Stability of mobile manipulators by adjusting center of mass
By calculating the ZMP trajectory and adjusting the manipulator arm and center of mass, the stability problem of the mobile manipulator in a confined space was solved, enabling stable movement and efficient operation in complex environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ABB (SCHWEIZ) AG
- Filing Date
- 2023-11-08
- Publication Date
- 2026-05-29
AI Technical Summary
Mobile manipulators face stability issues when operating in confined spaces, especially under high dynamic forces, where they are prone to tipping over, and existing technologies struggle to maintain stability effectively.
By determining the current configuration and desired trajectory of the mobile manipulator, the zero-movement point (ZMP) trajectory is calculated, and the manipulator arm and center of mass are adjusted to align the current ZMP trajectory with the desired ZMP trajectory, ensuring the manipulator remains stable during movement.
It enables stable movement of the manipulator in complex environments, avoids tipping over, and improves the efficiency and safety of the manipulator in confined spaces.
Smart Images
Figure CN122121986A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for controlling a mobile manipulator, a mobile manipulator, a computer program product, and a computer-readable medium. Background Technology
[0002] In recent years, the automation industry has increasingly focused on automation applications in industries with confined spaces. These applications typically consist of a combination of transport tasks in laboratory environments and pick-and-place tasks in different workplaces. One type of robot proposed to meet these needs is the mobile manipulator. It combines a mobile base with an attached manipulator. Due to the limited space in laboratory environments, the size requirements for these robots are becoming increasingly stringent. The robot's footprint is a particular optimization focus. Common manipulators often consist of a bulky, large base, which can be a disadvantage when the robot needs to operate in confined spaces. In addition to the robot's size, the total time required for the robot to perform a task must also be continuously reduced. This requirement necessitates higher acceleration for the mobile base when navigating and performing pick-and-place tasks. The resulting challenge is ensuring the robot remains stable and, for example, does not tip over. Stability issues can arise with higher dynamic forces, further increasing the challenge of ensuring robot stability.
[0003] Therefore, sophisticated methods are needed to prevent instability of the motion controller. Summary of the Invention
[0004] This invention achieves its objectives according to the independent claims. Preferred embodiments of the invention are provided in the dependent claims, the specification, and the accompanying drawings.
[0005] The present invention relates to a method for controlling a mobile manipulator, the mobile manipulator comprising a manipulator base and at least one manipulator arm.
[0006] The method includes determining the current configuration of the mobile manipulator, which includes manipulator arm configuration and manipulator base configuration.
[0007] The method includes the step of determining the desired movement trajectory of the motion manipulator.
[0008] The method includes the step of determining the current zero-movement point (ZMP) trajectory based on the current configuration of the mobile manipulator and the desired movement trajectory, the ZMP trajectory including the location of one or more current ZMPs of the mobile manipulator.
[0009] The method includes the step of determining the desired ZMP trajectory of the mobile manipulator, wherein each ZMP is located within a support polygon of the manipulator base.
[0010] The method includes the step of adjusting the motion manipulator so that the current ZMP trajectory corresponds to the desired ZMP trajectory.
[0011] In the method according to the invention, the step of adjusting the moving manipulator includes adjusting the center of gravity of the moving manipulator, and adjusting the center of gravity includes adjusting the configuration of the manipulator arm.
[0012] Therefore, the present invention provides an improved method for stabilizing a mobile manipulator during movement along dissimilar paths, which ensures that the mobile manipulator remains stable and does not overturn during movement.
[0013] A mobile manipulator can be understood as any kind of mobile robot. In this context, a "mobile" or "possibly mobile" manipulator can be understood as one that allows the manipulator to occupy different positions or locations on the ground. The position of the mobile manipulator can be changed accordingly. For example, a mobile manipulator can move on its own, or be moved from a starting point to a destination by a corresponding device via a predetermined, different travel path.
[0014] The manipulator arm can be any type of robotic arm. It may include multiple interconnected elements and a movable base to form a kinematic chain. The links of such a manipulator arm can be connected via appropriate joints, which, for example, allow rotational motion or linear translation. However, it should be understood that a manipulator arm may also consist of only a single rigid element linked to the manipulator base. The manipulator arm can be programmable to allow for corresponding movements to perform different tasks. Furthermore, more than one manipulator arm may be provided.
