CN111695213B

CN111695213B - Continuous robot kinematics equivalent method and application

Info

Publication number: CN111695213B
Application number: CN202010450642.7A
Authority: CN
Inventors: 刘厚德; 程淏; 王学谦; 兰斌; 梁斌
Original assignee: Shenzhen International Graduate School of Tsinghua University
Current assignee: Shenzhen International Graduate School of Tsinghua University
Priority date: 2020-05-25
Filing date: 2020-05-25
Publication date: 2023-04-07
Anticipated expiration: 2040-05-25
Also published as: CN111695213A

Abstract

The invention provides a kinematic equivalent method of a continuous robot and application thereof, wherein the method comprises the following steps: a kinematic equivalence method adopting a two-connecting-rod-four-joint equivalent model uses a rigid arm to conduct equivalence on the kinematics of a continuous robot based on a segmentation constant curvature assumption. By using the two-connecting-rod-four-joint equivalent model to be equivalent to the motion of the continuous robot, the equivalent model can effectively simplify the existing model and reduce the environmental perception, planning and control difficulty of the continuous robot.

Description

Continuous robot kinematics equivalent method and application

Technical Field

The invention relates to the technical field of continuous robots, in particular to a kinematic equivalence method of a continuous robot and application thereof.

Background

In the aspects of disaster rescue, nuclear and radiation equipment overhaul, toxic waste sampling, pipeline monitoring and the like, the space is narrow and large-scale equipment is not suitable for people or large-scale equipment to enter for carrying out work, so that the continuous Robots (continuous Robots) with fine body shapes and flexible movement become an important choice. The continuous robot has good bending characteristic and obstacle avoidance capability, can change self shape and posture and other adaptive environments, overcomes the limitation of various obstacles, and is widely applied to special occasions of autonomous operation in unstructured environments, such as the fields of medical treatment, military, disaster rescue, ocean exploration and the like. However, the current research on the continuous robot mainly focuses on the innovative design of the robot structure, and the perception planning control technology for such a robot is far less mature than the traditional mechanical arm, which severely limits its ability to flexibly work in an unstructured environment such as a narrow space.

Continuous robot environment perception (arm type pose estimation and environment map construction) is the basis for realizing effective planning control under a complex unknown environment so as to avoid obstacles and complete tasks; and firstly, modeling and describing the kinematic relationship of the continuum robot is required to realize the environment perception of the continuum robot.

In the common continuous robot perception planning control technology, the method is often based on a Piecewise Constant Curvature hypothesis (PCC); the segmental constant curvature assumed continuous robot is formed by splicing a plurality of sections of arcs of which the curvatures are respectively a certain value which can change along with time, so that the application difficulty of the continuous robot can be effectively reduced.

In the prior art, the kinematic shape coding description method of the continuum robot can describe the arm shape (mechanical arm configuration, namely space shape) of the continuum robot without any assumption. The biggest disadvantage of the description method is that the model is complex and is not beneficial to engineering realization; and the prior knowledge in the design of the existing continuum robot is ignored, and the continuum robot is only regarded as an arbitrary space curve.

The existing continuum robot kinematics model based on the constant curvature hypothesis is formed by splicing a plurality of sections of arcs of which the curvatures are respectively a certain value which can change along with time by assuming the continuum robot; the method considers prior information in the design and engineering realization of the continuum robot, and effectively simplifies the kinematics model of the continuum robot. The existing continuum robot kinematics model based on the assumption of piecewise constant curvature has the condition that singular points are easy to generate numerical instability, has strong nonlinearity, and is not beneficial to applications such as environmental perception, planning, control and the like of the continuum robot.

Therefore, an improved scheme for the kinematic model is needed, so that the kinematic model is more beneficial to environment perception, planning and control of the continuum robot, and limitation of numerical instability and nonlinearity on environment perception, planning and control of the continuum robot is effectively avoided.

The above background disclosure is only for the purpose of assisting understanding of the concept and technical solution of the present invention and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.

Disclosure of Invention

The invention provides a kinematic equivalent method of a continuous robot and application thereof in order to solve the existing problems.

