WO2010001195A1

WO2010001195A1 - Sensor system for vehicle safety

Info

Publication number: WO2010001195A1
Application number: PCT/IB2008/052646
Authority: WO
Inventors: Krishnan Kutty Kongasary; Vijay Soni; Vinay Govind Vaidya
Original assignee: Kpit Cummins Infosystems Limited
Priority date: 2008-07-01
Filing date: 2008-07-01
Publication date: 2010-01-07
Also published as: EP2319031A1; CN102160099A; EP2319031A4

Abstract

An on-board system and method for real time measurement of relative velocity and distance of separation between a subject vehicle and objects in its surroundings is disclosed. The present invention provides for a system comprising a plurality of sensors that serve to detect, map positions, measure the distances and relative velocities of objects around a subject vehicle and issue warnings to the driver about impending collisions and the path to be taken during different maneuvers.

Description

SENSOR SYSTEM FOR VEHICLE SAFETY

Technical Field

[1] The present invention relates generally to safety systems used in means of vehicular transport. More particularly, the present invention relates to on-board systems and devices that function to assist the drivers of motor land vehicles in a variety of driving situations and maneuvers. The system outlined by the present invention employs a plurality of sensors that function in coordinated fashion to map relative positions of objects around the vehicle so as to warn the driver of impending collisions. Background Art

[2] Collision avoidance systems and adaptive cruise control systems find mention in the art. Various different kinds of collision warning systems have been proposed for road driven motor vehicles that warn the driver of potential collisions.

[3] US 5,529,138 describes a collision warning and avoidance system that uses a laser radar to determine the distance and relative velocity to determine a time to collision of a vehicle with an object. US 5,646,612 describes a collision warning and avoidance system employing a laser radar and infrared camera. However, laser radar systems are complicated systems that are generally expensive and tend to suffer from a narrow field of view and relatively poor lateral resolution.

[4] The present state of art provides numerous devices and methods locating, tracking and monitoring the movement of objects in relation to each other. These devices range from determining the relative trajectories of subatomic particles to the plotting the relationship between global positioning satellites to traffic collision avoidance systems, such as those described in US 6,690,296, US 6,690,295, US 6,636,752, US 6,525,674 and US 6,356,855. US 6,230107, US 5,453,740 and US 6,747,592 disclose use of Doppler effect for calculation of velocity of moving objects. However, a single system addressing multiple driving issues such as lane change, parking assist etc is not found in or anticipated by prior art. Disclosure of Invention Technical Problem

[5] Cost, complexity of sensing means is a hindrance in ease of utilization of collision warning systems in vehicles. For a collision warning system to be accurate and quick, it is essential to have a tracking device not only to locate the position of the object in the proximity, but also to monitor the movement of the object in real time without any significant delay.

[6] Common collision warning systems used in road vehicles typically employ long range sensors. These tend to have narrow field of view in the close proximity of the vehicle and hence, cannot accurately and quickly recognize changes in orientation of surrounding vehicles, which may suddenly cut into the same lane. Thus, these systems fail in the timely detection and issuing of warning about impending collisions. Also, in systems that utilize plurality of sensors of the same type, there is chance that the sensors perceive signals emitted by adjacent sensors as those reflected by target object and hence, have interference in the ranging system. The methods and devices mentioned in prior art have not been successful to completely address the issue of road safety for vehicular traffic and further, do not suggest the novel sensor system and the associated logic disclosed herein. Summary of the invention

[7] The present invention discloses the logic and description of a system and method for collision warning system comprising inter alia, a plurality of sensors. The present invention advantageously uses state of the art electronic sensors such as ultrasound, infrared and lasers. Also, the current invention provides means to adapt to the safety distance to be maintained between moving objects on the basis of their relative speeds. The present invention is unique as it provides for discretionary logic for selection and actuation of sensors to be fired and frequency of their firing on the basis of parameters including vehicle speed and maneuver to be performed.

[8] The present inventors have come up with novel solutions to overcome the problems faced in prior art. One of the solutions is a combination of sensor types that collectively map both short range and long range, thus overcoming the lack of short range mapping found in systems proposed in prior art. Also, use of plurality of sensors and their strategic positioning in the vehicle helps to eliminate 'blind spots' in the mapping of the surrounding of the vehicle.

