Travelling direction correction apparatus

A travelling direction correcting apparatus includes: a shift detection device for detecting a shift amount of a vehicle running on a road with respect to the road; a wheel brake pressure control device for pressure wheel brake pressures and controlling a wheel brake pressure distribution; and a cruise control device for commanding a wheel brake pressure distribution control to the wheel brake pressure control device. The wheel brake pressure distribution control includes the following processes: (1) at least one of a yaw rate, a lateral speed and a lateral acceleration is made an index, (2) a value of the index, which appears in the vehicle when its running direction is changed toward a direction along which the shift amount decreases, is added to a value of the index, which appears when the vehicle runs along a curved road, and a summed amount is made an object value and (3) the value of the index, which appears in the vehicle, is coincided with the object value.

BACKGROUND OF THE INVENTION
 The present invention relates to an automatic correction device in which
 the deviation of a vehicle from a running lane is automatically monitored
 and, when the deviation occurs, a brake pressure applied to at least one
 of the left and right wheel brakes is automatically increased, thereby
 automatically adjusting a distribution between pressures applied to left
 and right wheel brakes and returning the vehicle to the running lane.
 Hereafter, an adjustment of brake pressure distribution between left and
 right wheel brakes, i.e., a change of vehicle's travelling direction by a
 differential braking, is referred to as "brake steering".
 The above automatic correction of travelling direction is effective for
 temporarily securing the safety of the running vehicle, when a driver's
 watchfulness ahead of the running vehicle deteriorates, e.g., when the
 driver looks aside, falls asleep or is in a semi-comatose state before or
 after sleeping.
 In "A Warning and Intervention System to Prevent Road-Departure Accidents"
 recited in Vehicle System Dynamics Supplement 25 (1996), pp 383-396, a
 vehicle travelling direction is automatically adjusted in the direction
 along which the vehicle moves by a feedback control in which a front view
 ahead of the vehicle is photographed by a television camera and a running
 lane is detected by image processing, vehicle behavior is inferred from
 information detected by another sensor mounted on the vehicle, and when an
 unintended deviation from the running lane occurs, the amount of deviation
 determines the amount of control with respect to wheel brake pressure
 distribution.
 In "Correlation between Snaking of Vehicle and Awakening Degree" recited in
 Japan Automobile Technology Association's Scientific Lecture Preprints
 941, pp. 25-28 published in May 1994, there is suggested a technique in
 which the front view ahead of the vehicle is photographed by a television
 camera, a white line partitioning a running lane is detected by image
 processing, and a lateral shift amount of the vehicle is computed, thereby
 detecting a snaking state of vehicle.
 Detection of a running lane and detections of lane width, curve, a
 preceding vehicle or the like have been already suggested by the present
 applicant (for example, Japanese Patent Unexamined Publication No.
 6-213660). Further, there has been suggested a technique in which a
 television camera for photographing a front view ahead of the vehicle is
 turned to follow a lane curve, thereby tracing a forward running lane (for
 example, Japanese Patent Unexamined Publication No. 9-96507). Furthermore,
 there has been suggested a distribution control technique for wheel brakes
 (for example, Japanese Patent Unexamined Publication No. 8-207737). By
 combining these techniques, the aforementioned automatic correction of
 travelling direction can be realized.
 It is inferred that in the feedback control in which the amount of
 deviation determines the amount of control with respect to wheel brake
 pressure distribution, when the deviation amount is large, an increase in
 pressure for a wheel brake is high and when the former is small, the
 latter is low, so that the effect of correcting the deviation amount is
 high, but when the deviation amount is large a change in direction of the
 vehicle is great, so that depending on road conditions such an unstable
 behavior is liable to occur that an increase in wheel brake pressure
 becomes too high so the wheels are locked or that a change in direction of
 vehicle is so sharp the vehicle spins. Steering by a driver during running
 of a vehicle is performed generally in response to the car speed, a radius
 of curvature and the friction coefficient of the road surface. It is
 preferable that brake steering for the aforementioned automatic correction
 of travelling direction responds smoothly to a car speed, a radius of
 curve and a friction coefficient of road surface (these are combined and
 referred to as "running conditions"), and it is considered that brake
 steering not reflecting a driver's will should lay emphasis on a stable
 and gentle correction of direction rather than a rapid correction of the
 deviation amount. It is inferred that by introducing such parameters as a
 car speed, a radius of a curve, a yaw rate and the like to the
 aforementioned feedback control and revising the amount of operation in
 response to the above parameters, there is obtained an improvement in
 consistency and smoothness with respect to the running conditions.
 However, the characteristic that since the control amount is the deviation
 amount, if the deviation amount is large an increase in wheel brake
 pressure is high and a change in direction is large will be maintained
 because that characteristic is an object inherent in the aforementioned
 feedback control.
 A driver in another vehicle is uneasy if a preceding vehicle, or a vehicle
 running in the opposite direction, rapidly changes its direction. In the
 event that another vehicle deviates from the lane, it is easier to cope
 with that vehicle when it returns slowly but stably and gradually to the
 lane judging from its running state than when it exhibits such a behavior
 that it returns rapidly to the lane.
 It cannot be said that reliability of detecting a vehicle in the running
 lane is sufficient. Further, it is comparatively frequent that a deviation
 from the running lane or a change of the running lane is performed by a
 normal judgment of the driver in order to avoid another vehicle or an
 obstacle. Alternatively, the running lane is frequently changed as a
 result of the driver's intent. However, in these cases, a consistency
 between the driver's will and the brake steering is low. Therefore, it is
 preferable that a brake steering amount is made as small as possible in
 order to prevent a hindrance in driving the vehicle from occurring. To the
 contrary, when the driver's power of attention deteriorates (e.g., when
 the driver looks aside or falls asleep), it is preferable that the brake
 steering is strongly applied in the event that the vehicle deviates from
 the lane. However, at present it is difficult to realize these problems
 simultaneously by a feedback control.
 Further, in a usual road in which there are many parked or stopped vehicles
 and many telephone or electric poles, the radius of curvature is small or
 across which many people and vehicles traverse, an error in detecting the
 running lane is liable to occur. Further, even if the running lane is
 accurately detected, a change of running lanes and a deviation from a lane
 is frequently performed. Under such situations, in view of the driver's
 recognition and intention, it is highly possible that the aforementioned
 automatic correction of travelling direction becomes a malfunction and
 becomes an erroneous interference to the driver. When a vehicle runs on a
 large road, e.g., a freeway (road exclusively for vehicles), on which it
 can keep a comparatively high speed with little possibility of sharp
 steering for avoiding another vehicle or the like and whose smallest
 radius of curve is comparatively large, driving at a substantially
 constant speed with little steering continues for a long time. For
 example, there is also a situation where the driver selects an automatic
 cruising which conducts an intra-vehicle control or a fixed speed control.
 Under such running conditions, since the incentive to stay awake is small,
 it is liable to make the driver sleepy. The aforementioned automatic
 correction of travelling direction is effective for supplementing the
 driver's carelessness under such running conditions.
 SUMMARY OF THE INVENTION
 A first object of the present invention is to provide brake steering which
 is high in consistency with respect to the running conditions and is high
 in stability of direction correction. A second object of the present
 invention is to provide brake steering which jogs an uplift of the
 driver's power of attention.
 Further, a third object of the present invention is to increase the
 reliability of the aforementioned automatic control of travelling
 direction, which is appreciated by the driver. A fourth object of the same
 is to suppress an erroneous interference with the driver. A fifth object
 of the same is to increase the consistency and smoothness of brake
 steering with respect to the running conditions of vehicle.
 A first mode of the present invention for achieving the above first and
 second objects relates to the following (1).
 (1) A travelling direction correcting apparatus comprising::
 a shift detection device (140, 160) for detecting a shift amount of a
 vehicle (CAR) running on a road with respect to the road;
 a wheel brake pressure control device (10, 30) for increasing the pressure
 in wheel brakes (51-54) of the vehicle and controlling wheel brake
 pressure distribution; and
 cruise control means (100) for commanding a wheel brake pressure
 distribution control to the wheel brake pressure control device (10, 30),
 where in the wheel brake pressure distribution control the following
 processes are implemented:
 (1) at least one of a yaw rate (Y), a lateral speed and a lateral
 acceleration (GY) provides an index,
 (2) a value (yawS) of the index, which appears in the vehicle when its
 running direction is changed toward a direction along which the shift
 amount decreases, is added to a value (v/R) of the index, which appears
 when the vehicle runs along a curved road, and a summed amount (v/R+yawS)
 is made an object value and
 (3) the value (Y) of the index, which appears in the vehicle, is coincided
 with the object value (v/R+yawS).
 The above wheel brake pressure distribution control, i.e., brake steering
 is not one in which the shift amount (deviation amount) is made a control
 amount, but the feedback control in which the yaw rate (Y), the lateral
 speed and/or the lateral acceleration (GY) are/is made a control amount.
 In the embodiment mentioned later by referring to the drawings, since the
 yaw rate (Y) is made a control amount, it is explained on the basis of
 this embodiment. The brake steering is a feedback control in which the yaw
 rate is made a control amount and the wheel brake pressure is made an
 operation amount. Since the yaw rate (Y) is a value responding to
 vehicle's running conditions, the summed value (v/R+yawS) obtained by
 adding the yaw rate (yawS) for brake steer to the yaw rate (Y.apprxeq.v/R)
 appearing when the brake steering is not acting is made an object value.
