Ground-based robot and navigation method

Abstract

In one embodiment, the ground-based robot comprises: - a casing (2); - a measurement arrangement (3) comprising a self-mixing interferometry, SMI sensor, (31, 32, 33, 34) and configured to emit a plurality of measurement rays (r) for determining radial speed and distance information by means of self-mixing interferometry; - a motor (4); and - a navigation unit (5), wherein the navigation unit (5) is configured to receive radial speed and distance information from the SMI sensor (31, 32, 33, 34), to analyze the radial speed and distance information and to output control signals to the motor (4) in order to move the robot (1).

Description

[0001]2023PF01303 September 4, 2024 P2023,1224 WO N - 1 - Description GROUND-BASED ROBOT AND NAVIGATION METHOD A ground-based robot is provided. A method for navigating such a ground-based robot is also provided. Documents WO 2023 / 156380 A1 and WO 2023 / 094402 A1 disclose self-mixing interferometry sensors. Document Dominik Kellner et al., “Instantaneous Ego-Motion Estimation using Doppler Radar” in Proceedings - IEEE International Conference on Robotics and Automation, October 2013, DOI: 10.1109 / ITSC.2013.6728341, discusses using Doppler radars. Document Javier Moreno et al., “Experimental Characterization of the Twin-Eye Laser Mouse Sensor" in Journal of Sensors, Volume 2016, Article ID 4281397, DOI: 10.1155 / 2016 / 4281397, refers to optical sensors for motion measurement. An object to be solved is to provide a ground-based robot that can efficiently be navigated. This object is achieved, inter alia, by a ground-based robot and by a method as defined in the independent patent claims. Exemplary further developments constitute the subject-matter of the dependent patent claims. According to at least one embodiment, the robot is ground- based. This means, for example, that the robot is bound to the ground and, thus, cannot fly, for example. It is possible that in the intended use the robot always touches the ground. 2023PF01303 September 4, 2024 P2023,1224 WO N - 2 - However, the term “ground-based” may alternatively or additionally refer to a near-ground vehicle using at least one of an aerodynamical ground effect or electromagnetic levitation or air-cushion or the like. Thus, the robot is configured for two-dimensional movement relative to the ground, and may not or not significantly perform intentional height changes above ground. For example, the robot is configured for heights of no more than 50% of a largest lateral extent of the robot, seen in top view. According to at least one embodiment, the robot comprises a casing. For example, by means of the casing an interior of the robot is protected. The casing may comprise a metal and / or plastics. According to at least one embodiment, the robot comprises one or a plurality of self-mixing interferometry sensors, SMI sensors for short. Hence, the SMI sensors are optical sensors. The term “optical” includes radiation that can be handled by optical components like lenses and is not limited to the visible spectral range, but may include near- ultraviolet radiation and / or near-infrared radiation. For example, the SMI sensors may work with radiation anywhere in the spectral range from 0.3 µm to 2 µm. The one or the plurality of SMI sensors can be regarded as a measurement arrangement configured to emit a plurality of measurement rays for determining radial speed and distance information by means of self-mixing interferometry. According to at least one embodiment, the SMI sensors are arranged at the casing. That is, the SMI sensors can be located within the casing or can be applied on a hull of the casing. Especially, the SMI sensors are mounted within the 2023PF01303 September 4, 2024 P2023,1224 WO N - 3 - casing but can emit and receive relevant radiation from outside the robot, possibly through windows or cut-outs in the casing. According to at least one embodiment, the robot comprises one or a plurality of motors. By means of the at least one motor, the robot can move relative to the ground. The at least one motor can be part of a motor system or can constitute a motor system. According to at least one embodiment, the robot comprises one or a plurality of navigation units. The at least one navigation unit is configured to receive radial speed and distance information from the SMI sensors. The radial speed and distance information includes information either about the radial speed or about the angular speed, or the radial speed and distance information includes information about both the radial speed and the angular speed. Said information may be coded by means of electric or electromagnetic signals. The signals may be analog signals to be processed in the navigation unit or the signals may already be digital signals representing a speed and / or a distance measured by the respective SMI sensor. The radial speed may be a speed along at least one beam emitted by the respective SMI sensor, and the distance may be a distance to the ground or to an obstacle along said at least one beam. According to at least one embodiment, the at least one navigation unit is configured to analyze the radial speed and distance information. For example, the at least one navigation unit is configured to calculate a linear velocity and / or an angular velocity of the robot based on the radial 2023PF01303 September 4, 2024 P2023,1224 WO N - 4 - speed and distance information. That is, the navigation unit processes all the speeds and / or distances measured by means of the SMI sensors to the linear velocity and the angular velocity of the robot. The linear velocity may be a two- dimensional vector, at a given time, and the angular velocity may be a scalar value, at a given time. A temporal resolution of the navigation unit may be better than a quotient of a length of the robot along the velocity vector and of an actual or maximum speed of the robot, or may be better than three times or better than ten times said quotient. Thus, the temporal resolution