Method of controlling automated guided vehicle, automated guided vehicle, and system

Abstract

A method of controlling an automated guided vehicle (AGV) (12a), the AGV comprising a support structure (18) and at least three wheel units (20a), each wheel unit (20a) comprising a wheel (22a), the wheel (22a) being rotatable about a horizontal wheel axis; wherein for at least two of the wheel units, the wheel units comprise a steering motor (54); and wherein the method comprises: providing a support point (102a) associated with the support structure and an application load, the application load comprising an application force (98a); representing the applied load by a remote force (104a) acting at a remote point (106a) horizontally offset from the support point and in a horizontal remote direction (108a) transverse to the offset line (110a); and for at least two of the wheel units comprising the steering motor, positioning each wheel in a steering position such that the instantaneous center of rotation ICR (100a) of each wheel substantially coincides with the remote point.

Description

Technical Field

[0001] This disclosure generally relates to automated guided vehicles (AGVs). Specifically, it provides a method for controlling an AGV, the AGV itself, and a system including the AGV. Background Technology

[0002] Automated Guided Vehicles (AGVs) are typically self-powered, self-propelled vehicles. AGVs can be used to transport materials and other items from one location to another without requiring a driver. AGVs may also include manipulators for performing various tasks. AGVs are commonly used in manufacturing sites, warehouses, post offices, libraries, ports, airports, and in some hazardous locations and specialized industries.

[0003] WO 2020259830 A1 discloses a method for braking an AGV. The AGV includes a support structure and at least three drive units connected to the support structure. The method includes: positioning the wheels of the drive units in an invalid configuration; and performing position control on each wheel about a corresponding steering axis in the invalid configuration. While the method in WO 2020259830 A1 provides a good general solution for braking AGVs, the invalid wheel configuration is not suitable for any specific load.

[0004] If an AGV including a manipulator is instructed to remain stationary while performing a task using the manipulator, there is a risk of task failure if the AGV's support structure moves even slightly (e.g., translational movement and / or rotation). To mitigate this risk, the manipulator can only perform relatively simple, low-accuracy tasks and operates at low speeds, potentially requiring frequent AGV recalibration, and / or avoiding interactions between the manipulator and its environment, such as push operations. All of these measures limit the AGV's productivity. The inability to guarantee the stability of the support structure also prevents the manipulator from performing more complex tasks. Using dedicated brakes to keep the support structure stationary significantly increases the AGV's cost. Summary of the Invention

[0005] One object of the present invention is to provide an improved method for controlling automated guided vehicles (AGVs).

[0006] Another object of the present invention is to provide an improved AGV.

[0007] Another object of the present invention is to provide an improved system.

[0008] These objectives are achieved by the method according to claim 1, the AGV according to claim 9, and the system according to claim 17.

[0009] This invention is based on the understanding that by representing the applied load on the AGV by a remote force acting at a remote point, and by orienting the wheels of the AGV so that its instantaneous rotation center ICR coincides with the remote point, the increased stiffness of the AGV can be obtained.

[0010] According to a first aspect, a method for controlling an Automated Guided Vehicle (AGV) is provided, the AGV comprising a support structure and at least three wheel units, each wheel unit comprising a wheel rotatable about a horizontal wheel axis; wherein for at least two of the wheel units, the wheel unit includes a steering motor arranged to drive the wheel about a vertical steering axis; and wherein the method comprises: providing a support point associated with the support structure; providing an applied load associated with the support structure, the applied load comprising an applied force; representing the applied load by a remote force acting at a remote point horizontally offset from the support point and acting in a horizontally remote direction transverse to the offset line between the support point and the remote point; and for at least two of the wheel units including the steering motor, positioning each wheel in a steering position such that the instantaneous rotation center ICR of each wheel substantially coincides with or coincides with the remote point.

[0011] The steering positions of the corresponding wheels are considered to form a wheel configuration. The wheel configuration according to this method allows for an increase in the stiffness of the support structure relative to the applied load. Since the applied load is represented by a remote force acting in a remote direction, this remote direction can be referred to as the preferred direction, in which the stiffness of the support structure is highest or nearly highest. Therefore, this method provides a wheel configuration adapted to the applied load.

[0012] The AGV's performance is improved due to the increased stiffness of the support structure provided by this method. This method ensures that any known applied load, including applied forces, is converted into pure lateral forces (i.e., in the corresponding direction along the wheel axis) positioned in the corresponding steering position to provide ICR. Positioning the wheel in the corresponding steering position according to the ICR provides motion locking of the wheel, and thus provides braking of the AGV.

[0013] Each wheel is configured to support the support structure on a horizontal ground surface (such as a floor). The stiffness of the support structure refers to its ability to resist horizontal loads acting on it without shifting horizontally relative to the ground surface.

[0014] The wheel configuration provided by this method may not offer the highest stiffness for applied forces acting in any direction. However, for applied forces acting in remote directions, the wheel configuration will provide optimal or near-optimal stiffness.

[0015] When two or more wheels are positioned to provide an ICR (Intercepting Radius), it means that the wheel axes of these wheels intersect with the ICR. For two non-parallel wheels, an ICR will always be provided. For two parallel wheels, the ICR will be at an infinite distance from the AGV.

[0016] One, several, or all of the at least two wheel units including a steering motor may also include a drive motor arranged to drive the wheel around the wheel axis. In these cases, positioning these wheels such that the ICR coincides with the remote point will ensure that the applied load does not generate any torque or any significant torque on such drive motors. ICR substantially coinciding with the remote point can mean that the maximum distance between the ICR and the remote point is less than 10% of the maximum distance between the remote point and one of the wheels, such as less than 5%.