[9] The present invention uses to its advantage a selection among sensor types instead of any single type of sensor. This minimizes dependency on any one type of sensor and also, reduces interferences due to environmental changes in functioning of individual sensors. Also, this minimizes signal interference between adjacent sensors. The system of sensors, according to the preferred embodiment of this invention, act in coordinated fashion. The present invention also provides for logic to select, fire and periodicity of re-firing a specific combination of sensors depending on maneuvers to be performed in relation to relative speed of the vehicle. Being a selection amongst various sensor types, the depth of field and field of view are optimally balanced. Description of Drawings

[10] Non limiting examples of the present invention are described herein with reference to figures attached hereto, which are listed following this paragraph. Dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and not necessarily shown to scale.

[11] Figure 1 illustrates the arrangement of the sensor system on the subject vehicle, as outlined by the best mode of performing the present invention.

[12] Figure 2.a illustrates the schematics of the working of a ranging sensor.

[13] Figure 2.b and 2.c illustrate schematics of calculation of relative distance between subject vehicle and adjacent vehicles

[14] Figure 3. a illustrates the schematics of the static safety zone around subject vehicle within which the driver can operate without risk of collision

[15] Figure 3.b illustrates the schematics of the dynamic safety zone around the subject vehicle within which the driver can operate without risk of collision

[16] Figure 4.a and 4.b illustrate schematics of calculating radius of motion upon change in steering angle

[17] Figure 5 illustrates schematics of forces acting on a vehicle when undertaking a turn

[18] Figure 6 illustrates schematics of maneuver of lane change undertaken by the driver with assistance of sensor system

[19] Figures 7 illustrates concept of safety zones around each sensor with the ranging sensor as center of the safety zone.

[20] Figure 8. a, 8.b, 8.c and 8.d illustrate limiting conditions in a lane change maneuver and the logic to maintain minimum safety distance between the vehicles during lane change.

[21] Figure 9 illustrates the graphic user interface between the driver and the sensor system.

[22] Figure 10 illustrates the door opening assist function enabled by sensor system of this invention. Best Mode

[23] Various embodiments of the present invention are described herein in the context of collision warning systems. Those of ordinary skill in the art will realize that the following detailed description of the present invention is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementation of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts.

[24] Figure 1 illustrates arrangement of ranging sensors 101, 102 , 103, 104, 105 ,106,

107, 108, 109, 110, 111 ,112 on a subject vehicle 100 surrounded by adjacent vehicles 113,114,115 and 116. In the preferred embodiment of the invention, sensors 101, 112 at front and sensors 106, 107 at back of vehicle are constantly active whereas actuation of sensors 102, 103, 104, 105, 108, 109, 110 and 111 may be activated selectively, the stimulus for such activation being stimuli of subsequent vehicle maneuver such as turning of steering wheel, switching on of turn indicator and the like.

[25] Figure 2.a illustrates the schematic of working of a ranging sensor 200. The sensor

200 consists of emitting and receiving means whereby ranging signal 202 is sent to the target 201 and after reflection, the reflected signal 203 is received by the sensor. The distance between the sensor and the target is calculated by

[26] D = (S)(T)(0.5) (1)

[27] where D is the distance between sensor 200 and target 201; S is the known speed of the ranging signal in medium, which, in the preferred embodiment of the invention, is air; and T is time between transmittal of ranging signal and receipt of signal reflected from target. The ranging signal travels from the sensor 200 to the target 201 and back to the sensor 200, thus traveling twice the distance between the sensor and the target. Hence, multiplication factor of 0.5 is introduced to compensate for this phenomenon. Calculation of relative velocity of adjacent vehicle is illustrated in Figure 2.b [28] Figures 2.b and 2.c illustrate dynamism of relative positions of adjacent vehicle 114 in relation to subject vehicle 100. Using equation (1), relative speed of adjacent vehicle 114 is given by

[29] dV = (d2-dl)/dT (2)

[30] where dV is change in relative velocity of the vehicle after lapse of time dT, dl is distance between subject vehicle 100 and adjacent vehicle 114 as calculated by equation (1), d2 is distance between subject vehicle and adjacent vehicle after lapse of time dT. 115 and 116 are ranging signals that help determine distance of vehicle 114 from vehicle 100. [31] Absolute instantaneous velocity (W) of adjacent vehicle is thus given by

[32] W = V + dV (3)

[33] where V is initial velocity of the vehicle and dV is the change in velocity after lapse of time dT.

