CN114571466B - Rigidity-variable device, rigidity-variable method thereof and modeling method of rigidity model - Google Patents
Rigidity-variable device, rigidity-variable method thereof and modeling method of rigidity model Download PDFInfo
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- CN114571466B CN114571466B CN202210357022.8A CN202210357022A CN114571466B CN 114571466 B CN114571466 B CN 114571466B CN 202210357022 A CN202210357022 A CN 202210357022A CN 114571466 B CN114571466 B CN 114571466B
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- 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
- B25J9/1628—Programme controls characterised by the control loop
- B25J9/163—Programme controls characterised by the control loop learning, adaptive, model based, rule based expert control
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- 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
Abstract
The invention relates to the technical field of bionic mechanisms, in particular to a rigidity changing device, a rigidity changing method thereof and a modeling method of a rigidity model. The invention realizes the control of simulating the adjustable rigidity of human arms by simulating the simulation of the human skeletal muscle system and dynamically simulating and adjusting the rigidity of artificial muscles.
Description
Technical Field
The invention relates to the technical field of bionic mechanisms, in particular to a variable stiffness device, a variable stiffness method thereof and a modeling method of a stiffness model.
Background
At present, in order to reduce the weight and inertia of the humanoid arm body and improve the flexibility and the high-speed motion performance, a rope driving technology is increasingly applied to the field of humanoid arm research by more and more students. The technology is realized by placing a driving motor and a speed reducer on a base, driving a joint to move through a rope, and reducing the weight of an execution link of the humanoid arm. However, due to the flexibility and unidirectional stress characteristics of the rope, the variation range of the rigidity is limited, the rope does not have safety and flexibility when man-machine interaction is performed in a high-rigidity state, and the rope is poor in position control precision and low in response speed in a low-rigidity state.
The prior art discloses a bionic parallel robot driven by a rigidity-adjustable rope, which comprises a movable platform, a fixed platform, a supporting spring fixed between the movable platform and the fixed platform, a linear bearing, a plane bearing and a driving rope. The lower end of the supporting spring is fixed on the fixed platform, and the upper end of the supporting spring is connected with the movable platform through a plane bearing. The support spring is internally provided with an upper spine, a universal joint and a lower spine, the linear bearing is fixed on the movable platform and connected with the upper end of the upper spine, the lower end of the upper spine is connected with the upper end of the universal joint, the lower end of the universal joint is connected with the upper end of the lower spine, the lower end of the lower spine is fixed on the fixed platform, one end of the driving rope is fixed on the movable platform, and the other end of the driving rope penetrates through the fixed platform to serve as a driving end. The bionic parallel robot has the characteristics of adjustable rigidity, visual kinematic analysis and calculation, flexible motion and the like.
However, the defects of nonlinear concentration of the rigidity change interval and the like in the scheme are unfavorable for research.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a variable stiffness device, a variable stiffness method thereof and a modeling method of a stiffness model, wherein the stiffness of artificial muscles can be dynamically simulated and adjusted through bionics of a human skeletal muscle system, so that the adjustable control of simulating the stiffness of human arms is realized.
In order to solve the technical problems, the invention adopts the following technical scheme:
the utility model provides a changeable bionic mechanism of rigidity, including fixed platform, movable platform, fixed platform and movable platform rotate to be connected and constitute the joint support, the both sides of joint support all are equipped with flexible component, movable platform, flexible component, fixed platform pass through actuating mechanism and drive in order and connect.
Preferably, the fixed platform comprises a first supporting section connected with a first platform section, the movable platform comprises a second supporting section connected with a second platform section, and the first supporting section is hinged with the second supporting section; the driving mechanism comprises a driving piece, a first flexible rope and a second flexible rope, the second platform section is connected with the displacement part of the flexible member through the second flexible rope, one end of the first flexible rope is connected with the fixing part of the flexible member, and the other end of the first flexible rope penetrates through the first platform section and then is connected with the driving piece.
Preferably, the fixed platform and the movable platform are connected through a hinged supporting mechanism; the driving mechanism comprises a first pulley connected to the end part of the fixed platform, a second pulley connected to the end part of the movable platform and a driving piece, wherein the second pulley is in transmission connection with the displacement part of the flexible member, and the fixing part, the first pulley and the driving piece of the flexible member are in transmission connection in sequence.