may be significantly better than the time span the robot needs to move along its length. According to at least one embodiment, the at least one navigation unit is configured to output control signals to the motor in order to move the robot. For this purpose, the navigation unit may also consider further signals, like a map of the region the robot moves through or like a destination of the robot to go to or like a path the robot has already travelled. Hence, the navigation unit may use the radial speed and distance information as well as information about an intention and / or task of the robot. In at least one embodiment, the ground-based robot comprises: - a casing; - a measurement arrangement comprising a self-mixing interferometry, SMI sensor, and configured to emit a plurality of measurement rays for determining radial speed and distance information by means of self-mixing interferometry; - a motor; and - a navigation unit, wherein the navigation unit is configured to receive radial 2023PF01303 September 4, 2024 P2023,1224 WO N - 5 - speed and distance information from the SMI sensors, to analyze the radial speed and distance information and to output control signals to the motor in order to move the robot. Thus, herein a method for robot navigation using self-mixing Interferometry, SMI, sensors is described. For example, the method can be used in robots, like vacuum cleaner robots or warehouse robots or lawn mower robots, as well as in drones. With the method, odometry, mapping, simultaneous localization and mapping, SLAM for short, and / or navigation can be performed. With this method, direct linear and angular velocity measurements are possible that result in a simple and robust solution for robot navigation, in particular for odometry but also possibly for mapping and obstacles detection. There are some possible solutions to track ground-based robots. Some solutions rely on external installation like GPS, ultra-wideband beacons or visual tracking with external cameras. These solutions are usually complex to deploy, might suffer from coverage issues or might have a limited resolution. Another approach is ego-motion or odometry that uses data from "inside-out" motion sensors on the mobile device itself to estimate changes in position over time. The measure of the velocity of the moving robot is critical for such an application. To estimate the velocity of ground-based robots, there are several approaches based on wheel encoders, optical flow measurements, inertial measurement units or VIO, but these methods lack robustness, can be complex and / or computationally intensive. 2023PF01303 September 4, 2024 P2023,1224 WO N - 6 - SMI sensors can reliably measure the relative radial velocity between a mobile device and a target. Herein, it is proposed to use SMI sensors pointed toward the ground to estimate the linear and angular velocities of a mobile robot. With the method and the robot described herein, it is possible to deal with baselines between multiple SMI sensors. Optionally, measurement of the angular velocity in addition to the linear velocity is enabled, especially with optical sensors only. Herein, also a suitable arrangement of the SMI sensor for both linear and angular velocities measurement is proposed but also for obstacle detection and room mapping. Thus, several SMI sensors can be placed on a mobile robot or on a vehicle. The SMI sensors point from a side of the robot toward the floor with a given angle, for example, of 45°, and in different directions. Each SMI sensor can measure the radial velocity in the direction of its ray. By combining the measurements from multiple sensors and by leveraging the orientation and the baselines between the sensors, the linear and angular velocities can be determined, like estimated. The determined velocities can then be directly integrated to estimate the movement of the device. The distance measurements from the SMI sensors can be used for obstacle detection, and optional SMI sensors pointing horizontally can also be used for localization and mapping. For example, an SMI sensor comprises a laser device, like a vertical cavity surface emitting laser, VCSEL for short, configured to emit a transmit signal towards an object, a frequency of the transmit signal being variable by varying a current injected in the laser device, a laser driving system for driving the laser device, and a receiver configured to 2023PF01303 September 4, 2024 P2023,1224 WO N - 7 - receive an input signal, for example, a photodiode or the VCSEL itself, the input signal being based on a superposition of the transmit signal and a reflected signal reflected by the object. The laser driving system is configured to supply the current having an intensity varying in accordance with multiple different modulation patterns at different timings, the modulation patterns representing a frequency change of the transmit signal with time or in accordance with a combination at different timings of a changing frequency with time and a constant frequency. A speed and a distance between the object and the receiver are configured to be determined from the input signal. The method described herein can be used, inter alia, to track the movement of a mobile robot, to detect obstacles and for localization and mapping. The advantages are the following, for example: - Simplicity: Such a system is simple and the associated computations is much simpler than, for example, for visual odometry. - Robustness: Since the SMI sensors are pointed toward the floor, the surfaces targeted by each sensor will not vary much and will stay at a distance approximately constant. The system can thus be able to track the movement in all conditions. Visual odometry on the contrary rely on the textures of the environment and does not work well against flat surfaces, for example. - Obstacle detection / localization and mapping: The proposed sensors can measure velocities but also distances. Therefore, the SMI sensors can also be used to detect obstacles and for localization and mapping. 