NAVIGATION SENSOR

Description

[0001] The present invention relates to a navigation sensor for determining a coordinate data set, which includes 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, which is configured for periodically scanning a monitoring area and includes a base unit and a scanning unit rotatably mounted on the base unit. The scanning unit has a transmitter, which is configured for transmitting signals into a monitoring area, and a receiver, which is configured for receiving signals generated by objects present in the monitoring area through the reflection of incident signals, and for converting the received signals into electrical signals.The navigation sensor also includes an evaluation unit 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.

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

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

[0004] Depending on the degrees of freedom in which the moving 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 orientation (i.e., the orientation in space in one, two, or three dimensions), and, if applicable, their temporal derivatives (i.e., linear motion and / or rotational motion in one, two, or three dimensions). The temporal derivatives can refer 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 using 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", which refers to a form of three-dimensional laser scanning), or as a radar sensor (from English "radio detection and ranging", which refers to a form of radio-based direction and distance measurement).

[0006] In a laser scanner, a laser beam or light pulse sequence periodically sweeps across a monitoring or scanning plane with the aid of a deflection unit. The transmitted signals, emitted as light, are reflected by any objects present (in particular, diffusely reflected) and, after being received by the receiver and converted into corresponding electrical signals, evaluated by the processing unit. In an object detection sensor designed as a radar sensor, the transmitted signals are emitted as focused electromagnetic waves in the radio frequency range and reflected by any objects present (in particular, diffusely reflected). After being received by the receiver and converted into corresponding electrical signals, evaluated by the processing unit.The deflection unit consists of 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 their emission by the transmitter and their reception in the receiver. 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 the transmitted light beam or radar beam is additionally pivoted around a pivot axis perpendicular to the rotation axis of the deflection unit. In an object detection sensor designed as an optoelectronic sensor, the detection of the received light signals in the receiver can be non-spatially resolved, e.g.,This can be achieved using a single photodiode, or with spatial resolution, e.g., using a line sensor or an image sensor. The transmitted light signals of an object detection sensor designed as an optoelectronic sensor can be emitted in both the visible and non-visible ranges (ultraviolet or infrared range).

[0007] An exemplary optoelectronic sensor with a base unit and a rotatably mounted scanning unit is described in EP 3 736 603 B1. For measuring object distances, one or more time-of-flight modules are arranged on the scanning unit, which are configured for distance measurement based on the time-of-flight principle. Additional optical or non-optical modules can be arranged in the scanning unit, with an inertial sensor being given as an example.

[0008] By scanning a two- or three-dimensional area using the object detection sensor, the evaluation unit can create a virtual representation of the scene or environment in which the navigation sensor or the moving object is located or moving. In real-world operation, however, localization can be disrupted temporarily due to unsuitable environmental conditions. For example, localization in corridors or tunnels can be impaired due to the lack of clarity in the surroundings. Temporary partial or total obstruction of the object detection sensor's field of view by foreign objects or environmental factors such as dust or fog can also impair or even prevent localization.

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

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

[0011] GB 2 573 090 A relates to a device for determining the position of a remote object. The device comprises a distance measuring unit for measuring the distance of the remote object and a direction measuring unit for determining the direction of this object. These units are rotatable about two axes. The direction measuring unit may include one or more direction sensors such as accelerometers, gyroscopes and / or magnetometers.

[0012] EP 4 332 495 A1 and EP 3 736 607 A1 also relate to distance sensors in which inertial sensors are provided, but which are not arranged on a rotatable scanning unit.

[0013] The object of the invention is to further develop a navigation sensor of the type mentioned above in a cost-effective manner in such a way that temporary failures or malfunctions of the object detection sensor can be compensated for or bridged.

[0014] The problem is solved by a navigation sensor with 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.

[0015] An inertial measurement unit is a combination of several motion sensors that can detect accelerations and / or angular velocities in one, two or three dimensions, whereby the accelerations and / or angular velocities are determined based on the principle of inertia.

