An electromagnetically driven highly integrated spherical motor and its control method

Abstract

The present invention belongs to the field of automation engineering technology, and relates to an electromagnetically driven highly integrated spherical motor and a control method thereof, specifically a highly integrated spherical motor device for a robot that only requires a follow-up mechanism formed by a coaxial connection with an output end through an external universal joint unit, and a built-in radially magnetized permanent magnet, which can achieve two-degree-of-freedom rotation of side and pitch under the direct drive of the coaxial follow-up magnetic torque of a universal rotating magnetic field in space. The rotation center of the external universal joint of the novel electromagnetically driven two-degree-of-freedom highly integrated spherical motor of the present invention is the rotation center of the spherical motor, which reliably realizes the motion decoupling of the two degrees of freedom of the motor, and the side and pitch angles can be measured and controlled separately. The motor has a compact and simple structure, flexible rotation, is not easily interfered with, has good motion stability, high positioning accuracy, and stable braking. Since the motor adopts a multi-layer nested structure based on a three-axis orthogonal combination coil, the motor has a large uniform magnetic field area, a compact structure, and a high energy output density.

Description

Technical Field

[0001] The present invention belongs to the field of automation engineering technology and relates to an electromagnetically driven highly integrated spherical motor and a control method thereof. Specifically, the present invention is a highly integrated spherical motor device which realizes two-degree-of-freedom rotation of roll and pitch by directly driving a follow-up mechanism composed of a coaxial connection between an external universal joint unit and an output end and a radially magnetized permanent magnet built in the follow-up mechanism under the direct drive of the coaxial follower magnetic torque of a universal rotating magnetic field in space. Background Art

[0002] Due to the high complexity of the robot's multi-degree-of-freedom wrist mechanical system structure and the nonlinear characteristics of the motion transmission system friction, it ultimately leads to problems such as poor dynamic performance of the mechanical structure wrist, low control accuracy, low mechanical efficiency, and poor reliability.

[0003] To overcome the aforementioned drawbacks of mechanical transmission wrists, simplify and lighten the multi-DOF wrist transmission system, and significantly improve motion performance, transmission efficiency, control response speed, and positioning accuracy, an electromagnetic direct-drive multi-DOF motor can be used to replace the complex transmission wrist. Multi-DOF motors offer high integration, a simple transmission chain with no mechanical backlash, and high utilization of effective materials and control system components. In particular, their multiple rotational degrees of freedom significantly simplify the mechanical system structure, avoid nonlinear friction in the joints, and improve both the static and dynamic performance of the system.

[0004] Spherical motors are a high-tech technology that integrates modern motor design theory, power electronics, and automatic control theory. A spherical motor itself is a direct-drive spherical active joint. Based on their principle, they can be classified into the following categories: synchro, induction, and permanent magnet (including DC, stepper, reluctance, and synchronous). Overcoming many of the shortcomings of coil-type spherical motors, permanent magnet spherical motors offer a compact footprint, high system efficiency, and a high magnetic energy product. They hold great promise for applications in multi-dimensional servo control systems, such as robotics, multi-directional transmission mechanisms, and manufacturing.

[0005] At present, electromagnetic spherical motors generally have the following problems in terms of body structure design, electromagnetic and torque analysis and control: 1) Difficulty in calculating the magnetic field. The magnetic field of a spherical motor is a three-dimensional magnetic field and is extremely complex. Currently, the magnetic field calculations of spherical motors are all based on idealized hypothetical models, and the magnetic field cannot be accurately modeled and calculated. 2) Electromagnetic coupling problem. The electromagnetic coupling and mechanical coupling relationships between the degrees of freedom of a spherical motor are complex. How to quantitatively analyze these coupling relationships based on the magnetic field model and achieve precise decoupling is an urgent problem to be solved in the research of spherical motor design and precise control. 3) Optimization of structural parameters of new spherical motors. Based on the accurate modeling of the spherical motor, the structural parameters of the spherical motor body must be optimized with the goal of increasing its output torque, reducing its size, improving response sensitivity and positioning accuracy.

[0006] To address these challenges, innovations in the principles of electromagnetically driven spherical joints are essential. New spherical motors must facilitate the establishment of accurate mechanical and kinematic models, identify appropriate path planning algorithms, and improve the motor's dynamic performance and stability. These are fundamental to precise control of spherical motors and are essential for their application in precision industry.

[0007] To achieve innovation in the principles of electromagnetically driven spherical joints, breakthroughs in space universal rotating magnetic field technology are essential. Because the space universal rotating magnetic field is a single, uniform rotating magnetic field generated by the linear superposition of three orthogonal Helmholtz coils, it eliminates magnetic field coupling issues, offers high magnetic field control precision, and eliminates magnetic force coupling. The magnetic poles are only acted upon by pure electromagnetic drive torque, facilitating the establishment of accurate mechanical and motion models. Therefore, the use of space universal rotating magnetic field technology offers significant advantages and is expected to significantly improve spherical motor control accuracy. To achieve universal control of spherical motors, controlling the rotating magnetic field's orientation and rotational direction is crucial.

[0008] To enable the capsule robot to move freely in the curved intestinal environment, the national invention patent "Universal rotating magnetic field drive control method for in-vivo medical microrobot" (patent authorization number: ZL 200810011110.2) proposes a spatial universal rotating magnetic field control method with adjustable rotation axis, and gives the basic current superposition formula of the rotating magnetic field applicable to the first quadrant of space.

