CN116277140A - Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof - Google Patents

Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof Download PDF

Info

Publication number
CN116277140A
CN116277140A CN202310170542.2A CN202310170542A CN116277140A CN 116277140 A CN116277140 A CN 116277140A CN 202310170542 A CN202310170542 A CN 202310170542A CN 116277140 A CN116277140 A CN 116277140A
Authority
CN
China
Prior art keywords
rigidity
flexible arm
tube
variable
rolling
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202310170542.2A
Other languages
Chinese (zh)
Inventor
李龙
郝晴
汪田鸿
金滔
张泉
田应仲
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Shanghai for Science and Technology
Original Assignee
University of Shanghai for Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Shanghai for Science and Technology filed Critical University of Shanghai for Science and Technology
Priority to CN202310170542.2A priority Critical patent/CN116277140A/en
Publication of CN116277140A publication Critical patent/CN116277140A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J18/00—Arms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J17/00—Joints
    • B25J17/02—Wrist joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
    • B25J19/06—Safety devices
    • B25J19/068—Actuating means with variable stiffness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1602—Programme controls characterised by the control system, structure, architecture
    • B25J9/1605—Simulation of manipulator lay-out, design, modelling of manipulator
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Landscapes

  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Manipulator (AREA)

Abstract

The invention relates to a variable-rigidity rolling joint flexible arm and a variable-rigidity method thereof, wherein the variable-rigidity rolling joint flexible arm comprises a flexible arm framework, a rigidity reinforcing mechanism, a positioning device, a driving platform and a driving cable; the flexible arm framework is of a hollow structure, the rigidity enhancing mechanism penetrates through the flexible arm framework, and the rigidity enhancing mechanism and the flexible arm framework are combined to form a rigidity-variable flexible arm; the flexible arm framework is fixed on the positioning device, and a plurality of driving cables sequentially penetrate through the flexible arm framework and the positioning device and are connected to the driving platform; the driving platform is used for controlling the driving cable to move so as to drive the variable-rigidity rolling joint flexible arm to move. The invention realizes the adjustability of the joint rigidity without changing the posture of the flexible arm, provides a rigidity changing method thereof, establishes a rigidity model, realizes the rigidity adjustable control of the flexible arm, and effectively increases the rigidity effect of the rolling joint flexible arm.

