CN115816435A

CN115816435A - Robot carrying object and method for determining motion trail of robot carrying object

Info

Publication number: CN115816435A
Application number: CN202111111091.2A
Authority: CN
Inventors: 周诚; 雷茂霖; 郑宇�
Original assignee: Tencent Technology Shenzhen Co Ltd
Current assignee: Tencent Technology Shenzhen Co Ltd
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2023-03-21

Abstract

The present disclosure relates to a method of robot handling an object and a method of determining a motion trajectory of a robot handling object, which are capable of handling the object from a start position to a target position with a variable motion by means of pose adjustment of an operation part without fixed contact and relative motion of the operation part with the object to be handled. Furthermore, the disclosure also relates to a robot which is able to perform the above method in case the operating part is in non-fixed contact with the object to be operated, so that the robot is able to handle heavier objects at a faster speed.

Description

Robot carrying object and method for determining motion trail of robot carrying object

Technical Field

The present disclosure relates to the field of robots, and more particularly, to a method for a robot to carry an object, a method for determining a motion trajectory of a robot to carry an object, and a robot capable of performing the above methods.

Background

With the continuous development of technology in the field of robots, various types of robots such as industrial robots and service robots have been increasingly used in various technical fields such as smart agriculture, smart factories, and smart warehousing. In the above-described fields, it is possible to perform desired operations, such as acquisition, movement, placement, and the like of an operation object, on various objects in the above-described fields (for example, a workpiece to be transported in a smart factory; a smart logistics, goods in a smart warehouse field, and the like) by means of an appropriate operation section (for example, a robot arm having a mechanical gripper at a distal end) of a robot, so as to significantly improve the degree of automation and reduce the human resource cost.

Generally, an operation of a robot on an object may be classified into a fixed operation and a non-fixed operation. Here, the expression "fixed" means that the operation part of the robot is firmly and fixedly connected to the object. The operation in which the operation portion establishes a firm fixed connection with the object is a fixed operation, whereas the operation portion is an unfixed operation such as pushing, pulling, dragging, sliding, and hitting the object without establishing a fixed connection. For example, the fixed type operation is an operation for acquiring an object by an operation unit having an acquisition member capable of establishing a fixed connection with the object, such as a mechanical gripper or a controllable suction member. The anthropomorphic robot uses the tray to carry a plurality of stacked goblets, namely the anthropomorphic robot belongs to the non-fixed operation.

In the related art, there is a method in which a robot quickly conveys an object to be operated in a case where an operation part of the robot fixedly contacts the object to be operated. However, in the case where the operation portion of the robot is not fixedly in contact with the object to be operated, there is no disclosure of a method for quickly conveying the object by the robot.

Therefore, there is a need for a method of transporting an object by a robot, a method of determining a motion trajectory of a robot transporting an object, and a robot capable of performing the above methods, in a case where an operation part is non-fixedly connected to the object.

Disclosure of Invention

The present disclosure provides a method of robot handling an object and a method of determining a motion trajectory of a robot handling object, which are capable of handling the object from a start position to a target position with a variable motion by means of pose adjustment of an operation part without fixed contact and relative motion of the operation part with the object to be handled. Furthermore, the disclosure also relates to a robot which is able to perform the above method in case the operating part is in non-fixed contact with the object to be operated, so that the robot is able to handle heavier objects at a faster speed.

For example, the present disclosure provides a method of a robot handling an object, the robot having an operating part that is in non-stationary contact with the object, the method comprising: receiving a carrying instruction; determining a driving force of an operation unit based on the transport instruction; and driving the operation section with the determined driving force to adjust a posture in conveying the object such that the operation section conveys the object from a home position to a target position with a shift movement and the object and the operation section do not move relatively.

Furthermore, the present disclosure also provides a method of determining a motion trajectory of a robot carrying an object, the operating part being in non-fixed contact with the object and carrying the object from a start position to a target position in a variable speed motion, the method comprising: determining a motion trajectory of the operating part based on a control model, wherein the control model indicates: aiming at minimizing the movement time of the object from a starting position to a target position, determining the movement track of the operation part based on a dynamic model corresponding to the operation part, a dynamic model corresponding to the object and a stable grabbing constraint equation set, wherein the stable grabbing constraint equation set is related to the contact force provided by the operation part to the object and the gravity and the centrifugal force of the object.

Further, the present disclosure also provides a robot having: an operation portion that applies a supporting force and a frictional force to an object so that the object is carried from a start position to a target position in a shifting motion; a controller for controlling the operation section to adjust the pose, the controller being provided on the robot and configured to perform the above-described method.

The present disclosure also provides a computer-readable storage medium having stored thereon a handling instruction, which when executed by a controller implements the above method.

According to another aspect of the present disclosure, there is provided a computer program product or computer program comprising handling instructions stored in a computer readable storage medium. The controller of the robot reads the handling instructions from the computer readable medium, and the controller executes the handling instructions, so that the robot performs the method provided in the above aspects or various alternative implementations of the above aspects.

In summary, the present disclosure provides a method for a robot to transport an object. Wherein a contact force between an operating part and an object is changed by adjusting a posture of the operating part of the robot so that the object can be carried from a start position to a target position in a variable speed motion with the operating part in non-fixed contact with the object, thereby enabling the robot to carry a heavier object at a faster speed.

Further, the present disclosure provides a method of determining a motion trajectory of a robot handling object. Wherein the movement locus of the operation part is determined based on a control model so that, in the case where the operation part is in non-fixed contact with the object, the contact force provided to the object by the operation part and the centrifugal force of the object are changed by adjusting the position of the operation part, thereby enabling the robot to carry a heavier object at a faster speed.