 If the wheel brake pressure distribution is controlled in such a manner
 that an actual yaw rate (Y: detection amount) coincides with the object
 value (v/R+yawS), a brake steering generating the yaw rate (yawS) by an
 amount of basis acts on the vehicle.
 A steering amount due to this steering does not depend on the shift amount
 (deviation amount), but is one which additionally generates the yaw rate b
 an amount of bias irrespective of what the vehicle speed (v) and the road
 curve radius (R) are. In other words, the vehicle is given a desired
 change of direction without being influenced by its running condition. In
 the embodiment mentioned later, the yaw rate by an amount of bias is
 expressed as yawS=.+-.2.degree./sec and is a low value. This yaw rate
 value is one which falls within a range defined by a lower limit value
 necessary for applying an effective pressure to the wheel brake and upper
 limit value below which it can be deemed that the vehicle's direction
 change is moderate and, moreover, it a value which is slightly lower than
 an intermediate value between the above lower and upper limit values. By
 this, the vehicle's direction change becomes one which is stable and
 moderate.
 (2) The travelling direction correcting apparatus further comprises
 annunciator means (110, 120), the cruise control means (100) emits a
 primary alarm at said annunciator means (110, 120) when the shift amount
 is more than a first set value (0 m), emits a secondary alarm at said
 annunciator means when the shift amount is more than a second set value (1
 m) which exceeds the first set value and commands the wheel brake pressure
 distribution control to the wheel brake pressure control device (10, 30).
 According to this, the first alarm is emitted when the vehicle's shift
 (deviation amount) from the lane is about to become large. When the
 vehicle's shift (deviation amount) is large, the secondary alarm (i.e.,
 brake steering implementation annunciation) is emitted and brake steering
 in the above (1) is automatically implemented.
 (3) The above index is a yaw rate (Y).
 (4) A travelling direction correcting apparatus comprising:
 a shift detection device (140, 160) for detecting a shift amount of a
 vehicle (CAR) running on a road with respect to the road;
 a wheel brake pressure control device (10, 30) for increasing the pressure
 in the wheel brakes (5154) of the vehicle and controlling a wheel brake
 pressure distribution; and
 annunciator means (110, 120); and
 cruise control means (100) which emits a primary alarm at the annunciator
 (110, 120) when the shift amount is more than a first set value (0 m),
 emits a secondary alarm when the shift amount is more than a second set
 value (1 m) which exceeds the first set value and commands a wheel brake
 pressure distribution control for decreasing the shift amount and
 fluctuating the shift amount in timed series to the wheel brake pressure
 control device (10, 30).
 According to this, the first alarm is emitted when the vehicle's shift
 (deviation amount) from the lane is about to become large. When the
 vehicle's shift (deviation amount) is large, the secondary alarm (i.e.,
 brake steering implementation annunciation) is emitted and the brake
 steering is automatically implemented. Since this brake steering decreases
 the lane deviation and fluctuates the shift amount in time series, the
 vehicle fluctuates leftward/rightward with respect to the direction along
 which the vehicle is traveling which is considered the center, thereby
 exerting a yaw rate vibration (lateral acceleration vibration) to the
 driver. This is different from the usual rate during steady running, so
 that the driver's power of attention is heightened. It is an advantage
 that the concerned vehicle attracts another driver's attention.
 (5) The travelling direction correcting apparatus further comprises means
 (YA) for detecting a yaw rate of said vehicle, wherein the wheel brake
 pressure control device (10, 30) performs a wheel brake pressure
 distribution in which a vibration yaw rate [yawS (1+sin .omega..tau.)],
 which is formed by superimposing a fluctuation yaw rate (sin .omega..tau.)
 increasing/decreasing in time series to a yaw rate (yawS) for correcting a
 shift in the same direction as a direction of a yaw rate appearing in the
 vehicle when its running direction is changed toward a direction along
 which the shift amount decreases, is computed and a yaw rate (Y) detected
 by the yaw rate detecting means (YA) is changed by an amount of the
 vibration yaw rate.
 (6) The wheel brake pressure control device (10, 30) performs a wheel brake
 pressure distribution in which a value, which is obtained by adding the
 vibration yaw rate [yawS (1+sin .omega..tau.)] to a yaw rate (v/R)
 appearing in the vehicle correspondingly to a vehicle speed (v) and a
 curve radius (R) of the road, is made an object yaw rate [yawO=v/R+yawS
 (1+sin .omega..tau.) ] and a yaw rate (Y) detected by the yaw rate
 detecting means (YA) is coincided with the object yaw rate (yawO).
 (7) The cruise means (100) tests yes/no of a travelling direction
 correction and, in the event that it is yes, emits a primary alarm at the
 annunciator means (110, 120) when the shift amount (deviation amount) is
 more than a first set value (0 m), emits a secondary alarm at the
 annunciator means (110, 120) when the shift amount is more than a second
 set value (1 m) which exceeds the first set value and commands a wheel
 brake pressure distribution control for decreasing the shift amount
 (deviation amount) to the wheel brake pressure control device (10, 30).
 According to this, "yes" is judged in accordance with a logic testing
 yes/no of the travelling direction correction and moreover the first alarm
 (i.e., preliminary alarm is emitted when the vehicle's shift (deviation
 amount) from the lane is going to become large. When y is judged in
 accordance with a logic testing yes/no of the travelling direction change
 and moreover the vehicle's shift (deviation amount) is large, the second
 alarm (i.e., brake steering implementation annunciation) is emitted and
 the brake steering is implemented. If the vehicle is returned by the
 driver to lane center in response to the primary alarm, the primary alarm
 is extinguished and the brake steering does not start.
 If a result of the travelling direction yes/no testing is "no", the primary
 alarm is not emitted, and the reliability of the primary alarm is high and
 so the effect of arousing the driver's attention is high. Since the second
 alarm exists when the brake steering is working due to an automatic
 intervention of the cruise control means (100), the driver can recognize
 the fact that the brake steering is working. The reliability with respect
 to the travelling direction automatic correction appreciated by the driver
 becomes high. By heightening the reliability of the travelling direction
 correction yes/no testing, erroneous interference with the driver becomes
 shall and moreover a consistency and a smoothness of the brake steering
 with respect to the vehicle's running conditions becomes high.
 For example, when the driver is dozing off and is not sufficiently awakened
 by the primary and secondary alarms, the vehicle fluctuates
 leftward/rightward with respect to the direction along which the vehicle
 is travelling which is considered the center, thereby exerting a yaw rate
 vibration (lateral acceleration vibration) to the driver. This is
 different from the yaw rate during a steady running and stimulates the
 driver, so that the effect of awakening a driver is high.
 (8) The cruise control means (100) commands a stoppage of the wheel brake
 pressure distribution control to the wheel brake pressure control device
 (10, 30) in response to the operation of equipment on the vehicle, which
 is performed by a driver. According to this, if the driver operates the
 equipment on the vehicle by being stimulated by the primary alarm, the
 secondary alarm or the fluctuating brake steering, the travelling
 direction correction is stopped. Since the primary alarm and the secondary
 alarm arouse the driver's attention and the travelling direction
 correction is stopped in response to the driver's equipment operation,
 interference to driving by the driver is small and the reliability
 appreciated by the driver becomes high.
 A second mode of the present invention for achieving the aforementioned
 third and fourth objects relates to the following (1).
 (1) A traveling direction correcting apparatus comprising:
 a shift detection device (160, 140) for detecting a shift amount (deviation
 amount) of a vehicle (MCR) running on a road with respect to said road;
 a wheel brake pressure control device (10, 30) for increasing wheel brake
 pressure (51-54) of said vehicle and controlling wheel brake pressure
 distribution;
 annunciator means (110, 120); and
 cruise control means (100) for commanding a wheel brake pressure
 distribution control to the wheel brake pressure control device (10, 30),
 wherein in the wheel brake pressure distribution control the following
 processes are implemented:
 (1) yes/no of a travelling direction correction is tested and
 (2) in the event that it is yes, when the shift amount (deviation amount)
 is more than a first set value (0 m) a primary alarm is emitted at the
 annunciator means (100, 120) and when said shift amount is more than a
 second set value (1 m) which exceeds the first set value a secondary alarm
 is emitted at the annunciator means (100, 120), thereby decreasing the
 shift amount (deviation amount). "Yes" is judged in accordance with a
 logic testing yes/no of the travelling direction correction and moreover
 the first alarm i.e., preliminary alarm is emitted when the vehicle's
 shift (deviation amount) from the lane is going to become large. When Y is
 judged in accordance with a logic testing yes/no of the travelling
 direction change and moreover the vehicle's shift (deviation amount) is
 large, the second alarm i.e., brake steering implementation annunciation)
 is emitted and brake steering is implemented. If the vehicle is returned
 by the driver to lane center in response to the primary alarm, the primary
 alarm is extinguished and brake steering does not start.