[0009] To achieve universal adjustability of the rotating magnetic field axis, the basic current superposition formula is extended to the other seven quadrants of space. The national invention patent, "Control Method for the Azimuth and Rotational Direction of the Rotating Axis of a Space-Universal Superimposed Rotating Magnetic Field" (Patent Authorization No.: ZL 201210039753.4), utilizes a combined drive mode of anti-phase currents of three-phase sinusoidal current signals in the basic current superposition formula with the three azimuth angles of a fixed axis in space as input variables, based on the variation pattern of the azimuth and rotational direction of the rotating axis of the space-universal uniform rotating magnetic field superimposed within a three-axis orthogonal nested Helmholtz coil device. This achieves unique control of the azimuth and rotational direction of the rotating axis of the space-universal rotating magnetic field within each quadrant of the spatial coordinate system. This theoretically solves the problem of achieving arbitrary adjustment of the azimuth, rotational direction, strength, and rotational speed of the space-universal rotating magnetic vector through digital control, laying the foundation for achieving posture adjustment and directional driven walking for robots.

[0010] During research on the capsule robot's posture control process, researchers discovered that when driven by a universal rotating magnetic field, the axis of a radially magnetized NdFeB permanent magnet cylinder experiences a rotating magnetic field coaxial follower magnetic moment effect. Specifically, when an angle exists between the NdFeB cylinder axis and the rotating magnetic field axis, the rotating magnetic field's coaxial follower magnetic moment pulls the NdFeB cylinder axis toward the rotating magnetic field axis until they coincide. This spatial universal rotating magnetic field coaxial follower magnetic moment can guide the permanent magnet axis to any position in space, laying the foundation for the capsule robot's turning control within the gastrointestinal tract.

[0011] In order to solve the problem of the separation of posture adjustment and turning walking of the capsule robot during gastrointestinal tract diagnosis, the national invention patent "An active and passive dual-hemispherical capsule robot and its posture adjustment and turning drive control method" (patent authorization number: ZL 201510262778.4) utilizes the flexibility and omnidirectionality of the spherical structure to avoid the rolling motion of the spherical robot during posture adjustment. Combined with the coaxial follower magnetic moment effect of the spatial universal rotating magnetic field, when the radially magnetized cylindrical magnet rotates following the spatial universal rotating magnetic field, its axis direction always follows and eventually remains consistent with the direction of the normal vector of the rotating magnetic field (the magnetic field rotation axis), which enables the active and passive dual-hemispherical structure capsule robot to freely adjust its posture and turn walking in the body. Studies have shown that the orientation of the spatial universal rotating magnetic field and the error of the terminal circular trajectory directly affect the control accuracy of the robot.

[0012] The space universal rotating magnetic field has successfully achieved effective control of the posture of the dual-hemisphere capsule, and also laid the foundation for the development of universal spherical motors. To facilitate the universal control and application of the roll and pitch posture of the universal spherical motor, the national invention patent "A human-computer interactive control method for space universal rotating magnetic fields" (patent authorization number: ZL 201610009285.4) proposed a space universal rotating magnetic field superposition formula in the form of current in the longitude and latitude coordinate system with the roll and pitch angles as input variables.

[0013]

[0014] in Where θ and δ are the roll and pitch angles of the robot's axes, I0 is the amplitude of the sinusoidal current in the three sets of orthogonal Helmholtz coils, and ω is the angular frequency of the applied sinusoidal current signal, with the frequency of the applied sinusoidal current signal being f = 2π / ω. The three-dimensional superposition problem of spatial universal rotating magnetic fields is transformed into a two-dimensional superposition problem within a plane, and the roll and pitch angles are controlled separately via two joysticks, achieving interactive control of low-dimensional separable variables. The drive of the three-axis orthogonal Helmholtz coils generates a spatial universal rotating magnetic field control mode with azimuthally separable variables for the roll and pitch angles of the robot's axes, fully capable of controlling the roll and pitch angles of the novel wrist.

[0015] To overcome the limitations of existing permanent magnet motors, such as distorted coupling magnetic fields and complex control processes, innovations in the principles of electromagnetically driven spherical joints are essential. Furthermore, new electromagnetic drive technologies must be developed that are more efficient, fast, and accurate in a uniform, universally rotating magnetic field. The coaxial follower magnetic moment in the universally rotating magnetic field can guide the axis of the permanent magnet to any position in space, laying the foundation for electromagnetic drive of spherical joint posture conversion.

[0016] Given the advantages of pure magnetic torque manipulation and based on the coaxial follower magnetic torque effect, the invention patent applied for by Dalian University of Technology, "An Electromagnetically Driven Two-Degree-of-Freedom Spherical Robot Wrist and Its Control Method" (Patent Authorization No. ZL202010484343.5), proposes a dynamic balance control scheme for manipulating the position of the spherical motor output terminal using pure magnetic torque coupled with a spatial universal rotating magnetic field. Under the action of the coaxial follower magnetic torque effect, the axial direction of the radially magnetized cylindrical magnet always follows and ultimately aligns with the direction of the normal vector of the rotating magnetic field (the magnetic field rotation axis) as it rotates with the spatial universal rotating magnetic field. By solving the spatial universal rotating magnetic field control technology with two attitude angles as input variables (Patent Authorization No.: ZL201610009285.4), universal control of the spherical motor output terminal's roll and pitch can be achieved, achieving the unification of magnetic field and spherical motor orientation control. The coaxial follower magnetic torque effect provides a new exploration approach for driving spherical motors.

[0017] like Figure 1 As shown, the national invention patent "An electromagnetically driven two-degree-of-freedom spherical robot wrist and its control method" (patent authorization number: ZL 202010484343.5) describes an electromagnetically driven two-degree-of-freedom spherical robot wrist, that is, a spherical motor, including a three-axis Helmholtz coil group A and a follower part b; wherein, the three-axis orthogonal Helmholtz coil group A provides a space universal rotating magnetic field, and the follower part b provides a rotating magnetic field coaxial follower magnetic torque to drive the lower side swing and pitch two degrees of freedom rotation. Figure 2 As shown, the follower part b includes an inner cross joint D, an outer cross joint c and a fixed end e.

