CN113618774A

CN113618774A - Variable-stiffness transmission joint based on cam mechanism and switching control method

Info

Publication number: CN113618774A
Application number: CN202110815119.4A
Authority: CN
Inventors: 鞠锦勇; 黄少奇; 张春蕊; 刘玉飞; 訾斌; 苏学满; 汤东; 陈剑波; 聂洋
Original assignee: Anhui Polytechnic University
Current assignee: Anhui Polytechnic University
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2021-11-09
Anticipated expiration: 2041-07-19
Also published as: CN113618774B

Abstract

The invention relates to the technical field of variable-stiffness transmission of robots, in particular to a variable-stiffness transmission joint based on a cam mechanism and a switching control method, wherein the variable-stiffness transmission joint comprises a transmission module and a variable-stiffness module, and the transmission module comprises: the rear shaft I is provided with a cavity and internally provided with a large electromagnet, a large spring, a variable stiffness motor and a speed reducer which are sequentially connected; the front shaft I is provided with a cavity and is fixedly connected with the rear shaft I; the shaft II is arranged in the cavity of the front shaft I and rotates relative to the front shaft I; the torsion bar is arranged in the cavity of the front shaft I, and two ends of the torsion bar are connected with the rear shaft I and the shaft II; the variable stiffness module includes: a cylindrical cam mechanism; a movable platform; a guide rail mechanism. The variable-stiffness transmission joint based on the cam mechanism is compact in structure and light in weight; the locking of the position of the push rod positioning piece and the position of the movable platform can be realized, the switching between the transmission function and the rigidity changing function is realized, and the device has the advantages of simplicity in control and high rigidity retentivity.

Description

Variable-stiffness transmission joint based on cam mechanism and switching control method

Technical Field

The invention relates to the technical field of variable-stiffness transmission of robots, in particular to a variable-stiffness transmission joint based on a cam mechanism and a switching control method.

Background

In the fields of robots, vehicle transmission and the like, a transmission joint is used as an important component of power transmission and plays an important role in the kinematic characteristics and the dynamic characteristics of a mechanism. In order to ensure the accuracy of an output position, the traditional transmission joint pursues high rigidity of the transmission joint or keeps the rigidity constant, but the traditional transmission joint has poor adaptability and weak man-machine interaction capability. In recent years, in order to improve the man-machine interaction capability of a transmission joint in the field of robots and the load adaptability of the transmission joint under different working conditions, the variable-stiffness rotary joint has gained more and more attention.

The variable-stiffness joint has flexible and various structural forms and mainly comprises basic types such as an antagonistic type, a pre-tightening type, a spring sheet type and a variable transmission ratio type. The variable-rigidity joints are driven by a specific mechanical structure through a motor matched with a speed reducer, so that the state of a variable-rigidity element is changed, and the aim of adjusting the rigidity of the joints is fulfilled. For example, chinese patent CN201510715690.3 discloses a variable-stiffness elastic joint of cam structure, in which a spring plate is a variable-stiffness element, one end of the spring plate is fixedly connected with a shaft, and the other end of the spring plate is fixedly connected with an outer ring, and the position of a sliding block on the spring plate is changed by the rotation of a cam plate, so as to change the effective deformation length of the spring plate, thereby achieving the purpose of changing the stiffness of the output joint. The structure can only fix the position of the sliding block by locking the cam disc, thereby realizing output rigidity maintenance, but under the action of external force, the cam roller on the sliding block and the cam disc are easy to relatively move, so the rigidity maintenance of the mechanism is poor, and effective control is difficult to realize in specific application; for another example, chinese patent CN201810733720.7 discloses a variable stiffness joint based on a cam mechanism, in which a locking motor is used to fix the position of a joint input rotating shaft, so as to maintain output stiffness, but also under the action of an external force, a circular arc cam and the joint input rotating shaft may rotate relatively, resulting in poor stiffness maintenance performance of the solution. Therefore, in the design process, in order to fully utilize the advantages of the variable stiffness joint, the problem of stiffness retentivity of the variable stiffness joint in the actual application process is fully considered, and the control is convenient.

