CN111890409A

CN111890409A - Multi-degree-of-freedom active and passive variable stiffness flexible joint based on controllable viscosity medium

Info

Publication number: CN111890409A
Application number: CN202010848320.8A
Authority: CN
Inventors: 李满宏; 陈俊杰; 王哲; 张明路; 曹鉴
Original assignee: Hebei University of Technology
Current assignee: Hebei University of Technology
Priority date: 2020-08-21
Filing date: 2020-08-21
Publication date: 2020-11-06

Abstract

The invention relates to a multi-degree-of-freedom active and passive variable-stiffness flexible joint based on a controllable viscosity medium, which comprises an active and passive variable-stiffness adjusting mechanism, a joint multi-degree-of-freedom adjusting mechanism and an input shell structure, wherein the active and passive variable-stiffness adjusting mechanism and the joint multi-degree-of-freedom adjusting mechanism are both arranged in the input shell structure; the active and passive variable stiffness adjusting mechanism comprises a reducer output disc, an external excitation generator and an output disc adapter; the joint multi-degree-of-freedom adjusting mechanism comprises an air pressure telescopic cylinder, a connecting hinge, a connecting flange, a speed reducer and a motor; the joint has a rotational degree of freedom in the circumferential direction under the action of the motor, and has a spherical rotational degree of freedom under the synergistic action of the four air pressure telescopic cylinders. The joint realizes variable rigidity in the circumferential direction through a controllable viscosity medium, and realizes variable rigidity in the direction of the spherical rotational freedom degree through the combined action of four pneumatic telescopic cylinders.

Description

Multi-degree-of-freedom active and passive variable stiffness flexible joint based on controllable viscosity medium

Technical Field

The invention relates to the field of intelligent robots, in particular to a multi-degree-of-freedom active and passive variable stiffness flexible joint based on a controllable viscosity medium.

Background

The joint is used as a connecting part of the robot and is the key for guaranteeing the environmental adaptability and the gait mobility of the robot. The joint of the traditional robot is usually connected with two movable parts in a rigid connection mode, namely, the two movable parts are connected in a hard connection mode, the connection mode is suitable for controlling joint driving under a simple mechanical structure, but the rigid connection easily causes vibration transmission of the movable parts of the robot, so that the control precision of robot movement is influenced, parts are damaged when the control precision is serious, and the working stability and the service life of the robot are further influenced. In particular, the rigid contact between the foot end of the legged robot and the ground can cause a great loss of energy, and the utilization rate of the energy is also reduced. In addition, the joint adopting the hard connection mode cannot dynamically adjust the rigidity of the joint according to the external environment and the change of the self load of the robot, cannot meet the requirement of dynamic adjustment of the rigidity of the joint in the motion process of the robot under a complex and changeable environment, and easily generates time-varying rigidity impact, thereby causing the damage of the root nature of the robot. Therefore, flexible joints with variable stiffness characteristics have been a hot spot in the field of robotic research.

At present, scholars at home and abroad carry out extensive and intensive research on variable-stiffness robot joints and research and develop various typical joints. According to the patent document 'a variable-rigidity flexible joint device (CN 109227596A)', the variable-rigidity flexible joint device is provided, joint rigidity adjustment is realized by actively adjusting the relative position of a roller frame and a leaf spring, and the relative position of the roller frame and the leaf spring is adjusted by adopting the structure of a lead screw slider, so that the structure is relatively complex, and meanwhile, the high-precision joint movement positioning is difficult to carry out due to the influence of the arrangement form of positioning parts, and the requirement of high-precision joint movement control is met. Patent document "spatially controllable time varying stiffness flexible joint device (CN 109483590A)" discloses a spatially controllable time varying stiffness flexible joint device, which utilizes the engagement of a driven gear and an end curved surface gear to compress a spring to realize varying stiffness; the joint device can only realize one degree of freedom of rotation, and the meshing position of the gears has abrasion and gaps, so that the rigidity is difficult to realize accurate adjustment. Patent document "a variable stiffness joint (CN109877874A) based on a symmetric slider-crank mechanism" realizes joint stiffness adjustment by actively driving a slider-crank mechanism with a stiffness adjustment motor, and although the joint has a simple structure and can realize a wide-range stiffness adjustment, the stiffness adjustment method has high requirements on the structural strength and the adjustment torque of a joint stiffness adjustment structure, and it is difficult to realize effective adjustment of joint passive stiffness.

In summary, although the existing flexible joint can primarily realize the adjustment of the joint stiffness, the joint motion and stiffness control freedom degree is single, the active and passive stiffness adjustment modes are complex, the motion positioning and stiffness adjustment precision is poor, the frequency response characteristic is poor, the structure control is complex and other outstanding problems generally exist. Therefore, it is necessary to design a flexible joint having multiple degrees of freedom, capable of passively and adaptively responding to external rigid impacts and also capable of actively adjusting rigidity.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to solve the technical problem of providing a multi-degree-of-freedom active and passive variable stiffness flexible joint based on a controllable viscosity medium; the joint has a spherical rotational degree of freedom and a rotational degree of freedom in the circumferential direction of the joint, can realize active and passive adjustment of rigidity of the joint in any motion direction, and can passively adapt to external rigid impact in all directions.

