Formation control method for a plurality of transport robots

Abstract

The invention relates to a formation control method (400) for a fleet of a plurality of transport robots (100) which are designed to pick up, transport and set down an object, wherein each transport robot has a frame (10) on which a plurality of driving modules (19) are at least indirectly arranged, each of which driving module has a wheel pair (20), the wheels (211, 212) of which are rotatable mutually independently about a common axis of rotation, and wherein the wheel pairs are mounted rotatably about a vertical axis. The aim of the invention is to provide a transport robot which allows for resources-saving and precise steering. The aim is achieved in that the transport robots can be connected to a control unit (80, 81) which is designed to carry out the formation control method by means of which the target rotational speeds of the individual wheels of all wheel pairs can be specified on the basis of target variables with respect to linear velocities and yaw rates of the transport robots in a formation.

Description

[0001]Description Formation control method for multiple transport robots The invention relates to a formation control method for a fleet of multiple transport robots designed to pick up, transport, and deposit an object, wherein each transport robot has a frame on which a plurality of drive modules are arranged at least indirectly, each having a pair of wheels whose wheels can rotate independently of one another about a common axis of rotation, wherein the wheel pairs are rotatably mounted about a vertical axis. Transport robots and related controllers are known in particular from WO 2023 / 274689 A1, US 2022 / 0307281 A1, and US 11,447,025 B2. However, the available control methods are cumbersome to implement and are each individually tailored to the disclosed transport robots. It is therefore an object of the invention to propose a transport robot that allows resource-saving and precise steering.This object is achieved by the formation control method according to claim 1. According to the invention, the transport robots are connectable to a control unit designed to carry out the formation control method, with which the target rotational speeds of the individual wheels of all wheel pairs can be predetermined as a function of target variables relating to linear speeds and yaw rates of the transport robots of a formation. Advantageous developments of the invention are specified below and in the subclaims. According to an advantageous development of the invention, a coupling device is arranged between the travel modules and the frame, which coupling device allows a height adjustment of the frame in a first coupling setting and free rotation of the travel modules relative to the frame in a second coupling setting. Preferably, the frame has a plurality of supports connected to the travel modules.In an advantageous development of the invention, the supports are designed as flat profiles that are arranged on the frame parallel to the frame surface. The supports can be selected as required, particularly with regard to their length, with supports of the same length being installed on a transport robot to ensure a uniform geometry. According to an advantageous embodiment of the invention, the frame has two L-shaped sections that are aligned in a mirror image to one another and are connected to one another at their short ends via a linear drive. Alternatively, the frame is provided with two C-shaped sections that are aligned in a mirror image to one another, the ends of which are each connected to one another via a linear drive. Regardless of the specific design of the sections of the frame, at least one linear drive is designed as a spindle drive with a motor, a spindle and a nut.Preferably, each drive module has a pair of wheels whose wheels are rotatably mounted on axle stubs, with the axle stubs preferably aligned coaxially with each other. Each wheel of the wheel pair is preferably connected to a separate motor, wherein, according to a preferred embodiment of the invention, a belt drive is arranged between the motor and the respective wheel.The axle stubs are preferably connected to a nut that receives a support bolt that is at least indirectly connected to the frame via the coupling device. The coupling device has a first coupling that creates a lockable connection between the turntable and the carrier, and a second coupling that creates a lockable connection between the support bolt and the nut, so that during the first clutch adjustment and an equal but oppositely oriented rotation of the wheels, the support bolt is displaced longitudinally axially relative to the nut. The first coupling and the second coupling are each preferably designed as a two-part ring coupling with friction linings between the rings of the ring coupling, which are frictionally connected to one another by a spring in the engaged state.To disengage such a clutch, a coil is preferably provided which opens the first and second clutch when energized and closes them when de-energized. The energization of such a coil can be implemented using simple control technology specifications, so that