Disclosure of Invention

In order to solve the technical problem, the invention provides a variable-stiffness transmission joint based on a cam mechanism and a switching control method. The rigidity-variable joint aims to solve the problems that the rigidity retentivity of the rigidity-variable joint is poor and the control difficulty is high in the prior art. According to the invention, the push rod positioning piece and the locking mechanism of the movable platform are integrated through the guide rail mechanism, the rigidity changing function and the transmission function of the variable-rigidity transmission joint are switched by utilizing electric control, and the rigidity retentivity of the variable-rigidity transmission joint is effectively ensured.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

a variable-rigidity transmission joint based on a cam mechanism comprises a transmission module and a variable-rigidity module, wherein the transmission module comprises:

the rear shaft I is provided with a cavity and internally provided with a large electromagnet, a large spring, a variable stiffness motor and a speed reducer which are sequentially connected;

the front shaft I is provided with a cavity and is fixedly connected with the rear shaft I;

the shaft II is arranged in the cavity of the front shaft I and rotates relative to the front shaft I;

the torsion bar is arranged in the cavity of the front shaft I, and two ends of the torsion bar are connected with the rear shaft I and the shaft II, so that power is transmitted from the rear shaft I to the shaft II;

the variable stiffness module includes:

the cylindrical cam mechanism is arranged in the cavity of the front shaft I through a bearing and is connected with the speed reducer;

the movable platform is arranged in the cavity of the front shaft I, sleeved on the torsion bar and connected with the cylindrical cam mechanism;

and the guide rail mechanism is in interference fit with the front shaft I and is coaxial with the rear shaft I, and is respectively matched with the cylindrical cam mechanism and the movable platform.

Preferably, the cylindrical cam mechanism comprises a cylindrical cam installed in a cavity of the front shaft I through a bearing, a push rod positioning piece matched with the guide rail mechanism, a roller arranged on the contour line of the cylindrical cam, a push rod penetrating through the push rod positioning piece and having two ends correspondingly connected to the roller and the movable platform, and an external gear connected with the speed reducer.

Preferably, the cylindrical cam is of a cavity structure, and an inner gear in meshed connection with the outer gear is arranged on the end face of the cylindrical cam.

Preferably, the guide rail mechanism comprises a guide rail with a guide groove, a movable rack I and a movable rack II which are assembled in the guide rail guide groove, a small electromagnet I and a small electromagnet II which are arranged on the bottom surface of the guide rail guide groove, a small spring I and a small spring II, wherein the small electromagnet I and the small spring I are connected with the movable rack I, the small electromagnet II and the small spring II are connected with the movable rack II, the movable rack I is matched with a push rod positioning piece, and the movable rack II is matched with a movable platform.

Preferably, the push rod positioning piece is provided with a fixing block matched with the movable rack I, and the fixing block is provided with a Hall proximity switch sensor.

Preferably, be equipped with on the portable rack I with fixed block complex recess, the bottom of recess is equipped with the permanent magnet.

Preferably, the movable platform is provided with a circumferential guide rail connected with one end of the push rod, a toothed block matched with the movable rack II and a laser displacement sensor.

Preferably, a tooth-shaped groove matched with the tooth-shaped block is formed in the movable rack II.

The switching control method is based on a switching control system, the switching control system comprises a variable stiffness transmission joint based on a cam mechanism, a signal acquisition card for acquiring data of a laser displacement sensor and a Hall proximity switch sensor, a motor driver for controlling the movement of a variable stiffness motor, a relay I for correspondingly controlling the loss of power of a large electromagnet, a small electromagnet I and a small electromagnet II, a relay III, and a controller connected with the signal acquisition card, the motor driver, the relay I, the relay II and the relay III, and the switching control method specifically comprises the following steps:

(A) setting a zero point position: the permanent magnet at the bottom of the groove in the movable rack I is sensed through a Hall proximity switch sensor, and a signal is sent out to determine the zero point position;

(B) determining the target effective deformation length of the torsion bar according to the rigidity value required in the transmission process of the variable-rigidity transmission joint;

(C) and (3) rigidity adjustment: the controller controls the large electromagnet to lose power, the small electromagnet to lose power and the small electromagnet to gain power through the relay I, the relay II and the relay III, so that the position between the push rod positioning piece and the guide rail is locked, the variable stiffness motor is in power connection with the cylindrical cam, and then the movable platform is driven to axially move along the front shaft I through the cylindrical cam and the push rod, so that the distance between the movable platform and the shaft II is adjusted;