[0017] The AGV may optionally include a manipulator. The manipulator can be a programmable robotic arm on three or more axes (such as six or seven axes). The manipulator can be supported on a support structure and is capable of movement relative to the support structure. When the AGV including the manipulator is stationary, the support structure is in a stationary position, but the manipulator can move relative to the support structure. The AGV can be, for example, an Autonomous Mobile Robot (AMR) or an Autonomous Mobile Manipulator Robot (AMMR) including a manipulator.

[0018] Specifically, when the AGV includes a manipulator, the increased stiffness of the support structure provided by this method improves the AGV's productivity. The increased stiffness of the support structure provided by this method enables the manipulator to perform more advanced tasks, allows the manipulator to perform tasks at higher speeds, reduces or eliminates the need for AGV recalibration, and enables interaction with external objects or more advanced interactions.

[0019] When the manipulator performs a first task generating a first applied load, the wheels, including at least two wheel units of the steering motor, can be positioned in a first wheel configuration according to this method. When the manipulator performs a second task generating a second applied load different from the first applied load, the wheels, including at least two wheel units of the steering motor, can be positioned in a second wheel configuration different from the first wheel configuration according to this method. This allows for a time series of different wheel configurations to provide optimal stiffness for each task performed by the manipulator. This implies that while the manipulator performs several tasks, the support structure can remain stationary, but after each task is completed, at least two wheels can rotate about their respective steering axes to provide optimal stiffness for the next task.

[0020] The supporting structure can be a platform. Specifically, when the supporting structure is in a static state, the method according to the first aspect can be performed.

[0021] This method provides maximum stiffness at the support point. The support point can be arbitrarily selected. It can be predetermined and selected by the AGV's control system or by a human user. In either case, the support point can be provided directly or indirectly in the control system based on user input.

[0022] The applied load can be a load acting on or estimated to act on the supporting structure. Correspondingly, the applied force can be a force acting on or estimated to act on the supporting structure. In addition to applied force, the applied load may also include torque. Torque can be a torque acting on or estimated to act on the supporting structure. In any case, the characteristics of the applied load (such as its one or more vectors in the horizontal plane) can be provided by the control system or online. The applied force, represented by a remote force, can be executed by the control system or online.

[0023] The steering positions of at least two wheel units, including the steering motor, can be calculated using inverse kinematics (e.g., based on the positions of the support points, the remote points, and the respective wheel unit's position in a local coordinate system fixed relative to the support structure). These calculations can be performed by the control system or online. The positioning of the wheels in their respective steering positions can be controlled by the control system.

[0024] In this method, the wheel configuration adopted by the wheels can be either a valid wheel configuration or an invalid wheel configuration. An invalid wheel configuration includes all wheel configurations other than the valid configuration. A valid wheel configuration includes only the orientation in which all wheels are parallel and the orientation in which all wheels provide ICR.

[0025] Two, several, or all wheel units may include a steering motor arranged to drive the wheel about a vertical steering axis. The method may include positioning each wheel in a steering position for all wheel units including the steering motor, such that the instantaneous center of rotation (ICR) of each wheel substantially coincides with or is coincident with a remote point. In addition to at least two steerable wheels, the AGV may also include one or more non-driven wheels, such as swivel casters or other passive wheels.

[0026] The terms "application load" and "application force" were chosen because application load includes application force, and because application force can be different from the remote force that represents application load. Application load, application force, and remote force can be referred to as primary load, primary force, and secondary force, respectively.

[0027] For at least three wheel units in a wheel unit, the wheel unit may include a steering motor arranged to drive the wheel about a vertical steering axis. In these cases, the method may further include: for at least one wheel unit including the steering motor, positioning the wheel of the wheel unit in a steering position such that the wheel's direction of travel is substantially laterally or laterally to the remote direction. Thus, when more than two steerable wheel units are available, at least one wheel can be positioned in this manner. This provides greater robustness to changes in the direction of the applied force.

[0028] At least one wheel unit including the steering motor can be an intermediate wheel unit as viewed from the remote point. Therefore, the two wheels that produce the widest span toward the remote point can be oriented such that these wheels provide an ICR coinciding with the remote point, while a third intermediate wheel is positioned such that its direction of travel is substantially lateral to or laterally to the remote direction. Alternatively or additionally, at least one wheel unit including the steering motor can be the wheel unit furthest from the remote point.

[0029] Providing support points may include receiving a selection of support points from the user via a programming device. Providing application loads may include receiving a selection of application loads from the user via a programming device. The programming device may be, for example, a teach pendant unit (TPU). One or more selections by the user may be transmitted wirelessly or via a control cable to the AGV's control system.

[0030] Providing application load can include determining the application load using one or more sensors on the AGV. Therefore, the application load can originate, for example, from the execution of the AGV control program. In this case, the application load is the load actually acting on the AGV. Examples of such loads include loads arising from the AGV's interaction with its environment (e.g., physical contact with objects) and loads arising from the movement of the AGV's manipulators relative to a supporting structure. In any case, such application loads can be determined by one or more sensors on the AGV.

[0031] The method may further include: providing an AGV control program that includes at least one movement instruction for the AGV. In these cases, providing the application load may include: determining the application load based on the AGV control program. Therefore, the application load may originate, for example, from the AGV control program itself, e.g., before the execution of the AGV control program. In this case, the application load is the load estimated to act on the support structure when the AGV control program is executed.

[0032] However, the application load may include forces or torques that do not necessarily originate from the AGV control program or the execution of the AGV control program, such as forces or torques originating from a human pushing the AGV and that can be sensed by one or more sensors of the AGV.

