SAFEGUARDING THE SURROUNDING AREA OF A VEHICLE

Abstract

A safety system (10, 64) for safeguarding the surrounding area of a vehicle (50), wherein the safety system (10, 64) comprises an optoelectronic safety sensor (10) for monitoring the surrounding area, a first input (40) connectable to a first kinematic sensor (56) for determining a first speed value for the speed of the vehicle (50), and a control and evaluation unit (34, 64) configured to detect objects in the surrounding area based on sensor data of the optoelectronic safety sensor (10) and to evaluate whether or not the vehicle (50) initiates a safety reaction, taking into account the speed of the vehicle (50), further comprising an inertial measurement unit (38) for determining movement information of the vehicle (50), with the control and evaluation unit (34, 64) being configured to compare the first speed value and the movement information with each other.

Claims

1. A safety system (10, 64) for safeguarding a surrounding area of a vehicle (50), wherein the safety system (10, 64) comprises an optoelectronic safety sensor (10) for monitoring the surrounding area, a first input (40) connectable to a first kinematic sensor (56) for determining a first speed value for the speed of the vehicle (50), and a control and evaluation unit (34, 64) configured to detect objects in the surrounding area based on sensor data of the optoelectronic safety sensor (10) and to evaluate whether or not the vehicle (50) initiates a safety reaction, taking into account the speed of the vehicle (50), further comprising an inertial measurement unit (38) for determining movement information of the vehicle (50), with the control and evaluation unit (34, 64) being configured to compare the first speed value and the movement information with each other.

2. The safety system (10, 64) according to claim 1, wherein the vehicle (50) is a driverless vehicle.

3. The safety system (10, 64) according to claim 1, wherein the control and evaluation unit (34, 64) is configured to determine a second speed value for the speed of the vehicle (50) from the sensor data of the safety sensor (10) by means of optical speed estimation.

4. The safety system (10, 64) according to claim 3, wherein the control and evaluation unit (34, 64) is configured to compare the first speed value and the second speed value with each other.

5. The safety system (10, 64) according to claim 3, wherein the control and evaluation unit (34, 64) is configured to compare the second speed value and the movement information with each other.

6. The safety system (10,64) according to claim 3, wherein the control and evaluation unit (34, 64) is configured to test, in the case of a standstill value of the first speed value and the second speed value, whether the movement information is compatible with a standstill of the vehicle (50).

7. The safety system (10,64) according to claim 6, wherein, in order to be compatible with a standstill of the vehicle, the movement information has to indicate no movement if the standstill values are present over a time interval, and/or has to indicate a matching braking acceleration if the first speed value and the second speed value decrease to the standstill values.

8. The safety system (10, 64) according to claim 1, comprising a second input (42) that can be connected to a second kinematic sensor (62) for determining a second speed value for the speed of the vehicle (50).

9. The safety system (10, 64) according to claim 8, wherein at least one of the first kinematic sensor (56) and the second kinematic sensor (62) is a rotary encoder which is connected at least indirectly to a vehicle axle of the vehicle (50).

10. The safety system (10, 64) according to claim 8, wherein the control and evaluation unit (34, 64) is configured to compare the first speed value and the second speed value with each other.

11. The safety system (10, 64) according to claim 8, wherein the control and evaluation unit (34, 64) is configured to compare the second speed value and the movement information with each other.

12. The safety system (10, 64) according to claim 1, wherein the control and evaluation unit (34, 64) is configured to determine the speed of the vehicle (50) in a safe manner by means of the first kinematic sensor (56), an optical speed estimation from the sensor data of the safety sensor (10) and the movement information of the inertial measuring unit (38).

13. The safety system (10, 64) according to claim 8, wherein the control and evaluation unit (34, 64) is configured to determine the speed of the vehicle (50) in a safe manner by means of the first kinematic sensor (56), the second kinematic sensor (62) and the movement information of the inertial measuring unit (38).

14. The safety system (10, 64) according to claim 8, wherein the control and evaluation unit (34, 64) is configured to test, in the case of a standstill value of the first speed value and the second speed value, whether the movement information is compatible with a standstill of the vehicle (50).

15. The safety system (10, 64) according to claim 14, wherein, in order to be compatible with a standstill of the vehicle, the movement information has to indicate no movement if the standstill values are present over a time interval, and/or has to indicate a matching braking acceleration if the first speed value and the second speed value decrease to the standstill values.

16. The safety system (10, 64) according to claim 1, wherein at least one of the inertial measuring unit (38) and the control and evaluation unit (34) is integrated into the safety sensor (10).