(D) the transmission function is realized: the controller controls the large electromagnet to be powered on, the small electromagnet to be powered on and the small electromagnet to be powered off through the relay I, the relay II and the relay III, so that the push rod positioning piece and the guide rail are separated from locking, the variable stiffness motor is separated from power connection with the cylindrical cam, the movable platform and the guide rail are locked at positions, the rear shaft I and the front shaft I rotate, and the shaft II is driven by the torsion bar to synchronously rotate with the rear shaft I so as to perform torsion transmission;

(E) resetting: detecting whether the push rod positioning piece is located at a zero position, if not, controlling the large electromagnet to lose power by the controller through the relay I, and driving the detection push rod positioning piece to rotate until the push rod positioning piece is located at the zero position after the variable stiffness motor is in power connection with the cylindrical cam; if the push rod is located at the zero position, the controller controls the small electromagnet I to lose power through the relay II, and the position between the push rod positioning piece and the guide rail is locked.

Further, the target effective deformation length of the torsion bar in the step (B) is determined by the following formula:

wherein L represents the effective deformation length of the torsion bar, E represents the elastic modulus of the torsion bar, R represents the rotation radius of the torsion bar, d represents the section diameter of the torsion bar, theta represents the bending angle of the torsion bar, and K represents the variable stiffness transmission joint stiffness value required in the transmission process.

The invention has the beneficial effects that:

compared with the prior art, on one hand, the variable-rigidity transmission joint based on the cam mechanism has the advantages that the cylindrical cam is of a cavity structure, power is transmitted through the internal gear on the inner surface of the cylindrical cam, the torsion bar penetrates through the cylindrical cam, and the two sides of the torsion bar are fixedly connected with the shaft I and the shaft II respectively, so that the structure is compact, and the weight is light; on the other hand, the variable-stiffness transmission joint based on the cam mechanism can realize the locking of the position of the push rod positioning piece and the position of the movable platform by controlling the large electromagnet, the small electromagnet I and the small electromagnet II to lose power, realizes the switching of the transmission function and the variable-stiffness function, and has the advantages of simplicity in control and high stiffness retentivity.

Drawings

The invention is further illustrated with reference to the following figures and examples:

FIG. 1 is a schematic view showing an external structure of a variable stiffness revolute joint according to the present invention;

FIG. 2 is a schematic view of the internal structure of the variable stiffness revolute joint of the present invention;

FIG. 3 is a schematic structural diagram of a transmission module according to the present invention;

FIG. 4 is a schematic view showing the engagement of an external gear with an internal gear at the right end of a cylindrical cam in the present invention;

FIG. 5 is a schematic view of the coupling of the external gear to the output shaft of the reducer in accordance with the present invention;

FIG. 6 is a schematic structural view of a cylindrical cam mechanism according to the present invention;

FIG. 7 is a schematic view of the guide rail mechanism of the present invention in cooperation with the movable platform and the push rod positioning plate;

FIG. 8 is a front view of the guide rail mechanism (not including the guide rail) of the present invention;

FIG. 9 is a rear view of the guide mechanism (not including the guide rail) of the present invention;

FIG. 10 is a control flow block diagram of the present invention;

FIG. 11 is a schematic diagram illustrating determination of zero position in an embodiment of the present invention;

FIG. 12 is a control flow diagram of the stiffness adjustment function in an embodiment of the present invention;

FIG. 13 is a schematic diagram showing the state of the electromagnets and springs in varying stiffness in an embodiment of the present invention;

FIG. 14 is a control flow diagram of the transmission function in an embodiment of the present invention;

fig. 15 is a schematic view of the state of each electromagnet and spring during transmission in the embodiment of the invention.

In the figure: 1. a rear shaft I; 2. a bolt; 3. a gasket; 4. a nut; 5. a front shaft I; 6. an end cap; 7. a screw; 8. a shaft II; 9. a large electromagnet; 10. a large spring; 11. a motor positioning sheet; 12. a bearing; 12-1 and a bearing I; 12-2 and a bearing II; 13. a cylindrical cam; 14. a movable platform; 15. a guide rail; 16. a torsion bar; 17. a push rod positioning sheet; 18. a push rod; 19. a variable stiffness motor; 20. an outer gear; 21. a speed reducer; 22. a set screw; 23. a roller; 24. a small electromagnet I; 25. a small spring I; 26. a small electromagnet II; 27. a small spring II; 28. a movable rack I; 29. a movable rack II; 30. a torsion bar locating plate; 31. positioning pins; 32. a laser displacement sensor; 33. a Hall proximity switch sensor; 34. a signal acquisition card; 35. a controller; 36. a relay I; 37. a relay II; 38. a relay III; 39. a motor driver; 40. a fixed block; 41. a circumferential guide rail; 42. a toothed block; 43. and (4) a groove.