[0033] According to a second aspect, an Automated Guided Vehicle (AGV) is provided, comprising a support structure; at least three wheel units, each wheel unit including a wheel rotatable about a horizontal wheel axis; wherein for at least two of the wheel units, the wheel unit includes a steering motor arranged to drive the wheel about a vertical steering axis; and a control system including at least one data processing device and at least one memory storing at least one computer program, the at least one computer program including program code, which, when executed by the at least one data processing device, causes the at least one data processing device to provide a support point associated with the support structure; provide an application load associated with the support structure, the application load including an application force; represent the application load by a remote force acting at a remote point horizontally offset from the support point and acting in a horizontal remote direction transverse to the offset line between the support point and the remote point; and for at least two of the wheel units including the steering motor, command to position each wheel in a steering position such that the instantaneous center of rotation (ICR) of each wheel substantially coincides with or is coincident with the remote point. The AGV of the second aspect can be any type combined with that described in the first aspect, or vice versa.

[0034] For at least three wheel units in a wheel unit, the wheel unit may include a steering motor arranged to drive the wheels about a vertical steering axis. In these cases, at least one computer program may include program code that, when executed by at least one data processing device, commands the at least one data processing device, for at least one wheel unit including the steering motor, to position the wheels of the wheel unit in a steering position such that the direction of travel of the wheels is laterally to the remote direction.

[0035] At least one wheel unit, including the steering motor, can be an intermediate wheel unit as viewed from a remote point.

[0036] At least one wheel unit among the wheel units including the steering motor can be the wheel unit furthest from the remote point.

[0037] Providing support points may include receiving the selection of support points from the user via a programming device.

[0038] Providing application load may include receiving a selection of application load from the user via a programming device.

[0039] An AGV may include one or more sensors. In these cases, providing the application load may include determining the application load through the control system and based on data from one or more sensors.

[0040] The at least one computer program may include program code that, when executed by at least one data processing device, causes the at least one data processing device to provide an AGV control program including at least one movement instruction for the AGV. In these cases, providing the application load may include determining the application load based on the AGV control program.

[0041] According to a third aspect, a system is provided that includes an AGV according to a second aspect and a programming device configured to communicate with control system signals. Attached Figure Description

[0042] Further details, advantages, and aspects of this disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0043] Figure 1 : A schematic side view of a system including an automated guided vehicle (AGV);

[0044] Figure 2 : A schematic cross-sectional side view illustrating an example of an AGV drive unit;

[0045] Figure 3 : A schematic top view of the AGV when an applied load is applied to its support structure;

[0046] Figure 4 : A schematic top view of the AGV when each wheel is positioned in a turning position such that the instantaneous center of rotation (ICR) coincides with the remote point;

[0047] Figure 5 : A schematic top view of an AGV when some of its wheels are positioned in the corresponding steering positions such that the ICR of these wheels coincides with the remote point;

[0048] Figure 6 : A schematic top view of an AGV when some of its wheels are positioned in the corresponding steering positions such that the ICR of these wheels coincides with the remote point;

[0049] Figure 7 : A schematic top view of an AGV when each wheel is positioned in a steering position such that the ICR of these wheels coincides with another remote point;

[0050] Figure 8 : A top view schematically illustrating another example of an AGV where some of its wheels are positioned in the appropriate turning positions such that the ICR of these wheels coincides with another remote point; and

[0051] Figure 9 This is a flowchart outlining the general steps of the method. Detailed Implementation

[0052] The following describes a method for controlling an Automated Guided Vehicle (AGV), the AGV itself, and a system including the AGV. The same or similar reference numerals will be used to denote the same or similar structural features.

[0053] Figure 1 A schematic side view of system 10 is shown. System 10 includes an automated guided vehicle (AGV) 12a. Therefore, system 10 can be referred to as an AGV system. Figure 1 In the diagram, AGV 12a is located on a horizontal ground surface 14, which is illustrated here as a floor. Figure 1 The human user 16 is also shown next to the AGV 12a.

[0054] AGV 12a includes a support structure 18, which is illustrated herein as a platform. This example AGV 12a also includes four wheel units 20a connected to the support structure 18. Figure 1 (Only two are visible in the image). Each wheel unit 20a includes a wheel 22a. Each wheel 22a is arranged to support the support structure 18 on the ground surface 14. The AGV 12a may also include a power source (not shown) (such as a battery) to power the wheel unit 20a.

[0055] Figure 1 Local coordinate system 24-1 and global coordinate system 24-2 are also shown. In this example, local coordinate system 24-1 is fixed relative to the support structure 18, and global coordinate system 24-2 is fixed relative to the ground surface 14.

[0056] The AGV 12a in this example also includes a manipulator 26, which is illustrated herein as a serial robotic arm programmable on at least three axes. The manipulator 26 is supported on a support structure 18 and is movable relative to the support structure 18.

[0057] The manipulator 26 in this example includes multiple joints 28, multiple actuators 30 for driving the respective joints 28, and multiple links, including a first link 32. The first link 32 is rotatable about a vertical axis relative to the support structure 18, as indicated by the corresponding arrow.

[0058] AGV 12a also includes an electronic control system 34 configured to control AGV 12a. This example control system 34 includes a data processing device 36 and a memory 38. A computer program is stored in the memory 38. The computer program includes program code that, when executed by the data processing device 36, causes the data processing device 36 to perform or command the execution of various steps as described herein. An AGV control program is also stored in the memory 38. When the AGV control program is executed, it controls AGV 12a to perform various tasks. The AGV control program may include movement instructions for AGV 12a. These movement instructions may include, when executed, instructions that cause AGV 12a to move on the ground surface 14 and, when executed, instructions that cause the manipulator 26 to move relative to the support structure 18 to perform tasks while the support structure 18 is moving and / or stationary.