 If a result of the travelling direction yes/no testing is "no", the primary
 alarm is not emitted, and a reliability of the primary alarm is high and
 so the effect of arousing the driver's attention is high. Since the second
 alarm exists when the brake steering is working owing to an automatic
 intervention of the cruise control means (100), the driver can recognize
 the fact that the brake steering is working. The reliability with respect
 to the travelling direction automatic correction appreciated by the driver
 becomes high. By heightening the reliability of the travelling direction
 correction yes/no testing, an erroneous interference with the driver
 becomes small and moreover the consistency and the smoothness of the brake
 steering with respect to the vehicle's running conditions become high.
 (2) The cruise control means (100) judges that the travelling direction
 correction is yes when the vehicle speed automatic control (intra-vehicle
 control/fixed speed run) is instructed by a driver.
 In the embodiment mentioned later, if a fixed speed run is instructed by a
 switch operation of a driver, the cruise control means (100) writes a
 vehicle speed at that time in a object vehicle speed register. Thereafter,
 until a fixed speed run release condition is brought into existence, a
 throttle valve of engine mounted on the vehicle is subjected to an
 open/close control in such a manner that the vehicle speed coincides with
 the vehicle speed (object vehicle speed) of the object vehicle speed
 register. If an intra-vehicle control is instructed by a switch operation
 of the driver, until an intra-vehicle release condition is brought into
 existence, the throttle valve is subjected to an open/close control in
 such a manner that the distance from a preceding vehicle detected by a
 shift detection device (160, 140) becomes an intra-vehicle distance
 suitable for the vehicle speed.
 These vehicle speed automatic controls are suitable for a run on a road,
 such as a freeway, on which the vehicle can keep a comparatively high
 speed and the possibility of sharp steering for avoiding, for example,
 another vehicle is low and whose minimum curve radius is comparatively
 large. Start conditions and release conditions of the above automatic
 controls are highly similar to those of the brake steering. It is inferred
 from the fact that the above automatic controls are being implemented,
 correction (brake steering) is high and moreover safety in its
 implementation is high as well. Therefore, according to the present
 implementation mode, it may be said that the reliability of the travelling
 direction correction yes/no testing is high, an erroneous interference
 with a driver's driving is low and moreover the brake steering consistency
 and smoothness with respect to the vehicle running condition is high.
 (3) The cruise control means (100) judges that the travelling direction
 correction is yes when the vehicle running speed (V) continues for a time
 longer than a set time (five minutes) at a speed higher than a set value
 (60 Km/H). From this, it is inferred that the running state is stable and,
 moreover, a further stable run continues. In this case, since there is a
 possibility that a driver becomes careless, it is inferred that the
 necessity of the travelling direction correction (brake steering) is high
 and moreover safety in its implementation is high as well. Therefore,
 according to the present implementation mode, it may be said that
 reliability of the travelling direction correction yes/no testing is high,
 an erroneous interference with a driver's driving is low and moreover the
 brake steering consistency and smoothness with respect to the vehicle
 running is high.
 (4) The cruise control means 100 judges that the travelling direction
 correction is yes when the running road information on the basis of GPS
 position measurement and map data are (freeway/road exclusively for
 vehicles) corresponding to the vehicle speed automatic control yes. In the
 embodiment mentioned later, the GPS information processing ECU (190)
 computes a present position of vehicle on the basis of information
 received from GPS satellite, and map information possessed by the ECU
 (190) is referenced with the present position and a relative position
 between the road on which the vehicle is running, the present position on
 the map and the index is computed and outputted. In the map data, there
 are additional data representing the road's standards and regulations. The
 cruise control means (100) obtains such additional information from the
 GPS information processing ECU (190), and judges whether the road, on
 which the vehicle is running at present, is one on which it can run stably
 at a high speed for a long time. If it is judged so, it is judged that the
 travelling direction correction is yes.
 Precision and stability of the GPS position measurement and those of the
 map data, both being available nowadays, are high. Further, in case of a
 freeway, the vehicle's adaptability to the vehicle speed automatic control
 is high and so there is such a possibility that the driver will become
 careless. Accordingly, it is inferred that the necessity of travelling
 direction correction (brake steering) is high and safety in implementing
 it is high as well. Therefore, according to the present implementation
 mode, it may be said that reliability of the travelling direction
 correction yes/no testing is high an erroneous interference with a
 driver's driving is low and moreover the brake steering consistency and
 smoothness with respect to the vehicle running is high.
 (5) The cruise control means (100) judges that the travelling direction
 correction is yes when the instruction that the travelling direction
 correction is yes has been instructed (deviation alarm main SW is ON) by a
 driver. Since the travelling direction correction is made yes by the
 driver's will, and since it is possible for the driver to release that
 instruction to thereby make the travelling direction correction no,
 adaptability to the driver's will is high.
 (6) The cruise control means (100) judges that the travelling direction
 control is yes when a curve radius (R) of a running lane detected by the
 deviation detection device (160, 140) is larger than a set value (900 m)
 and a running time continues for a time longer than a set time (five
 minutes). From this, it is inferred that the running state is stable and,
 moreover, a further stable running continues. In this case, since there is
 a possibility that a driver becomes careless, it is inferred that the
 necessity of the travelling direction correction (brake steering) is high
 and moreover safety in its implementation is high as well. Therefore,
 according to the present implementation mode, it may be said that
 reliability of the travelling direction correction yes/no testing is high,
 an erroneous interference with a driver's driving is low and moreover, the
 brake steering consistency and smoothness with respect to the vehicle
 running is high.
 A travelling direction correcting apparatus comprising:
 a shift detection device (160, 140) for detecting a shift amount deviation
 amount of a vehicle (MCR) running on a road with respect to the road;
 a wheel brake pressure control device (10, 30) for pressure-increasing
 wheel brakes (51-54) of the vehicle and controlling a wheel brake pressure
 distribution;
 annunciator (110, 120) means; and
 cruise control means (100) which emits a primary alarm at the annunciator
 means (110, 120) when the shift amount (deviation amount) is more than a
 first set value (0 m), emits a secondary alarm at the annunciator means
 (110, 120) when the shift amount is more than a second set value (1 m)
 which exceeds the first set value, commands a wheel brake pressure
 distribution control for decreasing the shift amount to the wheel brake
 pressure control device (10, 30) and commands a stoppage of the wheel
 brake pressure distribution control to the wheel brake pressure control
 device (10, 30) in response to an operation of equipment on the vehicle,
 which is performed by a driver.
 According to this, the first alarm is emitted when the vehicle's shift
 (deviation amount) from the lane is going to become large. When the
 vehicle's shift (deviation amount) is large, the secondary alarm (i.e.,
 brake steering implementation annunciation) is emitted and the brake
 steering is automatically implemented. When the primary alarm or the
 secondary alarm is emitted, if a driver operates the equipment mounted on
 the vehicle, the travelling direction correction is stopped and the above
 alarm stops. Since the primary alarm and the secondary alarm arouse the
 driver's attention and the travelling direction correction is stopped in
 response to the driver's equipment operation, interference with the
 driving by the driver is low and a reliability appreciated by the driver
 becomes high.
 An operation effected by the driver to actuate the equipment on the vehicle
 is a turning the steering wheel mounted on the vehicle. When the deviation
 from the lane occurs, the member to be operated by the driver is the
 steering wheel. When a steering contradictory to the turning of steering
 wheel, an erroneous interference with the driver's will occurs by any
 chance, the driver stops the travelling direction change by the brake
 steering and operates the steering wheel in order to change the direction
 to an intended direction. In the present implementation mode, since the
 travelling direction correction is stopped in response to the driver's
 action and the reliability appreciated by the driver becomes high.
 (9) An operation effected by the driver to actuate the equipment on the
 vehicle is a turning of a steering wheel whose torque exceeds a set value
 (2 Nm). When the brake steering is contradictory to the driver's will, the
 driver stops the travelling direction change by the brake steering and
 operates the steering wheel in order to change the direction to an
 intended direction. In this case, the operation of steering wheel intends
 a direction change which is reverse in direction to the travelling
 direction change by the brake steering, so that rotational torque of the
 steering wheel is high. In the present implementation mode, since the
 travelling direction correction is stopped in response to this high
 torque, the brake steering is automatically stopped when the brake
 steering becomes an erroneous interference with the driving of the driver.
 Therefore, reliability appreciated by the driver becomes high.
 (10) An operation effected by the driver to actuate the equipment on the
 vehicle is a turn signal operation. If the driver operates a turn signal
 to change the lane, since the travelling direction correction is stopped,
 the brake steering automatically stops when it becomes an erroneous
 interference with the lane change effected by the driver.
 (11) An operation effected by the driver to actuate the equipment on the
 vehicle is an application of the brake pedal. Usually, the driver applies
 the brake pedal when avoiding nearness to another vehicle. Further, the
 brake pedal is applied when the vehicle reaches a state that the vehicle
 exhibits non-intended behavior. In that case, the brake steering is
 automatically stopped and it automatically stops when there is a
 possibility that it becomes an erroneous interference to the driving of a
 driver.