In order to solve the technical problems, the invention adopts the technical scheme that:

a multi-degree-of-freedom active and passive variable-stiffness flexible joint based on a controllable viscosity medium comprises an active and passive variable-stiffness adjusting mechanism, a joint multi-degree-of-freedom adjusting mechanism and an input shell structure, wherein the active and passive variable-stiffness adjusting mechanism and the joint multi-degree-of-freedom adjusting mechanism are both arranged in the input shell structure; it is characterized in that the preparation method is characterized in that,

the active and passive variable stiffness adjusting mechanism comprises a reducer output disc, an external excitation generator and an output disc adapter; the joint multi-degree-of-freedom adjusting mechanism comprises an air pressure telescopic cylinder, a connecting hinge, a connecting flange, a speed reducer and a motor;

the motor is arranged on the connecting flange, an output shaft of the motor penetrates through the connecting flange to be connected with an input end of the speed reducer, and an output end of the speed reducer is fixedly connected with an output disc of the speed reducer; one end of the output disc adapter is rotatably arranged in the input shell structure, the output disc of the speed reducer is rotatably arranged in the output disc adapter, and the joint has a rotational degree of freedom in the circumferential direction under the action of the motor; a closed cavity is formed between the output disc of the speed reducer and the output disc jointer at the same time, and the closed cavity is filled with a controllable viscosity medium; the external excitation generator is positioned in the closed cavity and provides excitation with different strengths for the controllable viscosity medium, so that the variable stiffness of the joint in the circumferential direction is realized;

the connecting flange is uniformly provided with four air pressure telescopic cylinders on the circumference through connecting hinges, the cylinder barrel of each air pressure telescopic cylinder is hinged with the upper end of the corresponding connecting hinge to form a revolute pair, and the rotary axes of the revolute pairs formed by all the air pressure telescopic cylinders and the corresponding connecting hinges are perpendicular to the radial direction of the connecting flange; the piston rods of the pneumatic telescopic cylinders are fixedly connected with the upper part of the input shell structure; the lower end of the connecting hinge and the connecting flange form a moving pair in the radial direction of a joint, and a rotating pair taking the radial direction of the connecting flange as a rotating shaft is formed between the two moving pairs; under the synergistic effect of the four air pressure telescopic cylinders, the joint has a spherical surface rotation freedom degree.

The joint also comprises an encoder and a grating ruler; two ends of the encoder are fixedly connected with an output disc of the speed reducer and an output disc connector respectively; each pneumatic telescopic cylinder is provided with a grating ruler.

The input shell structure comprises a retainer end cover, a guide end cover and an input shell; the retainer end cover and the guide end cover are both hemispherical shells with one open end; the input shell is a cylindrical thin-wall structure with openings at the upper end and the lower end, and end cover connecting flanges are respectively arranged at the openings at the upper end and the lower end; an end cover connecting flange at the upper end of the input shell is fixedly connected with the end cover of the retainer, and an end cover connecting flange at the lower end of the input shell is fixedly connected with the guide end cover; the input shell is provided with a gap in the circumferential direction, and a connecting flange plate extends in the circumferential direction opposite to the gap.

The output disc adaptor is a cylindrical structure with an opening at the upper part, and an output flange extends out of the circumference of the cylindrical structure; a cylinder is arranged at the center of the cylindrical structure; the bottom of the barrel-shaped structure is provided with an annular arc surface in the circumferential direction.

The curvature of the annular cambered surface is the same as that of the inner surface of the shell of the guide end cover.

An annular cover extends from the edge of the bottom of the output disc of the speed reducer along the axial direction, a shaft shoulder is arranged at the lower part of the outer wall of the annular cover, and a groove is formed in the lower end face of the annular cover; the center of the bottom of the output disc of the speed reducer is provided with a circular truncated cone, and the upper part of the outer wall of the circular truncated cone is provided with a groove.

The output disc of the speed reducer is rotatably arranged in the cylindrical structure of the output disc jointer, the circular table of the output disc of the speed reducer is inserted into the cylinder of the output disc jointer, and the lower end surface of the circular table is not contacted with the upper surface of the cylinder; a closed cavity is formed between the annular cover of the output disc of the speed reducer and the cylinder of the output disc jointer, and the closed cavity is filled with a controllable viscosity medium.

The upper end of the connecting hinge is provided with a hinge hole, and the lower end of the connecting hinge is provided with a shaft hole; the connecting flange is uniformly provided with four cylindrical guide rails along the radial direction of the connecting flange in a circumferential direction on the upper end surface, and each cylindrical guide rail is matched with a shaft hole at the lower end of the connecting hinge to form a moving pair along the radial direction of the joint and a rotating pair taking the axis of the shaft hole of the connecting hinge as a rotating shaft; the hinge hole at the upper end of each connecting hinge is hinged with the cylinder barrel of the respective air pressure telescopic cylinder to form a rotating pair, and the rotating axes of the rotating pairs formed by all the connecting hinges and the air pressure telescopic cylinders are perpendicular to the radial direction of the connecting flange.