[0059] The manipulator 26 in this example also includes one or more torque sensors 40 and one or more force sensors 42. Each torque sensor 40 is arranged to sense torque at the associated joint 28 and each force sensor 42 is arranged to sense force at the associated joint 28. Each torque sensor 40 and each force sensor 42 communicates signalingly with the control system 34. According to one example, the manipulator 26 includes a torque sensor 40 at each joint 28 and, for example, a force sensor 42 at the most distal joint 28. In any case, the control system 34 can be configured to determine any force or torque acting on the manipulator 26 based on signals from the one or more torque sensors 40 and the one or more force sensors 42.

[0060] However, one or more torque sensors 40 and one or more force sensors 42 are optional. For each trajectory of the manipulator 26 defined in the AGV control program, the resulting force and torque can also be calculated at one or more arbitrarily selected points on the manipulator 26 without the manipulator 26 executing the trajectory and without using one or more torque sensors 40 and one or more force sensors 42. Those skilled in the art will understand these calculations. In this regard, for example, reference can be made to WO2022171283 A1, the contents of which are incorporated herein by reference in their entirety.

[0061] The system 10 in this example also includes a programming device 44, which is illustrated herein as a teach pendant unit (TPU). User 16 can use the programming device 44 to create and / or modify AGV control programs. In this example, the programming device 44 is configured to communicate wirelessly with the control system 34.

[0062] Figure 2 A cross-sectional view schematically illustrating a specific example of the wheel unit 20a of AGV 12a. Figure 2Only a portion of the AGV 12a is shown in the illustration. This specific, non-limiting example of the AGV 12a includes four wheel units 20a of the same design.

[0063] The specific, non-limiting example of wheel unit 20a includes a driven steering member 46. Wheel 22a is rotatable about a wheel axis 48a to generate traction in a forward direction transverse to the wheel axis 48a. The driven steering member 46 and wheel 22a are rotatable about a steering axis 50a. The wheel axis 48a is perpendicular to the steering axis 50a. Furthermore, the wheel axis 48a intersects the steering axis 50a. Figure 2 In this configuration, wheel axis 48a is horizontal and steering axis 50a is vertical. Wheel axis 48a provides the first degree of freedom for wheel unit 20a. Steering axis 50a provides the second degree of freedom for wheel unit 20a.

[0064] Wheel unit 20a also includes a drive motor 52, which is illustrated herein as an electric synchronous drive motor. The drive motor 52 is arranged to rotatably drive wheel 22a about wheel axis 48a. In this example, the drive motor 52 is arranged to directly drive wheel 22a; that is, there is no intermediate gearing between the drive motor 52 and wheel 22a.

[0065] Wheel unit 20a also includes a steering motor 54, which is illustrated herein as an electric synchronous steering motor. The steering motor 54 is arranged to rotatably drive the driven steering member 46 about the steering axis 50a. The steering motor 54 and the drive motor 52 can each provide, for example, a torque of at least 5 Nm. Therefore, the wheel 22a in this example is a steerable, drivable wheel. Since the AGV 12a in this example includes at least two wheel units 20a, and here four wheel units 20a, the AGV 12a can perform omnidirectional movement of the support structure 18.

[0066] The steering motor 54 is arranged to directly drive the driven steering member 46, that is, there is no intermediate gear device between the steering motor 54 and the driven steering member 46. Figure 2 The example of the driven steering member 46 includes a support structure member 56 and two arm members 58 extending downward from the support structure member 56.

[0067] Wheel unit 20a also includes a steering shaft 60 and two steering bearings 62 for rotatably supporting the driven steering member 46 about steering axis 50a. The steering shaft 60 is rigidly connected to the support structure 18 of AGV 12a. Steering motor 54 includes a steering stator 64, a steering rotor 66, and a steering coil 68. The steering rotor 66 is disposed within the support structure component 56. The steering coil 68 is disposed on the steering stator 64. In this example, the support structure portion 56 is an integral part of the steering rotor 66.

[0068] Wheel unit 20a also includes a steering sensor device 70. The steering sensor device 70 determines the rotational position of the driven steering member 46, and therefore also the rotational position of wheel 22a about steering axis 50a. The steering sensor device 70 communicates with the control system 34. This example of the steering sensor device 70 includes an active component (in this document, a Hall effect steering sensor 72) and a passive component (in this document, a multi-pole steering encoder ring 74).

[0069] Wheel unit 20a also includes a steering circuit board 76. A Hall effect steering sensor 72 is mounted on the steering circuit board 76. A steering encoder ring 74 is connected to the driven steering member 46.

[0070] The drive motor 52 includes a wheel stator 78, a wheel rotor 80, and a wheel coil 82. The wheel stator 78 is arranged inside the wheel 22a. The wheel coil 82 is arranged on the wheel stator 78. The wheel unit 20a also includes a wheel axle 84 and two wheel bearings 86 for rotatably supporting the wheel 22a around the wheel axle 48a. The wheel axle 84 is rigidly connected to the arm portion 58 of the driven steering member 46.

[0071] Wheel unit 20a also includes wheel sensor device 88. Wheel sensor device 88 may be of the same type as steering sensor device 70. Wheel sensor device 88 determines the rotational position of wheel 22a about wheel axis 48a. Wheel sensor device 88 communicates signals with control system 34. The wheel sensor device 88 in this example includes an active part (constituted herein by a Hall effect wheel sensor 90) and a passive part (constituted herein by a multipole wheel encoder ring 92).

[0072] Wheel unit 20a also includes wheel circuit board 94. Hall effect wheel sensor 90 is mounted on wheel circuit board 94. Wheel encoder ring 92 is connected to wheel 22a.