Further, the present disclosure provides a robot that enables the robot to carry a heavier object at a faster speed by adjusting the posture of the operation portion of the robot, as described above.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings used in the description of the embodiments will be briefly introduced below. It is apparent that the drawings in the following description are only exemplary embodiments of the disclosure, and that other drawings may be derived from those drawings by a person of ordinary skill in the art without inventive effort.

Herein, in the drawings:

fig. 1 shows a schematic flow diagram of a method of robotic handling of objects according to the present disclosure;

fig. 2 shows a schematic view of an operating part of the robot in non-stationary contact with an object;

FIG. 3A shows a schematic diagram of one pose that can exist in a method of robotic handling of objects according to the present disclosure;

FIG. 3B is a schematic view showing a movement locus of an operation part and an object relating to the posture of FIG. 3A;

fig. 4A shows a schematic view of one pose that can exist in a method of robotic handling of objects according to the present disclosure;

fig. 4B shows a schematic diagram of a movement locus of an operation part and an object relating to the posture of fig. 4A;

fig. 5 shows schematic diagrams in a first phase and a second phase of a variable speed movement in a method of a robot handling objects according to the present disclosure;

FIG. 6 shows a schematic diagram of a friction cone of an object in a method of handling the object by a robot according to the present disclosure;

fig. 7 illustrates an example of a movement locus of an object and an operation part in the method of the robot handling the object according to the present disclosure;

fig. 8 shows a schematic flow chart of a method of determining a motion trajectory of an operating part of a robot according to the present disclosure;

fig. 9 shows a schematic block diagram of a robot according to the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present disclosure more apparent, example embodiments according to the present disclosure will be described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a subset of the embodiments of the present disclosure and not all embodiments of the present disclosure, with the understanding that the present disclosure is not limited to the example embodiments described herein.

Further, in the present specification and the drawings, steps and elements having substantially the same or similar characteristics are denoted by the same or similar reference numerals, and repeated description of the steps and elements will be omitted.

Furthermore, in the specification and drawings, elements are described in the singular or plural according to the embodiments. However, the singular and plural forms are appropriately selected for the proposed situation only for convenience of explanation and are not intended to limit the present disclosure thereto. Thus, the singular may include the plural and the plural may also include the singular, unless the context clearly dictates otherwise.

Moreover, the terms "first," "second," and the like in the description and in the drawings are used for distinguishing similar objects from each other and not necessarily for describing a particular sequential or chronological order, it being understood that "first," "second," and the like may be interchanged under certain circumstances or sequences of events to enable embodiments of the invention described herein to be practiced in other than those illustrated or described herein.

Furthermore, in the present specification and the drawings, terms relating to orientation or positional relationship, such as "upper", "lower", "vertical", "horizontal", and the like, are used only for convenience in describing the embodiments according to the present disclosure, and are not intended to limit the present disclosure thereto. And therefore should not be construed as limiting the present disclosure.

In addition, in the present specification and the drawings, unless otherwise specifically stated, "connected" does not mean that "directly connected" or "directly contacting", and herein, "connected" means both fixation and electrical communication.

In the present specification and drawings, unless otherwise specified, "motion trajectory" does not mean not only a displacement or a trajectory of an object, and here, as is customary in robot dynamics, "motion trajectory" means not only a displacement or an angle made in space of an object but also a velocity, an acceleration, an angular velocity, and an angular acceleration of the object.

In addition, in the present specification and the drawings, unless otherwise explicitly stated, "driving force" is to be understood in a broad sense, that is, "driving force" does not mean "force" and "driving force" herein may mean both force in a narrow sense and "driving torque" (for example, for a joint) with respect to a specific driving object of the "driving force".

As one example, the present disclosure may be applied to the field of intelligent sensors combined with Artificial Intelligence (AI). The artificial intelligence is a theory, a method, a technology and an application system which simulate, extend and expand human intelligence by using a digital computer or a machine controlled by the digital computer, sense the environment, acquire knowledge and obtain the best result by using the knowledge. In other words, artificial intelligence is a comprehensive technique of computer science that attempts to understand the essence of intelligence and produce a new intelligent machine that can react in a manner similar to human intelligence. Artificial intelligence is the research of the design principle and the realization method of various intelligent machines, so that the machines have the functions of perception, reasoning and decision making.

The artificial intelligence technology is a comprehensive subject and relates to the field of extensive technology, namely the technology of a hardware level and the technology of a software level. The artificial intelligence infrastructure generally includes technologies such as sensors, dedicated artificial intelligence chips, cloud computing, distributed storage, big data processing technologies, operation/interaction systems, mechatronics, and the like. The artificial intelligence software technology mainly comprises a computer vision technology, a voice processing technology, a natural language processing technology, machine learning/deep learning and the like.

Currently, with the research and progress of artificial intelligence technology, the artificial intelligence technology is developing research and application in a plurality of fields, such as common smart homes, smart wearable devices, virtual assistants, smart speakers, smart marketing, unmanned, autonomous, unmanned aerial vehicles, robots, smart medical, smart customer service, and the like. Currently, artificial intelligence has been combined with various types of robots and applied to various fields such as smart agriculture, smart factories, and smart warehousing, using the sensing, reasoning, and decision functions of artificial intelligence, for the purpose of performing desired operations on various objects in the above fields (e.g., causing objects to be carried to target sites) instead of human labor, significantly improving the degree of automation of the above fields, and reducing the cost of human resources.