Description

Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof
Technical Field
The invention relates to the field of robots, in particular to a variable-rigidity rolling joint flexible arm and a variable-rigidity method thereof.
Background
With the increasing diversity of robot tasks, the traditional rigid mechanical robots are difficult to meet the increasingly complex task demands, and particularly in unstructured environments, novel flexible robots are increasingly and widely focused, are becoming more and more popular, and are advancing to practical use at a rapid speed. The flexible mechanical arm is used as an important component of the robot, has the advantages of high operation efficiency, light weight and flexible movement, and has important significance in application scenes such as aviation, operation and the like. The flexible mechanical arm has good flexibility and safety due to good flexibility, but when facing to contact operation with precision requirements, the flexible mechanical arm cannot bear too high load, and the working efficiency of the flexible mechanical arm is greatly reduced due to the flexibility. The proposal of variable rigidity well solves the contradiction between flexibility and operation precision, and the existing realization of variable rigidity is concentrated on the use of the rigidity-adjustable material, and has the problems of low response speed, great influence by environment and the like. Therefore, a rigidity-variable flexible arm mechanism is needed, which not only can realize accurate positioning of high rigidity under high-load operation, but also can move in a complex environment with lower rigidity, and improves the adaptability to the environment.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a variable stiffness rolling joint flexible arm and a variable stiffness method thereof.
The aim of the invention can be achieved by the following technical scheme:
a variable-rigidity rolling joint flexible arm comprises a flexible arm framework, a rigidity enhancing mechanism, a positioning device, a driving platform and a driving cable;
the flexible arm framework is of a hollow structure, the rigidity enhancing mechanism penetrates through the flexible arm framework, and the rigidity enhancing mechanism and the flexible arm framework are combined to form a rigidity-variable flexible arm;
the flexible arm framework is fixed on the positioning device, and a plurality of driving cables sequentially penetrate through the flexible arm framework and the positioning device and are connected to the driving platform;
the driving platform is used for controlling the driving cable to move so as to drive the variable-rigidity rolling joint flexible arm to move.
Further, the flexible arm framework comprises elastic ropes and rolling joints;
the rolling joints comprise a plurality of rolling joints, and the rolling joints are sequentially stacked;
the elastic ropes sequentially penetrate through the small holes on the rolling joints to be connected with the rolling joints, and the elastic ropes are used for preventing sliding among the rolling joints;
the driving cable sequentially passes through all the rolling joints, all the rolling joints are connected in series to form a two-degree-of-freedom flexible arm, and the driving cable is used for driving the flexible arm to realize left-right movement and up-down movement.
Further, the rigidity enhancing mechanism comprises a connecting cover, a silicone tube, a hose joint and an air pump tube;
the silica gel tube passes through the inside of the flexible arm framework;
the first end of the silicone tube is connected with the connecting cover, and the connecting cover is used for sealing the first end of the silicone tube;
the second end of the silicone tube is connected with the first end of the hose connector, the second end of the hose connector is connected with the first end of the air pump tube, and the second end of the air pump tube penetrates through the positioning module to be communicated with an air source;
the air source is used for inflating the silica gel tube through the air pump tube, so that the flexible arm framework displays different rigidity performances.
Further, the positioning device comprises a cable expanding device and a flexible arm fixing seat;
the top of the cable expansion device is fixedly connected with a flexible arm fixing seat; the flexible arm fixing seat is connected with a through hole at the proximal end of the flexible arm framework through a steel column;
the cable expanding device comprises a plurality of tracks at the bottom, pulleys are embedded on the tracks, a driving cable is connected with the pulleys, and the pulleys are used for guiding and expanding the direction of the driving cable so as to facilitate the connection of the driving cable with a driving platform.
Further, the driving platform comprises a plurality of screw rod stepping motors, the number of the screw rod stepping motors is the same as that of the driving cables, and each screw rod stepping motor is correspondingly connected with each driving cable;
the screw rod stepping motor is used for controlling extension and contraction of the driving cable, and further driving the flexible arm to move in different directions.
A rigidity changing method of a rigidity changing rolling joint flexible arm is applied to the rigidity changing rolling joint flexible arm, and comprises the following steps:
s1, outputting power by a screw rod stepping motor and pulling a driving cable, and recording initial tension applied to the driving cable as T 0 ；
S2, inflating the inside of the silica gel tube through an air source to realize the rigidity change of the variable rigidity rolling joint flexible arm;
s3, constructing a mathematical model of the flexible arm framework;
s4, based on an air spring hypothesis, establishing a stiffness model of the silicone tube;
s5, establishing a rigidity model of the rigidity enhancing mechanism;
s6, establishing a rigidity model of the variable-rigidity rolling joint flexible arm based on the mathematical model of the flexible arm framework, the rigidity model of the silicone tube and the rigidity model of the rigidity enhancing mechanism to obtain the rigidity of the variable-rigidity rolling joint flexible arm system;
wherein, step S2 includes the following procedures:
s21, when the inside of the silicone tube is not inflated, the rigidity of the flexible arm is in an original state, and the rigidity adjustment of the flexible arm is in a first state, namely P a Air pressure P is inflated in the silicone tube a ＝0；
S22, when the inside of the silica gel tube is inflated and the silica gel tube is not in contact with the hollow inner wall of the flexible arm framework, the rigidity of the flexible arm is regulated to be in a second state, and the wall thickness is recorded as delta d si ，P m Is just contacted with the silica gel tubeThe air pressure in the tube when the inner wall is smaller than 0 < P a ≤P m ；
S23, when the silicone tube is in contact with the hollow inner wall of the flexible arm framework due to air pressure for inflating the inside of the silicone tube, the silicone tube generates micro-protrusion at the notch part of the flexible arm framework, and the rigidity of the flexible arm is regulated to be in a third state, and the wall thickness is recorded as delta d msi ，P a ＞P m 。
Further, the mathematical model of the flexible arm skeleton comprises a kinematic model representing a joint space to drive space mapping relationship; aiming at the condition of left-right movement of the flexible arm, the expression of the kinematic model is as follows:
Figure BDA0004097884650000031
Figure BDA0004097884650000032
in Deltad l For the length variation of the left drive cable Δd r For the length variation of the right drive cable, θ is the angle of rotation of the single rolling joint, R is the rolling radius of the rolling joint, and α is the effective half angle of the rolling joint.
Further, the stiffness model of the silicone tube comprises a vertical stiffness model, and the expression of the vertical stiffness model is as follows:
Figure BDA0004097884650000033
p in the formula 0 At atmospheric pressure, P a The pressure of the air in the silica gel tube is A eff V as effective bearing area 0 Is of air pressure P a The inner volume of the silica gel tube;
when the stiffness adjustment of the flexible arm is in a second state, the specific expression of the related parameters is as follows:
Figure BDA0004097884650000034
Figure BDA0004097884650000041
d in si Is the outer diameter d of the state disilicide tube si Is the inner diameter of the two-state silica gel tube, delta d si The wall thickness of the silica gel tube is in a state, and h is the effective length of the silica gel tube;
when the stiffness adjustment of the flexible arm is in a third state, the specific expression of the related parameters is as follows:
Figure BDA0004097884650000042
Figure BDA0004097884650000043
d in msi Is the outer diameter d of the state trisilicon tube msi Is the inner diameter of the three-state silicone tube, delta d msi Wall thickness of the trisilicon tube in the state of l 0 Is the effective length of a single discrete air spring.
Further, the stiffness model construction step of the stiffness enhancing mechanism includes:
s1, when the rigidity adjustment of the flexible arm is in a first state, the rigidity is enhanced to 0, and the rigidity of the rigidity enhancing mechanism is equivalent to two rigidity k 1 Linear springs of =0 are connected in parallel;
s2, when the rigidity adjustment of the flexible arm is in a second state, the rigidity enhancement is based on the rigidity of the whole silicone tube, and the rigidity of the rigidity enhancement mechanism is equivalent to two rigidities of k 2 Is connected in parallel with the linear spring to increase the compensation coefficient lambda 2 ，k 2 The expression is:
Figure BDA0004097884650000044
K si2 is a vertical rigidity model of the state disilicide tube;
s3, when the rigidity adjustment of the flexible arm is in a third state, the rigidity enhancement is based on the rigidity of the discrete silica gel tube, and the rigidity of the rigidity enhancement mechanism is equivalent to four rigidity of k 3 The expression is as follows:
k 3 ＝2λ 3 K si3
K si3 is a vertical rigidity model of the state trisilicon tube.
Further, according to the principle of energy conservation, a static balance equation of the variable stiffness rolling joint flexible arm is obtained, wherein the expression of the static balance equation is as follows:
Π＝∑W wire +∑W spring -∑W F
where pi is the sum of the total energy of the equilibrium states of the flexible arms, W wire Work for driving the cable, W spring To simplify the work done by the linear spring, W F Work done for external force load;
according to different rigidity states of the flexible arm, the method specifically comprises the following steps:
s1, when the stiffness adjustment of the flexible arm is in a first state, a balance equation expression is as follows:
Figure BDA0004097884650000051
in DeltaL l0 For the length of the initial left drive cable ΔL l For the final left drive cable length ΔL r0 For the length of the initial right drive cable ΔL r For the final right drive cable length, Δl is the total variation of the drive cable, s is the horizontal displacement under the action of the external force load F;
s2, when the stiffness adjustment of the flexible arm is in a second state, the expression of the balance equation is as follows:
Figure BDA0004097884650000052
s3, when the stiffness adjustment of the flexible arm is in a third state, the expression of the balance equation is as follows:
Figure BDA0004097884650000053
the static balance equation comprises a driving cable linear mechanical model, joint angle constraint conditions and load displacement constraint conditions; the driving cable linear mechanical model expression is as follows:
T wire ＝ax+T 0
wherein a is a coefficient, T 0 For initial drive cable tension;
the joint angle constraint condition expression is as follows:
Figure BDA0004097884650000054
where Θ is the total bending angle of the initial flexible arm, θ i N is the number of the motion joints for the bending angle of each motion joint;
aiming at the condition of left-right movement of the flexible arm, the specific expression of the load displacement constraint condition is as follows:
s＝3Hsinθ 1 +Hsin(θ 1 +θ 2 )+3Hsin(θ 1 +θ 2 +θ 3 )+H 1 sin(θ 1 +θ 2 +θ 3 +θ 4 )
＝7Hθ 1 +4Hθ 2 +3Hθ 3 +H 1 (θ 1 +θ 2 +θ 3 +θ 4 )
wherein H is the height of a single rolling joint in the middle of the flexible arm, H 1 The height of the rolling joint at the proximal end and the distal end of the flexible arm;
according to the minimum energy principle, solving the equilibrium equation expression is:
Figure BDA0004097884650000061
simultaneously solving to obtain specific angle values of all joints;
the rigidity model expression of the rigidity-variable rolling joint flexible arm is as follows:
Figure BDA0004097884650000062
substituting the obtained specific angle values of each joint to obtain the rigidity of the variable rigidity rolling joint flexible arm system.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a rigidity-variable rolling joint flexible arm and a rigidity-variable method. Based on the variation process of the rigidity enhancement of the flexible arm, the invention provides three states of the rigidity enhancement of the flexible arm, from a continuous rigidity enhancement state to a discrete rigidity enhancement state, and provides a simple rigidity varying method; by combining kinematics, air spring theory and statics, a stiffness model of the rolling joint flexible arm is established aiming at different stiffness change states, and the stiffness modeling problem is solved. The variable-rigidity flexible mechanical arm can realize high-rigidity accurate positioning under high-load operation, can move in a complex environment with lower rigidity, and has high adaptability to the environment.
Drawings
FIG. 1 is a schematic view of a flexible arm of a rolling joint with variable rigidity according to embodiment 1 of the present invention;
FIG. 2-1 is a schematic structural view of a rigidity reinforcing mechanism in embodiment 1 of the present invention;
fig. 2-2 is a schematic structural view of the cable expansion device in embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of a method for varying stiffness of a compliant arm of a rolling joint of variable stiffness according to example 2 of the present invention;
FIG. 4 is a simplified model diagram of a method for varying stiffness of a compliant arm of a rolling joint of varying stiffness according to example 2 of the present invention;
FIG. 5 is a force balance schematic diagram of a compliant arm of a rolling joint of variable stiffness according to example 2 of the present invention;
fig. 6 is a schematic diagram showing the stiffness change process of a roll joint flexible arm with variable stiffness according to embodiment 2 of the present invention.