Preferably, the flexible member comprises a connecting seat, a plurality of positive rigidity units and negative rigidity units, wherein the positive rigidity units and the negative rigidity units are connected with the connecting seat, a connecting piece is connected to the negative rigidity units, and the connecting piece is connected with the movable platform through a driving mechanism; the connecting seat is connected with the fixed platform through a driving mechanism.
The invention also provides a rigidity changing method of the rigidity changing device, the driving mechanism comprises a driving piece, a first flexible rope and a second flexible rope, and the rigidity changing method comprises the following steps:
s1, connecting two ends of the movable platform with displacement parts of flexible members through the second flexible ropes, and sequentially connecting fixed parts of the flexible members, two ends of the fixed platform and the driving piece through the first flexible ropes;
s2, the driving piece outputs power and pulls the first flexible rope and the second flexible rope to enable the displacement part of the flexible member to generate relative displacement relative to the fixed part, so that rigidity change of the flexible member is achieved;
wherein, step S2 includes the following steps:
s21, rigidity adjustment: the driving piece is controlled to output the same power to the flexible components positioned at two sides of the joint support, so that the relative position between the movable platform and the fixed platform is kept unchanged;
s22, regulating and controlling rigidity of a first level: the joint support is kept in a fixed position, the driving piece is dynamically adjusted, and the rigidity change adjustment of the flexible component under the fixed position is realized;
s23, regulating and controlling rigidity of a second level: the driving piece is dynamically adjusted, and the driving piece outputs different power to the flexible components positioned on two sides of the joint support, so that the movable platform rotates clockwise or anticlockwise around the fixed platform, and the change of the pose of the joint support is realized.
The invention also provides a rigidity model modeling method of the rigidity variable device, wherein the driving mechanism positioned at the first side of the joint support forms a first driving part, and the driving mechanism positioned at the second side of the joint support forms a second driving part; the verification method comprises the following steps:
s1, performing geometric analysis on the joint support to obtain relative position coordinates among the fixed platform, the movable platform, the first driving part and the second driving part;
s2, respectively obtaining the expressions of the pose and the activity length of the first driving part and the second driving part according to the relative position coordinates and the rotation angle relation between the relative position coordinates and the fixed platform and the movable platform;
s3, constructing a structural matrix according to the rotation of the fixed platform and the movable platform, the first driving pose, the second driving pose and the activity length expression;
s4, carrying out balance statics solving on the structural matrix to obtain a rigidity model.
Further, in step S1, the method specifically includes the following steps:
s11, marking point positions: taking midpoints of the fixed platform and the movable platform to be respectively marked as S, M; the first and second driving parts are respectively denoted as L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the The crossing points of the first and second driving parts and the fixed platform are respectively marked as S 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the The connection points of the first and second driving parts and the movable platform are respectively marked as M 1 、M 2 The method comprises the steps of carrying out a first treatment on the surface of the The movable platform rotates anticlockwise or clockwise relative to the fixed platform in a vertical plane, wherein the rotation center is marked as O, and the rotation angle is marked as theta e The method comprises the steps of carrying out a first treatment on the surface of the The length of the fixed platform is set to be 2q, and the distance from the fixed platform to the O point of the rotation center is set to be h 2 The method comprises the steps of carrying out a first treatment on the surface of the The length of the movable platform is set to be 2p, and the distance from the movable platform to the O point of the rotation center is set to be h 1 ；
S12, establishing a coordinate system: setting a movable platform coordinate system M-xyz by taking an M point as a coordinate origin, and setting a fixed platform coordinate system S-xyz by taking an S point as a coordinate origin;
s13, obtaining corresponding coordinates according to the positions of the point positions in the coordinate system: the coordinates of the rotation center O point are (0, 0); s is S 1 The coordinates of the points are (-q, -h) 2 )，S 2 The coordinates of the points are (q, -h 2 )；M 1 The coordinates of the points are (-p, h) 1 )，M 2 The coordinates of the points are (p, h 1 )。