In order to solve the above problems, the technical solution adopted by the present invention is as follows:

a continuous robot kinematics equivalent method is characterized in that a kinematics equivalent method adopting a two-connecting-rod-four-joint equivalent model is used for carrying out equivalence on the continuous robot kinematics based on a segmental constant curvature assumption by using a rigid arm.

Preferably, the kinematic equivalence comprises the following steps: s1: dividing the continuous robot based on the subsection constant curvature hypothesis into a plurality of constant curvature sections, acquiring the length of each constant curvature section and distinguishing each constant curvature section; s2: for each constant-curvature section, performing equivalence by using a rigid arm according to the length of each constant-curvature section; s3: and integrating the equivalent parameters of each constant curvature section, and writing the equivalent D-H parameters of the continuous robot based on the subsection constant curvature hypothesis to obtain the kinematic equivalent method of the equivalent model.

Preferably, the length of each constant curvature segment is constant.

Preferably, each of the constant curvature segments is equivalent to two rigid links connected by four revolute joints, and is equivalent within an error range by parameter constraints.

Preferably, the parameter includes a geometrical relationship between an axial deflection angle and a yaw assist angle of the constant-curvature section.

Preferably, the equivalents comprise: short rod-long rod equivalent, long rod-short rod equivalent; and obtaining the geometric relation between the axial deflection angle and the deflection auxiliary angle of the constant-curvature section according to the short rod-long rod equivalent.

Preferably, the geometric relationship between the axial deflection angle and the deflection auxiliary angle of the constant-curvature section satisfies:

further simplification results in:

wherein theta is the axial deflection angle of the constant curvature segment,

is the yaw assist angle of the constant curvature segment and L is the length of the constant curvature segment.

Preferably, according to a long rod-short rod equivalent method, obtaining equivalent parameters as follows: the configuration parameter state variables of the constant curvature segment comprise an axial deflection angle theta, an axial rotation angle psi and an equivalent long rod length l ₁ =3/4L, equivalent short rod length L ₂ =1/4L, equivalent first deflection angle

Equivalent second deflection angle, i.e. deflection auxiliary angle>

Preferably, kinematic equivalence further comprises: s4: a kinematic equivalence method of evaluating the equivalence model.

The invention also provides application of the continuous robot kinematic equivalence method, and the continuous robot kinematic equivalence method is adopted.

The beneficial effects of the invention are as follows: the equivalent model can effectively simplify the existing model and reduce the environmental perception, planning and control difficulties of the continuous robot.

Furthermore, the invention obtains the configuration direct list writing kinematics equivalent D-H parameter of the continuum robot, thereby rapidly obtaining the kinematics relationship between the configuration space and the Cartesian space, further greatly improving the modeling efficiency of the piecewise constant curvature continuum robot and improving the efficiency of the piecewise constant curvature hypothesis-based kinematics equivalent method of the continuum robot.

Furthermore, the model complexity is reduced and the efficiency is improved in the environment perception, planning and control of the continuous robot.

Drawings

FIG. 1 is a schematic diagram of the geometrical relationship based on the kinematic model of the continuum robot in the prior art.

Fig. 2 is a schematic diagram of a kinematic description method of a continuum robot in an embodiment of the invention.

FIG. 3 is a schematic diagram of a geometric relationship of a constant curvature segment of the continuum robot based on the assumption of the segmented constant curvature in the embodiment of the invention.

4 (a) -4 (b) are schematic diagrams of the kinematic equivalent arm type parameter description model of the constant curvature section of the continuum robot in the embodiment of the invention.

FIG. 5 is a schematic diagram of an equivalent case of the normal curvature segment axial deflection plane in the embodiment of the present invention.

Fig. 6 (a) -6 (b) are schematic diagrams of an overall equivalent example of the segmented constant-curvature continuous robot in the embodiment of the invention.

FIG. 7 is a schematic diagram of a kinematic description method of a continuum robot according to an embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the embodiments of the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for either a fixing or a circuit communication.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

The associated nouns explain:

the continuous robot: the continuous robot is a novel bionic robot which is smooth and high in flexibility. Different from the structure of the traditional discrete robot which consists of discrete joints and rigid rods, the bending performance of the discrete robot is excellent, and the discrete robot can be suitable for the unstructured environment with numerous obstacles and narrow working space.

Piecewise constant curvature assumption: the Piecewise Constant Curvature hypothesis (PCC) assumes that a continuum robot is formed by splicing a plurality of arcs of which the curvatures are respectively a certain value which can change along with time.

Continuous robot arm type: continuum robots are generally similar to robotic arms, and arm type, i.e., robotic arm configuration, refers to the overall shape of a continuum robot robotic arm.

The continuous robot kinematics description technology is a precondition for realizing perception, planning and control of the continuous robot.

The existing continuous robot kinematics description method is mainly based on a Piecewise Constant Curvature hypothesis (PCC); the method for describing the motion of the continuous robot by the segmental constant curvature takes the continuous robot as a spliced arc with a plurality of segments of curvatures which can change along with time, and considers prior information in the design and the engineering realization of the continuous robot, thereby simplifying the description of the kinematics of the continuous robot.

Fig. 1 is a schematic diagram of the geometrical relationship based on the kinematics model of the continuum robot in the prior art. Wherein S represents a coordinate system.

The corresponding kinematic homogeneous transformation relationship is as follows:

wherein L is _i For a constant value, i.e. the length of the constant curvature section,. Phi _i Angle of axial rotation, θ _i Is an axial deflection angle. The pose transformation relation between each section of the continuous robot is psi _i And theta _i And (4) uniquely determining.

However, the existing continuous robot segment constant curvature motion description method has the following technical problems: 1. singular points are artificially introduced in the description process, so that the numerical value is easy to be unstable; 2. the description method involves stronger nonlinear formula calculation, increases the calculation difficulty and is not beneficial to further application.

The invention provides a kinematic equivalence method of a continuum robot and application thereof.

The method is different from the existing segmental constant-curvature continuous robot kinematics description technology, adopts the kinematics equivalent method of the two-connecting-rod-four-joint equivalent model to describe the kinematics of the continuous robot by using the traditional rigid arm, and can effectively reduce the application difficulty of the description technology.

The method of the invention can convert the perception, planning and control of the continuum robot based on the assumption of the piecewise constant curvature into the traditional rigid mechanical arm as an object.

As shown in fig. 2, in one embodiment of the present invention, a method for describing kinematics of a continuum robot is provided, comprising the steps of:

s1: dividing the continuous robot based on the assumption of the segmented constant curvature into a plurality of constant curvature segments, acquiring the length of each constant curvature segment and distinguishing each constant curvature segment;

s2: for each constant-curvature section, performing equivalence by using a rigid arm according to the length of each constant-curvature section;

s3: and integrating the equivalent parameters of each constant curvature section, and writing the equivalent D-H parameters of the continuous robot based on the subsection constant curvature hypothesis to obtain the kinematic equivalent method of the equivalent model.

According to the method, the configuration direct column-writing kinematic equivalent D-H parameter of the continuous robot is obtained, so that the kinematic relationship between the configuration space and the Cartesian space is quickly obtained, and further the modeling efficiency of the segmented constant-curvature continuous robot is greatly improved.

As shown in fig. 3, the continuum robot based on the assumption of the piecewise constant curvature is designed based on the assumption of the piecewise constant curvature. The whole continuous robot can be divided into a plurality of constant-curvature sections, namely, the constant-curvature sections can be similar to a multi-section circular arc, and the length L of each section _i Is a constant value. The length of each constant curvature section can be obtained through measurement, and each constant curvature section is distinguished to carry out the equivalence of each section in the next step.

As shown in fig. 4 (a) and 4 (b), each constant curvature segment of the segmented constant curvature continuous robot can be equivalent to two rigid links connected by four rotational joints on the aspect of kinematics, and is constrained by specific parameters within an acceptable error range, which is equivalent to the theoretical kinematics of the constant curvature segment. In one embodiment of the invention, the parameter comprises a geometrical relationship between an axial deflection angle and a yaw assist angle of said constant curvature segment.

The method is characterized in that a two-connecting-rod-four-joint rigid arm combination mode and a parameter relation thereof are provided, and particularly the geometric relation between the axial deflection angle and the deflection auxiliary angle of the constant-curvature section is provided.

Fig. 5 is a schematic diagram showing an equivalent situation of a constant curvature segment axis deflection plane according to the present invention.

The equivalent method comprises two methods of short rod-long rod equivalent and long rod-short rod equivalent.

The equivalent model of the invention is composed of two linksThe length of the rigid body rod is determined by the length L of the constant curvature section, and the axial deflection angle theta and the auxiliary deflection angle in the constant curvature section

With a constraint relationship. According to symmetry, two equivalent modes exist, a black solid line represents a long rod-short rod equivalent method, a black dotted line represents a short rod-long rod equivalent method, the black solid line equivalent mode is usually used in practical application, and the black dotted line equivalent mode is only used for deducing a geometric constraint relation between equivalent deflection angles; the following constraints are obtained from the geometrical relationship of the short-rod-long-rod equivalent method:

further simplification results in:

the parameters of the specific equivalent method are shown in Table 1.

TABLE 1 detailed parameters of equivalent model

The configuration parameter state variables of the constant curvature segment comprise an axial deflection angle theta, an axial rotation angle psi and an equivalent long rod length l ₁ =3/4L, equivalent short rod length L ₂ =1/4L, equivalent first deflection angle

Equivalent second deflection angle, i.e. deflection auxiliary angle

Axial deflection angle theta and deflection auxiliary angle->

Satisfying formula (3).

After the equivalent rigid models of all the constant curvature sections are obtained through the steps, all the sections of the equivalent rigid models can be connected according to the connection mode of all the constant curvature sections of the segmented constant curvature continuous robot.

Fig. 6 (a) and 6 (b) are schematic diagrams illustrating an overall equivalent example of a piecewise constant curvature continuous robot according to an embodiment of the present invention.

Then, according to a classical robot D-H parameter description model, a continuous robot kinematics equivalent description D-H parameter is listed.

As shown in fig. 7, the inventive continuous robot kinematic equivalent method based on the assumption of piecewise constant curvature further includes:

s4: a kinematic equivalence method of evaluating the equivalence model.

Specifically, the deviation between the kinematic equivalent method and the piecewise constant curvature kinematic theory trajectory is analyzed.

As shown in fig. 5, when the single constant curvature segment is equivalent, the black curve at the outer side is the tail end track of the original motion model of the constant curvature segment; the outer gray curve is the tail end track of the equivalent model; it can be seen that when the axial deflection angle is too large, the equivalent model and the original model have deviation. However, in the engineering implementation, the angle θ of the axial deflection angle θ of each constant-curvature section of the continuous robot is limited due to the limitation of materials and the like, and is generally less than 60 °. When the axial deflection angle theta reaches 60 degrees, the deviation of the equivalent model and the original model is only 0.11 percent of the length L of the constant curvature segment; when 90 ° is reached, the deviation is also only 0.53%. By measuring the maximum axial deflection angle of each constant-curvature section of the segmented constant-curvature continuous robot, the maximum deviation between the equivalent method and the theoretical condition can be obtained through analysis in fig. 5, and therefore guidance is given to the maximum deflection angle limit applicable to each section in practical application.

It is understood that the equivalent method based on the above method can be used for any subsequent application and shall fall within the protection scope of the present invention.

An embodiment of the present application further provides a control apparatus, including a processor and a storage medium for storing a computer program; wherein a processor is adapted to perform at least the method as described above when executing the computer program.

Embodiments of the present application also provide a storage medium for storing a computer program, which when executed performs at least the method described above.

Embodiments of the present application further provide a processor, where the processor executes a computer program to perform at least the method described above.