2023PF01303 September 4, 2024 P2023,1224 WO N - 8 - According to at least one embodiment, the robot further comprises at least one of a cleaning unit, a transport unit, a cutting unit or a display unit. In case of comprising one or a plurality of cleaning units, the robot can be a cleaner, like a vacuum cleaner robot. In case of comprising one or a plurality of transport units, the robot may be a warehouse robot or a service robot. In case of comprising one or a plurality of display units, the robot can be a service robot or an information providing robot, for example. In case of comprising one or a plurality of cutting units, the robot can be a robot lawnmower or an agricultural robot, for example. According to at least one embodiment, the at least one motor is configured to linearly and / or to angularly move the robot. In this context, “linearly” can also be referred to as “laterally” or “transversally”, that is, parallel to the ground. The term “angularly” may mean in this context a rotation relative to an axis of rotation of the robot. The motor or the motor system may comprise or may be an electric motor supplied with energy by means of at least one of a battery or an accumulator or an electro-chemical cell or also a combustion engine included in the robot. For example, the motor or the motor system is configured to drive one or a plurality of wheels. There may be at least one gearbox. According to at least one embodiment, only the SMI sensors are configured to provide the radial speed and distance information. Hence, it is possible that the navigation unit together with the SMI sensors only is configured to determine a linear velocity and an angular velocity of the robot. Thus, for this purpose there are only the SMI sensors and no other sensors. 2023PF01303 September 4, 2024 P2023,1224 WO N - 9 - According to at least one embodiment, the robot also comprises one or a plurality of further sensors. For example, the at least one further sensor is an inertial measurement unit, IMU, sensor. The IMU sensor may be a semiconductor sensor based, for example, on silicon technology. According to at least one embodiment, the SMI sensors together with the at least one further sensor and the navigation unit are configured to determine the linear velocity and the angular velocity of the robot. Hence, in this case, for example, the SMI sensors are to provide information on the linear velocity while the at least one further sensor is to provide information on the angular velocity. In this case, the linear velocity can be determined based on the optical sensors while the angular velocity is determined based on the further sensor, like the IMU. According to at least one embodiment, each one of the SMI sensors is configured to emit one or a plurality of measurement rays for determining the radial speed and distance information. It is possible that there are different kinds of SMI sensors in the robot wherein the different kinds of SMI sensors may differ in the number of rays emitted by the respective kind of sensor. Otherwise, all the SMI sensors may have the same number of rays emitted. Each measurement ray may be emitted in a distinct direction different from some or from all other directions of measurement rays. Hence, the rays are not congruent and possibly there are no measurement rays running in parallel with each other; there can be measurement rays running 2023PF01303 September 4, 2024 P2023,1224 WO N - 10 - antiparallel with each other. It is however possible that at least two of the measurement rays cross each other. Each measurement ray may be represented by a three- dimensional vector starting from a distinct point in space. Thus, there are no two identical vectors starting from the same point in space, and there may be no two identical vectors at all. According to at least one embodiment, all of the SMI sensors together are configured to emit at least two or at least three or at least six of the measurement rays. Alternatively or additionally, the number of measurement rays is at most 100 or is at most 60 or is at most 20 or is at most twelve. According to at least one embodiment, one or some or all of of the SMI sensors is / are configured to emit two or more than two of the measurement rays. Especially in case of two measurement rays per SMI sensor, these rays are emitted along a first angle and along a second angle different from the first angle, the first angle and the second angle being defined relative to said SMI sensor. These angles may accordingly also be referred to as directions starting from the respective one SMI sensor. According to at least one embodiment, the measurement rays of a specific one of the SMI sensors are located in a common plane. In other words, all the measurement rays emitted by a specific one of the SMI sensors may be placed in one common plane. It is possible that for each one of the SMI sensors emitting at least two of the measurement rays there is such a common plane. It is further possible that all common planes 2023PF01303 September 4, 2024 P2023,1224 WO N - 11 - of all SMI sensors differ from one another in pairs so that there are no parallel and / or congruent common planes. According to at least one embodiment, a difference between the first angle and the second angle of the at least one respective SMI sensor is at least 30° or is at least 45°. Alternatively or additionally, said difference is at most 180° or is at most 130° or is at most 80°. For example, said difference is between 50° and 70°. This applies especially seen in top view of the robot and / or in projection onto the ground which can be plane and horizontal. According to at least one embodiment, one or some or all of the common planes has / have a vertical angle of at most -30° or of at most -15° or of at most -5°. Alternatively or additionally, said vertical angle is at least -80° or is at least -60° or is at least -50°. For example, said vertical angle is between 45° and 50°. The vertical angle is an angle relative to a horizontal plane. In other words, the measurement rays of the at least one respective SMI sensor point downwards. According to at least one embodiment, there is no common point of intersection of the measurement rays. In other words, each measurement ray defines a line, that is, an infinitely long object with no width, depth, or curvature, and there is no single point in which all these lines cross each other. It is possible that per SMI sensor there is a point in which all the lines of the measurement rays emitted by the respective SMI sensor intersect. By doing so, to determine the angular velocity as well as the linear velocity, no further sensor, like an IMU, is required. 