Further, in step S2, the expression of the pose and the activity length of the first driving portion is:
wherein, I 1 Representing the pose of the first driving part s 1 Representing OS 1 Vector, m of 1 Representation OM 1 Is used, R represents the rotation matrix,
represents M 1 Coordinates of points in the moving platform coordinate system m-xyz, ||l 1 The first driving part is provided with a first driving part;
the expression of the pose and the activity length of the second driving part is as follows:
wherein, I 2 Representing the pose of the second driving part s 2 Representing OS 2 Vector, m of 2 Representation OM 2 Is used, R represents the rotation matrix,
represents M 2 Coordinates of points in the moving platform coordinate system m-xyz, ||l 2 The i represents an active length of the second driving part;
wherein, the rotation matrix R is:
the method comprises the following steps of:
further, in step S3, the structural matrix is denoted as a:
A＝[a 1 a 2 ] T
a 1 ＝OM 1 ×e 1
a 2 ＝OM 2 ×e 2
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Structure vector e of (2) 1 Representation l 1 Unit vector of e 2 Representation l 2 Is a unit vector of (a);
by substitution, it is possible to obtain:
further, in step S4, the relation between the joint stiffness, the external force, and the displacement is:
wherein K represents joint rigidity, W represents external force, and X represents displacement;
the balance statics formula of the joint support is as follows:
W＝[a 1 a 2 ][t 1 t 2 ] T
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Is t 1 Representation l 1 Force on t 2 Representation l 2 Force on;
the rigidity of the first driving part and the second driving part is as follows:
wherein F represents a stiffness characteristic of the flexible member, and d represents a displacement amount of the flexible member in a vertical direction;
neglecting the value of l 1 ，l 2 Stiffness due to tension variation can be obtained:
the stiffness model K is obtained by overlapping the formulas:
compared with the prior art, the invention has the beneficial effects that:
the invention provides a rigidity-changing device, a rigidity-changing method thereof and a modeling method of a rigidity model.
Drawings
FIG. 1 is a schematic view of an embodiment 1 of a stiffness varying apparatus according to the present invention;
FIG. 2 is a schematic structural view of the flexible member of the present invention;
FIG. 3 is a schematic view of an embodiment 2 of a stiffness varying apparatus according to the present invention;
FIG. 4 is a flow chart of a method of varying stiffness of a variable stiffness device of the present invention;
FIG. 5 is a flow chart of a method for modeling a stiffness model of a variable stiffness device of the present invention;
FIG. 6 is a schematic diagram of a method for modeling stiffness model of a variable stiffness device according to the present invention in step S1;
fig. 7 is a schematic representation of a tandem BVSA image of a joint according to the present invention.
The graphic indicia are illustrated as follows:
1-a fixed platform, 11-a first platform section, 111-a first through hole, 12-a first supporting section, 2-a movable platform, 21-a second platform section, 211-a connecting piece, 22-a second supporting section, 3-a flexible member, 31-a connecting seat, 32-a positive stiffness unit, 33-a negative stiffness unit, 34-connecting piece, 4-actuating mechanism, 41-first pulley, 42-second pulley, 43-actuating piece, 44-first flexible rope, 45-second flexible rope, 46-winding wheel, 5-articulated supporting mechanism, 51-first bracing piece subassembly, 52-second bracing piece subassembly, 6-hinge.
Detailed Description
The invention is further described below in connection with the following detailed description. Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to be limiting of the present patent; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
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, it should be understood that, if there is an azimuth or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc., based on the azimuth or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not indicated or implied that the apparatus or element referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus terms describing the positional relationship in the drawings are merely illustrative and should not be construed as limitations of the present patent, and specific meanings of the terms described above may be understood by those skilled in the art according to specific circumstances.
Example 1
Referring to fig. 1 and 2, a first embodiment of a stiffness variable device of the present invention includes a fixed platform 1 and a movable platform 2, wherein the fixed platform 1 and the movable platform 2 are rotationally connected to form an articulated bracket, two sides of the articulated bracket are respectively provided with a flexible member 3, and the movable platform 2, the flexible member 3 and the fixed platform 1 are sequentially connected in a transmission manner through a driving mechanism 4. In this embodiment, the fixed platform 1, the movable platform 2 and the driving mechanism 4 form a redundant degree of freedom platform.
