The invention relates to a safety system for a motor vehicle, comprising a sensing means adapted to acquire images from a surrounding of a motor vehicle, an electronic sensing control means adapted to control said sensing means and to evaluate images acquired by said sensing means in order to control a driver assisting means based on the result of said evaluation, and an electronic wiper control means adapted to control a windshield wiper of said motor vehicle.

When a sensing means, in particular a camera, is positioned behind a windshield of a motor vehicle, the sensing may be disturbed or blocked by the windshield wiper passing through the field of view of the sensing means. Due to the passing wiper, one or more image frames may be unusable for the pur ^¬ pose of, for example, detecting objects in the environment of the motor vehicle. Therefore, the functioning and reliability of the safety means is reduced.

US 7 196 305 B2 discloses an imaging system for a vehicle with a controller programmed to detect an obstructed image frame, where the obstruction corresponds to a windshield wiper of the vehicle. In response to detecting an obstructed image frame, the controller optimizes the obstructed image for display or use by a vehicle system, in particular by removing or otherwise hiding the obstructed portion of the image, for example by a frame averaging technique or an obstruction subtraction technique . The problem underlying the invention is to provide a safety system and method offering improved safety, reliability and comfort for the passenger, in particular in the case where an sensing means is positioned in the field of view of a wind ^¬ shield wiper.

The invention solves this problem by the features of the inde ^¬ pendent claims. The coordinated operation, in particular a co ^¬ ordinated timing, of the sensing means and the windshield wip ^¬ er enables to avoid disturbance or blockage of the sensing means by the passing wiper. According to the invention, the timing of the wiper movement and the timing of the sensing means are advantageously coordinated. In this manner, and in contrast to the prior art where obstructed image frames are recorded and amended later by image processing or related techniques, according to the invention the recording of (significantly) obstructed images is avoided from the start.

Preferably the sensing control means uses information about the wiper and/or the wiper control means uses information about the sensing means in order to coordinate the control of the windshield wiper and the sensing means. Advantageously this is achieved by exchanging of information between the wiper control means and the sensing control means. However, also possible for example is a one-time setting of information about the sensing means in the wiper control means, or a one ^¬ time setting of information about the wiper in the sensing control means. In this case, further communication between the wiper control means and the sensing control means may be dis ^¬ pensed with.

Preferably, the sensing control means and/or the wiper control means is adapted to change or shift the relative timing be- tween the sensing means and the wiper, or in other words to impose a time shift between the operation timing of the sens ^¬ ing means and the operation timing of the wiper.

Preferably, the wiper is controlled in coordination with in ^¬ formation provided by the sensing control means. In one em ^¬ bodiment, for example, the sensing control means provides in ^¬ formation about gaps or idle phases in the image processing to the wiper control means. The wiper control means may then ad ^¬ vantageously control the wiper to pass through the field of view of the sensing means during an image processing gap or idle phase.

In a further preferred embodiment, the speed of the windshield wiper may be controlled on the basis of information provided by the sensing means. In particular, the wiper speed may ad ^¬ vantageously be enhanced if the windshield wiper is in the field of view of said sensing means. In this embodiment, it is preferable if the wiper speed is not enhanced if the wind ^¬ shield wiper is out of the field of view of said sensing means, in order not to irritate the driver.

The invention may also be realized by controlling the timing of the sensing means in coordination with information provided by the wiper control means. In this regard, the wiper control unit advantageously provides information about at least one of the current position of the wiper, the wiper speed or fre ^¬ quency and/or an on/off state of a wiper control lever to the sensing control means. The sensing control means may then, for example, schedule a gap in the image processing to times when the wiper passes through the field of view of said sensing means, based on the information provided by the wiper control unit . A shared time reference, for example a common clock, is pref ^¬ erably established between the sensing control means and the wiper control means. In particular, the sensing control means and the wiper control means are preferably synchronized to each other on the time scale.

In one embodiment, the safety system preferably uses informa ^¬ tion from a rain sensor in said coordinated sensing and wiper control .

In the following the invention shall be illustrated on the ba ^¬ sis of preferred embodiments with reference to the accompany ^¬ ing drawings, wherein

Fig. 1 shows a schematic illustration of a safety system for a motor vehicle.