2023PF01303 September 4, 2024 P2023,1224 WO N - 12 - Otherwise, it is possible that there is a common point of intersection in which all the lines defined by the measurement rays cross each other. In this case, preferably there is the further sensor to determine the angular velocity, and the SMI sensors may be used to determine the linear velocity only. According to at least one embodiment, a height above ground of one or some or all of the SMI sensors is at least 0.5 cm or is at least 1 cm or is at least 2 cm or is at least 5 cm. Alternatively or additionally, said height is at most 0.4 m or is at most 0.2 m or is at most 10 cm. In other words, the SMI sensors are located near the ground. The height may refer to a center of the lowermost measurement ray emitted by the respective SMI sensor and directly at a radiation exit face of the respective SMI sensor. The ground level may be defined by a plane of lowermost points of wheels of the robot in the intended use, for example. According to at least one embodiment, seen in top view, the robot’s casing has a centrosymmetric or rotational symmetric footprint, seen in top view. For example, the footprint is a regular polygon or a circle. According to at least one embodiment, a diameter or a mean diameter of the casing and / or of the robot, seen in top view, is at least 2 cm or is at least 0.1 m or is at least 0.2 m. Alternatively or additionally, the diameter or the mean diameter is at most 2 m or is at most 1 m or is at most 0.6 m. In case of a none-circular footprint, for the mean diameter D it applies: D = (4A / ^)1 / 2, wherein A is an area content of the footprint. 2023PF01303 September 4, 2024 P2023,1224 WO N - 13 - According to at least one embodiment, the robot further comprises one or a plurality of distance sensors. For example, the distance sensor or one some or all of the distance sensors is / are an optical sensor, like an SMI sensor, too. It is possible that contrary to the SMI sensors the at least one distance sensor does not point downwards but is arranged horizontally. This means, for example, that a vertical angle between a measurement ray or of measurement rays of the distance sensor and the horizontal plane is between -10° and +10° or is between -5° and +5° or is between -2° and +2°. According to at least one embodiment, the at least one distance sensor is configured to measure a distance between the robot and an obstacle. Preferably. There is a plurality of the distance sensors pointing in different directions in the horizontal plane. According to at least one embodiment, a total horizontal angle framed by the SMI sensors is at least 190° or is at least 230° or is at least 270°. The total horizontal angle is, for example, the minimum horizontal angle included between connection lines of the SMI sensors and a rotation axis or a center of gravity of the robot, seen in top view. According to at least one embodiment, the robot is configured for autonomous driving. Thus, the robot is enabled to find its way across the ground by itself, especially without colliding with obstacles. It is possible that the robot is configured for full or near-full coverage of the ground. For example, in intended operation, over time the footprint of the robot covers at least 80% or at least 90% of an area of 2023PF01303 September 4, 2024 P2023,1224 WO N - 14 - the ground assigned to the robot, for example, in case of a vacuum cleaner robot. It is possible that the robot is configured for indoor use and / or for use on solid ground, like on a concrete floor. Otherwise, the robot may be configured for outdoor use, for example, in case of a robot lawnmower or in case of an agricultural robot. A method for navigating the robot is additionally provided. By means of the method, a robot as indicated in connection with at least one of the above-stated embodiments is navigated. Features of the robot are therefore also disclosed for the method and vice versa. In at least one embodiment, by means of the method a ground- based robot is navigated, the method comprising: - providing the robot, wherein the robot comprises a casing, a plurality of self-mixing interferometry, SMI, sensors arranged at the casing, a motor and a navigation unit; - emitting, by the SMI sensors, measurement rays (r) and receiving, by the SMI sensors, reflected light stemming from the measurement rays; - receiving, by the navigation unit, radial speed and distance information from the SMI sensors; - analyzing, by the navigation unit, the radial speed and distance information and outputting, by the navigation unit, control signals to the motor; and - moving, by the motor, the robot according to the control signals. A robot and a method described herein are explained in greater detail below by way of exemplary embodiments with 2023PF01303 September 4, 2024 P2023,1224 WO N - 15 - reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding. In the figures: Figure 1 shows a schematic top view of an exemplary embodiment of a robot described herein, Figure 2 shows a schematic block diagram of an exemplary embodiment of a method for navigating a robot described herein, Figure 3 shows a schematic top view of an exemplary embodiment of a robot described herein, Figures 4 to 11 show schematic sketches for deriving radial speed and distance information in exemplary embodiments of methods described herein, Figures 12 and 13 show schematic block diagrams of