Detailed Description

In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the invention is further explained in the following with the accompanying drawings and the embodiments.

As shown in fig. 1 to 9, the variable stiffness transmission joint based on the cam mechanism comprises a transmission module, a variable stiffness module, a large electromagnet 9, a large spring 10, a variable stiffness motor 19 and a speed reducer 21, wherein the large electromagnet, the large spring 10, the variable stiffness motor 19 and the speed reducer are positioned in the transmission module.

Specifically, as shown in fig. 2 and 3, the transmission module includes a rear axle i 1, a front axle i 5, an end cover 6, an axle ii 8, and a torsion bar 16.

Furthermore, the rear shaft I1 and the front shaft I5 are fixedly connected through four groups of bolts 2, gaskets 3 and nuts 4 which are uniformly distributed in the circumferential direction.

The rear shaft I1 and the front shaft I5 are respectively provided with a cavity, the large electromagnet 9, the large spring 10, the variable stiffness motor 19 and the speed reducer 21 are sequentially connected and are arranged in the cavity of the rear shaft I1, the variable stiffness motor 19, the speed reducer 21 and the integrated structure are arranged, the bottom of the variable stiffness motor 19 is arranged in the cavity of the rear shaft I1 through a motor positioning piece 11, and the motor positioning piece 11 is made of metal materials and is provided with a moving guide groove so as to achieve the purpose of limiting the rotation of the variable stiffness motor 19 and the speed reducer 21.

The end cover 6 is of a hollow structure and is fixedly connected with the front shaft I5 through a screw 7.

The shaft II 8 is internally arranged in a cavity of the front shaft I5, and is matched with the inner wall of the cavity of the front shaft I5 through a bearing I12-1 and a bearing II 12-2, so that the relative rotation with the front shaft I5 is realized.

The torsion bar 16 is arranged in a cavity of the front shaft I5, one end of the torsion bar positioning piece 30 and one end of the positioning pin 31 are connected to the rear shaft I1, and the other end of the torsion bar positioning piece is connected to the shaft II 8, so that power is transmitted to the shaft II 8 from the rear shaft I1 through the torsion bar 16.

Specifically, as shown in fig. 2, the variable stiffness module includes a cylindrical cam mechanism, a movable platform 14, and a guide rail mechanism.

Further, as shown in fig. 6, the cylindrical cam mechanism includes a cylindrical cam 13 with a cavity structure, two rollers 23 mounted on a cam contour of the cylindrical cam 13, push rod positioning pieces 17 concentrically distributed with the cylindrical cam 13, and two push rods 18 distributed side by side and each passing through the push rod positioning piece 17. One end of each push rod 18 is fixedly connected with the corresponding two rollers, and the other end of each push rod is matched and connected with a circumferential guide rail on the movable platform 14 through a spherical hinge. The circumferential rotation of the pushrods 18 on the movable platform 14 is achieved by the spherical hinge cooperating with the circumferential guide. As shown in fig. 2, the cylindrical cam 13 is mounted in a cavity of the front shaft i 5 via a bearing 12. As shown in fig. 4, an internal gear is provided on an end surface of the cylindrical cam 13, and the internal gear is engaged with an external gear 20. As shown in fig. 5, the external gear 20 is fixedly coupled to the output shaft of the reducer by a set screw 22.

As shown in fig. 7, 8 and 9, the guide rail mechanism comprises a guide rail 15, a small electromagnet i 24, a small spring i 25, a small electromagnet ii 26, a small spring ii 27, a movable rack i 28 and a movable rack ii 29. Wherein, the guide rail 15 is provided with two symmetrical structures which are provided with guide grooves.