[0073] Figure 3 A schematic top view of AGV 12a. Figure 3 In the diagram, AGV 12a is in a stationary state. As mentioned, the AGV 12a in this example includes four wheel units 20a, and each wheel unit 20a includes a wheel 22a. Therefore, the AGV 12a in this example includes a first wheel 22a-1, a second wheel 22a-2, a third wheel 22a-3, and a fourth wheel 22a-4. One, several, or all of the wheels in the first wheel 22a-1, the second wheel 22a-2, the third wheel 22a-3, and the fourth wheel 22a-4 may also be referred to by the reference numeral "22a".

[0074] Figure 3Each wheel 22a is indicated to have a forward direction 96a. The X1 / Y1 plane of the local coordinate system 24-1 can coincide with the plane including the wheel axis 48a and the forward direction 96a.

[0075] Position control of each wheel 22a can be performed, for example, via control system 34. When position control is performed on each wheel 22a, a position control loop can be used, wherein the measured position of each wheel 22a about its corresponding wheel axis 48a (e.g., determined based on signals from the corresponding wheel sensor device 88) is fed back and compared with a corresponding target position. For example, the gain of the position control loop can be set, for instance, to be relatively high, such that the compliance of the wheel 22a in the corresponding forward direction 96a is relatively low.

[0076] exist Figure 3 In this example, wheel 22a is configured according to its corresponding steering position. In this example, all wheels 22a are parallel, specifically parallel to the X1 direction of the local coordinate system 24-1. Figure 3 The wheel configuration in the diagram is an effective wheel configuration.

[0077] Figure 3 An example of an applied force 98a applied to the support structure 18 is also shown. The applied force 98a constitutes an example of an applied load according to this disclosure. The applied force 98a may be, for example, a force applied to the support structure 18 by the user 16. Figure 3 The wheel configuration in the middle is not optimal for handling the applied force 98a. When the applied force 98a is applied to the support structure 18, there is a risk that the support structure 18 will move away from its stationary position.

[0078] Figure 4 A schematic top view of AGV 12a. Figure 4 In another example of a wheel configuration, wheel 22a is positioned according to the instantaneous rotation center (ICR) 100a at the corresponding steering position. Furthermore, in Figure 4 In the middle, AGV 12a is in a stationary state.

[0079] In order to position wheel 22a relative to ICR 100a, the position of wheel 22a in local coordinate system 24-1 must be known. These positions of wheel 22a can be determined in various ways known to those skilled in the art, including by measurement.

[0080] Furthermore, this wheel configuration is also an effective wheel configuration. However, Figure 4 The wheel configuration in the middle provides more Figure 3The wheel configuration in the middle has a much higher resistance to the applied force 98a. In order to position the wheel 22a in a wheel configuration that provides the support structure 18 with respect to the applied force 98a, the following method can be performed.

[0081] Support points 102a associated with support structure 18 are provided in control system 34. Support point 102a is the point that will provide optimal stiffness for support structure 18. Support point 102a may, for example, be defined in the X1 / Y1 plane of local coordinate system 24-1.

[0082] Support point 102a can be selected arbitrarily. For example, user 16 can select support point 102a. To do this, user 16 can provide the selection of support point 102a via programming device 44. This selection can then be transmitted from programming device 44 to control system 34.

[0083] Alternatively, support point 102a can be pre-set or automatically set by the AGV control program. Support point 102a can, for example, be pre-set to be horizontally aligned with the geometric center point of support structure 18 or wheel 22a. Figure 4 In the middle, the support point 102a is horizontally aligned with the geometric center point of the support structure 18 and the geometric center point of the wheel 22a.

[0084] Then, an applied force 98a related to the support structure 18 is provided in the control system 34. For this purpose, the applied force 98a can be represented, for example, by a vector in the X1 / Y1 plane of the local coordinate system 24-1. The applied force 98a can be a force acting on the support structure 18 or an estimated force acting on the support structure 18. The applied force 98a can be provided in the control system 34 in various ways.

[0085] According to one example, the applied force 98a can be selected by user 16. To do this, user 16 can provide the selection of applied force 98a via programming device 44. This selection can then be transmitted from programming device 44 to control system 34.

[0086] According to another example, the applied force 98a can be determined based on the AGV control program before execution. In this case, the applied force 98a is the estimated force that will act on the support structure 18 in the future when the AGV control program is executed.

[0087] For the two examples above, the applied force 98a can be associated with a specific task in the AGV control program (such as a task performed by the manipulator 26 when the support structure 18 is stationary). Therefore, when the AGV control program is executed and this specific task is performed, the control system 34 can control the wheel unit 20a such that the wheel 22a adopts a wheel configuration that provides optimal stiffness for the support structure 18 relative to the support point 102a and the applied force 98a.

[0088] According to another example, the applied force 98a can be determined based on signals from one or more torque sensors 40, one or more force sensors 42, one or more steering sensor devices 70, and / or one or more wheel sensor devices 88. In this case, the applied force 98a is actually applied to the support structure 18, and the AGV 12a can respond to the applied force 98a by employing a wheel configuration that provides high stiffness at the support point 102a. Moreover, in this case, the applied force 98a can be, for example, a force arising from the movement of the manipulator 26 relative to the support structure 18, a force arising from the manipulator 26 contacting an external object, and / or a force arising from external parts (such as the user 16) acting on the support structure 18.

[0089] For any load including forces acting on the support structure 18, there exists a point where the load can be represented by pure force. Correspondingly, once the applied force 98a is provided, the applied force 98a is represented in the control system 34 by the remote force 104a acting at the remote point 106a.