exemplary embodiments of methods for navigating robots described herein, Figure 14 shows a schematic top view of an exemplary embodiment of a robot described herein, Figure 15 shows a schematic cross-sectional view of an exemplary embodiment of a robot described herein, 2023PF01303 September 4, 2024 P2023,1224 WO N - 16 - Figures 16 and 17 show schematic perspective views of exemplary embodiments of robots described herein, Figure 18 shows a schematic top view of a scenario in which an exemplary embodiment of a robot described herein is used, and Figure 19 shows a schematic top view of an exemplary embodiment of a robot described herein. In Figure 1, an embodiment of a ground-based robot 1 is illustrated. The robot 1 comprises a casing 2. At the casing 2, that is, in or on the casing 2, there is a motor 4 and a navigation unit 5. Moreover, there is a measurement arrangement 3 that comprises a couple of self-mixing interferometry, SMI, sensors 31, 32, 33, 34. Optionally, the robot 1 further comprises a further sensor 35, like an inertial measurement unit, IMU, sensor. Moreover, optionally there is one or a plurality of distance sensors 36, and the at least one distance sensor 36 can be an SMI sensor as well, for example. The SMI sensors 31, 32, 33, 34 and the optional distance sensor 36 can be set-up as described in documents WO 2023 / 156380 A1 and / or WO 2023 / 094402 A1. The disclose content of these documents is incorporated by reference. The casing 2 may be of rotational symmetric shape, seen in top view. For example, the casing 2 is of circular shape or has the shape of a polygon, like a regular polygon as a regular hexagon. It is possible that the robot 1 and, thus, the casing 2 is of disc shape so that a diameter of the robot exceeds a height of the robot 1, for example, by at least a 2023PF01303 September 4, 2024 P2023,1224 WO N - 17 - factor of 1.5 or by at least a factor of 3. Seen in top view, the robot 1 comprises an axis of rotation 22. For example, the axis of rotation 22 runs through a center of gravity of the robot. The axis of rotation 22 is preferably a vertical axis. As illustrated in Figure 2, the robot 1 may be operated as follows: In a method step S1, the SMI sensors 31, 32, 33, 34 emit measurement rays r. Radiation of the measurement rays r, like near-infrared radiation, is partially reflected back to the respective SMI sensor 31, 32, 33, 34 by a floor and / or by an obstacle. Thus, the SMI sensors 31, 32, 33, 34 which are arranged at the casing 2 are configured to receive reflected light stemming from the measurement rays r. Method step S1 can be performed continuously or discontinuously after small time intervals. According to method step S2, the navigation unit 5 receives radial speed and distance information from the SMI sensors 31, 32, 33, 34. The radial speed and distance information is obtained by the SMI sensors 31, 32, 33, 34 by means of the measurement rays r and the corresponding reflected light. Method step S2 can be performed each time when the SMI sensors 31, 32, 33, 34 obtained new radial speed and distance information. It is noted that the radial speed and distance information includes at least one of radial speed information or radial distance information. Preferably, the radial speed and distance information comprises at least the radial speed information. 2023PF01303 September 4, 2024 P2023,1224 WO N - 18 - Then, in method step S3, the navigation unit analyzes the received radial speed and distance information and outputs control signals to the motor 4. Method step S3 can be performed each time when being provided with the radial speed and distance information. In method step S4, the motor 4 moves the robot 1 according to the control signals received from the navigation unit. It is noted that the navigation unit can also consider further information related, for example, to a destination or a task of the robot 1. For example, the robot 1 has wheels, not shown in detail, and the motor 1 drives at least one of the wheels to move the robot 1. In Figure 3 the term ‘radial’ is explained. The SMI sensors 31, 32, 33, 34 of the measurement arrangement 3 each emit at least one the measurement rays r. Along each direction of said measurement rays r, a respective speed and / or distance is obtained by the respective SMI sensor 31, 32, 33, 34. Said speed and / or distance is referred to as the corresponding radial speed and / or radial distance. The overall velocity of the robot 1 at a given time is referred to as linear velocity. Accordingly, the robot 1 has an angular velocity VAaround the axis 22 of rotation. At each point of time, the movement of the robot 1 relative to a floor 7 may be characterized by and VA. Hence, there is a plurality of The radial speeds and distances attributed to the measurement rays r, but there is only one and only one VA. The radial distances attributed to the measurement rays r may not only be distances to the floor 7, but also distances to obstacles 8 in or next to a way the robot 1 intends to travel along. 2023PF01303 September 4, 2024 P2023,1224 WO N - 19 - In Figures 4 to 11 the obtaining and VAfrom the measurement rays r is explained in more detail based on the shown diagrams and formulas. Thus, each channel, that is, each measurement ray r, measures the respective radial velocity and distance. The radial velocity is not the derivative of the distance but the instantaneous velocity between the respective sensor and the target in the direction of said measurement ray r. Hence, a direct measurement of the linear velocity and optionally the angular velocity is possible by combining multiple channels. In doing so, there is no need for textured surfaces or specific scene geometry. Thus, computational load can be reduces compared, for example, with camera-based systems. Linear velocity estimation from the radial velocity measurements when all the measurement rays intersect at a single point is illustrated in Figures 4 and 5. In short, the resulting linear velocity v is a linear combination of the vector vriwhich contains the individual radial speed measurements. The ray matrix ûiconnects the linear velocity v with the vector vri. It is noted that v can be a two- dimensional vector when having a two-dimensional movement bound to the floor 7, but in principal v can also be a three- dimensional vector. A dimension N of the vector vriis the number of radial speed measurements. The matrix ûimay be defined by the geometry of the robot 1 and the locations of the SMI sensors only. Hence, v and vrican have different dimensions. The ray matrix ûimay be obtained by calibration. 