The safety system 10 is mounted in a motor vehicle and com ^¬ prises a sensing means 11 for acquiring sensing signals of a region surrounding the motor vehicle, for example a region in front of the motor vehicle. In the following, the sensing means 11 is an imaging means adapted to acquire images of a region surrounding the motor vehicle. Preferably the imaging means 11 comprises one or more imaging devices 12, in particu ^¬ lar long-range focusable or focused cameras preferably operat ^¬ ing in the visible range. Operation in the infrared range is also possible. Preferably the imaging means 11 comprises one imaging device 12 in particular forming a mono imaging means 11; alternatively a plurality of imaging devices forming a stereo imaging means can be used. The camera 12 is mounted be ^¬ hind a windshield 30, for example the front windshield of the motor vehicle. More particularly, the camera 12 may be mounted between the inner rear-view mirror of the vehicle and the windscreen 30, facing forwardly. Other arrangements are possi ^¬ ble, for example a rear-facing camera 12 may be mounted behind a rear window having a wiper, like in a station wagon. The camera frame rate preferably lies in the range between 40 Hz and 60 Hz but other frame rates are possible.

Other sensing means 11 are possible, for example sensing means based on radar or lidar sensors instead of cameras.

The imaging means 11 is controlled by an imaging electronic control unit (ECU) 20. The image data from the imaging means 11 is transmitted to the imaging ECU 20 where image and data processing is carried out by corresponding software in a proc ^¬ essing means 14 contained in said imaging ECU 20. In particu ^¬ lar, the image and data processing in the processing means 14 comprises the following functions: identification and classi ^¬ fication of possible objects surrounding the motor vehicle, such as pedestrians, other vehicles, bicyclists or large ani ^¬ mals; tracking over time the position of identified object candidates in the recorded images; calculation of a collision probability between the vehicle and a detected object; and/or activation or control of at least one driver assistance means depending on the result of the object detection and tracking processing and/or said collision probability calculation. The driver assistance means may in particular comprise a display means for displaying information relating to a detected object; warning means adapted to provide a collision warning to the driver by suitable optical, acoustical and/or haptical warning signals; one or more restraint systems such as occu ^¬ pant airbags or safety belt tensioners, pedestrian airbags, hood lifters and the like; and/or dynamic vehicle control sys ^¬ tems such as brakes or steering means. The imaging means 11 may be used for other purposes, for example detecting of road conditions, finding absence of objects or free space detec ^¬ tion, traffic sign recognition, lane detection, lane departure warning, lane keep assist, light source recognition, high beam automation, etc.

The electronic processing means 14 is preferably programmed or programmable and expediently comprises a microprocessor or mi ^¬ cro-controller. The electronic processing means 14 can preferably be realized in a digital signal processor (DSP) . The electronic processing means 14 may be connected to the imaging means 11 via a separate cable or the vehicle data bus 40. In another embodiment the ECU and the imaging device 12 can be integrated into a single box. Imaging and image processing are performed automatically and continuously during driving in re ^¬ al time.

The windshield 30 comprises at least one windshield wiper 31 driven by a wiper drive 32, in particular an electromotor. The wiper 31 is positioned such that it passes through the field of view of the camera 12 during wiping. The wiper drive 32 is controlled by a wiper electronic control unit (ECU) 33. The wiper ECU 33 preferably has information about the current po ^¬ sition of the wiper 31. This information may for example be transmitted from the wiper drive 32 to the wiper ECU 33. The current position of the wiper 31 may for example be given as the wiper angle a, see Figure 1. The wiper 31 is actuated by the driver using a wiper lever 34 which has at least two states, namely on and off, but usually has a plurality of on states corresponding to different wiper speeds or frequencies. The wiper lever 34 is usually mounted at the steering wheel 35 of the vehicle. The wiper ECU 33 preferably provides informa ^¬ tion regarding the current position a of the wiper 31, the state of the wiper lever 34, in particular regarding the on/off state of the wiper 31 and the wiper speed, to the imag ^¬ ing ECU 14, preferably via the vehicle data bus 40, usually a CAN bus, Ethernet bus or Flexray bus, or alternatively di ^¬ rectly via a corresponding signal line.