The process of passively changing rigidity of the joint comprises the following steps: when the joint is subjected to rigid impact, the output disc of the speed reducer and the output disc jointer rotate relatively, a controllable viscosity medium in a closed space formed by the output disc of the speed reducer and the output disc jointer generates damping force between the output disc of the speed reducer and the output disc jointer, and the rigidity of the joint in the circumferential direction is passively changed when the output disc of the speed reducer and the output disc jointer move relatively; meanwhile, the rigid impact can compress the gas in each air pressure telescopic cylinder, and the compressed air pressure telescopic cylinder generates damping force, so that the passive rigidity change of the joint in the spherical surface rotation direction is realized.

The process of actively changing the rigidity of the joint comprises the following steps: when the original rigidity of the joint cannot meet the working requirement, the excitation strength generated by an external excitation generator is adjusted to enable the viscous force of the controllable viscosity medium to reach a preset value, so that the damping force between an output disc and an output disc jointer of the speed reducer reaches a preset value, and the rigidity of the joint in the circumferential direction is actively changed; meanwhile, the damping force of a piston rod of the air pressure telescopic cylinder is changed by adjusting the air pressure of the air pressure telescopic cylinder, and the active rigidity change of the joint in the spherical rotation direction is realized.

Compared with the prior art, the invention has the beneficial effects that:

1. the flexible joint can realize the instant regulation of the joint rigidity by dynamically regulating and controlling the viscosity coefficient of a controllable viscosity medium, and has extremely high frequency response characteristics: a closed cavity is formed between an annular cover of the output disc of the speed reducer and a cylinder of the output disc jointer, controllable viscosity media (such as electrorheological fluid) are filled in the closed cavity, and the controllable viscosity media have different viscous forces under different external excitation strengths (such as electric field strength) to generate corresponding damping force to influence the relative rotation between the output disc of the speed reducer and the output disc jointer, so that the rigidity of a joint in the circumferential direction is influenced. According to the requirement of dynamic adjustment of the rigidity, the viscous force of the controllable viscosity medium can be changed by changing the external excitation strength in a very short time, and further the instant adjustment of the rigidity of the joint is realized.

2. The flexible joint provided by the invention has multiple degrees of freedom, can realize motion in any direction, and can be passively self-adapted to external rigid impact: the connecting flange is provided with four air pressure telescopic cylinders which are uniformly distributed in the circumferential direction, the axes of the air pressure telescopic cylinders are parallel to the axis of the joint, a cylinder barrel of the air pressure telescopic cylinder is matched with the connecting flange to form movable connection, the tail end of a piston rod of the air pressure telescopic cylinder is fixed with the end cover of the retainer, the bottom of the output disc connector is provided with a cambered surface ring, the cambered surface ring is matched with the inner surface of the guide end cover to form a moving pair, and the contraction or stretching (different stretching amounts) of the four air pressure telescopic cylinders is controlled, so that the joint has a spherical surface rotation degree of; in addition, a motor is fixed on the connecting flange, and an output shaft of the motor can transmit power to the output disc jointer through a speed reducer so as to realize that the output disc jointer rotates around a joint axis to realize controllable movement of one degree of freedom in the circumferential direction of the joint; this rotational movement will produce two direct effects: 1) when the output disc jointer is subjected to external rigid impact and generates angular displacement around a joint shaft, namely when the output disc jointer generates passive rigidity change in the circumferential direction, the output disc jointer cannot rebound to a position before the rigid impact, and the angular displacement of the output disc jointer caused by the external rigid impact can be actively compensated by using the rotation motion of the motor, so that the output disc jointer is prevented from moving and impacting an input shell of the joint under continuous rigid impact; 2) when the joint drives the mechanical arm to move, the mechanical arm can perform rotary motion at a certain angle in the circumferential direction of the joint by the power output by the motor, so that the main rotation of the joint is realized; when the joint is subjected to rigid impact, the output disc adapter overcomes part of damping force generated by viscous force of the controllable viscosity medium so as to generate rotary motion around the axis of the joint to generate angular displacement to adapt to the rigid impact; meanwhile, when the joint is subjected to rigid impact, the pneumatic telescopic cylinder is compressed to enable the output disc adapter to do spherical motion around the spherical center of the guide end cover, so that passive self-adaptation in the direction of the spherical rotational freedom degree of the joint is met, and the joint can be passively self-adapted to the rigid impact in any direction through the matching of a rotating pair formed by the output disc of the speed reducer and the output disc adapter and the four pneumatic telescopic cylinders.

3. The flexible joint has the capability of multi-degree-of-freedom accurate positioning, and can realize high-precision motion control in any direction: the output disc jointer and the output disc of the speed reducer are connected through the encoder, the angular displacement of rotary motion between the output disc jointer and the output disc of the speed reducer can be accurately detected by the encoder, and the angular displacement of the output disc of the speed reducer is accurately controlled by matching with a motor, so that the tail end of the output disc jointer can be accurately positioned around an axis; the pneumatic telescopic cylinders are provided with the grating rulers, the grating rulers can detect the telescopic amount of the pneumatic telescopic cylinders in real time during working, and the telescopic amount of each pneumatic telescopic cylinder uniquely determines the position of the tail end of the output disc jointer in space, so that the deflection angle generated when the tail end of the output disc jointer performs spherical motion can be accurately solved through the telescopic amounts of the four pneumatic telescopic cylinders, and the accurate measurement and control of the displacement of the joint in the spherical rotation direction are realized through the cooperation of the encoder, the motor and the grating rulers.