As shown in fig. 9, the bottom of the movable rack I28 is provided with two small electromagnets I24 and a small spring I25 which are fixedly connected to the bottom surface of the guide groove of the guide rail 15, and the bottom of the movable rack II 29 is provided with two small electromagnets II 26 and a small spring II 27 which are fixedly connected to the bottom surface of the guide groove of the guide rail 15.

As shown in fig. 6, a fixing block 40 is arranged on the push rod positioning piece 17, a hall proximity switch sensor 33 is arranged on the fixing block 40, and the hall proximity switch sensor 33 can detect the relative position of the fixing block on the push rod positioning piece 17 and the movable rack i 28 in real time. As shown in fig. 8 and 11, a groove 43 matched with the fixing block 40 on the push rod positioning piece 17 is arranged on the movable rack i 28, and the position locking of the push rod positioning piece 17 can be realized through the fixing block 40 and the groove 43. As shown in fig. 6, a rack 42 is provided on the movable platform 14. As shown in fig. 8, a toothed groove matched with the toothed block 42 is formed in the movable rack ii 29, and the position locking of the movable platform 14 can be realized through the matching of the toothed block 42 and the toothed groove. The small spring I25 and the small spring II 27 are in a compressed state, when the small electromagnet I24 is electrified, the movable rack I28 can be adsorbed, the movable rack I28 can move along the radial direction of the guide rail 15, the groove 43 on the movable rack I28 is separated from the fixed block on the push rod positioning piece 17, and the push rod positioning piece 17 can axially rotate; when the small electromagnet II 26 is electrified, the movable rack II 29 is adsorbed, so that the movable rack II 29 moves along the radial direction of the guide rail 15, the tooth-shaped groove on the movable rack II 29 is separated from the tooth-shaped block of the movable platform 14, and the push rod positioning piece 17 can move along the axial direction.

As shown in fig. 10, which is a control flow diagram of the present invention, the switching control method of the present invention is based on a switching control system, and the switching control system includes a variable stiffness transmission joint based on a cam mechanism, a signal acquisition card 34 for acquiring data of a laser displacement sensor 32 and a hall proximity switch sensor 33, a motor driver 39 for controlling the movement of a variable stiffness motor 19, a relay i 36 for correspondingly controlling the loss of power to the large electromagnet 9, the small electromagnet i 24, and the small electromagnet ii 26, a relay ii 37, a relay iii 38, and a controller 35 connected to the signal acquisition card 34, the motor driver 39, the relay i 36, the relay ii 37, and the relay iii 38.

Specifically, the controller 35 receives the laser displacement sensor 32 and the hall proximity switch sensor 33 acquired by the signal acquisition card 34, controls the power failure of the relay i 36, the relay ii 37 and the relay iii 38, and controls the power failure of the large electromagnet 9, the small electromagnet i 24 and the small electromagnet ii 26 correspondingly to the relay i 36, the relay ii 37 and the relay iii 38, and the controller 35 drives the variable stiffness motor 19 to move through the motor driver 39 at the same time, the movement of the variable stiffness motor 19 in the variable stiffness mode affects the output of the laser displacement sensor 32, and the movement of the variable stiffness motor 19 in the transmission mode affects the output of the hall proximity switch sensor 33.

A switching control method of a variable-stiffness transmission joint based on a cam mechanism comprises the following specific steps:

(A) setting a zero point position: the permanent magnet at the bottom of the groove 43 in the movable rack I28 is sensed by the Hall proximity switch sensor 33 and a signal is sent out to determine the zero point position.

Specifically, in order to ensure that the variable stiffness transmission joint does not affect the variable stiffness function of the variable stiffness transmission joint after the variable stiffness transmission joint achieves the transmission function, a zero point position must be set. The zero point position is set to a position where the movable rack i 28 is engaged with the push-rod positioning piece 17. As shown in fig. 11, a permanent magnet is arranged at the bottom of the groove 43 on the movable rack i 28, and when the fixed block 40 on the push rod positioning piece 17 is in a position opposite to the groove 43 on the movable rack i 28, the hall proximity switch sensor 33 senses the permanent magnet at the bottom of the groove 43 on the movable rack i 28, and sends a signal to determine a zero point position.

(B) And determining the target effective deformation length of the torsion bar 16 according to the rigidity value required in the variable-rigidity transmission joint transmission process.