[0018] The three-axis Helmholtz coil assembly A includes a large coil assembly, a small coil assembly, and an intermediate coil assembly, each of which includes two identical coils arranged symmetrically. The axes of the three coil groups are perpendicular to each other and fixed to each other. The bottom of the large coil assembly is fixed to the fixed end e, and the axis of the intermediate coil assembly coincides with the axis of the fixed end e. The internal cross universal joint D is located in the internal space between the three coil groups, and the external cross universal joint C is located outside the three coil groups. The external cross universal joint C, the three-axis Helmholtz coil assembly A, and the internal cross universal joint D form a three-layer nested structure in space.

[0019] The follower part (b) consists of an internal cross-joint (D) (which houses the rotor's permanent magnets), an external cross-joint (C) (which houses the brake, damping, and measurement mechanisms), and a fixed end (e). The internal and external cross-joints (D and C) share the same center of rotation, the wrist's rotation center. This creates a spherical wrist, decoupling the two degrees of freedom (DOF) and enabling independent measurement and control of roll and pitch angles. Both the internal and external cross-joints (D and C) are hollow structures to increase internal space.

[0020] The braking mechanism, damping mechanism and measuring mechanism installed on the external cross universal joint C realize the functions of braking, measuring and changing the damping characteristics of the wrist lateral swing and pitch motion.

[0021] Although the invention proposes a highly integrated active spherical wrist mechanism and variable stiffness control method for a two-degree-of-freedom robot, which achieves lateral swing and pitch at the output end of the servo mechanism by coaxially connecting the two output ends (driven forks) of concentric inner and outer universal joints, and a radially magnetized NdFeB permanent magnet built into the servo mechanism, guided by the coaxial servo magnetic torque of a spatial universal rotating magnetic field, the following problems exist during implementation: 1) The three-axis nested Helmholtz coils used in the magnetic field generating device are complex and non-compact, and the uniform magnetic field area is too small, which not only directly affects the wrist energy density index but also brings difficulties to the spatial arrangement of the inner and outer universal joint mechanisms. 2) The rotor follower part includes an internal cross-joint and an external cross-joint, both of which adopt a hollow nested structure, resulting in a complex structure and poor rigidity. It is difficult to ensure that the rotation centers of the internal and external cross-joints are the same. If the rotation centers of the two do not coincide, the flexibility of the follower mechanism's rotation will be affected, and even mechanical interference may occur. The internal cross-joint also occupies the space of the rotor permanent magnet, making the spatial arrangement of the permanent magnet difficult. The small size of the permanent magnet also affects the energy output density index of the wrist. 3) It is difficult to simultaneously arrange and install the braking mechanism, damping mechanism, and measuring mechanism on the external cross-joint. Because the external cross-joint adopts a hollow structure, it has insufficient rigidity. Braking with the external cross-joint as the support unit will affect the stability of the follower mechanism's motion control and the positioning accuracy of the wrist. Summary of the Invention

[0022] To address the limitations of the aforementioned electromagnetic wrist, such as complex mechanical structures, uncompact construction, poor rigidity, and difficulty arranging electromechanical components, the present invention provides a highly integrated spherical motor device that utilizes a single external universal joint unit coaxially connected to the output end to form a follower mechanism. This device utilizes internal radially magnetized permanent magnets, directly guided by the coaxial follower magnetic moment of a spatial universal rotating magnetic field, to achieve two-degree-of-freedom motion in roll and pitch. The key improvements to this specific solution are as follows:

[0023] 1) The magnetic field generator utilizes a three-axis orthogonal combination coil, consisting of two sets of saddle coils and one set of Helmholtz coils. This design features a compact structure, a large uniform magnetic field area, a high energy density, and convenient external universal joint layout. 2) The rotor follower portion includes only an external cross universal joint, eliminating the need for an internal cross universal joint. The rotation center of the external cross universal joint serves as the rotation center of the follower mechanism, allowing for flexible rotation without mechanical interference. The lack of an internal cross universal joint allows for ample space within the three-axis orthogonal combination coil for the permanent magnets, significantly increasing the motor's energy output density. 3) The external cross universal joint only requires the installation of damping and measuring mechanisms, simplifying spatial layout. The follower mechanism is locked to the fixed-end frame, and braking using the frame as support significantly increases the stiffness of the follower mechanism, resulting in excellent motion stability and high positioning accuracy.

[0024] This spherical motor can further get rid of the complex mechanical structure and use joint electromagnetic drive to directly realize variable stiffness linear control, which will significantly improve the dynamic performance of the joint's flexible control.

[0025] The technical solution of the present invention is:

[0026] An electromagnetically driven, highly integrated spherical motor comprises a three-axis orthogonal combination coil a and a follower part b. The three-axis orthogonal combination coil a comprises two sets of saddle coils and one set of Helmholtz coils. The three-axis orthogonal combination coil a provides a spatial universal rotating magnetic field, and the follower part b provides a rotating magnetic field with a coaxial follower magnetic torque to drive the two degrees of freedom of yaw and pitch. The specific structure is as follows:

[0027] The follower part b includes an external cross universal joint c, an electromagnetic brake device d, and a fixed end e. The fixed end e includes a base 12 and two vertical support frames f connected to the base 12 at both ends by screws. The support frames f are provided with horizontal through holes for mounting the external cross universal joint c.