As shown in fig. 1, the fixed platform 1 comprises a first platform section 11 and a first support section 12 connected with the first platform section 11, the movable platform 2 comprises a second platform section 21 and a second support section 22 connected with the second platform section 21, and the first support section 12 is hinged with the second support section 22. Specifically, the first platform section 11 and the first support section 12 form a first T-shaped structure, the second platform section 21 and the second support section 22 form a second T-shaped structure, and one end of the first support section 12 far away from the first platform section 11 is connected with one end of the second support section 22 far away from the second platform section 21 through a hinge 6.
As shown in fig. 1, the driving mechanism 4 includes a driving element 43, a first flexible rope 44, and a second flexible rope 45, the second platform section 21 is connected to the displacement portion of the flexible member 3 through the second flexible rope 45, one end of the first flexible rope 44 is connected to the fixing portion of the flexible member 3, and the other end passes through the first platform section 11 and is connected to the driving element 43. In this embodiment, the driving mechanism 4 further includes a winding wheel 46, where the winding wheel 46 is connected to the driving end of the driving element 43, one end of the first flexible rope 44 is connected to the fixing portion of the flexible member 3, and the other end passes through the first platform section 11 and is connected to the winding wheel 46.
Specifically, the driving member 43 is a motor, and the first flexible rope 44 and the second flexible rope 45 are kevlar ropes.
Also, the first platform section 11 is provided at both ends with a first through hole 111 for the first flexible rope 44 to pass through, and the second platform section 21 is provided at both ends with a connecting piece 211 for connecting the second flexible rope 45. One end of the first flexible rope 44 is connected with the fixed part of the flexible member 3, and the other end passes through the first through hole 111 and then is connected with the driving piece 43; one end of the second flexible rope 45 is connected to the displacement portion of the flexible member 3, and the other end is connected to the second platform section 21 via the connector 211. In this embodiment, the connecting piece 211 includes a second through hole formed on the movable platform 2, and further includes a countersunk nut formed at the second through hole, and the second flexible rope 45 extends into the second through hole and is connected with the countersunk nut. In order to improve the winding effect of the winding wheel 46, the winding wheel 46 is located at a position directly below the first through hole 111.
As shown in fig. 2, the fixing portion of the flexible member 3 includes two connection seats 31, the displacement portion of the flexible member 3 is provided with a plurality of groups, each group of displacement portion includes a positive stiffness unit 32 and a negative stiffness unit 33, the positive stiffness unit 32 and the negative stiffness unit 33 are both located between the two connection seats 31, two ends of the positive stiffness unit 32 are respectively connected with the two connection seats 31, and two ends of the negative stiffness unit 33 are also respectively connected with the two connection seats 31; the positive stiffness unit 32 is positioned right above the negative stiffness unit 33, the middle part of the positive stiffness unit 32 is provided with an opening structure, the negative stiffness unit 33 is connected with a connecting piece 34, and the negative stiffness units 33 between two adjacent groups in the displacement part are connected through the connecting piece 34; the connecting piece 34 passes through the opening structure and then is connected with the movable platform 2 through the driving mechanism 4; the connecting seat 31 is connected with the fixed platform 1 through the driving mechanism 4. In this embodiment, the connecting piece 34 is a connecting strip, one end of the second flexible rope 45 is connected with the connecting piece 34, and the other end is connected with the movable platform 2; one end of the first flexible rope 44 is connected with the bottoms of the two connecting seats 31, and the other end passes through the fixed platform 1 and then is connected with the driving mechanism 4.
Example 2
The embodiment is similar to embodiment 1, except that, as shown in fig. 3, the fixed platform 1 and the movable platform 2 are connected by a hinge support mechanism 5; the driving mechanism 4 comprises a first pulley 41 connected to the end part of the fixed platform 1, a second pulley 42 connected to the end part of the movable platform 2, a driving piece 43, a first flexible rope 44 and a second flexible rope 45, wherein the second pulley 42 is connected with the displacement part of the flexible member 3 through the second flexible rope 45, one end of the first flexible rope 44 is connected with the fixed part of the flexible member 3, and the other end of the first flexible rope 44 bypasses the first pulley 41 and is connected with the driving piece 43.
