WO2021243515A1 - 一种电磁驱动两自由度球型机器人手腕及其控制方法 - Google Patents

一种电磁驱动两自由度球型机器人手腕及其控制方法 Download PDF

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Publication number
WO2021243515A1
WO2021243515A1 PCT/CN2020/093737 CN2020093737W WO2021243515A1 WO 2021243515 A1 WO2021243515 A1 WO 2021243515A1 CN 2020093737 W CN2020093737 W CN 2020093737W WO 2021243515 A1 WO2021243515 A1 WO 2021243515A1
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Prior art keywords
universal joint
wrist
axis
magnetic field
coaxial
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PCT/CN2020/093737
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English (en)
French (fr)
Inventor
张永顺
王殿龙
杨振强
贾鹏志
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大连理工大学
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Priority to PCT/CN2020/093737 priority Critical patent/WO2021243515A1/zh
Priority to US17/286,780 priority patent/US11446814B2/en
Publication of WO2021243515A1 publication Critical patent/WO2021243515A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/10—Programme-controlled manipulators characterised by positioning means for manipulator elements
    • B25J9/12—Programme-controlled manipulators characterised by positioning means for manipulator elements electric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J17/00—Joints
    • B25J17/02—Wrist joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J17/00—Joints
    • B25J17/02—Wrist joints
    • B25J17/0258—Two-dimensional joints
    • B25J17/0275—Universal joints, e.g. Hooke, Cardan, ball joints

Definitions

  • the invention belongs to the technical field of automation engineering, and relates to an electromagnetically driven two-degree-of-freedom spherical robot wrist and a control method thereof, and specifically relates to two output ends (driven forks) of the inner and outer universal joints passing through the same rotation center.
  • the follow-up mechanism formed by the shaft connection has a built-in radial magnetized permanent magnet that is directly driven by the coaxial follow-up magnetic moment of the space universal rotating magnetic field to realize the rotation of side and pitch two degrees of freedom of the robot, which is a highly integrated active spherical wrist device for the robot.
  • Robots used in dangerous and extreme environments have strict requirements on the performance indicators of the wrist.
  • the distinguishing characteristics of space robots are compact structure, high degree of integration, and large power-to-weight ratio.
  • Space robots are playing an increasingly important role in the maintenance of spacecraft and space stations.
  • the control of spacecraft and the opening of hatches, the assembly of space modules, and the maintenance of spacecraft can all be completed in place of astronauts.
  • the wrist is an important basic component connecting the arm and the hand, and its performance directly affects the positioning accuracy, flexibility and operating functions of the robot end effector.
  • the function of the robot wrist is to change the posture of the end effector in space through small local adjustments to achieve accurate positioning.
  • the degree of freedom and posture range of the wrist directly affect the flexibility, stability and positioning accuracy of the robot, and any position and posture of the robot
  • the control requires six degrees of freedom, and the wrist should have at least two degrees of freedom.
  • the wrist is located at the front end of the arm.
  • the weight of the wrist constitutes the additional load of the forearm and increases energy consumption.
  • the wrist realizes two-axis rotation in a small space. Therefore, the mechanical design of the wrist is complicated and there are many variable parameters.
  • the performance index of the wrist has become the main bottleneck restricting the application and expansion of the robot in extreme environments such as space.
  • the transmission of multi-degree-of-freedom motion generally adopts gear transmission.
  • the structure is complex, the integration is low, and there are kinematic coupling problems, which make the end effector flexibility, posture adjustment ability and accuracy.
  • the positioning ability is limited, and it is not yet possible to complete complex contact operations such as opening the spacecraft door through the adjustment of the wrist.
  • robot wrists can basically be divided into three categories: 1) Spherical wrist, its three joint axes intersect at one point, its position and posture are decoupled, the inverse kinematics analysis is simple, the structure is compact, and the work is heavy. The ratio is large, so most robots used in special occasions such as space robots use spherical wrists. Due to the limitation of the mechanical structure, this kind of wrist design is difficult, the structure is complex, the weight is difficult to reduce, and the working space is small; 2) Aspherical wrist, its three axes do not intersect at one point, which overcomes the limitations of the mechanical structure.
  • the rotation angle of each joint can reach more than 360°, but its disadvantage is that the structure is not compact, the volume is large, which limits the improvement of the power-to-weight ratio index, the movement cannot be decoupled, and the control accuracy is low; 3) Parallel structure wrist, this type The structure of the wrist is actually a miniaturized parallel mechanism.
  • the motor layout adopts pitch, roll and rotation separation methods, but its structure is not compact and its power is heavy. The ratio is small, the motion of the three joints is not decoupled, and the control accuracy is low.
  • NASA has developed a new generation of wrist module.
  • the transmission system uses three parallel screw drives to achieve side roll and pitch, which simplifies the design and reduces the cost. Because of its additional flexibility, it is suitable for unstructured environments.
  • NASA jet thrust experiment The laboratory has successfully used the universal wrist to handle dangerous items. However, the disadvantage of this wrist is that it requires three drives to achieve two movements of side swing and pitch.
  • robot operations can be divided into two categories: non-contact and contact: the former is for the robot to move in free space without being restricted by the external environment. It is only necessary to adopt pure position control, and the robot position control is only suitable for structured construction. Work in the mold environment; the latter is constrained by the external environment, such as space robots opening doors, assembling, rotating cranks and other tasks. Work robots such as grasping, installation, and positioning in an unmodeled environment have obvious contact operation characteristics, and their wrists should have a variable stiffness compliant control function to avoid damage to the robotic arm during contact operations.
  • active compliance control there are two main types of compliance control: active and passive.
  • active compliance control The way that the robot actively controls the force by processing the force feedback information and adopting a certain control strategy is called active compliance control.
  • passive compliance control the way that the robot does not use force feedback but just relies on the compliant mechanism such as machinery to make it naturally compliant with the environment is called passive compliance control.
  • Active compliance control is divided into active impedance control and force/position hybrid control.
  • the force/position hybrid control method is highly dependent on the dynamics of the external environment and requires a detailed task description.
  • the research of passive compliance control is mainly realized through the mechanical device itself or specially designed passive compliance mechanism, such as the RCC elastic attachment of the robot wrist.
  • the disadvantage is that additional mechanical devices need to be added, which makes the wrist mechanism complex and heavy, and has poor adaptability. .
  • South Korea proposed a spherical two-degree-of-freedom active-driving robot wrist joint and active compliance control method. Its lower hemisphere movement is realized by gear transmission, and the upper hemisphere is transmitted through the internal universal joint. The two offset slopes are compounded into the wrist's lateral swing and pitch movement.
  • the structure is compact and simple, and it realizes two input movements. Decoupling, and controlling the transmission torque through the degree of clutch engagement, so that the wrist becomes a passive wrist under a certain torque, which plays the role of overload protection and avoiding mechanical interference to damage the wrist joints.
  • Dalian University of Technology proposed a three-degree-of-freedom constant velocity decoupling space robot active spherical wrist and universal compliance control method (patent number: ZL201310282753.1), which is a typical active compliance control method, specifically through friction compensation It can realize the functions of active and passive wrists.
  • the passive mode the spherical wrist is in a fully compliant state to avoid damage to the mechanical arm during contact operations.
  • the friction compensation accuracy will directly affect the compliance control effect, and the control process of the three-axis rotation of the wrist is complicated.
  • the friction of the motion transmission system has nonlinear characteristics, which ultimately leads to problems such as poor dynamic performance of the mechanical structure of the wrist, low control accuracy, low mechanical efficiency, and poor reliability.
  • the complex transmission structure of the mechanical wrist and the realization of active compliance control, which leads to the difficulty of compliance control and low response speed.
  • the traditional mechanical wrist reducer system has the output end reverse transmission self-locking characteristic, when contacting work, the active control torque must be applied to eliminate the joint friction in order to release the self-locking and realize the compliance control.
  • the friction of the joint reducer system It manifests as complex nonlinearity, which leads to poor compliance control of mechanical joints and easily damages the mechanical arm.
  • the electromagnetic direct-drive multi-degree-of-freedom motor can be used to replace the complex transmission mechanical wrist .
  • the multi-degree-of-freedom motor has high integration, simple transmission chain and no mechanical gap, high utilization of effective materials and control system components, especially the high degree of freedom of rotation, which can significantly simplify the structure of the mechanical system and avoid the nonlinear friction of the joints. Improve the static and dynamic performance of the system.
  • the spherical motor is a high technology that integrates modern motor design theory, power electronic technology, and automatic control theory.
  • the spherical motor itself is a directly driven spherical active joint. According to the principle, it can be divided into the following categories: self-aligning machine type, induction type, permanent magnet type (including direct current, stepping, reluctance type, synchronous type), etc. It overcomes many shortcomings of the coiled spherical motor.
  • the permanent magnet spherical motor occupies a small space, has high system efficiency and high magnetic energy product. It has good application prospects in the field of multi-dimensional space servo control systems such as robots, multi-directional transmission mechanisms, and manufacturing.
  • electromagnetic spherical motors generally have the following problems in the body structure design, electromagnetic and torque analysis and control: 1) The magnetic field calculation is difficult. The magnetic field of the spherical motor is a three-dimensional magnetic field, which is extremely complicated. At present, the calculation of the magnetic field of the spherical motor is based on an idealized hypothetical model, and the magnetic field cannot be accurately modeled and calculated. 2) The problem of electromagnetic coupling. Spherical motors have complicated electromagnetic coupling and mechanical coupling. How to quantitatively analyze these coupling relationships based on the magnetic field model to achieve precise decoupling is an urgent problem in the design and precise control of spherical motors. 3) Optimization of the structural parameters of the new spherical motor. Based on the accurate modeling of the spherical motor, the goal of improving its output torque, reducing the size, improving the response sensitivity and positioning accuracy, and optimizing the structural parameters of the spherical motor must be carried out.
  • the new spherical motor must facilitate the establishment of an accurate mechanical model and motion model, find a suitable path planning algorithm, and improve the dynamic performance and stability of the motor. It is the basis for precise control of the spherical motor, and it is also the application of the spherical motor in the field of precision industry. Inevitable requirement.
  • the space universal rotating magnetic field is a single uniform rotating magnetic field generated by a three-axis orthogonal Helmholtz coil, there is no magnetic field coupling problem, and there is no magnetic coupling problem.
  • the magnetic poles are only affected by pure electromagnetic driving torque, which is convenient for establishing accurate mechanics. Model and motion model, therefore, the advantages of using the space universal rotating magnetic field technology are obvious.
  • the control of the orientation of the rotating magnetic field and the direction of rotation is the key.
  • ⁇ and ⁇ are the side swing and pitch angles of the robot axis
  • I 0 is the amplitude of the sinusoidal current in the three orthogonal Helmholtz coils
  • ⁇ is the angular frequency of the sinusoidal signal current
  • the drive of the three-axis orthogonal Helmholtz coil is a space universal rotating magnetic field control mode that generates the azimuth of the robot axis's roll angle and pitch angle with separable variables, which can completely realize the new type of wrist roll angle and pitch angle control.
  • the axis of the radial magnetized NdFeB permanent magnet cylinder driven by the universal rotating magnetic field will have the coaxial follower magnetic moment effect of the rotating magnetic field, that is, when the axis of the NdFeB cylinder rotates
  • the coaxial follower magnetic moment of the rotating magnetic field will pull the neodymium iron boron cylinder axis to rotate in the direction of the rotating magnetic field rotation axis until it overlaps.
  • the coaxial follow-up magnetic moment of the space universal rotating magnetic field can guide the axis of the permanent magnet to any position in space, which lays the foundation for the electromagnetic drive of the ball joint attitude conversion.
  • variable stiffness flexible joints are divided into two types of models: lever mechanism and cam mechanism according to the structural principle.
  • the German Aerospace Center Robotics and Mechatronics Association has developed a cam mechanism-based variable stiffness joint VS.Joint, which uses the rotation of the joint to drive the position of the cam roller in the bottom cam disc to change the compression of the spring to achieve the joint Variable stiffness flexible output; its second-generation variable stiffness flexible joint (FSJ) is used in the new DLR arm system.