such a clutch can be precisely engaged and disengaged. Alternatively, the first clutch and the second clutch have a magnetic coil which alternately releases one mechanical connection and establishes the other mechanical connection. The support robot is preferably connectable to a control unit designed to carry out a control method with which the target rotational speeds of the individual wheels of all wheel pairs can be specified as a function of target variables relating to a linear velocity and a yaw rate of the transport robot.According to a particularly preferred embodiment of the invention, the transport robot is controllable in different operating modes, wherein preferably a precision mode is provided which only allows adjustment of the steering angle of the driving modules while the transport robot is at a standstill, i.e., the horizontal speed and the change in the yaw angle are equal to zero. In other words, the transport robot is controllable in different operating modes, wherein preferably the precision mode is provided, in which adjustment of the steering angle is blocked while the transport robot is moving, and vice versa. In precision mode, the transport robot can preferably perform either only a horizontal movement (translation and / or yaw) or only a change in the steering angle, wherein in precision mode, switching from a horizontal movement to a steering angle adjustment and vice versa is permitted.Specific embodiments of the present invention are described below with reference to the figures. These show: Fig. 1a, b embodiments of a transport robot, Fig. 1c, d side views of a driving module, Fig. 2a a plan view of a vehicle and four transport robots, Fig. 2b a side view of a picked-up vehicle, Fig. 3a a schematic view of a transport robot, Fig. 3b a pair of wheels, Fig. 3c, d, e each a schematic view of a transport robot for performing a movement in modes 1, 2 and 3, Fig. 4a a control method, Fig. 4b a sub-method for angle adjustment, Fig. 5a a formation of several transport robots and Fig. 5b a fleet control system. The present invention encompasses different aspects of a transport robot or a fleet of several interconnected / correlated transport robots. The individual aspects of the invention are described in detail below. a) Height adjustment Fig.1a, b show different embodiments of a single transport robot 100. The transport robot 100 has a frame 10 which is designed to receive an object to be transported. The frame 10 of the embodiment according to Fig. 1a has two L-shaped sections 111, 112 which are aligned in a mirror-inverted manner to one another and whose short ends are connected to one another via a linear drive 12. As a result, the frame 10 is U-shaped in the assembled or mounted state and has an end 13 which is open to the side. In the embodiment according to Fig. 1b, the frame is composed of two C-shaped sections 141, 142 which are aligned in a mirror-inverted manner to one another and whose ends are each connected to a linear drive 12. The frame according to Fig. 1b therefore has a closed and essentially annular contour.In both cases, the linear drives 12 are designed as spindle drives 121 with a motor 15, a spindle 16, and a nut 17. In both embodiments, the linear drives 12 allow adjustment of the frame length F, which is advantageous when picking up objects in the manner described later. In the illustrated embodiment, the frame 10 of the transport robot 100 is connected to four drive modules 19 via a carrier 18. Each drive module 19 has a wheel pair 20, the wheels 211, 212 of which are rotatably mounted on axle stubs 22. The axle stubs 22 of a wheel pair 20 are aligned coaxially with one another and extend along a common axis of rotation. The wheels 211, 212 are connected to separate drive motors 23 so that they can be driven at independent speeds. The axle stubs 22 of a wheel pair 20 are connected to a turntable 24.The turntable 24 of a driving module 19 is connected to the carrier 18 so that the wheel pairs 20 can each rotate about a vertical axis with respect to the frame 10. Such a transport robot 100 can be moved in a predeterminable manner on a support plane by controlling the rotational speeds of the individual wheels 211, 212. Fig. 1c shows a first embodiment of a driving module 19 in a side view. According to this example, the turntable 24 has a nut 25 to which the axle stubs 22 of a wheel pair 20 are fixed. A support bolt 26, which has a bolt head 27 for fastening to the carrier 18, passes through the nut 25. The nut 25 and the support bolt 26 have corresponding threads so that the support bolt 26 can be displaced longitudinally axially within the nut 25 by rotating it in the direction of arrow 28.By rotating the wheels 211, 212 of a wheel pair 20 by the same amount but in opposite directions, the nut 25 is rotated about the support bolt 26, which is arranged non-rotatably on the carrier 18, causing the nut to move in the direction of the arrow 29. This allows the height of the frame 10 to be adjusted relative to the support plane. By adjusting the height of various drive modules 19 to different degrees, the inclination of the frame 10 relative to the support plane can also be adjusted if