4. The flexible joint of the invention can realize the dynamic and accurate adjustment of the joint rigidity: according to the invention, the viscosity coefficient between the controllable viscosity media in the closed cavity is accurately controlled by accurately adjusting the external excitation strength, so that the damping force between the output disc jointer and the output disc of the speed reducer is changed, and the accurate adjustment of the joint rigidity in the circumferential direction for actively changing the rigidity is realized; when the joint is subjected to rigid impact in the circumferential direction, relative displacement is generated between the output disc of the speed reducer and the output disc jointer, and damping force can be generated between the output disc of the speed reducer and the output disc jointer by the viscous force of the controllable viscosity medium in the closed cavity, so that the accurate adjustment of the passive variable stiffness in the circumferential direction of the joint is realized; the pressure of each air pressure telescopic cylinder can be adjusted by inflating or deflating the four air pressure telescopic cylinders, and the pressure in the air pressure telescopic cylinders can be accurately controlled to change the mechanical characteristics of two ends of the air pressure telescopic cylinders, so that the accurate adjustment of the active variable stiffness of the joint in the direction of the spherical surface rotational freedom degree is realized; when the joint is subjected to rigid impact, the four air pressure telescopic cylinders are compressed under stress, so that the connecting flange can do spherical motion around a spherical center on the guide end cover, and damping force is generated between the connecting flange and the end cover of the retainer, thereby realizing the accurate adjustment of the joint in the axial direction by changing the rigidity passively; in conclusion, the cooperative coupling dynamic accurate adjustment performance of the rigidity of the joint in any direction can be realized through the combined action of the controllable viscosity medium and the air pressure telescopic cylinder.

5. The variable-rigidity flexible joint has the advantages of simple and compact structure, convenience in installation and strong universality: the active and passive variable stiffness adjusting mechanism adopts the controllable viscosity medium to actively and passively adjust the stiffness of the joint in the circumferential direction, and adopts the variable stiffness mode of the controllable viscosity medium to replace the variable stiffness mechanism of the traditional complex mechanical structure, so that the joint structure is simple and compact and is easy to miniaturize; the four air pressure telescopic cylinders can realize the spherical rotation of the joint and the active and passive rigidity change in the spherical rotation direction, so that the joint structure is more compact; the flanges on the input shell and the output disc jointer can adopt universal connecting flanges, are conveniently connected with the mechanical arm, and are convenient to install and high in universality.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is an axial cross-sectional view of the overall structure of the present invention;

FIG. 3 is a schematic structural diagram of an active and passive variable stiffness adjustment mechanism and a joint multiple degree of freedom adjustment mechanism of the present invention at one viewing angle;

FIG. 4 is a schematic structural diagram of an active and passive variable stiffness adjustment mechanism and a joint multiple degree of freedom adjustment mechanism of the present invention at another viewing angle;

FIG. 5 is an exploded view of the active and passive stiffness-varying adjustment mechanism of the present invention from one perspective;

FIG. 6 is an exploded view of the active and passive variable stiffness adjustment mechanism of the present invention from another perspective;

FIG. 7 is an exploded view of the joint multiple degree of freedom adjustment mechanism and the cage end cap of the present invention;

FIG. 8 is a schematic structural view of a coupling flange of the present invention;

FIG. 9 is a schematic structural diagram of an input housing of the present invention;

in the figure: 1, an active and passive variable stiffness adjusting mechanism, 2, a joint multi-degree-of-freedom adjusting mechanism and 3, an input shell structure;

101 reducer output disc, 102 clamp spring, 103 thin-wall bearing, 104 small sealing ring, 105 controllable viscosity medium, 106 encoder, 107 large sealing ring, 108 excitation generator, 109 flat key, 110 output disc connector, 201 pipe clamp, 202 air pressure telescopic cylinder, 203 connecting hinge, 204 connecting flange, 205 reducer, 206 motor, 207 grating ruler, 301 retainer end cover, 302 guiding end cover, 303 input shell;

101-1 annular cover, 101-2 round table, 110-1 cylinder, 110-2 annular arc surface, 110-3 output flange, 110-4 cylinder structure, 204-1 cylindrical guide rail, 204-2 countersunk through hole, 301-1 end cover connecting seat, 303-1 connecting flange plate and 303-2 end cover connecting flange.

Detailed Description

The embodiments of the present invention are given below with reference to the specific drawings, and the specific embodiments are only used for further explaining the present invention in detail, and do not limit the protection scope of the present application.