2023PF01303 September 4, 2024 P2023,1224 WO N - 20 - When all the measurement rays intersect at a single point, optionally there is the further sensor 35 to determine the angular velocity VA. Linear and angular velocities estimation from radial velocity measurements when the measurement rays do not intersect at a single point is shown in the three-dimensional, 3D, case in Figures 6 to 11. The measurement rays r are emitted from respectively assigned emitters E corresponding to the SMI sensors. In case of not having a common point of intersection, there are in principal two options, that is, using the further sensor 35 for measuring the angular velocity VA, or estimating the angular velocity VAby means of the SMI sensors 31, 32, 33, 34. Anyhow, estimation of and VAcan be done with the formula of Figure 7. When the further sensor 35 is used, the contribution from the angular velocity VAcan be subtracted, for example, using the angular velocity measured with an IMU, see Figures 6 and 8. Thus, because of using the further sensor 35, just three unknowns have to be determined. When there is no further sensor 35 and the angular velocity VAis measured by means of the SMI sensors 31, 32, 33, 34, too, the formula depicted in Figure 9 can be used. Because there is no further sensor 35, six unknowns have to be determined from the data of the SMI sensors 31, 32, 33, 34. Because the robot 1 may be ground-based, the two-dimensional, 2D, case is the relevant one, and when using the further 2023PF01303 September 4, 2024 P2023,1224 WO N - 21 - sensor 35, just two unknowns are to be determined, compare Figure 10. In the 2D case and having no further sensor but the SMI sensors 31, 32, 33, 34 only, three unknowns are to be determined, compare Figure 11. Hence, by taking advantage of the baselines between the ray origins of the measurement rays, both the angular and linear velocities can be estimated from the radial speed and distance information. This is because in general, angular and linear velocities influence the radial speed measurements. In Figure 12, a flow chart of the method is illustrated in the case when the contribution from the angular velocity is subtracted, for example, using the angular velocity measured with the further sensor 36 which can be an IMU. In step S11, the radial speeds are measured using the multiple SMI sensors 31, 32, 33, 34. For example, in parallel the angular velocity of the robot 1 is measured using the at least one further sensor 35, like the IMU or another kind of sensor. In step S20, the contribution from the angular velocity to the radial speeds is subtracted. Then, in step S30 stationary targets or obstacles 8 are detected and outliers of the measured values, for example, are removed. Then, in step S41 the linear velocity is estimated. Because the angular velocity VAis determined by means of the at least one further sensor 35, see step S12, the angular velocity VAis already known. 2023PF01303 September 4, 2024 P2023,1224 WO N - 22 - In Figure 13, a flow chart of the method is illustrated in the case when the contribution from the angular velocity is nut subtracted but is estimated by means of using the baselines between the measurement ray origins at the emitter E to estimate both the angular and linear velocities VL, VA. Thus, in method step S13 the radial speeds are measured using the multiple SMI sensors 31, 32, 33, 34. Optionally, also the radial distances are measured. Then, in step S30 stationary targets or obstacles 8 are detected and outliers of the measured values, for example, are removed, as in step S30 of Figure 12. Further, see step S42, both the angular and the linear velocities VL, VAof the robot 1 are estimated based on the data of the SMI sensors 31, 32, 33, 34. Otherwise, the same as to Figures 1 to 11 may also apply to Figures 12 and 13, and vice versa. In Figures 14 to 16, an example of a sensor configuration for robot odometry is shown. The robot 1 includes the four SMI sensors 31, 32, 33, 34 which are arranged at the casing 2. The casing 2 may have a circular footprint, for example. Seen relative to the axis 22 of rotation, the SMI sensors 31, 32, 33, 34 are located equidistant from the axis 22 of rotation, for example, at an edge of the casing 2. Thus, a distance between the SMI sensors 31, 32, 33, 34 and the axis 22 of rotation corresponds to a radius R of the casing 2. For example, the radius R is at least 0.1 m and / or is at most 0.5 m. 2023PF01303 September 4, 2024 P2023,1224 WO N - 23 - The SMI sensors 31, 32, 33, 34 may also be arranged at equal angular distances, that is, may be separated from each other by 360° / M wherein M is the number of the SMI sensors 31, 32, 33, 34. In Figure 14, M = 4 so that each 90° there is one of the SMI sensors 31, 32, 33, 34. An overall total horizontal angle ATof the SMI sensors 31, 32, 33, 34 is thus 270°. The overall total horizontal angle ATmay be the minimum horizontal angle included between connection lines of the SMI sensors 31, 32, 33, 34 and the axis 22 of rotation or the center of gravity of the robot 1, seen in top view. Each one of the SMI sensors 31, 32, 33, 34 has two emitters E so that each one of the SMI sensors 31, 32, 33, 34 emits two of the measurement rays r. A horizontal angle AHbetween the measurement rays r and a radial line between the respective SMI sensor 31, 32, 33, 34 and the axis 22 of rotation is, for example, at least 15° and at most 90°, especially between 50° and 130°, like 60°. Thus, an angle between the two adjacent measurement rays r of each one of the SMI sensors 31, 32, 33, 34 may be at least 30° and / or at most 180°, seen in top view of the robot 1. The two measurement rays r of each one of the SMI sensors 31, 32, 33, 34 may be located in a common plane P. Hence, overall there are four of the common planes P, one for each one of the SMI sensors 31, 32, 33, 34. A vertical angle AVof the measurement rays r, relative to a horizontal plane h, is, for example, at most -15° and / or at least -60°, like 45°. It is possible that all the measurement rays r for determining and VAhave the same vertical angleAV. 