necessary. Because the wheels 211, 212 of a wheel pair 20 can rotate about the support bolt 16 independently of the height adjustment of the frame 10 during the intended use of the transport robot 100 with such a turntable 24, the set height varies at least to a small extent, which depends on the specific steering movements and the thread pitch of the combination of nut 25 and support bolt 26.To allow continuous height adjustment of the frame 10 relative to the support plane, a switchable coupling device 30 is provided according to the embodiment of Fig. 1d. The coupling device 30 has a first coupling 301, which, in the assembled state, creates a connection between the turntable 24 and the support 18. Furthermore, the coupling device 30 has a second coupling 302, which, in the engaged state, establishes a rotationally fixed connection between the support bolt 26 and the nut 25. The state of the first coupling 301 and the second coupling 302 is disjoint during operation of the drive module 19. This means that one of the couplings 301, 302 always establishes a rotationally fixed connection, while the other coupling releases the rotationally fixed connection.For the purpose of height adjustment, the first coupling 301, in the engaged state, establishes a rotationally fixed connection between the carrier 18 and the support bolt 26 of the turntable 24, which allows height adjustment upon appropriate rotation of the wheels 211, 212 of the wheel pair 20. This is made possible by the relative movement between the support bolt 26 and the nut 25 under the condition that the second coupling 302 releases the rotationally fixed connection between the support bolt 26 and the nut 25. Once the desired height has been set, the first coupling 301 can be transferred to a disengaged state so that the support bolt 26 is freely rotatably connected to the carrier 18. The second coupling 302 is transferred to the engaged state for this purpose in order to establish the rotationally fixed connection between the support bolt 26 and the nut 25.In this (disengaged) state of the first clutch 301 and (engaged) state of the second clutch 302, any desired rotational movements of the wheel pair 20 about the vertical axis can be performed without the height of the frame 10 changing relative to the support plane, because the support bolt 26 rotates relative to the carrier 18 and not relative to the nut 25. According to a specific embodiment of the invention, the first clutch 301 and the second clutch 302 are each designed as a two-part ring clutch with friction linings between the rings, wherein the friction linings are frictionally pressed together by a spring in the engaged state. For disengagement, a coil is preferably provided which opens the first clutch 301 and the second clutch 302 in an energized state.Alternatively, the first clutch 301 and the second clutch 302 can also be designed in such a way that a magnetic coil integrated into the bolt head 27 alternately releases one mechanical connection and establishes the other mechanical connection, e.g. by disengaging the first clutch 301 and engaging the second clutch 302 or vice versa. Regardless of the specific design of the first clutch 301 and the second clutch 302, the bearing of the turntable can be designed by an axial bearing 32 in various designs, e.g. ball or needle bearings, plain bearings. Furthermore, it can be designed with or without a seal. By means of a single transport robot 100, as shown in Fig. 1a, b, different objects can be transported, which for this purpose are picked up by the frame 10 or placed on the frame 10. The embodiment according to Fig.1a is designed to pick up objects that rest on the support surface of the transport robot 100. The transport robot 100 positions itself such that the L-shaped sections 111, 1112 of the frame 10 encompass the object on the right and left sides. By pushing the L-shaped sections 111, 112 of the frame 10 together using the linear drive 12, the object is secured and lifted using the described height adjustment. The picked up object can then be transported along predetermined trajectories and deposited at its destination. The embodiment according to Fig. 1b assumes that the frame 10 can move beneath a load-bearing section of the object, so that the object can be lifted, if necessary after adjusting the support surface, by adjusting the length of the frame 10. Otherwise, the lifting and transporting of the picked up object are functionally identical.With a fleet of multiple transport robots 100, vehicles 31 in particular can be parked automatically. Fig. 2a shows a plan view of a vehicle 31 and four transport robots 100, each of which can be moved in the (unnumbered) direction of the arrow such that they each grip a vehicle wheel 33 on the left and right sides. By lifting the respective vehicle wheels 22 in the manner already described, a spacing 35 results between the vehicle wheels and the support plane 34, as shown in the side view of Fig. 2b. In this state, the vehicle can be parked by the four transport robots in a manner that significantly exceeds the typical maneuverability of vehicles with two-wheel or four-wheel steering.b) Kinematics of an individual transport