[0090] exist Figure 4 In the example, the applied force 98a acting on the support structure 18 provides the same torque at the support point 102a in the horizontal plane as the remote force 104a acting at the remote point 106a. Therefore, the remote point 106a is horizontally offset from the support point 102a and acts in a horizontally remote direction 108a transverse to the offset line 110a between the support point 102a and the remote point 106a. Figure 4 In the example, the remote direction 108a is also the direction in which the applied force 98a acts. The wheel axis 48a, the forward direction 96a, the support point 102a, and the remote point 106a are located in a common horizontal plane.

[0091] In this example, the control system 34 then controls all wheels 22a to adopt the corresponding steering positions so that ICR 100a coincides with the remote point 106a. For this purpose, the control system 34 can use inverse kinematics to determine the corresponding steering positions. In this wheel configuration, the wheel axis 48a of each wheel 22a passes through the remote point 106a. This provides a wheel configuration that resists the applied force 98a very efficiently and provides optimal stiffness of the support structure 18 relative to the support point 102a. Therefore, the support structure 18 can resist the applied force 98a more efficiently without moving relative to the ground surface 14. As a result, the productivity of the manipulator 26 can be increased, and the manipulator 26 can perform challenging additional manipulator tasks.

[0092] AGV 12a may not include any dedicated brakes for braking AGV 12a. Instead, braking in a stationary state can be performed by various wheel configurations as described herein. If the applied load consists only of torque, then wheel 22a can be positioned in an X-shape, as taught in WO 2020259830 A1.

[0093] Figure 5 A schematic top view of AGV 12a is shown. The main description will be relative to... Figure 4 The differences. Figure 5 In this configuration, the first wheel 22a-1 and the fourth wheel 22a-4 are positioned at their respective turning points, such that the ICR 100a of these wheels 22a coincides with the remote point 106a. On the other hand, the second wheel 22a-2 and the third wheel 22a-3 are positioned laterally to their ICR orientation, i.e., such that their forward direction 96a intersects with ICR 100a. Figure 5 The wheel configuration provided by wheel 22a is invalid. The wheelset including first wheel 22a-1 and fourth wheel 22a-4 spans the widest angle relative to the remote point 106a, and is therefore the wheelset that helps to provide the highest stiffness at the support point 102a.

[0094] In the same example, AGV 12a will exhibit rigid behavior relative to the applied force 98a. However, if the direction of the applied force 98a were to change, the positioning of the second wheel 22a-2 and the third wheel 22a-3 would increase the stiffness. Therefore, the second wheel 22a-2 and the third wheel 22a-3 provide redundancy to the braking of AGV 12a. Figure 5 In the middle, the second round 22a-2 is furthest from the remote point 106a. Moreover, from the perspective of the remote point 106a, the second round 22a-2 and the third round 22a-3 are intermediate rounds 22a. That is to say, from the perspective of the remote point 106a, the second round 22a-2 and the third round 22a-3 are located between the first round 22a-1 and the fourth round 22a-4.

[0095] Figure 6A schematic top view of AGV 12a is shown. The main description will be relative to... Figure 4 and Figure 5 The differences. Figure 6 In this example, the first wheel 22a-1, the third wheel 22a-3, and the fourth wheel 22a-4 are positioned at their respective turning positions, such that the ICR 100a of these wheels 22a coincides with the remote point 106a. Only the second wheel 22a-2 is positioned laterally to its ICR orientation, i.e., such that its forward direction 96a intersects with ICR 100a. Furthermore, by… Figure 6 The wheel configuration provided by wheel 22a is invalid. The second wheel 22a-2 is furthest from the remote point 106a. Viewed from the remote point 106a, the second wheel 22a-2 is also an intermediate wheel relative to the first wheel 22a-1 and the third wheel 22a-3. Furthermore, in this example, AGV 12a will exhibit rigid behavior relative to the applied force 98a. Moreover, the positioning of the second wheel 22a-2 increases stiffness even when the direction of the applied force 98a should change.

[0096] Figure 7 A schematic top view of AGV 12a and an applied force 98b acting on the support structure 18 are shown. The applied force 98b is another example of an applied load according to this disclosure. Figure 7 The special case is illustrated when the applied force 98b acts along a line passing through the support point 102a. Therefore, the applied force 98b does not induce any torque at the support point 102a. When the applied force 98b is represented by a remote force 104b acting at a remote point 106b horizontally offset from the support point 102a and in a horizontal remote direction 108b, the remote direction 108b also passes through the support point 102a. In this case, the remote point 106b can be located anywhere along the remote direction 108b, as indicated by arrow 112. As the distance between the support point 102a and the remote point 106b increases, the stiffness increases, but the resistance to changes in the direction of the applied force 98b decreases, and vice versa. In these cases, the distance between the support point 102a and the remote point 106b can be, for example, preset to be a distance greater than the minimum distance between the two wheels in wheel 22a and less than the maximum distance between the two wheels in wheel 22a, such as being preset to be the average of these two distances.

[0097] In all cases, each wheel 22a is positioned at the corresponding steering position such that the ICR 100b of these wheels 22a coincides with the remote point 106b. This provides Figure 7 The wheel configuration shown is an effective wheel configuration. Furthermore, in this example, AGV 12a will exhibit rigid behavior relative to the applied force 98a.

[0098] Figure 8A schematic top view of AGV 12b according to yet another example. Figure 1 System 10 may alternatively include AGV 12b. The AGV 12b in this example includes... Figure 2 The two wheel units 20a shown are of the type shown. Therefore, the AGV 12b includes a first wheel 22a-1 and a second wheel 22a-2.

[0099] The AGV 12b in this example also includes a first wheel 22b-1 and a second wheel 22b-2, which are illustrated here as swivel casters. Swivel casters are an example of non-drive wheels. One or both wheels 22b-1 and 22b-2 may also be referred to using the reference numeral "22b". Although non-driveable, each wheel 22b in this example includes a forward direction 96b and is capable of rotating about a wheel axis 48b and a steering axis 50b.