The imaging ECU 20 and the wiper ECU 33 may be integrated into one single electronic control unit (ECU) .

The safety system 10 may further comprise a rain sensor 36 which is able to detect whether or not it rains, and prefera ^¬ bly also how strong it rains. The information from the rain sensor 36 is transmitted via the vehicle data bus 40 to the wiper ECU 33 and preferably also to the imaging ECU 20.

The imaging ECU 20 provides information about the operation of the imaging means 11, in particular timing information, to the wiper ECU 33, preferably via the vehicle data bus 40, usually a CAN bus, or alternatively directly via a corresponding sig ^¬ nal line. The timing information may for example be a digital signal containing information for every image frame of the imaging means 11 whether this frame is suited for wiper passage (since it falls into an idle phase or gap of the image proc ^¬ essing) or not. In this manner, a time reference is estab ^¬ lished between the imaging ECU 20 and the wiper ECU 33. Pref ^¬ erably, the imaging ECU 20 and the wiper ECU 33 are synchro ^¬ nized to each other on the time scale, in particular by pro ^¬ viding a common clock to each ECU.

In a preferred embodiment, the wiper ECU 33 controls the wiper 31 to pass through the field of view of the imaging means 11 in a time period suited for wiper passage, as indicated by the information from the imaging ECU 20. This may be done, for ex- ample, by maintaining the chosen wiper speed but delaying the wiping action by a suitable time shift such that the wiper 31 will pass the imaging means 11 such that it causes as little blocking as possible. Knowledge about the wiper speed, motor start latency and/or friction of the wiper on the windshield 30 may be useful in this embodiment.

A gap or time window suited for passage of the wiper arm 31 may for example be the time period between the end of one im ^¬ age frame and the beginning of the next image frame. The blanking interval may be controlled by the shutter time, where the shorter the shutter time the longer may be the blanking interval. In a preferred embodiment of the camera 12, a roll ^¬ ing shutter may be used. When using such a camera 12, the shutter is open for a longer period of time with the effect that an image frame is not a snapshot, as in a camera with a global shutter. In the context of the invention, this may mean that a first row of pixels in the sensor array is exposed to light first at time 0; the last row of pixels is exposed at time X; a blanking interval with no exposed pixels starts at time X+l; and the first row of pixels are exposed for the next frame at time X+Y.

The time interval suited for wiper passage may be about 2 ms but may be extended to about 7 ms or even 10 ms . Even if the interval is too short for complete passing of the wiper through the field of view of the camera 12, at least the cen ^¬ tral portion of the field of view of the camera 12 may be passed without disturbance or blocking of the camera field of view .

If a global shutter is used in a preferred embodiment, the time all pixels are exposed to light is typically around 1 ms during daytime. This would give a blanking interval of more than 10 ms, for example about 20 ms, which would increase the chances of avoiding blocking of the camera field of view.

Alternatively or in addition, the wiper ECU 33 may control the wiper 31, based on the information provided by the imaging ECU 20 and the position information of the wiper arm 31, to enhance its speed during the time it is in the field of view of the imaging means 11, while the wiper speed is preferably not enhanced when the wiper 31 is not in the field of view of the imaging means 11. Speed enhancement means that the speed is enhanced over the speed the wiper 31 would normally have for the current position of the lever 34 and, if applicable, the current information from the rain sensor 36.

In an alternative embodiment, the wiper 31 is operated nor ^¬ mally, but the imaging ECU 20 is adapted to schedule, based on the information provided by the wiper ECU 33, gaps or idle phases in image processing to times when the wiper passes through the field of view of said imaging means.

In a preferred embodiment, information about the time of pres ^¬ ence of the wiper 31 in the camera field of view may be ob ^¬ tained by evaluating the image data 31 in a test phase. For one or several test sweeps of the wiper 31 the time of the be ^¬ ginning and end of the blocking by the wiper arm in the recorded images is measured by image processing and used in the coordinated control of the imaging means and the wiper. This information may suitably be stored in a memory of the wiper ECU 33 and/or the imaging ECU 20. Generally, the information from the rain sensor 36 may be us by the wiper ECU 33 and/or by the imaging ECU 20 in the control of the wiper 31 and/or the imaging means 11.