17. The safety system (10, 64) according to claim 1, wherein the safety sensor (10) is configured as a safety laser scanner comprising a light transmitter (12) for transmitting a light beam (16), a rotatable deflection unit (18) for periodically deflecting the light beam (16) in the surrounding area (20), an angle measuring unit (30) for determining an angular position of the deflection unit (18), and a light receiver (26) for generating a reception signal from the light beam (22) remitted or reflected by objects in the surrounding area (20), wherein the control and evaluation unit (34) is configured to determine a light time of flight to the objects respectively scanned with the light beam based on the reception signal.

18. The safety system (10, 64) according to claim 17, wherein the control and evaluation unit (34) is configured to monitor at least one protective field (60a-c), adapted in dependence on a speed information, for object intrusion in order to determine whether or not the vehicle (50) initiates a safety reaction.

19. A method for safeguarding a surrounding area of a vehicle (50), wherein the surrounding area is monitored by an optoelectronic safety sensor (10), a first speed value for the speed of the vehicle (50) is determined by means of a first kinematic sensor (56), objects in the surrounding area are detected by means of sensor data of the safety sensor (10) and it is evaluated, taking into account the speed of the vehicle (50), whether or not the vehicle (50) initiates a safety reaction, wherein movement information of the vehicle (50) is determined by means of an inertial measuring unit (38) and the first speed value and the movement information are compared with each other.

20. The method according to claim 19, wherein the vehicle (50) is a driverless vehicle.

Description

[0030] The invention will be explained in the following also with respect to further advantages and features with reference to exemplary embodiments and the enclosed drawing. The Figures of the drawing show in:

[0031] FIG. 1 a schematic sectional view of a safety laser scanner with an inertial measuring unit;

[0032] FIG. 2 a schematic representation of a vehicle safeguarded by an optoelectronic safety sensor and safe speed determination by an encoder and optical speed estimation;

[0033] FIG. 3 a schematic representation of a vehicle similar to FIG. 2, but with speed determination by two rotary encoders;

[0034] FIG. 4 a schematic representation of a vehicle similar to FIG. 2, but with at least some of the evaluations in a safety control; and

[0035] FIG. 5 a schematic representation of a vehicle similar to FIG. 3, but with at least some of the evaluations in a safety control.

[0036] FIG. 1 shows a schematic sectional view of a safety laser scanner 10 that can be used for safeguarding a vehicle, as explained below with reference to FIGS. 2 to 5.

[0037] In the safety laser scanner 10, a light transmitter 12, for example with a laser light source in the infrared or another spectral range, generates a transmitted light beam 16 by means of transmission optics 14, which is deflected at a deflection unit 18 into a monitoring area 20. If the transmitted light beam 16 impinges on an object in the monitoring area 20, remitted light 22 returns to the safety laser scanner 10 and is detected via the deflection unit 18 and receiving optics 24 by a light receiver 26, for example a photodiode or an APD (Avalanche Photo Diode).

[0038] The deflection unit 18 in this embodiment is configured as a rotating mirror and rotates continuously driven by a motor 28. Alternatively, a measuring head including light transmitter 12 and light receiver 26 may rotate. The respective angular position of the motor 28 or the deflection unit 18 is detected by an angle measuring unit 30, for example in the form of a code disk rotating with the motor 28 and a forked photoelectric sensor.

[0039] The transmitted light beam 16 generated by the light transmitter 12 thus sweeps over the monitoring area 20 generated by the rotational movement. The design of transmission optics 14 and receiving optics 24 can be varied, for example by using a beam-shaping mirror as a deflection unit, by a different arrangement of lenses or by additional lenses. In particular, laser scanners are also known in an auto-collimation arrangement. In the embodiment shown, light transmitter 12 and light receiver 26 are accommodated on a common circuit board 32. This, too, is only an example, as separate circuit boards as well as other arrangements, for example with a mutual height offset, can be provided.

[0040] If remitted light 22 from the monitoring area 20 is received by the light receiver 26, the angular position of the deflection unit 18 measured by the angle measuring unit 30 can be used to determine the angular position of the object in the monitoring area 20. In addition, the light time of flight from transmission of a light signal to its reception after reflection at the object in the monitoring area 20 preferably is determined, for example with a pulse or phase method, and the distance of the object from the safety laser scanner 10 is determined using the speed of light.

[0041] This evaluation takes place in a control and evaluation unit 34 which is connected to the light transmitter 12, the light receiver 26, the motor 28 and the angle measuring unit 30. Thus, two-dimensional polar coordinates of all objects in monitoring area 20 are available via the angle and distance. The control and evaluation unit 34 evaluates whether a forbidden object intrudes into at least one protective field defined within monitoring area 20. If this is the case, a safety signal is output via a safety output 36 (OSSD, Output Signal Switching Device). The safety laser scanner 10 is of safe design due to measures in accordance with the standards mentioned in the introduction.