The hinged support mechanism 5 includes a first support rod assembly 51 and a second support rod assembly 52, which are arranged in a crossing manner, wherein two ends of the first support rod assembly 51 are hinged with the fixed platform 1 and the movable platform 2 respectively, and two ends of the second support rod assembly 52 are hinged with the fixed platform 1 and the movable platform 2 respectively. As shown in fig. 3, the first support rod assembly 51 includes at least two first support rods parallel to each other, and the second support rod assembly 52 includes at least two second support rods parallel to each other, and both the first support rods are located between the two second support rods, so that stability of the hinge support mechanism 5 can be improved.
In addition, the driving mechanism 4 in the embodiment further comprises a winding wheel 46, the driving piece 43 is a motor, the winding wheel 46 is connected with an output shaft of the motor, and a motor base of the motor is connected with the bottom of the fixed platform 1; one end of the first flexible rope 44 is connected to the fixed portion of the flexible member 3, and the other end is connected to the take-up pulley 46 after passing around the first pulley 41.
Example 3
Referring to fig. 4, an embodiment of a stiffness varying method of a stiffness varying device according to the present invention is shown, wherein the driving mechanism 4 includes a driving member 43, a first flexible rope 44, and a second flexible rope 45, and the stiffness varying method includes the following steps:
s1, connecting two ends of a movable platform 2 with displacement parts of a flexible member 3 through a second flexible rope 45, and sequentially connecting fixed parts of the flexible member 3, two ends of a fixed platform 1 and a driving piece 43 through a first flexible rope 44;
s2, the driving piece 43 outputs power and pulls the first flexible rope 44 and the second flexible rope 45 to enable the displacement part of the flexible member 3 to generate relative displacement relative to the fixed part, so that the rigidity change of the flexible member 3 is realized;
wherein, step S2 includes the following steps:
s21, rigidity adjustment: the control driving piece 43 outputs the same power to the flexible components 3 positioned at the two sides of the joint bracket, so that the relative position between the movable platform 2 and the fixed platform 1 is kept unchanged;
s22, regulating and controlling rigidity of a first level: the joint support is kept in a fixed position, the power output quantity of the driving piece 43 is dynamically adjusted, and the rigidity change adjustment of the flexible component 3 in the fixed position is realized;
s23, regulating and controlling rigidity of a second level: the power output quantity of the driving piece 43 is dynamically regulated, and the driving piece 43 outputs different powers to the flexible components 3 positioned at the two sides of the joint support, so that the movable platform 2 rotates clockwise or anticlockwise around the fixed platform 1, and the change of the pose of the joint support is realized.
Example 4
Fig. 5 to 7 show an embodiment of a stiffness modeling method of a stiffness variable device according to the present invention, wherein a first flexible rope 44 and a second flexible rope 45 located on the left side of an articular bracket form a first driving portion, and a first flexible rope 44 and a second flexible rope 45 located on the right side of the articular bracket form a second driving portion; the verification method comprises the following steps:
s1, performing geometric analysis on the joint support to obtain relative position coordinates among the fixed platform 1, the movable platform 2, the first driving part and the second driving part.
In step S1, the method specifically includes the following steps:
s11, marking point positions: the midpoints of the fixed platform 1 and the movable platform 2 are respectively marked as S, M; the first and second driving parts are respectively denoted as L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the The intersection points of the first and second driving parts and the fixed platform 1 are respectively denoted as S 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the First and secondThe connection points of the driving part and the movable platform 2 are respectively marked as M 1 、M 2 The method comprises the steps of carrying out a first treatment on the surface of the The movable platform 2 rotates anticlockwise or clockwise relative to the fixed platform 1 in a vertical plane, wherein the rotation center is marked as O, and the rotation angle is marked as theta e The method comprises the steps of carrying out a first treatment on the surface of the Setting the length of the platform 1 to be 2q, and setting the distance from the platform 1 to the rotation center O point to be h 2 The method comprises the steps of carrying out a first treatment on the surface of the Let the length of the movable platform 2 be 2p, and the distance from the movable platform 2 to the rotation center O point be h 1 The method comprises the steps of carrying out a first treatment on the surface of the As shown in fig. 6;
s12, establishing a coordinate system: setting a movable platform coordinate system M-xyz by taking an M point as a coordinate origin, and setting a fixed platform coordinate system S-xyz by taking an S point as a coordinate origin;
s13, obtaining corresponding coordinates according to the positions of the points in the coordinate system: the coordinates of the rotation center O point are (0, 0); s is S 1 The coordinates of the points are (-q, -h) 2 )，S 2 The coordinates of the points are (q, -h 2 )；M 1 The coordinates of the points are (-p, h) 1 )，M 2 The coordinates of the points are (p, h 1 )。
S2, according to the relative position coordinates and the rotation angle relation between the relative position coordinates and the fixed platform 1 and the movable platform 2, the positions and the movement length expressions of the first driving part and the second driving part are obtained respectively.