[0015] The manipulator base essentially defines the core of the mobile manipulator, to which the manipulator arm is attached. The manipulator base may house the corresponding propulsion or control devices (such as a power supply, one or more motors, and / or computing devices) and may be enclosed in a housing to protect the internally arranged mobile manipulator components from negative influences such as dust and moisture. The manipulator base may define a support polygon. The support polygon can be a surface area on the ground that supports or carries the mobile manipulator. The support polygon may include three, four, or more sides, or may have a circular, elliptical, or any other two-dimensional shape.
[0016] The current configuration of the mobile manipulator may include information about the extent of extension and / or weight of the corresponding parts of the mobile manipulator. For example, the current configuration may include information about the center of gravity of each component and / or the entire mobile manipulator. The manipulator arm configuration may include the extent of extension or orientation of the manipulator arm relative to the manipulator base, such as the rotation angle or extent of extension of the manipulator arm. The manipulator base configuration may include information about the weight or dimensions of the manipulator base, such as the dimensions of the lower surface of the manipulator base that may form a supporting polygon. Any suitable parameters related to the center of gravity of the mobile manipulator may be included.
[0017] The positioning of the manipulator arm attached to the manipulator base can be fixed or variable. The manipulator arm can be provided on any desired side of the base, such as the top, front, or rear side, or on one of the lateral sides of the manipulator. The manipulator arm configuration can include different positions and / or orientations of the manipulator arm in space, such as arm posture. The manipulator arm configuration can include the rotational position of the manipulator arm or the extent of extension of the manipulator arm, for example, beyond the extent of extension of the manipulator base. Accordingly, the manipulator base configuration can include the spatial extent of extension and weight or weight distribution of the manipulator base.
[0018] The desired movement trajectory can be the path or track along which the mobile manipulator moves on the ground. Therefore, the desired movement trajectory can be provided on a substantially horizontal two-dimensional plane. The mobile manipulator can move along the desired movement trajectory from a starting position to an intermediate or ending position on the ground. The desired movement trajectory can be based on one or more tasks that the mobile manipulator should perform, such as picking up an item at a first position and placing the item at a second position. The movement trajectory can include one or more linear or curved movements, or any other arbitrary geometric movement on the ground between the starting and ending positions. The desired movement trajectory can include intermediate positions where the mobile manipulator can change its direction of movement. For example, the mobile manipulator can pick up an item at the starting position, move along the desired movement trajectory to the ending position, and place the item at the ending position. Accordingly, the mobile manipulator can continue to a third point (where it may or may not pick up the same or different item), and / or can return to its starting position. During movement along certain segments of the desired movement trajectory, the manipulator arm configuration can be substantially fixed or predetermined.
[0019] ZMP can be understood as the point where the reaction force between the manipulator and the ground produces no torque in the horizontal direction (i.e., in the direction of the plane in which the manipulator is moving). This can be in a direction approximately perpendicular to the direction of gravity. In general notation, the plane in which the manipulator is moving can extend in the xy direction, and the direction of gravity is in the z direction. ZMP can be considered as a horizontal torque.M x and M y The point where the sum of the points is zero. In other words, the ZMP can be defined as a reference point in the contact plane between the robot and the ground, where the horizontal component of the contact torque disappears. The ZMP of a mobile manipulator can depend on the manipulator arm configuration, the manipulator base configuration (e.g., the extent of extension of the support polygon), and the desired movement trajectory. One or more ZMPs can be determined or predicted for a mobile manipulator. In this disclosure, "determine" can also be understood as "predict". Any ZMP can depend on the configuration of the mobile base and the manipulator arm, for example, the weight and spatial extent of the components and their corresponding arrangement relative to each other.
[0020] Based on the current configuration of the mobile manipulator, the current ZMP trajectory can be determined or predicted. The current ZMP trajectory may correspond to one or more predicted ZMP positions of the mobile manipulator as it moves along the desired trajectory. The mobile manipulator is considered stable when its predicted current ZMP is within the supporting polygon. If one or more predicted current ZMPs of the mobile manipulator are arranged within the supporting polygon, the mobile manipulator can be stable, preventing overturning during movement along the desired trajectory. Therefore, in the method of the present invention, the mobile manipulator is preferably configured such that its ZMP is within the supporting polygon, thereby allowing for stable movement or stationary states.
[0021] Accordingly, given the desired trajectory of the mobile manipulator and (e.g., based on the arm configuration) taking into account the manipulator's configuration, the desired ZMP trajectory can be determined or predicted, which allows the mobile manipulator to move stably along the desired trajectory. Stable movement of the mobile manipulator can be achieved if the mobile manipulator moves along the desired trajectory and its ZMP corresponds to or is sufficiently close to the desired ZMP trajectory.