The corresponding relation between the reference numbers and the components in the drawings is as follows: the device comprises a 1-flexible arm framework, a 2-rigidity enhancing mechanism, a 3-positioning device, a 4-driving platform, a 6-air pump pipe, a 7-driving cable, an 8-screw rod stepping motor, a 9-connecting cover, a 10-silicone pipe, an 11-hose connector, a 12-elastic rope, a 13-rolling joint, a 14-cable expanding device, a 15-flexible arm fixing seat and a 16-pulley.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, if there are terms such as "upper", "lower", "left", "right", etc., indicating azimuth or positional relationships based on the azimuth or positional relationships shown in the drawings, only for convenience of description of the present invention and simplification of description, it will be understood to those skilled in the art that the specific meanings of the terms are as appropriate.
Example 1
Aiming at the problems that a flexible mechanical arm in the prior art is low in response speed, is greatly influenced by environment, can not simultaneously meet high load requirements and high precision requirements and the like, the invention provides a variable stiffness rolling joint flexible arm and a variable stiffness method thereof.
As shown in fig. 1 and fig. 2-1 and 2-2, a preferred embodiment of a variable stiffness roll joint flexible arm provided by the invention comprises a flexible arm framework 1, a stiffness enhancing mechanism 2, a positioning device 3, a driving platform 4 and a driving cable 7;
the flexible arm framework 1 is of a hollow structure, the rigidity enhancing mechanism 2 penetrates through the flexible arm framework 1, and the rigidity enhancing mechanism 2 and the flexible arm framework 1 are combined to form a rigidity-variable flexible arm; the flexible arm framework 1 is fixed on the positioning device 3, and a plurality of driving cables 7 sequentially penetrate through the flexible arm framework 1 and the positioning device 3 and are connected to the driving platform 4; the driving platform 4 is used for controlling the driving cable 7 to move so as to drive the variable stiffness rolling joint flexible arm to move.
As shown in fig. 2-1, the flexible arm skeleton 1 comprises a plurality of rolling joints 13, elastic ropes 12 and four driving cables 7, wherein the rolling joints 13 are connected in series through the driving cables 7 in a certain stacking mode to form a two-degree-of-freedom flexible arm, so that left-right movement and up-down movement are realized; the rolling joints 13 are provided with small holes, the elastic ropes 12 sequentially penetrate through the small holes on the rolling joints 13 to be connected with the rolling joints 13, and the elastic ropes 12 are used for preventing sliding among the rolling joints;
as shown in fig. 1 and 2-1, the rigidity enhancing mechanism 2 comprises a connecting cover 9, a silica gel tube 10, a hose joint 11 and an air pump tube 6; the silicone tube 10 passes through the inside of the flexible arm framework 1; the first end of the silicone tube 10 is connected with the connecting cover 9, and the connecting cover 9 is used for sealing the first end of the silicone tube 10; the second end of the silicone tube 10 is connected with the first end of the hose joint 11, the second end of the hose joint 11 is connected with the first end of the air pump tube 6, and the second end of the air pump tube 6 passes through the positioning module 3 to be communicated with an air source; the air source charges the silica gel tube 10 through the air pump tube 6, so that the flexible arm framework 1 displays different rigidity performances.
As shown in fig. 1 and 2-1, the positioning device 3 comprises a cable expansion device 14 and a flexible arm fixing seat 15;
the top of the cable expansion device 14 is fixedly connected with a flexible arm fixing seat 15, four tracks are arranged at the bottom of the cable expansion device 14, the four tracks jointly form an X shape, a pulley 16 is embedded on each track, the driving cable 7 is connected with the pulley 16, the pulley 16 is used for guiding and expanding the direction of the driving cable 7, and the driving cable 7 is conveniently connected with the driving platform 4;
the air pump pipe 6 passes through the cable expansion device 14 and is led out from the crossing point of each track;
the flexible arm fixing seat 15 is connected with a through hole at the proximal end of the flexible arm framework 1 through a steel column. The variable stiffness rolling flexible arm determines the initial position with the aid of the positioning device 3.
As shown in fig. 1, the driving platform 4 includes four screw rod stepping motors 8, and the extension and contraction of the driving cable 7 can be realized by the single-chip microcomputer driving motor, so that the movement of the flexible arm in different directions can be realized.
Example 2
Fig. 3 to 6 show an embodiment of a variable stiffness method for a variable stiffness roll joint flexible arm according to the present invention, which is applied to a variable stiffness roll joint flexible arm according to embodiment 1, wherein a proximal end of the flexible arm is fixed, the flexible arm is in an upright state, and the embodiment uses a plane in a left-right movement direction as an example to describe a same up-down movement.
As shown in fig. 3, the stiffness varying method includes the steps of:
s1, a screw rod stepping motor 8 outputs power and pulls four driving cables 7, and initial tension applied to the driving cables is T 0 ；
S2, the rigidity enhancing mechanism is used for inflating the inside of the silica gel tube through an air source, so that rigidity change of the flexible arm of the rolling joint is realized;
wherein, step S2 includes the following procedures:
s21, when the inside of the silica gel tube is not inflated, namely no gas is driven, the rigidity of the flexible arm is in the original state, and the rigidity adjustment of the flexible arm is in the first state at the moment, P a ＝0；
S22, when the inside of the silica gel tube is inflated, and the silica gel tube is not contacted with the hollow inner wall of the flexible arm framework, the whole silica gel tube can be regarded as an air spring, and the rigidity of the flexible arm is regulated to be in a second state, and the wall thickness of the silica gel tube is delta d si ，P a Air pressure P is inflated in the silicone tube m The pressure in the tube just contacting the inner wall is 0 < P a ≤P m ；
S23, when the air pressure for inflating the inside of the silicone tube enables the silicone tube to be in contact with the hollow inner wall of the flexible arm framework, the silicone tube generates tiny protrusions at the notch part of the flexible arm framework, and at the moment, the rigidity enhancement effect of the silicone tube is only reflected inThe tiny protruding portions can therefore be seen as a silicone tube with several discrete air springs in series, at which time the flexible arm stiffness adjustment is said to be in state three, the silicone tube having a wall thickness Δd msi The pressure in the tube is P a ＞P m 。
Based on the rigidity changing method, a rigidity model is established, according to the space geometric relation, a mathematical model of a flexible arm framework is firstly established, then a rigidity model of a silicone tube is established based on an air spring hypothesis, and then a rigidity model of a rigidity enhancing mechanism is established, and finally a rigidity model of a rigidity-changing rolling joint flexible arm is established, wherein the vertical movement is the same by taking a plane in a left-right movement direction as an example.