  • FSJ second-generation variable stiffness flexible joint
  • variable stiffness driver CompAct-VSA developed by the Italian Institute of Technology TSAGARAKIS, etc., uses rack and pinion transmission to change the position of the rotation axis of the cam-shaped lever arm.
  • the cam acts through a roller and a spring to change the output stiffness of the mechanism.
  • the mechanical variable stiffness adjustment mechanism is large in size, complex in structure, and poor in practical application. If it can get rid of the complex mechanical structure and use the joint electromagnetic drive to directly realize the linear control of the variable stiffness, the dynamic performance of the joint compliance control will be improved. Significantly increased.
  • the present invention proposes a method of concentric inner and outer
  • the two output ends (driven forks) of the universal joint are coaxially connected to form the follow-up mechanism.
  • Built-in radial magnetized neodymium iron boron permanent magnets realize the output side of the follow-up mechanism under the guidance of the coaxial follow-up magnetic moment of the space universal rotating magnetic field.
  • the swing and pitch two-degree-of-freedom robot highly integrated active spherical wrist mechanism and variable stiffness control method.
  • the present invention provides a built-in radial magnetized permanent magnet driver of a follower mechanism formed by coaxial connection of two output ends (driven forks) of concentric inner and outer universal joints in a space universal rotating magnetic field.
  • a feedforward control method through electromagnetic direct drive is also provided to realize the spherical wrist under contact operation conditions.
  • the variable stiffness and compliance control method is also provided to realize the spherical wrist under contact operation conditions.
  • An electromagnetically driven two-degree-of-freedom spherical robot wrist includes a three-axis Helmholtz coil group a and a rotor follow-up part b; wherein the three-axis orthogonal Helmholtz coil group a provides a space universal rotating magnetic field, The follower part b of the rotor provides the coaxial follower magnetic moment of the rotating magnetic field to drive the two degrees of freedom rotation of the lower side swing and pitch; the specific structure is as follows:
  • the rotor follow-up part b includes an inner cross universal joint d, an outer cross universal joint c, and a fixed end e; the top of the fixed end e is the fixed end support seat 5, and the fixed end support seat 5 is divided into four parts located in the same
  • the vertical support frame of the axis, the support frame is provided with a horizontal through hole, the two vertical support frames in the middle are used to install the internal cross universal joint d, and the two vertical support frames at the outer end are used to install the external cross universal joint.
  • Section c
  • the internal cross universal joint d includes two vertical support frames (active forks) in the middle of the fixed end supporting seat 5, an internal universal joint inner ring 14 and a cylindrical shell 2, wherein the inner universal joint inner ring 14 As a cross shaft bracket, the cylindrical housing 2 acts as a driven fork; the two sides of the inner universal joint inner ring 14 are respectively mounted on the two middle two sides of the fixed end support seat 5 through deep groove ball bearings a15 and deep groove ball bearings b16.
  • the fixed end supporting seat 5 and the inner universal joint inner ring 14 realize relative rotation to form a pitch rotation axis;
  • the cylindrical shell 2 is located in the inner universal joint inner ring 14, and the connecting shaft d23
  • One end of the connecting shaft e26 and the connecting shaft e26 are symmetrically fixed on both sides of the cylindrical shell 2, and the other end is installed on the inner side of the inner universal joint ring 14 through the deep groove ball bearing c24 and the deep groove ball bearing d25 to realize the cylindrical shell 2
  • the radially magnetized permanent magnet 1 is installed in the cylindrical housing 2 through the bearing 31;
  • the external cross universal joint c includes two vertical support brackets (active forks) at the outer end of the fixed end support base 5, an outer universal joint inner ring 3 and an outer universal joint outer ring 17, wherein the outer universal joint
  • the inner ring 3 is used as a cross shaft support
  • the outer universal joint inner ring 3 is provided with four horizontal coaxial through holes (cross shaft holes) symmetrically
  • the outer universal joint outer ring 17 is used as a driven fork
  • the shaft b9 is respectively installed in the through holes of the two vertical support frames at the outer end of the fixed end support base 5 through the flange bearing a8 and the flange bearing b10; the coaxial through holes on both sides of the outer universal joint inner ring 3 pass through the common
  • the flat key a6 and the ordinary flat key b11 are fixedly connected to the connecting shaft a7 and the connecting shaft b9, and the fixed end supporting seat 5 and the outer universal joint inner ring 3 realize relative rotation to form a pitch angle rotation
  • the three-axis Helmholtz coil group a includes a large coil group, a small coil group and an intermediate coil group, each group includes two identical coils arranged symmetrically; the axes of the three groups of coils are perpendicular to each other, and the three groups of coils Fixed to each other, where the bottom of the large coil group is fixed on the fixed end e, and the axis of the middle coil group coincides with the axis of the fixed end e; the inner cross universal joint d is located in the inner space between the three groups of coils, and the outer cross universal joint The joint c is located outside the three sets of coils; the external cross universal joint c, the three-axis Helmholtz coil set a, and the internal cross universal joint d form a three-layer nested structure in space.
  • the two input ends and output ends of the inner and outer gimbal joints of a new type of electromagnetically driven two-degree-of-freedom spherical robot wrist of the present invention are coaxially connected in parallel, and the inner and outer gimbals have the same rotation center, thus forming a spherical wrist ,
  • the movement decoupling of the two degrees of freedom of the wrist is realized, and the side roll and pitch angle can be measured and controlled separately.
  • Both the inner and outer universal joints adopt a hollow structure, which can significantly increase the internal nesting and accommodating space, and the multi-layer nesting structure of the wrist is compact.
  • the side swing and pitch angles of the end effector connected to the wrist output end are controllable, but the rotation angle is always not deflected, and the normal direction of the end effector can be easily adjusted to complete the wrist positioning.
  • the invention overcomes the disadvantages of the complex transmission mechanical wrist, the wrist transmission system has a simple and portable structure, high transmission efficiency, good system static and dynamic performance, and fast control response speed. Because the transmission chain is simple and there is no mechanical gap, the positioning accuracy is high. Since there is no non-linear friction force of the complex mechanical transmission system, the variable stiffness control and compliance control of the wrist joint can be quickly realized by electromagnetic direct drive.
  • the present invention overcomes the problem of modeling the three-dimensional complex magnetic field of the existing spherical electromagnetic drive joints, can realize accurate magnetic field modeling and calculation, and quantitatively analyze the electromagnetic coupling and mechanical coupling relationship between the respective degrees of electromagnetic drive joints, and realize precise decoupling and structure. Parameter optimization is expected to eventually achieve the response sensitivity and positioning accuracy of electromagnetically driven spherical joint control.
  • Fig. 1 is a schematic diagram of the structure of the robot wrist of the present invention.
  • Fig. 2 is a schematic diagram of the follow-up part of the robot wrist rotor of the present invention.
  • Fig. 3(A) is a schematic cross-sectional view of the wrist pitch transmission mechanism of the robot of the present invention.
  • Fig. 3(B) is a partial enlarged view at I of the schematic cross-sectional view of the wrist pitch transmission mechanism of the robot of the present invention.
  • Fig. 3(C) is a partial enlarged view of the section II of the schematic diagram of the wrist pitch transmission mechanism of the robot of the present invention.
  • Fig. 3(D) is a schematic cross-sectional view of the lateral swing transmission mechanism of the robot wrist of the present invention.
  • Fig. 3(E) is a partial enlarged view of part III of the schematic cross-sectional view of the lateral swing transmission mechanism of the robot wrist of the present invention.
  • Fig. 3(F) is a partial enlarged view of the section IV of the lateral swing transmission mechanism of the robot wrist of the present invention.
  • Fig. 3(G) is a partial enlarged view of the section V of the lateral swing transmission mechanism of the robot wrist of the present invention.
  • Fig. 3(H) is a partial enlarged view at VI of the schematic cross-sectional view of the lateral swing transmission mechanism of the robot wrist of the present invention.
  • Fig. 4(A) is a schematic diagram of the transformation process of the axis of the robot wrist of the present invention from the fixed coordinate system to the Lai-Chai coordinate system.
  • Fig. 4(B) is a schematic diagram of the spatial position of the axis vector of the robot wrist and the axis vector of the space universal rotating magnetic field of the present invention.
  • Fig. 4(C) is a schematic diagram of a coaxial follower magnetic moment effect driving model of the robot wrist of the present invention.
  • Fig. 4(D) is a schematic diagram of the establishment of the coordinate system for calculating the coaxial follow-up magnetic moment of the robot wrist of the present invention.
  • Fig. 5 is a schematic diagram of the active and passive mode control principle of the robot wrist of the present invention.
  • a three-axis Helmholtz coil group a three-axis Helmholtz coil group; b rotor follow-up part; c external cross universal joint; d internal cross universal joint; e fixed end; f end effector; g force sensor; h two degrees of freedom Robot wrist.
  • the two-degree-of-freedom spherical robot wrist h of the present invention includes a three-axis Helmholtz coil group a and a rotor follower part b.
  • the three-axis orthogonal Helmholtz coil group a provides a space universal rotating magnetic field
  • the rotor follower part b provides a rotating magnetic field. Coaxial follow-up magnetic moment effect to the rotating magnetic field.
  • the rotor follow-up part b includes an internal cross universal joint d (with rotor permanent magnets, that is, a radially magnetized permanent magnet 1), an external cross universal joint c (installed with a braking mechanism, a damping mechanism, a measuring mechanism, etc.), and Fixed end e.
  • the rotation center of the inner cross universal joint d and the outer cross universal joint c are the same, that is, the wrist rotation center, forming a spherical wrist, which realizes the decoupling of rotation of two degrees of freedom, and can implement separate measurement of roll angle and pitch angle And control; both the internal cross universal joint d and the external cross universal joint c adopt a hollow structure to increase the internal accommodating space.
  • Both the internal cross universal joint d and the external cross universal joint c use the fixed end support 5 as the input end (active fork) to ensure that the two input ends are coaxial; the external cross universal joint c output end 33 (driven fork) It is also coaxially connected with the output end of the inner cross universal joint d, that is, the connecting rod 32 (driven fork), which constitutes the wrist rotor follow-up part b.
  • the axis b of the follower part of the rotor is the axis of rotation of the wrist.
  • the axis b of the follower part of the rotor of the wrist can realize the rotation movement of the fixed point (wrist rotation center) with two degrees of freedom of side and pitch.
  • the radial magnetized permanent magnet 1 is installed in the follower part b of the rotor. The inner and can rotate freely with the rotating magnetic field, and the coaxial follow-up magnetic moment of the outer rotating magnetic field is driven by the power medium and realizes the lateral swing and pitch steering movement of the wrist.
  • the external cross universal joint c includes: two vertical support frames (active forks) at the outer end of the fixed end support base 5, the inner ring 3 of the external universal joint (cross shaft bracket) and the outer ring 17 of the external universal joint (driven fork) ).
  • the outer gimbal inner ring 3 is an integral ring structure, with four holes (cross shaft holes) evenly distributed around the circumference;
  • the outer gimbal outer ring 17 is composed of two semi-annular structure support rods symmetrically, and two semi-annular structure support rods Two coaxial holes are evenly distributed on the top.
  • the posture of the end effector f connected to the output end 33 of the external cross universal joint c is determined by the side swing and pitch angle of the axis b of the rotor follower part. Because the input end of the external cross universal joint c, that is, the fixed end support seat 5 cannot When rotating, the posture of the end effector f is consistent with the axis of the rotor follow-up part b. Therefore, the rotation angle of the end effector f does not deflect, and the normal direction of the end effector f of the robot can be conveniently adjusted to complete the wrist positioning.
  • a force sensor g can be installed on the end effector f.
  • the fixed end support 5 (equivalent to the active fork) and the outer universal joint inner ring 3 can realize relative rotation.