[0028] The external cross universal joint c includes an external universal joint inner ring 34, an external universal joint outer ring a22, an external universal joint outer ring b36 and a radially magnetized permanent magnet 3, wherein the external universal joint inner ring 34 serves as a cross-axis bracket, and four horizontal coaxial through holes (cross-axis holes) are symmetrically provided on the external universal joint inner ring 34, and the external universal joint outer rings a22 and b36 serve as driven forks; the flange shaft a6 and the flange shaft b21 are installed in the through holes on the support frame f through the flange bearings a5 and the flange bearings b20. The inner sides of flange shafts a6 and b21 pass through a pair of coaxial through-holes in the outer universal joint inner ring 34 and are bolted to the outer universal joint inner ring 34. The outer side of flange shaft a6 is connected to the shaft of encoder a8 via coupling a7, which is connected to one of the support frames f via encoder connector 9. The outer side of flange shaft b21 is connected to the shaft of damper a18 via coupling b19, which is connected to the other support frame f via damper bracket 17. The other two coaxial through-holes in the outer universal joint inner ring 34 are used to mount deep groove ball bearings a29 and b33, which mate with rotating shafts a28 and b33, respectively. The outer side of rotating shaft a28 mates with outer universal joint outer ring a22 and then with one end of coupling c26. The inner side of rotating shaft a28 mates with circular support a25 and is circumferentially secured with hexagon socket head cap screws. The other end of coupling c26 is connected to the shaft of damper b27, which is fixed to the inner ring 34 of the external universal joint. Damper b27 provides damping during movement, thereby improving the stability of the follower system. Circular support a25 is fixed to the permanent magnet housing 4 and, together with the rotating shaft a28, transmits torque from the radially magnetized permanent magnet 3. The outer side of the rotating shaft b33 first mates with the outer ring b36 of the external universal joint, and then mates with one end of coupling d31. The inner side of the rotating shaft b33 mates with the circular support b30 and is circumferentially positioned using hexagon socket screws. The other end of coupling d29 is connected to the shaft of encoder b30, which is connected to the inner ring 34 of the external universal joint. Circular support b30 is screwed to the permanent magnet housing 4 and, together with the rotating shaft b33, transmits torque. The output end 1 of the external cross joint c is bolted to the external universal joint outer rings a22 and b36. This in turn mates with the output shaft 2. The external universal joint outer rings a22 and b36 support the output end 1, while the output shaft 2 guides it. One end of the output shaft 2 mates with the output end 1, while the other end mates with the circular support c23. The circular support c23 is screwed to the permanent magnet housing end cap 24. The permanent magnet housing end cap 24 mates with the permanent magnet housing 4 and is also screwed together. The permanent magnet housing 4 is hollow, with its top end connected to the permanent magnet housing end cap 24 and its bottom end connected to the friction plate a10.Encoder c16 is installed in the hole inside friction plate a10 to measure the rotation angle of radially magnetized permanent magnet 3. The shaft of encoder c16 is connected to radially magnetized permanent magnet 3 through sleeve 37. Radially magnetized permanent magnet 3 is installed inside permanent magnet housing 4 and can rotate freely.

[0029] The three-axis orthogonal combination coil a comprises an outer saddle coil assembly 39, an inner saddle coil assembly 40, and a Helmholtz coil assembly 41. The inner saddle coil assembly 40 is positioned within the outer saddle coil assembly 39, and the Helmholtz coil assembly 41 is symmetrically arranged on the outer surface of the outer saddle coil assembly 39. The three saddle coils are coaxial, and the bottoms of the outer saddle coil assembly 39 and the inner saddle coil assembly 40 are fixed to the base 12. The saddle coil assembly 39 generates a uniform magnetic field perpendicular to its plane of symmetry and along the y-axis. The saddle coil assembly 40 generates a uniform magnetic field perpendicular to its plane of symmetry and along the x-axis. The Helmholtz coil 41 generates a uniform magnetic field perpendicular to its plane of symmetry and along the z-axis. The z-axis is perpendicular to the x-axis and y-axis, respectively. In other words, the uniform magnetic fields generated by the three coils are perpendicular to each other. The center of the three-axis orthogonal combination coil a coincides with the rotation center of the external cross universal joint c. The radially magnetized permanent magnet 3 is located in the internal space of the three-axis orthogonal combination coil a, and the external cross universal joint c is located outside the three-axis orthogonal combination coil a; the external cross universal joint c, the three-axis orthogonal combination coil a, and the radially magnetized permanent magnet 3 form a three-layer nested structure in space.

[0030] The electromagnetic brake device d is composed of a friction plate a10, a friction plate b11, an electromagnet 15 and a linear guide 14. The linear guide 14 and the electromagnet 15 are both fixed to the base 12. The center of the friction plate b11 is a vertically downward cylindrical structure. The cylindrical end of the friction plate b11 is coaxially mounted with the inner hole of the linear guide 14 and can move relative to each other along the axial direction. The horizontal ends of the friction plate b11 on both sides are symmetrically provided with mounting holes, and the electromagnet 15 is provided with corresponding through holes. After the bolt passes through the mounting holes on the friction plate b11 and the through holes on the electromagnet 15 in sequence, the bottom end is fixed to the base 12. The bolt is sleeved with a spring 42, and the spring 42 is located between the lower surface of the friction plate b11 and the upper surface of the electromagnet (15). When electromagnetic brake device d is de-energized, spring 42 under friction plate b11 pushes it into contact with friction plate a10, generating friction and braking follower part b in both directions. When the brake device is energized, electromagnet 15 generates electromagnetic attraction, pulling friction plate b11 back in. Friction plate a10, connected to permanent magnet housing 4, can continue to move, disengaging from contact with friction plate a10 and releasing the brake on follower part b. A linear guide 14 embedded with balls ensures flexible vertical movement of friction plate b11 and reduces frictional resistance to its movement.

[0031] The base 12 is fixed on the support 13. The support 13 only plays a supporting role. The base 12 is a mechanical interface that can be connected with other components.

[0032] The effects and benefits of the present invention are:

[0033] The rotation center of the external universal joint of this novel electromagnetically driven, two-degree-of-freedom, highly integrated spherical motor is the same as the spherical motor's rotation center. The follower mechanism is compact and simple, offering flexible rotation without mechanical interference. This reliably decouples the motor's two degrees of freedom, allowing for independent measurement and control of roll and pitch angles. The follower mechanism offers excellent motion stability, high positioning accuracy, and robust braking. The magnetic field generator utilizes a three-axis orthogonal combination of coils, resulting in a compact structure and a large uniform magnetic field area.

[0034] Overall, the motor of this invention utilizes a compact, multi-layered, nested structure. The external universal joint and three-axis orthogonal coils are both hollow, significantly increasing the internal volume for nesting permanent magnets and achieving high energy output density. The end effector connected to the motor's output terminal has controllable roll and pitch angles, while maintaining a constant rotation angle. This allows for convenient adjustment of the end effector's normal orientation for positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the existing robot wrist structure.

[0036] Figure 2 It is a schematic diagram of the existing robot wrist rotor follower part.

[0037] Figure 3 It is a schematic diagram of the structure of the spherical motor of the present invention.

[0038] Figure 4 It is a schematic diagram of the rotor follower part of the spherical motor of the present invention.

[0039] FIG5(A) is a schematic cross-sectional view of the pitch transmission mechanism of the spherical motor of the present invention.

[0040] FIG5(B) is a cross-sectional view of the spherical motor transmission mechanism of the present invention Figure I Partial enlargement

[0041] FIG5(C) is a cross-sectional view of the pitch transmission mechanism of the spherical motor of the present invention Figure II A partial enlarged view.

[0042] FIG5(D) is a cross-sectional schematic diagram of the spherical motor side-sway transmission mechanism of the present invention.

[0043] FIG5(E) is a cross-sectional view of the spherical motor side swing transmission mechanism of the present invention. Figure III A partial enlarged view.

[0044] FIG5(F) is a cross-sectional view of the spherical motor side swing transmission mechanism of the present invention Figure IV A partial enlarged view.

[0045] FIG5(G) is a partial enlarged view of point V of the cross-sectional schematic diagram of the spherical motor side-sway transmission mechanism of the present invention.

[0046] Figure 6 This is a schematic diagram of the disassembly and overall assembly of the three-axis orthogonal combination coils of the spherical motor of the present invention.

[0047] FIG7(A) is a schematic diagram of a damper connecting frame.

[0048] Figure 7(B) is a schematic diagram of the encoder connecting frame.

[0049] In the figure: A three-axis Helmholtz coil group; D internal cross universal joint; a three-axis orthogonal combination coil; b follower part; c external cross universal joint; d electromagnetic brake device; e fixed end; f support frame.

[0050] 1 Output end; 2 Output shaft; 3 Radially magnetized permanent magnet; 4 Permanent magnet housing; 5 Flange bearing a; 6 Flange shaft a; 7 Coupling a; 8 Encoder a; 9 Encoder bracket; 10 Friction plate a; 11 Friction plate b; 12 Base; 13 Support; 14 Linear guide; 15 Electromagnet; 16 Encoder c; 17 Damper bracket; 18 Damper a; 19 Coupling b; 20 Flange bearing b; 21 Flange shaft b; 22 External universal joint outer ring a; 23 Circular support c; 24 Permanent magnet end cover; 25 Circular support a; 26 Coupling c; 27 Damper b; 28 Rotating shaft a; 29 Deep groove ball bearing a; 30 Circular support b; 31 Coupling d; 32 Encoder b; 33 Rotating shaft b; 34 External universal joint inner ring; 35 Deep groove ball bearing b; 36 External universal joint outer ring b; 37 Bushing; 38 Slip angle bracket; 39 External saddle coil group; 40 Inner saddle coil group; 41 Helmholtz coil group; 42 Spring; 43 Thin-walled bearing. DETAILED DESCRIPTION

[0051] The specific embodiments of the present invention are described in detail below in conjunction with the technical solutions and drawings.

[0052] like Figure 3 As shown, the two-degree-of-freedom spherical motor of the present invention comprises a three-axis orthogonal combination coil a and a follower part b. The three-axis orthogonal combination coil a provides a universal rotating magnetic field, while the follower part b provides a coaxial follower magnetic moment of the rotating magnetic field to drive the two degrees of freedom of yaw and pitch. The operating principle utilizes the coaxial follower magnetic moment effect of the universal rotating magnetic field.

[0053] Combine Figure 4 、 5(A) 5(G) illustrates the structure of the follower part b of the novel electromagnetically driven two-degree-of-freedom spherical motor of the present invention.

[0054] The follower part (b) consists of an external cross-joint (c) (which houses a radially magnetized permanent magnet (3), dampers a18 and b27 as the damping mechanism, and encoders a8 and b32 as the measuring mechanism), an electromagnetic brake (d), and a fixed end (e). The rotational center of the two axes of the external universal joint's inner ring (34) is the same, i.e., the motor's rotational center. This forms a spherical motor, decoupling the two degrees of freedom (DOF) and enabling independent measurement and control of the roll and pitch angles. The location of the external universal joint's inner ring (34) between the Helmholtz coils makes the overall structure more compact.

[0055] The axis b of the follower part is the rotation axis of the motor. The axis b of the follower part can realize the rotational motion of the two degrees of freedom of roll and pitch (the center of rotation of the motor). The radially magnetized permanent magnet 3 is installed in the follower part b and can rotate freely with the rotating magnetic field. The coaxial follower magnetic moment of the external rotating magnetic field is used as the power medium to drive and realize the roll and pitch steering motion of the motor.

[0056] The output end 1 of the external cross universal joint c can be connected to the end effector, whose posture is determined by the roll and pitch angles of the follower part b axis. Since the end effector is connected to the output end 1 of the external cross universal joint c, the end effector rotation angle does not deflect, and the normal direction of the motor end effector can be easily adjusted to complete the motor positioning.

[0057] See Figures 5(A) to 5(C) The support frame f and the outer universal joint inner ring 34 can achieve relative rotation. The assembly process of the flange shaft a6 and the flange shaft b21 is: the flange shaft a6 is fixedly connected to the outer universal joint inner ring 34 by bolts, and is connected to one of the support frames f through the flange bearing a5, and the shaft end is fixedly connected to the coupling a7; the flange shaft b21 is fixedly connected to the outer universal joint inner ring 34 by bolts, and is connected to the other support frame f through the flange bearing b20, and the shaft end is fixedly connected to the coupling b19.

[0058] As shown in Figures 5(D), (E), and (G), the permanent magnet housing 4 and the outer universal joint inner ring 34 can achieve relative rotation. The assembly process of the rotating shaft a28 and the rotating shaft b33 is as follows: the rotating shaft a28 is first connected to the outer universal joint inner ring 34 through the deep groove ball bearing a29, and its inner shaft end is matched with the circular support a25 and circumferentially positioned with a hexagon socket screw. The outer side of the rotating shaft a28 is first matched with the outer universal joint outer ring a22, and the shaft end is then matched with the coupling c26. The other end of the coupling c26 is connected to the shaft of the damper b27, and the damper b27 is fixed to the universal joint inner ring 34 through the damper connecting frame (see Figure 7(A)). The rotating shaft b33 is first connected to the inner ring 34 of the universal joint through the deep groove ball bearing b33. The inner shaft end cooperates with the circular support b30 and is circumferentially positioned with a hexagon socket screw. Its outer side first cooperates with the outer ring b36 of the external universal joint and then connects to one end of the coupling d31.

[0059] As shown in Figure 5(F), the encoder c16 rotates synchronously with the radially magnetized permanent magnet 3. The assembly process is as follows: the bottom of the encoder c16 fits into the hole in the friction plate a10, and then is connected to the slip angle bracket 38, which is fixed to the friction plate a10; the shaft of the encoder c16 fits into the hole of the sleeve 35 and is circumferentially positioned with screws, and finally the sleeve 37 is connected to the radially magnetized permanent magnet 3.

[0060] See Figure 6 The three-axis orthogonal combination coil a includes an outer saddle coil group 39, an inner saddle coil group 40 and a Helmholtz coil group 41, which are arranged symmetrically; the magnetic field directions of the three coil groups are perpendicular to each other, and the three coil groups are fixed to each other, and the outer saddle coil group 39 and the inner saddle coil group 40 are fixed on the base 12.

[0061] The follower portion b, constructed through an external cross universal joint c and an electromagnetic brake device d, features a characteristic: the center of rotation of the outer universal joint inner ring 34 is the motor's center of rotation, thus forming a spherical motor. This decouples the two degrees of freedom of rotation, enabling independent measurement and control of the roll and pitch angles. The coaxial connection between the outer universal joint inner ring 34 and the permanent magnet housing 4 is as follows: circular supports a25 and b30 are respectively fixed to the permanent magnet housing 4, and circular supports a25 and b30 are respectively connected to the rotation axis a28 and the rotation axis b33. The radially magnetized permanent magnet 3 is mounted within the permanent magnet housing 4 via a thin-walled bearing 43, enabling coaxial rotation relative to the follower portion b.

[0062] The detection and control method of the motor output terminal posture is as follows:

[0063] The follower part b has only one fixed point (the motor's center of rotation), and the position of the follower part b's axis must be controlled. Specifically, the motor axis's position is controlled by detecting and controlling the relative motion of the outer universal joint inner ring 34. The outer universal joint inner ring 34 is connected by support frame f, rotating shaft a28, and rotating shaft b33, which move relative to each other to achieve universal rotation of the motor axis. Because the outer universal joint inner ring 34 is a monolithic annular structure with four holes (cross-shaft holes) evenly distributed around its circumference, it can be connected as follows:

[0064] Encoder bracket 9 is mounted on support frame f. Encoder a8 is mounted on encoder bracket 9 and connected to flange shaft a6 via coupling a7. Encoder a8 measures the relative angle between the outer gimbal inner ring 34 and support frame f, which is the motor pitch angle. An encoder connector (see Figure 7(B)) is mounted on the other axis of outer gimbal inner ring 34. Encoder b32 is mounted on the encoder connector (see Figure 7(B)) and connected to rotating shaft b33 via coupling d31. Encoder b32 measures the relative angle between gimbal inner ring 34 and rotating shaft b33, which is the motor output roll angle. The absolute encoder b32 mounted on the rotating axis of outer gimbal inner ring 34 and the absolute encoder a8 mounted on the rotating axis of support frame f enable real-time measurement of roll and pitch angles, which are transmitted to the control system for accurate control of these angles.

[0065] The electromagnetic brake device d locks the motor's two degrees of freedom, pitch and roll. When the motor is stationary, the electromagnetic brake device d locks the external cross universal joint c to fix the position of the follower part b and prevent it from swinging randomly and causing accidents. When the motor rotates, the electromagnetic brake device d releases the lock on the external cross universal joint c to achieve the following of the follower part b and the universal rotating magnetic field, that is, to achieve the drive of roll and pitch rotation.

[0066] Damper a18 and damper b27 are respectively installed at the outer end of the support frame f and the rotation axis joint of the inner ring 34 of the external universal joint (roll axis), providing damping for the pitch and roll rotation of the motor, so as to reduce the vibration of the motor output end during the roll and pitch attitude adjustment process and maintain the stability of the working process.

[0067] Combine Figure 3 、 4 Describe the working process of the new electromagnetically driven two-degree-of-freedom spherical motor.

[0068] The posture zero point calibration process before operation is as follows: a spatial universal rotating magnetic field with a vertical rotation axis is generated by a three-axis orthogonal combination coil a. Under the drive of the coaxial follower magnetic torque, the two axes of the outer universal joint inner ring 34 of the follower part b are both in a horizontal position. At this time, the relative rotation angles of encoder a8 for the pitch angle and encoder b26 for the roll angle are zero. Then, encoder a8 and encoder b26 are powered on respectively to store and memorize the zero point position of the two-degree-of-freedom motor; when the two-degree-of-freedom motor is positioned, the roll and pitch are driven to put the two-degree-of-freedom motor in active working mode, and the external coaxial follower magnetic torque control system is used with encoder a8 and encoder b26 to form a closed-loop control of the angular position. The control accuracy is improved by real-time sensing and memorizing the roll and pitch positions of the two-degree-of-freedom motor.

[0069] The working process is:

[0070] In the first step, before power is turned on, the electromagnetic brake device d has been locking the follower part b, making it unable to perform side swing and pitch movements.

[0071] The second step is to determine the direction of the rotation axis of the space universal rotating magnetic field to be applied according to the target spatial orientation, and to pass three sets of equal-frequency alternating currents into the three-axis orthogonal combination coil a to generate a space rotating magnetic field in the corresponding orientation.

[0072] In the third step, the radially magnetized permanent magnet 3 starts to rotate under the action of the rotating magnetic field and generates a coaxial follower magnetic moment. However, due to the locking of the follower part b by the electromagnetic brake device d, the follower part b cannot perform side swing and pitch motion.

[0073] In the fourth step, the electromagnetic brake device d is energized to release the lock on the follower part b. Under the action of the coaxial follower magnetic moment of the rotating magnetic field, the radially magnetized permanent magnet 3 causes the follower part b's axis to follow the axis of the rotating magnetic field to perform side and pitch motions. The pitch angle is measured by encoder a8, and the side and side deflection angle is measured by encoder b26. The movement process is damped by dampers a18 and b27 to reduce possible vibrations.

[0074] The fifth step is to provide real-time feedback of pitch and roll angle information through encoder a8 and encoder b26; based on the feedback angle information, the coaxial follower magnetic torque is feedback controlled until the accuracy is met and the motor reaches the target position, realizing the control of two-degree-of-freedom motion.

[0075] In the sixth step, the three-axis orthogonal combination coil a is de-energized, the electromagnetic brake device d is de-energized, and the follower part b is locked again to fix the motor position.

Claims

1. An electromagnetically driven highly integrated spherical motor, characterized in that: The electromagnetically driven highly integrated spherical motor comprises a three-axis orthogonal combination coil (a) and a follower part (b); wherein the three-axis orthogonal combination coil (a) provides a spatial universal rotating magnetic field, and the follower part (b) provides a rotating magnetic field coaxial with the follower magnetic torque to drive the two degrees of freedom of lateral swing and pitch. The specific structure of the electromagnetically driven two-degree-of-freedom spherical highly integrated motor is as follows: The following part (b) includes an external cross universal joint (c), an electromagnetic brake device (d), and a fixed end (e); the fixed end (e) includes a base (12) and two vertical support frames (f) connected to the two ends of the base (12) by screws; the support frames (f) are provided with horizontal through holes for mounting the external cross universal joint (c); The external cross universal joint (c) comprises an external universal joint inner ring (34), an external universal joint outer ring a (22), an external universal joint outer ring b (36) and a radially magnetized permanent magnet (3), wherein the external universal joint inner ring (34) serves as a cross shaft bracket, four horizontal coaxial through holes are symmetrically provided on the external universal joint inner ring (34), and the external universal joint outer ring a (22) and the external universal joint outer ring b (36) serve as driven forks; the flange shaft a (6) and the flange shaft b (21) are respectively installed in the through holes on the two support frames (f) through the flange bearing a (5) and the flange bearing b (20); the inner sides of the flange shaft a (6) and the flange shaft b (21) pass through a pair of coaxial through holes of the external universal joint inner ring (34) and are connected to the external universal joint inner ring (34) by bolts. The outer side of the flange shaft a (6) is connected to the shaft of the encoder a (8) through the coupling a (7), and the encoder a (8) is connected to one of the support frames (f) through the encoder bracket (9); the outer side of the flange shaft b (21) is connected to the shaft of the damper a (18) through the coupling b (19), and the damper a (18) is connected to the other support frame (f) through the damper bracket (17); the other two through holes on the outer universal joint inner ring (34) are used to install deep groove ball bearings a (29) and deep groove ball bearings b (33), and the deep groove ball bearings a (29) and deep groove ball bearings b (33) are matched with the rotating shaft a (28) and the rotating shaft b (33) respectively; the outer side of the rotating shaft a (28) is first connected to the outer side of the rotating shaft a (28) The outer ring a (22) of the external universal joint is matched with one end of the coupling c (26), and the inner side of the rotating shaft a (28) is matched with the circular support a (25) and is circumferentially positioned by a hexagon socket screw; the other end of the coupling c (26) is connected to the shaft of the damper b (27), and the damper b (27) is fixed to the inner ring (34) of the external universal joint through the damper connecting frame, which plays the role of providing damping in the motion circle; the circular support a (25) is fixed to the permanent magnet housing (4), and transmits the torque from the radially magnetized permanent magnet (3) together with the rotating shaft a (28); the outer side of the rotating shaft b (33) is first matched with the outer ring b (36) of the external universal joint, and then matched with one end of the coupling d (31), and the inner side of the rotating shaft b (33) is matched with the outer ring b (36) of the external universal joint, and then matched with one end of the coupling d (31). The outer ring a (22) and the outer ring b (36) of the outer cross universal joint (c) are connected to each other through bolts, and the ... cross universal joint (c) are connected to each other through bolts, and the outer cross universal joint (c) are connected to the output shaft (2), wherein the outer cross universal joint (c) and the outer ring b (36) of the outer cross universal joint (c) support the output end (1), and the output shaft (2) guides the output end (1).One end of the output shaft (2) is matched with the output end (1), and the other end is matched with the circular support c (23), and the circular support c (23) is connected to the permanent magnet housing end cover (24) by screws; the permanent magnet housing end cover (24) is matched with the permanent magnet housing (4) and connected by screws; the permanent magnet housing (4) is a hollow structure, the top end is connected to the permanent magnet housing end cover (24), and the bottom end is connected to the friction plate a (10); the encoder c (16) is installed in the hole inside the friction plate a (10) and is used to measure the rotation angle of the radially magnetized permanent magnet (3), and the shaft of the encoder c (16) is connected to the radially magnetized permanent magnet (3) through the shaft sleeve (37); the radially magnetized permanent magnet (3) is located in the permanent magnet housing (4) and can rotate freely; The three-axis orthogonal combination coil (a) comprises an outer saddle coil group (39), an inner saddle coil group (40) and a Helmholtz coil group (41), wherein the inner saddle coil group (40) is placed inside the outer saddle coil group (39), and the Helmholtz coil group (41) is symmetrically arranged on the outer surface of the outer saddle coil group (39). The three are coaxial, and the bottoms of the outer saddle coil group (39) and the inner saddle coil group (40) are fixed on the base (12); the direction of the uniform magnetic field generated by the saddle coil group (39) is perpendicular to its symmetry plane and along the y-axis, and the direction of the uniform magnetic field generated by the saddle coil group (40) is perpendicular to its symmetry plane and along the y-axis. The symmetry plane is perpendicular and along the x-axis; the direction of the uniform magnetic field generated by the Helmholtz coil (41) is perpendicular to its symmetry plane and along the z-axis; the directions of the uniform magnetic fields generated by the three groups of coils are perpendicular to each other; the center of the three-axis orthogonal combination coil (a) coincides with the rotation center of the external cross universal joint (c); the radially magnetized permanent magnet (3) is located in the internal space of the three-axis orthogonal combination coil (a), and the external cross universal joint (c) is located outside the three-axis orthogonal combination coil (a); the external cross universal joint (c), the three-axis orthogonal combination coil (a), and the radially magnetized permanent magnet (3) form a three-layer nested structure in space; The electromagnetic brake device (d) is composed of a friction plate a (10), a friction plate b (11), an electromagnet (15) and a linear guide rail (14); the linear guide rail (14) and the electromagnet (15) are both fixed on the base (12); the center of the friction plate b (11) is a vertically downward cylindrical structure, the cylindrical end of the friction plate b (11) is coaxially installed with the inner hole of the linear guide rail (14) and can move relative to each other along the axial direction, the horizontal ends of both sides of the friction plate b (11) are symmetrically provided with mounting holes, and the electromagnet (15) is provided with corresponding through holes, and the bolts are successively passed through the mounting holes on the friction plate b (11) and the through holes on the electromagnet (15), and the bottom ends are fixed to the base (1 2), a spring (42) is sleeved on the bolt, and the spring (42) is located between the lower surface of the friction plate b (11) and the upper surface of the electromagnet (15); when the electromagnetic brake device (d) is powered off, the elastic force of the spring (42) under the friction plate b (11) pushes the friction plate a (10) and the friction plate b (11) into contact, generating friction force, thereby achieving braking of the follower part (b) in two directions; when the electromagnetic brake device (d) is powered on, the electromagnet (15) generates electromagnetic suction force to suck the friction plate b (11) back, and the friction plate a (10) connected to the permanent magnet housing (4) continues to move, disengages from the friction plate a (10) and releases the braking of the follower part (b); The base (12) is fixed on the support (13), and the support (13) only plays a supporting role. The base (12) can also be docked with other components.

2. The control method of the electromagnetically driven highly integrated spherical motor according to claim 1, characterized in that: The specific control process is as follows: (1) The posture zero point calibration process before operation is as follows: a space universal rotating magnetic field with a vertical rotation axis is generated by a three-axis orthogonal combination coil (a), and under the drive of the coaxial follower magnetic moment, the two axes of the outer universal joint inner ring (34) of the follower part (b) are both in a horizontal position. At this time, the relative rotation angles of the encoder a (8) of the pitch angle and the encoder b (26) of the roll angle are zero, and then the encoder a (8) and the encoder b (26) are powered on respectively, while storing and memorizing the zero point position of the two-degree-of-freedom motor; when the two-degree-of-freedom motor is positioned, the roll and pitch are driven to put the two-degree-of-freedom motor in working mode, and the angular position closed-loop control is formed according to the external coaxial follower magnetic moment control system and the encoder a (8) and the encoder b (26), and the roll and pitch positions of the two-degree-of-freedom motor are sensed and memorized in real time; (2) The working process is: In the first step, before power is applied, the electromagnetic brake device (d) always locks the follower part (b), preventing it from rolling or pitching. The second step is to determine the direction of the rotation axis of the universal rotating magnetic field according to the target spatial orientation, and to pass three sets of equal-frequency alternating currents into the three-axis orthogonal combination coil (a) to generate a spatial rotating magnetic field in the corresponding orientation; In the third step, the radially magnetized permanent magnet (3) begins to rotate under the action of the rotating magnetic field, generating a coaxial follower magnetic moment. However, due to the locking of the follower part (b) by the electromagnetic brake device (d), the follower part (b) cannot perform side swing and pitch motion. In the fourth step, the electromagnetic brake device (d) is energized to release the lock on the follower part (b). Under the action of the coaxial follower magnetic moment of the rotating magnetic field, the radially magnetized permanent magnet (3) causes the follower part (b) to follow the axis of the rotating magnetic field to perform side swing and pitch motion. The pitch angle is measured by encoder a (8), and the side swing angle is measured by encoder b (26). The motion process is damped by damper a (18) and damper b (27) to reduce possible vibration. The fifth step is to feedback the pitch and roll angle information in real time through encoder a (8) and encoder b (26); according to the feedback angle information, the coaxial follower magnetic moment is feedback controlled until the accuracy is met and the motor reaches the target position, thus realizing the control of two-degree-of-freedom motion; In the sixth step, the three-axis orthogonal combination coil (a) is de-energized, the electromagnetic brake device (d) is de-energized, and the follower part (b) is locked again to fix the motor position.

Images