robot To control the movement of a transport robot 100, a method 200 is provided with which the target rotational speeds n of the individual wheels 211, 212 of all wheel pairs 20 can be determined as a function of target variables relating to the desired linear velocity v and the desired yaw rate of the transport robot 100. To carry out the method 200, a control unit is provided which has several calculation units for data exchange and data processing. First, Fig. 3a shows a schematic plan view of a transport robot 100 with the variables relevant for controlling / regulating the movement. Shown in detail: ^ The frame length F as the sum of the basic length F0 and the variable length F set by the linear drive 12. V, ^ the wheel pairs 20 with the wheels 211, 212, ^ the center point M1 of the transport robot 100, ^ the center points M2 of the wheel pairs 20, ^ the track width m of the individual wheel pairs 20 and ^ the track width w between the center points M2 of two wheel pairs 20. Fig. 3b shows the executable movements using the example of a wheel pair 20. The wheels 211, 212 of the wheel pair 20 can be rotated by the same amount and in the same direction, so that the wheel pair 20 moves at a linear velocity v. To set an angle ^ or to change a set angle ^, the wheels 211, 212 of the wheel pair 20 are driven at different speeds n, so that the wheel pair 20 orbits around the instantaneous pole M3. By independently adjusting the rotational speeds n of the wheels 211, 212 of a wheel pair 20, predetermined trajectories can be followed on the contact plane. With respect to the transport robot 100, the components of the linear speeds vx , v y and the yaw rate ^ between the following modes: Mode 1: Translation of the transport robot 100, in which the yaw rate disappears ( ^ = 0). Mode 2: Yawing of the transport robot 100 around its center M1, in which the components of the linear velocities v x , v y disappear ( ^ ≠ 0 , v x = 0, v y = 0). Mode 3: Combination of translation and yaw ([ ^ ≠ 0, v x ≠ 0, v y = 0] or [ ^ ≠ 0, v x = 0, v y ≠ 0] or [ ^ ≠ 0, v x ≠ 0, v y ≠ 0]), with translation and yaw occurring instantaneously (simultaneously). Fig. 3c shows the transport robot 100 in a mode 1 setting, and thus in a setting for pure translation. With respect to the vehicle coordinate system, all wheel pairs 20 of the individual drive modules 19 are aligned identically. The respective angles to be set ^ n relative to the x-axis are: For the special case that a translation along the y-axis is to be performed, the angle ^ n to determine: This gives the speed v: The speeds n of the wheels 211, 212 are determined by the wheel diameters r Rad from: 1 ^^ ^,^ ൌ ^^ ^,ଶ ൌ 2 ^^ ^^ோ^ௗ ∙ ^^ ^ This is due to ^^ ^,^ ൌ ^^ ^^ ^^൫ ^^ ^,^ ൯ and ^^ ^,ଶ ൌ ^^ ^^ ^^൫ ^^ ^,ଶ ൯ a maximum speed can be specified. Fig. 3d shows the transport robot 100 in a mode 2 setting, and thus in a setting for rotation around the vertical axis (yaw). For this purpose, the wheel pairs 20 are aligned such that the virtual axes of rotation of all wheel pairs 20 intersect the center point M1 of the transport robot 100. For the angles ^ n applies: ^^ ସ ൌ ^^ ^The distance D between the center M1 of the transport robot 100 and the centers M2 of the wheel pairs 20 is given by the present geometry: ^^ ൌ 0,5 ^ ^^ ଶ ^ ^^ ଶ For the speeds v of equal magnitude but different directions n applies: ^^ ଶ ൌ െ ^^ ^ ^^ ଷ ൌ ^^ ^ ^^ ସ ൌ ^^ ଶ For the speeds of (virtual) wheels located in the centers of the wheel pairs 20, the speeds would be where n i = lim(n i ) a speed limit can be specified. Based on this, the speeds n of the wheels 211, 212 of the individual wheel pairs 20 are determined from: ^^ ^^ െ 0.5 ^^^ ଶ ൌ ^^ ∙ ^^^ ^^ ൌ ^^ െ 0.5 ^^ଶ^ ^^ ∙ ^^ଶ ^^ ^^ ^ 0.5 ^ଶ ଶ ൌ ^ ^ ^ ∙ ^^ଶ ^^ ^^ ^ 0.5 ^^ଷ ^ ൌ^^ ∙ ^^ଷ ^^ ^^ െ 0.5 ^^ଷ ଶ ൌ ^^ ∙ ^^ଷ ^^ െ 0.5 ^^ ^^ ^^ ^ 0.5 ^^ସ ଶ ൌ ^^ ∙ ^^ସ Fig. 3e shows the transport robot 100 in a mode 3 setting, and thus in a setting for a movement resulting from a linear combination of translation and yaw. Here, the drive modules 19 are set such that the rotational axes of the wheel pairs 20 intersect the instantaneous center M3 of the rotational movement, with the instantaneous center M3 being spaced from the center M1 of the transport robot 100. ^^ ^ 0.5 ^^^^ ି^ ோ ଷ ൌ െtan ൬ ^ ^ ^ ோ െ 0,5 ^^ ^^ ൌ െtan ି^ ^^ோ ^ 0.5 ^^ସ ൬ ^^ ^ 0.5 ^ ோ ^^ For the speeds v i the centers M2 of the wheel pairs 20 applies: A (virtual) wheel would have a speed n i of each Here, a speed limit of n i = lim(n i) can be specified. This results in the target values ​​in relation to the speeds n of the individual wheels 211, 212 of the wheel pairs 20 from: ^൫ ^^^ െ ^^ ^^ ^^ ^^ ^ ^^ோ ^ ൯ ∙ 0.5 ^^ ^ Overall, there are calculation rules for all three modes that are taken into account when controlling a transport robot 100. In particular, the calculation rules allow the control of a transport robot 100 by specifying rotational speeds n of the individual wheels 211, 212, which are determined as a function of target values ​​related to the speed v and the yaw rate ^ of the transport robot 100. Fig. 4a shows the control method 200 with the calculation units for an individual transport robot 100 in the context of a flowchart. The