  • the assembly process of the pitch angle shaft is: the outer universal joint inner ring 3 It is fixedly connected to the connecting shaft a7 through a common flat key a6, and a vertical support frame at the outer end of the fixed end supporting seat 5 is connected to the connecting shaft a7 through a flange bearing a8; the outer universal joint inner ring 3 is connected to a common flat key b11
  • the shaft b9 is fixedly connected, and the other vertical support frame at the outer end of the fixed end supporting seat 5 is connected to the connecting shaft b9 through a flange bearing b10.
  • the outer joint ring 17 is fixedly connected to the connecting shaft c21 through a common flat key c20, the outer universal joint inner ring 3 is connected to the connecting shaft c21 through a flange bearing c22; the outer universal joint outer ring 17 is connected to the connecting shaft through a common flat key d29 F28 is fixedly connected, and the outer universal joint inner ring 3 is connected to the connecting shaft f28 through a flange bearing d27.
  • the internal cross universal joint d includes: two vertical support frames (active forks) in the middle of the fixed end supporting seat 5, the internal universal joint inner ring 14 (cross shaft) and the cylindrical shell 2 (driven fork) three parts;
  • the inner universal joint inner ring 14 is equivalent to a cross shaft bracket.
  • the two vertical support frames in the middle of the fixed end support 5 and the inner universal joint inner ring 14 can realize relative rotation.
  • the assembly process of the pitch rotation axis is: inside the inner universal joint
  • the ring 14 is connected to the two vertical support frames in the middle of the fixed end supporting seat 5 through the deep groove ball bearing a15 and the deep groove ball bearing b16.
  • the cylindrical shell 2 and the inner universal joint inner ring 14 can realize relative rotation.
  • the assembly process of the side swing angle shaft is: one end of the connecting shaft d23 is fixed to the cylindrical shell 2. The other end is connected to the inner universal joint inner ring 14 through the deep groove ball bearing c24; one end of the connecting shaft e26 is fixed to the cylindrical housing 2, and the other end is connected to the inner universal joint inner ring 14 through the deep groove ball bearing d25 .
  • the rotor follow-up part b is formed by the outer cross universal joint c and the inner cross universal joint d.
  • the characteristics are: the rotation center of the inner and outer cross universal joints is the same (that is, the wrist rotation center), the outer cross universal joint c and the inner
  • the input end (active fork) and output end (driven fork) of the cross universal joint d are coaxially fixed respectively, thus forming a spherical wrist, which realizes the decoupling of the rotation of two degrees of freedom, and further, the side swing angle can be implemented Separate measurement and control of pitch angle and pitch angle.
  • Both the external cross universal joint c and the internal cross universal joint d adopt a hollow structure to increase the internal accommodating space; the input terminals of the external cross universal joint c and the internal cross universal joint d
  • the (active forks) are all fixed-end support seats 5, which are equivalent to the coaxial and fixed connection of the input ends of the external universal joint c and the internal universal joint d.
  • the output ends (driven forks) of the external cross universal joint c and the internal cross universal joint d are coaxially connected, that is, the coaxial connection process of the outer cross universal joint outer ring 17 and the cylindrical shell 2 is: connecting rod
  • the two ends of 32 are respectively fixed to the cylindrical shell 2 and the output end 33, and the output end 33 is fixed to the outer ring 17 of the external cross universal joint.
  • the radially magnetized permanent magnet 1 is installed in the cylindrical housing 2 through a bearing 31, and the radially magnetized permanent magnet 1 can realize coaxial rotation relative to the rotor follower b.
  • the rotor follower part b that forms the wrist is coaxially connected.
  • the axis of the rotor follower part b is the wrist rotation axis, which can realize the rotation movement of the fixed point (wrist rotation center) with two degrees of freedom of side swing and pitch.
  • the radial magnetized permanent magnet 1 is in Driven by the coaxial follow-up magnetic moment of the space universal rotating magnetic field, the wrist can be moved at a fixed point with two degrees of freedom in lateral swing and pitch.
  • the detection and control methods of wrist posture are as follows:
  • the outer cross universal joint c consists of two vertical support frames at the outer end of the fixed end support base 5, and the three parts of the outer universal joint inner ring 3 and the outer universal joint outer ring 17 move relative to each other to realize the universal rotation of the wrist axis.
  • the outer gimbal inner ring 3 is an overall annular structure with four holes (cross-shaft holes) evenly distributed on the circumference; the outer gimbal outer ring 17 is symmetrical by two semi-annular structure support rods with two coaxial holes evenly distributed on the top end
  • the composition therefore, can be connected as follows:
  • a set of two coaxial holes of the outer universal joint inner ring 3 (cross shaft bracket) and two vertical support frames (active forks) at the outer end of the fixed end support seat 5 are connected to form a pitch angle rotation axis (a cross shaft), and the external universal joint
  • the inner joint ring 3 can rotate around the axis, and the absolute encoder a4, brake a13, and damper a12 are installed between the two vertical support shafts of the outer universal joint inner ring 3 and the outer end of the fixed end support base 5, respectively, then
  • the encoder a4 can measure the relative rotation angle between the two vertical supports at the outer end of the outer gimbal inner ring 3 and the fixed end support base 5, which is the wrist pitch angle; the outer gimbal inner ring 3 another set of two coaxial
  • the two holes and the outer universal joint outer ring 17 are coaxially connected to form another side swing angle shaft (another cross shaft).
  • the outer universal joint outer ring 17 is opposite to the inner universal joint.
  • the ring 3 can rotate around the axis, and the absolute encoder b18, brake b19, and damper b30 are installed between the shafts of the outer universal joint inner ring 3 and the outer universal joint outer ring 17 respectively, then the encoder b18 can measure the outer universal joint
  • the relative rotation angle between the inner ring 3 and the outer gimbal outer ring 17 is the wrist lateral swing angle.
  • the two absolute encoders b18 and a4 installed at the two sets of vertical rotation axes of the external cross universal joint c can realize the real-time measurement of the side roll and pitch angle, and transmit them to the control system to achieve the opposite side roll Accurate control of movement with pitch angle.
  • Brake a13 and brake b19 are both electromagnetic brakes, which can lock the wrist pitch and roll.
  • brake a13 and brake b19 can lock the external cross universal joint d to fix the rotor follow-up.
  • the orientation of part b prevents accidents due to random swinging; when the wrist rotates, the brake a13 and the brake b19 unlock the external cross universal joint d, so as to realize the follow-up of the rotor follow-up part b and the universal rotating magnetic field.
  • Drive for roll and pitch rotation When only one rotation axis of the external universal joint is locked, the wrist becomes a single degree of freedom to rotate the wrist.
  • the movement of the two degrees of freedom is independent of each other and does not affect each other. Independent detection and control can be realized, and two single freedoms of wrist roll and pitch can be realized. Degree control mode.
  • the damper a12 and the damper b30 are installed at the two cross rotation axis joints (pitch and roll rotation axis) of the external cross universal joint d to provide damping for the pitch and roll rotation of the wrist, so as to slow down the roll and pitch adjustment of the wrist Vibration.
  • the active drive control of the coaxial follow-up magnetic moment of the rotating magnetic field can release the restraint of the wrist pitch and side swing, turning the wrist into a compliant passive wrist, effectively removing mechanical interference and satisfying the space
  • the extreme environment has special requirements for the robot's wrist, completing complex tasks such as rotating installation and opening the hatch.
  • the realization process of the pitch angle movement measurement is: the outer universal joint inner ring 3 is fixedly connected to the connecting shaft a7 through the ordinary flat key a6, and the fixed end support seat 5 (the active fork of the outer cross universal joint c) is connected to the flange bearing a8
  • the connecting shaft a7 is connected to realize the relative rotation of the outer universal joint inner ring 3 and the fixed end supporting base 5; the encoder a4 is fixed to the fixed end supporting base 5 and connected with the connecting shaft a7 to realize the pitch angle measurement.
  • the realization process of the pitch angle motion control is: the outer universal joint inner ring 3 is fixedly connected to the connecting shaft b9 through a common flat key b11, and the fixed end support seat 5 is connected to the connecting shaft b9 through a flange bearing b10 to realize the external universal joint.
  • the realization process of the roll angle movement measurement is: the outer universal joint outer ring 17 is fixedly connected to the connecting shaft c21 through a common flat key c20, and the outer universal joint inner ring 3 is connected to the connecting shaft c21 through a flange bearing c22 to realize the external The relative rotation of the outer universal joint ring 17 and the outer universal joint inner ring 3; the encoder b18 is fixed to the outer universal joint inner ring 3 and connected with the connecting shaft c21 to realize the side swing angle measurement.
  • the realization process of the roll angle motion control is: the outer universal joint outer ring 17 is fixedly connected to the connecting shaft f28 through a common flat key d29, and the outer universal joint inner ring 3 is connected to the connecting shaft f28 through a flange bearing d27 to realize the external The relative rotation of the universal joint outer ring 17 and the outer universal joint inner ring 3; the damper b30 is fixed to the outer universal joint inner ring 3 and connected to the connecting shaft f28 to realize the change of the damping characteristics of the roll angle to reduce Vibration phenomenon; the brake b19 is fixed to the inner ring 3 of the outer universal joint and connected with the connecting shaft c21 to realize the locking of the side swing angle. This part of the structure realizes the functions of braking, measuring and changing the damping characteristics of the side swing.
  • Fig. 4(A) The coordinate system established in Fig. 4(A) is as follows: the fixed coordinate system Oxyz is consolidated with the three-axis Helmholtz coil group a, the initial position of the wrist axis is vertical upwards, and the Oz axis and the external cross universal joint c are connected to the encoder a4 The pitch angle rotation axis coincides, wherein the Ox axis coincides with the lateral swing angle rotation axis of the external cross universal joint c connected to the encoder b18.
  • the Lai-Chai coordinate system Ox 1 y 1 z 1 is obtained by two rotations of the fixed coordinate system Oxyz.
  • the fixed coordinate system Oxyz first rotates the pitch angle ⁇ around the Oz axis to obtain the intermediate coordinate system Ox 1 y'z, which is compared with the external cross universal
  • the pitch angle ⁇ of the encoder a4 connected to section c can be measured, and the Ox 1 axis always coincides with the roll angle rotation axis of the external cross universal joint c connected to the encoder b18.
  • the intermediate coordinate system Ox 1 y'z revolves around the Ox 1 axis.
  • the pitch angle ⁇ and the roll angle ⁇ used in the transformation process of the Lai-Chai coordinate system Ox 1 y 1 z 1 in Fig. 4(A) are used to describe the space of the wrist axis and the rotation axis of the space universal rotating magnetic field in the fixed coordinate system Oxyz Orientation, omitting the motor structure, the radial magnetization permanent magnet 1 axis direction vector n 2 ( ⁇ 0 , ⁇ 0 ) (wrist axis vector) and the space universal rotating magnetic field rotation axis vector n 3 ( ⁇ 3, ⁇ 3) at any spatial position in the fixed coordinate system, O a, O b are vectors and vector n 2 n 3 end of the projection in the plane Oxy.
  • the space angle between vector n 2 and vector n 3 is ⁇ .
  • Figure 4(C) is a diagram of a wrist coaxial follow-up magnetic moment effect driving model. It can be obtained by intercepting the plane composed of vector n 2 and vector n 3 in Figure 4(B).
  • the driving model is a radial magnetized permanent magnet 1 with a magnetic moment of m (rotating axis n 2 ) in a rotating magnetic field B (rotating axis n 3 )
  • the relative motion relationship that rotates at the angular velocity ⁇ at the same time in the inside, where the three-axis Helmholtz coil group a generates the space universal rotating magnetic field and the rotation axis vector n 3 ( ⁇ 3 , ⁇ 3 ) is fixed, and they are respectively passed through the external cross
  • the brake a13 and the brake b19 on the joint c realize the locking of the pitch angle ⁇ 0 and the roll angle ⁇ 0 , and the axis direction vector n 2 ( ⁇ 0 , ⁇ 0 ) of the radial magnetized permanent magnet 1 is
  • Figure 4(D) is a schematic diagram of the establishment of the coordinate system for calculating the coaxial magnetic moment of the robot wrist according to the present invention.