For fixed operation, because relative motion does not exist between the object and the operation part after the fixed connection is established, in the prior art, a dynamic model can be conveniently established for the operation part and the object, and the dynamic model is analyzed by using a Lagrange function balance method and the like, so that accurate control on the motion trail of the operation part and the object is conveniently realized in the subsequent process. For the non-fixed operation, because the fixed connection is not established between the operation part and the object, relative motion may occur between the operation part and the object, and even the object may fall off from the operation part, and it is difficult to control the motion track of the operation part and the object which are not fixedly connected. For example, when the operation unit conveys a plurality of stacked goblets at a high speed, the stacked goblets are likely to fall off the operation unit when the conveying speed is too high. Therefore, it is necessary to further control the non-fixed type operation so as to quickly convey the object without dropping the object.

The present disclosure provides a method of determining a movement trajectory of a robot transfer object when an operating part is in non-fixed contact with an object and a method of determining a movement trajectory of a robot transfer object, which enable the operating part to transfer the object quickly and ensure that the object keeps no relative movement with the operating part all the time by changing the pose of the operating part during transfer.

Thus, according to a first aspect of the present disclosure, a method 100 of robotic handling of objects is provided. Fig. 1 shows a schematic flow diagram of a method 100 of robotic handling of objects according to the present disclosure. Fig. 2 shows a schematic view of the non-stationary contact of the operating part of the robot with the object. For the sake of clarity, only the operating part 210 of the robot and the object 220 to be operated are shown here. For convenience, fig. 1 and 2 will be discussed together.

According to an embodiment of the present disclosure, in a method of a robot carrying an object, the robot having an operating part 210, the operating part 210 being in non-fixed contact with the object 220, the method includes steps S101 to S103. In step S101, the robot receives a transport instruction. In step S102, the driving force of the operation unit is determined based on the conveyance command. And in step S103, driving the operation section with the determined driving force adjusts the posture in conveying the object such that the operation section conveys the object from the start position to the target position with the shift movement and there is no relative movement between the object and the operation section.

See, for example, fig. 2, which illustrates an instant in the handling process. The operating part is shown in white rectangles, and the object is shown in gray rectangles. And assume that the mass of the object is m.

As shown in fig. 2, the operation section has its posture adjusted so that the positive pressure between the operation section and the object makes an angle θ with the direction of gravity to provide a linear acceleration to the object horizontally rightward. Therefore, in the conveying process, the posture of the operation part is adjusted to enable the object to perform variable-speed movement, so that the operation part can finish the conveying process at a higher speed. The positive pressure applied to the subject by the operation unit is mgcos θ, which is smaller than the actual weight G of the subject by mg. That is, in the actual carrying process, there may be a period of time due to the adjustment of the posture of the operation portion, and the positive pressure provided by the operation portion to the object may be smaller than the actual gravity of the object, so that the operation portion can carry a heavier object.

For example, there are a plurality of grasping positions between the object and the operation section, two of which, grasping position a and grasping position B, are schematically shown in fig. 2. The friction force of the object at the grabbing position A is in the friction cone F because the object and the operation part do not move relatively _N1 Within the range, the friction force of the object at the grabbing position B is in the friction cone F _N2 Within the range. That is, the object does not fall off the operation unit during the conveyance. There are also a plurality of different gripping positions between the object and the operating part, depending on the shape and the gravity distribution of the object, and the friction force experienced by the object at each gripping position should be within the corresponding friction cone. The grasp positions a and the grasp positions B are shown only as equivalent grasp positions, and it should be understood by those skilled in the art that the present disclosure is not limited thereto.

Here, compared to a conventional robot that conveys an object by using a fixed contact, for example, a fixed contact established with the object by having a mechanical gripper, a controllable suction member, or the like, the method of conveying an object by a robot according to the present disclosure causes an object that is not in fixed contact with the operation portion to perform a variable speed motion by adjusting the posture of the operation portion itself during conveyance, so as to convey the object at a faster speed without a relative motion between the operation portion and the object. Compared with the displacement of the object by using non-fixed contact, such as driving by a conveyor belt, the pose of the operating part of the robot according to the disclosure can be automatically adjusted according to different objects and/or different motion tracks, so that the flexibility of transportation is improved.

Therefore, when the operation part is not fixedly contacted with the object, the robot can adjust the pose of the robot according to the conveying instruction, so that the robot can convey heavier objects at a higher speed.

Fig. 3A illustrates a pose that can exist in a method of a robot handling an object according to the present disclosure, in which case a centrifugal force that the object has during movement is opposite to a direction of gravity. Fig. 3B shows a schematic diagram of a movement locus of an operation part and an object relating to the posture of fig. 3A. In fig. 3B, the respective states before and after reaching the attitude of fig. 3A are shown from left to right, respectively. For the sake of clarity, corresponding reference numerals are only marked in the partial states.