 (12) A travelling direction correcting apparatus comprising:
 a shift detection device (160, 140) for detecting a shift amount (deviation
 amount) of a vehicle (MCR) running on a road with respect to the road;
 a wheel brake pressure control device (10, 30) for pressure-increasing
 wheel brakes (51-54) of the vehicle and controlling a wheel brake pressure
 distribution;
 Annunciator means (110, 120); and
 cruise control means (100) which emits a primary alarm at the annunciator
 means (110, 120) when the shift amount (deviation amount) is more than a
 first set value (0 m), emits a secondary alarm at the annunciator means
 (110, 120) when the shift amount (deviation amount) is more than a second
 set value (1 m), which exceeds the first set value, and commands a wheel
 brake pressure distribution control for decreasing said deviation amount
 to the wheel brake pressure control device (10, 30), and; if the shift
 amount decreases to a value less than a third set value (10 m) which is
 less than the second value, commands a stoppage of said wheel brake
 pressure distribution control to said wheel brake pressure control device
 (10, 30), thereby stopping the alarm or changing said alarm to another
 annunciation.
 According to this, the first alarm is emitted when the vehicle's shift
 (deviation amount) from the lane is going to become large. When the
 vehicle's shift (deviation amount) is large, the secondary alarm (i.e.,
 brake steering implementation annunciation) is emitted and the brake
 steering is automatically implemented. This brake steering stops when the
 shift (deviation amount) has decreased to a third set value (0 m) less
 than the second set value which is a starting threshold of the brake
 steering. That is, with respect to start/finish of the brake steering,
 there are hysteresis characteristics to the shift (deviation amount).
 By this, there is no possibility that the brake steering is repeated in
 comparatively short cycle in such a manner that, e.g., if the shift
 (deviation amount) becomes above the second set value, the brake steering
 starts.fwdarw.by this brake steering if the shift (deviation amount)
 becomes below the second set value, the brake steering stops.fwdarw.by a
 small displacement if the shift (deviation amount) becomes the second set
 value, the brake steering starts. Therefore, reliability of automatic
 correction of travelling direction, which is appreciated by the driver, is
 improved and the brake steering consistency and smoothness with respect to
 the vehicle running conditions is high.
 Other objects and features of the present invention will become clear by
 the following description of embodiments making reference to the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 In FIG. 1, there is shown one embodiment of the present invention, which is
 mounted on a vehicle. A GPS position measurement device comprises a
 receiving antenna 201, a GPS receiver 202, a GPS demodulator 203, a
 display unit 205, a piezoelectric vibration gyro 206, an altitude sensor
 207, a GPS information processing ECU (electronic control unit) 190 and an
 operation board 204. An electric wave of 1.5742 GHz transmitted from each
 satellite of the GPS is received by the GPS receiver 202 via the receiving
 antenna 201, and information, i.e., information on a function representing
 the satellite's orbit, a time and the like, are demodulated by the
 demodulator 203 and inputted to the GPS information processing ECU 190.
 The GPS information processing ECU 190 is a computer system which
 comprises an armanac data memory, a map memory and a memory for date
 buffer as well as an input/output interface (electric and/or electronic
 circuit) and which has a microprocessor as its main component. The CPU
 generates information (latitude, longitude, altitude) representing a
 position of the concerned vehicle on the basis of information transmitted
 from the GPS satellite, and on the basis this position information one
 page (one screen) containing the above position is read from the map
 memory and this is displayed on the display unit 205, thereby displaying a
 present position index to the present position on display. Basic
 constituent such as the receiving antenna 201, the GPS receiver 202, the
 GPS demodulator 203 and the display unit 205 as well as basic operations
 of the GPS information processing ECU 190 are similar to respective
 constituent elements of a known apparatus already on sale.
 Analog signals outputted by the piezoelectric vibration gyro 206 and the
 altitude sensor 207 are respectively inputted to the GPS information
 processing ECU 190, and in the GPS information processing ECU 190 the
 inputted information is converted to digital data via an A/D converter and
 read thereby. Information outputted from the GPS demodulator 203 and
 information for controlling the GPS demodulator 203 are inputted to the
 CPU or outputted from the CPU via I/O port of the GPS information
 processing ECU 190.
 The GPS information processing ECU 190 computes three-dimensional
 coordinates Ux, Uy, Uz for the position of the concerned vehicle by a
 "3-satellite position measurement operation" or a "4-satellite position
 measurement operation".
 In a "3-satellite position measurement operation", three sets of data
 received from three satellites are substituted, respectively as
 parameters, to ternary simultaneous equations having been determined
 beforehand, and a latitude and a longitude at a reception point, which are
 unknowns, and a clock error at the reception side are obtained by solving
 these simultaneous equations. Further, in a "4-satellite position
 measurement operation", four sets of data received from four satellites
 are substituted, respectively as parameters, to quadruple simultaneous
 equations having been determined beforehand, and a latitude and a
 longitude at a reception point, which are unknowns, and a clock error at
 the reception side are obtained by solving these simultaneous equations.
 Furthermore, since the clock error at the reception side is obtained by
 either of the above position measurement operations, a built-in clock is
 calibrated on the basis of this error information.
 On the basis of position information obtained by the GPS position
 measurement, a map data of one page (one screen) containing that position
 is read from a map memory, and this is displayed on the display unit 205,
 thereby displaying the present position index for the present position on
 display. Then, the GPS information processing ECU 190 reads additional
 information, such as "road information, representing standards and
 regulations for a road on which the present position is located, and
 information representing this is displayed on the display unit 205 and
 data representing that the GPS data is effective and the road conditions
 are written in an output data storage area, which is addressed to a cruise
 control ECU 100 with a memory for DMA transfer within the GPS information
 processing ECU 190. When the GPS position measurement is unsuccessful,
 "invalid" is newly written in the above area, and when the GPS position
 measurement is successful, the fact that the GPS data is valid and the
 road information are newly written in the above area every time the road
 information is read from the map memory. The cruise control ECU 100 (its
 CPU) can read the data in the above area by using the DMA transfer when
 needed.
 A television camera 160 supported by a rotary mechanism 170 is connected to
 an image processing ECU 140. The rotary mechanism 170 contains therein an
 electric motor for rotary drive and reduction gears, and the camera 160 is
 fixed to an output rotary shaft of the reduction gears. The rotary
 mechanism 170 is supported by a frame, and as shown in FIG. 2 it is
 disposed in the vicinity of a central, upper portion of a front window
 within a vehicle MCR. The television camera 160 photographs a scene in
 front of the vehicle and outputs analog signals of 512.times.512 pixels
 per one frame.
 In case of a curved road, there is a strong possibility that the camera
 photographs in a direction deviated from the road. Accordingly, in the
 present embodiment, the image processing ECU 140 performs the detection of
 the running lane in front of the vehicle, a computation of a curve radius
 R of the lane, a computation of lane width, a computation of lane
 deviation amount (shift amount) of the concerned vehicle MCR, a detection
 of a preceding vehicle and a computation of the distance from the
 preceding vehicle, and when a preceding vehicle is not detected, the
 camera 160 is rotated in such a manner that the center of the camera's
 field of view is coincident with the lane center. When a preceding vehicle
 exists in the camera's field of view, the camera is rotated in such a
 manner that the preceding vehicle is placed in the center of the field of
 view.
 The camera 160 and constitution and function of the image processing ECU
 140 are similar to those suggested in the aforementioned Japanese Patent
 Unexamined Publication No. 6-213660. Further, constitution and function
 relating to rotating the camera 160 are similar to those suggested in the
 aforementioned Japanese Patent Unexamined Publication No. 9-96507.
 The image processing ECU 140's constitution and function and the camera 160
 and constitution and function of the camera's rotating mechanism are
 similar to those suggested in the aforementioned Japanese Patent
 Unexamined Publication No. 9-96507. The camera's photographed image is
 image-processed to detect a left white line (L: detection line) and a
 right white line (R: detection line) which partition a running lane, and a
 center line (Y) with respect to the vehicle width is defined and,
 thereafter, the lateral distance XL between L and Y and the lateral
 distance XR between Y and R are computed. This processing technique is
 disclosed in the aforementioned Japanese Patent Unexamined Publication No.
 6-213660. In the present embodiment, the image processing ECU 140 further
 computes the vehicle's left-side deviation amount [(Vw/w)-XL] with respect
 to the lane and the vehicle's right-side deviation amount [Vw/2-XR]. Vw is
 a vehicle width (lateral width). As between the left-side and right-side
 deviation amounts, the larger value is considered the lane deviation.
 Information of this lane deviation and whether the lane deviation exists
 left-side or right-side and information representing lane detection data,
 a lane curve radius R, a preceding vehicle detection -yes/no and a
 preceding vehicle distance (when a preceding vehicle is detected) are
 written together in a storage area, which is addressed to the cruise
 control ECU 100 and a memory for DMA transfer within the image processing
 ECU 140. When the detection of a running lane is unsuccessful, "invalid"
 is written or updated in the storage area. When the detection of a running
 lane is successful, every time the computation or detection of the curve
 radius R, the vehicle deviation amount, the presence of a preceding
 vehicle -yes/no and the preceding vehicle distance is performed, this
 information is written or updated in the storage area. The cruise control
 ECU 100, by means of its CPU, can read data in the storage area by using
 DMA transfer when desired.
 A wheel brake fluid circuit 30 contains a brake pedal, a vacuum booster and
 a brake master cylinder, and further contains a first brake pressure
 source which generates a brake pressure corresponding to the driver's
 brake pedal applying force, a second brake pressure source which generates
 a second pressure by a pump that is driven by a motor, and an
 electromagnetic valve for wheel brake pressure operation, which
 selectively supplies one of the first pressure and the second pressure to
 wheel brakes 51-54 as disclosed in the aforementioned Japanese Patent
 Unexamined Publication No. 8-207737.