  • the fixed coordinate system Ox 3 y 3 z 3 where the rotating magnetic field is located and the fixed coordinate system Ox 2 y 2 z 2 where the magnetic moment rotation vector m is located The establishment is as follows: take the vectors n 2 and n 3 as the Oy 2 and Oy 3 axes respectively, and take the intersection of the magnetic field rotation plane and the rotation plane of the magnetic moment vector m as the Oz 2 and Oz 3 axes, and O is the two fixed coordinate systems origin.
  • the coordinate system Ox 3 y 3 z 3 where the rotating magnetic field is located is obtained from the coordinate system Ox 2 y 2 z 2 where the magnetic moment rotation vector m is located by rotating Oz 2 by - ⁇ , then the coordinate system where the rotating magnetic field is located is Ox 3 y 3 z 3 to the magnetic moment
  • the transformation matrix between the coordinate system Ox 2 y 2 z 2 where the rotation vector m is located is
  • ob is the unit rotating magnetic vector in the coordinate system Ox 3 y 3 z 3 , the coordinates are (cos( ⁇ t), 0, -sin( ⁇ t)), om 1 is the unit magnetic moment vector in the coordinate system Ox 2 y 2 z 2 Is (cos( ⁇ t- ⁇ 1 ), 0,-sin( ⁇ t- ⁇ 1 )), and ⁇ 1 is the slip angle of the magnetic moment m relative to the rotating magnetic field B.
  • m 0 and B 0 are the magnetic moment vector and the magnitude of the magnetic vector.
  • T x2 , T y2 and T z2 are all periodic functions, and the periods are respectively
  • the angle ⁇ is the angle between the axis of the m permanent magnet cylinder and the axis of rotation of the rotating magnetic field B, and m 0 , B 0 are the magnitude of the magnetic moment vector and the rotating magnetic vector.
  • the permanent magnet When the wrist-driving magnetic moment vector is provided by the radially magnetized permanent magnet 1, in each cycle, the permanent magnet is only extended by the negative magnetic moment of the Oz 2 axis. Under the action of this magnetic moment, the magnet magnetic moment vector m rotates the plane Flip to the plane of rotation of the magnetic vector B, that is, the axis of the permanent magnet approaches the axis of the rotating magnetic field.
  • the magnetic moment vector is the coaxial follow-up magnetic moment of the permanent magnet.
  • the magnetic moment of the rotating magnetic field coaxial follower effect may be directed to any permanent magnet axis orientation space, respectively, if the pitch angle ⁇ 0 b19 is released and the side swing angle ⁇ 0 c joint cross through the external a13 and brake lock brakes, the radial The axis direction vector n 2 ( ⁇ 0 , ⁇ 0 ) of the magnetized permanent magnet 1 can not only rotate with the space universal rotating magnetic field at a speed ⁇ , but also drive the rotor follower part b to the space universal rotating magnetic field rotation axis vector n 3 ( ⁇ 3 , ⁇ 3 ) Rotation. It is completely possible to use the coaxial follower magnetic moment for the electromagnetic drive of the ball joint, which is the theoretical basis for the electromagnetic drive of the ball joint.
  • One An electromagnetically driven two-degree-of-freedom spherical robot wrist is a directly electromagnetically driven spherical active joint.
  • the principle of electromagnetic driving is the coaxial follower magnetic moment effect of the rotating magnetic field.
  • the coaxial follower magnetic moment only acts on the magnet magnetic moment vector m In the rotation plane formed by the rotation axis n 2 and the magnetic vector B rotation axis n 3 , the rotation plane of the magnet magnetic moment vector m and the rotation plane of the magnetic vector B are flipped. Obviously, the force vector F at the end of the end effector f is also rotating In the rotation plane formed by the axis n 2 and the rotation axis n 3 , the formula (3) is the calculation formula of the coaxial follower magnetic moment.
  • Equation (3) shows that the coaxial follow-up magnetic moment of the wrist can be controlled by the amplitude I 0 of the sinusoidal current in the three sets of orthogonal Helmholtz coils, or by the angle ⁇ , and can also be controlled at the same time to increase Magnetic moment.
  • the included angle ⁇ changes greatly. Due to the large torque adjustment range, the coaxial follower magnetic moment of the permanent magnet can pass through the amplitude I 0 of the sinusoidal current in the three sets of orthogonal Helmholtz coils at the same time.
  • the angle ⁇ between the axis of the permanent magnet cylinder and the axis of the rotating magnetic field is controlled to increase the torque adjustment range and make the wrist become a compliant wrist. Since there is no friction in the complex mechanical transmission system, the torque control can be quickly realized by electromagnetic direct drive.
  • s is the deformation of the end of the end effector f along the direction of the force
  • L is the distance from the force F of the end of the actuator to the center of the electromagnetically driven ball joint.
  • the torque generated by the force F at the end of the end effector f should be equal to the coaxial follow-up magnetic moment of the rotating magnetic field, that is
  • Equation (6) shows that the stiffness of the new electromagnetically driven ball joint can be linearly controlled by rotating the magnetic vector amplitude B 0 , which can be controlled by the sinusoidal current amplitude I 0 in the three sets of orthogonal Helmholtz coils Because there is no friction of the complex mechanical transmission system, the complicated variable stiffness mechanical adjustment mechanism is avoided, and the joint variable stiffness control can be quickly and conveniently realized by electromagnetic direct drive, and the control accuracy is significantly improved.
  • the angle ⁇ changes very small
  • (6) The formula is established. That is, when F is small, the angle ⁇ changes very little, and the stiffness of the wrist can be directly controlled according to formula (6). At this time, it can be controlled only by the amplitude I 0 of the sinusoidal current, so that the wrist becomes a compliant wrist.
  • the calibration process of the posture zero point of the new type of electromagnetic drive wrist before operation is: the three-axis Helmholtz coil group a generates a spatial universal rotating magnetic field with the rotation axis perpendicular to it. Driven by the coaxial follower magnetic moment, the rotor follower part b is connected to the fixed The axis of end e coincides. At this time, the relative rotation angle of the pitch angle encoder a4 and the roll angle encoder b18 is zero. At this time, the encoder a4 and the encoder b18 are powered on, and the two-degree-of-freedom solution is stored and memorized.
  • the coaxial follow-up magnetic moment control system and encoder a4 and encoder according to formula (3) b18 constitutes a closed-loop control of the corner position, which improves the control accuracy by real-time sensing and memory of the lateral swing and pitch positions of the wrist with two degrees of freedom.
  • the brake a13 and the brake b19 have been locked to the external cross universal joint c, and the roll and pitch motions cannot be performed.
  • the second step is to determine the direction of the axis of rotation to which the universal rotating magnetic field should be applied according to the target space orientation.
  • three groups of equal-frequency alternating current are applied to the three-axis Helmholtz coil group a to generate the corresponding azimuth space Rotating magnetic field.
  • the radially magnetized permanent magnet 1 starts to rotate under the action of the rotating magnetic field, and generates a coaxial follow-up magnetic moment according to formula (3), but because the brake a13 and the brake b19 have two degrees of freedom on the external cross universal joint c Locked, the rotor follow-up part b cannot perform side swing and pitch motions.
  • the brake a13 and the brake b19 are energized to release the lock on the external cross universal joint c, and the radial magnetized permanent magnet 1 is under the action of the coaxial follow-up magnetic moment of the rotating magnetic field, and the axis of the rotor follow-up part b follows the axis of the rotating magnetic field.
  • Roll and pitch motion pitch angle is measured by encoder a4, yaw angle is measured by encoder b18, the movement process is damped by damper a12 and damper b30 to prevent vibration.
  • the fifth step is to feed back the pitch and roll angle information in real time through the encoder 4a and the encoder b18; according to the feedback angle information, the coaxial follower magnetic moment is feedback controlled according to formula (3), until the accuracy is satisfied, the wrist reaches The target position realizes the control of two-degree-of-freedom motion.
  • the three-axis Helmholtz coil group a is powered off, the brake a13 and the brake b19 are powered off, and the external cross universal joint c is locked again to fix the orientation of the robot's wrist.
  • the wrist becomes a single degree of freedom to rotate the wrist.
  • the movement of the two degrees of freedom is independent of each other and does not affect each other. Independent detection and control can be realized, and the wrist swing and pitch can be realized.
  • Single degree of freedom control mode The single degree of freedom has good modal stability and few control variables, and is used for precise position control.
  • the other steps are the same.
  • the fourth step and the fifth step above are respectively controlled as follows to realize the single-degree-of-freedom control mode.
  • the brake a13 is energized to release the uniaxial lock of the external cross universal joint c.
  • the radial magnetized permanent magnet 1 is under the action of the coaxial magnetic moment of the rotating magnetic field, and the axis b of the rotor follower part follows the axis of the rotating magnetic field.
  • the deflection angle is measured by encoder b18; or only the brake b19 is energized to release the uniaxial lock to the external cross universal joint c, the radial magnetized permanent magnet 1 is under the action of the coaxial follow-up magnetic moment of the rotating magnetic field, the rotor
  • the axis of the follower part b follows the axis of the rotating magnetic field for side swing motion, and the pitch angle is measured by the encoder a4.
  • the fifth step is to feed back the pitch or roll angle information in real time through the encoder a4 or the encoder b18; according to the feedback angle information, the coaxial follower magnetic moment is feedback controlled according to formula (3), until the accuracy is satisfied, the wrist reaches The target position respectively realizes the control of single degree of freedom movement.
  • the rotor follow-up part b of the wrist h of the two-degree-of-freedom robot has the functions of side swing and pitch drive, which can realize the pitch swing of the wrist end effector f in any plane of the axis e of the fixed end.
  • a force sensor g is installed on the robot wrist end effector f.
  • the coaxial follower magnetic moment control system and the force F detected by the force sensor g are formed Closed-loop control, according to the size of the force F, that is, when F is large, the included angle ⁇ changes greatly.
  • the coaxial follow-up electromagnetic driving torque is controlled, even if the wrist output end is subjected to the detection force in the plane.
  • the force direction directly reduces the amplitude of the sinusoidal current I 0 and changes the angle ⁇ through the direction of the space universal rotating magnetic field and reduces it, ensuring that the trajectory of the wrist end effector f is composed of the axis of the end effector f and the force F
  • the plane swings in the direction of the force F; when F is very small, the angle ⁇ changes very little, and the amplitude I 0 of the sinusoidal current can be directly reduced according to formula (6), and the stiffness of the wrist h of the two-degree-of-freedom robot can be controlled.
  • the wrist end effector f moves along the direction of the force F in the plane of the force F.
  • the force F detected by the coaxial follower magnetic moment control system and the force sensor g is controlled by a closed loop and follows the force Swing in the direction of F.
  • the force F value detected by the force sensor g is as small as 0.1N, the passive wrist can be completely compliant, which improves the flexibility of the wrist and protects the wrist from damage when the door is opened.
  • the direction of the force F changes, but when F is large, the included angle ⁇ changes greatly.
  • the coaxial follower magnetic moment is controlled to change the direction and magnitude of the torque, that is, the amplitude of the sinusoidal current is directly reduced I 0 and make the wrist output end change the included angle ⁇ along the force direction in the detection force plane and reduce it; when F is very small, the angle ⁇ changes very little, and the formula (6) is established, then directly follow the formula (6) Reduce the amplitude I 0 of the sinusoidal current, realize variable stiffness control, and protect the wrist.
  • the two-degree-of-freedom robot wrist h is operated in the passive wrist mode, the position of side roll and pitch can still be stored in the absolute encoder a4 and absolute encoder b18.
  • the two-degree-of-freedom robot wrist h is restored to the active wrist after the operation is completed, it can be restored to Zero calibration position.
  • the constraints of the wrist pitch and side swing can be lifted, and the wrist becomes a passive wrist mode.
  • the wrist becomes a compliant rope, which is completely compliant and effective. It can relieve mechanical interference, meet the special needs of the robot wrist in the extreme space environment, and complete complex tasks such as pulling out rocks and opening the spacecraft door when sampling alien planets.