[0022] Therefore, the motion manipulator can be adjusted accordingly so that the current ZMP trajectory corresponds to or is close to the desired ZMP trajectory, thereby achieving stable movement of the motion manipulator. This adjustment can be performed before or during the movement of the motion manipulator. Different adjustments to the motion manipulator can be provided for different parts of the movement trajectory to obtain a stable configuration.
[0023] For example, if the ZMP is outside or too far from the desired ZMP trajectory, the locator may become unstable during movement. Therefore, appropriate adjustments to the locator (e.g., adjustments to the manipulator arm) can be determined and performed. For instance, the orientation or position of the manipulator arm can be adjusted from a first position to a second position, such that the locator's center of mass (and correspondingly its ZMP) can shift towards a more central position, thus providing enhanced stability. The locator is thus adjusted so that it may no longer be unstable as it moves along the desired trajectory.
[0024] The center of gravity can include the mass and dimensions of the entire moving manipulator, or it can include only the mass and dimensions of individual parts. For example, it can be the largest part, or the part that has the greatest impact on the position of the center of gravity of the moving manipulator.
[0025] In some examples, adjusting the mobile manipulator may include modifying the mobile manipulator (e.g., a specific rotation of the arm) to shift the center of gravity. Alternatively, adjusting the mobile manipulator may include adjusting the extension or reach of the manipulator arm relative to the manipulator base to prevent the mobile manipulator from tipping over. Further adjustments may consider adding, removing, or changing the position of the counterweight associated with the mobile manipulator.
[0026] In a preferred embodiment, the method includes the following steps: determining a critical point at which the mobile manipulator becomes unstable along a desired trajectory; and adjusting the center of mass of the mobile manipulator to counteract the determined instability, such that the mobile manipulator no longer becomes unstable at the critical point.
[0027] Therefore, an efficient and reliable method can be implemented to provide stable movement of a mobile manipulator, adaptable to any desired movement of the manipulator. Critical points can include points or locations along the movement trajectory where the center of mass may shift due to, for example, picking up additional weight or changing the orientation of the manipulator arm; or points where the manipulator accelerates, decelerates, or changes direction. Accordingly, the adjustment of the center of mass is sufficient to achieve stability of the manipulator along at least a portion (preferably the entire) of the movement trajectory (especially at critical points). The determination or prediction of critical points can include not only a single point but also portions of the manipulator's path or movement trajectory for which the center of mass is appropriately adjusted to allow stable movement.
[0028] In a preferred embodiment, the manipulator base includes one or more contact elements configured to contact the ground, and the manipulator is movable on the ground, wherein the contact elements preferably include one or more wheels.
[0029] Therefore, the manipulator base can be made to stand stably on the ground during movement or at rest. The manipulator base may include at least three contact elements. However, a different number of contact elements may also be provided. The supporting polygon may be defined accordingly by the area between the contact elements in contact with the ground. The ZMP (Zero-Mean Plane) can be adjusted accordingly so that it is substantially located within this contact area, thereby allowing the mobile manipulator to move or stand stably. Providing wheels allows the mobile manipulator to be easily steered along the ground in one or more desired directions. One or more wheels may be actively steered by the corresponding control and propulsion device of the mobile manipulator, or may be passively rotated. The invention is not limited to wheels, but may also include any type of steerable or non-steerable element that allows the mobile manipulator to move on the ground.
[0030] In a preferred embodiment, the step of determining the desired trajectory of the mobile manipulator includes determining the movement path of the mobile manipulator and / or determining the acceleration of the mobile manipulator.
[0031] Therefore, one or more movement paths or accelerations of the manipulator can be considered to adjust the manipulator. Acceleration along the entire path can be defined and known in advance, which helps in adjusting the manipulator to achieve stability. However, other parameters, such as the manipulator's speed (e.g., maximum speed), can also be considered in advance and can be considered as known beforehand. For example, each parameter can be considered as fixed to a certain value, such as a minimum or maximum value.
[0032] In a preferred embodiment, the step of adjusting the center of mass of the mobile manipulator includes adjusting the configuration of the manipulator arm to one or more manipulator arm configurations, wherein preferably the manipulator arm is moved from one manipulator arm configuration to another manipulator arm configuration to adjust the center of mass of the mobile manipulator.