 A brake control ECU 10 estimates a vehicle drift amount and a vehicle spin
 amount, and on the basis of these estimated values it is judged whether a
 vehicle turning is in an excessively insufficient area and if it is in the
 excessively insufficient area, a wheel brake whose wheel brake pressure
 should be increased is determined, and the second pressure is supplied to
 the determined wheel via the wheel brake fluid circuit 30. That is, a
 wheel brake pressure distribution control is performed. As this
 distribution control, there are "B-STR control" for all wheels and "2-BDC
 control" for two rear wheels. As to "B-STR control" for all wheels, there
 are additional controls, i.e., "B-STR-OS" control for suppressing an
 over-steering and "B-STR-US" control for suppressing an understeering. The
 brake control ECU 10 further implements "ABS control" (antiskid control)
 and "TRC control" (traction control) as well.
 A rotating speed of each of wheels 51-54, i.e., wheels of front-right,
 front-left, rear-right and rear-light, is detected respectively by wheel
 speed sensors 41-44, and an electric signal (wheel speed signal)
 representing each wheel speed is given to the brake control ECU 10. A
 brake SW 45 which is closed when the brake pedal is applied gives an
 electric signal representing its open (pedal is not applied: OFF)/close
 (pedal is applied: ON) condition to the brake control ECU 10.
 A yaw rate of the vehicle is detected by a yaw rate sensor A, and an
 electric signal representing the yaw rate (actual yaw rate) .gamma. is
 generated and given to the brake control ECU 10. A turning angle of
 steering wheel is detected by a front wheel steerage angle sensor
 .theta.F, and an electric signal representing a front wheel steerage angle
 .theta.f is given to the brake control ECU 10. A steerage angle of rear
 wheel is detected by a rear wheel steerage angle sensor OR, and an
 electric signal representing a rear wheel steerage angle .theta.r is given
 to the brake control ECU 10. A steering torque Tr exerted on a front wheel
 steering mechanism is detected by a torque sensor ST, and an electric
 signal representing the steering torque Tr is given to the brake control
 ECU 10. A forward/rearward acceleration gx of car body is detected by an
 acceleration sensor (GX sensor), and an electric signal representing the
 forward/rearward acceleration is given to the brake control ECU 10. A
 lateral acceleration gy of car body is detected by an acceleration sensor
 (GY sensor), and an electric signal representing the lateral acceleration
 is given to the brake control ECU 10.
 The brake control ECU 10 reads information of the above sensors, switches
 and the like and computes data used in ABS control, 2-BDC control (braking
 force distribution control for two rear wheels), TRC control and B-STR
 control (braking force distribution control for four wheels), and on the
 basis of these it is judged whether a start, a continuation or a finish of
 the above, various controls is necessary or not. And "ABS control", "2-BDC
 control", "TRC control" and/or "B-STR control" are performed depending on
 the judgment, thereby generating a wheel brake pressure operation output
 (open/close and timing of the electromagnetic valve) for these various
 controls, and the wheel brake fluid circuit 30 is operated by adjusting
 the wheel brake pressure operation output on the basis of a priority order
 of the above, various controls. That is, the electromagnetic valve is
 operated. When a steering by the braking force distribution control is
 insufficient, the brake control ECU 10 gives a steering instruction to
 4-WS control ECU 60 and further gives a command for closing a sub-throttle
 to a throttle control ECU 80, and thus a sub-throttle of engine is closed
 by a throttle driver 90, thereby decreasing an output of engine. Contents
 of these controls are ones suggested in the aforementioned Japanese Patent
 Unexamined Publication No. 8-207737.
 In the present embodiment, in the brake control ECU 10, the cruise control
 ECU 100 revives the detected signals and data of the sensors, the
 switches, etc. and the information representing the data computed by the
 ECU 10 and the determined control mode. In addition, there is a memory for
 DMA transfer and for receiving a brake steering command and a command
 value (object yaw rate) from the cruise control ECU 100, and the brake
 control ECU 10 performs either of the aforementioned "2-BDC control" and
 "B-STR control". At this time, it is checked whether there are, in a
 command receiving area of the memory for DMA transfer, a brake steering
 command and command values (lane deviation amount and curve radius) from
 the cruise control ECU 100. When they exist, an object yaw rate yawO is
 computed on the basis of the command values, and an object yaw rate of the
 wheel brake pressure distribution control, which has been generated by the
 ECU 10 for "2-BDC control" and "B-STR control", is corrected (biased) by
 an amount corresponding to the object yaw rate yawO for the brake
 steering, which has been commanded by the cruise control ECU 100, thereby
 determining the wheel brake pressure distribution in response to the
 corrected object yaw rate. By this, a brake steering intended by the
 cruise control ECU 100 is implemented by the brake control ECU 100.
 When both "2-BDC control" and "B-STR control" are unnecessary, if the brake
 steering command and the common values are received from the cruise
 control ECU 100, the brake control ECU 10 implements the wheel brake
 pressure distribution control only for this brake steering. Content of
 this is shown in FIG. 8 and described later. In the brake control ECU 10,
 the detection signals of the sensors, the switches, etc. are read at a
 predetermined cycle, a predetermined data processing is performed, and
 information representing the computed or processed data and the determined
 control mode are written in the data storage area, which is addressed to
 the cruise control ECU 100, of the memory for DMA transfer. The cruise
 control ECU 100 can read the data in the above area by using the DMA
 transfer when desired.
 The main function of the cruise control ECU 100 is a cruise control (fixed
 speed running control/inter-vehicle distance control) and a lane deviation
 control.
 In FIG. 3, the gist of the processing function of the cruise control ECU
 100 is shown. When an operating voltage is applied, the cruise control ECU
 l00 sets a built-in register, an input/output port and a built-in timer to
 their initial states, and sets an input/output interface of the ECU 10 to
 an input read connection and an output signal level when waiting (step 1).
 A timer Tc for determining a control processing cycle is started (2), a
 processing from a operation board input read (3) to "data renewal of DNA
 memory" (7) is implemented, a time-over of the timer Tc is waited (8) and
 during waiting, a state of electric circuit in the ECU 100 is checked (9),
 thereby judging whether there is an abnormality (10). If there is no
 abnormality and the time-over of the timer occurs, the timer is started
 again (2), a processing from an operation board input read (3) to "data
 renewal of DMA memory" (7) is implemented. Thus, if an electric circuit in
 the ECU 100 has no abnormality, the steps 2-10 are repeatedly implemented
 substantially at the Tc cycle.
 If a state (open, close) of switch operated by the driver is read in the
 operation board input read (3), state information and data, which are
 referenced in a later-mentioned cruise control (5) and "lane deviation
 control processing" (6), are read, by DMA transfer, from the GPS
 information ECU 190, the image processing ECU 140 and the brake control
 ECU 10 (4). That is, data in a data write area, which is addressed to the
 cruise control ECU 100, on a memory for DMA transfer within the above ECUs
 190140, 10 is written, by DMA transfer, in a memory for DMA transfer in
 the cruise control ECU 100, and is read therefrom and written in a
 reference memory (RAM) for data processing.
 Next, "cruise control processing" (5) is implemented. Here, when a fixed
 speed running instruction switch of the operation/display board 110 is
 switched from OFF to ON, a vehicle speed at that time (vehicle speed data
 computed by the brake control ECU 10) is written in an object vehicle
 speed register. Until the fixed speed running instruction switch is
 switched to OFF or a fixed speed running release condition is brought into
 existence, an open/close control for a main throttle valve of engine is
 performed via the throttle control ECU 80 in such a manner that the
 vehicle speed coincides with an object vehicle speed (data of the object
 vehicle speed register). When an inter-vehicle distance control
 instruction switch of the operation/display board 110 is switched from OFF
 to ON, until it is switched to OFF or an inter-vehicle distance control
 release condition is brought into existence, an open/close control for a
 main throttle valve of engine is performed via the throttle control ECU 80
 in such a manner that a distance between a preceding vehicle and the
 concerned vehicle, which has been detected by the image processing ECU
 140, becomes a distance corresponded to the vehicle speed. Incidentally,
 these controls are realized by repeatedly implementing "cruise control
 processing" (5) at the constant Tc cycle. Until the aforementioned fixed
 speed running control or intra-vehicle distance control is started and it
 is released, in the ECU 100, a state information ("1") representing the
 fact that it is being implemented is maintained in a cruise state
 register.
 After passing through "cruise control processing" (5), the ECU 100
 implements "lane deviation control processing" (6). Contents of this are
 shown in FIGS. 4-6. Next, contents of controls are realized by repeatedly
 implementing "lane deviation control processing" (6) at the constant cycle
 Tc.
 1. Brake steering yes/no testing (21-41 in FIG. 4):
 1A: If a deviation alarm main SW becomes ON by the driver, it is judged
 that the brake steering is yes (21 in FIG. 4), and the process proceeds to
 deviation alarm testing yes/no testing (42-45) in FIG. 5.
 1B: When the deviation alarm main SW is OFF, it is checked whether a state
 information of the cruise state register is 1 (cruise is being
 implemented) (22 in FIG. 4), and if the cruise is being implemented, it is
 judged that the brake steering is yes, and the process proceeds to the
 deviation alarm yes/no testing (42-45) in FIG. 5.