[0100] Figure 8 The application force 98c and torque 114 are also shown. The application force 98c and torque 114 together constitute another example of the application load according to this disclosure. The application force 98c is illustrated here as the force acting on the actuator 26. The torque 114 is illustrated here as the torque due to the first link 32 relative to the support structure 18. Figure 8 The reaction torque that acts on the first link 32 of the manipulator 26 due to the clockwise rotation of the lever 26.

[0101] Figure 8 Another example of support point 102b is shown. In this example, support point 102b is centered relative to the first link 32, which is horizontally offset from the geometric center of the support structure 18. Therefore, optimal stiffness will be provided in the first link 32.

[0102] According to this method, support point 102b is set in control system 34, for example, by user 16 or by control system 34. Then, an applied load including applied force 98c and torque 114 related to support structure 18 is provided in control system 34, for example, by selection from user 16, by determination based on the AGV control program before execution, or based on calculations from signals from one or more torque sensors 40, one or more force sensors 42, one or more steering sensor devices 70, and / or one or more wheel sensor devices 88.

[0103] Furthermore, the applied load is represented by a remote force 104c, which acts at a remote point 106c that is horizontally offset from the support point 102c and in a horizontal remote direction 108c transverse to the offset line 110c between the support point 102b and the remote point 106c. Figure 8 It can be concluded that the remote force 104c provides the same torque around the support point 102c as the combination of the applied force 98c and the torque 114. Therefore, the magnitude of the remote force 104c is greater than the magnitude of the applied force 98c.

[0104] Then, all wheels 22a are controlled to be positioned at their respective steering positions such that the ICR 100c of these wheels 22a coincides with the remote point 106c. Therefore, optimal stiffness is provided at the center of the first link 32. Since wheels 22b are not steerable, they are positioned at random steering positions. Figure 8 In the examples 22a and 22b, wheels provide another example of a wheel configuration that is an invalid wheel configuration.

[0105] like Figure 8 As illustrated, the remote force 104c is in equilibrium with the first lateral force 116a of the first wheel 22a-1 and the second lateral force 116b of the second wheel 22a-2. The first lateral force 116a and the second lateral force 116b act only parallel to the corresponding wheel axis 48a and only laterally to the corresponding forward direction 96a. As a result, no torque is applied to the drive motor 52 due to the applied load. Figure 8 The method according to this disclosure is particularly advantageous when the AGV 12b includes only two steerable wheels 22a.

[0106] Figure 9 This is a flowchart outlining the general steps of a method for controlling automated guided vehicles (AGVs) 12a; 12b. AGVs 12a; 12b include a support structure 18 and at least three wheel units 20a; 20b, each wheel unit 20a; 20b including wheels 22a; 22b rotatable about horizontal wheel axes 48a; 48b. For at least two of the wheel units 20a, each wheel unit 20a includes a steering motor 54 arranged to drive the wheels 22a about a vertical steering axis 50a.

[0107] The method includes: providing support points 102a and 102b related to the support structure 18 in S10. The method further includes: providing an applied load related to the support structure 18 in S12, the applied load including applied forces 98a and 98c. The method further includes: representing the applied load in S14 by remote forces 104a and 104c, the remote forces 104a and 104c acting at remote points 106a and 106c horizontally offset from the support points 102a and 102b, and acting in a horizontal remote direction 108a and 108c transverse to the offset line 110a and 110c between the support points 102a and 102b and the remote points 106a and 106c. The method further includes positioning each wheel 22a in a steering position for at least two wheel units 20a, including the steering motor 54, such that the instantaneous rotation center (ICR) 100a; 100c of each wheel 22a substantially coincides with the remote point 106a; 106c.

[0108] For at least three wheel units 20a, each wheel unit 20a includes a steering motor 54 arranged to drive wheels 22a about a vertical steering axis 50a. In these cases, the method may further include: for at least one wheel unit 20a including the steering motor 54, positioning the wheel 22a of the wheel unit 20a in a steering position S18 such that the forward direction 96a of the wheel 22a is substantially transverse to the remote direction 108a; 108c.

[0109] The provision of support points 102a and 102b S10 may include receiving selection of support points 102a and 102b from user 16 via programming device 44 S20.

[0110] The provision of application load S12 may include receiving the selection of application load from user 16 via programming device 44 S22.

[0111] The provision of application load S12 may include: determining the application load S24 using one or more sensors 40, 42, 70, 88 of AGV 12a; 12b.

[0112] The method may further include: providing an S26 AGV control program, which includes at least one movement instruction for AGVs 12a and 12b. In these cases, providing the S12 application load may include: determining the S28 application load based on the AGV control program.

[0113] Although this disclosure has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to what has been described above. For example, it should be understood that the dimensions of the various parts may vary as needed. Therefore, the invention is intended to be limited only by the scope of the appended claims.

Claims

1. A method for controlling an automated guided vehicle (AGV) (12a; 12b), the AGV (12a; 12b) comprising a support structure (18) and at least three wheel units (20a; 20b), each wheel unit (20a; 20b) comprising a wheel (22a; 22b) capable of rotating about a horizontal wheel axis (48a; 48b); For at least two of the wheel units (20a), each wheel unit (20a) includes a steering motor (54) arranged to drive the wheel (22a) about a vertical steering axis (50a); and The method includes: - Provide (S10) support points (102a) associated with the support structure (18); 102b）； - Provide (S12) an application load associated with the support structure (18), the application load including application forces (98a; 98c). - The application load (S14) is represented by a remote force (104a; 104c), which acts at a remote point (106a; 106c) that is horizontally offset from the support point (102a; 102b) and acts in a horizontal remote direction (108a; 108c) transverse to the offset line (110a; 110c) between the support point (102a; 102b) and the remote point (106a; 106c); as well as - For at least two wheel units (20a) of the wheel unit (20a) including the steering motor (54), each wheel (22a) is positioned (S16) in a steering position such that the instantaneous rotation center ICR (100a; 100c) of each wheel (22a) substantially coincides with the remote point (106a; 106c).