Specifically, in the present embodiment, the target effective deformation length of the torsion bar 16 may be determined as:

where L represents an effective deformation length of the torsion bar 16, E represents an elastic modulus of the torsion bar 16, R represents a rotation radius of the torsion bar 16, d represents a cross-sectional diameter of the torsion bar 16, θ represents a bending angle of the torsion bar 16, and K represents a variable-stiffness transmission joint stiffness value required during transmission.

(C) And (3) rigidity adjustment: the controller 35 controls the large electromagnet 9 and the small electromagnet I24 to lose power and the small electromagnet II 26 to get power through the relay I36, the relay II 37 and the relay III 38. When the large electromagnet 9 is de-energized, the variable stiffness motor 19 and the speed reducer 21 move rightwards under the action of the large spring 10, so that the external gear 20 is meshed with the internal gear on the right end face of the cylindrical cam 13; when the small electromagnet I24 is powered off, the movable rack I28 moves radially inwards under the action of the small spring I25 and is meshed with the fixed block on the push rod positioning piece 17, so that the push rod positioning piece 17 is locked; the small electromagnet II 26 is electrified, the movable rack II 29 is not meshed with the movable platform 14, and the movable platform 14 can axially move along the front shaft I5; after the variable stiffness motor 19 is decelerated by the reducer 21, the cylindrical cam 13 is driven to rotate, the roller 23 rolls on a cam profile line, the push rod 18 is driven to move axially under the limitation of the push rod positioning sheet 17, the movable platform 14 moves axially along the front shaft I5 under the pushing of the push rod 18, the distance between the movable platform 14 and the shaft II 8 is changed, namely the effective deformation length of the torsion bar 16 is changed, the distance between the movable platform 14 and the shaft II 8 is measured by the laser displacement sensor 32, and when the distance value is equal to the target effective deformation length of the torsion bar 16, the variable stiffness motor 19 stops moving.

Specifically, in this embodiment, the controller 35 is a PLC controller, and a stiffness adjustment function control flowchart is shown in fig. 12, where an output port Q0.1 of the PLC controller is connected to the relay i 36, Q0.2 is connected to the relay ii 37, and Q0.3 is connected to the relay iii 38. As shown in fig. 13, which is a schematic diagram of the states of each electromagnet and spring during stiffness variation in the embodiment of the present invention, since the large electromagnet 9 is de-energized, the large spring 10 is in a compressed state in an initial state, and the large spring 10 extends to push the stiffness varying motor 19 to move rightward; because the small electromagnet I24 is powered off, the small spring I25 is in a compressed state in an initial state, and the small spring I25 extends to push the movable rack I28 to be meshed with the push rod positioning sheet 17; the small electromagnet II 26 is electrified, so that the small spring II 27 is further compressed.

(D) The transmission function is realized: the controller 35 controls the large electromagnet 9 and the small electromagnet I24 to be electrified and the small electromagnet II 26 to be deenergized through the relay I36, the relay II 37 and the relay III 38. The large electromagnet 9 is electrified, the variable stiffness motor 19 and the speed reducer 21 move leftwards, and the external gear 20 is not meshed with the internal gear on the right end face of the cylindrical cam 13; the small electromagnet I24 is electrified, the movable rack I28 moves outwards in the radial direction and is not meshed with the fixed block on the push rod positioning piece 17; the small electromagnet II 26 loses power, and under the action of a small spring II 27, the movable rack II 29 is meshed with the gear block on the movable platform 14, so that the movable platform 14 is axially locked; the rear shaft I1 and the front shaft I5 rotate, the variable stiffness motor 19, the speed reducer 21 and the torsion bar 16 rotate around the center of the rear shaft I1, the guide rail 15 is in interference fit with the front shaft I5 and rotates synchronously with the front shaft I5, the movable platform 14 and the guide rail 15 rotate synchronously under the action of the guide rail 15, and the torsion bar 16 between the movable platform 14 and the front shaft I5, the front shaft I5 and the movable platform 14 rotate synchronously, so that the torsion bars only play a connecting role, and the torsion bar between the movable platform 14 and the shaft II 8 bears external torque; at the moment, the variable-rigidity transmission joint can perform transmission under the set rigidity.