 1C: If the cruise is being implemented, data which has been read in the
 step 4 and represents a GPS position measurement valid/invalid of the GPS
 information processing ECU 190 is checked (23), and when it is valid, it
 is checked whether the read information means a cruise permission road
 (24). If this is yes, the process proceeds to the deviation alarm yes/no
 testing (42-45) in FIG. 5. Whether it is the cruise permission read or not
 is determined by the read information written in a map data base and does
 not mean whether the cruise is officially permitted or not.
 1D: When the GPS position measurement is invalid and when, even if it is
 valid, the cruise permission is not contained in the read information,
 data which has been read in the step 4 and represents a lane detection
 valid/invalid of the image processing ECU 140 is checked (25), and when
 the lane detection is valid, it is checked whether a curve radius R is
 larger than 900 m (26). And if the curve radius R is larger than 900 m,
 its continuation time is measured (26b-c). If the continuation time
 becomes longer than five minutes (26e-26g), the process proceeds to the
 deviation alarm yes/no testing (42-55) in FIG. 5.
 1E: When the lane detection is invalid and when, even if it is valid, the
 curve radius R is less than 900 m, it is checked whether a vehicle speed
 which has been read in the step 4 and computed by the brake control ECU 10
 is higher than 60 Km/h (27). If it is higher than 60 Km/h, its
 continuation time is measured (28-30). If the continuation time becomes
 longer than five minutes (31-33), it is judged that the brake steering is
 yes, and the process proceeds to the deviation alarm yes/no testing
 (42-55) in FIG. 5.
 1F: When the deviation alarm main SW is OFF, the cruise is not implemented,
 the GPS position measurement data is invalid or the cruise permission is
 not contained in the read information even if that data is valid, a road
 whose curve radius is larger than 900 m does not continue for a time
 longer than five minutes even if the lane detection is invalid and the
 vehicle speed higher than 60 Km/h does not continue for a time longer than
 five minutes, it is judged the brake steering is no, and the process does
 not proceed to the deviation alarm yes/no testing (42-45) in FIG. 5.
 When this judgment to the effect that the brake steering is not is
 concluded, there may be such a case that an alarm has been already emitted
 or further the brake steering has been started by the deviation alarm
 yes/no testing (42-45) and an output setting (61-72), which are mentioned
 later. If it is so, when the judgment to the effect that the brake
 steering is no is concluded, the alarm is released and the brake steering
 is stopped.
 1G: That is, state registers VcF, RcF, LcFT and RcFT for monitoring the
 aforementioned continuation time are first cleared (34, 35). This brings
 about stoppage of the continuation time measurement. Next, all alarm flags
 (data of state register) are made OFF (36) and the all alarms are released
 (37). Whether the brake steering is being implemented or not is checked by
 a state register CcF (38). If the brake steering is being implemented a
 brake steering stoppage is commanded to the brake control ECU 10 (39), and
 a release alarm for informing a control release is displayed on the
 operation/display board 20 and setting for energizing a buzzer under a
 release alarm mode is performed. The state register CcF is cleared (41).
 Incidentally, when this release alarm is set, a timer is started, and
 thereafter if a time-over of this timer occurs the alarm is set, a timer
 is started, and thereafter if a time-over of this timer occurs, the alarm
 is stopped.
 2. Deviation alarm yes/no testing (42-55):
 2A: Data representing a lane detection valid/invalid of the image
 processing ECU 140 is checked. If the lane detection is invalid, since
 there is no lane deviation amount data or a low reliability, the process
 proceeds to a brake steering release yes/no testing (56-60 in FIG. 6)
 jumping the deviation alarm yes/no testing.
 If the detection is valid, a lane deviation amount which is being computed
 by the image processing ECU 140 is checked (43, 45). As mentioned before,
 the lane deviation amount is one having a larger value among the left-side
 deviation amount [(Vw/2)-XL] and the right-side deviation amount
 [(Vw/2)-XR]. In the lane deviation amount data, there are contained a
 deviation amount numeric value data (including+m, -) and a direction data
 which indicates whether the deviation is left-side or right-side. If the
 lane deviation amount is larger than 0 m (vehicle's side edge exists on a
 lane partition line or protrudes therefrom), 1 (primary alarm yes) is
 written in a primary alarm flag register (44). If the lane deviation
 amount is below -0.3 m (position in which vehicle's side edge withdraws
 from the lane partition line by more than 3 m), the primary alarm flag
 register is cleared (46). By this, when the deviation amount becomes more
 than 0 m, the primary alarm flag goes ON (data of the primary alarm flag
 register=1). If the deviation amount becomes below -0.3 m, the primary
 alarm flag becomes OFF (data of the primary alarm flag register=0). If the
 deviation amount is less than 0 in but above -0.3 m, data of the primary
 alarm flag register is not changed.
 2B: If the lane deviation amount becomes more than 1 m, 1 is written in a
 secondary alarm flag register (47, 48). If the lane deviation amount is
 below 0 m, the secondary alarm flag register is cleared (49, 50). By this,
 when the deviation amount becomes more than 1 m, the secondary alarm flag
 becomes ON. If the deviation amount becomes below 0 m, the secondary alarm
 flag becomes OFF. If the deviation amount is less than 1 m but above 0 m,
 data of the secondary data of the secondary alarm flag register is not
 changed.
 2C: When data of the secondary alarm flag register is 1, if the lane
 deviation amount becomes more than 2 m, 1 is written in a tertiary alarm
 register (51-53). When data of the secondary alarm flag register is 0, if
 the deviation amount becomes below 0 m, the tertiary alarm register is
 cleared (54, 55). By this, if the lane deviation amount is increased and
 becomes more than 2 m after the secondary flag has become ON, the tertiary
 alarm flag becomes ON. If the lane deviation amount becomes below 0 m, the
 tertiary alarm flag becomes OFF. If the deviation amount is less than 2 m
 but above 0 m, data of the tertiary alarm flag register is not changed.
 3. Brake steering release yes/no testing (56-60 in FIG. 6):
 3A: It is checked whether a front wheel steering angle .theta. is an angle
 which is larger, by more than 10.degree. C., than a steering angle
 responding to the vehicle speed v and the curve radius R, i.e., a steering
 angle A1 [v, R] for performing a running of the curve radius R at the
 vehicle speed v (56, 57). If it is so, it is deemed that the driver is
 intentionally steering (e.g., in order to avoid another vehicle, obstacle,
 etc. or to change a traffic lane), and it is judged that the brake
 steering release is yes and the process proceeds to the release processing
 (34-41) subsequent to step 34. Content of this release processing is as
 described in the aforementioned 1G.
 3B: It is checked whether a steering torque of front steering mechanism is
 above 2 Nm (58).
 It if is so, it is deemed that the driver is intentionally performing a
 strong steering operation, and it is judged that the brake steering
 release is yes and the process proceeds to the release processing (34-41)
 subsequent to step 34.
 3C: State of turn signal SW of a turn signal driver 130 is checked (59). If
 it is ON (turn signal drive), it is judged that the brake steering release
 is yes and the process proceeds to the release processing (34-41)
 subsequent to step 34.
 3D: State of brake SW 45 is checked (60). If it is ON (brake pedal is
 applied), it is judged that the brake steering release is yes and the
 process proceed to the release processing (34-41) subsequent to step 34.
 When there is no driver's steering operation, the turn signal is OFF and
 the brake SW is OFF, it is judged that the brake steering release is no
 and the process proceed to a brake steering alarm output (61-72)
 subsequent to step 61.
 4. Brake steering alarm output:
 4A: When only the primary alarm flag is ON, i.e., when only the primary
 alarm flag within the primary to tertiary alarm flag register is 1, a
 primary alarm is displayed on the operation/display board 110 m, and the
 buzzer 120 is energized under a primary alarm mode 50 as to sound (61-64).
 Incidentally, this primary alarm continues until data of the primary alarm
 flag register is cleared, i.e., until the primary alarm flag becomes OFF.
 4B: When the secondary flag is ON, the alarm is changed to the secondary
 alarm. That is, the secondary alarm is displayed on the operation/display
 board 110, and the buzzer 120 is energized under a secondary mode so as to
 sound (62, 65). This secondary alarm continues until the alarm flag
 register is cleared, i.e., until the secondary alarm flag becomes OFF.
 If changed to the secondary alarm, it is checked whether the brake steering
 is being implemented (data of the register CcF is 1) (66). If the brake
 steering is not being implementation (CcF=0), the travelling direction
 correction, i.e., the brake steering is started (67). Since an actual
 brake steering (increase in wheel brake pressure and distribution control)
 is performed by the brake control ECU 100, here the cruise control ECU 100
 writes a correction command [a wheel brake pressure control instruction, a
 lane deviation amount (value containing+,- or right-side) and a curve
 radius] in a data area, which is addressed to the brake control ECU 10, of
 the memory for DMA transfer. The cruise control ECU 100 writes 1 (the
 brake steering is being implemented) in the register CcF (68). The brake
 control ECU 10 increases the wheel brake pressure and performs the
 distribution control in response to the above correction command. That is,
 the brake steering is performed. Content of this is described later by
 referring to FIG. 8.