[0042] The safety laser scanner 10 furthermore includes an inertial measuring unit 38. This can be an integrated MEMS device, for example. The inertial measuring unit 38 determines the acceleration, preferably in all three spatial directions, and the angular speed with respect to all three axes. If the mounting position of the safety laser scanner 10 on a vehicle is known, fewer degrees of freedom may also be sufficient, for example for measuring the acceleration only in the direction of travel.

[0043] The safety laser scanner 10 has one input 40 or two inputs 40, 42 for connecting one or two sensors for speed measurement. The speed of a vehicle where the safety laser scanner 10 is mounted which is detected via these inputs is verified in a manner yet to be described and thus becomes safe information in the sense of the standards mentioned in the introduction using some or all of the following information: the speeds obtained via the two inputs, the acceleration information of the inertial measuring unit 38 and an optical speed estimation from the measurement data of the safety laser scanner. The protective fields can then be adapted to the current speed.

[0044] All the above-mentioned functional components of the safety laser scanner 10 are arranged in a housing 44, which has a front window 46 in the area of the light exit and light entry.

[0045] FIG. 2 shows a schematic representation of a vehicle 50, in particular an automated guided vehicle (AGV), where at least one safety laser scanner 10 is mounted to safeguard the movement paths. If the vehicle 50 is moving in one direction 52 only, a front safety laser scanner 10 is sufficient, otherwise additional safety laser scanners 10 are possible, for example on the rear, to safeguard the surrounding area when moving backwards. Instead of a safety laser scanner 10, other optoelectronic safety sensors can also be used, such as a camera, especially a 3D camera based on the time-off-light principle or a stereo camera.

[0046] The vehicle 50 moves on wheels 54, with an encoder 56 measuring the rotation rate of one of the wheels 54 to determine the speed of the vehicle 50 and transmitting this information to the safety laser scanner 10 via a connection to the safety laser scanner's corresponding input 40, 42. A vehicle controller 58 controls the vehicle 50, i.e. determines its accelerations, steering angles, speeds and the like. Preferably, the safety output 36 of the safety laser scanner 10 is connected to the vehicle control unit 58 in order to initiate a safety-related reaction of the vehicle 50 when a danger is detected.

[0047] The rotary encoder 56 and its connection to the safety laser scanner 10 and also the inputs 40, 42 are preferably single-channel or non-safe. The reliability of the speed measurement is increased by means of the inertial measuring unit 38. Thus, independent of the surroundings of the safety laser scanner 10, at least a rough estimate of the change in speed and quite an exact estimate of the change in rotation can be measured. Based on the speed measured with the rotary encoder 56 and possibly a stored movement history of the safety laser scanner 10, the control and evaluation unit 34 can calculate an expectation for the signals of the inertial measuring unit 38, i.e. its angular speed and linear acceleration in all required axes. This is compared with the actual output signal of the inertial measuring unit 38. If there is a sufficient match, the measured speed is considered to be safe. Conversely, the accelerations from the inertial measuring unit 38 can also be integrated and compared with the speed determined by the encoder 56.

[0048] The inertial measuring unit 38 preferably is only used for plausibility tests, because at least in a low-cost version, which is particularly suitable for integration in a safety laser scanner 10, it may be too inaccurate for the actual speed measurement. Therefore, the speed can preferably be measured with an additional source. An additional encoder for this purpose will be discussed later with reference to FIG. 3. However, still with reference to FIG. 2, it is also possible to optically estimate the movement of the safety laser scanner 10 from its distance measurement data. Various algorithms are conceivable, such as SLAM (Simultaneous Location and Mapping) or optical flow. A method that evaluates the measured distances from successive scans that change over time is particularly suitable. The quality of the estimation depends on the properties of the surroundings. It is usually of high accuracy, but can also become unreliable in some cases, such as in the scenarios mentioned in the introduction with long corridors or large moving objects in the field of view.

[0049] On the one hand, assuming a rigidly mounted wheel 54 and known fixed positional relationship to the installation position of the safety laser scanners 10, it is continuously tested whether the value output by the encoder is compatible with the speed calculated by the optical motion estimation. For this purpose, depending on the application, information on the current curve radius or, in the case of a rotating wheel, the steering angle may also be required from the vehicle control unit 58.

[0050] On the other hand, this speed measurement, which has already been confirmed from two sources, is also tested via the inertial measurement unit 38 as described. This means that a safe speed value can be determined with a single encoder 56, without a redundant second encoder. As long as the speed measured with the rotary encoder 56 is compatible with the signal of the inertial measuring unit 38, it is even conceivable that short-term discrepancies between the speed measured with the rotary encoder 56 and the speed optically estimated from the measurement data of the safety laser scanner or short failure phases of the optical motion estimation can be compensated.