[0033] Therefore, the center of mass of the mobile manipulator can be easily adjusted for stability, for example, without the need for additional counterweights. This adjustment can include iteratively moving the manipulator arm to one or more different positions. This adjustment can include moving the manipulator arm into one or more fixed arm configurations. For adjustment, the trajectory or path of the mobile manipulator and the acceleration along said path can be known. Appropriate fixed arm configurations (which may be predefined for the entire path or one or more portions of the path) can be considered for determining or calculating the ZMP of the mobile manipulator. Adjustment of the center of mass can be performed during the movement of the mobile manipulator, or it can be performed when the mobile manipulator is stationary, for example, before the mobile manipulator begins to move or between two critical points. The movement of the arm is preferably slow to avoid the influence of dynamic forces. Adjustment of the manipulator arm can be performed when the mobile manipulator is in a stable stationary position, for example, before it begins to move along the trajectory.
[0034] In a preferred embodiment, the motion manipulator includes one or more variable mass elements, and the step of adjusting the center of mass of the motion manipulator includes adjusting the variable mass elements.
[0035] Therefore, in addition to adjusting the arm configuration of the mobile manipulator, or as an alternative, the mobile manipulator can be adjusted, which can improve flexibility and expand the range of stability adjustments. Variable mass elements can be positioned at different locations on the mobile manipulator to influence and adjust its center of gravity. Variable mass elements can include fixed counterweights or can include variable counterweights (which can be adapted). Variable mass elements can be a single mass element or can include multiple mass elements (which can be individually adapted). Furthermore, multiple different counterweights can be provided depending on the adjustment needs of the mobile manipulator. Mass elements can be provided at any suitable location on the mobile manipulator, for example, on the outside of the housing, such as on the top side of the housing or inside it. Mass elements can be manually adjusted by the user or can be automatically adjusted to one or more positions. For example, mass elements can be appropriately adapted according to the weight or size of the mobile manipulator in a way that achieves appropriate stability of the mobile manipulator while avoiding unnecessary counterweight.
[0036] In a preferred embodiment, the variable mass element includes one or more external mass elements detachably disposed at the motion manipulator, and the step of adjusting the center of gravity of the motion manipulator includes adding to or removing the external variable mass element from the motion manipulator. Alternatively or additionally, the variable mass element includes one or more internal mass elements non-detachably disposed at different locations on the motion manipulator, and the step of adjusting the center of gravity of the motion manipulator includes changing the position of the internal variable mass element.
[0037] Therefore, it is possible to achieve specific, precise, and efficient adjustments to the center of mass.
[0038] An external mass element can be understood as a mass element that is not directly connected to the moving manipulator but can be added or removed as needed. For example, a tool or gripper positioned at the distal end of the manipulator arm (e.g., the tool center point) can grip a heavy object to adjust the center of gravity of the moving manipulator. If the manipulator picks up a certain weight during its task, the additional counterweight can be taken into account accordingly for adjusting the center of gravity. External mass elements can include any type of additional counterweight or mass block that can be easily added to or removed from the moving manipulator manually or automatically.
[0039] In contrast, an internal mass element can be understood as a mass element that is more or less directly connected to the moving manipulator. This can include mass elements that are fixedly or detachably arranged or mounted inside or outside the housing of the moving manipulator. For example, an internal mass element can be arranged at a corresponding guide rail on the moving manipulator to allow for simple and well-defined positioning of the counterweight.
[0040] The movement of internal and external mass elements can be sensed and controlled accordingly by a motion manipulator sensing and control device. Positioning of the internal and external mass elements can be performed along any desired direction. Movement of variable mass elements can be achieved by moving the mass elements relative to the motion manipulator along one or more predefined movement trajectories. Furthermore, combinations of external and internal mass elements can be provided, and adjustments to the center of mass of the motion manipulator can be performed accordingly based on individual or combined adjustments of the external and internal mass elements.
[0041] The present invention also relates to a mobile manipulator comprising a manipulator base and at least one manipulator arm, and a control device adapted to control the mobile manipulator according to the method of the present disclosure.