In step S2, the expression of the pose and the activity length of the first driving portion is:
wherein, I 1 Representing the pose of the first driving part s 1 Representing OS 1 Vector, m of 1 Representation OM 1 Is used, R represents the rotation matrix,
represents M 1 Coordinates of points in a moving platform coordinate system m-xyz, ||l 1 I represents the first driveThe movable length of the movable part;
the expression of the pose and the activity length of the second driving part is as follows:
wherein, I 2 Representing the pose of the second driving part s 2 Representing OS 2 Vector, m of 2 Representation OM 2 Is used, R represents the rotation matrix,
represents M 2 Coordinates of points in a moving platform coordinate system m-xyz, ||l 2 The i represents the active length of the second driving part;
wherein, the rotation matrix R is:
the method comprises the following steps of:
s3, constructing a structural matrix according to the rotation of the fixed platform 1 and the movable platform 2, the first driving pose, the second driving pose and the activity length expression.
In step S3, the structural matrix is denoted as a:
A＝[a 1 a 2 ] T
a 1 ＝OM 1 ×e 1
a 2 ＝OM 2 ×e 2
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Structure vector e of (2) 1 Representation l 1 Unit vector of e 2 Representation l 2 Is a unit vector of (a);
by substitution, it is possible to obtain:
s4, carrying out balance statics solving on the structural matrix to obtain a rigidity model.
In step S4, the relation between the joint stiffness, the external force and the displacement is:
wherein K represents joint rigidity, W represents external force, and x represents displacement;
the balance statics formula of the joint support is:
W＝[a 1 a 2 ][t 1 t 2 ] T
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Is t 1 Representation l 1 Force on t 2 Representation l 2 Force on;
the rigidity of the first driving part and the second driving part is as follows:
wherein F represents the rigidity characteristic of the flexible member 3, and d represents the displacement amount of the flexible member 3 in the vertical direction; note that, according to the principle of stiffness superposition, the stiffness characteristic of the flexible member 3 has the following expression:
F＝F p +F n
wherein F is p Representing the positive stiffness characteristic of the positive stiffness unit 32, F n Representing the negative stiffness characteristic of the negative stiffness unit 33;
since the change in stiffness due to the tension change in the flexible cord is very small, the change in stiffness due to the tension change in the flexible cord can be ignored 1 ，l 2 Stiffness caused by tension change can be obtained:
the stiffness model K can be obtained by superimposing the formulas in step S4 as follows:
it should be noted that, the image drawn according to the function of the stiffness model K may be analogous to the joint serial BVSA image, as shown in fig. 7, in which the ordinate represents stiffness and the abscissa represents the rotation angle of the joint support, so that it can be confirmed that the stiffness varying device has stiffness varying capability.
