NAVIGATION SENSOR

Abstract

Navigation sensor for determining a coordinate data set, which comprises a spatial position and / or a location and / or a movement of the navigation sensor or of a movable object connected to the navigation sensor in space, with an object detection sensor, which is configured for periodically scanning a surveillance area and comprises a base unit and a scanning unit rotatably mounted on the base unit, wherein the scanning unit has a transmitting device, which is configured for transmitting transmission signals into a surveillance area, and a receiving device, which is configured for receiving reception signals generated by objects present in the surveillance area by remission of incident transmission signals, and for converting the received light signals into electrical reception signals, and an evaluation unit connected to the object detection sensor, which is configured toto determine the coordinate data set at least on the basis of the electrical received signals. According to the invention, at least one inertial measuring unit connected to the evaluation unit is arranged on the scanning unit, which is configured to detect accelerations and / or angular velocities of the rotating scanning unit and to transmit corresponding acceleration signals and / or angular velocity signals to the evaluation unit, and that the evaluation unit is configured to additionally determine the coordinate data set on the basis of the acceleration signals and / or angular velocity signals.

Description

[0001] The present invention relates to a navigation sensor for determining a coordinate data set comprising a spatial position and / or a location and / or a movement of the navigation sensor or of a movable object connected to the navigation sensor in space. The navigation sensor comprises an object detection sensor configured for periodically scanning a surveillance area and comprising a base unit and a scanning unit rotatably mounted on the base unit. The scanning unit has a transmitting device configured for transmitting transmission signals into a surveillance area and a receiving device configured for receiving received signals generated by objects present in the surveillance area by reflecting incident transmission signals, and for converting the received signals into electrical received signals.The navigation sensor further comprises an evaluation unit connected to the object detection sensor, which is configured to determine the coordinate data set at least on the basis of the electrical received signals.

[0002] In the field of automation technology, mobile devices such as mobile robots, self-propelled conveyors, or self-propelled vehicles are increasingly being used. These devices can move in one or more dimensions, either autonomously or under control. For the safe operation of such robots or conveyors, it is necessary that they can be localized in space.

[0003] For this purpose, generic navigation sensors are provided which can be arranged on a movable object, e.g. a robot arm, a robot platform or a conveyor device, and are designed to determine a coordinate data set which enables the localization of the navigation sensor or of the movable object connected to the navigation sensor.

[0004] Depending on the degrees of freedom in which the movable object connected to the navigation sensor can move, the coordinate data set can include the position, i.e. the location in space, in one, two or three dimensions, the attitude, i.e. the orientation in space, in one, two or three dimensions and, if applicable, also their time derivatives, i.e. a linear movement and / or a rotational movement in one, two or three dimensions. The time derivatives can relate to both the first derivative, i.e. linear velocities and / or angular velocities, and the second derivative, i.e. linear accelerations and / or angular accelerations. The coordinate data set can be represented in a suitable local or global coordinate system.

[0005] The localization of the navigation sensor or the associated moving object is primarily achieved with the help of an object detection sensor, which can be designed, for example, as an optoelectronic sensor, preferably as a laser scanner or as LIDAR (from English "Light imaging, detection and ranging", a form of three-dimensional laser scanning), or as a radar sensor (from English "radio detection and ranging", a form of radio-based direction and distance measurement).

[0006] In a laser scanner, a light beam or a sequence of light pulses generated by a laser periodically sweeps across a monitoring or scanning plane with the aid of a deflection unit. The transmitted signals emitted in the form of transmitted light are remitted by any objects present (in particular, for example, diffusely reflected) and, after being received by the receiving device and converted into corresponding electrical received signals, are evaluated by the evaluation unit. In an object detection sensor designed as a radar sensor, the transmitted signals are emitted in the form of bundled electromagnetic waves in the radio frequency range and remitted by any objects present (in particular, for example, diffusely reflected). After being received by the receiving device and converted into corresponding electrical received signals, they are evaluated by the evaluation unit.The deflection unit is formed by a base unit and a scanning unit rotating on the base unit. The position of a detected object can be determined from the angular position of the scanning unit relative to the base unit and the signal propagation time of the transmitted signals between transmission by the transmitting device and reception in the receiving device. Monitoring in multiple scanning planes or in three dimensions can be achieved, for example, by designing the object detection sensor as a multi-plane scanner with multiple scanning beams or as a LIDAR or radar system in which additional pivoting of the transmitted light beam or the radar beam is provided about a pivot axis running perpendicular to the axis of rotation of the deflection unit. In an object detection sensor designed as an optoelectronic sensor, the detection of the received light signals in the receiving device can be non-spatially resolved, e.g.The detection can be carried out using a single photodiode, or spatially resolved, e.g., using a line sensor or an image sensor. In an object detection sensor designed as an optoelectronic sensor, the transmitted light signals can be emitted in both the visible and non-visible range (ultraviolet or infrared).