The invention relates to a multi-degree-of-freedom active and passive variable stiffness flexible joint (a joint for short, see figures 1-9) based on a controllable viscosity medium, which comprises an active and passive variable stiffness adjusting mechanism 1, a joint multi-degree-of-freedom adjusting mechanism 2 and an input shell structure 3, wherein the active and passive variable stiffness adjusting mechanism 1 and the joint multi-degree-of-freedom adjusting mechanism 2 are both arranged in the input shell structure 3; the active and passive variable stiffness adjusting mechanism 1 comprises a reducer output disc 101, an excitation generator 108 and an output disc adapter 110; the joint multiple freedom degree adjusting mechanism 2 comprises an air pressure telescopic cylinder 202, a connecting hinge 203, a connecting flange 204, a speed reducer 205 and a motor 206;

one end of the output disc adaptor 110 is rotatably arranged in the input shell structure 3, and the reducer output disc 101 is rotatably arranged in the output disc adaptor 110, so that the joint has one degree of freedom of rotation in the circumferential direction; a closed cavity is formed between the reducer output disc 101 and the output disc adapter 110 at the same time, and the closed cavity is filled with a controllable viscosity medium 105; the excitation generator 108 is positioned in the closed cavity and provides excitation with different strengths for the controllable viscosity medium 105 so as to change the viscous force of the controllable viscosity medium 105 and further change the damping force between the output disc 101 and the output disc jointer 110 of the speed reducer, thereby realizing variable rigidity of the joint in the circumferential direction;

the motor 206 is fixed on the connecting flange 204, an output shaft of the motor 206 passes through the connecting flange 204 to be connected with an input end of the speed reducer 205, and an output end of the speed reducer 205 is fixedly connected with the upper end of the output disc 101 of the speed reducer; the connecting flange 204 is uniformly provided with four air pressure telescopic cylinders 202 in a circumference manner through connecting hinges 203, the cylinder barrel of each air pressure telescopic cylinder 202 is hinged with the upper end of the respective connecting hinge 203 to form a revolute pair, and the revolute axes of the revolute pairs formed by all the air pressure telescopic cylinders 202 and the respective connecting hinges 203 are vertical to the radial direction of the connecting flange 204; a piston rod of the pneumatic telescopic cylinder 202 is fixedly connected with the upper part of the input shell structure 3; the lower end of the connecting hinge 203 and the connecting flange 204 form a moving pair in the radial direction of the joint, and the moving pair and the connecting flange 204 can form a rotating pair taking the radial direction of the connecting flange 204 as a rotating shaft; under the synergistic action of the four air compression cylinders 202, the structures except the input shell 3, the connecting hinge 203 and the air compression cylinders 202 perform spherical motion by taking a point on a joint axis as a spherical center to generate deflection of a certain angle, so that the joint has a spherical rotation degree of freedom.

The joint further comprises an encoder 106 and a grating ruler 207; two ends of the encoder 106 are respectively connected with the reducer output disc 101 and the output disc jointer 110, and the encoder is used for detecting the relative rotational displacement between the output disc jointer 110 and the reducer output disc 101; each pneumatic telescopic cylinder 202 is provided with a grating ruler 207 for detecting the displacement generated in the axial direction of the pneumatic telescopic cylinder 202 during the rotation of the connecting flange 204.

The working principle and the working process of the invention are as follows:

the present invention can be used as a joint for a robot, connecting the middle of the input housing structure 3 to one arm of a robot arm, and one end of the output disk engager 110 to the other arm of the robot arm. Before the joint starts to work, proper pressure needs to be preset in the air pressure telescopic cylinder 202 to ensure that the joint has certain rigidity in the degree of freedom of spherical motion and the bottom annular cambered surface 110-2 of the output disc adapter 110 is tightly matched with the inner surface of the guide end cover 302; meanwhile, the air inflation or deflation of the air compression cylinders 202 can enable each air compression cylinder 202 to extend or contract, and the expansion amount of the four air compression cylinders 202 is adjusted, so that the connecting flange 204 can deflect around the spherical center on the guide end cover 302 to a certain degree, and the joint has a spherical surface rotation degree of freedom; meanwhile, in the radial direction of the joint, the power output by the motor 206 is transmitted to the output disc 101 and the output disc adapter 110 of the speed reducer through the speed reducer 205, so that the output disc adapter 110 performs rotary motion around the axis of the joint, and the joint has one degree of freedom of rotation around the axis of the joint in the circumferential direction; under the combined action of the motor 206 and all the air pressure telescopic cylinders 202, the joint can realize the coupling motion of the spherical rotation freedom degree and the circumferential rotation freedom degree, thereby realizing the controllable motion of the joint in any direction.

In the process of movement and work of the joint, rigid impact is easily generated at the position connected with the mechanical arm to cause impact vibration of the joint, the impact vibration can enable the output disc jointer 110 to generate relative rotary angular displacement relative to the output disc 101 of the speed reducer, in the process, the viscous force of the controllable viscosity medium 105 in the closed cavity between the output disc jointer 110 and the output disc 101 of the speed reducer can generate damping force between the output disc jointer 110 and the output disc 101 of the speed reducer, and the damping force can change the mechanical property of displacement between the output disc jointer 110 and the output disc 101 of the speed reducer, so that the circumferential passive variable stiffness of the joint is realized, and the circumferential rigid impact of the; in the joint axial direction, the impact vibration can cause the gas in each pneumatic telescopic cylinder 202 to be compressed, so that the connecting flange 204 can rotate around the spherical center of the guide end cover 302 in a spherical manner, the compressed pneumatic telescopic cylinder 202 generates damping force to realize the passive rigidity change of the joint in the spherical rotation direction, and the rigid impact of the joint is effectively avoided.