Here, as shown in fig. 3B, in the process of transporting the object 220 from point a to point B on the trajectory schematically shown in block c, both the operation unit 210 and the object 220 rotate clockwise by the posture adjustment of the operation unit 210. During the conveyance, the determined driving force drives the operating section to adjust the attitude such that the center of mass of the operating section is not lower than the center of mass of the object and the object has a centrifugal force having a component opposite to the direction of gravity. For example, the centrifugal force f that the object has during the process of transporting the object _centrifugal Can be calculated as follows using equation (1).

f _centrifugal ＝w ^b ×mv ^b (1)

Wherein, w ^b Is the angular velocity, v, of the object 220 ^b Is the linear velocity of the object 220 and m is the mass of the object 220. In the attitude shown in FIG. 3A, to make the force analysis clearer, the separation and contact are shown in dotted linesHeart force f _centrifugal The opposite force. Since the center of the circular motion of the object is below the object, the centrifugal force f _centrifugal A gravity mg larger than the object is required to enable the positive pressure f between the operation part 210 and the object 220 _N Thereby generating frictional force. For example, referring to fig. 3A, in a special case where the operating section 210 is in a horizontal attitude with an object just under the operating section, in this case in order to make a positive pressure f _N If present, then have | f _centrifugal |＝|f _N |+|mg|。

At this time, although a centrifugal force is utilized so that a positive pressure between the manipulation part 210 and the object 220 is small, the manipulation part can carry a heavier object. However, since the positive pressure is small, the frictional force that the operation unit 210 can provide to the object 220 is also small, and therefore the acceleration that the object 220 can have is also small, and therefore the moving speed of the object 220 during conveyance is also small. Thus, the movement trajectory and the posture adjustment method of the operation unit in fig. 3A and 3B are more suitable for conveying a heavy object with variable speed movement.

Fig. 4A shows a pose that can exist in the method of the robot handling the object according to the present disclosure, in which case the centrifugal force that the object has during the movement is in the same direction as the direction of gravity. Fig. 4B shows a schematic diagram of a movement locus of an operation part and an object relating to the posture of fig. 4A. In fig. 4B, the respective states before and after reaching the attitude of fig. 4A are shown from left to right, respectively. For the sake of clarity, corresponding reference numerals are only marked in the partial states.

Here, as shown in fig. 4B, in the process of carrying the trajectory schematically shown in the block d of the object 220 from the point a to the point B, both the operation unit 210 and the object 220 rotate counterclockwise by the posture adjustment of the operation unit 210. During the transportation, the determined driving force drives the operation section to adjust the attitude such that the center of mass of the operation section is not higher than the center of mass of the object and the object has a centrifugal force having a component in the same direction as the direction of gravity. For example, the centrifugal force f that the object has during the process of transporting the object _centrifugal Can continue to use the formula (1)And (5) line calculation.

In the movement locus shown in fig. 4B, since the center of the circular motion of the object is above the object, the centrifugal force f _centrifugal The sum of the gravity Mg with the object is equal to the positive pressure f between the operation part 210 and the object 220 _N Thereby generating frictional force. For example, referring to FIG. 4A, in a special case where the operating section 210 is in a horizontal attitude with the object directly above the operating section, there is | f _N |＝|f _centrifugal |+|mg|。

At this time, although the centrifugal force is utilized so that the positive pressure between the operation part 210 and the object 220 is large, and further the frictional force is large, the object can have a larger acceleration, and the operation part can convey the object more quickly. However, the carrying process requires a higher load-bearing capacity of the operation part. Thus, the movement locus and the posture adjustment manner of the operation portion of fig. 4A and 4B are more suitable for faster conveyance of a light object with variable speed movement.

Fig. 5 shows schematic diagrams in a first phase (i.e., an acceleration phase) and a second phase (i.e., a deceleration phase) of a variable speed motion in a method of a robot handling an object according to the present disclosure. In fig. 5, the positive pressure at which the object 220 is in contact with the operating part 210 is shown as f _N The frictional force between the object 220 and the operation part 210 is shown as f _f The gravity of the object 220 is shown as G, the inclination angle of the operation portion 210 with respect to the horizontal plane is shown as θ, and the resultant force of the respective forces received by the object 220 is shown as F _a 。

According to a more detailed embodiment of the method of robot handling objects of the present disclosure, the driving force may be further determined using different strategies to make more accurate adjustments to the pose of the operating part to further shorten the handling time. For example, the acceleration stage and the deceleration stage may be designed separately during the process of the robot carrying the object to more quickly carry the object from the start position to the target position while satisfying no relative movement and no fixed contact between the object and the operation part.

For example, in a first period, the operating part applies a first frictional force to the object so that the object moves in an accelerated state, the first frictional force having a component opposite to a linear acceleration direction of the object. The operating part applies a second frictional force to the object to move the object in a decelerated state, the second frictional force having a component in the same direction as a linear acceleration direction of the object, for a second period.

As shown in fig. 5, when the object velocity v and the friction force f _f When the direction is the same, the acceleration a of the object is the same as the speed direction, and the object is in an acceleration state. On the contrary, when the object velocity v and the friction force f _f When the direction is opposite, the acceleration a of the object is opposite to the speed direction, and the object is in a deceleration state.

Thus, when the object is in an acceleration state or a deceleration state, the force-bearing relationship of the object 220 can be expressed by formula (2), where a is the acceleration of the object.

Further derivation is performed based on the formula (2), and the following inequality (3) can be obtained.

‖mgsinθ-macosθ‖≤μ(mgcosθ+mgsinθ) (3)

Thus, by further solving, the boundary condition of the acceleration a of the object 220 can be determined, which can be shown as inequality (4) below.

gtan(θ-θ ₀ )≤a≤gtan(θ+θ ₀ ) (4)

Wherein, theta ₀ = atan μ, friction cone angle. That is, when the acceleration a of the object 220 satisfies the above condition, the object 220 may be kept in balance. From the above derivation, the acceleration a of the visible object 220 is directly related to the inclination angle of the operating section 210, that is, the acceleration of the object is larger as the operating section 210 adjusts its posture to form a larger inclination angle with respect to the horizontal plane. In such a case, the object 220 can perform a variable speed movement at a faster speed, and stable grasping is ensured (i.e., no relative movement with the operation portion 210).