[34] Thus by firing the ranging sensors at time interval equal to dT, where dT depends on the maximum practical speed achievable by the vehicle on the road, it is possible to estimate the speed and the distance of the adjacent vehicle from the subject vehicle. More the velocity of the subject vehicle, higher is the frequency of firing of the ranging sensors. The same logic holds true for calculating speed and distance for other adjacent vehicles.

[35] Having mapped the relative positions, relative velocities and distances from subject vehicle for adjacent vehicles, the sensor system functions to warn the driver of impending collision as and when any object moves within the safety distance of the subject vehicle, which is in turn given by [36] SD = OSD + SF (4)

[37] where SD is the safety distance to be maintained around the vehicle, OSD is the overall stopping distance of the vehicle, SF is a safety factor that depends on characteristics of vehicle and the driver. Stopping distance is different for different vehicles and depends to a large extent on the inertia of the vehicle, road grip, condition of brakes and driver's reaction time during hazardous situations. Driver response times are instrumental in deciding as to when the driver, in response to hazardous situation, applies brakes in order to stop the vehicle. In the time required for this response, the vehicle moves ahead and thus, the overall stopping distance is increased by a proportional amount. The stopping distance of the vehicle is given by

[38] s = (v²-u² )/2a (5.0)

[39] s is the stopping distance of the subject vehicle, v is the final velocity of the subject vehicle, u is the initial velocity of the subject vehicle, a is the deceleration experienced by the vehicle in coming to a halt from the initial velocity.

[40] hence, under braking conditions,

[41] since v = 0 as the vehicle comes to a stop, we have,

[42] s = u²/ 2a (5.1)

[43] Thus, the safe distance wherein an response is elicited from the driver and the vehicle is actually stopped is a simple arithmetic addition of the response time in terms of distance traveled by vehicle during response time and the distance traveled by the vehicle between application of brakes and coming to a halt. Over a large number of readings, generalization of these parameters is possible and thus, a value for safety distance be arrived at for particular vehicle and driving conditions. Thus, it is possible to chalk out a periphery of safe distance on all sides of vehicle, as illustrated in Figure 3.a

[44] Figure 3. a illustrates the concept of safety zone around the subject vehicle wherein the driver can operate without risk of collision. Assuming shape of vehicle 100 to be a rectangle with length b and width a, the length 'd' of hypotenuse is given by:

[45] d = (a² + b²)^1/2 (6)

[46] If safe distance 'SD' to be maintained on all sides of the subject vehicle while driving, then the safe zone for the subject vehicle is a rectangular area 301 with width (a + SD) and length (b + SD). However, this kind of safe zone representation is static with respect to change in steering of the subject vehicle. The dynamism of the safety zone with turning angles of the vehicle is described in detail in Figures 3.b.

[47] Figure 3.b illustrates the dynamism of safety zone 301 in accordance with the different maneuvers undertaken by the vehicle 100. When vehicle 100 turns by a particular angle theta , then the safe rectangle 301 also rotates by the same angle theta. With reference to this logic, the safety zone 301 is thereby inscribed in a circular zone 302 of dimensions such that distance of any tip of the vehicle 100 from boundary of this circular safety zone 302 is equal to the safety distance SD. The diameter of the circumscribing 'safe' circle 302 is given as

[48] D = d + 2(SD) (7)

[49] where D is diameter of the circumscribing safe circle 302, d is length of hypotenuse of the rectangle formed by the vehicle 100. The center of the circle is the same as the center of the rectangle. The radius 'R' of the 'safe circle' is hence given as

[50] R = D/2 = d/2+SD (8)

[51] where R is radius of safe circle, D is diameter of safe circle 302, d is length of hypotenuse of the rectangle shaped vehicle, SD is the safe distance to be maintained on all sides of the subject vehicle.