 4C: When the tertiary alarm flag became ON, the secondary alarm flag is
 cleared (69, 70), a control stoppage alarm is displayed on the
 operation/display board 110, and the buzzer 120 is energized under a
 stoppage alarm and an alarm timer which prescribes a time of this stoppage
 alarm is started (71). Thereafter, since the tertiary flag is ON and the
 secondary alarm flag is OFF, a time-over of the alarm timer is waited (72)
 and if the time-over occurs, the process proceeds to the release
 processing (34-41) subsequent to the step 34. That is, if the tertiary
 alarm flag becomes ON (the lane deviation amount is more than 2 m), the
 stoppage alarm is firstly generated in order to stop the direction
 correction by the brake steering and thereafter the brake steering is
 stopped after the set time has elapsed. In FIG. 7, there is shown an
 outline of processing function of the brake control ECU 10. If an
 operating voltage is applied, the brake control ECU 10 sets a built-in
 register, an input/output port and a built-in timer to initial states, and
 sets an input/output interface to an input read connection and an output
 signal level during waiting (step 81).
 A timer Tb for determining a control processing cycle is started (82), a
 processing from an input read (83) "data renewal of DMA memory" (87) is
 implemented and a time-over of the timer Tb is awaited (88). During
 waiting, a state of electric circuit within the ECU 10 is checked (89) and
 it is judged whether there is an abnormality or not (90). If there is no
 abnormality and the time-over of the timer Tb occurs, the timer Tc is
 started again (82), and a processing from an input read (83) to "data
 renewal of DMA memory" (87) is implemented. Thus, if there is no
 abnormality in the electric circuit within the ECU 10, steps 82-90 are
 repeatedly implemented substantially at a Tb cycle.
 At the input read (83), if input of the operation/display board 20 and
 detection signals of the sensors 41-45. YA, .theta.F, .theta.R, ST, GX and
 GY are read, a state information referenced at a brake control processing
 (85) and "direction correction processing" (86), which are mentioned
 later, and data are read from the cruise control ECU 100 by DMA transfer
 (84). That is, data in a data write area, which is addressed to the brake
 control ECU 10, in a memory for DMA transfer within the ECU 100 is written
 in a memory for DMA transfer within the brake control ECU 10, and is read
 therefrom and written in a reference data memory (RAM) for data
 processing.
 Next, "brake control processing" (85) is implemented. Content of this is
 similar to one disclosed in the aforementioned Japanese Patent Unexamined
 Publication No. 8-207737. However, in the present embodiment, when the
 wheel brake pressure control of either of "2-BDC control" and "B-STR
 control" is performed, if data of the flag register CpF is 1 (direction
 correction demand from the ECU 10 is received), an object yaw rate yawO
 for brake steering is computed on the basis of command values (lane
 deviation amount, curve radius R) from the ECU 100. An object yaw rate of
 the wheel brake pressure distribution control, which has been formed by
 the ECU 100 for "2-BCD control" and "B-STR control", is corrected (biased)
 by an amount of the yaw rate yawO for brake steering instructed by the
 cruise control ECU 100, thereby determining a wheel brake pressure
 distribution in response to the corrected object yaw rate. By this, a
 brake steering intended by the cruise control ECU 100 is implemented by
 the brake control ECU 10. The object yaw rate yawO for brake steering is
 computed by a computation similar to that in steps 105-107 mentioned
 later.
 After passing through "brake control processing" (85), the ECU 10 proceeds
 to "direction correction processing" (86). One mode of this content is
 shown in FIG. 8. Here, the ECU 10 checks whether data of the flag register
 CpF is 1 (direction correction command from the ECU 100 has been already
 received) (101). If data of the flag register CpF is 0, it is checked
 whether there are a brake steering command and command values (lane
 deviation amount, curve radius R) from the cruise control ECU 100 (102).
 When they exist, 1 is written in the flag register CpF (103) and a
 measurement (clocking) of elapsed time T is started (104). On the basis of
 the lane deviation amount (+, -numeric value and deviation direction) and
 the curve radius R, an object yaw rate yawO of the brake steering for
 decreasing the lane deviation amount is computed (105-107).
 That is, by making reference to a direction data of the lane deviation
 amount data (+1-value data and deviation direction data), a yaw rate
 generated by a change of the vehicle travelling direction along which the
 deviation amount is decreased and a yaw rate yawS for correction in the
 same direction are determined (106A, 106B). In the present embodiment, a
 value (absolute value) of yaw rate (yawS) for correction is determined to
 .+-.2.degree./sec. Next, from the determined yaw rate yawS for correction,
 a swing yaw rate yawS.(1+sin .omega..tau.) which fluctuates within
 .+-.yawS is determined. A sum yawO=(v/R)+yawS (1+sin .omega..tau.) of a
 vehicle speed v (m/sec) and a yaw rate (v/R), i.e., a yaw rate (v/R) which
 is inferred that it is generated under the running state at present, is
 made an object yaw rate for brake steering (107). The mark .tau. is a
 clocked value (elapsed time) of clocking started in the step 104. .omega.
 is expressed as X=2.pi.f, and f is decided as f=1 Hz in the present
 embodiment.
 Next, it is checked whether data of a register ObsF is 1 ("2-BDC control"
 or "B-STR control" is being implemented) (108). When data of the register
 ObsF is 1, since the brake steering by an amount of the object yaw rate
 yawO in the aforementioned "brake control processing" (85) implemented
 just before the present processing or after the Tb is implemented as
 mentioned before, "brake control processing" (85) which is being
 implemented in this time ceases.
 When data of the register ObsF is 0, since the wheel brake pressure control
 only for brake steering is necessary, a control duty amount is computed
 (109). A computation expression is shown in a block of the step 109. In
 this computation expression, the duty (if it is a positive value) is an
 on-duty of repetition of open (ON=turning on electricity: pressure
 increase) and close (OFF=no turning on electricity: hold) of a pressure
 intensifier electromagnetic valve by which a pump discharge pressure is
 applied to the wheel brake, Kp is a proportional coefficient given to
 control error amount, yawO is an object yaw rate, Y is a detection value
 of yaw rate sensor YA, (yawO-Y) is a control error amount and Kd is a
 proportional coefficient (differential term coefficient) given to
 differential value d yawO/dt (change speed) of the object yaw rate.
 That is, by PD control, the duty for adapting the yaw rate Y of vehicle, to
 the object yaw rate yawO is computed. On the basis of a direction of the
 lane deviation and a polarity of the duty, a wheel brake to be
 pressure-increased is determined. The pressure intensifier electromagnetic
 valve connected to the determined wheel brake is subjected to ON/OFF in a
 time series pattern realizing that duty (113-116). By this, with an
 average of comparatively long time in time series, only a left-front or
 right-front wheel brake is pressure-increased. When the left-front wheel
 brake in pressure-increased, the vehicle's travelling direction changes in
 left direction and when the right-front wheel brake is pressure-increased,
 it changes in right direction, so that the lane deviation amount is
 decreased (the vehicle moves toward a lane center). Moreover, with a
 comparatively short time (instantaneous value) in time series, the
 traveling direction fluctuates in response to yawS.multidot.(1+sin
 .omega..tau.), so that a yaw rate vibration (lateral acceleration) is
 applied to the driver. This gives an abnormal feeling to the driver and
 becomes an incentive to pay attention.
 For example, if the deviation direction is right, a brake steering for
 correcting the vehicle travelling direction to left direction is
 necessary, and the brake steering to left direction can be realized by
 pressure increase (duty value plus) of the left-front wheel brake or
 pressure decrease (duty value minus) of the right-front wheel brake. In
 the present embodiment, when the brake steering is necessary, since a
 wheel brake pressure by the brake pedal application does not exist (brake
 steering during the brake pedal application is not implemented: no brake
 pressure exists in wheel brakes 51-54), a practical effect of the brake
 steering by pressure decrease of the wheel brake cannot be expected. Thus,
 when it becomes a judgment to the effect that the right-front wheel brake
 should be pressure-decreased, the left-front wheel brake is
 pressure-increased (113). When it is judged that the pressure increase of
 either of the wheel brakes is necessary, the ECU 10 drives a brake oil
 pump of the wheel brake fluid circuit 30. This is common to "brake control
 processing" (85) and "direction correction processing" (86).
 In the step 101, when it is recognized that data of the register CcF is 1
 (brake steering is being implemented), the ECU 10 checks whether the
 cruise control ECU 100 outputted a direction correction release command
 (117). If it does not exist and there are a brake steering command and
 command values (lane deviation amount, curve radius R), the brake steering
 control (105-116) subsequent to the aforementioned step 105 is
 implemented.
 If the cruise control ECU 100 outputs the direction correction release
 command, the ECU 10 clears the register CcF (118) and checks data of the
 register ObsF (119). When it is 1 ("2-BDC control" or "B-STR control" is
 being implemented), the release process ceases at this point of time. In
 this case, since the register CpF is cleared, when the wheel brake
 pressure control of either of "2-BDC control" and "B-STR control" is
 performed in "brake control processing" (85) implemented subsequently,
 data of the flag register CpF is 0 (there is no direction correction
 command from the ECU 100), so that the object yaw rate yawO for brake
 steering is not computed, and a wheel brake pressure distribution is
 determined in response to the object yaw rate itself of the wheel brake
 pressure distribution generated by the ECU 10 for "2-BDC control" and
 "B-STR control".