It will be appreciated by those skilled in the art that the derivation process described above is merely an example of a rubbing condition of the object 220 in a certain direction. In an actual conveying process, the motion trail of the object is often in a more complicated state, and friction conditions in different directions in a three-dimensional space need to be considered. A more detailed implementation of the method 100 corresponding to the complex trajectory will be described further below with reference to fig. 6-7. Those skilled in the art will appreciate that the present disclosure is not so limited.

A more detailed embodiment of a method of robot handling objects according to the present disclosure is described below with reference to fig. 6 to 7. Fig. 6 shows a schematic diagram of a friction cone of an object in a method for handling the object by a robot according to the present disclosure. Fig. 7 illustrates an example of movement trajectories of an object and an operation part in the method for the robot to convey the object according to the present disclosure.

In this more detailed embodiment, the conveyance command includes motion trajectory information indicating a motion trajectory of the operation unit and the object desired during conveyance of the object by the operation unit, spatial dimension information indicating spatial dimensions of the operation unit and the object, and mass information indicating a mass or moment of inertia of the operation unit and the object, or an operation unit driving force parameter corresponding to different times while the operation unit is conveying the object.

Thus, the robot can determine the driving force for realizing the operation unit specified in the transport command by using a plurality of methods such as a kinetic analysis, for example, a basic kinetic theory, lagrangian mechanics, a rotation-even method, and a kanne method, based on the motion trajectory information, the spatial dimension information, and the quality information.

According to a further alternative design of the method for transporting an object by a robot of the present disclosure, in consideration of the computational power of the robot itself or the limitation thereof, instead of performing the kinetic analysis by the robot itself by means of the motion trajectory information, the spatial dimension information, and the mass information, the kinetic analysis may be performed by another computing device disposed outside the robot, and the results of the kinetic analysis, that is, the operating section driving force parameters corresponding to different times in motion, may be transmitted to the robot as the transport instruction. Therefore, the transport command referred to here does not indicate a desired movement trajectory of the operation unit and the object during the transport of the object, but directly includes operation unit driving force parameters corresponding to different timings during the transport of the object by the operation unit, which are determined by another calculation device based on the desired movement trajectory of the operation unit and the object. Thus, the method for conveying an object by a robot according to the present disclosure can be performed in the same manner even for a robot with limited computing power.

To determine the driving force of the operating portion, it is necessary to determine the relationship between the driving force of the operating portion and the motion trajectory of the object, and then further determine the driving force to optimize a certain target. A model that determines a driving force capable of optimizing a certain target based on the driving force and the motion trajectory of the object is hereinafter referred to as a control model. The specific goal may be, for example, to minimize the movement time of the object from a starting position to a target position. The specific goal may also be, for example, maximizing the weight of the object that can be handled during a specific movement time. Those skilled in the art will appreciate that the present disclosure is not limited to optimization goals.

For example, the control model may be associated with: the dynamic model corresponding to the operation part, the dynamic model corresponding to the object, the stable grabbing constraint equation set, the motion trail of the operation part and the motion trail of the object. Wherein the stable grasping constraint equation set is associated with a contact force provided to the object by the operating portion and a gravity and/or a centrifugal force that the object has. Wherein the stable grasping constraint equation set further includes stable constraint equations regarding a plurality of equivalent contact points between the operating part and the object, the stable constraint equations being configured to constrain a contact force of each of the plurality of equivalent contact points within a friction cone range corresponding to the contact point.

Referring to fig. 6, for example, the dynamic model corresponding to the object may be used to characterize the relationship between the motion trajectory of the object and the stress condition of the object. That is, in some examples, the dynamic model of the object indicates a relationship between a contact force provided to the object by the operating part, a gravity of the object, an inertial force of the object, and a centrifugal force of the object, and a linear acceleration and an angular acceleration of the object.

Assume that the world coordinate system is { W }, the connected coordinate system is { b }, and the center of the connected coordinate system is the centroid of the object. Thus, the corresponding dynamic model of the object can be expressed as follows in equation (5):

in formula (5), M = mE ∈ R ^3×3 M is the quality of the object 220, E ∈ R ^3×3 Is an identity matrix, I is an inertia matrix of the object, F ^b And τ ^b Are respectively 6-dimensional vectors W ^b ＝R ^6×1 Force and moment components of v ^b And w ^b Respectively the linear and angular velocity of the object,

and

respectively linear and angular acceleration of the object.

The dynamic model of the object can be further characterized by the contact force and the gravity to which the object is subjected, i.e. the dynamic model of the object can be further characterized by the contact force term and the gravity term in equation (6).

W ^b ＝w _g +w _c (6)

In the above formula, w _g ∈R ^6×1 And w _c ∈R ^6×1 Force and moment space vectors due to the gravity and contact force terms, respectively.

In the world coordinate system { w }, the gravity term can be expressed in equation (7).

Assume that the rotation matrix between w and b is R _wb Is epsilon of SO (3), and the relative position of the two is p _wb ，

Is a transformation matrix between the world coordinate system and the connected coordinate system, then w _g And

the relationship therebetween can be expressed as follows in equation (8).