2023PF01303 September 4, 2024 P2023,1224 WO N - 24 - A height H of the SMI sensors 31, 32, 33, 34 above the floor 7 is, for example, at least 1 cm or is at least 2 cm and / or is at most 0.2 m or is at most 10 cm. In other words, the SMI sensors 31, 32, 33, 34 are located near the floor 7. Taking into account the relatively large vertical angle AV, a distance of an intersection point between the respective measurement ray r and the floor 7 is about the height H. Hence, by means of the SMI sensors 31, 32, 33, 34 for determining the radial speed and distance information, obstacle detection is possible only in close proximity to the casing 2. Otherwise, the same as to Figures 1 to 13 may also apply to Figures 14 to 16, and vice versa. The robot 1 of Figure 17 also includes distance sensors 36. The distance sensors 36 can be SMI sensors as well. For example, the distance sensors 36 are placed next to the SMI sensors 31, 32, 33, 34 used for determining the radial speed and distance information, or the distance sensors 36 are integrated in the SMI sensors 31, 32, 33, 34. The distance sensors 36 emit rays d for obstacle detection. These rays d are emitted parallel or approximately parallel to the horizontal plane h. Hence, by means of these rays d, relatively long-range obstacle detection is enabled, compared with the SMI sensors 31, 32, 33, 34 for determining the radial speed and distance information. It is possible that each one of the rays d lies in the horizontal plane, or that the rays d emitted by a respective one of the distance sensors 36 are located in a plane in each case. 2023PF01303 September 4, 2024 P2023,1224 WO N - 25 - With such a configuration, the speed measurements can be used for odometry and the distance measurements for obstacle detection. A corresponding scenario is illustrated in Figure 18. For example, the robot 1 is a vacuum cleaner robot. The robot 1 travels across the floor 7 and covers along its way W a portion of the floor 7 as large as possible. By means of the sensors 31, 32, 33, 34, 36, obstacles 8 like walls or furniture or also persons can be detected. Especially when using the distance sensors 36, the room in which the robot 1 moves can be mapped, for example, to optimize the way W when the robot 1 is used in the same room again. Otherwise, the same as to Figures 1 to 17 may also apply to Figure 18, and vice versa. In Figure 19 it is shown that the robot 1 may carry a number of different tools, individually or in any combination. For example, the robot 1 can comprise a cleaning unit 61 in case the robot is a vacuum cleaner robot or a mop robot. Moreover, the tool can be any one of a transport unit 62, a display unit 63 and / or a cutting unit 64, depending on the robot’s application. It is also possible that the tools may be exchangeable, so that at times the robot 1 may carry a display unit 64 and at times the robot may carry a transport unit 62, for example. Otherwise, the same as to Figures 1 to 18 may also apply to Figure 19, and vice versa. The components shown in the figures follow, unless indicated otherwise, exemplarily in the specified sequence directly one 2023PF01303 September 4, 2024 P2023,1224 WO N - 26 - on top of the other. Components which are not in contact in the figures are exemplarily spaced apart from one another. If lines are drawn parallel to one another, the corresponding surfaces may be oriented in parallel with one another. Likewise, unless indicated otherwise, the positions of the drawn components relative to one another are correctly reproduced in the figures. The term ‘and / or’ describes only an association relationship for describing associated objects and represents that three relationships may exist. For example, A and / or B may represent the following three cases: Only A exists, both A and B exist, and only B exists. Correspondingly, the wording ‘at least one of A, B or C’ may represent the following seven cases: Only A exists, only B exists, only C exists, both A and B exist, both A and C exist, both B and C exist, as well as all three A and B and C exist; the same applies analogously if there are only two or more than three entities in the list following ‘at least one of’. Thus, ‘at least one of A or B’ is equivalent to ‘A and / or B’. The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments. This patent application claims the priority of German patent application 102023 126 516.4, the disclosure content of which is hereby incorporated by reference. 2023PF01303 September 4, 2024 P2023,1224 WO N - 27 - List of Reference Signs 1 ground-based robot 2 casing 22 axis of rotation of the robot 3 measurement arrangement 31 first self-mixing interferometry, SMI, sensor 32 second SMI sensor 33 third SMI sensor 34 fourth SMI sensor 35 further sensor 36 distance sensor 4 motor 5 navigation unit 61 cleaning unit 62 transport unit 63 display unit 64 cutting unit 7 ground or floor 8 obstacle AHhorizontal angle total horizontal angle AVvertical angle d ray for obstacle recognition E emitter of a corresponding measurement ray h horizontal plane H height above ground of the SMI sensors M measured radial speed and distance information P common plane of the rays of a specific SMI sensor r measurement ray for radial speed and distance information R radius of the casing S.. method step 2023PF01303 September 4, 2024 P2023,1224 WO N - 28 - VAangular velocity of the robot VLlinear velocity of the robot W way