Abstract

一种电磁驱动两自由度球型机器人手腕及其控制方法，包括一种通过相同转动中心的内、外部十字万向节（c、d）两个输出端（33）同轴连接所构成转子随动部分（b），转子随动部分（b）内置的径向磁化永磁体（1）在空间万向旋转磁场同轴随动磁矩的直接驱动下实现侧摆、俯仰二自由度转动。该装置克服了复杂传动机械手腕的弊端及现有球形电磁驱动关节三维复杂磁场难建模的问题，实现球形电磁驱动关节磁场精确建模和电磁耦合和力学耦合的精准解耦，显著提高电磁驱动球形关节控制的响应灵敏度和定位精度。

Description

一种电磁驱动两自由度球型机器人手腕及其控制方法 技术领域
本发明属于自动化工程技术领域，涉及一种电磁驱动两自由度球型机器人手腕及其控制方法，具体为一种通过相同转动中心的内、外部万向节两个输出端(从动叉)同轴连接所构成随动机构内置径向磁化永磁体在空间万向旋转磁场同轴随动磁矩直接驱动下实现侧摆、俯仰二自由度转动的机器人高集成主动球型手腕装置。
背景技术
应用于危险和极限环境下的机器人对腕部的性能指标要求苛刻，如空间机器人的显著特征是结构紧凑，集成化程度高，功重比大。空间机器人在航天器和空间站的维护等任务中发挥着越来越重要的作用，如飞船的控制与舱门的开启、空间舱段的组装、航天器的维修等，均可代替宇航员完成。腕部是联结臂与手的重要基础部件，其性能直接影响机器人末端执行器的定位精度、灵活性与作业功能。机器人腕部的功用是通过局部微小调整来改变末端执行器在空间的姿态，实现准确定位，腕部的自由度及姿态范围直接影响机器人的灵活性、稳定性与定位精度，机器人任意位置及姿态的控制需要六个自由度，手腕至少应有两个自由度，手腕位于臂部的前端，腕部的重量又构成小臂的附加载荷而增加能耗。腕部是在狭小的空间实现两轴回转，因此手腕的机构设计复杂、可变参数多，手腕的性能指标已经成为限制机器人在空间等极限环境下应用与扩展的主要瓶颈。
目前，机器人腕部尚不能完全满足空间作业要求，其多自由度运动的传递普遍采用齿轮传动，结构复杂、集成度低，存在运动耦合问题，使得末端执行器的灵活性、姿态调整能力和精确定位能力受限，尚不能通过腕部的调整完成飞船舱门开启等复杂性接触作业。
从结构方面，机器人手腕基本上可分为三类：1)球型手腕，它的三个关节轴线相交于一点,其位置和姿态是解耦的，逆运动学分析简单，结构紧凑,功重比大，所以空间机器人等特殊场合下使用的机器人大多采用球型手腕。由于受机械结构的限制，这种手腕设计难度大，结构复杂，重量难以降低，工作空间小；2)非球型手腕，它的三个轴线不交于一点，克服了机械结构的局限性,每个关节的转动角度都能达到360°以上，但其缺点是结构不紧凑，体积庞大，限制了功重比指标的提高，运动不能解耦，控制精度低；3)并联结构手腕，此种结构的手腕实际上是一种小型化的并联机构。
The Martin Marietta和美国NASA的宇航飞行中心于1991年研制的一种用于空间站装配的遥控机器人腕部模块，其电机的布置采用俯仰、侧摆和自转分离方式，但其结构不紧凑，功重比小，三个关节的运动不解耦，控制精度低。
1991年Graco Robotics,Inc.研制了紧凑型双万向节万向腕，它的斜齿轮传动链由防倾斜的在齿轮滑轨内运动的凸轮机构导向来保证，克服了以往腕部功重比小和结构强度欠佳的缺点，俯仰和侧摆分别由两个相交的万向节转动轴传动，使结构更加紧凑，但该腕部的缺点仍然是结构复杂，加工难度大，但腕部斜齿轮在载荷的作用下有跳跃的不平稳现象。
NASA研制了新一代的腕部模块，传动系统采用三个并联的螺杆驱动实现侧摆、俯仰，简化了设计，降低了成本，由于其附加的灵活性适于非结构化环境，NASA喷气推力实验室已经将该万向腕成功的应用于处理危险的物品。但该腕部的缺点是要三个驱动实现侧摆、俯仰两个运动。
从操作方式方面，机器人作业可分为非接触与接触两大类：前者为机器人在自由空间中运动，不受外界环境约束，采用单纯位置控制即可，机器人位置控制只适合在结构化可建模环境内作业；后者受外界环境约束，如空间机器人开门、装配，旋转曲柄等任务。在未建模环境中的抓取、安装、定位等作业机器人具有明显接触作业特征，其腕部应该具有变刚度柔顺控制功能，以免接触作业时损坏机械臂。
对于接触作业，只采用位置控制已不能胜任，因为作业环境对机器人有接触力影响，其末端微小位置偏差可导致较大的接触力，极易损坏机械臂或作业目标，可见，未建模环境中目标抓取等作业绝非易事。目前，空间机械臂等手腕尚不完全具备非结构未建模环境中接触作业的能力。
迄今为止，柔顺控制主要分为两种：主动式和被动式。机器人通过处理力反馈信息并采用一定控制策略去主动控制作用力的方式称为主动柔顺控制。相反，机器人不通过力反馈而只是凭借机械等柔顺机构，使其自然顺从接触环境的方式称为被动柔顺控制。主动柔顺控制又分为主动阻抗控制和力/位置混合控制。力/位置混合控制方法对外界环境动力学依赖性强，需要详尽的任务描述。被动柔顺控制的研究主要是通过机械装置本身或特殊设计的被动柔顺机构来实现，如机器人手腕的RCC弹性附件，缺点是要增加额外的机械装置，使腕部机构变得复杂笨重，适应能力差。
韩国提出了一种球型两自由度主动驱动机器人腕部关节及主动柔顺控制方法。它的下半球运动通过齿轮传动实现，上半球通过内部万向节传递运动，两个偏置斜面复合成腕子的侧摆与俯仰两个运动，结构紧凑、简单，且实现了两个输入运动的解耦，并通过离合器的啮合程度控制传递力矩的大小，使腕部在一定力矩的作用下成为被动腕，起到了过载荷保护和避免机械干涉而损坏腕部关节的作用。
大连理工大学提出了一种三自由度等速解耦空间机器人主动球型腕与万向柔顺控制方法(专利号：ZL201310282753.1)，是一种典型的主动柔顺控制方法，具体通过摩擦力补偿可实现主、被动腕功能，被动模态下球型腕处于完全柔顺状态，避免接触作业损坏机械臂。但机器人关节非线性摩擦力模型难以准确确定，摩擦力补偿精度会直接影响柔顺控制效果，手腕三轴转动控制过程复杂。
综上所述，由于机器人手腕机械系统结构复杂程度高，运动传动系统摩擦具有非线性特征，最终导致机械结构手腕动态性能差、控制精度低，机械效率低，可靠性差等问题。尤其是机械手腕复杂的传动结构与实现主动柔顺控制之间存在矛盾，导致柔顺控制难度大，响应速度低。由于传统机械式手腕减速器系统存在输出端反向传动自锁特性，接触作业时，必须施加主动控制力矩消除关节摩擦力，才能解除自锁，实现柔顺控制，但由于关节减速器系统的摩擦力表现为复杂的非线性，导致机械关节柔顺控制功能差而极易损坏机械臂。
为了克服上述机械传动手腕的弊端，使多自由度手腕传动系统结构简单轻便，并显著提高运动性能、传动效率、控制响应速度和定位精度，可采用电磁直接驱动多自由度电机代替复杂传动机械手腕。多自由度电机集成度高，传动链简单且无机械间隙，有效材料和控制系统元件的利用率高，特别是转动的自由度多，可显著简化机械系统结构，避免关节的非线性摩擦力，提高系统静态及动态性能。
球形电机是集现代电机设计理论、功率电子技术、自动控制理论于一体的高技术，球形 电动机本身就是一种直接驱动的球形主动关节。按原理主要可分成以下几类：自整角机式、感应式、永磁式(含直流、步进、磁阻式、同步式)等。克服了线圈式球形电机的许多缺点，永磁式球形电机占用空间小、系统效率高、磁能积高，在机器人、多向传动机构、制造业等多维空间伺服控制系统领域应用前景良好。
目前，电磁球形电机在本体结构设计、电磁和转矩分析与控制等方面普遍存在以下问题：1)磁场计算困难。球形电机磁场为三维磁场，异常复杂，目前球形电机磁场计算均基于理想化假设模型，还不能对磁场进行精确建模和计算。2)电磁耦合问题。球形电机各自由度间电磁耦合和力学耦合关系复杂，如何根据磁场模型，定量分析这些耦合关系，实现精准解耦，是球形电机设计与精确控制研究中急需解决的问题。3)新型球形电机的结构参数优化。必须以球形电机的精确建模为基础，以提高其输出转矩、减小尺寸、提高响应灵敏度和定位精度为目标，对球形电机本体结构参数进行优化设计。
为了解决上述难题，必须进行电磁驱动球形关节原理方面的创新。新球形电机必须便于建立准确的力学模型和运动模型，找出合适路径规划算法，提高电机的动态性能和稳定性，是对球形电机进行精密控制的基础，也是球形电机能够应用于精密工业领域的必然要求。
为了实现电磁驱动球型关节原理方面的创新，首先要突破空间万向旋转磁场技术。由于空间万向旋转磁场是三轴正交亥姆霍兹线圈产生的单一均匀旋转磁场，不存在磁场耦合问题，也不存在磁力耦合问题，磁极只受纯电磁驱动力矩作用，便于建立准确的力学模型和运动模型，因此，采用空间万向旋转磁场技术优势明显。但旋转磁场方位与旋转方向控制是关键。
为实现胶囊机器人在弯曲肠道环境中自由行走，国家发明专利“体内医疗微型机器人万向旋转磁场驱动控制方法”中(专利授权号：ZL 200810011110.2)，提出了旋转轴线可调的空间万向旋转磁场控制方法，并给出适用于空间第一象限的旋转磁场基本电流叠加公式。
为了实现旋转磁场轴线的万向可调，将基本电流叠加公式扩展到空间另七个象限，国家发明专利“空间万向叠加旋转磁场旋转轴线方位与旋向的控制方法”中(专利授权号：ZL201210039753.4)中，通过以空间某一固定轴线三个方向角为输入变量的基本电流叠加公式中三相正弦电流信号的反相位电流的组合驱动方式与三轴正交嵌套亥姆霍兹线圈装置内叠加的空间万向均匀旋转磁场的旋转轴方位和旋向的变化规律为基础，实现了空间万向旋转磁场旋转轴线方位与旋向在空间坐标系各个象限内的唯一性控制，在理论上解决通过数字化控制实现空间万向旋转磁矢量方位、旋向、强度、转速的任意调整的问题，为实现机器人的姿态调整与定向驱动行走奠定了基础。
为解决胶囊机器人在胃肠道中诊察时的姿态调整与行走两种运动方式相互分离的问题，国家发明专利“一种主被动双半球形胶囊机器人及其姿态调整与转弯驱动控制方法”(专利授权号：ZL 201510262778.4)中，利用球形结构的灵活性与万向性，避免了调姿时球形机器人发生滚动运动，结合空间万向旋转磁场的控制，可实现主、被动双半球结构胶囊机器人在体内自由进行姿态调整与转弯行走，研究表明，空间万向旋转磁场的方位与末端圆形轨迹误差直接影响机器人的控制精度。空间万向旋转磁场对双半球胶囊进行姿态调整与控制为两自由度球型机器人手腕研制奠定了基础。
为实现空间万向旋转磁场人机交互控制，国家发明专利“一种空间万向旋转磁场人机交 互控制方法”(专利授权号：ZL 201610009285.4)中，提出经纬坐标系内以侧摆与俯仰角两个姿态角度为输入变量的电流形式的空间万向旋转磁场叠加公式，