When the original rigidity characteristic of the joint cannot meet the working requirement of the joint in a complex environment, the original rigidity of the joint needs to be changed at any time to adapt to the work in the complex environment, and at the moment, the excitation strength generated by the excitation generator 108 is accurately adjusted, so that the viscous force of the controllable viscosity medium 105 reaches a preset value, the damping force between the output disc 101 and the output disc jointer 110 of the speed reducer reaches a preset value, and the rigidity of the joint in the circumferential direction can be actively and accurately adjusted; meanwhile, the gas pressure in the air pressure telescopic cylinder 202 is accurately adjusted by controlling the charging and discharging of the air pressure telescopic cylinder 202, so that the damping force of the piston rod of the air pressure telescopic cylinder 202 is changed, and the active rigidity change of the joint in the spherical rotation direction is realized.

According to the control requirement of the dynamic motion of the joint, the four air pressure telescopic cylinders 202 and the motor 206 can be simultaneously and cooperatively controlled to realize the coupling motion of the joint in any direction, the excitation strength of the excitation generator 108 can be changed at any time to change the viscous force of the controllable viscosity medium 105 in the continuous coupling motion process of the joint, and the pressure of the air pressure telescopic cylinders 202 is changed, so that the active accurate rigidity changing capability of the joint in the circumferential direction and the axial direction is realized immediately, and in the active rigidity changing process, the joint always has the spherical surface rotation freedom degree and the passive rigidity changing capability in the circumferential direction.

The grating ruler 207 on each air pressure telescopic cylinder 202 can detect the displacement of the air pressure telescopic cylinder 202 in the radial direction of the joint in real time, in the active motion process of the joint, the grating ruler 207 can detect the displacement of the air pressure telescopic cylinder 202 in the active motion in real time, the pose of the connecting flange 204 in the space can be accurately known through calculation of the displacements of the four air pressure telescopic cylinders 202, and then the pose of the tail end of the output disc connector 110 can be accurately mastered through mathematical calculation, so that accurate positioning in the motion process of the joint is realized, and the joint load motion can be accurately achieved to a preset value; when the joint is subjected to circumferential rigid impact, the output disc 101 of the speed reducer performs passive rotation, the encoder 106 detects the generated angular displacement in real time, the angular displacement of the passive rotation detected by the encoder 106 and the active rotation displacement controlled by the motor 206 are superposed, and the angular displacement of the rotation of the tail end of the output disc jointer 110 can be accurately measured; through the cooperation measurement of the encoder 106 and the grating ruler 207, the position of the tail end of the output disc jointer 110 in the motion process can be accurately positioned, so that the multi-degree-of-freedom accurate coupling motion of the joint is realized.

Examples

The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium comprises an active and passive variable stiffness adjusting mechanism 1, a joint multi-degree-of-freedom adjusting mechanism 2 and an input shell structure 3; the active and passive variable stiffness adjusting mechanism 1 comprises a reducer output disc 101, an encoder 106, an excitation generator 108 and an output disc adapter 110; the joint multiple-degree-of-freedom adjusting mechanism 2 comprises an air pressure telescopic cylinder 202, a connecting hinge 203, a connecting flange 204, a speed reducer 205, a motor 206 and a grating ruler 207; the input shell structure 3 comprises a retainer end cover 301, a guide end cover 302 and an input shell 303;

the output disc adaptor 110 is a cylindrical structure 110-4 with an opening at the upper part, an output flange 110-3 extends out of the circumference of the cylindrical structure 110-4, a circle of through holes which are uniformly distributed and used for connecting the arm body of the mechanical arm are formed in the output flange 110-3, and the output flange 110-3 is used as the output end of the whole joint; a cylinder 110-1 is arranged at the center of the cylindrical structure 110-4, and the output disc adapter 110 is provided with a circle of threaded holes which are uniformly arranged and used for connecting the encoder 106 in the area of the cylinder 110-1; the bottom of the barrel-shaped structure 110-4 is provided with an annular arc surface 110-2 matched with the guide end cover 302, and the middle part of the inner wall of the barrel-shaped structure 110-4 is provided with a groove for mounting the clamp spring 102;