[0016] Changes in position, such as linear movements, or changes in orientation, such as rotations, can be determined, for example, by integrating the acceleration or angular velocity signals. Such inertial measurement units (IMUs) are commercially available at very low costs, depending on their operating principle and the required precision. The combination of an object detection sensor and an initial measurement unit can compensate for failures of the object detection sensor, such as those caused by unfavorable environmental conditions like dust, rain, snow, or insufficient contrast due to inadequate lighting or a lack of contours in the scene being detected. These factors can prevent or distort the navigation sensor's ability to detect the environment.

[0017] Due to the placement of the inertial measurement unit (IMU) on the rotating scanning unit, forces or accelerations act on the navigation sensor even when the navigation sensor, or a connected moving object, is at rest, i.e., in a stationary position. The rotation of the IMU superimposes a kind of offset or idle signal on its output signals, preventing the suppression of output signals near zero. Many IMU designs incorporate such zero-point suppression as a standard feature to prevent the generation of erroneous output signals when the IMU, or a device equipped with it, is at rest and the IMU's motion sensors are only providing low signal levels near zero.With this zero-point suppression, signals that lie below defined thresholds and may also meet other criteria are filtered out. Such zero-point suppression can be easily circumvented, and in particular without modifications to the circuitry of the inertial measuring unit, by positioning the inertial measuring unit on the rotating scanning unit. Due to the rotation, the signal levels rise to a level above the thresholds. This avoids the need for costly custom-made inertial measuring units, in which such zero-point suppression is either not provided or at least deactivated.

[0018] 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 may only act on some of the individual sensor components of the inertial measuring unit. This means that the desired offset may not be achieved for all sub-sensors. If this cannot be tolerated in a particular application, the inertial measuring unit can be aligned with respect to the axis of rotation of the scanning unit so that all motion vectors that can be detected by the inertial measuring unit are at least partially aligned with 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.

[0019] According to the invention, 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 determining the corrected acceleration signals and / or angular velocity signals comprises reducing the acceleration signals and / or angular velocity signals by those signal components which are solely attributable to the rotation of the scanning unit.The aforementioned speed sensor can be, for example, a separate speed sensor or a processing unit that determines the rotational frequency of the scanning unit from a control signal for a motor driving the scanning unit. This processing 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 already known or is determined by an angular position sensor of the object detection sensor, as this serves as the basis for the optoelectronic or radar-based determination of the coordinate data set. In particular, the corrected acceleration and / or angular velocity signals only include the acceleration and / or angular velocity components that are attributable to movement of the navigation sensor.Provided that 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.

[0020] According to a further advantageous embodiment, the inertial measuring unit comprises at least one angle rate sensor and / or at least one acceleration sensor. Preferably, both sensor types are integrated in one inertial measuring unit or assembly.

[0021] According to a further advantageous embodiment, the at least one angle 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 referred to as MEMS. These MEMS are designed for mass production and are used in large quantities, for example, in mobile devices such as smartphones or tablets. Due to the resulting high production volumes, inertial measurement units in which one or more MEMS are integrated are available at very low unit costs. Often, such MEMS-based inertial measurement units—as explained above—feature 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 impact if the inertial measuring unit were arranged in a fixed position, for example on the base unit.

[0022] According to a further advantageous embodiment, the optoelectronic sensor is configured to determine the distance of a detected object present in the monitoring area, preferably according to the principle of signal time-of-flight measurement, i.e., the travel time of the light or radar wave signals. Alternatively, the object distance can also be determined according to the principle of phase shift.

[0023] 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 meaningful further combinations. It shows: Fig. 1 is a schematic representation of a navigation sensor according to an exemplary embodiment.

[0024] Fig. 1Figure 1 shows a navigation sensor 10 according to an exemplary embodiment, which is configured to determine a coordinate data set. The coordinate data set can include 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 10 in space (not shown). The navigation sensor 10 comprises an object detection sensor, for example, an optoelectronic sensor, which is configured for periodically scanning a monitoring area 30. The object detection sensor comprises 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 Figure 1. Fig. 1 not shown.