method 200 is started with a request 50 to execute a journey, wherein the position and orientation of the transport robot 100 are specified as (x, y, ^). DESThis data is transferred to a calculation unit 51 “Single Robot Navigation” for a single transport robot 100, which, taking into account position data 521 of a digital map 52, calculates the target values ​​for the horizontal speeds and the yaw rate (v x ,v y , ^) DES This data is transferred to a calculation unit 53 "Inverse Differential Kinematics", which calculates the setpoints for the angles ( ^1,…, ^4) DES of the driving modules 19 and the preliminary rotation rates (n 11 , n 12 ,…,n 42 ) pDES of the individual wheels 211, 212. Using the calculation unit 54 "Angle Controller", the target values ​​for the angles (^1,…, ^4) DES of the driving modules 19 and the preliminary rotation rates (n 11 , n 12 ,…,n 42 ) pDES of the individual wheels 211, 212 the set values ​​for the rotation rates (n 11 , n 12 ,…,n 42 ) DESof the individual wheels 211, 212. If necessary, the height and angle of the frame 10 relative to the support plane 34 can be adjusted by the request 71. Usually, the request 71 to adjust the height or angle relative to the support plane is made while the transport robot is stationary, i.e., the horizontal speed and the yaw rate of the transport robot are zero during the height adjustment. After the target speeds of the wheels with (n 11 , n 12 ,…,n 42 ) DES are finally determined, these are transferred to the drive controllers 55. The drive controllers control the drive motors 56 of the transport robot, ie they provide a pulse-width modulated voltage signal, with the help of which the speed of the drive motors and thus of the wheels is adjusted according to the setpoint (n 11 , n 12 ,…,n 42 ) DESThe current actual values ​​of the wheel speeds (n 11 , n 12 ,…,n 42 ) ACT and the current angles ( ^1,…, ^4) ACT of the wheel pairs are transferred to a calculation unit 57 “Odometry”, which calculates the horizontal speeds and the yaw rate (v x ,v y , ^) odom1 and transferred to the calculation unit 58 "Localization". Furthermore, data from an inertial measurement unit 59 (IMU) is also transferred to the calculation unit 58 "Localization". Here, values ​​of the acceleration and the yaw rate are converted, in particular by means of an integrator 60, into the horizontal speeds and the yaw rate (v x ,v y , ^) odom2converted. In addition, the calculation unit 58 "Localization" also receives image data 611 from a camera 61 and lidar data 621 from a lidar 62. The calculation unit 58 "Localization" determines the current position and the current yaw angle (x, y, ^) from the received input data. ACT and forwards this data to the "Single Robot Navigation" calculation unit 51, thus closing the loop of the control method 200. The previously described method 200 terminates as soon as there is no request to execute a movement. The control method 200 also allows switching to a formation control 400, for which a switch 63 is provided. Within the framework of the formation control 400, which will be discussed in more detail later, the "Localization" calculation unit 58 transfers the current position data and the current yaw angle (x, y, ^) to a "Multi Robot Formation Controller" calculation unit 64. ACT, which represents the target speeds and yaw rates in the form of (v x ,v y , ^) Des,FC The control of the individual transport robots 100 otherwise takes place according to the described method 200. For setting the length F of the frame 10, a substantially supplementary sub-method 65 is provided. According to this sub-method, the transport robot 100 receives a request 66 to lengthen or shorten the length F of the frame 10, which occurs, for example, when picking up and setting down an object. The request 66 to change the frame length F is transmitted together with the desired frame length F DES a calculation unit 67 “Position Controller”, which, taking into account the current frame length and the required frame length F DES a speed n LS,DESof the spindle 16, so that the frame length F changes as specified by means of a control unit 68 “Lead Screw Drive Controller” and a motor 69 “Lead Screw Plant” by setting a current speed n LS,ACT the spindle 16. The resulting instantaneous frame length F ACT is continuously transferred to the calculation unit 67 "Position Controller", which aborts the sub-process 65 as soon as the current frame length matches the target frame length. The current frame length F ACT is also transferred to the calculation unit 57 “Odometry” and the calculation unit 53 “Inverse Differential Kinematics”, so that the current frame length of the transport robot 100 is used in the calculation of the target speeds (n 11 , n 12 ,…, n 42 ) pDES of the wheels 211, 212 and the angle ( ^1,…, ^4) DESbe taken into account. The control method 200 also includes a sub-method 70 for adjusting the angle of the wheel pair 20. The sub-method 70 is shown in Fig. 4b in the form of a flowchart. In response to a request 71 to raise the frame 10, the required rotational speeds of the wheels 211, 212 of all wheel pairs 20 are determined so that they rotate in such a way that the heights of the supports 18 