[0007] An exemplary optoelectronic sensor is described in EP 3 736 603 B1.

[0008] By scanning a two- or three-dimensional spatial area using the object detection sensor, the evaluation unit can generate an image of the scene or environment in which the navigation sensor or the moving object is located or moving. However, in real-world operation, localization may be temporarily disrupted due to unsuitable environmental conditions. For example, localization in corridors or tunnels may be impaired due to a lack of clarity in the environment. Temporary partial or total obscuration of the object detection sensor's field of view by foreign objects or environmental influences such as dust or fog can also impair or even render localization impossible.

[0009] To overcome such disruptions, optical navigation or localization can be supplemented with additional navigation tools that can compensate for temporary failures or malfunctions of the optical or radar-based navigation. For example, odometers can be used, which are linked to drive wheels and can record their angle of rotation and / or angular velocity. This allows the distance traveled to be coupled during a failure of the optical navigation system, thus allowing the current location to be determined.

[0010] Furthermore, devices can also be used that can detect movements or changes in movement according to the principle of inertial navigation. However, such inertial navigation systems are often expensive and difficult to calibrate.

[0011] It is the object of the invention to develop a navigation sensor of the type mentioned at the outset in a cost-effective manner such that temporary failures or malfunctions of the object detection sensor can be compensated or bridged.

[0012] The object is achieved by a navigation sensor having the features of claim 1. According to the invention, at least one inertial measuring unit connected to the evaluation unit is arranged on the scanning unit, which is configured to detect accelerations and / or angular velocities of the rotating scanning unit and to transmit corresponding acceleration signals and / or angular velocity signals to the evaluation unit, and that the evaluation unit is configured to additionally determine the coordinate data set on the basis of the acceleration signals and / or angular velocity signals.

[0013] An inertial measurement unit is a combination of multiple motion sensors that can measure accelerations and / or angular velocities in one, two, or three dimensions. The accelerations and / or angular velocities are determined based on the principle of inertia. Changes in position, such as linear movements, or changes in attitude, such as rotations, can be determined, for example, by integrating the acceleration signals or angular velocity signals. Such inertial measurement units, also referred to as IMUs (inertial measurement units), are commercially available, sometimes at very low cost, depending on the operating principle and the desired precision.The combination of object detection sensor and initial measuring unit can compensate for failures of the object detection sensor, for example due to unfavorable environmental conditions such as dust, rain, snow or lack of contrast due to insufficient lighting or missing contours in the scene detected by the object detection sensor, which do not allow or distort the detection of the surroundings of the navigation sensor.

[0014] Due to the arrangement of the inertial measuring unit on the rotating scanning unit, forces or accelerations act during operation of the navigation sensor even when the navigation sensor or a connected moving object is at rest, i.e. in a stationary position and orientation. The rotation of the inertial measuring unit superimposes a type of offset or a rest signal on the output signals of the inertial measuring unit, which prevents the suppression of output signals close to the zero point. In many designs of inertial measuring units, such zero point suppression is provided as standard to prevent the generation of erroneous output signals when the inertial measuring unit or a device equipped with it is at rest and the motion sensors of the IMU only deliver low signal levels close to the zero point.With this zero-point suppression, signals that lie below defined thresholds and possibly also meet other criteria are filtered out. Such zero-point suppression can be easily circumvented by arranging the inertial measuring unit on the rotating scanning unit, particularly without any adjustments to the circuitry of the inertial measuring unit. Due to the rotation, the signal levels rise to a level above the thresholds. This avoids the need to resort to costly custom-made inertial measuring units, in which such zero-point suppression is not provided or at least deactivated.

[0015] Depending on the specific arrangement and orientation of the inertial measuring unit relative to the scanning device, the centrifugal forces occurring during the rotation of the scanning unit only act on a portion of the individual sensor components of the inertial measuring unit, meaning that the desired offset may not be able to be generated for all sub-sensors. If this cannot be tolerated depending on the specific application, the inertial measuring unit can be aligned with respect to the scanning unit's rotation axis in such a way that all motion vectors that can be detected by the inertial measuring unit are at least partially aligned in the direction of the centrifugal force vector, or that none of the detectable motion vectors of the inertial measuring unit are exactly perpendicular to the centrifugal force vector.