[52] When a vehicle negotiates a turning maneuver, at all points along the curve, there is a risk of coming within colliding distance of adjacent vehicles. Thus, it is important to calculate the motion path to be followed by vehicle when undertaking a specific maneuver. Schematics of this process is more particularly described in Figure 4. [53] Figures 4.a and 4.b illustrates the schematics of calculating radius of motion of vehicle with a particular change in steering angle to effect a turn. Figure 4. a illustrates footprint of vehicle 100 with wheels 400, 402, 403 and 404 parallel to line 401 which represents the longitudinal axis of the vehicle 100. As further illustrated in figure 4.b, when the vehicle 100 takes a turn, the front wheels change their orientation with respect to axis 401 and orient themselves parallel to a new axis 407, thus making angle 406, of value theta, between axes 401 and 407. If an imaginary line 408 is drawn perpendicular to the central axis 401 at the point where axis 401 intersects the axle of the front wheels, there is a point 409 at which it touches the axle of the rear wheels. The radius of the turn for the vehicle with turn angle theta can be approximated as a circle with center about point 409 and radius equal to the distance between the center of this circle and the point of intersection of the central axis 401 with the front axle. For any given vehicle, the distance 'da' between front and rear axles is constant. Thus radius of turn for a given steering angle theta is given by

[54] r = d / Sin(theta) (9)

[55] It is known from classical physics that when any object of mass 'm' tries to negotiate a turn of radius V, then there is a centrifugal force that acts on that object. From equation 9, we can calculate the locus taken by a vehicle due to a particular change in angle of the front wheel. Having determined the locus of driving path taken by vehicle 100 when undertaking a maneuver wherein the front wheels turn by an angle theta, we can determine the maximum velocity that can be attained by vehicle 100 when actually moving along the curved path. Calculations involved in this process are more par- ticularly described in Figure 5

[56] Figure 5 illustrates the schematics of forces acting on a vehicle 100 when it undertakes a turn 501. According to classical laws in physics, to avoid skidding of the vehicle 100, the static friction should be less than the limiting friction

[57] fs <= Fs (10)

[58] fs <= μN (11)

[59] where fs is static friction and Fs is the limiting friction of vehicle 100. Also, as there is no motion in the vertical direction, normal reaction 'N' is equal to weight of the vehicle 'Wt' which is further equitable to product of mass of vehicle 100 and coefficient of gravity. Substituting in equation 9,we get

[60] Fs <= μmg (12)

[61] In limiting condition when the car is about to skid away, maximum static friction is equal to the centripetal force on the object required for circular motion. Hence,

[62] Centripetal force = mv²/r (13)

[63] Substituting 13 in 12 and removing inequality for limiting condition, we get

[64] mv²/r = μmg (14)

[65] Thus,

[66] v = (μrg)"² (15)

[67] where μ is coefficient of static friction, r is radius of curvature, g is acceleration due to gravity. Thus the limiting velocity is independent of the mass of the vehicle. [68] Substituting equation 9 in 15, we get,

[69] v = {μdg/sin(theta)}^1/2 (16), that is,

[70] v is directly proportional to {sin(theta)} ^1/2 (17)

[71] when μ, d and g are constant.

[72] The logic of having a circular safety zone maintained in true dynamism by real time sensor activity is useful in maneuvers like lane change assist as explained in Figure 6, wherein the subject vehicle 100 has two vehicles surrounding it, namely vehicle 114 on the front and vehicle 113 to the left side. In a case where the driver intentionally has to change the lane and move to the lane of vehicle 113, the maneuver involves taking a curved path 601 to change lane and avoid collision with adjacent vehicle 113. As illustrated in Figure 6, the front tip 606 of vehicle 113 is behind front tip 607 of the vehicle 100. Thus, the ranging sensors 110 and 111 do not sense any vehicle in their respective fields of view 602 and 603. However, ranging sensors 108 and 109 can sense vehicle 113 due to their relative positioning on vehicle 100 wherein the vehicle 113 comes within ambit of their respective fields of view 604 and 605.