 When data of register ObsF is O ("2-BDC control" and "B-STR control" are
 not implemented), a pump drive is stopped and all electromagnetic valves
 are made OFF under the conditions that another "ABS control", "TRC
 control" are not implemented, and the wheel brake oil circuit 30 is
 returned to a circuit connection which exerts only an output pressure of
 brake master cylinder to the wheel brake.
 In the aforementioned embodiment, with the yaw rate Y being made a control
 amount, the wheel brake pressure distribution is controlled in such a
 manner that the yaw rate Y coincides with the object value yawO, but the
 control amount may be another physical value which becomes a value
 corresponding to the steering amount. For example, in the aforementioned
 embodiment, since the lateral acceleration sensor GY is provided, the
 lateral acceleration gy may be made a control amount. Further, it may be
 possible that the lateral acceleration is integrated to compute a lateral
 movement speed and the lateral movement speed is made a control amount. In
 any case, by making the yaw rate Y, the lateral acceleration gy and/or the
 lateral movement speed, each of which becomes a value corresponding to the
 steering amount, a control amount, a stable brake steering consistent with
 the vehicle's running state is realized.
 As mentioned above, after passing through "brake control processing (85),
 the ECU 10 proceeds to "direction correction processing (86), and another
 mode of this content is shown in FIG. 9. Here, the ECU 10 checks whether
 data of the flag register CpF is i (direction correction command from the
 Ecu 100 has been already received) (101). If data of the flag register CpF
 is O, it is checked whether there are a brake steering command and command
 values (lane deviation amount, curve radius R) from the cruise control ECU
 100. When they exist, 1 is written in the flag register CpF and, on the
 basis of the lane deviation amount (+,-numeric value and deviation
 direction) and the curve radius R, the brake steering object rate yawt for
 reducing this deviation is computed (105'-106'). In this way, rate yawt
 becomes a value which is obtained by such a calculation that 2.degree./sec
 is added to or subtracted from a yaw rate (v/R) appearing with the vehicle
 speed v(m/sec) at that time and the curve radius R of running vehicle. The
 value 2.degree./sec is yaw rate adjustment allowance for reducing the
 deviation. It is checked whether data of the register ObsF is 1 ("2-BDC
 control" or "B-STR control" is being implemented) (108). When data of the
 register ObsF is 1, since the brake steering by an amount of the object
 yaw rate yawt is implemented in such a manner as mentioned before in the
 aforementioned "brake control processing" (85) implemented just before the
 present procession or after the Tb, "brake steering" (85) which is being
 implemented at present ceases.
 When data of the register ObsF is 0, since the wheel brake pressure control
 only for brake steering is necessary, a control duty amount is computed
 (109). A computation expression is shown in a block of the step 109. In
 this computation expression, the duty (if it is a positive value) is an
 on-duty of repetition of open (ON=turning on electricity: pressure
 increase) and close (OFF=no turning on electricity: hold) of a pressure
 intensifier electromagnetic valve by which a pump discharge pressure is
 applied to the wheel brake, Kp is a proportional coefficient given to
 control error amount, yawt in an object yaw rate, Y is a detection value
 of yaw rate sensor YA, (yawt-Y) is a control error amount and Kd is a
 proportional coefficient (differential term coefficient) given to
 differential value d yawt/dt (change speed) of the object yaw rate.
 That is, by PD control, the duty for adapting the yaw rate Y of vehicle to
 the object yaw rate yawt is computed. On the basis of a direction of the
 lane deviation and a polarity of the duty, a wheel brake to be
 pressure-increased is determined. The pressure intensifier electromagnetic
 valve connected to the determined wheel brake is subjected to ON/OFF in a
 timed series pattern realizing that duty (113-116). By this, with an
 average of comparatively long time in time series, only a left-front or
 fight-front wheel brake is pressure-increased. When the left-front wheel
 brake is pressure-increased, the vehicle's travelling direction changes in
 left direction and when the right-front wheel brake is pressure-increased,
 it changes in right direction, so that the lane deviation amount is
 decreased (the vehicle moves toward a lane center).
 For example, if the deviation direction is right, a brake steering for
 correcting the vehicle travelling direction to left direction is
 necessary, and the brake steering to left direction can be realized by
 pressure increase (duty value plus) of the left-front wheel brake or
 pressure decrease (duty value minus) of the right-front wheel brake. In
 the present embodiment, when the brake steering is necessary, since a
 wheel brake pressure by the brake pedal application does not exist (brake
 steering during the brake pedal application is not implemented: no brake
 pressure exists in wheel brakes 51-54), a practical effect of the brake
 steering by pressure decrease of the wheel brake cannot be expected. Thus,
 when it becomes a judgment to the effect that the right-front wheel brake
 should be pressure-decreased, the left-front wheel brake is
 pressure-increased (113). When it is judged that the pressure increase of
 either of the wheel brakes is necessary, the ECU 10 drives a brake fluid
 pump of the wheel brake oil circuit 30. This is common to "brake control
 processing" (85) and "direction correction processing" (86).
 In the step 101, when it is recognized that data of the register CcF is 1
 (brake steering is being implemented), the ECU 10 checks whether the
 cruise control ECU 100 outputted a direction correction release command
 (117). If it does not exist and there are a brake steering command and
 command values (lane deviation amount, curve radius R), the brake steering
 control (105-116) subsequent to the aforementioned step 105 is
 implemented.
 If the cruise control ECU 100 outputs the direction correction release
 command, the ECU 10 clears the register CcF (119) and checks data of the
 register ObsF (119). When it is 1 ("2-BDC control" or "B-STR control" is
 being implemented), the release process ceases at this point of time. In
 this case, since the register CpF is cleared, when the wheel brake
 pressure control of either of "2-BDC control" and "B-STR control" is
 performed in "brake control processing" (85) implemented subsequently,
 data of the flag register CpF is 0 (there is no direction correction
 command from the ECU 100), so that the object yaw rate yawt for brake
 steering is not computed, and a wheel brake pressure distribution is
 determined in response to the object yaw rate itself of the wheel brake
 pressure distribution generated by the ECU 10 for "2-BDC control" and
 "B-STR control".
 When data of register ObsF is O ("2-BDC control" and "B-STR control" are
 not implemented), a pump drive is stopped and all electromagnetic valves
 are made OFF under the conditions that another "ABS control", "TRC
 control" are not implemented, and the wheel brake fluid circuit 30 is
 returned to a circuit connection which exerts only an output pressure of
 brake master cylinder to the wheel brake.
 In the aforementioned embodiment, if in the travelling direction correction
 yes/no testing (21-33) at lest one of the following conditions (a)-(e) is
 brought into existence, it is judged that the travelling direction
 correction is yes: (a) the deviation alarm main SW is ON, (b) the cruise
 control is being implemented, (c) the GPS position measurement data is
 effective and the cruise permission is contained in the read information,
 (d) the lane detection is effective and the curve radius of larger than
 900 m continues for longer than five minutes and (e) the vehicle speed of
 higher than 60 Km/h continues for longer than five minutes. Although these
 five conditions are all equivalent, it may be possible to adopt a testing
 logic which judges that the travelling direction correction is yes when at
 least two of these five conditions are brought into existence. One example
 of this is shown in FIG. 10.
 In the example shown in FIG. 10, under a first condition that the deviation
 alarm main SW is ON, if at least one of the following conditions (i)-(iv)
 is brought into existence, it is judged that the travelling direction
 correction is yes: (i) the cruise control is being implemented, (ii) the
 GPS position measurement data is effective and the cruise control
 permission is contained in the read information, (iii) the lane detection
 is effective and the curve radius of larger than 900 m continues for
 longer than five minutes and (iv) the vehicle speed of higher than 60 Km/h
 continues for longer than five minutes. If the deviation alarm main SW is
 switched to OFF, the travelling direction correction is released
 (21-34-41). In this example, by existence of the first condition
 (deviation alarm SW is ON) and other of the four conditions, it is judged
 that the travelling direction correction is yes. It may be possible to
 adopt another combination. For example, it is judged that the travelling
 direction correction is yes when the above five conditions are all brought
 into existence.
 In the mode shown in FIG. 10, since the travelling direction correction
 yes/no is first determined by the driver's will, such a possibility that
 whether the brake steering is performed or not performed is decided
 depending on the driver becomes high, so that a realization probability of
 the automatic detection of lane deviation and the brake steering
 corresponding to the deviation becomes low correspondingly. In case of a
 mode in which it is judged that the travelling direction correction is yes
 when all of the above five conditions are brought into existence, the
 realization probability becomes further low.
 As shown in FIG. 4, in the mode in which it is judged that the travelling
 direction correction is yes when either of the five conditions is brought
 into existence, a probability that the brake steering corresponding to the
 lane deviation is automatically performed is high, and if a reliability of
 lane deviation detection and brake steering is high, an effect of
 preventing the vehicle from drifting from the lane due to the driver's
 carelessness (e.g., sleepiness or looking away) is high. However, such a
 possibility is also high that the brake steering acting against the
 driving intended by the driver occurs. In the aforementioned embodiment, a
 difference from the driving intended by the driver is sensed by the brake
 steering release testing of the steps 56-60 and the brake steering is
 released.
 While the preferred embodiments have been described, variations thereto
 will occur to those skilled in the art within the scope of the present
 inventive concepts which are delineated by the following claims.