Claims

2023PF01303 September 4, 2024 P2023,1224 WO N - 29 - Patent Claims 1. A ground-based robot (1) comprising: - a casing (2); - a measurement arrangement (3) comprising a self-mixing interferometry, SMI, sensor (31, 32, 33, 34) and configured to emit a plurality of measurement rays (r) for determining radial speed and distance information by means of self-mixing interferometry; - a motor (4); and - a navigation unit (5), wherein the navigation unit (5) is configured to receive the radial speed and distance information from the SMI sensor (31, 32, 33, 34), to analyze the radial speed and distance information and to output control signals to the motor (4) in order to move the robot (1).

2. The robot (1) according to the preceding claim, further comprising at least one of a cleaning unit (61), a transport unit (62), a display unit (63) or a cutting unit (64), wherein the robot (1) is a vacuum cleaner robot or a warehouse robot or a lawn mower robot.

3. The robot (1) according to any one of the preceding claims, wherein the motor (4) is configured to linearly and to angularly move the robot (1), wherein the SMI sensor or the SMI sensors (31, 32, 33, 34) only, together with the navigation unit (5), are configured to determine a linear velocity and an angular velocity of the robot (1).2023PF01303 September 4, 2024 P2023,1224 WO N - 30 - 4. The robot (1) according to claim 1 or 2, further comprising a further sensor (35), wherein the further sensor (35) is an inertial measurement unit, IMU, sensor, wherein the motor (4) is configured to linearly and to angularly move the robot (1), wherein the SMI sensor or the SMI sensors (31, 32, 33, 34) together with the further sensor (35) and the navigation unit (5) are configured to determine a linear velocity and an angular velocity of the robot (1).

5. The robot (1) according to any one of the preceding claims, wherein the measurement arrangement (3) comprising a plurality of the SMI sensors (31, 32, 33, 34), wherein each one of the SMI sensors (31, 32, 33, 34) is configured to emit at least one of the measurement rays (r) for determining the radial speed and distance information.

6. The robot (1) according to any one of the preceding claims, wherein the SMI sensors (31, 32, 33, 34) together are configured to emit at least three and at most 60 of the measurement rays.

7. The robot (1) according to any one of the two preceding claims, wherein at least one of the SMI sensors (31, 32, 33, 34) is configured to emit at least two of the measurement rays (r) along a first angle and along a second angle different from the first angle, the first angle and the second angle being defined relative to said SMI sensor (31, 32, 33, 34).2023PF01303 September 4, 2024 P2023,1224 WO N - 31 - 8. The robot (1) according to the preceding claim, wherein - the at least two measurement rays (r) of said SMI sensor (31, 32, 33, 34) are located in a common plane (P); and - a difference between the first angle and the second angle is at least 30° and is at most 180°, seen in top view of the robot (1).

9. The robot (1) according to the preceding claim, wherein the common plane (P) has a vertical angle (AV) of at most -15° and of at least -60°, relative to a horizontal plane (h), so that the measurement rays (r) of said SMI sensor (31, 32, 33, 34) point downwards.

10. The robot (1) according to any one of claims 6 to 9, wherein there is no common point of intersection of the measurement rays (r).

11. The robot (1) according to any one of the preceding claims, wherein a height (H) above ground of the SMI sensors (31, 32, 33, 34) is at least 0.5 cm and is at most 0.2 m.

12. The robot (1) according to any one of the preceding claims, wherein the casing (2) has a rotational symmetric footprint; and wherein a diameter (R) of the robot (1), seen in top view, is at least 0.1 m and is at most 1 m.

13. The robot (1) according to any one of the preceding claims, further comprising a distance sensor (37),2023PF01303 September 4, 2024 P2023,1224 WO N - 32 - wherein the distance sensor (37) is arranged horizontally and is configured to measure a distance between the robot and an obstacle, wherein the distance sensor (37) is an optical sensor.

14. The robot (1) according to any one of the preceding claims, wherein the robot (1) is configured for autonomous driving.

15. A method by means of which a ground-based robot (1) is navigated, the method comprising: - providing the robot (1), wherein the robot (1) comprises a casing (2), a plurality of self-mixing interferometry, SMI, sensors (31, 32, 33, 34) arranged at the casing (2), a motor (4) and a navigation unit (5); - emitting, by the SMI sensors (31, 32, 33, 34), measurement rays (r) and receiving, by the SMI sensors (31, 32, 33, 34), reflected light stemming from the measurement rays (r); - receiving, by the navigation unit (5), radial speed and distance information from the SMI sensors (31, 32, 33, 34); - analyzing, by the navigation unit (5), the radial speed and distance information and outputting, by the navigation unit (5), control signals to the motor (4); and - moving, by the motor (4), the robot (1) according to the control signals.

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