[73] The maneuver of lane change, as illustrated in the schematic Figure 6 involves un- dertaking of multiple curves as illustrated by path 601. In order to avoid skidding in such maneuvers, the limiting velocity and the angle for moving sideward for vehicle 100 must be calculated. These two parameters are controlled by the equation [74] v = { μrg/sin(theta) } ^m (18)

[75] where v is the limiting velocity, μ is coefficient of static friction, r is radius of curvature and g is acceleration due to gravity (9.8 m/s²). It is essential to know the path the vehicle would follow, given the constraints of the surrounding vehicles not entering the circular safety zone 302 of vehicle 100. Sensors 101 and 112 would warn the driver if the distance from the vehicle 100 to the vehicle 114 was less than the safe distance 'SD'. While changing from current lane to that of vehicle 113, the first expected point of impact would be the part of vehicle 113 most proximate to vehicle 100, which, is the front tip 606 of the vehicle 113.

[76] Figure 7 further illustrates the coordination of function among sensors in the assisting lane change maneuver by vehicle 100. The lane change assist is aimed at assisting the driver when he wants to change the lane willingly. It warns the driver of any vehicle in the blind spot zone or any approaching vehicle, when the driver wants to change lane willingly. As shown in Figure 7, for lane change assist to move left, the sensors 108, 109, 110 and 111 are actuated following the stimulus of such maneuver. The sensors 112 and 101 warn the driver when he intends to change the lane to the left, but some part of the front of the vehicle comes within safe distance of the vehicle 114. Sensors 108, 109, 110 and 111 warn the driver of vehicle available in blind spot 115, as well as any approaching vehicle. By virtue of unique placement of the sensors 108, 109, 110 and 111, it is possible to detect vehicles in the blind spot of the subject vehicle. In the schematic, assuming that sensor 111 corresponds to sensing vehicles in the blind spot. This sensor does not get any strong reflections, which means that there is no vehicle in the blind spot. However, sensors 109 & 110 get reflections from the vehicle 113, which means that there is a vehicle present to the left of the subject vehicle. By estimating speed and distance of the vehicle 113 with respect to the subject vehicle, it is possible to assist the driver to change lane intentionally.

[77] Figure 7 illustrates another novel feature of the present invention, that each sensor can be assumed as the center of an imaginary circle of radius equal to the safe distance 'SD' required between the two vehicles. Ramification of this assumption can be realized from the scenarios wherein the subject vehicle is undertaking turn to its right or to its left.

[78] Figures 8. a to 8c illustrate derivation of path followed during maneuvers involving possibility of presence of vehicle and thus collision in blind spot of subject vehicle. It is presumed that the 'safe circle' is normalized to size unity centered at coordinates (0,0). The tip of the vehicle as seen by sensor 111 is as shown in the illustration 8. a. For the subject vehicle to be safe, it is essential that the tip should lie outside the circle C. The equation of the circle C is given as : [79] x² + y² = 1 (19)

[80] Figure 8. a illustrates path of the subject vehicle when undertaking an overtaking maneuver. Here, changing lane to the left is allowed only when there is at least one sensor at the start (on the side) which does not sense any approaching vehicle. For sake of increased safety, even if sensor 110 shows an approaching vehicle, since it is not known where exactly the tip of the vehicle is in between sensors 110 and 111, it is assumed that the signal is actually from sensor 111 and not from sensor 110. The derivation of the path to be taken by the vehicle in such a scenario is as given in Figure 8.

[81] Figure 8. a illustrates circle C having center at (0,0) and radius = 1. Under limiting case, as shown in Figure 8.b, position of the tip is at (-1,0). In order to ensure that the subject vehicle is always safe, it is necessary to ensure that the distance 'd', as calculated from the center of the circle (0,0) to the left tip should be greater than 1, i.e d > 1. Also, under limiting case, the subject vehicle (in this case, circle C) should move forward and sideward (left), in such a way that the 'tip' point traverses from (-1,0) to

(-1,-1).

[82] As seen in the Figure 8.b, the locus of the center of the subject vehicle is such that the center of the subject vehicle which was at the position (0,0) before lane change moves along the locus G such that, after lane change has happened, the position of the tip now shifts to the bottom of the safe circle of the subject vehicle. The new center of the subject vehicle is now (-1,1). The equation of the locus G, the path which the subject vehicle should take is now given by the equation:

[83] (x+l)² + y² =

1 (20)

[84] This circle has center at (-1,0) and radius = 1. However, one drawback with this method is the view of the driver. As seen in the figure 8.b, the driver sees the road ahead in front of him, with the approaching vehicle to the left. However, after the lane change has happened, the driver is now looking perpendicular to the direction of the road. This can be rectified by making a modification in the locus, as shown in the figure 8. c.