[0016] According to an advantageous embodiment, the navigation sensor comprises a rotational speed sensor connected to the evaluation unit, which is configured to determine the rotational frequency of the scanning unit relative to the base unit, wherein the evaluation unit is configured to determine acceleration signals and / or angular velocity signals corrected on the basis of the rotational frequency and to determine the coordinate data set on the basis of the corrected acceleration signals and / or angular velocity signals, wherein the determination of the corrected acceleration signals and / or angular velocity signals comprises reducing the acceleration signals and / or the angular velocity signals by those signal components which are solely attributable to the rotation of the scanning unit.The speed sensor mentioned can, for example, be a separate speed sensor or a computing unit that determines the rotational frequency of the scanning unit from a control signal for a motor driving the scanning unit. This computing unit can, for example, be implemented as a logic unit within the evaluation unit. However, the angular position of the scanning unit relative to the base unit is usually known anyway or is detected using an angular position sensor of the object detection sensor, since this serves as the basis for the optoelectronic or radar-based determination of the coordinate data set. In particular, the corrected acceleration signals and / or angular velocity signals only include the acceleration components and / or angular velocity components that are attributable to a movement of the navigation sensor.If the navigation sensor, more precisely the base unit, is at rest, the corrected acceleration signals and / or angular velocity signals have a value of zero.

[0017] According to a further advantageous embodiment, the inertial measuring unit comprises at least one angular rate sensor and / or at least one acceleration sensor. Preferably, both sensor types are integrated into an inertial measuring unit or assembly.

[0018] According to a further advantageous embodiment, the at least one angular rate sensor and / or the at least one acceleration sensor is formed by at least one micro-electro-mechanical system. Such micro-electro-mechanical systems are also abbreviated to MEMS. Such MEMS are designed for mass use and are used in large quantities, for example, in mobile devices such as smartphones or tablets. Due to the resulting high production numbers, inertial measuring units in which one or more MEMS are integrated are available at very low unit costs. As explained above, such MEMS-based inertial measuring units often feature a non-deactivatable zero-point suppression as standard.The arrangement on the rotating scanning unit now makes it possible to overcome the disadvantages associated with zero point suppression, which would have a negative effect on an assumed stationary arrangement of the inertial measuring unit, for example on the base unit.

[0019] According to a further advantageous embodiment, the optoelectronic sensor is configured to determine the distance to a detected object present in the monitoring area, preferably according to the principle of signal propagation time measurement, i.e., the propagation time of the light or radar wave signals. Alternatively, the object distance can also be determined according to the principle of phase shift.

[0020] Further advantages of the navigation sensor according to the invention and advantageous embodiments will become apparent from the following description of the drawings. The drawing shows an exemplary embodiment of the invention. The drawing, the description, and the claims contain numerous features in combination. Those skilled in the art will expediently consider these features individually and combine them into useful further combinations. It shows: Fig. 1 a schematic representation of a navigation sensor according to an embodiment.

[0021] Fig. 1shows a navigation sensor 10 according to an embodiment, which is configured to determine a coordinate data set. The coordinate data set can include a spatial position and / or a position and / or a movement of the navigation sensor or of a movable object in space (not shown) connected to the navigation sensor 10. The navigation sensor 10 includes an object detection sensor, designed, for example, as an optoelectronic sensor, which is configured to periodically scan a surveillance area 30. The object detection sensor includes a base unit 12 and a scanning unit 14 rotatably mounted on the base unit. Drive means for rotating the scanning unit 14 are shown in the schematic representation of Fig. 1 not shown.

[0022] Arranged on the rotating scanning unit 14 are a transmitting device 22, which is configured to emit transmitted light signals into the monitoring area 30, and a receiving device 24, which is configured to receive received light signals generated by surrounding objects 32 present in the monitoring area 30 by reflecting incident transmitted light signals. The transmitting device 22, for example a laser or a laser diode, and the receiving device 24, which comprises, for example, a photodiode, a line sensor, or an image sensor, are integrated into a common structural unit in the exemplary embodiment. Both the transmitting device 22 and the receiving device 24 can comprise one or more respective optical systems. In addition, further optical elements such as deflection elements, beam splitters, or filters can also be provided.

[0023] The description in the previous paragraph refers to an embodiment using an optoelectronic sensor.