The contact force term can be expressed as in equation (9) below.

w _c ＝G _r (r)f (9)

In the above formula, f is the contact force, G _r And (r) is a grabbing matrix taking the equivalent contact position as an independent variable. As shown in FIG. 6, at the equivalent contact point position i, the components of the contact force f in the x, y and z directions are f _xi ，f _yi And f _zi . Based on the above-described dynamic model corresponding to the object and the mechanical analysis relationship shown in fig. 6, it can be derived that if no relative motion between the object and the operation portion is to be achieved, a stable constraint equation shown in the following equation (10) needs to be satisfied at the equivalent contact point position i. The stability constraint equation is configured to constrain the contact force of each of a plurality of equivalent contact points to be within a corresponding friction cone of the contact point.

In the formula (10), μ isCoefficient of friction. FC _i The friction cone of the ith contact point. By combining the above-mentioned kinetic equation of the object with the grasping stabilization condition, the formula (11) can be further derived.

Wherein G is _r (r) ⁺ Is G _r The inverse of (r). Thus, the above-mentioned stable grab constraint equation system can be further formulated into the form of equation (12).

min‖w _c -Gf‖ ²

subject to:f _zi >0

f _i ∈FC _i (12)

That is, the stable grab constraint equation set is indicated to minimize | w _c -Gf‖ ² Is targeted and ensures that the object does not fall off.

For example, the dynamic model corresponding to the operation portion may be used to represent a relationship between a motion trajectory of the operation portion (e.g., a pose of the operation portion) and a force condition of the operation portion. At the same time as the operating section applies a force to the object, the object also applies a reaction force to the operating section. The operation unit is also subjected to a force such as gravity and centrifugal force. For the sake of simplicity, the force analysis of the operation portion is omitted in fig. 6.

In some examples, the dynamic model of the operating portion indicates a relationship between inertia, centrifugal force, gravity, coulomb friction, driving force of the operating portion, and a motion trajectory of the operating portion. For example, the dynamic equation of the operating portion may be as shown in the following equation (13).

In the formula (11), M (q), C (q), and G (q) are an inertia matrix, a centrifugal force term matrix, and a gravity term matrix of the operation portion, respectively. F _s (q) isA matrix of the coulomb friction torques is generated,

the joint angle, the joint angular velocity, and the joint angular acceleration of the operation portion, respectively. τ is a driving force matrix of the operation section.

Considering the normalized path coordinates s (T) of the operation section, the start time is T =0, the end time is T = T, and there is s (0) =0 ≦ s (T) ≦ 1=s (T). The first order and second order differential terms of s (t) are respectively

And

considering the need to minimize the movement time of the object from the starting position to the target position, it can be designed

Thus, the trajectory of the joint space of the operation portion in relation to the path coordinates can be expressed by equation (14):

in the formula (12), the reaction mixture is,

this generates a dynamic model corresponding to the operation portion shown in the following equation (15).

Specifically, in formula (15), M(s) = M (q (s)) q '(s), C(s) = M (q (s)) q ″(s) + C (q (s)), q ' (s)) q '(s), g(s) = F _s (q(s))sgn(q′(s))+G(q(s))。

Therefore, the following control model can be obtained based on the dynamic model corresponding to the operation part, the dynamic model corresponding to the object, the stable grabbing constraint equation set, the motion trail of the operation part or the motion trail of the object. Since the operation part and the object do not move relatively in the whole moving process and the motion tracks of the operation part and the object have similar limits on the driving force, only the motion track of the operation part is selected to construct the control model.

For example, the control model may be designed with the goal of minimizing the movement time of the object from a start position to a target position. That is, the control model indicates: and determining the driving force of the operation part based on a dynamic model corresponding to the operation part, a dynamic model corresponding to the object and a stable grabbing constraint equation system by taking the minimization of the movement time of the object from a starting position to a target position as a target.

Based on at least the above formulas, a control model composed of a set of formulas (16) to (23) can be designed.

The objective is to minimize T, and the following equations are satisfied for T ∈ [0,T ]

s(0)＝0 (17)

s(1)＝1 (18)

τ(s(t)) ^down ≤τ(t)≤τ(s(t)) ^up (21)

f _zi >0 (22)

f _i ∈FC _i (23)

In the formulae (16) to (23),

and

the coordinate conversion rates of the operation unit trajectory at the start time and the end time are respectively. τ (s (t)) ^up And τ (s (t)) ^down Respectively the upper and lower limits of the moment of the driving force.

It will be understood by those skilled in the art that the motion trajectory referred to above may further include the motion states of the operating part of the robot and the object at various times in joint space and cartesian space during the transportation, which are referred to as cartesian space trajectory and joint space trajectory, respectively. The control model described above may further combine the cartesian space trajectory and the joint space trajectory to further determine the driving force of the operation portion. For example, in some examples, it may also involve using pose adjustments in cartesian space to avoid potential obstacles during the actual completion of object handling by the operating portion of the robot. That is, during the process of carrying the object, it may further involve switching between cartesian space trajectory and joint space trajectory of the robot, and also involve rapid transfer of cartesian space complex trajectory of the robot.

In the process of switching the track of the robot in the joint space and the Cartesian space, if the operation is not stopped, the speed and the acceleration of the joint space and the Cartesian space at the switching position are required to be continuous. Under a time-optimal control framework (that is, the robot is controlled by taking the motion time of the object from the initial position to the target position as the target), the tracks of the joint space and the cartesian space of the robot are realized by the tracks of the joint space of the robot, so that the smooth switching can be realized only by ensuring that the positions of switching points in the cartesian space are consistent and the speed and the acceleration are continuous. And the tracks of the joint space and the Cartesian space are continuous, so that the robot can move rapidly under the condition of large-range movement, namely the track of the joint space of the robot ensures that the time of the robot in a large range is shortest, and the track of the Cartesian space of the robot ensures that the time of the robot in a small range is shortest.