Specifically, as shown in fig. 14, it is a flow chart of the transmission function control; fig. 15 is a schematic diagram showing the state of each electromagnet and spring during transmission according to the embodiment of the present invention. Because the large electromagnet 9 is electrified, the large spring 10 is further compressed, and the variable stiffness motor 19 moves leftwards; because the small electromagnet I24 is electrified, the small spring I25 is further compressed, and the movable rack I28 is not meshed with the push rod positioning sheet 17; and when the small electromagnet II 26 is powered off, the small spring II 27 is in a compressed state in the initial state, and the small spring II 27 extends to push the movable platform 14 to be meshed with the movable rack II 29.

(E) Resetting: after the transmission is finished, the controller 35 controls the large electromagnet 9 to lose power through the relay I36, and under the action of the large spring 10, the variable stiffness motor 19 and the speed reducer 21 move rightwards, so that the external gear 20 is meshed with the internal gear on the right end face of the cylindrical cam 13. Whether the front shaft I5 is located at a zero position or not is detected, if not, the variable stiffness motor 19 is started, the push rod positioning piece 17 is driven to rotate through the push rod 18 until the Hall proximity switch sensor 33 detects that the groove 43 on the movable rack I28 and the fixed block 40 on the push rod positioning piece 17 are just located at a right position, the controller 35 controls the small electromagnet I24 to lose power through the relay II 37, and under the action of the small spring I25, the movable rack I is meshed with the fixed block on the push rod positioning piece 17, so that the push rod positioning piece 17 is locked.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The utility model provides a become rigidity transmission joint based on cam mechanism, includes transmission module and becomes rigidity module, its characterized in that: the transmission module includes:

the rear shaft I (1) is provided with a cavity and is internally provided with a large electromagnet (9), a large spring (10), a variable stiffness motor (19) and a speed reducer (21) which are connected in sequence;

the front shaft I (5) is provided with a cavity and is fixedly connected with the rear shaft I (1);

the shaft II (8) is arranged in the cavity of the front shaft I (5) and rotates relative to the front shaft I (5);

the torsion bar (16) is arranged in the cavity of the front shaft I (5), two ends of the torsion bar are connected with the rear shaft I (1) and the shaft II (8), and the torsion bar is used for realizing the transmission of power from the rear shaft I (1) to the shaft II (8);

the variable stiffness module includes:

the cylindrical cam mechanism is arranged in a cavity of the front shaft I (5) through a bearing (12) and is connected with the speed reducer (21);

the movable platform (14) is arranged in the cavity of the front shaft I (5), sleeved on the torsion bar (16) and connected with the cylindrical cam mechanism;

and the guide rail mechanism is in interference fit with the front shaft I (5) and is coaxial with the rear shaft I (1), and is respectively matched with the cylindrical cam mechanism and the movable platform (14).

2. The variable stiffness drive joint based on the cam mechanism as claimed in claim 1, wherein: the cylindrical cam mechanism comprises a cylindrical cam (13) which is arranged in a cavity of the front shaft I (5) through a bearing (12), a push rod positioning piece (17) matched with the guide rail mechanism, a roller (23) arranged on a cam contour line of the cylindrical cam (13), a push rod (18) which penetrates through the push rod positioning piece (17) and is correspondingly connected to the roller (23) and the movable platform (14) at two ends, and an external gear (20) connected with the speed reducer (21).

3. The variable stiffness drive joint based on the cam mechanism as claimed in claim 2, wherein: the cylindrical cam (13) is of a cavity structure, and an inner gear meshed with the outer gear (20) is arranged on the end face of the cylindrical cam (13).

4. The variable stiffness drive joint based on the cam mechanism as claimed in claim 2, wherein: the guide rail mechanism comprises a guide rail (15) with a guide groove, a movable rack I (28) and a movable rack II (29) which are assembled in the guide groove of the guide rail (15), a small electromagnet I (24) and a small electromagnet II (26) which are arranged on the bottom surface of the guide groove of the guide rail (15), a small spring I (25) and a small spring II (27), wherein the small electromagnet I (24) and the small spring I (25) are connected with the movable rack I (28), the small electromagnet II (26) and the small spring II (27) are connected with the movable rack II (29), the movable rack I (28) is matched with a push rod positioning piece (17), and the movable rack II (29) is matched with a movable platform (14).