During simulation, the rigidity and the pose of the flexible rope-driven humanoid arm are cooperatively controlled by the torque output by the motor, the output torque is transmitted to the flexible rope through the winding wheel 46, the flexible rope drives the displacement part of the flexible member 3 to deform in the vertical direction, and tension change generated by the displacement of the displacement part of the flexible member 3 relative to the fixed part is the rigidity characteristic of the variable-rigidity device for driving the humanoid arm by the flexible rope. The rigidity characteristic is characterized by the relation between the tension of the flexible rope driving movable platform 2 and the displacement of the displacement part, and the relation between the muscle strength and the muscle length of human skeletal muscles is similar to that of human skeletal muscles. The length, width and height of the positive and negative rigidity units of the flexible member 3 as well as the inclination angle with the horizontal plane and the number of unit layers can be flexibly adjusted according to the environment so as to realize different rigidity characteristics.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (7)
1. The rigidity-changing device is characterized by comprising a fixed platform (1) and a movable platform (2), wherein the fixed platform (1) is rotationally connected with the movable platform (2) to form an articulated bracket, flexible components (3) are arranged on two sides of the articulated bracket, and the movable platform (2), the flexible components (3) and the fixed platform (1) are sequentially in transmission connection through a driving mechanism (4); the flexible member (3) comprises a connecting seat (31), a plurality of positive rigidity units (32) and negative rigidity units (33), wherein the positive rigidity units (32) and the negative rigidity units (33) are connected with the connecting seat (31), a connecting piece (34) is connected to the negative rigidity units (33), and the connecting piece (34) is connected with the movable platform (2) through a driving mechanism (4); the connecting seat (31) is connected with the fixed platform (1) through the driving mechanism (4); wherein:
the fixed platform (1) comprises a first platform section (11) and a first supporting section (12) connected with the first platform section (11), the movable platform (2) comprises a second supporting section (22) connected with a second platform section (21), and the first supporting section (12) is hinged with the second supporting section (22); the driving mechanism (4) comprises a driving piece (43), a first flexible rope (44) and a second flexible rope (45), the second platform section (21) is connected with the displacement part of the flexible member (3) through the second flexible rope (45), one end of the first flexible rope (44) is connected with the fixed part of the flexible member (3), and the other end of the first flexible rope passes through the first platform section (11) and is connected with the driving piece (43);
or the fixed platform (1) and the movable platform (2) are connected through a hinged supporting mechanism (5); the driving mechanism (4) comprises a first pulley (41) connected to the end part of the fixed platform (1), a second pulley (42) connected to the end part of the movable platform (2) and a driving piece (43), the second pulley (42) is in transmission connection with the displacement part of the flexible member (3), and the fixed part, the first pulley (41) and the driving piece (43) of the flexible member (3) are in sequential transmission connection.
2. A method of varying stiffness applied to the varying stiffness device of claim 1, wherein the driving mechanism (4) comprises a driving member (43), a first flexible cord (44), a second flexible cord (45), the method comprising the steps of:
s1, connecting two ends of the movable platform (2) with displacement parts of a flexible member (3) through the second flexible rope (45), and sequentially connecting fixed parts of the flexible member (3), two ends of the fixed platform (1) and the driving piece (43) through the first flexible rope (44);
s2, the driving piece (43) outputs power and pulls the first flexible rope (44) and the second flexible rope (45) to enable the displacement part of the flexible member (3) to generate relative displacement relative to the fixed part, so that the rigidity change of the flexible member (3) is realized;
wherein, step S2 includes the following steps:
s21, rigidity adjustment: the driving piece (43) is controlled to output the same power to the flexible components (3) positioned at the two sides of the joint support, so that the relative position between the movable platform (2) and the fixed platform (1) is kept unchanged;
s22, regulating and controlling rigidity of a first level: the joint support is kept in a fixed position, the driving piece (43) is dynamically adjusted, and the rigidity change adjustment of the flexible component (3) under the fixed position is realized;
s23, regulating and controlling rigidity of a second level: the driving piece (43) is dynamically adjusted, and the driving piece (43) outputs different power to the flexible components (3) positioned on two sides of the joint support, so that the movable platform (2) rotates clockwise or anticlockwise around the fixed platform (1) to change the pose of the joint support.
3. A method for modeling a stiffness model applied to the variable stiffness device according to claim 1, wherein a driving mechanism (4) located on a first side of the joint support forms a first driving part, and a driving mechanism (4) located on a second side of the joint support forms a second driving part; the verification method comprises the following steps:
s1, performing geometric analysis on the joint support to obtain relative position coordinates among the fixed platform (1), the movable platform (2), the first driving part and the second driving part;
s2, respectively obtaining the expressions of the pose and the activity length of the first driving part and the second driving part according to the relative position coordinates and the rotation angle relation between the relative position coordinates and the fixed platform (1) and the movable platform (2);
s3, constructing a structural matrix according to the rotation of the fixed platform (1) and the movable platform (2), the first driving pose, the second driving pose and the activity length expression;
s4, carrying out balance statics solving on the structural matrix to obtain a rigidity model.