The mathematical model of the flexible arm skeleton comprises a kinematic model representing the mapping relation between joint space and driving space, and the expression is as follows:
Figure BDA0004097884650000091
Figure BDA0004097884650000092
in Deltad l For the length variation of the left drive cable Δd r For the length variation of the right drive cable, θ is the angle of rotation of the single joint, R is the rolling radius of the rolling joint, and α is the effective half angle of the rolling joint.
Further, the stiffness model of the silicone tube comprises a vertical stiffness model, and the expression is as follows:
Figure BDA0004097884650000093
p in the formula 0 At atmospheric pressure, P a The pressure of the air in the silica gel tube is A eff V as effective bearing area 0 Is of air pressure P a The internal volume of the silica gel tube.
When the stiffness adjustment of the flexible arm is in a second state, the specific expression of the related parameters is as follows:
Figure BDA0004097884650000094
Figure BDA0004097884650000095
d in si Is the outer diameter d of the state disilicide tube si Is the inner diameter of the two-state silica gel tube, delta d si The wall thickness of the silica gel tube is in a state, and h is the effective length of the silica gel tube. By taking the expressions (4), (5) into (3), K can be obtained si2 。
When the stiffness adjustment of the flexible arm is in a third state, the specific expression of the related parameters is as follows:
Figure BDA0004097884650000096
Figure BDA0004097884650000097
d in msi Is the outer diameter d of the state trisilicon tube msi Is the inner diameter of the three-state silicone tube, delta d msi Wall thickness of the trisilicon tube in the state of l 0 Is the effective length of a single discrete air spring. By taking the expressions (6), (7) into (3), K can be obtained si3 。
As shown in fig. 4, the stiffness model of the stiffness enhancing mechanism may be further simplified, specifically including the following steps:
s1, when the rigidity adjustment of the flexible arm is in a first state, the rigidity is enhanced to 0, or the rigidity of the rigidity enhancing mechanism can be equivalently expressed as two rigidity k 1 Linear springs of =0 are connected in parallel;
s2, when the rigidity adjustment of the flexible arm is in a second state, the silicone tube is not contacted with the inner wall, the rigidity enhancement is based on the rigidity of the whole silicone tube, and the rigidity of the rigidity enhancement mechanism can be equivalent to two rigidity of k 3 Is of the (2)The springs are connected in parallel to increase the compensation coefficient lambda 2 ，k 2 The expression is:
Figure BDA0004097884650000101
s3, when the rigidity adjustment of the flexible arm is in a third state, the silicone tube is completely contacted with the inner wall, the rigidity enhancement is based on the rigidity of the discrete silicone tube, and the rigidity of the rigidity enhancement mechanism can be equivalent to four rigidity k 3 Is connected in parallel after being discretely connected in series, and increases the compensation coefficient lambda 3 ，k 3 The expression is:
k 3 ＝2λ 3 K si3 (9)
as shown in fig. 5, when the end of the flexible arm is loaded by external force, the upright flexible arm can be bent in an S shape, and according to the principle of energy conservation, the static balance equation of the flexible arm of the variable stiffness rolling joint can be obtained as follows:
Π＝∑W wire +∑W spring -∑W F (10)
where pi is the sum of the total energy of the equilibrium states of the flexible arms, W wire Work for driving the cable, W spring To simplify the work done by the linear spring, W F Work is performed for the external force load.
According to different rigidity states of the flexible arm, the method specifically comprises the following steps:
s1, when the stiffness adjustment of the flexible arm is in a first state, the expression of a balance equation is as follows:
Figure BDA0004097884650000102
in DeltaL l0 For the length of the initial left drive cable ΔL l For the final left drive cable length ΔL r0 For the length of the initial right drive cable ΔL r For the final right drive cable length Δl is the total variation of the drive cable and s is the horizontal displacement under the action of the external force load F.
S2, when the stiffness adjustment of the flexible arm is in a second state, the expression of the balance equation is as follows:
Figure BDA0004097884650000103
s3, when the stiffness adjustment of the flexible arm is in a state III, the expression of the balance equation is as follows:
Figure BDA0004097884650000111
the static balance equation comprises a driving cable linear mechanical model, joint angle constraint conditions and load displacement constraint conditions, and the driving cable linear mechanical model expression is obtained as follows:
T wire ＝ax+T 0 (14)
wherein a is a coefficient, which is obtained by experimental fitting, T 0 For initial drive cable tension.
The joint angle constraint condition expression is:
Figure BDA0004097884650000112
where Θ is the total bending angle of the initial flexible arm, θ i For each bending angle of the motion joint, n is the number of motion joints, and n is 4 in this embodiment.
Under the action of external force F, the joint angle change generated by the variable-rigidity flexible arm is tiny, so that an equivalent infinitely small substitution formula, sin theta approximately equal theta, can be used, and the specific expression of the load displacement s constraint condition is as follows:
Figure BDA0004097884650000113
wherein H is the height of a single rolling joint in the middle of the flexible arm, H 1 The height of the roll joint is the proximal and distal ends of the flexible arm.
According to the minimum energy principle, solving the equilibrium equation expression is:
Figure BDA0004097884650000114
the specific angle values of the joints can be obtained by taking the expressions (14), (15) and (16) into the expression (17).
Further, the stiffness model expression of the variable stiffness roll joint flexible arm is:
Figure BDA0004097884650000115
and (3) bringing the angle value of the joint obtained in the expression (17) into the expression (18) to finally obtain the rigidity of the variable rigidity rolling joint flexible arm system.
As shown in FIG. 6, a curve is fitted to the stiffness variation of the flexible arm, and its theoretical stiffness values are calculated for different air pressure values, it can be seen that at air pressure P m In the vicinity, there is a relatively significant abrupt change in stiffness when the air pressure is less than P m When the rigidity is slowly increased; when the air pressure is greater than P m The stiffness trend becomes faster. The variation trend accords with the rigidity enhancement mechanism of the flexible arm, so that the rigidity-variable rolling joint flexible arm can be proved to have better rigidity-variable capability. Therefore, the variable-rigidity flexible arm provided by the invention can realize high-rigidity accurate positioning under high-load operation, can move in a complex environment with lower rigidity, and has high environmental adaptability.
The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention by one of ordinary skill in the art without undue burden. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims (10)