The storage medium may be implemented by any type of volatile or non-volatile storage device, or combination thereof. Among them, the nonvolatile Memory may be a Read Only Memory (ROM), a Programmable Read Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a magnetic Random Access Memory (FRAM), a Flash Memory (Flash Memory), a magnetic surface Memory, an optical Disc, or a Compact Disc Read-Only Memory (CD-ROM); the magnetic surface storage may be disk storage or tape storage. Volatile Memory can be Random Access Memory (RAM), which acts as external cache Memory. By way of illustration, and not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), synchronous Static Random Access Memory (SSRAM), dynamic Random Access Memory (DRAM), synchronous Dynamic Random Access Memory (SDRAM), double Data Rate Synchronous Dynamic Random Access Memory (DDRSDRAM), double Data Rate Synchronous Random Access Memory (ESDRAM), enhanced Synchronous Dynamic Random Access Memory (ESDRAM), enhanced Synchronous Random Access Memory (DRAM), synchronous Random Access Memory (DRAM), direct Random Access Memory (DRmb Access Memory). The storage media described in connection with the embodiments of the invention are intended to comprise, without being limited to, these and any other suitable types of memory.

In the several embodiments provided in the present application, it should be understood that the disclosed system and method may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only a logical functional division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all the functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: a mobile storage device, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and various media capable of storing program codes.

Alternatively, the integrated unit of the present invention may be stored in a computer-readable storage medium if it is implemented in the form of a software functional module and sold or used as a separate product. Based on such understanding, the technical solutions of the embodiments of the present invention may be essentially implemented or a part contributing to the prior art may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a removable storage device, a ROM, a RAM, a magnetic or optical disk, or various other media capable of storing program code.

The methods disclosed in the several method embodiments provided in the present application may be combined arbitrarily without conflict to obtain new method embodiments.

Features disclosed in several of the product embodiments provided in the present application may be combined in any combination to yield new product embodiments without conflict.

The features disclosed in the several method or apparatus embodiments provided in the present application may be combined arbitrarily, without conflict, to arrive at new method embodiments or apparatus embodiments.

The foregoing is a further detailed description of the invention in connection with specific preferred embodiments and it is not intended to limit the invention to the specific embodiments described. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. It will be apparent to those skilled in the art that various equivalent substitutions and obvious modifications can be made without departing from the spirit of the invention, and all changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. A continuous robot kinematics equivalent method is characterized in that a kinematics equivalent method adopting a two-connecting-rod-four-joint equivalent model is used for carrying out equivalence on the continuous robot kinematics based on a segmental constant curvature assumption by using a rigid arm;

the kinematic equivalence comprises the following steps:

s1: dividing the continuous robot based on the subsection constant curvature hypothesis into a plurality of constant curvature sections, acquiring the length of each constant curvature section and distinguishing each constant curvature section;

s2: for each constant-curvature section, performing equivalence by using a rigid arm according to the length of each constant-curvature section; each constant curvature section is equivalent to two rigid connecting rods connected by four rotating joints and is equivalent within an error range through parameter constraint;

2. The continuum robot kinematic equivalent method of claim 1, wherein the length of each of the constant curvature segments is constant.

3. The continuum robot kinematic equivalent method of claim 1, wherein the parameter comprises a geometric relationship between an axial deflection angle and a deflection assist angle of the constant curvature segment.

4. The continuum robot kinematic equivalence method according to claim 3, wherein said equivalence comprises: short rod-long rod equivalent, long rod-short rod equivalent;

and obtaining the geometric relation between the axial deflection angle and the deflection auxiliary angle of the constant-curvature section according to the short rod-long rod equivalent.

5. The continuum robot kinematic equivalent method of claim 4, wherein a geometric relationship between the axial deflection angle and the deflection assist angle of the constant curvature segment satisfies:

；

further simplification results in:

；

wherein the content of the first and second substances,θis the axial deflection angle of the constant curvature segment,φis the yaw assist angle of the constant curvature segment,Lis the length of the constant curvature segment.

6. The continuous type robot kinematics equivalent method according to claim 5, wherein the equivalent parameters are obtained according to a long-short bar equivalent method: the configuration parameter state variable axial deflection angle of the constant curvature sectionθAxial rotation angleψEquivalent length of long polel ₁ =3/4LEquivalent short rod lengthl ₂ =1/4LEquivalent to a first deflection angleθ-φEquivalent second deflection angle, i.e. auxiliary deflection angleφ。

7. The kinematic equivalence method of continuum robots according to any of claims 1-6, further comprising:

s4: a kinematic equivalence method of evaluating the equivalence model.

8. Use of a continuum robot kinematic equivalence method according to any of the claims 1-7.