Figure PCTCN2020093737-appb-000001
其中
Figure PCTCN2020093737-appb-000002
其中θ、δ为机器人轴线侧摆角与俯仰角，I 0为三组正交亥姆霍兹线圈中正弦电流的幅值，ω为施加正弦信号电流的角频率，施加正弦信号电流的频率为f＝2π/ω。将空间万向旋转磁场的三维叠加问题转化为平面内的两维叠加问题，并通过两个操纵杆分别将侧摆与俯仰角度分离控制，实现低维度可分离变量交互式控制。三轴正交亥姆霍兹线圈的驱动是产生机器人轴线的侧摆角和俯仰角的方位可分离变量的空间万向旋转磁场控制模式，完全可以实现新型手腕侧摆角和俯仰角的控制。
为了实现电磁驱动球型关节原理方面的创新，还要解决均匀空间万向旋转磁场下更有效、快捷、准确的新型电磁驱动技术。在研究胶囊机器人姿态控制过程，发现在万向旋转磁场驱动下的径向磁化钕铁硼永磁体圆柱体轴线会发生旋转磁场同轴随动磁矩效应，即当钕铁硼圆柱体轴线与旋转磁场旋转轴线存在夹角时，旋转磁场的同轴随动磁矩将拉动钕铁硼圆柱体轴线向旋转磁场旋转轴线方向转动，直到重合为止。空间万向旋转磁场同轴随动磁矩可将永磁体轴线引导到空间任何方位，为球型关节姿态转换的电磁驱动奠定了基础。
为实现机器人运动关节的在线刚度调整功能，国内外科研人员进行多种结构设计,通过调查研究国内外变刚度柔性关节结构，变刚度柔性关节按结构原理分为杠杆机构、凸轮机构两类模型。德国宇航中心机器人及机电一体化协会，研制了一种基于凸轮机构的变刚度关节VS.Joint，利用关节旋转，带动凸轮滚子在底部凸轮盘内的位置变化，改变弹簧的压缩量，达到关节变刚度柔性输出；其第二代变刚度柔性关节(Floating spring joint，FSJ)并应用于新型DLR手臂系统中，该机构每个凹槽处由原来的一个凸轮滚子增加为两个，从而实现了低摩擦、低耗能，增大了承受负载的能力。意大利理工学院TSAGARAKIS等研制的变刚度驱动器CompAct—VSA，该机构利用齿轮齿条传动改变凸轮形状杠杆臂的旋转轴心所在的位置，凸轮通过滚子与弹簧作用，从而改变机构的输出刚度。总之，机械式变刚度调整机构体积较大，结构复杂，实际应用效果较差，如果能够摆脱复杂的机械结构，采用关节电磁驱动直接实现变刚度的线性化控制，则关节的柔顺控制动态性能将显著提高。
对上述机械式手腕所存在的机械结构复杂，机械摩擦力、变刚度控制、柔顺控制困难等局限性，结合旋转磁场同轴随动磁矩效应驱动原理，本发明提出一种通过同心内、外部万向节两个输出端(从动叉)同轴连接所构成随动机构内置径向磁化钕铁硼永磁体在空间万向旋转磁场同轴随动磁矩引导下实现随动机构输出端侧摆、俯仰的二自由度机器人高集成主动球型手腕机构及变刚度控制方法。在控制方面，是一种通过电磁驱动的前馈补偿途径实现该球型腕在接触作业条件下的变刚度及柔顺控制方法。通过电磁驱动的前馈补偿途径可实现主、被动腕功能，当通过侧摆、俯仰主动控制实现执行器末端定位后并拉住舱门；由于拉开舱门时，会出现机器人末端执行器运动轨迹与舱门转动圆轨迹的干涉，由于干涉时舱门对腕部的作用力方向已知，根据预知方向施加万向旋转磁场，施加力矩补偿，使腕子末端执行器的运动轨 迹在过腕部末端执行器作用力方向的平面内，使腕子变成松弛的被动腕，避开干涉，顺利实现舱门的开启等复杂作业。
据掌握的资料和立项查新显示，目前，国内外还没有采用空间万向旋转磁场同轴随动磁矩效应的新型电磁驱动球型手腕的相关资料报道，也没有通过电磁力矩控制实现主、被动腕工作模式的报道，因此，本发明具有较为突出的原创性。
发明内容
为解决上述为问题，本发明提供一种通过同心内、外部万向节两个输出端(从动叉)同轴连接所构成随动机构的内置径向磁化永磁体驱动器在空间万向旋转磁场同轴随动磁矩直接引导驱动下，实现输出端侧摆、俯仰二自由度主动球型手腕装置，还提供一种通过电磁直接驱动的前馈控制途径实现该球型腕在接触作业条件下的变刚度及柔顺控制方法。
本发明的技术方案是：
一种电磁驱动两自由度球型机器人手腕，包括三轴亥姆霍兹线圈组a和转子随动部分b；其中，三轴正交的亥姆霍兹线圈组a提供空间万向旋转磁场，转子随动部分b提供旋转磁场同轴随动磁矩驱动下侧摆和俯仰两个自由度转动；具体结构如下：
所述的转子随动部分b包括内部十字万向节d、外部十字万向节c以及固定端e；固定端e的顶部为固定端支承座5，固定端支承座5分为四个位于同一轴线的竖直支撑架，支撑架的上设有水平的通孔，中间两个竖直支撑架用于安装内部十字万向节d，外端两个竖直支撑架用于安装外部十字万向节c；
所述的内部十字万向节d包括固定端支承座5中间两个竖直支撑架(主动叉)，内部万向节内环14和柱形壳体2，其中，内部万向节内环14作为十字轴支架，柱形壳体2作为从动叉；内部万向节内环14的两侧分别通过深沟球轴承a15和深沟球轴承b16安装在与固定端支承座5上中间的两个竖直支撑架的通孔中，固定端支承座5和内部万向节内环14实现相对转动，形成俯仰转角转轴；柱形壳体2位于内部万向节内环14内，连接轴d23和连接轴e26的一端分别对称固定在柱形壳体2的两侧，另一端分别通过深沟球轴承c24和深沟球轴承d25安装在内部万向节内环14内侧，实现柱形壳体2和内部万向节内环14相对转动，形成侧摆角转轴；径向磁化永磁体1通过轴承31安装于柱形壳体2内；
所述的外部十字万向节c包括固定端支承座5外端两个竖直支撑架(主动叉)，外部万向节内环3和外部万向节外环17，其中，外部万向节内环3作为十字轴支架，外部万向节内环3上对称设有四个水平的同轴通孔(十字轴孔)，外部万向节外环17作为从动叉；连接轴a7和连接轴b9分别通过法兰轴承a8和法兰轴承b10安装在固定端支承座5外端两个竖直支撑架的通孔中；外部万向节内环3的两侧同轴通孔分别通过普通平键a6和普通平键b11与连接轴a7和连接轴b9固定连接，固定端支承座5和外部万向节内环3实现相对转动，形成俯仰角转轴；连接轴a7外端与编码器a4连接，连接轴b9一端与阻尼器a12连接，另一端与制动器a13连接，且编码器a4、阻尼器a12和制动器a13均固定在固定端支承座5上；连接轴c21和连接轴f28分别通过法兰轴承c22和法兰轴承d27安装在外部万向节内环3另外两侧的同轴通孔中；外部万向节外环17由两个半环形结构的支撑杆对称组成，两个支撑杆的一端分别通过普通平键c20和普通平键d29与连接轴c21和连接轴f28固定连接，且支撑杆的端部位于外部万向节内环3外部，两个支撑杆的另一端固定在输出端33的两侧；外部万向节外环 17和外部万向节内环3实现相对转动，形成侧摆角转轴；连接杆32的一端固定在柱形壳体2的顶部，另一端与输出端33固定连接；连接轴c21的两端分别与编码器b18和制动器b19连接，连接轴f28的外端与阻尼器b30连接，且编码器b18、制动器b19和阻尼器b30均固定安装在外部万向节内环3外侧；
所述的三轴亥姆霍兹线圈组a包括大线圈组、小线圈组和中间线圈组，每组包括两个完全相同的线圈，对称布置；三组线圈的轴线相互垂直，且三组线圈相互固定，其中大线圈组的底部固定在固定端e上，且中间线圈组的轴线与固定端e的轴线重合；内部十字万向节d位于三组线圈中间的内部空间内，外部十字万向节c位于三组线圈外部；所述的外部十字万向节c、三轴亥姆霍兹线圈组a、内部十字万向节d在空间上形成三层嵌套结构。
本发明的效果和益处是：
本发明的一种新型电磁驱动两自由度球型机器人手腕的内、外部万向节两个输入端、输出端分别同轴并联，内、外部万向节具有同一转动中心，因此构成球型腕，实现了手腕两个自由度的运动解耦，侧摆、俯仰角度可单独测量与控制。内、外部万向节均采用空心结构，可显著增加内部可嵌套容纳空间，手腕多层嵌套结构紧凑。手腕输出端连接的末端执行器侧摆、俯仰角度可控，但自转角度始终不发生偏转，可方便的调整末端执行器的法方向，完成腕部定位。
本发明克服了复杂传动机械手腕的弊端，手腕传动系统结构简单轻便、传动效率高、系统静态及动态性能好、控制响应速度快。由于传动链简单且无机械间隙，因此定位精度高。由于没有复杂机械传动系统非线性摩擦力，可通过电磁直接驱动快捷的实现手腕关节的变刚度控制以及柔顺控制。
本发明克服了现有球形电磁驱动关节三维复杂磁场的建模难题，可实现磁场精确建模和计算，为定量分析电磁驱动关节各自由度间电磁耦合和力学耦合关系，实现精准解耦和结构参数优化，最终可望实现电磁驱动球形关节控制的响应灵敏度和定位精度。
附图说明
图1是本发明机器人手腕结构示意图。
图2是本发明机器人手腕转子随动部分示意图。
图3(A)是本发明机器人手腕俯仰传动机构截面示意图。
图3(B)是本发明机器人手腕俯仰传动机构截面示意图Ⅰ处局部放大图。
图3(C)是本发明机器人手腕俯仰传动机构截面示意图Ⅱ处局部放大图。
图3(D)是本发明机器人手腕侧摆传动机构截面示意图。
图3(E)是本发明机器人手腕侧摆传动机构截面示意图Ⅲ处局部放大图。
图3(F)是本发明机器人手腕侧摆传动机构截面示意图Ⅳ处局部放大图。
图3(G)是本发明机器人手腕侧摆传动机构截面示意图Ⅴ处局部放大图。
图3(H)是本发明机器人手腕侧摆传动机构截面示意图Ⅵ处局部放大图。
图4(A)是本发明机器人手腕轴线由固定坐标系到赖柴坐标系转换过程示意图。
图4(B)是本发明机器人手腕轴线向量和空间万向旋转磁场旋转轴线向量的空间位置示意图。
图4(C)是本发明机器人手腕同轴随动磁矩效应驱动模型示意图。
图4(D)是本发明机器人手腕同轴随动磁矩计算坐标系建立示意图。
图5是本发明机器人手腕主被动模式控制原理示意图。
图中：a三轴亥姆霍兹线圈组；b转子随动部分；c外部十字万向节；d内部十字万向节；e固定端；f末端执行器；g力传感器；h两自由度机器人手腕。
1径向磁化永磁体；2柱形壳体；3外部万向节内环；4编码器a；5固定端支承座；6普通平键a；7连接轴a；8法兰轴承a；9连接轴b；10法兰轴承b；11普通平键b；12阻尼器a；13制动器a；14内部万向节内环；15深沟球轴承a；16深沟球轴承b；17外部万向节外环；18编码器b；19制动器b；20普通平键c；21连接轴c；22法兰轴承c；23连接轴d；24深沟球轴承c；25深沟球轴承d；26连接轴e；27法兰轴承d；28连接轴f；29普通平键d；30阻尼器b；31轴承；32连接杆；33输出端。
具体实施方式
以下结合技术方案和附图详细叙述本发明的具体实施例。