2. The method according to claim 1, wherein for at least three wheel units (20a) of the wheel units (20a), each wheel unit (20a) includes a steering motor (54) arranged to drive the wheel (22a) about a vertical steering axis (50a); and wherein the method further comprises: For at least one of the wheel units (20a) including the steering motor (54), the wheel (22a) of the wheel unit (20a) is positioned (S18) in a steering position such that the forward direction (96a) of the wheel (22a) is substantially transverse to the remote direction (108a; 108c).

3. The method according to claim 2, wherein, viewed from the remote point (106a; 106c), at least one wheel unit (20a) of the wheel unit (20a) including the steering motor (54) is the intermediate wheel unit (20a).

4. The method according to claim 2 or 3, wherein at least one wheel unit (20a) of the steering motor (54) is the wheel unit (20a) that is furthest from the remote point (106a; 106c).

5. The method according to any one of the preceding claims, wherein the support point (102a; The provision (S10) of 102b) includes: Receive (S20) information from user (16) on the support point (102a) via programming device (44); The choice of 102b).

6. The method according to any one of the preceding claims, wherein the provision of the application load (S12) comprises: The user (16) receives (S22) the selection of the application load via the programming device (44).

7. The method according to any one of the preceding claims, wherein the provision of the application load (S12) comprises: The application load is determined (S24) by using one or more sensors (40, 42, 70, 88) of the AGV (12a; 12b).

8. The method according to any one of the preceding claims further comprises: Provide (S26) an AGV control program, the AGV control program including at least one movement instruction for the AGV (12a; 12b), wherein the provision (S12) of the application load includes: determining (S28) the application load based on the AGV control program.

9. An automated guided vehicle (AGV) (12a; 12b), said AGV (12a; 12b) comprising: - Support structure (18); -At least three wheel units (20a; 20b), each wheel unit (20a; 20b) includes wheels (22a; 22b) rotatable about a horizontal wheel axis (48a; 48b), wherein for at least two wheel units (20a) of the wheel units (20a), the wheel unit (20a) includes a steering motor (54) arranged to drive the wheel (22a) about a vertical steering axis (50a); and - A control system (34) comprising at least one data processing device (36) and at least one memory (38), wherein at least one computer program is stored on the at least one memory (38), the at least one computer program comprising program code, wherein the program code, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to: - Provide (S10) support points (102a; 102b) associated with the support structure (18); - Provide (S12) an application load associated with the support structure (18), the application load including application forces (98a; 98c). - The application load (S14) is represented by a remote force (104a; 104c), which acts at a remote point (106a; 106c) that is horizontally offset from the support point (102a; 102b) and acts in a horizontal remote direction (108a; 108c) transverse to the offset line (110a; 110c) between the support point (102a; 102b) and the remote point (106a; 106c); as well as - For at least two wheel units (20a) of the wheel unit (20a) including the steering motor (54), the command positions (S16) each wheel (22a) in a steering position such that the instantaneous rotation center ICR (100a; 100c) of each wheel (22a) substantially coincides with the remote point (106a; 106c).

10. The AGV (12a; 12b) according to claim 9, wherein for at least three wheel units (20a) of the wheel units (20a), the wheel unit (20a) includes a steering motor (54) arranged to drive the wheel (22a) about a vertical steering axis (50a); and wherein the at least one computer program includes program code that, when executed by the at least one data processing device (36), commands the at least one data processing device (36) to: for at least one wheel unit (20a) including the steering motor (54), position (S18) the wheel (22a) of the wheel unit (20a) in a steering position such that the forward direction (96a) of the wheel (22a) is transverse to the remote direction (108a; 108c).

11. The AGV (12a; 12b) according to claim 10, wherein, as viewed from the remote point (106a; 106c), at least one wheel unit (20a) of the wheel unit (20a) including the steering motor (54) is an intermediate wheel unit (20a).

12. The AGV (12a; 12b) according to claim 10 or 11, wherein at least one wheel unit (20a) of the wheel unit (20a) including the steering motor (54) is the wheel unit (20a) furthest from the remote point (106a; 106c).

13. The AGV (12a; 12b) according to any one of claims 9 to 12, wherein the provision (S10) of the support point (102a; 102b) comprises: Receive (S20) information from user (16) on the support point (102a) via programming device (44); The choice of 102b).

14. The AGV (12a; 12b) according to any one of claims 9 to 13, wherein the provision of the application load (S10) comprises: The user (16) receives (S22) the selection of the application load via the programming device (44).

15. The AGV (12a; 12b) according to any one of claims 9 to 14, wherein the AGV (12a; 12b) comprises one or more sensors (40, 42, 70, 88), and wherein the provision of the application load (S12) comprises: The application load is determined (S24) by the control system (34) and based on data from the one or more sensors (40, 42, 70, 88).

16. The AGV (12a; 12b) according to any one of claims 9 to 15, wherein the at least one computer program includes program code that, when executed by the at least one data processing device (36), causes the at least one data processing device (36) to provide (S26) an AGV control program, the AGV control program including at least one movement instruction for the AGV (12a; 12b), wherein the provision of the application load (S12) includes: The application load is determined (S28) based on the AGV control program.

17. A system (10) comprising an AGV (12a; 12b) according to any one of claims 9 to 16 and a programming device (44) configured to communicate signalally with the control system (34).

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