For example, referring to fig. 7, three different motion profiles are shown in fig. 7. Wherein, the track A is the inner circumference motion, the track B is the outer circumference motion, and the track C is the schematic complex track motion. Although both the trajectory a and the trajectory B perform circular motion, they present different poses within the range of the dotted circle, so that there is no collision between the object and a possible external obstacle. Because the control model is designed in a dynamic graspi ng mode, the related Cartesian track of the object can be expressed as 6 pose quantities of position and pose. That is, the end pose amount of the robot can be expressed by equation (24).

X＝[x,y,z,α,β,γ] ^T (24)

In the formula (24), X is the pose of the end of the robot, X, y, and z are three position quantities of the robot, and α, β, and γ are three pose quantities of the robot. The end pose amount X of the robot can be associated with the above formula (14) through the conversion of cartesian space and joint space to advantageously realize the process control of the carried object.

In addition, it is also possible to solve a so-called dynamic positive problem that the movement locus of the operation portion and the object is determined by the driving force of the operation portion in the case where the operation portion is in non-fixed contact with the object based on the control model.

Thus, according to a second aspect of the present disclosure, a method 800 of determining a motion trajectory of a robotic handling object is provided. Fig. 8 shows a schematic flow chart of a method of determining a motion trajectory of an operating part of a robot according to the present disclosure. Wherein the operating portion is also in non-stationary contact with an object and carries the object from a starting position to a target position in a variable speed movement, the method comprising: and step S810, determining the motion trail of the operation part based on a control model. Wherein the control model indicates: aiming at minimizing the movement time of the object from a starting position to a target position, determining the movement track of the operation part based on a dynamic model corresponding to the operation part, a dynamic model corresponding to the object and a stable grabbing constraint equation set, wherein the stable grabbing constraint equation set is related to the contact force provided by the operation part to the object and the gravity and the centrifugal force of the object.

Here, the stable grasping constraint equation set further includes stable constraint equations regarding a plurality of equivalent contact points between the operation part and the object, the stable constraint equations being configured to constrain the contact force of each of the plurality of equivalent contact points within a range of the friction cone corresponding to the contact point.

For example, in a process in which the operation section carries the object from a start position to a target position in a variable speed motion, the operation section adjusts the attitude so that the center of mass of the operation section is not lower than the center of mass of the object and the object has a centrifugal force having a component in the direction of gravity. Alternatively, the operating section adjusts the posture so that the center of mass of the operating section is not higher than the center of mass of the object and the object has a centrifugal force having a component in the opposite direction to the direction of gravity.

For example, the carrying of the object from the start position to the target position in a variable speed motion comprises: the operating part applies a first frictional force to the object for a first period of time so that the object moves in an accelerated state, the first frictional force having a component opposite to a linear acceleration direction of the object; the operating part applies a second frictional force to the object to move the object in a decelerated state, the second frictional force having a component in the same direction as a linear acceleration direction of the object, for a second period.

According to a more detailed embodiment of the present disclosure, the specific process of further setting the control model in the method 800 for determining the motion trajectory of the operation portion of the robot is described above, and is not described herein again for brevity.

Further, according to a third aspect of the present disclosure, there is also provided a robot. Fig. 9 shows a schematic block diagram of a robot according to the present disclosure. As shown in fig. 9, the robot includes: an operation unit 210 that applies a supporting force and a frictional force to an object to cause the object to be carried from a start position to a target position in a variable-speed motion; and a controller 920, the controller 920 being configured to control the operation portion to adjust the pose, the controller being provided on the robot and being configured to perform the method of robot handling the object according to the first aspect of the present disclosure and the method of determining the motion trajectory of the robot handling object according to the second aspect of the present disclosure.

According to a more detailed embodiment of the robot of the present disclosure, the operating part 210 may be implemented as any operating part commonly found in the field of robots, such as a mechanical gripper or a pallet, etc. As mentioned above, the handling part in the sense of the present disclosure does not require a fixed handling of the object, i.e. in case the handling part is a mechanical gripper, the fingers of the mechanical gripper do not need to be bent to establish a fixed connection with the object (i.e. e. to e.g. grab the object), i.e. to transport the object.

According to a more detailed embodiment of the robot of the present disclosure, the controller 920 may be implemented, for example, as any device that can perform the methods according to the first aspect of the present disclosure and the second aspect of the present disclosure, including but not limited to, an FPGA, a DSP, an ARM single chip, a CPU, and the like. For more details of the functions of the controller 920, reference may be made to the description of the method described above for the first aspect of the present disclosure and the second aspect of the present disclosure, and details are not repeated here.

In summary, the present disclosure provides a method for a robot to transport an object. Wherein by constraining and adjusting the pose of the operating part of the robot such that the contact force between the operating part and the object can be changed in the case where the operating part is in non-fixed contact with the object, the object can be carried from a start position to a target position in variable speed motion in the case where the operating part is in non-fixed contact with the object, thereby enabling the robot to carry heavier objects at a faster speed.