如图1所示，本发明的两自由度球型机器人手腕h，包括三轴亥姆霍兹线圈组a和转子随动部分b。三轴正交的亥姆霍兹线圈组a提供空间万向旋转磁场，转子随动部分b提供旋转磁场同轴随动磁矩驱动下侧摆和俯仰两个自由度转动；工作原理采用空间万向旋转磁场同轴随动磁矩效应。
结合图2、3(A)～3(C)、3(D)～3(H)说明本发明的新型电磁驱动两自由度球型机器人手腕转子随动部分b的构成。
转子随动部分b包括内部十字万向节d(内安装有转子永磁体，即径向磁化永磁体1)、外部十字万向节c(安装有制动机构、阻尼机构、测量机构等)以及固定端e。内部十字万向节d和外部十字万向节c的转动中心相同，即手腕转动中心，构成球型腕，实现了两个自由度转动的解耦，可以实施侧摆角度和俯仰角度的单独测量与控制；内部十字万向节d和外部十字万向节c均采用空心结构，以增加内部可容纳空间。
内部十字万向节d和外部十字万向节c均采用固定端支承座5为输入端(主动叉)，保证两个输入端同轴；外部十字万向节c输出端33(从动叉)和内部十字万向节d的输出端即连接杆32(从动叉)也同轴连接，则构成手腕转子随动部分b。
转子随动部分b轴线即为手腕转动轴线，手腕转子随动部分b轴线可实现侧摆、俯仰两自由度定点(手腕转动中心)旋转运动，径向磁化永磁体1安装在转子随动部分b内并可以随旋转磁场自由旋转，以外旋转磁场同轴随动磁矩为动力媒介驱动并实现手腕侧摆与俯仰转向运动。
外部十字万向节c包括：固定端支承座5外端两个竖直支撑架(主动叉)，外部万向节内环3(十字轴支架)和外部万向节外环17(从动叉)。外部万向节内环3为整体的环形结构，圆周均匀分布四个孔(十字轴孔)；外部万向节外环17由两个半环形结构支撑杆对称组成，两个半环形结构支撑杆顶端均匀分布两个同轴孔。
与外部十字万向节c输出端33连接的末端执行器f姿态是由转子随动部分b轴线的侧摆与俯仰角度决定，由于外部十字万向节c输入端，即固定端支承座5不能旋转，末端执行器f姿态与转子随动部分b轴线保持一致，因此，末端执行器f自转角度也不发生偏转，可方便的调整机器人末端执行器f的法方向，完成腕部定位。末端执行器f上可以安装力传感器g。
见图3(A)～3(C)，固定端支承座5(相当于主动叉)和外部万向节内环3可实现相对转动，俯仰角转轴的装配过程是：外部万向节内环3通过普通平键a6与连接轴a7固连，固定端支承座5外端一个竖直支撑架通过法兰轴承a8与连接轴a7连接；外部万向节内环3通过普通平键b11与连接轴b9固连，固定端支承座5外端另一个竖直支撑架通过法兰轴承b10与连接轴b9连接。
见图3(D)～3(H)，外部万向节外环17(相当于从动叉)和外部万向节内环3可实现相对转动，侧摆角转轴的装配过程是：外部万向节外环17通过普通平键c20与连接轴c21固连，外部万向节内环3通过法兰轴承c22与连接轴c21连接；外部万向节外环17通过普通平键d29与连接轴f28固连，外部万向节内环3通过法兰轴承d27与连接轴f28连接。
内部十字万向节d包括：固定端支承座5中间两个竖直支撑架(主动叉)，内部万向节内环14(十字轴)和柱形壳体2(从动叉)三部分；内部万向节内环14相当于十字轴支架。
见图3(A)～3(C)，固定端支承座5中间两个竖直支撑架和内部万向节内环14可实现相对转动，俯仰转角转轴的装配过程是：内部万向节内环14通过深沟球轴承a15、深沟球轴承b16与固定端支承座5中间两个竖直支撑架连接。
见图3(D)～3(H)，柱形壳体2和内部万向节内环14可实现相对转动，侧摆角转轴的装配过程是：连接轴d23一端固结于柱形壳体2，另一端通过深沟球轴承c24与内部万向节内环14连接；连接轴e26一端固结于柱形壳体2，另一端通过深沟球轴承d25与内部万向节内环14连接。
转子随动部分b通过外部十字万向节c和内部十字万向节d构成的特征是：内、外部十字万向节的转动中心相同(即手腕转动中心)，外部十字万向节c和内部十字万向节d的输入端(主动叉)、输出端(从动叉)分别同轴固接，因此构成球型腕，实现了两个自由度转动的解耦，进而，可以实施侧摆角度和俯仰角度的单独测量与控制，外部十字万向节c和内部十字万向节d均采用空心结构，以增加内部可容纳空间；外部十字万向节c和内部十字万向节d的输入端(主动叉)均为固定端支承座5，相当于外部十字万向节c和内部十字万向节d的输入端同轴固定连接。外部十字万向节c和内部十字万向节d的输出端(从动叉)采用同轴连接，即外部十字万向节外环17和柱形壳体2的同轴连接过程是：连接杆32两端分别与柱形壳体2和输出端33固结，输出端33与外部十字万向节外环17固结。径向磁化永磁体1通过轴承31安装于柱形壳体2内，径向磁化永磁体1可实现相对转子随动部分b的同轴自转。
外部十字万向节c和内部十字万向节d两个输入端(主动叉)同轴连接的前提下，外部十字万向节c和内部十字万向节d两个输出端(从动叉)通过同轴连接构成手腕的转子随动部分b，转子随动部分b轴线即为手腕转动轴线，可实现侧摆、俯仰两自由度定点(手腕转动中心)旋转运动，径向磁化永磁体1在空间万向旋转磁场的同轴随动磁矩驱动下，实现手腕侧摆、俯仰两自由度定点运动。
手腕姿态的检测与控制方法如下：
转子随动部分b只存在一个固定点(手腕转动中心)，还需要对转子随动部分b转轴方位进行控制。具体通过对外部万向节d各部分相对运动的检测与控制实现手腕轴线方位的控制。外部十字万向节c由固定端支承座5外端两个竖直支撑架，外部万向节内环3和外部万 向节外环17三部分相对运动实现手腕轴线的万向转动。由于外部万向节内环3为圆周均匀分布四个孔(十字轴孔)的整体环形结构；外部万向节外环17由顶端均匀分布两个同轴孔的两个半环形结构支撑杆对称组成，因此，可以连接如下:
外部万向节内环3(十字轴支架)一组两个同轴孔和固定端支承座5外端两个竖直支撑架(主动叉)连接形成俯仰角转轴(一个十字轴)，外部万向节内环3可绕轴线旋转，在外部万向节内环3和固定端支承座5外端两个竖直支撑架转轴之间分别安装绝对编码器a4、制动器a13、阻尼器a12，则编码器a4可测量外部万向节内环3和固定端支承座5外端两个竖直支撑架之间相对转角即为手腕俯仰角度；外部万向节内环3另一组两个同轴孔和外部万向节外环17两个半环形结构支撑杆的两个孔同轴连接形成另一个侧摆角转轴(另一个十字轴)，外部万向节外环17相对外部万向节内环3可绕轴线旋转，在外部万向节内环3和外部万向节外环17转轴之间分别安装绝对编码器b18、制动器b19、阻尼器b30，则编码器b18可测量外部万向节内环3和外部万向节外环17之间相对转角即为手腕侧摆角度。
安装于外部十字万向节c两组垂直旋转轴处的两个绝对编码器b18和绝对编码器a4，可实现对侧摆与俯仰转角的实时测量，并传输给控制系统，以实现对侧摆与俯仰角度动的准确控制。
制动器a13、制动器b19均为电磁制动器，实现对手腕俯仰与侧摆两个自由度的锁定，当手腕静止时，制动器a13、制动器b19实现对外部十字万向节d的锁定，以固定转子随动部分b方位，防止随意摆动发生意外事故；当手腕旋转时，制动器a13、制动器b19解除对外部十字万向节d的锁定，以实现转子随动部分b与万向旋转磁场的随动，即实现侧摆与俯仰转动的驱动。当只锁定外部万向节一个转轴时，手腕就变成单个自由度转动手腕，两个自由度运动相互独立，互不影响，可实现独立检测与控制，实现手腕侧摆与俯仰两种单自由度控制模态。
阻尼器a12和阻尼器b30安装于外部十字万向节d两十字旋转轴关节处(俯仰与侧摆转轴)，为手腕的俯仰、侧摆转动提供阻尼，以便减缓侧摆与俯仰姿态调整时手腕的振动。
当腕子完成定位与抓紧后，通过旋转磁场同轴随动磁矩的主动驱动控制，可解除腕部俯仰和侧摆的约束，使腕部变成柔顺性被动腕，有效解除机械干涉，满足空间极限环境对机器人腕部的特殊需求，完成旋转安装、拉开舱门等复杂作业。
结合图3(A)～3(C)说明本发明的新型电磁驱动两自由度球型机器人手腕俯仰运动的检测与控制的实现。
俯仰转角运动测量的实现过程是：外部万向节内环3通过普通平键a6与连接轴a7固连，固定端支承座5(外部十字万向节c的主动叉)通过法兰轴承a8与连接轴a7连接，实现了外部万向节内环3和固定端支承座5的相对转动；编码器a4固结于固定端支承座5并与连接轴a7相连接，实现俯仰转角测量。
俯仰转角运动控制的实现过程是：外部万向节内环3通过普通平键b11与连接轴b9固连，固定端支承座5通过法兰轴承b10与连接轴b9连接，实现了外部万向节内环3和固定端支承座5的相对转动；阻尼器a12固结于固定端支承座5并与连接轴b9相连，实现俯仰转角阻尼特性的改变，以减小振动现象；制动器a13固结于固定端支承座5并与连接轴b9相连，实现俯仰转角锁定。此部分结构实现了俯仰运动制动、测量、改变阻尼特性的功能。
结合图3(D)～3(H)说明本发明的新型电磁驱动两自由度球型机器人手腕侧摆运动的检测与控制的实现。
侧摆转角运动测量的实现过程是：外部万向节外环17通过普通平键c20与连接轴c21固连，外部万向节内环3通过法兰轴承c22与连接轴c21连接，实现了外部万向节外环17和外部万向节内环3的相对转动；编码器b18固结于外部万向节内环3并与连接轴c21相连，实现侧摆转角测量。
侧摆转角运动控制的实现过程是：外部万向节外环17通过普通平键d29与连接轴f28固连，外部万向节内环3通过法兰轴承d27与连接轴f28连接，实现了外部万向节外环17和外部万向节内环3的相对转动；阻尼器b30固结于外部万向节内环3并与连接轴f28相连，实现侧摆转角阻尼特性的改变，以减小振动现象；制动器b19固结于外部万向节内环3并与连接轴c21相连，实现侧摆转角锁定。此部分结构实现了侧摆运动制动、测量、改变阻尼特性的功能。
结合图4(A)、4(B)、4(C)、4(D)说明本发明的新型电磁驱动两自由度球型机器人手腕的工作原理。
首先，结合图4(A)说明本发明机器人手腕轴线俯仰角与侧摆角可以分别独立测量的原因。图4(A)中建立坐标系如下：固定坐标系Oxyz与三轴亥姆霍兹线圈组a固结，手腕轴线初始位置垂直向上，其中Oz轴与外部十字万向节c连接编码器a4的俯仰角旋转轴重合，其中Ox轴与外部十字万向节c连接编码器b18的侧摆角旋转轴重合。
