight movement of the vehicle. Since the brakes are still
 applied, albeit with less force, the vehicle slows to a stop and again
 returns to the secure stop mode. This allows the operator to "inch" the
 vehicle forward by lightly tapping on the gas pedal. In an alternate
 embodiment, this function may be eliminated by eliminating steps 212-216
 and having step 210 proceed directly to step 202.
 In an alternate embodiment, the determination an operator's desire for
 acceleration of step 164 could be made in response to the operator simply
 releasing the brake pedal. While this mode may not prevent the vehicle
 from moving when the operator's foot is removed from the brake, it does
 ensure that the vehicle's brakes are securely engaged even with a light
 brake pressure while the vehicle is stopped.
 The invention has the advantage in that most all of the hardware of FIG. 1
 exists in a modern automobile. Enhanced processes performed by the brake
 controller, 130, secure stop controller 150 and stop detector 155 may be
 implemented in software executed in either an automobile's anti-lock
 braking system and/or electronic system controller.
 Thus, what has been provided is a vehicle that remains securely stopped
 when the operator intends the vehicle to be stopped. What also been
 provided is a vehicle able to accelerate from a stop in a manner intended
 by the operator, as well as an improved mode of rapid acceleration from a
 stop and an improved mode of inching forward while stopped.