[85] As seen in the figure 8.c, the locus as shown in equation 20 is followed for the first

45°. At this instant, the driver is looking at an angle 45° to the lane or pavement on the road. In order to get the driver back to normal viewing condition, the center of locus is reflected from (-1,0) to a point about the tangent to the locus at 67.5°. The new position of the center of locus is as shown in the figure 8.c. After this, the mirror image of the locus is obtained starting from the 45° position. This gives the complete locus of the subject vehicle under limiting condition. All the time, when the lane is being changed, if at any point, the sensors at the front, side or at the rear sense that any part of the surrounding vehicle is below safe distance 'SD', an alarm is generated. Thus, under no circumstance, is the safety of the driver jeopardized.

[86] Figure 8.d further illustrates schematics of maintenance of safety distance 'SD' between vehicle 100 when undertaking an overtaking maneuver around vehicle 113. As evident from schematics illustrated in figures 8. a, 8.b and 8.c, the said overtaking maneuver requires the driver to follow a path inclusive of two curves, curve 801 in anti-clockwise direction to steer around vehicle 113 and curve 802, in clockwise direction, to orient vehicle 100 to the lane of vehicle 113. Safety distance is to be maintained while maneuvering through the curves 801 and 802. 'Y' is mirror image of center O' of subject vehicle having mirror plane 805. 'p' and 'c' are points of intersection of circles with radius equal to unity and centers o and Y respectively. It would be obvious that the paths 801 and 802 would lie along the periphery of circles 803 and 804. . After transition from path 801 to 802, it is evident that path 802 is within safety distance SD of vehicle 100. This places the subject vehicle at risk of collision. To ensure that safety distance is maintained between subject vehicle and adjacent vehicle along the curve 802, an offset 'ab' must be provided. The calculation of this offset is given by following equations

[87] In triangle opY,

[88] x = oa + ab + bY (21)

[89] where x is distance between o and Y, a and b are points of intersection of circles 801 and 802 with straight line joining points o and Y.

[90] From classical geometry, it is clear that line oY is bisector of angle poc of rhombus pocY. Thus, measure of angle poY is 1/2 of angle poc, which is 45°. Hence, measure of angle poY is 22.5°. As triangle poY is isosceles, measure of angle pYo is also 22.5° and thus, measure of angle opOl is (180°-45°) = 135°.

[91] using sine rule,

[92] l/sin(22.5°) = x/sin(135°

) (22)

[93] thus,

[94] x = sin(135°)/sin(22.5°) = cos(45°)/sin(22.5°) = 0.7071/0.38268 =

1.847755 (23)

[95] It would be appreciated that oa = bY; and oa + ab = ab+bY = 1 = radius of circle 801 or 802. [96] Thus x =1.84775 = 1+bY (24) [97] Thus bY = oa = 0.84775 (25)

[98] Thus ab = 1.84775-2(0.84775) = 0.15225 (26)

[99] For figure 8.c, the value of 1' for safe distance is assuming that this value 'ab' =

0.15225 is taken into account. In other words, 1 is the normalized value of 'SD + 0.15225'.

[100] Thus, the present inventors have proposed a vehicle safety system comprising of plurality of sensors which differs from prior art in the logic presented for maintaining the safety distance in adaptation to changing maneuvers of subject vehicle. Industrial Applicability

[101] The present invention is capable of wide applicability in industry and considering its adaptability towards various driving maneuvers and circumstances, it may be used in various modes such as lane change assist system, collision warning system, parking assist system, adaptive cruise control system, parallel parking assist system and door opening warning systems. Adaptability towards different vehicles may be enabled by deciding optimal placement of sensors taking into consideration factors including size of the subject vehicle, shape of the subject vehicle, minimum size of the surrounding vehicle that should be detected, range of the sensors used and speed of the subject vehicle.