[0042] It should be noted that the above explanations of certain elements or advantages described with respect to the mobile manipulator control method of this disclosure apply accordingly to the mobile manipulator described herein. Therefore, a particularly stable mobile manipulator during movement can be provided. The control device can be arranged at the mobile manipulator, or can be at least partially arranged outside and away from the mobile manipulator. The control device may include suitable computing and control devices for controlling any element of the mobile manipulator, such as the orientation or extension degree of the manipulator arm and / or propulsion speed, acceleration, or wheel steering. The control device may include corresponding sensors or detectors to determine the position or movement of corresponding elements. The determination of any configuration of the mobile manipulator and / or the determination or prediction of any parameters (such as the current configuration of the mobile manipulator, the desired movement trajectory, the determination of ZMP, the current or desired ZMP trajectory, etc.) can be performed by a corresponding computing device, which may or may not be part of the mobile manipulator control device. The mobile manipulator may include one or more tools arranged at the distal end of the manipulator arm to perform corresponding manipulatory actions, such as picking up and lifting items and transporting and placing said items to different locations.
[0043] In a preferred embodiment, the manipulator base includes one or more contact elements configured to contact the ground, on which the manipulator is movable, wherein the contact elements are preferably formed of wheels.
[0044] Therefore, it is possible for the base of the mobile manipulator to stand particularly stably on the ground during movement or when stationary.
[0045] In a preferred embodiment, the manipulator arm can be adjusted to one or more manipulator arm configurations, wherein the manipulator arm is preferably movable from one manipulator arm configuration to another manipulator arm configuration to adjust the center of mass of the moving manipulator.
[0046] Therefore, by adjusting the center of gravity, the stability of the moving manipulator can be easily adjusted, for example, without the need for additional counterweights.
[0047] In a preferred embodiment, the motion manipulator further includes one or more variable mass elements that are adjustable to adjust the center of mass of the motion manipulator.
[0048] Therefore, a mobile manipulator can be provided that, in addition to adjusting the configuration of the mobile manipulator or as an alternative, the mobile manipulator can be adjusted, which improves flexibility and expands the range of stability adjustments.
[0049] In a preferred embodiment, the variable mass element includes one or more external mass elements detachably disposed at the moving manipulator for adjusting the center of gravity of the moving manipulator. Alternatively or additionally, the variable mass element may include one or more internal mass elements non-detachably disposed at different locations on the moving manipulator for adjusting the center of gravity of the moving manipulator.
[0050] Therefore, a motion manipulator can be provided that enables precise and efficient adjustment of the center of mass.
[0051] In a preferred embodiment, the mobile manipulator is an autonomous mobile manipulator robot, which preferably includes more than two steering wheels.
[0052] Therefore, a flexible and reliable autonomous mobile manipulator robot can be provided. This can include any type of manipulator robot, such as a mobile manipulator that can move on the ground. The robot's movement along the ground and the movement of the arms can be controlled fully or semi-automatically. At least two steering wheels can allow for particularly good control of movement on the ground. The wheels can be jointly or independently propulsive or steerable. The mobile manipulator robot can be an industrial robot, logistics robot, medical robot, laboratory robot, or any other type of robot operating in a suitable industrial, logistics, medical, or laboratory environment, which can perform the desired task using one or more manipulator arms arranged on a mobile manipulator base.
[0053] The present invention also relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to perform and / or control any of the methods described in this disclosure.
[0054] The features of the system according to the invention can be implemented by a suitable digital or computing device, which may include one or more computers, applications, and / or networks.
[0055] This method can be implemented at least partially by a computer, and can be implemented in software or hardware, or both. Furthermore, the method can be executed by computer program instructions running on a device that provides data processing capabilities.
[0056] The data processing device can be a suitable computing device such as an electronic control module, or it can be a distributed computer system. The data processing device or computer may each include one or more of a processor, memory, data interface, etc.
[0057] The present invention also relates to a computer-readable medium including instructions that, when executed by a computer, cause the computer to perform and / or control any of the methods described in this disclosure.
[0058] Any of a computer, computer program product, and / or computer-readable medium may be at least part of a mobile manipulator, or may be arranged remotely from a mobile manipulator.
[0059] The features and advantages outlined above in the context of systems and methods also apply to the computer program products and computer-readable media described herein. Similarly, any features and advantages described with respect to the methods of the invention also apply to the mobile manipulator of the invention, and vice versa.
[0060] Computer programs can be stored / distributed on suitable media (such as optical storage media or solid-state media) and can be provided together with other hardware or as part of hardware; however, they can also be distributed in other forms, such as via the Internet or other wired or wireless communication systems.