[0024] An inertial measuring unit 20 is also arranged on the scanning unit 14. As indicated by the curved arrow, the inertial measuring unit 20 rotates together with the transmitting device 22 and the receiving device 24. The inertial measuring unit 20 is configured to detect accelerations and / or angular velocities of the rotating scanning unit 14. Both the inertial measuring unit 20 and the transmitting device 22 and the receiving device 24 are connected to an evaluation unit 18, which, in the exemplary embodiment, is arranged on the base unit 12. The transmission of signals between the evaluation unit 18 and the modules arranged on the scanning unit 14 can be either wired or wireless.

[0025] The evaluation unit 18 is configured to determine the spatial position, attitude, and / or movement of the navigation sensor in space based on the electrical reception signals generated by the receiving device 24, which represent a scene image of the surveillance area 30. If optical determination of this coordinate data set is temporarily not possible, changes in the spatial position, attitude, and / or movement of the navigation sensor 10 can be detected by the inertial measuring unit 20, in which case the determination of the coordinate data set is temporarily carried out solely on the basis of these acceleration or angular velocity signals detected by the inertial measuring unit 20.

[0026] In order to determine the corrected acceleration signals and / or angular velocity signals that are solely attributable to the relative movement of the navigation sensor 10 in space, those signal components that are solely attributable to the rotation of the inertial measuring unit 20 can be determined either mathematically, taking into account the distance of the inertial measuring unit 20 from the axis of rotation of the rotating scanning unit 14 and the rotational speed of the scanning unit 14, or experimentally as part of a calibration process.

[0027] These rotation-related signal components can then be subtracted from the signals measured by the inertial measurement unit 20 during real operation to determine the corrected acceleration signals and / or angular velocity signals. This correction is expediently performed vectorially, taking into account the vector directions of the detected or generated forces or accelerations. List of reference symbols

[0028] 10Navigation sensor 12Base unit 14Scanning unit 18Evaluation unit 20Inertial measuring unit 22Transmitting device 24Receiving device 30Monitoring area 32Environmental object

Claims

1. A navigation sensor (10) for determining a coordinate data set comprising a spatial position and / or a location and / or a movement of the navigation sensor (10) or of a movable object connected to the navigation sensor (10) in space, comprising an object detection sensor configured to periodically scan a surveillance area (30) and comprising a base unit (12) and a scanning unit (14) rotatably mounted on the base unit (12), wherein the scanning unit (14) has a transmitting device (22) configured to transmit transmitted signals into a surveillance area (30), and a receiving device (24) configured to receive received signals generated by surrounding objects (32) present in the surveillance area (30) by remission of incident transmitted signals, and to convert the received signals into electrical received signals,and an evaluation unit (18) connected to the object detection sensor, which is designed to determine the coordinate data set at least on the basis of the electrical received signals, , characterized by that at least one inertial measuring unit (20) connected to the evaluation unit (18) is arranged on the scanning unit (14), which is designed to detect accelerations and / or angular velocities of the rotating scanning unit (14) and to transmit corresponding acceleration signals and / or angular velocity signals to the evaluation unit (18), and that the evaluation unit (18) is configured to additionally determine the coordinate data set on the basis of the acceleration signals and / or angular velocity signals.

2. Navigation sensor (10) according to claim 1, characterized by thatthe navigation sensor (10) comprises a rotational speed sensor connected to the evaluation unit (18), which is configured to determine the rotational frequency of the scanning unit (14) relative to the base unit (12), and in that the evaluation unit (18) is configured to determine acceleration signals and / or angular velocity signals corrected on the basis of the rotational frequency and to determine the coordinate data set on the basis of the corrected acceleration signals and / or angular velocity signals, wherein the determination of the corrected acceleration signals and / or angular velocity signals comprises reducing the acceleration signals and / or the angular velocity signals by those signal components which are solely attributable to the rotation of the scanning unit (14).

3. Navigation sensor (10) according to claim 1 or 2, characterized by thatthe inertial measuring unit (20) comprises at least one angular rate sensor and / or at least one acceleration sensor.

4. Navigation sensor (10) according to claim 3, characterized by that the at least one angular rate sensor and / or the at least one acceleration sensor is formed by at least one micro-electro-mechanical system.

5. Navigation sensor (10) according to one of the preceding claims, characterized by that the object detection sensor is designed as an optoelectronic sensor.

6. Navigation sensor (10) according to claim 5, characterized by that the optoelectronic sensor is designed as a laser scanner or LIDAR sensor.

7. Navigation sensor (10) according to one of claims 1 to 4, characterized by that the object detection sensor is designed as a RADAR sensor.

8. Navigation sensor (10) according to one of the preceding claims, characterized by thatthe object detection sensor is designed to determine the distance of a detected environmental object (32) present in the monitoring area (30), preferably according to the principle of signal propagation time measurement.