5. The variable stiffness drive joint based on the cam mechanism as claimed in claim 4, wherein: the push rod positioning piece (17) is provided with a fixing block (40) matched with the movable rack I (28), and the fixing block (40) is provided with a Hall proximity switch sensor (33).

6. The variable stiffness drive joint based on the cam mechanism as claimed in claim 5, wherein: a groove (43) matched with the fixed block (40) is formed in the movable rack I (28), and a permanent magnet is arranged at the bottom of the groove (43).

7. The variable stiffness drive joint based on the cam mechanism as claimed in claim 4, wherein: and a circumferential guide rail (41) connected with one end part of the push rod (18), a toothed block (42) matched with the movable rack II (29) and a laser displacement sensor (32) are arranged on the movable platform (14).

8. The variable stiffness drive joint based on the cam mechanism as claimed in claim 7, wherein: and a toothed groove matched with the toothed block (42) is formed in the movable rack II (29).

9. The switching control method of the variable-stiffness transmission joint based on the cam mechanism is applied to any one of claims 1 to 8, and is characterized in that: the switching control method is based on a switching control system, the switching control system comprises a variable-stiffness transmission joint based on a cam mechanism, a signal acquisition card (34) for acquiring data of a laser displacement sensor (32) and a Hall proximity switch sensor (33), a motor driver (39) for controlling the movement of a variable-stiffness motor (19), a relay I (36) for correspondingly controlling a large electromagnet (9), a small electromagnet I (24), a small electromagnet II (26) to lose power, a relay II (37), a relay III (38), and a controller (35) connected with the signal acquisition card (34), the motor driver (39), the relay I (36), the relay II (37) and the relay III (38), and the switching control method specifically comprises the following steps:

(A) setting a zero point position: the permanent magnet at the bottom of the groove (43) in the movable rack I (28) is sensed through the Hall proximity switch sensor (33), and a signal is sent out to determine the zero point position;

(B) determining the target effective deformation length of the torsion bar (16) according to the rigidity value required in the variable-rigidity transmission joint transmission process;

(C) and (3) rigidity adjustment: the controller (35) controls the large electromagnet (9) to lose power, the small electromagnet I (24) to lose power and the small electromagnet II (26) to get power through the relay I (36), the relay II (37) and the relay III (38), so that the position between the push rod positioning sheet (17) and the guide rail (15) is locked, the variable stiffness motor (19) is in power connection with the cylindrical cam (13), and then the movable platform (14) is driven to move axially along the front shaft I (5) through the cylindrical cam (13) and the push rod (18), so that the distance between the movable platform (14) and the shaft II (8) is adjusted;

(D) the transmission function is realized: the controller (35) controls the large electromagnet (9) to be electrified, the small electromagnet I (24) to be electrified and the small electromagnet II (26) to be deenergized through the relay I (36), the relay II (37) and the relay III (38) so that the push rod positioning sheet (17) and the guide rail (15) are separated from locking, the variable stiffness motor (19) and the cylindrical cam (13) are separated from power connection, the movable platform (14) and the guide rail (15) are locked at positions, the rear shaft I (1) and the front shaft I (5) rotate, and the torsion bar (16) drives the shaft II (8) to synchronously rotate along with the shaft I (1) so as to perform torsion transmission;

(E) resetting: whether the push rod positioning piece (17) is located at a zero position is detected, if the push rod positioning piece is not located at the zero position, the controller (35) controls the large electromagnet (9) to lose power through the relay I (36), so that the variable-stiffness motor (19) is in power connection with the cylindrical cam (13) and then drives the detection push rod positioning piece (17) to rotate until the push rod positioning piece is located at the zero position; if the push rod is in the zero position, the controller (35) controls the small electromagnet I (24) to lose power through the relay II (37), so that the position between the push rod positioning piece (17) and the guide rail (15) is locked.

10. The switching control method of the variable-stiffness transmission joint based on the cam mechanism as claimed in claim 9, wherein: the target effective deformation length of the torsion bar (16) in the step (B) is determined by the following formula:

wherein L represents the effective deformation length of the torsion bar (16), E represents the elastic modulus of the torsion bar (16), R represents the rotation radius of the torsion bar (16), d represents the section diameter of the torsion bar (16), theta represents the bending angle of the torsion bar (16), and K represents the rigidity value of the variable-rigidity transmission joint required in the transmission process.