1. The variable-rigidity rolling joint flexible arm is characterized by comprising a flexible arm framework (1), a rigidity enhancing mechanism (2), a positioning device (3), a driving platform (4) and a driving cable (7);
the flexible arm framework (1) is of a hollow structure, the rigidity enhancing mechanism (2) penetrates through the flexible arm framework (1), and the rigidity enhancing mechanism (2) and the flexible arm framework (1) are combined to form a rigidity-variable flexible arm;
the flexible arm framework (1) is fixed on the positioning device (3), and a plurality of driving cables (7) sequentially penetrate through the flexible arm framework (1) and the positioning device (3) to be connected to the driving platform (4);
the driving platform (4) is used for controlling the driving cable (7) to move so as to drive the variable-rigidity rolling joint flexible arm to move.
2. The variable stiffness rolling joint flexible arm according to claim 1, wherein the flexible arm framework (1) comprises elastic ropes (12) and rolling joints (13);
the rolling joints (13) are multiple, and the rolling joints (13) are stacked in sequence;
the elastic ropes (12) sequentially penetrate through the small holes on the rolling joints (13) to be connected with the rolling joints (13), and the elastic ropes (12) are used for preventing sliding among the rolling joints;
the driving cable (7) sequentially passes through all the rolling joints (13), all the rolling joints (13) are connected in series to form a two-degree-of-freedom flexible arm, and the driving cable (7) is used for driving the flexible arm to realize left-right movement and up-down movement.
3. The variable stiffness roll joint flexible arm according to claim 2, wherein the stiffness enhancing mechanism (2) comprises a connecting cover (9), a silicone tube (10), a hose connector (11) and an air pump tube (6);
the silicone tube (10) passes through the inside of the flexible arm framework (1);
the first end of the silicone tube (10) is connected with the connecting cover (9), and the connecting cover (9) is used for sealing the first end of the silicone tube (10);
the second end of the silicone tube (10) is connected with the first end of the hose connector (11), the second end of the hose connector (11) is connected with the first end of the air pump tube (6), and the second end of the air pump tube (6) passes through the positioning module (3) to be communicated with an air source;
the air source is used for inflating the silica gel tube (10) through the air pump tube (6), so that the flexible arm framework (1) shows different rigidity performances.
4. A variable stiffness roll joint flexible arm according to claim 3, characterized in that the positioning device (3) comprises a cable extension device (14) and a flexible arm fixing seat (15);
the top of the cable expanding device (14) is fixedly connected with a flexible arm fixing seat (15); the flexible arm fixing seat (15) is connected with a through hole at the proximal end of the flexible arm framework (1) through a steel column;
the cable expanding device is characterized in that a plurality of tracks are arranged at the bottom of the cable expanding device (14), pulleys (16) are embedded in the tracks, the driving cable (7) is connected with the pulleys (16), and the pulleys (16) are used for guiding and expanding the direction of the driving cable (7) so as to facilitate connection of the driving cable (7) and the driving platform (4).
5. A variable stiffness roll joint flexible arm according to claim 1, characterized in that the drive platform (4) comprises a number of screw stepper motors (8), the number of screw stepper motors (8) being the same as the number of drive cables (7), each screw stepper motor (8) being correspondingly connected to a respective drive cable (7);
the screw rod stepping motor (8) is used for controlling the extension and contraction of the driving cable (7), so that the flexible arm is driven to move in different directions.
6. A method for changing rigidity of a rigidity-changing rolling joint flexible arm, which is characterized by being applied to the rigidity-changing rolling joint flexible arm according to any one of claims 1-5, and comprising the following steps:
s1, outputting power by a screw rod stepping motor and pulling a driving cable, and recording initial tension applied to the driving cable as T 0 ；
S2, inflating the inside of the silica gel tube through an air source to realize the rigidity change of the variable rigidity rolling joint flexible arm;
s3, constructing a mathematical model of the flexible arm framework;
s4, based on an air spring hypothesis, establishing a stiffness model of the silicone tube;
s5, establishing a rigidity model of the rigidity enhancing mechanism;
s6, establishing a rigidity model of the variable-rigidity rolling joint flexible arm based on the mathematical model of the flexible arm framework, the rigidity model of the silicone tube and the rigidity model of the rigidity enhancing mechanism to obtain the rigidity of the variable-rigidity rolling joint flexible arm system;
wherein, step S2 includes the following procedures:
s21, when the inside of the silicone tube is not inflated, the rigidity of the flexible arm is in an original state, and the rigidity adjustment of the flexible arm is in a first state, namely P a Air pressure P is inflated in the silicone tube a ＝0；
S22, when the inside of the silica gel tube is inflated and the silica gel tube is not in contact with the hollow inner wall of the flexible arm framework, the rigidity of the flexible arm is regulated to be in a second state, and the wall thickness is recorded as delta d si ，P m The pressure in the tube when the silica gel tube just contacts the inner wall is more than 0 and less than P a ≤P m ；
S23, when the silicone tube is in contact with the hollow inner wall of the flexible arm framework due to air pressure for inflating the inside of the silicone tube, the silicone tube generates micro-protrusion at the notch part of the flexible arm framework, and the rigidity of the flexible arm is regulated to be in a third state, and the wall thickness is recorded as delta d msi ，P a ＞P m 。
7. The method of varying stiffness of a rolling joint flexible arm according to claim 6, wherein the mathematical model of the flexible arm skeleton comprises a kinematic model representing joint space to drive space mapping; aiming at the condition of left-right movement of the flexible arm, the expression of the kinematic model is as follows:
Figure FDA0004097884630000031
Figure FDA0004097884630000032
in Deltad l For the length variation of the left drive cable Δd r For the length variation of the right drive cable, θ is the angle of rotation of the single rolling joint, R is the rolling radius of the rolling joint, and α is the effective half angle of the rolling joint.
8. The method for changing the rigidity of the flexible arm of the rigidity-changing rolling joint according to claim 6, wherein the rigidity model of the silicone tube comprises a vertical rigidity model, and the expression of the vertical rigidity model is as follows:
Figure FDA0004097884630000033
p in the formula 0 At atmospheric pressure, P a The pressure of the air in the silica gel tube is A eff V as effective bearing area 0 Is of air pressure P a The inner volume of the silica gel tube;
when the stiffness adjustment of the flexible arm is in a second state, the specific expression of the related parameters is as follows:
Figure FDA0004097884630000034
Figure FDA0004097884630000035
d in si Is the outer diameter d of the state disilicide tube si Is the inner diameter of the two-state silica gel tube, delta d si The wall thickness of the silica gel tube is in a state, and h is the effective length of the silica gel tube;
when the stiffness adjustment of the flexible arm is in a third state, the specific expression of the related parameters is as follows:
Figure FDA0004097884630000036
Figure FDA0004097884630000037
d in msi Is the outer diameter d of the state trisilicon tube msi Is the inner diameter of the three-state silicone tube, delta d msi Wall thickness of the trisilicon tube in the state of l 0 Is the effective length of a single discrete air spring.
9. The method for changing the rigidity of the flexible arm of the rigidity-changing rolling joint according to claim 8, wherein the rigidity model constructing step of the rigidity-enhancing mechanism comprises:
s1, when the rigidity adjustment of the flexible arm is in a first state, the rigidity is enhanced to 0, and the rigidity of the rigidity enhancing mechanism is equivalent to two rigidity k 1 Linear springs of =0 are connected in parallel;
s2, when the rigidity adjustment of the flexible arm is in a second state, the rigidity enhancement is based on the rigidity of the whole silicone tube, and the rigidity of the rigidity enhancement mechanism is equivalent to two rigidities of k 2 Is connected in parallel with the linear spring to increase the compensation coefficient lambda 2 ，k 2 The expression is:
Figure FDA0004097884630000041
K si2 is a vertical rigidity model of the state disilicide tube;
s3, when the rigidity adjustment of the flexible arm is in a third state, the rigidity enhancement is based on the rigidity of the discrete silica gel tube, and the rigidity of the rigidity enhancement mechanism is equivalent to four rigidity of k 3 The expression is as follows:
k 3 ＝2λ 3 K si3
K si3 is a vertical rigidity model of the state trisilicon tube.
10. The method for changing the rigidity of the variable rigidity rolling joint flexible arm according to claim 9, wherein a static balance equation of the variable rigidity rolling joint flexible arm is obtained according to an energy conservation principle, and the expression of the static balance equation is as follows:
Π＝∑W wire +∑W spring -∑W F
where pi is the sum of the total energy of the equilibrium states of the flexible arms, W wire Work for driving the cable, W spring To simplify the work done by the linear spring, W F Work done for external force load;
according to different rigidity states of the flexible arm, the method specifically comprises the following steps:
s1, when the stiffness adjustment of the flexible arm is in a first state, a balance equation expression is as follows:
Figure FDA0004097884630000042
in DeltaL l0 For the length of the initial left drive cable ΔL l For the final left drive cable length ΔL r0 For the length of the initial right drive cable ΔL r For the final right drive cable length, Δl is the total variation of the drive cable, s is the horizontal displacement under the action of the external force load F;
s2, when the stiffness adjustment of the flexible arm is in a second state, the expression of the balance equation is as follows:
Figure FDA0004097884630000043
s3, when the stiffness adjustment of the flexible arm is in a third state, the expression of the balance equation is as follows:
Figure FDA0004097884630000051
the static balance equation comprises a driving cable linear mechanical model, joint angle constraint conditions and load displacement constraint conditions; the driving cable linear mechanical model expression is as follows:
T wire ＝ax+T 0
wherein a is a coefficient, T 0 For initial drive cable tension;
the joint angle constraint condition expression is as follows:
Figure FDA0004097884630000052
where Θ is the total bending angle of the initial flexible arm, θ i N is the number of the motion joints for the bending angle of each motion joint;
aiming at the condition of left-right movement of the flexible arm, the specific expression of the load displacement constraint condition is as follows:
s＝3Hsinθ 1 +Hsin(θ 1 +θ 2 )+3Hsin(θ 1 +θ 2 +θ 3 )+H 1 sin(θ 1 +θ 2 +θ 3 +θ 4 )
＝7Hθ 1 +4Hθ 2 +3Hθ 3 +H 1 (θ 1 +θ 2 +θ 3 +θ 4 )
wherein H is the height of a single rolling joint in the middle of the flexible arm, H 1 The height of the rolling joint at the proximal end and the distal end of the flexible arm;
according to the minimum energy principle, solving the equilibrium equation expression is:
Figure FDA0004097884630000053
simultaneously solving to obtain specific angle values of all joints;
the rigidity model expression of the rigidity-variable rolling joint flexible arm is as follows:
Figure FDA0004097884630000054
substituting the obtained specific angle values of each joint to obtain the rigidity of the variable rigidity rolling joint flexible arm system.
CN202310170542.2A 2023-02-27 2023-02-27 Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof Pending CN116277140A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310170542.2A CN116277140A (en) 2023-02-27 2023-02-27 Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310170542.2A CN116277140A (en) 2023-02-27 2023-02-27 Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof

Publications (1)

Publication Number Publication Date
CN116277140A true CN116277140A (en) 2023-06-23

Family

ID=86793483

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310170542.2A Pending CN116277140A (en) 2023-02-27 2023-02-27 Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof

Country Status (1)

Country Link
CN (1) CN116277140A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117811280A (en) * 2024-02-29 2024-04-02 清华大学 Reluctance motor and design method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117811280A (en) * 2024-02-29 2024-04-02 清华大学 Reluctance motor and design method thereof

Similar Documents

Publication Publication Date Title
CN110270987B (en) Pneumatic soft crawling robot and manufacturing and control method thereof
Liao et al. Soft rod-climbing robot inspired by winding locomotion of snake
CN109249428B (en) Tail end Cartesian space rigidity modeling method of rope-driven linkage type mechanical arm
JP5629484B2 (en) Robot hand with human-like finger
CN112476478B (en) Bionic rope-driven four-degree-of-freedom arm oriented to man-machine cooperation
CN111216129B (en) Active-passive combined series-parallel force feedback equipment gravity compensation method
CN116277140A (en) Variable-rigidity rolling joint flexible arm and variable-rigidity method thereof
Xu et al. Design and tension modeling of a novel cable-driven rigid snake-like manipulator
CN113427503B (en) Ripple pneumatic soft driver and soft manipulator
JP5212797B2 (en) Haptic manipulator
US11305420B2 (en) Articulated multi-link robotic tail systems and methods
CN110271002A (en) The Dynamic Modeling and its rope tension optimization method of rope driving coordinated type mechanical arm
CN110561425A (en) Rope-driven flexible robot force and position hybrid control method and system
WO2023216544A1 (en) Transmission mechanism for micro crawling robot, and micro crawling robot
CN113183144A (en) Rolling joint continuum mechanical arm driven by cable
CN115092280B (en) Soft flexible trunk and soft flexible bionic wall climbing robot
CN107121930B (en) Six Degree-of-Freedom Parallel Platform motion control method based on dummy model
CN108621197B (en) Variable-rigidity control device for rope-driven robot
JP3989943B2 (en) Flapping levitation moving device
Chen et al. A pneumatic–hydraulic hybrid actuator for underwater soft robot swimming and crawling
He et al. Kinematic design of a serial-parallel hybrid finger mechanism actuated by twisted-and-coiled polymer
Gong et al. Untethered cable-driven soft actuators for quadruped robots
Lim et al. Tension optimization for cable-driven parallel manipulators using gradient projection
Wang et al. The kinematic analysis and stiffness optimization for an 8-DOF cable-driven manipulator
Salgueiro et al. Towards a highly integrated 3D printed soft continuum manipulator

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination