CN115741770B - Electromagnetic driving type friction variable stiffness compliant joint and working method - Google Patents
Electromagnetic driving type friction variable stiffness compliant joint and working method Download PDFInfo
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Abstract
The invention discloses an electromagnetic driving friction variable stiffness compliant joint and a working method thereof, which are applicable to the technical field of robot control. A main transmission shaft is arranged between the mechanical arm I and the mechanical arm II, the mechanical arm I is connected with a driving motor through a motor bracket, an output shaft of the driving motor is provided with a main gear, the main gear is horizontally meshed with a driven gear, and the center of the driven gear is connected with the tail part of the main transmission shaft; the rigidity-changing module comprises an input friction disc, an output friction disc and an output shaft, wherein the input friction disc and the output friction disc are arranged on the main transmission shaft, and friction surfaces of the input friction disc and the output friction disc are arranged in a relatively matched mode; the input friction disc and the output friction disc are contacted with each other to enable power to be transmitted between the mechanical arm I and the mechanical arm II, the input friction disc and the output friction disc are separated to disconnect transmission, and the change of friction force is achieved by changing positive pressure between the input friction disc and the output friction disc, so that rigidity adjustment is achieved. The device has the characteristics of high safety, compact structure and strong adaptability.
Description
Technical Field
The invention relates to the technical field of robot control, in particular to an electromagnetic driving type friction variable stiffness compliant joint and a working method.
Background
Man-machine cooperation can better exert the advantages of people and robots, and in recent years, man-machine cooperation and man-machine interaction have become important contents of research in the field of robots. However, in the man-machine cooperation process, the man-machine cooperation has great uncertainty due to dynamic change and unpredictability of the environment, which causes great potential safety hazard in the robot man-machine cooperation process.
In order to improve the robot man-machine cooperation safety, a plurality of students gather eyes on the variable-rigidity compliant joint, and the compliant joint introduces a buffer link between a rigid single machine and an end effector, so that the compliant joint can deform to a certain extent under the action of external force, thereby playing a role in temporarily storing collision energy, and having good environmental adaptability and safety. For example, a flexible cable driving robot variable stiffness elastic joint (ZL 201710803257.4) adopts a spring piece as a variable stiffness element and a flexible cable driving device as an adjusting element, so that variable stiffness output of the joint is realized; for example, a variable stiffness joint for a robot and a stiffness adjusting method (ZL 201710160784.8) thereof in China patent adopt a three-link mechanism and a lever mechanism to realize the motion of a stiffness adjusting mechanism in a matched manner, the mechanism has complex transmission motion, and also cannot realize rapid adjustment and overload protection, so that the application occasion is limited; for example, a lever mechanism-based rigidity-changing module (ZL 201810774632.1) adopts a plate spring as a rigidity-changing element, and utilizes a diamond four-bar structure to move to change the effective deformation pivot of the plate spring.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention aims to provide an electromagnetic driving type friction variable stiffness compliant joint and a working method thereof, which overcome the problems of low stiffness adjustment efficiency and poor joint overload protection capability in the prior art.
In order to achieve the above purpose, the electromagnetic driving type friction rigidity-changing flexible joint comprises a mechanical arm I and a mechanical arm II, wherein a main transmission shaft is arranged between the mechanical arm I and the mechanical arm II, the mechanical arm I is connected with a driving motor through a motor bracket, an output shaft of the driving motor is provided with a main gear, the main gear is horizontally meshed with a driven gear, the center of the driven gear is connected with the tail part of the main transmission shaft, a shell I is arranged outside the main gear and the driven gear, a bearing I is arranged between the main transmission shaft and the mechanical arm I, and the main transmission shaft is connected with the mechanical arm II through a rigidity-changing module;
the rigidity-changing module comprises an input friction disc, an output friction disc and an output shaft, wherein the input friction disc and the output friction disc are arranged on the main transmission shaft, and friction surfaces of the input friction disc and the output friction disc are arranged in a relatively matched mode, and the output shaft is used for being connected with the mechanical arm II; the input friction disc and the output friction disc are of disc structures with opposite friction surfaces, the input friction disc is connected with the main transmission shaft through keys and synchronously rotates, a bearing II is arranged on the main transmission shaft next to the input friction disc, a bearing III is arranged on the bearing II through a gasket arranged on the outer edge, a compression ring of a sleeve structure is concentrically arranged on the non-friction surface of the output friction disc, a plurality of groups of coil units are respectively arranged on the compression ring through overhanging connecting lugs, a bearing IV is arranged at the end part of the main transmission shaft, a sleeve is sleeved on the main transmission shaft between the bearing III and the bearing IV, the output shaft is sleeved on the sleeve, two ends of the output shaft are respectively connected with the main transmission shaft through the bearing III and the bearing IV, the length of the output shaft is equal to the distance between the bearing III and the bearing IV, the output friction disc and the compression ring are sleeved on the output shaft, mutually matched splines and spline grooves are arranged on the outer sides of one end of the output shaft, the spline grooves are arranged on the inner sides of the friction disc, the spline grooves are arranged on the outer sides of the output shaft, the lengths of the output shaft are longer than the output friction disc, the output shaft and the positions of the output shaft and the main transmission shaft are unchanged in the axial directions, and the axial movement of the output friction disc on the output shaft is realized; an annular permanent magnet is arranged on the outer side of the surrounding coil unit through a shell II; an end cover for blocking the open hole is arranged at one end of the output shaft, which is not provided with a spline, the inner ring of the bearing IV is contacted with the end cover, the end cover is fixed on the main transmission shaft through a screw, the axial fixation of the inner ring of the bearing IV on the main transmission shaft is realized, and then the axial positioning of the bearing IV on the main transmission shaft is realized; the screw is simultaneously connected with a shell II for covering the variable stiffness module, and a through notch is formed in the axial direction of the shell II, so that a corner difference is allowed to exist between the output shaft and the shell II, and active slipping is allowed when transmission in a range exceeding a set stiffness occurs, so that the transmission protection effect is disconnected;
the coil unit is connected with a direct current power supply module, a rigidity controller and an expert knowledge base in sequence through wires;
the mechanical arm I and the mechanical arm II are enabled to transmit power through the mutual contact of the input friction disc and the output friction disc, the transmission is disconnected when the input friction disc is separated from the output friction disc, the friction force can be changed by changing the positive pressure between the input friction disc and the output friction disc while the transmission is carried out, then the rigidity adjustment is achieved, the positive pressure between the input friction disc and the output friction disc is changed through the electromagnetic interaction force generated by the electrified coil unit and the annular permanent magnet, and the compression ring is pushed to control the connection or disconnection of the output friction disc and the input friction disc.
Further, the outside of the main gear and the driven gear is fixedly provided with a protecting shell I through a screw, the shell II and the end cover are fixedly arranged on the main transmission shaft through screws, and the end cover is not contacted with the output shaft after being installed.
Further, an annular permanent magnet is fixed inside the housing ii and is position-matched with all coil units.
Further, the coil units are of electromagnet structures and are symmetrically arranged at the center, suction force or repulsive force is generated between the coil units and the annular permanent magnets through electrification, and accordingly the output friction disc is pushed to axially move on a spline groove of the output shaft through the spline on the inner side through the compression ring, and the distance between the output friction disc and the input friction disc is controlled.
Further, the bearing II can bear axial load and is a tapered roller bearing or a thrust ball bearing.
Further, the gasket is of a boss structure, and the boss part is contacted with the inner ring of the bearing III.
Further, the expert knowledge base is used for converting the rigidity requirement required by input into output current data of actual control; the expert knowledge base comprises comparison data of the rotation rigidity value and the input current value, after a user inputs the expected value of the rotation rigidity, the current value required by the corresponding rotation rigidity is obtained by inquiring the expert knowledge base, and then the DC power supply module is controlled by the rigidity controller to supply power to the coil unit to form corresponding magnetic force, so that positive pressure between the input friction disc and the output friction disc is influenced, and the friction force is changed.
A working method of a magnetically driven friction variable stiffness compliant joint comprises the following steps:
step one, calibrating the relation between positive pressure between an input friction disc and an output friction disc and a current signal of a coil unit:
the method comprises the steps of installing a diaphragm type pressure sensor for detection between an input friction disc and an output friction disc, giving a coil continuously-changing current in a coil unit through a direct current power supply module, converting the current into magnetic force between the annular permanent magnet and the coil unit, pushing a compression ring by the magnetic force to enable the output friction disc to move towards the input friction disc, generating positive pressure between the input friction disc and the output friction disc after the input friction disc is contacted with the output friction disc, obtaining the positive pressure between the input friction disc and the output friction disc by using the diaphragm type pressure sensor, drawing a relation curve between a current value in the coil and the positive pressure between the input friction disc and the output friction disc, intercepting a section with better linearization as a working section, and carrying out linear fitting based on a least square method, so as to obtain an analytic relation between the current value in the coil and the positive pressure between the input friction disc and the output friction disc;
calibrating the relation between positive pressure between the input friction disc and the output friction disc and the rotation rigidity of the output shaft, and determining an expert knowledge base of the relation between the current signal of the coil unit and the rotation rigidity of the output shaft:
according to the actual structural layout of the electromagnetic driving type friction variable stiffness compliant joint, a finite element analysis model of an input friction disc, an output friction disc and an output shaft is constructed in software ANSYS, zero displacement constraint of the input friction disc is given, a discrete point is selected by taking/N of a positive pressure change range in the working interval as a step length based on the working interval determined in the step one, N is a difference value between the maximum value and the minimum value of the positive pressure in the working interval, positive pressure of the output friction disc is given, rotational stiffness of the output shaft is obtained through statics analysis, a curve of the relationship between the positive pressure of the input friction disc and the rotational stiffness of the output friction disc is drawn by the description point, curve fitting is carried out based on a least square method, the analysis relationship between the current value in the coil and the positive pressure between the input friction disc and the output friction disc determined in the step one is further determined, the relationship between the current value sent to a coil unit and the rotational stiffness of the input friction disc and the output friction disc is further determined, the relationship between the current value in the coil and the rotational stiffness of the output friction disc is mapped, and the relationship between the current value in the coil unit and the rotational stiffness of the output shaft is determined;
and thirdly, determining an expected value of the rotation rigidity of the output shaft according to actual use requirements, setting a current value of a coil unit by the rigidity controller through the direct-current power supply module, starting the driving motor, and rotating the output shaft under the expected rotation rigidity.
Further, according to actual use requirements, an expected value of the rotational rigidity of the output shaft is determined, according to the relation between a coil unit current signal recorded in an expert knowledge base and the rotational rigidity of the output shaft, the rigidity controller gives the coil unit current value through the direct-current power supply module, under the electromagnetic force action of the coil unit and the annular permanent magnet, the output friction disc is pushed to move by the pressing ring through a spline and a spline groove between the output friction disc and the output shaft and is pressed against the input friction disc, so that positive pressure between the output friction disc and the input friction disc meets the requirements, the driving motor is started, power is transmitted to the main transmission shaft through the main gear and the driven gear, the main transmission shaft transmits the power to the input friction disc through key connection, and the power is further transmitted to the output shaft through spline connection between the output friction disc and the output shaft, so that the output shaft can rotate under the expected rotational rigidity.
Further, during operation, the rotation speed/rotation angle of the shell II is consistent with that of the main transmission shaft and that of the input friction disc, and the rotation speed/rotation angle of the output shaft is consistent with that of the output friction disc, under normal conditions, the rotation speed/rotation angle of the input friction disc is the same as that of the output friction disc, but when external load is relatively large, such as sudden collision, the input friction disc and the output friction disc can exceed the slip condition of the set transmission rigidity, at the moment, the rotation angle difference exists between the output shaft and the shell II, so that an axial gap is arranged on the shell II, a certain rotation angle space is reserved for enabling the output shaft/the output friction disc to actively slip relative to the main transmission shaft/the input friction disc when the transmission exceeds the set rigidity range, and the transmission is disconnected, so that a protection effect is achieved.
The beneficial effects are that:
1) The device adopts the friction transmission between the input friction disk and the output friction disk to realize variable stiffness output, so that the safety of the variable stiffness compliant joint can be effectively improved, and the overload protection capability of the joint is greatly enhanced; 2) The electromagnetic drive is integrated, so that the positive pressure between the input friction disk and the output friction disk is changed, and then the friction force between the input friction disk and the output friction disk is changed, and the variable stiffness type variable stiffness hydraulic pump has the characteristics of simple variable stiffness adjusting principle and high adjusting speed; the shell II is axially provided with a through gap, so that a corner difference is allowed to exist between the output shaft and the shell II, and the transmission is allowed to actively slip when the transmission exceeds a set rigidity range, so that the transmission protection effect is disconnected; 3) The main transmission shaft is adopted as a support, and the output shaft is sleeved outside, so that the device has the characteristics of compact structure and strong adaptability.
Drawings
FIG. 1 is a schematic view of an electromagnetically driven friction variable stiffness compliant joint structure of the present invention;
FIG. 2 is an exploded view of an electromagnetically driven friction variable stiffness compliant joint of the present invention;
FIG. 3 is a schematic diagram of the coupling relationship of the output friction disc, the compression ring and the coil unit of the present invention;
FIG. 4 is a schematic illustration of the coupling relationship of the output shaft and the output friction disk of the present invention;
FIG. 5 is a schematic diagram showing the assembly relationship between a housing II and an annular permanent magnet according to the present invention;
FIG. 6 is a workflow diagram of an electromagnetically driven friction variable stiffness compliant joint of the present invention;
FIG. 7 is a schematic view of an embodiment of an electromagnetically driven friction variable stiffness compliant joint of the present invention.
In the figure: 1-driving motor, 2-shell I, 3-arm I, 4-main drive shaft, 5-shell II, 6-motor support, 7-main gear, 8-driven gear, 9-bearing I, 10-rigidity changing module, 10-1-input friction disk, 10-2-output friction disk, 10-3-compression ring, 10-4-coil unit, 10-5-output shaft, 11-bearing II, 12-gasket, 13-bearing III, 14-bearing IV, 15-sleeve, 16-end cover, 17-annular permanent magnet, 18-screw, 19-DC power module, 20-expert knowledge base and 21-rigidity controller.
Detailed Description
The invention will be described in detail below with reference to the drawings and examples, but the practice of the invention is not limited thereto.
As shown in fig. 1, the electromagnetic driving friction rigidity-changing flexible joint comprises a driving motor 1, a shell I2, a mechanical arm I3, a main transmission shaft 4, a shell II 5, a motor bracket 6, a main gear 7, a driven gear 8, a bearing I9, a rigidity-changing module 10, a bearing II 11, a gasket 12, a bearing III 13, a bearing IV 14, a sleeve 15, an end cover 16 and an annular permanent magnet 17.
As shown in fig. 2, the bearing ii 11 in this embodiment is a thrust ball bearing. The driving motor 1 is arranged on the mechanical arm I3 through a motor bracket 6, and a main gear 7 is fixed on an output shaft of the driving motor 1 and meshed with a driven gear 8 to transmit the power of the driving motor 1 to a main transmission shaft 4 connected with the driven gear 8; the shell I2 is fixed on the mechanical arm I3 through a screw, and covers the main gear 7 and the driven gear 8; the main transmission shaft 4 is sequentially provided with a bearing I9, a bearing II 11, a gasket 12, a bearing III 13 and a bearing IV 14, the outer ring of the bearing I9 is arranged on the mechanical arm I3, the end cover 16 is fixed on the main transmission shaft 4 through a screw 18 and realizes the axial fixation of the inner ring of the bearing IV 14 on the main transmission shaft 4, and the shell II 5 is also fixed on the main transmission shaft 4 through the screw 18;
the rigidity-changing module 10 comprises an input friction disc 10-1, an output friction disc 10-2, a compression ring 10-3,2 groups of coil units 10-4 and an output shaft 10-5; as shown in fig. 2 and 3, the 2 groups of coil units 10-4 are arranged on the pressing ring 10-3 in a central symmetry manner, the pressing ring 10-3 is close to one end of the output friction disk 10-2 with smaller diameter, and the pressing ring 10-3 is coaxial with the output friction disk 10-2; the input friction disc 10-1 is connected with the main transmission shaft 4 through key transmission, the right end of the input friction disc 10-1 is sequentially connected with a bearing II 11, a gasket 12 and a bearing III 13, as shown in FIG. 3, a round hole is formed in the middle of the output friction disc 10-2, and the structure is ensured not to interfere when the input friction disc 10-1 is contacted with the output friction disc 10-2; a sleeve 15 is connected between the outer ring of the bearing IV 14 and the inner ring of the bearing III 13; the output shaft 10-5 passes through a round hole in the middle of the compression ring 10-3 and is sleeved on the sleeve 15, and two ends of the output shaft 10-5 are respectively connected with the outer ring of the bearing III 13 and the outer ring of the bearing IV 14.
The output friction disc 10-2 is contacted with one end of the compression ring 10-3 and coaxially sleeved on the output shaft 10-5, as shown in fig. 4, the output friction disc 10-2 is connected with the output shaft 10-5 through a spline, and the axial movement of the output friction disc 10-2 on the output shaft 10-5 can be realized.
The other end of the compression ring 10-3 is provided with 2 groups of coil units 10-4, and as shown in fig. 5, an annular permanent magnet 17 is arranged on the housing II 5 at a position opposite to the 2 groups of coil units 10-4.
As shown in FIG. 6, the working method of the electromagnetic driving type friction variable stiffness compliant joint comprises the following steps:
step one, calibration of the relationship between the positive pressure between the input friction disk 10-1 and the output friction disk 10-2 and the current signal of the coil unit 10-4
Installing a diaphragm type pressure sensor between an input friction disc 10-1 and an output friction disc 10-2, giving a coil unit 10-4 a continuously variable current through a direct current power supply module 19, obtaining positive pressure between the input friction disc 10-1 and the output friction disc 10-2 by using the diaphragm type pressure sensor, drawing a relation curve between a current value in the coil and the positive pressure between the input friction disc 10-1 and the output friction disc 10-2, intercepting a section with better linearization as a working section, and performing linear fitting based on a least square method to obtain an analytic relation between the current value in the coil and the positive pressure between the input friction disc 10-1 and the output friction disc 10-2;
step two, calibrating the relation between the positive pressure between the input friction disk 10-1 and the output friction disk 10-2 and the rotational rigidity of the output shaft 10-5, and determining the expert knowledge base 20 of the relation between the current signal of the coil unit 10-4 and the rotational rigidity of the output shaft 10-5
According to the actual structural layout of the electromagnetic driving type friction variable stiffness compliant joint, a finite element analysis model of an input friction disc 10-1, an output friction disc 10-2 and an output shaft 10-5 is constructed in ANSYS, zero displacement constraint of the input friction disc 10-1 is given, based on a working interval determined in the step one, 1/N of a positive pressure change range in the working interval is taken as a step length, a discrete point is selected, wherein N is a difference value between the maximum value and the minimum value of the positive pressure in the working interval, the positive pressure of the output friction disc 10-2 is given, rotational stiffness of the output shaft 10-5 is obtained through statics analysis, a curve of the relation between the positive pressure of the input friction disc 10-1 and the output friction disc 10-2 and the rotational stiffness of the output shaft 10-5 is drawn by a description point, curve fitting is carried out based on a least square method, the analysis relation between the current value in a coil and the positive pressure of the input friction disc 10-1 and the output friction disc 10-2 is further combined, the relation between the current value in the coil and the rotational stiffness of the output shaft 10-5 is mapped, and an expert knowledge base 20 of the relation between the current signal in the coil and the rotational stiffness of the output shaft 10-5 is determined;
step three, according to the actual use requirement, determining the expected value of the rotation rigidity of the output shaft 10-5, and setting the current value of the coil unit 10-4 by the rigidity controller 21 through the direct current power supply module 19
As shown in the left diagram of fig. 7, the initial state input friction disk 10-1 is not in contact with the output friction disk 10-2, and the power of the driving motor 1 cannot be transmitted to the output shaft 10-5; according to the actual use requirement, the expected value of the rotation rigidity of the output shaft 10-5 is determined, according to the expert knowledge base 20 of the relation between the current signal of the coil unit 10-4 and the rotation rigidity of the output shaft 10-5 determined in the second step, the rigidity controller 21 gives the current value of the coil unit 10-4 through the direct current power supply module 19, at this time, as shown in the right diagram of fig. 7, the input friction disc 10-1 contacts with the output friction disc 10-2, the driving motor 1 is started, the power is transmitted to the main transmission shaft 4 through the main gear 7 and the driven gear 8, the main transmission shaft 4 transmits the power to the input friction disc 10-1 through the key connection, the power is transmitted to the output friction disc 10-2 through the friction transmission, the power is further transmitted to the output shaft 10-5 through the spline connection between the output friction disc 10-2 and the output shaft 10-5, and the output shaft 10-5 rotates under the expected rotation rigidity.
Claims (10)
1. An electromagnetic drive type friction variable stiffness compliant joint is characterized in that: the mechanical arm comprises a mechanical arm I (3) and a mechanical arm II, wherein a main transmission shaft (4) is arranged between the mechanical arm I (3) and the mechanical arm II, the mechanical arm I (3) is connected with a driving motor (1) through a motor bracket (6), an output shaft of the driving motor (1) is provided with a main gear (7), the main gear (7) is horizontally meshed with a driven gear (8), the center of the driven gear (8) is connected with the tail part of the main transmission shaft (4), a shell I (2) is arranged outside the main gear (7) and the driven gear (8), a bearing I (9) is arranged between the main transmission shaft (4) and the mechanical arm I (3), and the main transmission shaft (4) is connected with the mechanical arm II through a rigidity changing module (10);
the rigidity-changing module (10) comprises an input friction disc (10-1), an output friction disc (10-2) and an output shaft (10-5) which are arranged on the main transmission shaft (4) and are in opposite matching arrangement with the friction surface, wherein the output shaft is used for being connected with the mechanical arm II; the input friction disk (10-1) and the output friction disk (10-2) are of disc structures with opposite friction surfaces, the input friction disk (10-1) is connected with the main transmission shaft (4) through a key and synchronously rotates, a bearing II (11) is arranged on the main transmission shaft (4) next to the input friction disk (10-1), a bearing III (13) is arranged on the bearing II (11) through a gasket (12) arranged on the outer edge, a pressing ring (10-3) of a sleeve structure is concentrically arranged on the non-friction surface of the output friction disk (10-2), a plurality of groups of coil units (10-4) are respectively arranged on the pressing ring (10-3) through an overhanging connecting lug, a sleeve (15) is sleeved on the main transmission shaft (4) between the bearing III (13) and the bearing IV (14), the output shaft (10-5) is sleeved on the sleeve (15) and two ends of the output shaft (10-5) are respectively connected with the main transmission shaft through the bearing III (13) and the bearing IV (14), the length of the output shaft (10-5) is equal to the distance between the bearing III (13) and the bearing IV (14), the output friction disk (10-2) is sleeved on the pressing ring (10-5), the inner wall of the output friction disk (10-2) and the outer side of one end of the output shaft (10-5) are provided with mutually matched spline grooves and spline grooves, wherein the spline grooves are arranged on the inner side of the friction disk (10-2), the spline grooves are arranged on the outer side of the end part of the output shaft (10-5), the length of the spline grooves on the output shaft (10-5) is longer than that of the output friction disk (10-2), the positions of the output shaft (10-5) and the main transmission shaft (4) in the axial direction are unchanged, and the axial movement of the output friction disk (10-2) on the output shaft (10-5) is realized; an annular permanent magnet (17) is arranged on the outer side of the surrounding coil unit (10-4) through a shell II (5); an end cover (16) for blocking the open hole is arranged at one end of the output shaft (10-5) which is not provided with a spline, the inner ring of the bearing IV (14) is in contact with the end cover (16), the end cover (16) is fixed on the main transmission shaft (4) through a screw (18) and realizes the axial fixation of the inner ring of the bearing IV (14) on the main transmission shaft (4), and then the axial positioning of the bearing IV (14) on the main transmission shaft (4) is realized; the screw (18) is simultaneously connected with a shell II (5) for covering the variable-rigidity module (10), and a penetrating notch is formed in the axial direction of the shell II (5), so that a corner difference is allowed to exist between the output shaft (10-5) and the shell II (5), and active slipping is allowed when transmission occurs within a range exceeding a set rigidity range, and the transmission protection effect is disconnected;
the coil unit (10-4) is connected with a direct current power supply module (19), a rigidity controller (21) and an expert knowledge base (20) in sequence through wires;
the mechanical arm I (3) and the mechanical arm II are enabled to transmit power through the mutual contact of the input friction disc (10-1) and the output friction disc (10-2), the transmission is disconnected when the input friction disc (10-1) is separated from the output friction disc (10-2), the friction force can be changed by changing the positive pressure between the input friction disc and the output friction disc while the transmission is carried out, then the rigidity adjustment is achieved, the positive pressure between the input friction disc (10-1) and the output friction disc (10-2) is changed through the electromagnetic interaction force generated between the electrified coil unit (10-4) and the annular permanent magnet (17), and the pressure ring (10-3) is pushed so as to control the connection or disconnection of the output friction disc (10-2) and the input friction disc (10-1).
2. The electromagnetically driven friction variable stiffness compliant joint as claimed in claim 1, wherein: a protective shell I (2) is fixed on the outer sides of the main gear (7) and the driven gear (8) through screws, a shell II (5) and an end cover (16) are fixed on the main transmission shaft (4) through screws (18), and the end cover (16) is required to be prevented from being contacted with the output shaft (10-5) after installation.
3. The electromagnetically driven friction variable stiffness compliant joint according to claim 2, wherein: the annular permanent magnet (17) is fixed inside the shell II (5) and is matched with all the coil units (10-4) in position.
4. The electromagnetically driven friction variable stiffness compliant joint as claimed in claim 3, wherein: the coil units (10-4) are of electromagnet structures and are symmetrically arranged at the center, suction force or repulsion force is generated between the coil units and the annular permanent magnet (17) through electrifying, so that the output friction disc (10-2) is pushed by the compression ring (10-3) to axially move on a spline groove of the output shaft (10-5) through an inner spline, and the distance between the output friction disc (10-2) and the input friction disc (10-1) is controlled.
5. The electromagnetically driven friction variable stiffness compliant joint as claimed in claim 1, wherein: the bearing II (11) can bear axial load and is a tapered roller bearing or a thrust ball bearing.
6. The electromagnetically driven friction variable stiffness compliant joint as claimed in claim 1, wherein: the gasket (12) is of a boss structure, and the boss part is contacted with the inner ring of the bearing III (13).
7. The electromagnetically driven friction variable stiffness compliant joint as claimed in claim 1, wherein: the expert knowledge base (20) is used for converting the rigidity requirement required by input into output current data of actual control; the expert knowledge base comprises comparison data of the rotation rigidity value and the input current value, after a user inputs the expected value of the rotation rigidity, the current value required by the corresponding rotation rigidity is obtained by inquiring the expert knowledge base (20), and then the stiffness controller (21) controls the direct-current power supply module (19) to supply power to the coil unit (10-4) to form corresponding magnetic force, so that positive pressure between the input friction disc (10-1) and the output friction disc (10-2) is influenced, and the friction force is changed.
8. A method of operating an electromagnetically driven friction variable stiffness compliant joint as defined in claim 1, comprising the steps of:
step one, calibrating the relation between positive pressure between an input friction disc (10-1) and an output friction disc (10-2) and current signals of a coil unit (10-4):
the method comprises the steps of installing a diaphragm type pressure sensor for detection between an input friction disc (10-1) and an output friction disc (10-2), giving a coil unit (10-4) a current continuously changing through a direct current power supply module (19), converting the current into magnetic force between the coil unit and an annular permanent magnet (17), pushing a compression ring (10-3) by the magnetic force to enable the output friction disc (10-2) to move towards the input friction disc (10-1), enabling the input friction disc (10-1) to be in contact with the output friction disc (10-2) to generate positive pressure, obtaining the positive pressure between the input friction disc (10-1) and the output friction disc (10-2) by utilizing the diaphragm type pressure sensor, drawing a relation curve between a current value in a coil and the positive pressure between the input friction disc (10-1) and the output friction disc (10-2), intercepting a section which is better to be used as a working section, and carrying out linear fitting based on a least square method, and obtaining an analysis relation between the current value in the coil and the positive pressure between the input friction disc (10-1) and the output friction disc (10-2);
calibrating the relation between positive pressure between the input friction disc (10-1) and the output friction disc (10-2) and the rotational rigidity of the output shaft (10-5), and determining an expert knowledge base (20) of the relation between the current signal of the coil unit (10-4) and the rotational rigidity of the output shaft (10-5):
according to the actual structural layout of the electromagnetic driving friction variable stiffness compliant joint, constructing a finite element analysis model of an input friction disc (10-1), an output friction disc (10-2) and an output shaft (10-5) in software ANSYS, giving zero displacement constraint to the input friction disc (10-1), selecting discrete points by taking 1/N of a positive pressure change range in the working interval as step length based on the working interval determined in the step one, wherein N is the difference value between the maximum value and the minimum value of the positive pressure in the working interval, giving positive pressure to the output friction disc (10-2), obtaining the rotational stiffness of the output shaft (10-5) through statics analysis, drawing a relation curve between the positive pressure between the input friction disc (10-1) and the output friction disc (10-2) and the rotational stiffness of the output shaft (10-5) based on the least square method, combining the relation between the current value in the coil determined in the step one and the positive pressure between the input friction disc (10-1) and the output friction disc (10-2), further determining the relation between the current value sent to the coil unit (10-4) and the output friction disc (10-5), mapping the rotational stiffness of the output shaft (10-5), an expert knowledge base (20) for determining the relation between the current signal of the coil unit (10-4) and the rotational stiffness of the output shaft (10-5);
and thirdly, determining an expected value of the rotation rigidity of the output shaft (10-5) according to actual use requirements, and starting the driving motor (1) by the rigidity controller (21) through the direct current power supply module (19) given by the current value of the coil unit (10-4), wherein the output shaft (10-5) rotates under the expected rotation rigidity.
9. The method of operation of claim 8, wherein: according to the actual use requirement, the expected value of the rotation rigidity of the output shaft (10-5) is determined, according to the relation between the current signal of the coil unit (10-4) recorded in the expert knowledge base (20) and the rotation rigidity of the output shaft (10-5), the rigidity controller (21) gives the current value of the coil unit (10-4) through the direct current power supply module (19), the coil unit (10-4) and the annular permanent magnet (17) are subjected to electromagnetic force, the output friction disc (10-2) is pushed to move by the pressure ring (10-3) through the spline and the spline groove between the output friction disc (10-2) and the output shaft (10-5), the pressure ring is pressed to the input friction disc (10-1), the positive pressure between the output friction disc (10-2) and the input friction disc (10-1) is enabled to meet the requirement, the driving motor (1) is started, the power is transmitted to the main transmission shaft (4) through the main gear (7) and the driven gear (8), the power is transmitted to the input friction disc (10-1) through the key connection, the power is transmitted to the output friction disc (10-2) through the friction transmission, the power is further transmitted to the output friction disc (10-5) through the friction transmission, thereby enabling the output shaft (10-5) to rotate at a desired rotational stiffness.
10. The method of operation of claim 8, wherein: when the transmission device works, the rotating speed/rotating angle of the shell II (5) is consistent with that of the main transmission shaft (4) and that of the input friction disc (10-1), the rotating speed/rotating angle of the output shaft (10-5) is consistent with that of the output friction disc (10-2), and under normal conditions, the rotating speed/rotating angle of the input friction disc (10-1) and that of the output friction disc (10-2) are the same, but when external loads are relatively large, such as sudden collision, the input friction disc (10-1) and the output friction disc (10-2) can exceed the slip condition of the set transmission rigidity, at the moment, the rotating angle difference exists between the output shaft (10-5) and the shell II (5), so that an axial notch is formed in the shell II (5), and a certain rotating angle space is provided for enabling the output shaft (10-5)/the output friction disc (10-2) to actively slip when the transmission exceeds the set rigidity range relative to the main transmission shaft (4)/the input friction disc (10-1), and the transmission is disconnected, so that the protection effect is achieved.
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