an annular cover 101-1 extends from the edge of the bottom of the output disc 101 of the speed reducer along the axial direction, the lower part of the outer wall of the annular cover 101-1 is provided with a shaft shoulder, and the lower end face of the annular cover 101-1 is provided with a groove for mounting a large sealing ring 107; a circular truncated cone 101-2 is arranged at the center of the bottom of the output disc 101 of the speed reducer, and a groove for mounting a small sealing ring 104 is formed in the upper part of the outer wall of the circular truncated cone 101-2; the output disc 101 of the speed reducer is rotatably installed in a cylindrical structure 110-4 of an output disc jointer 110 through a thin-wall bearing 103, a circular truncated cone 101-2 of the output disc 101 of the speed reducer is inserted into a cylinder 110-1 of the output disc jointer 110, the lower end face of the circular truncated cone 101-2 is not in contact with the upper surface of the cylinder 110-1, and a space for installing an encoder 106 is reserved; the inner ring of the thin-wall bearing 103 is axially limited by a shaft shoulder on the outer wall of the annular cover 101-1, the outer ring of the thin-wall bearing 103 is limited by a clamp spring 102, and the clamp spring 102 is embedded and fixed in a groove of the output disc adapter 110; a closed cavity is formed between the annular cover 101-1 of the output disc 101 of the speed reducer and the cylinder 110-1 of the output disc adapter 110, and two ends of the closed cavity are sealed through a small sealing ring 104 and a large sealing ring 107; the closed cavity is filled with a controllable viscosity medium 105, the controllable viscosity medium 105 is a solid-liquid mixing system with viscosity force remarkably changed under the action of external excitation intensity change, and is used for generating damping force between the output disc jointer 110 and the reducer output disc 101 so as to adjust the rigidity of the joint in the circumferential direction; the excitation generator 108 is positioned in the closed cavity and comprises an excitation generating end and an excitation receiving end, the excitation generating end and the excitation receiving end are fixedly connected with the output disc 101 and the output disc jointer 110 of the speed reducer respectively, an electric field or a magnetic field is formed in the closed cavity, and the viscosity force of the controllable viscosity medium 105 is changed by changing the strength of the electric field or the magnetic field; the encoder 106 is positioned in a cylinder 110-1 of the output disc adapter 110, a flange at the bottom of the encoder 106 is fixedly connected with a threaded hole in the cylinder 110-1 of the output disc adapter 110 through a screw, a rotating shaft of the encoder 106 is matched with a circular table 101-2 of the output disc 101 of the speed reducer through a flat key 109, and the encoder 106 is used for detecting the relative angular displacement during the relative rotation between the output disc adapter 110 and the output disc 101 of the speed reducer.

The small sealing ring 104 and the large sealing ring 107 are circular rings with rectangular radial sections, the small sealing ring 104 is arranged in a groove of a circular table 101-2 of the reducer output disc 101, and the large sealing ring 107 is arranged in a groove of the annular cover 101-1, so that a gap is prevented from being generated between contact surfaces of the reducer output disc 101 and the output disc connector 110, and the sealing of a closed cavity is realized.

The upper end of the connecting hinge 203 is provided with a hinge hole, and the lower end is provided with a shaft hole;

the connecting flange 204 is uniformly provided with four cylindrical guide rails 204-1 along the radial direction of the connecting flange 204 in the circumferential direction of the upper end surface, a central hole is formed in the central position, and a circle of countersunk through holes 204-2 connected with a motor 206 are formed in the circumferential direction; the cylindrical guide rails 204-1 are L-shaped, the short end of each cylindrical guide rail 204-1 is fixedly connected with the upper end face of the connecting flange 204, and the long end of each guide rail 204-1 is matched with the shaft hole at the lower end of the connecting hinge 203 to form a moving pair along the radial direction of the joint and a rotating pair taking the axis of the shaft hole of the connecting hinge 203 as a rotating shaft; a hinge hole at the upper end of each connecting hinge 203 is hinged with the cylinder barrel of the corresponding air pressure telescopic cylinder 202 through a rivet to form a rotating pair, and the rotating axes of the rotating pairs formed by the connecting hinges 203 and the air pressure telescopic cylinders 202 are all vertical to the axis of the cylindrical guide rail 204-1; the four air pressure telescopic cylinders 202 cooperate to enable the connecting flange 204 to perform spherical motion around the spherical center on the guide end cover 302, so that the joint has a spherical rotational degree of freedom; the upper end of a piston rod of the air compression and expansion cylinder 202 is fixedly connected with an end cover connecting seat 301-1 on a retainer end cover 301, and the axes of all the air compression and expansion cylinders 202 are always parallel to the axis of a joint in the initial position (before the joint does not work); the speed reducer 205 is a harmonic speed reducer, the motor 206 is fixed at the center of the connecting flange 204, and an output shaft of the motor 206 passes through a central hole of the connecting flange 204 and is connected with a flexible gear of the speed reducer 205; a rigid wheel of the speed reducer 205 is fixedly connected with the upper end of the output disc 101 of the speed reducer;

a rod of each pneumatic telescopic cylinder 202 is provided with a grating ruler 207 through the pipe clamp 201, and the grating ruler is used for detecting the displacement of the pneumatic telescopic cylinder 202 in the axial direction during the rotation of the connecting flange 204.

The holder end cover 301 and the guide end cover 302 are both hemispherical shells with one open end, a circular boss is arranged in the middle of the interior of the holder end cover 301, and four end cover connecting seats 301-1 which are uniformly arranged in a circumferential manner are arranged on the circular boss; the end cover connecting seat 301-1 is composed of two rectangular lifting lugs, and the two rectangular lifting lugs of each hinge 301-1 are fixedly connected with the upper end of the piston rod of the respective air pressure telescopic cylinder 202.

The curvature of the inner surface of the shell of the guide end cover 302 is the same as that of the annular cambered surface 110-2 at the bottom of the output disc adapter 110, so that the output disc adapter 110 and the guide end cover 302 can be matched without clearance to form a rotating pair.

The input shell 303 is a cylindrical thin-wall structure with openings at the upper end and the lower end, and end cover connecting flanges 303-2 are respectively arranged at the openings at the upper end and the lower end; an end cover connecting flange 303-2 at the upper end of the input shell 303 is fixedly connected with the retainer end cover 301, and an end cover connecting flange 303-2 at the lower end of the input shell 303 is fixedly connected with the guide end cover 302; the input housing 303 is circumferentially notched such that the output flange 110-1 of the output disc engager 110 extends from the notch; a connecting flange plate 303-1 extends out of the middle of the input shell 303 in the circumferential direction, the end of the connecting flange plate 303-1 is semicircular and used for being connected with the arm body of the mechanical arm, and the connecting flange plate 303-1 serves as an input end of a joint.