and thus the angle of the frame 10 relative to the support plane 34 are set as specified. The height adjustment takes place while the transport robot is stationary, i.e., the horizontal speed and the yaw rate of the transport robot are zero during the height adjustment. The angle of the wheel pairs 20 is adjusted during travel based on the setpoint values ​​for the angles (^1,..., ^4). DES of the driving modules 19 and the preliminary rotation rates (n 11 , n 12 ,…,n 42 ) pDESof the individual wheels 211, 212. The final target values ​​for the rotation rates (n 11 , n 12 ,…,n 42 ) DESThe individual wheels 211, 212 are additively subjected to a negative or positive contribution of a differential speed for setting the angle. c) Precision mode It is envisaged that an individual transport robot 100 can be controlled in different operating modes, which are determined depending on the task to be performed. The control architecture and thus the available operating modes are described in detail below. A first operating mode BM1 relates to the travel of an individual transport robot 100 and is independent of any loading situation. A second operating mode BM2 relates to a precision mode 300, which is selected, for example, when picking up and / or setting down the transported object.In precision mode 300, when the transport robot 100 changes its direction of travel, the transport robot 100 stops. The drive modules 19 then rotate to the specified steering angle, and only then does travel resume. In other words, precision mode 300 interrupts the normal travel operation of the transport robot 100. Normal travel operation is characterized by the ability to change the steering angle of the drive modules 19 instantly while traveling. This results in good maneuverability, but limits the shape of the trajectory curve of the horizontal speed and yaw angle change. Improved maneuverability and thus more precise control in very small spaces is achieved in precision mode 300 by allowing the steering angle of the drive modules 19 to be adjusted not while traveling, but only when the transport robot 100 is stationary, i.e., when the horizontal speed and yaw angle change are zero.This has the advantage that unwanted changes in the pose of the transport robot 100 due to steering movements of the drive modules 19 during travel are minimized, thus maintaining the transport robot's previous orientation. Overall, by adjusting the steering angle of the drive modules while stationary, constraints resulting from the kinematics that lead to restrictions in the trajectory of the transport robot's pose can be eliminated. This allows for significantly improved maneuverability and thus more precise control in very small spaces. Example: In operating mode BM1, the transport robot 100 first travels straight ahead to the height of a wheel of a vehicle 31 that is to be parked by a fleet of transport robots 100. The command is then given to move parallel to the wheel from the side in order to lift the wheel, which requires translation and yaw due to the change in direction.However, because translation and yaw occur instantaneously during a change of direction in operating mode BM1, it may happen that the transport robot 100 rotates around its vertical axis and positions itself incorrectly. In precision mode 300, on the other hand, the transport robot 100 stops between straight-ahead travel and parallel travel, and the drive modules 19 are aligned while stationary. Furthermore, in precision mode 300, the distance to be maintained between the transport robot 100 and obstacles is reduced compared to operating mode BM1, which improves the navigation capability of the transport robot 100, particularly when picking up an object. Likewise, the possible travel speed is reduced so that the reduced distance to obstacles can be handled in the calculation of the navigation data. The low preset speed in precision mode also serves for manual operation via a remote control.In precision mode 300, the transport robot 100 primarily performs translations in the form of straight-ahead and parallel travel rather than rotations. This is particularly advantageous when parking a vehicle 31, as it allows precise positioning on the inside of the tire when space is limited beneath the vehicle 31. When approaching a vehicle wheel underneath the vehicle 31, the transport robot 100 in precision mode 300 can also access images from a camera aligned with the inside of the vehicle wheel in order to detect (track) the position and enable controlled alignment with respect to the vehicle wheel. A third operating mode BM3 relates to the length adjustment of the frame, which occurs particularly when picking up and setting down objects that are to be transported or have been transported. During operating mode BM3, the center point M1 of the transport robot 100 does not move.A fourth operating mode BM4 refers to a rest mode in which the transport robot 100 performs no movement. A fifth operating mode BM5 refers to the lifting and setting down of an object. In this case, any first coupling 301 between the drive modules 19 and the supports 18 is engaged (locked), and any second coupling 302 is disengaged to release the frictional connection between the support bolt 26 and the nut 25. The wheels 211, 212 of the wheel pairs 20 are then controlled such that the wheel pairs 20 rotate around their common center point M2, so that the frame 10 is raised or lowered. As soon as the frame 10 has reached the desired height, any couplings 301 can be disengaged (released) again, and any couplings 302 can be engaged, so that no height adjustment occurs during any steering movements. A sixth operating mode BM6 refers to a waiting time in which all previous orpending requests are deleted or overwritten. d) Formation control In order to transport larger objects, such as vehicles 31, several transport robots 100 operate together in a fleet operation in a predeterminable formation. A formation control method 400 and a formation control unit 80 are provided for controlling the fleet. Fig. 5a shows a formation of four transport robots 100, which are to travel a specific trajectory in this formation to transport an object (not shown). Essentially three different proposals are provided for the arrangement of the formation control unit 80. Firstly, the formation control unit 80 can be located within a stationary control unit 81, which controls each individual transport robot 100 via a functionally configured interface.Alternatively, a guide robot 82 is provided, which accommodates the formation control unit 80 and is not used to transport the object. This guide robot 82 travels a trajectory at a distance from the fleet, and the individual transport robots 100 of the fleet follow the guide robot 82, which controls the individual transport robots 100 for this purpose via a suitable interface. Furthermore, one of the transport robots 100 of the fleet can also be designated as the guide robot 83 with transport function, which controls the movement of the remaining transport robots 100 of the fleet. Fig. 5b shows the process sequence of the formation control method 400 in a flowchart. According to this, the target position and orientation (x, y, ^) are first determined using a detection unit 92. F , DESof the formation and, together with the map data 521 of a map 52, transferred to a calculation unit 84 "Formation Path Planning", which determines the path of the formation as a "Global Plan" 85, which consists of vectors of target positions and orientations (x,y, ^) F , DES of the formation. The "Global Plan" 85 is supplemented by any kinematic limitations or constraints 86 and relative position data 871 from a "Formation Configurator" calculation unit 87 and transferred to a "Formation Trajectory Planning" calculation unit 88. There, the target speeds and the target yaw rates of the individual transport robots 100 are calculated with (v x ,v y , ^) pn,DES The data is calculated using nested calculation units 89 “Cascaded Position Controller” taking into account (x,y, ^) Pn,Des to (v x ,v y , ^) pn,DES,Cfrom which nested calculation units 90 “Single Robot Inverse Differential Kinematics” derive the target values ​​of the wheel speeds n and the angle ^ n for all transport robots 100. The nested calculation units 89 “Cascaded Position Controller” are connected to a position determination 91 of each individual transport robot 100, with which the positions and angles in the form of (x,y, ^) pn,ACT These data are also converted into a matrix (x,y, ^) by a calculation unit 93 “Single Robot Poses Fusion”. F,ACTlinked and transferred to the calculation unit 84 “Formation Path Planning” as input data. List of reference symbols Transport robot Control method Precision mode Formation control method Frame L-shaped section L-shaped section Linear drive Spindle drive Open end C-shaped section C-shaped section Motor Spindle Nut Carrier Driving module Pair of wheels Wheel Wheel Stub axle Drive motor Turntable Nut Support bolt Bolt head Direction of arrow Direction of arrow Coupling device First coupling Second coupling Vehicle Thrust bearing Vehicle wheel Contact plane Spacing Requirement Calculation unit “Single Robot Navigation” Map Map data Calculation unit “Inverse Differential Kinematics” Calculation unit “Angle Controller” Drive controller Drive with driven transport robot Calculation unit “Odometry” Calculation unit “Localization” Inertial measurement unit Integrator Camera Camera data LIDAR LIDAR data Switch Calculation unit “Multi Robot FormationController" sub-procedure request calculation unit "Position Controller" control unit motor sub-procedure request formation control unit stationary control unit leading robot leading robot calculation unit "Formation Path Planning" global plan kinematic limitation calculation unit "Formation Configurator" position data calculation unit "Formation Trajectory Planning" 89 calculation unit "Cascaded Position Controller" 90 calculation unit "Single Robot Inverse Differential Kinematics" 91 position determination 92 acquisition unit 93 calculation unit "Single Robot Poses Fusion" v linear velocity v x , v y Cartesian components of linear velocity ^ Yaw rate n Speed ​​n Index F Frame length F0Base length F v variable length M1Center point of the transport robot M2Center point of a wheel pair M3Instantaneous center w Track width m Track width r Rad Wheel diameter