4. A method of modeling a stiffness model of a variable stiffness device according to claim 3, comprising the steps of, in step S1:
s11, marking point positions: taking midpoints of the fixed platform (1) and the movable platform (2) to be respectively marked as S, M; the first and second driving parts are respectively denoted as L 1 、L 2 The method comprises the steps of carrying out a first treatment on the surface of the The crossing points of the first and second driving parts and the fixed platform (1) are respectively marked as S 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the The connection points of the first and second driving parts and the movable platform (2) are respectively marked as M 1 、M 2 The method comprises the steps of carrying out a first treatment on the surface of the The movable platform (2) rotates anticlockwise or clockwise relative to the fixed platform (1) in a vertical plane, wherein the rotation center is marked as O, and the rotation angle is marked as theta e The method comprises the steps of carrying out a first treatment on the surface of the The length of the fixed platform (1) is 2, and the distance from the fixed platform (1) to the rotation center O point is h 2 The method comprises the steps of carrying out a first treatment on the surface of the The length of the movable platform (2) is 2, and the distance from the movable platform (2) to the rotation center O point is h 1 ；
S12, establishing a coordinate system: setting a movable platform coordinate system M-xyz by taking an M point as a coordinate origin, and setting a fixed platform coordinate system S-xyz by taking an S point as a coordinate origin;
s13, obtaining corresponding coordinates according to the positions of the point positions in the coordinate system: the coordinates of the rotation center O point are (0, 0); s is S 1 The coordinates of the points are (-q, -h) 2 )， 2 The coordinates of the points are (q, -h 2 )；M 1 The coordinates of the points are (-p, h) 1 )， 2 The coordinates of the points are (p, h 1 )。
5. The method of modeling a stiffness model of a variable stiffness device according to claim 4, wherein in step S2, the expression of the pose and the activity length of the first driving portion is:
wherein, I 1 Representing the pose of the first driving part s 1 Representing OS 1 Vector, m of 1 Representation OM 1 Is used, R represents the rotation matrix,
represents M 1 Point atThe coordinates of the moving platform coordinate system m-xyz, |l 1 II represents the activity length of the first driving part;
the expression of the pose and the activity length of the second driving part is as follows:
wherein, I 2 Representing the pose of the second driving part s 2 Representing OS 2 Vector, m of 2 Representation OM 2 Is used, R represents the rotation matrix,
represents M 2 The coordinates of the point in the moving platform coordinate system m-xyz, |l 2 II represents the activity length of the second driving part;
wherein, the rotation matrix R is:
the method comprises the following steps of:
6. the method of modeling a stiffness model of a variable stiffness device of claim 5, wherein in step S3, the structural matrix is denoted as a:
A＝[a 1 a 2 ] T
a 1 ＝M 1 ×e 1
a 2 ＝M 2 ×e 2
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Structure vector e of (2) 1 Representation l 1 Unit vector of e 2 Representation l 2 Is a unit vector of (a);
by substitution, it is possible to obtain:
7. the method of modeling a stiffness model of a variable stiffness device according to claim 6, wherein in step S4, a relation between the joint stiffness and the external force, displacement is:
wherein K represents joint rigidity, W represents external force, and x represents displacement;
the balance statics formula of the joint support is as follows:
W＝[a 1 a 2 ][t 1 t 2 ] T
wherein a is 1 Representation l 1 A) of the structure vector of (a) 2 Representation l 2 Is used for the structure vector of (a), 1 representation l 1 Force on t 2 Representation l 2 Force on;
the rigidity of the first driving part and the second driving part is as follows:
wherein F represents the rigidity characteristic of the flexible member (3), and d represents the displacement amount of the flexible member (3) in the vertical direction;
neglecting the value of l 1 ，l 2 Stiffness due to tension variation can be obtained:
the stiffness model K is obtained by overlapping the formulas:
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