Further, the present disclosure provides a method of determining a motion trajectory of a robot handling object. Wherein, as described above, the movement locus of the operation part is determined based on the control model so that, in the case where the operation part is in non-fixed contact with the object, the contact force provided to the object by the operation part and the centrifugal force of the object are changed by adjusting the position of the operation part, thereby enabling the robot to carry a heavier object at a faster speed.

Further, the present disclosure provides a robot, and a robot according to the present disclosure enables the robot to carry a heavier object at a faster speed by adjusting the posture of the operation portion of the robot, as described above.

The exemplary embodiments of the present disclosure described in detail above are merely illustrative, and not restrictive. It will be appreciated by those skilled in the art that various modifications and combinations of these embodiments or features thereof may be made without departing from the principles and spirit of the disclosure, and that such modifications are intended to be within the scope of the disclosure.

Claims

1. A method of a robot handling an object, the robot having an operating portion in non-stationary contact with the object, the method comprising:

receiving a carrying instruction;

determining a driving force of an operation unit based on the transport instruction; and

the operation section is driven with the determined driving force to adjust the posture in the process of conveying the object so that the operation section conveys the object from the home position to the target position in the variable speed movement without the relative movement of the object and the operation section.

2. The method of claim 1, wherein,

the conveyance instruction includes motion trajectory information indicating a desired motion trajectory of the operation portion and the object during conveyance of the object by the operation portion, spatial size information indicating spatial sizes of the operation portion and the object, and quality information indicating a mass or a moment of inertia of the operation portion and the object, or

The transport command includes an operation unit driving force parameter corresponding to a different timing when the operation unit transports the object.

3. The method of claim 1, wherein,

the determination of the driving force of the operating portion is based at least in part on a control model associated with: a dynamic model corresponding to the operation part, a dynamic model corresponding to the object, a stable grabbing constraint equation set, a motion trail of the operation part and a motion trail of the object,

wherein the stable grasping constraint equation set is associated with a contact force provided to the object by the operating portion and a gravitational force and a centrifugal force that the object has.

4. The method of claim 3, wherein the set of stable grasp constraint equations further includes stable constraint equations for a plurality of equivalent contact points between the operating portion and the object, the stable constraint equations configured to constrain the contact force of each of the plurality of equivalent contact points within a corresponding friction cone of the contact point.

5. The method according to claim 3, wherein the dynamic model of the object indicates a relationship between a contact force provided by the operating part to the object, a gravity of the object, an inertial force of the object, and/or a centrifugal force of the object, and a linear acceleration and an angular acceleration of the object.

6. The method according to claim 3, wherein the dynamic model of the operating portion indicates a relationship between inertia, centrifugal force, gravity, coulomb friction force, driving force of the operating portion, and a motion trajectory of the operating portion.

7. The method of claim 3, wherein the control model indicates: and determining the motion trail of the operation part based on the dynamic model corresponding to the operation part, the dynamic model corresponding to the object and the stable grabbing constraint equation system by taking the minimized motion time of the object from the starting position to the target position as an objective.

8. The method according to claim 1, wherein the determined driving force drives the operating part to adjust the attitude such that the center of mass of the operating part is not lower than the center of mass of the object and the object has a centrifugal force having a component opposite to the direction of gravity, during the operation of the operating part in carrying the object.

9. The method according to claim 1, wherein the determined driving force drives the operating part to adjust the attitude such that a center of mass of the operating part is not higher than a center of mass of the object and the object has a centrifugal force having a component in the same direction as a direction of gravity, during the operation of the operating part in carrying the object.

10. The method of claim 1, the object being transported from a starting position to a target position in a variable motion comprising:

the operating part applies a first frictional force to the object for a first period of time so that the object moves in an accelerated state, the first frictional force having a component opposite to a linear acceleration direction of the object;

the operating part applies a second frictional force to the object to move the object in a decelerated state, the second frictional force having a component in the same direction as a linear acceleration direction of the object, for a second period.

11. A method of determining a motion trajectory of a robot carrying an object, an operating part of the robot being in non-stationary contact with the object and the operating part carrying the object from a start position to a target position in a variable speed motion, the method comprising:

determining a movement locus of the operation part based on a control model,

wherein the control model indicates: determining a motion track of the operation part based on a dynamic model corresponding to the operation part, a dynamic model corresponding to the object and a stable grabbing constraint equation system by taking the minimized motion time of the object from a starting position to a target position as a target,

wherein the stable grasping constraint equation system is associated with a contact force provided to the object by the operating part and a gravitational force and a centrifugal force that the object has.

12. The method of claim 11, wherein the set of stable grasp constraint equations further includes stable constraint equations for a plurality of equivalent contact points between the operating portion and the object, the stable constraint equations configured to constrain the contact force of each of the plurality of equivalent contact points within a corresponding friction cone of the contact point.

13. The method according to claim 11, wherein in the process in which the operating portion carries the object from a start position to a target position in a variable-speed motion,

the operating section adjusts the posture so that the center of mass of the operating section is not lower than the center of mass of the object and the object has a centrifugal force having a component opposite to the direction of gravity; or alternatively

The operating section adjusts the posture so that the center of mass of the operating section is not higher than the center of mass of the object and the object has a centrifugal force having a component in the same direction as the direction of gravity.

14. The method of claim 11, wherein the object being transported from a starting position to a target position in a variable motion comprises:

15. A robot, the robot having:

an operation portion that applies a supporting force and a frictional force to an object so that the object is carried from a start position to a target position in a shifting motion;

a controller for controlling the operation section to adjust the pose, the controller being provided on the robot and configured to perform the method according to any one of claims 1 to 14.