[0051] A special case is the standstill of vehicle 50, which should be detected with particular reliability because no danger emanates from a stationary vehicle 50, and therefore all the more so from a vehicle 50 which is incorrectly detected as stationary. Two cases can arise. On the one hand, both the encoder 56 and the optical speed estimator can permanently, i.e. for at least a certain period of time, output a standstill value of zero. In that case, the inertial measuring unit 38 must not output any significant acceleration, otherwise there is an error. On the other hand, the measured or estimated speed can drop to the standstill value zero. In this case, the inertial measurement unit 38 must measure an acceleration corresponding to this change in speed or this braking period, otherwise there is an error.

[0052] After the measures described above, the control and evaluation unit 34 knows the current speed of the vehicle 50 in a safe way. Depending on this, one of several configurations of protective fields 60a-c is selected and activated, or alternatively a configuration with protective fields 60a-c is determined dynamically, taking into account the current speed and possibly further parameters such as the direction of travel. For example, at high speed a long braking distance is safeguarded with a large protective field 60a, which at low speeds could trigger unnecessary safety measures and is therefore replaced by a short protective field 60c.

[0053] If a forbidden object is detected in an active protective field 60a-c during movement of the vehicle 50, a safety signal is output to vehicle control unit 58 to prevent collisions, primarily with persons, but also with other objects such as other vehicles, which can initiate an emergency stop, a braking maneuver or an evasive maneuver or at first just reduce the speed.

[0054] A safety signal is also output if an error is detected in the speed determination, i.e. the speed measured with the encoder 56 deviates too far from the optical speed estimation and/or is not compatible with the signal of the inertial measuring unit 38. It is conceivable to tolerate such inconsistencies for a predetermined, limited period of time in order to avoid triggering an emergency stop at every jerk in motion. Furthermore, it is also conceivable to respond to a speed determination detected as faulty with worst-case assumptions instead of a safety-related reaction. This means, for example, that a maximum speed of the vehicle 50 is assumed or, as a precaution, a switchover to the most generous protective fields 60a is made. A further measure for higher availability is not to stop a vehicle 50 completely, but to limit its movement to a safe speed (creep speed).

[0055] FIG. 3 again shows a vehicle 50 whose movement is safeguarded by a safety laser scanner 10. In contrast to FIG. 2, a second encoder 62 is now provided, which is connected to an input 40, 42 of the safety laser scanner 10, so that the speed is detected redundantly with two encoders 56, 62. The second rotary encoder 62 thus functionally replaces the optical motion estimation in the embodiment described with reference to FIG. 2. It is conceivable to add the optical motion estimation, so that there is a further source for speed determination.

[0056] The mode of operation of this embodiment is analogous to that shown in FIG. 2 and is not described again. To ensure safe speed detection, it is required that the two speeds measured by the encoders 56, 62 correspond to one another within the scope of specified tolerances. In addition to the redundant detection with the two rotary encoders 56, 62, a further type of motion detection is provided by the inertial measuring unit 38 integrated in the safety laser scanner 10.

[0057] In particular, a simultaneous failure of both encoders 56, 62 can be detected by a standstill monitoring, i.e. it can be tested whether the two encoders 56, 62 are generating valid signals. This test is performed on the basis of two logical conditions: If the outputs of both encoders 56, 62 drop to the standstill value zero, the inertial measuring unit 38 must detect a corresponding acceleration. If the outputs of both encoders 56, 62 permanently, i.e. for longer than a short time interval, output the standstill value zero, the inertial measuring unit 38 must not output any significant acceleration. If one of the conditions is violated, there is an error.

[0058] FIGS. 4 and 5 again show a vehicle 50 to explain further embodiments. FIG. 4 is based on FIG. 2 with optical motion estimation and FIG. 5 on FIG. 3 with two rotary encoders 56, 62. So far it has been assumed that the inertial measuring unit 38 and the control and evaluation unit 34 are part of the safety laser scanner 10. This is also the preferred embodiment.

[0059] Alternatively, however, it is conceivable to move at least part of the control and evaluation functionality to a safety control 64 that is connected to the safety laser scanner 10 and the encoder 56 or the encoders 56, 62. A preferred distribution of tasks is that the control and evaluation unit 34 in the safety laser scanner 10 is responsible for the time-of-flight measurement and the protective field monitoring, while the safety control evaluates and tests the speeds and outputs signals to the safety laser scanner 10 for activating protective fields 60a-c adapted to the speed. It is furthermore conceivable to provide the inertial measuring unit 38 externally, i.e. outside the safety laser scanner 10, and to connect it to the safety laser scanner 10 or the safety control 64.