[102] Figure 9 illustrates a console depicting a user interface 901 for the sensor system proposed by the present invention, It includes a graphic display 902 for depiction of positions, relative velocities and distances of adjacent vehicles 903, 904, 905 and 906 from subject vehicle 100. In case of any object in within the safe limits of the vehicle, warnings are issued, in this case, by lighting of warning lamps in the adjacent panel 908.

[103] Figure 10 illustrates the door opening assist function enabled by sensor system of this invention. In a scenario where vehicle 100 is parked between two parked vehicles 113 and 116. If the lateral distance between the vehicle 100 and vehicle 113 and / or vehicle 100 and vehicle 116 is less than the distance required to open the door, a warning signal is activated. Also, this warning is issued in case where there is an obstruction in the path of the door. The obstruction may be an external object or in some cases, body part of the individual boarding or alighting from the vehicle. This function is enabled by ranging sensors 102, 103, 104, 105, 108, 109, 110 and 111 are used to sense obstacles during door opening. The safety zones in this case, would be areas under the safety arcs 1004, 1005, 1006 and 1007 as made by opening of the doors 1000, 1001, 1002 and 1003 respectively. Radius of circle of which the safety arc is a part, would be length of the respective doors. Unlocking of doors can be utilized as stimulus for selective actuation of sensors among the group of 102, 103, 104, 105, 108, 109, 110 and 111.

Claims

[1] An integrated collision warning system to warn driver of impending collisions comprising of: plurality of sensing means mounted on the periphery of a vehicle; receiving means capable of receiving signals from sensing means; calculating means capable of using signals from sensing means in calculation of distance of separation and relative speed of surrounding objects in context of position and speed of subject vehicle; logic means capable of deciding whether an object is within defined safety zone of a sensing means; and warning means to issue warnings of impending collision to driver of subject vehicle. [2] The integrated system according to claim 1, wherein the sensing means comprise the selection of atleast one among the group including ultrasound sensors, infrared sensors and laser sensors. [3] The integrated system according to claim 1, wherein the receiving, calculating and logic means are contained in a central unit comprising: processor means for processing signals received from sensing means; memory means for storage of logic data; executable code for calculation of relative speed and distance of proximity of object from subject vehicle. [4] The integrated system according to claim 1, wherein the warning means include selection of atleast one among the group including warning lamps and sounds. [5] A method of providing warnings of impending collisions of a subject vehicle with objects in its surroundings comprising the steps of: using atleast one sensing means to sense the presence of an object in surroundings of subject vehicle whether stationary or moving; determining the distance of separation between the subject vehicle and object in proximity of subject vehicle; determining the relative speed of the object in proximity of the subject vehicle; determining the speed of reduction in distance of proximity between the object and subject vehicle, the distance approaching a defined zone around each sensing means; determining path of vehicle when negotiating a overtaking maneuver; and generating warning to the driver of the subject vehicle of impending collision upon distance of proximity of object being less than defined safety zone around each sensing means; [6] The method according to claim 5, wherein the objects include but are not limited to vehicles, persons or inanimate obstructions; [7] The method according to claim 5, wherein determination of distance of separation between object and subject of vehicle comprises the steps of: firing of sensor to emit signal; receiving signal reflected from target object, measurement of time gap between sending and receipt of signal by sensor; multiplying time measured by speed of signal; and halving result of multiplication of time required and speed of signal [8] The method according to claim 5, wherein calculation of velocity of object relative to subject vehicle comprises steps of: taking consecutive measurements of distance of separation of object from subject vehicle; subtracting subsequent measurement of distance of separation from precedent measurement; multiplying difference between consecutive measurements of distance of separation by amount of time between these consecutive measurements. [9] The method according to claim 5, wherein calculation of instantaneous speed of object comprises addition of relative velocity of object to original velocity of subject vehicle. [10] The method according to claim 5, wherein safety zone comprises a circular area with individual sensor as center within which a driver can safely operate the vehicle without the risk of collision; the process of determination of radius of safety zone around each sensor comprising: measuring speed of vehicle; providing driver the signal to apply brakes; measuring response time of driver from presentation of signal to apply brakes to actual application of brakes; measuring distance for vehicle to come to complete standstill; and adding distances for response of driver and stopping distance for vehicle.