[0061] Further features, examples, and advantages will become apparent from the following detailed description and accompanying drawings of preferred embodiments. Attached Figure Description
[0062] To better understand the invention and illustrate its practicality, accompanying drawings are provided and referenced below. It should be understood that the drawings illustrate exemplary embodiments only and therefore do not limit the scope of the claimed invention. Identical or similar elements are indicated throughout the text by the same reference numerals. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0063] In the attached diagram,
[0064] Figure 1 The diagram schematically illustrates different configurations of the motion manipulator according to the present invention;
[0065] Figure 2 This is a flowchart illustrating a method for controlling a mobile manipulator according to the present invention;
[0066] Figure 3 This is a flowchart illustrating a method for controlling a mobile manipulator according to the present invention. Detailed Implementation
[0067] Figure 1A mobile manipulator 1 according to the invention is depicted. The mobile manipulator 1 includes a manipulator base 3 and a manipulator arm 5 attached to the top side of the base 3. It should be understood that in different embodiments, more than one manipulator arm 5 may be provided, and the position of one or more manipulator arms 5 may vary; for example, the manipulator arm 5 may be provided on the front, rear, or lateral side of the mobile manipulator 1. The mobile manipulator 5 is formed as a movable arm consisting of a plurality of arm elements linked together to allow flexible movement and extension or retraction of the arm. However, it should be understood that in different environments, a rigid manipulator arm may also be provided; for example, a rigid manipulator arm may consist of only one rigid arm element movably attached to the manipulator base 3. The manipulator arm 5 is hinged to the mobile base 3 at its proximal end, and includes a tool center point TCP 15 at its distal end. In the depicted embodiment, TCP 15 is formed as a gripper to allow gripping of external objects or loads. The manipulator base 3 includes a wheel-shaped contact element 9 for contact with the ground 11. Therefore, the mobile manipulator 1 can be moved along the ground 11. During the movement of the mobile manipulator 1, the manipulator arm 5 remains essentially fixed. However, different fixed arm positions can be provided along the movement trajectory. For example, when the mobile manipulator 1 moves along a specific movement trajectory comprising multiple tracks, different arm positions can be presented in the first movement path segment, as shown in the left sub-figure A. Correspondingly, different arm positions can be provided in the second movement path segment, as shown in the right sub-figure B. In sub-figure A, the mobile manipulator 1 moves to the left, as depicted by arrow 50. In sub-figure B, the mobile manipulator 1 moves to the right, as depicted by arrow 50. The mobile manipulator 1 can move along a predetermined movement trajectory.
[0068] The movable manipulator 1 also includes a mass element 13 disposed on the top surface of the manipulator base 3. However, in different embodiments of the invention, no additional mass element is provided. As shown, the mass element 13 may be located at different positions relative to the manipulator base 3. For example, as shown in sub-Figure A, the mass element 13 is disposed on the right side of the manipulator base 3, near the proximal end of the manipulator arm 5, and is attached to the manipulator base 3 at the proximal end. It should be understood that in different embodiments, more than one mass element 13 may also be provided, and the positions of one or more mass elements 13 may vary. Furthermore, as shown in sub-Figure B, the mass element 13 is disposed on the left side of the manipulator base 3, at a distance from the proximal end of the manipulator arm 5, to counteract the centroid offset caused by the depicted manipulator arm configuration. As shown in sub-Figures A and B, the movable arm manipulator arm 5 may have different orientations relative to the manipulator base 3.
[0069] The orientation of the manipulator arm 5 can be set and controlled by the control device 7 of the mobile manipulator. In the depicted embodiment, the control device 7 is arranged at the mobile manipulator 1. However, it should be understood that in different embodiments, the control device 7 may also be arranged at least partially outside or away from the mobile manipulator 1. The control device 7 may include suitable sensing, computing, and control devices for controlling elements of the mobile manipulator 1, such as the orientation of the manipulator arm 5 or the propulsion speed, acceleration, and direction of the wheel. Depending on the configuration of the manipulator arm 5, the center of mass of the mobile manipulator 1 will also change. For example, due to the manipulator arm configuration, the center of mass of the mobile manipulator 1 in sub-figure B is shifted to the right more than that in sub-figure A, because the manipulator arm 5 in sub-figure B extends further and is farther away from the manipulator base 3 compared to the configuration in sub-figure A. As mentioned above, the positioning of the mass element 13 can counteract this shift. In different embodiments, the center of mass can shift by simply changing the manipulator arm configuration (e.g., the position of the manipulator arm 5).