Claims

1. Formation control method (400) for a fleet of several transport robots (100) designed to pick up, transport, and deposit an object, wherein each transport robot (100) has a frame (10) on which several drive modules (19) are arranged, each having a wheel pair (20), the wheels (211, 212) of which are rotatable independently of one another about a common axis of rotation, wherein the wheel pairs (20) are mounted rotatably about a vertical axis, characterized in that the transport robots (100) are connectable to a control unit (80, 81) designed to carry out the formation control method (400), with which the target rotational speeds of the individual wheels (211, 212) of all wheel pairs (20) can be specified as a function of target variables relating to linear speeds and yaw rates of the transport robots (100) of a formation.Formation control method (400) according to claim 1, characterized in that a coupling device (30) is arranged between the travel modules (19) and the frame (10), which coupling device allows a height adjustment of the frame (10) in a first coupling setting and a free rotation of the travel modules (19) with respect to the frame (10) in a second coupling setting.

3. Formation control method (400) according to one of claims 1 or 2, characterized in that the frame (10) has a plurality of supports (18) connected to the travel modules (19).

4. Formation control method (400) according to one of claims 1 to 3, characterized in that the frame (10) has two L-shaped sections (111, 112) aligned in a mirror-inverted manner to one another, which are connected to one another at their short ends via a linear drive (12).Formation control method (400) according to one of claims 1 to 3, characterized in that the frame (10) has two C-shaped sections (141, 142) aligned in a mirror-inverted manner to one another, the ends of which are each connected to one another via a linear drive (12).

6. Formation control method (400) according to one of claims 1 to 5, characterized in that at least one linear drive (12) is designed as a spindle drive (121) with a motor (15), a spindle (16), and a nut (17).

7. Formation control method (400) according to one of claims 1 to 6, characterized in that each travel module (19) has a wheel pair (20), the wheels (211, 212) of which are rotatably mounted on axle stubs (22), wherein the axle stubs (22) are preferably aligned coaxially with one another.

8. Formation control method (400) according to claim 7, characterized in that each wheel (211, 212) of the wheel pairs (20) is connected to a separate motor (23). 9.Formation control method (400) according to one of claims 7 or 8, characterized in that the axle stubs (22) are connected to a nut (25) that receives a support bolt (26) that is at least indirectly connected to the frame (10) via the coupling device (30), wherein the coupling device (30) has a first coupling (301) that creates a lockable connection between the turntable (24) and the carrier (18), and a second coupling (302) that creates a lockable connection between the support bolt (26) and the nut (25), so that during the first coupling setting and an equal but oppositely oriented rotation of the wheels (211, 212), the support bolt (26) is displaced longitudinally axially relative to the nut (25).Formation control method (400) according to one of claims 1 to 9, characterized in that the first clutch (301) and the second clutch (302) are each designed as a two-part ring clutch with friction linings between the rings of the ring clutch, which are frictionally connected to one another by a spring in the engaged state.

11. Formation control method (400) according to claim 10, characterized in that a coil is provided for disengaging, which opens the first and second clutches (301, 302) in the energized state and closes them in the de-energized state.

12. Formation control method (400) according to one of claims 1 to 9, characterized in that the first clutch (301) and the second clutch (302) have a magnetic coil that alternately releases one mechanical connection and establishes the other mechanical connection.

13. Formation control method (400) according to one of claims 1 to 11, characterized by a control unit configured to carry out a control method (200) with which the target rotational speeds of the individual wheels (211, 212) of all wheel pairs (20) can be specified as a function of target variables relating to a linear velocity and a yaw rate of the transport robot (100).

14. Formation control method (400) according to claim 13, characterized in that the transport robot (100) can be controlled in different operating modes by means of the control method (200), wherein a precision mode (300) is preferably provided in which a change in the steering angle of the driving modules (19) is only permitted when the transport robot (100) is stationary.Formation control method (400) according to claim 14, characterized in that the transport robot (100) in the precision mode (300) can perform either only a horizontal movement (translation and / or yaw) or only a change in the steering angle, wherein in the precision mode (300) a switch from a horizontal movement to a steering angle adjustment and vice versa is permitted.

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