[0025] A transmitting device 22, configured for emitting transmitted light signals into the monitoring area 30, and a receiving device 24, configured for receiving received light signals generated by ambient objects 32 present in the monitoring area 30 through reflection of incident transmitted light signals, are arranged on the rotating scanning unit 14. In this embodiment, 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 single unit. Both the transmitting device 22 and the receiving device 24 can comprise one or more optics. Additional optical elements, such as deflectors, beam splitters, or filters, may also be provided.

[0026] The description in the preceding paragraph refers to an embodiment using an optoelectronic sensor.

[0027] An inertial measuring unit 20 is additionally arranged on the scanning unit 14. As indicated by the curved arrow, the inertial measuring unit 20 rotates together with the transmitter 22 and the receiver 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 transmitter 22 and receiver 24 are connected to an evaluation unit 18, which in this embodiment is arranged on the base unit 12. Signal transmission between the evaluation unit 18 and the assemblies arranged on the scanning unit 14 can be either wired or wireless.

[0028] The evaluation unit 18 is configured to determine the spatial position, orientation, and / or movements of the navigation sensor in space based on the electrical received signals generated by the receiving device 24, which represent a scene image of the monitoring area 30. If an optical determination of this coordinate data set is temporarily not possible, changes in the spatial position, orientation, and / or movement of the navigation sensor 10 can be detected by means of the inertial measuring unit 20, whereby the determination of the coordinate data set is then temporarily based solely on these acceleration or angular velocity signals detected by the inertial measuring unit 20.

[0029] To determine the corrected acceleration and / or angular velocity signals that are solely attributable to the relative motion of the navigation sensor 10 in space, those signal components that are solely due to the rotation of the inertial measuring unit 20 can be determined either computationally, 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 procedure. These rotation-related signal components can then be subtracted from the signals measured by the inertial measuring unit 20 during actual operation to determine the corrected acceleration and / or angular velocity signals. Advantageously, this correction is performed vectorially, taking into account the vector directions of the detected or generated forces or accelerations. Reference symbol list

[0030] 10Navigationssensor 12Sockeleinheit 14Abtasteinheit 18Auswerteeinheit 20inertiale Messeinheit 22Sendevorrichtung 24Empfangsvorrichtung 30Überwachungsbereich 32Umgebungsobjekt

Claims

1. A navigation sensor (10) for determining a coordinate data set which comprises 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, said navigation sensor (10) comprising an object detection sensor which is configured for periodically scanning a monitored zone (30) and which comprises a base unit (12) and a scanning unit (14) rotatably supported at the base unit (12), wherein the scanning unit (14) has a transmission device (22) which is configured for transmitting transmission signals into a monitored zone (30) and a reception device (24) which is configured for receiving reception signals, which are generated by environmental objects (32) present in the monitored zone (30) by a remission of incident transmission signals, and for converting the reception signals into electrical reception signals, and an evaluation unit (18) which is connected to the object detection sensor and which is configured to determine the coordinate data set at least on the basis of the electrical reception signals, wherein at least one inertial measurement unit (20) connected to the evaluation unit (18) is arranged at the scanning unit (14) and is configured 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 wherein 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, characterized in that the navigation sensor (10) comprises a rotational speed sensor which is connected to the evaluation unit (18) and which is configured for determining 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 corrected acceleration signals and / or angular velocity signals that are 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 due to the rotation of the scanning unit (14).

2. A navigation sensor (10) according to claim 1, characterized in that the inertial measurement unit (20) comprises at least one angular rate sensor and / or at least one acceleration sensor.

3. A navigation sensor (10) according to claim 2, characterized in that the at least one angular rate sensor and / or the at least one acceleration sensor is / are formed by at least one microelectromechanical system.

4. A navigation sensor (10) according to any one of the preceding claims, characterized in that the object detection sensor is configured as an optoelectronic sensor.

5. A navigation sensor (10) according to claim 4, characterized in that the optoelectronic sensor is configured as a laser scanner or a LIDAR sensor.

6. A navigation sensor (10) according to any one of the claims 1 to 3, characterized in that the object detection sensor is configured as a RADAR sensor.

7. A navigation sensor (10) according to any one of the preceding claims, characterized in that the object detection sensor is configured to determine the distance of a detected environmental object (32) present in the monitored zone (30), preferably in accordance with the principle of signal transit time measurement.