[0070] When the center of gravity shifts too much, the mobile manipulator 1 may become unstable, causing it to tip over. This can be counteracted, for example, by controlling the orientation of the manipulator arm 5 to one or more suitable positions. Therefore, when the mobile manipulator 1 moves along a predetermined trajectory (e.g., along disparate paths in industrial, research, or medical settings), the manipulator arm 5 can be controlled to assume different configurations according to the invention to maintain stability during movement. This can include a first arm configuration on a first travel path or segment, and a different second configuration on a second travel path or segment.
[0071] Furthermore, a computer program product 200 and a computer-readable medium 300 are also shown, each comprising instructions that, when executed by a computer 100, cause the computer 100 to perform and / or control the method described according to any embodiment of the invention, particularly... Figure 2 and Figure 3 The method is illustrated in the figure. In the depicted embodiment, computer 100, computer program product 200, and computer-readable medium 300 are depicted as external elements. However, it should be understood that in different embodiments, any one of computer 100, computer program product 200, and computer-readable medium 300 may be at least partially integrated into the mobile manipulator 1.
[0072] Figure 2A flowchart illustrating a method for controlling a mobile manipulator 1 according to an embodiment of the present invention is depicted. In step S1 of the depicted embodiment, a desired movement trajectory of the mobile base 3 or the mobile manipulator 1 is determined. In step S2 of the depicted embodiment, a desired ZMP trajectory of the mobile base 3 or the mobile manipulator 1 is selected or determined based on the desired movement trajectory. As shown in step S3, optimization criteria can be introduced to improve the overall performance of the mobile manipulator 1. Such optimization criteria can be any criteria applicable to optimizing the movement of the mobile manipulator, such as requiring the lowest possible acceleration or the highest possible speed, or requiring a reduction in the power consumption of the mobile manipulator 1. In step S4, which will be explained in more detail below, the ZMP trajectory is used as input to define the motion definition of the mobile manipulator 1 to utilize redundant degrees of freedom. These degrees of freedom can be used accordingly to maintain the current ZMP trajectory of the mobile manipulator 1 on the desired ZMP trajectory of the mobile manipulator 1.
[0073] Figure 3 A flowchart illustrating a method for controlling a mobile manipulator 1 according to an embodiment of the present invention is shown. As depicted, steps S1 to S3 are... Figure 2 Steps S1 to S3 correspond to each other, where the outputs of steps S1 to S3 form the inputs for subsequent steps. In the section labeled "Method"... Figure 3 In China, Figure 2 Step S4 is explained in more detail. Here, the output of step S2 is used as the input to step S5, where the current or actual ZMP trajectory of the mobile manipulator 1 is determined or predicted. Based on the determination result, in step S6, it is determined or predicted whether the current ZMP trajectory is a stable trajectory, i.e., the trajectory corresponds to or is close to the desired ZMP trajectory of the mobile base. If the answer is "yes", the trajectory is executed in step S7. If the answer is "no", points in the desired movement trajectory of the mobile manipulator 1 where the ZMP does not correspond to the desired ZMP trajectory are determined or predicted in step S8. In step S9, the end effector and / or manipulator arm and / or additional mass can be adjusted or moved accordingly, such that their positional changes offset the criticality of overturning or unstable movement of the mobile manipulator 1 at the defined point.
[0074] Therefore, by moving the manipulator arm 5, the center of mass of the moving manipulator 1 is adjusted accordingly to avoid instability at the calculated critical point. Then, in step S10, it is determined or predicted whether the movement limit of the manipulator arm or the added mass has been reached. If the answer is "no," the process returns to step S5, where the current ZMP trajectory of the moving manipulator 1 is determined or predicted based on the adjusted settings. If the answer is "yes," more added mass can be added to the moving manipulator to overcome instability. Then, the process returns to step S5, where the current ZMP trajectory of the moving manipulator 1 is determined or predicted based on the adjusted settings.
[0075] It should be understood that the method according to the present invention is not limited to the above-described order of method steps. On the contrary, the method steps may be provided in a different order, and one or more of the above-described method steps may be removed or more method steps may be added as needed.