Nothing in this specification is said to apply to the prior art.

Claims

1. A multi-degree-of-freedom active and passive variable-stiffness flexible joint based on a controllable viscosity medium comprises an active and passive variable-stiffness adjusting mechanism, a joint multi-degree-of-freedom adjusting mechanism and an input shell structure, wherein the active and passive variable-stiffness adjusting mechanism and the joint multi-degree-of-freedom adjusting mechanism are both arranged in the input shell structure; it is characterized in that the preparation method is characterized in that,

2. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium as claimed in claim 1, wherein the joint further comprises an encoder and a grating ruler; two ends of the encoder are fixedly connected with an output disc of the speed reducer and an output disc connector respectively; each pneumatic telescopic cylinder is provided with a grating ruler.

3. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on a controllable viscosity medium as claimed in claim 1, wherein the input shell structure comprises a retainer end cap, a guide end cap and an input shell; the retainer end cover and the guide end cover are both hemispherical shells with one open end; the input shell is a cylindrical thin-wall structure with openings at the upper end and the lower end, and end cover connecting flanges are respectively arranged at the openings at the upper end and the lower end; an end cover connecting flange at the upper end of the input shell is fixedly connected with the end cover of the retainer, and an end cover connecting flange at the lower end of the input shell is fixedly connected with the guide end cover; the input shell is provided with a gap in the circumferential direction, and a connecting flange plate extends in the circumferential direction opposite to the gap.

4. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium as claimed in claim 3, wherein the output disc adapter is a cylindrical structure with an opening at the upper part, and an output flange extends out of the circumference of the cylindrical structure; a cylinder is arranged at the center of the cylindrical structure; the bottom of the barrel-shaped structure is provided with an annular arc surface in the circumferential direction.

5. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on a controllable viscosity medium as claimed in claim 4, wherein the curvature of the annular arc surface is the same as the curvature of the inner surface of the shell of the guide end cover.

6. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium is characterized in that an annular cover axially extends from the bottom edge of the output disc of the speed reducer, a shaft shoulder is arranged at the lower part of the outer wall of the annular cover, and a groove is formed in the lower end face of the annular cover; the center of the bottom of the output disc of the speed reducer is provided with a circular truncated cone, and the upper part of the outer wall of the circular truncated cone is provided with a groove.

7. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium is characterized in that the reducer output disc is rotatably installed in a cylindrical structure of an output disc jointer, a circular truncated cone of the reducer output disc is inserted into a cylinder of the output disc jointer, and the lower end face of the circular truncated cone is not in contact with the upper surface of the cylinder; a closed cavity is formed between the annular cover of the output disc of the speed reducer and the cylinder of the output disc jointer, and the closed cavity is filled with a controllable viscosity medium.

8. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium as claimed in claim 1, wherein the upper end of the connecting hinge is provided with a hinge hole, and the lower end of the connecting hinge is provided with a shaft hole; the connecting flange is uniformly provided with four cylindrical guide rails along the radial direction of the connecting flange in a circumferential direction on the upper end surface, and each cylindrical guide rail is matched with a shaft hole at the lower end of the connecting hinge to form a moving pair along the radial direction of the joint and a rotating pair taking the axis of the shaft hole of the connecting hinge as a rotating shaft; the hinge hole at the upper end of each connecting hinge is hinged with the cylinder barrel of the respective air pressure telescopic cylinder to form a rotating pair, and the rotating axes of the rotating pairs formed by all the connecting hinges and the air pressure telescopic cylinders are perpendicular to the radial direction of the connecting flange.

9. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium as claimed in claim 1, wherein the process of the joint passive variable stiffness is as follows:

when the joint is subjected to rigid impact, the output disc of the speed reducer and the output disc jointer rotate relatively, a controllable viscosity medium in a closed space formed by the output disc of the speed reducer and the output disc jointer generates damping force between the output disc of the speed reducer and the output disc jointer, and the rigidity of the joint in the circumferential direction is passively changed when the output disc of the speed reducer and the output disc jointer move relatively; meanwhile, the rigid impact can compress the gas in each air pressure telescopic cylinder, and the compressed air pressure telescopic cylinder generates damping force, so that the passive rigidity change of the joint in the spherical surface rotation direction is realized.

10. The multi-degree-of-freedom active and passive variable stiffness flexible joint based on the controllable viscosity medium as claimed in claim 1, wherein the process of the active variable stiffness of the joint is as follows:

when the original rigidity of the joint cannot meet the working requirement, the excitation strength generated by an external excitation generator is adjusted to enable the viscous force of the controllable viscosity medium to reach a preset value, so that the damping force between an output disc and an output disc jointer of the speed reducer reaches a preset value, and the rigidity of the joint in the circumferential direction is actively changed; meanwhile, the damping force of a piston rod of the air pressure telescopic cylinder is changed by adjusting the air pressure of the air pressure telescopic cylinder, and the active rigidity change of the joint in the spherical rotation direction is realized.