[0076] List of reference numerals
[0077] 1. Mobile controller
[0078] 3. Control base
[0079] 5. Manipulator arm
[0080] 7. Control device
[0081] 9 Contact elements
[0082] 11 Ground
[0083] 13 Mass Components
[0084] 15. Tool center point
[0085] 50. Movement of the mobile base
[0086] 100 computers
[0087] 200 computer program products
[0088] 300 Computer-readable media
[0089] S1 to S11 Method Steps
Claims
1. A method for controlling a mobile manipulator (1), the mobile manipulator comprising a manipulator base (3) and at least one manipulator arm (5), the method comprising the steps of: Determine the current configuration of the mobile manipulator (1), the current configuration including the manipulator arm configuration and the manipulator base configuration; Determine the desired movement trajectory of the mobile manipulator (1); Based on the current configuration of the mobile manipulator (1) and the desired movement trajectory, determine the current ZMP trajectory of the mobile manipulator, including the positioning of one or more current zero movement points (ZMPs). Determine the desired ZMP trajectory of the mobile manipulator (1), wherein each ZMP is located within the support polygon of the manipulator base (3); Adjust the movement manipulator (1) so that the current ZMP trajectory corresponds to the desired ZMP trajectory; The step of adjusting the mobile manipulator (1) includes adjusting the center of mass of the mobile manipulator (1), and adjusting the center of mass of the mobile manipulator (1) includes adjusting the configuration of the manipulator arm.
2. The method according to the preceding claims, The method includes the following steps: Determine the critical point at which the motion manipulator (1) becomes unstable along the desired motion trajectory; and The centroid of the moving manipulator (1) is adjusted to counteract the determined instability, so that the moving manipulator (1) no longer becomes unstable at the critical point.
3. The method according to any one of the preceding claims, The manipulator base (3) includes one or more contact elements (9) configured to contact the ground (11), the mobile manipulator (1) being movable on the ground (11), and the contact elements (9) preferably including one or more wheels.
4. The method according to any one of the preceding claims, The step of determining the desired trajectory of the mobile manipulator (1) includes determining the movement path of the mobile manipulator (1) and / or determining the acceleration of the mobile manipulator (1).
5. The method according to any one of the preceding claims, The step of adjusting the center of mass of the moving manipulator (1) includes adjusting the configuration of the manipulator arm (5) to one or more manipulator arm configurations. Preferably, the manipulator arm (5) is moved from one manipulator arm configuration to another manipulator arm configuration to adjust the center of mass of the moving manipulator (1).
6. The method according to any one of the preceding claims, The moving manipulator (1) includes one or more variable mass elements (13), and the step of adjusting the center of mass of the moving manipulator (1) includes adjusting the variable mass elements (13).
7. The method according to claim 1, The variable mass element (13) includes one or more external mass elements (13) that can be detachably arranged at the moving manipulator (1), and the step of adjusting the center of mass of the moving manipulator (1) includes adding or removing the external variable mass element (13) to the moving manipulator (1), and / or The variable mass element (13) therein includes one or more internal mass elements (13) that can be non-removably arranged at different locations of the moving manipulator (1), and the step of adjusting the center of mass of the moving manipulator (1) includes changing the location of the internal variable mass element (13).
8. A mobile manipulator (1), comprising: The manipulator base (3) and at least one manipulator arm (5), and The control device (7) is adapted to control the mobile manipulator (1) according to any one of the preceding claims 1 to 7.
9. The mobile manipulator (1) according to the preceding claims. The manipulator base (3) includes one or more contact elements (9) configured to contact the ground (11), the mobile manipulator (1) being movable on the ground (11), wherein the contact elements (9) are preferably formed of wheels.
10. The mobile manipulator (1) according to any one of claims 8 or 9. The manipulator arm (5) is adjustable to one or more manipulator arm configurations, wherein the manipulator arm (5) is preferably movable from one manipulator arm configuration to another manipulator arm configuration to adjust the center of mass of the moving manipulator (1).
11. The mobile manipulator (1) according to any one of claims 8 to 10. The moving manipulator (1) further includes one or more variable mass elements (13) that are adjustable to adjust the center of mass of the moving manipulator (1).
12. The mobile manipulator (1) according to the preceding claims. The variable mass element (13) includes one or more external mass elements (13) that are detachably arranged at the moving manipulator (1) to adjust the center of mass of the moving manipulator (1); and / or The variable mass element (13) therein includes one or more internal mass elements (13) which are non-removably arranged at different locations of the moving manipulator (1) to adjust the center of mass of the moving manipulator (1).
13. The mobile manipulator (1) according to any one of claims 8 to 12. The mobile manipulator (1) is an autonomous mobile manipulator robot, preferably including more than two steerable wheels.
14. A computer program product (200) comprising instructions which, when executed by a computer (100), cause the computer (100) to perform and / or control the method according to any one of claims 1 to 7.
15. A computer-readable medium (300) comprising instructions which, when executed by a computer (100), cause the computer to perform and / or control the method according to any one of claims 1 to 7.