赖柴坐标系Ox 1y 1z 1由固定坐标系Oxyz经过两次旋转得到，固定坐标系Oxyz首先绕Oz轴旋转俯仰角θ，得到中间坐标系Ox 1y’z，则与外部十字万向节c连接的编码器a4可测得俯仰角θ，Ox 1轴始终与外部十字万向节c连接编码器b18的侧摆角旋转轴重合，中间坐标系Ox 1y’z绕Ox 1轴再旋转侧摆角δ，得到赖柴坐标系Ox 1y 1z 1，则与外部十字万向节c连接编码器b18可测得侧摆角δ，Oy 1即为两次旋转后手腕轴线的新方位，可见，通过固定坐标系Oxyz到赖柴坐标系Ox 1y 1z 1的两个旋转过程，结合外部十字万向节c上引起的两个相互垂直的俯仰角转轴和侧摆角转轴的结构解耦特性，证明了手腕轴线空间方位的俯仰角θ、侧摆角δ可由与外部十字万向节c连接的编码器a4和编码器b18分别直接测得。
下面结合图4(B)、4(C)、4(D)证明本发明机器人手腕的同轴随动磁矩效应驱动原理，并推导同轴随动磁矩公式。
采用图4(A)中赖柴坐标系Ox 1y 1z 1变换过程所采用的俯仰角θ、侧摆角δ来描述手腕轴线和空间万向旋转磁场旋转轴线在固定坐标系Oxyz内的空间方位，略去电机结构，可得图4(B)中径向磁化永磁体1轴线方向向量n 2(θ 0，δ 0)(手腕轴线向量)和空间万向旋转磁场旋转轴线向量n 3(θ 3，δ 3)在固定坐标系的任意空间位置，O a，O b分别为向量n 2和向量n 3端点在平面Oxy的投影。向量n 2和向量n 3空间夹角为α。
图4(C)是手腕同轴随动磁矩效应驱动模型图。可由图4(B)中向量n 2和向量n 3构成的平面截取获得，驱动模型是磁矩为m的径向磁化永磁体1(旋转轴为n 2)在旋转磁场B(旋转轴为n 3)内同时以角速度ω旋转的相对运动关系，其中，通过三轴亥姆霍兹线圈组a产生空间万向旋转磁场旋转轴线向量n 3(θ 3，δ 3)固定，分别通过外部十字万向节c上的制动器a13和制动器b19实现俯仰转角θ 0和侧摆转角δ 0锁定，则径向磁化永磁体1轴线方向向量n 2(θ 0， δ 0)也固定，径向磁化永磁体1只能随空间万向旋转磁场以速度ω自转，Ta为以速度ω自转空间万向旋转磁场对以速度ω旋转的径向磁化永磁体1产生的同轴随动磁矩，以下证明同轴随动磁矩作用方向是由磁铁磁矩矢量m旋转平面向磁矢量B旋转平面翻转，即同轴随动磁矩使磁矩为m的径向磁化永磁体1的旋转轴n 2向磁矢量B旋转轴线向量n 3方向转动，直到重合为止。
图4(D)是本发明机器人手腕同轴随动磁矩计算坐标系建立示意图，旋转磁场所在固定坐标系Ox 3y 3z 3与磁矩旋转矢量m所在固定坐标系Ox 2y 2z 2建立如下：分别以向量n 2、n 3为Oy 2、Oy 3轴，分别以磁场旋转平面与磁矩矢量m的旋转平面交线为Oz 2、Oz 3轴，O即为两个固定坐标系原点。
旋转磁场所在坐标系Ox 3y 3z 3由磁矩旋转矢量m所在坐标系Ox 2y 2z 2绕Oz 2旋转-α角得到，则旋转磁场所在坐标系Ox 3y 3z 3到磁矩旋转矢量m所在坐标系Ox 2y 2z 2之间的变换矩阵为
Figure PCTCN2020093737-appb-000003
ob为单位旋转磁矢量在坐标系Ox 3y 3z 3下坐标为(cos(ωt)，0，-sin(ωt))，om 1为单位磁矩矢量在坐标系Ox 2y 2z 2坐标为(cos(ωt-δ 1)，0，-sin(ωt-δ 1))，δ 1为磁矩m相对旋转磁场B的转差角。
可得ob在坐标系Ox 2y 2z 2下坐标为
Figure PCTCN2020093737-appb-000004
根据矢量外积公式
Figure PCTCN2020093737-appb-000005
转差角一般很小，令δ 1＝0时
Figure PCTCN2020093737-appb-000006
Figure PCTCN2020093737-appb-000007
Figure PCTCN2020093737-appb-000008
式中m 0，B 0为磁矩矢量与磁矢量大小。
由上式可得T x2，T y2，T z2均为周期函数，周期分别为
Figure PCTCN2020093737-appb-000009
由于α为定值，因此单个周期内平均力矩为
Figure PCTCN2020093737-appb-000010
由式(2)可知，同轴随动磁矩只沿着Oz 2轴，沿着Ox 2和Oy 2的磁矩均为0，即同轴随动磁矩只作用于磁铁磁矩矢量m旋转轴n 2和磁矢量B旋转轴n 3构成的旋转平面内，并由磁铁磁矩矢量m旋转平面向磁矢量B旋转平面翻转，因此，同轴随动磁矩计算公式可简化为：
Figure PCTCN2020093737-appb-000011
式中，α角为磁矩为m永磁圆柱体轴线与旋转磁场B旋转轴线之间的夹角，m 0，B 0为磁矩矢量与旋转磁矢量幅值。
当手腕驱动磁矩矢量由径向磁化永磁体1提供时，每个周期内相当于永磁体只受延Oz 2轴负向的磁力矩，在此磁力矩作用下，磁铁磁矩矢量m旋转平面向磁矢量B旋转平面翻转，即永磁体轴线向旋转磁场轴线靠近，该磁矩矢量即为永磁体同轴随动磁矩，该现象称为旋转磁场同轴随动磁矩效应，空间万向旋转磁场同轴随动磁矩效应可将永磁体轴线引导到空间任何方位，如果分别通过外部十字万向节c制动器a13和制动器b19解除俯仰转角θ 0和侧摆转角δ 0锁定，则径向磁化永磁体1轴线方向向量n 2(θ 0，δ 0)不仅能随空间万向旋转磁场以速度ω自转，还能带动转子随动部分b向空间万向旋转磁场旋转轴线向量n 3(θ 3，δ 3)转动。完全可以将同轴随动磁矩用于球型关节的电磁驱动，这就是球型关节电磁驱动的理论依据。
下面结合图4(C)、图5说明实现新型电磁驱动两自由度球型机器人手腕如何实现手腕关节同轴随动磁矩控制的具体实施方式。
首先，假设在末端执行器f端部作用力矢量F与末端执行器f轴线所构成的平面内，F对手腕转动中心产生的力矩方向与同轴随动磁矩方向必然相反，此时，一种电磁驱动两自由度球型机器人手腕是一种直接电磁驱动的球形主动关节，电磁驱动原理是旋转磁场同轴随动磁矩效应，由于同轴随动磁矩只作用于磁铁磁矩矢量m旋转轴n 2和磁矢量B旋转轴n 3构成的旋转平面内，并由磁铁磁矩矢量m旋转平面和磁矢量B旋转平面翻转，显然，末端执行器f端部作用力矢量F也在旋转轴n 2和旋转轴n 3构成的旋转平面内，(3)式即为同轴随动磁矩计算公式。(3)式表明，手腕同轴随动磁矩即可以通过三组正交亥姆霍兹线圈中正弦电流的幅值I 0控制，也可以通过夹角α进行控制，还可以同时控制来提高磁矩。
即当F较大时，夹角α变化很大，由于力矩调整范围较大，永磁体同轴随动磁矩大小可 同时通过三组正交亥姆霍兹线圈中正弦电流的幅值I 0和永磁圆柱体轴线与旋转磁场轴线夹角α进行控制，以便增加力矩调整范围，使手腕变成柔顺腕。由于没有复杂机械传动系统摩擦力，可通过电磁直接驱动快捷实现力矩控制。
下面结合图4(C)、图5说明实现新型电磁驱动两自由度球型机器人手腕如何实现手腕关节变刚度控制的具体实施方式。
首先，在数学上推导同轴随动磁矩驱动关节的刚度计算公式，假设在图5中末端执行器f端部作用力矢量F与末端执行器f轴线所构成的平面内，此时，F对手腕转动中心产生的力矩方向与同轴随动磁矩方向必然相反，则电磁驱动球型关节的刚度是：
Figure PCTCN2020093737-appb-000012
式中，s为末端执行器f端部沿着作用力方向的变形，L为执行器末端作用力F到电磁驱动球型关节中心的距离，则有，s＝Lα，α为磁矩为m径向磁化永磁体1轴线与旋转磁场B轴线的夹角，假设α初始数值为零，如图4(C)所示。
末端执行器f端部作用力F产生的力矩应该等于旋转磁场同轴随动磁矩，即
Figure PCTCN2020093737-appb-000013
将(5)代入(4)得
Figure PCTCN2020093737-appb-000014
此时，由于夹角α很小，所以，
Figure PCTCN2020093737-appb-000015
则
Figure PCTCN2020093737-appb-000016
(6)式表明，新型电磁驱动球型关节的刚度，可以通过旋转磁矢量幅值B 0进行线性控制，即可通过三组正交亥姆霍兹线圈中正弦电流的幅值I 0进行控制，由于没有复杂机械传动系统摩擦力，避免了复杂的变刚度机械调整机构，可通过电磁直接驱动快捷、便利的实现关节变刚度控制，控制精度显著提高，显然，当夹角α变化很小时，(6)式才成立。即当F较小时，夹角α变化很小，可以按照(6)式直接控制手腕刚度，此时，可以只通过正弦电流的幅值I 0进行控制，使手腕变成柔顺腕。
结合附图1、2说明新型电磁驱动两自由度球型机器人手腕的工作过程。
新型电磁驱动手腕作业前姿态零点标定过程是：通过三轴亥姆霍兹线圈组a产生旋转轴线垂直的空间万向旋转磁场，在同轴随动磁矩驱动下，转子随动部分b与固定端e的轴线重合，此时，俯仰转角的编码器a4和侧摆转角的编码器b18相对转角为零，此时分别给编码器a4和编码器b18上电，便存储并记忆两自由度解耦手腕的零点位置；当两自由度手腕定位时，驱动侧摆与俯仰使两自由度手腕处于主动腕模式，根据公式(3)的同轴随动磁矩控制系统与编码器a4和编码器b18构成转角位置闭环控制，通过实时感知与记忆两自由度手腕的侧摆、俯仰位置，提高控制精度。
新型电磁驱动手腕两自由度主动模态工作过程是：
第一步，通电前，制动器a13与制动器b19一直锁定外部十字万向节c，无法进行侧摆、俯仰运动。
第二步，根据目标空间方位，确定应该施加空间万向旋转磁场的旋转轴线方向，依据公式(1)向三轴亥姆霍兹线圈组a通入三组等频交流电，产生相应方位的空间旋转磁场。
第三步，径向磁化永磁体1在旋转磁场的作用开始进行自转，并依据公式(3)产生同轴随动磁矩，但由于制动器a13与制动器b19对外部十字万向节c两自由度的锁定，转子随动部分b无法进行侧摆、俯仰运动。
第四步，制动器a13与制动器b19通电解除对外部十字万向节c的锁定，径向磁化永磁体1在旋转磁场同轴随动磁矩作用下，转子随动部分b轴线追随旋转磁场轴线进行侧摆、俯仰运动，俯仰转角通过编码器a4测量，偏转角度通过编码器b18测量，运动过程由阻尼器a12与阻尼器b30提供阻尼，防止发生振动。
第五步，通过编码器4a与编码器b18实时反馈俯仰、侧摆角度信息；根据反馈的角度信息，依据公式(3)对同轴随动磁矩进行反馈控制，直到满足精度为止，手腕到达目标位置，实现两自由度运动的控制。
第六步，三轴亥姆霍兹线圈组a断电，制动器a13与制动器b19断电，再次对外部十字万向节c锁定，以固定机器人手腕方位。
当只锁定外部十字万向节c一个转轴时，手腕就变成单个自由度转动手腕，两个自由度运动相互独立，互不影响，可实现独立检测与控制，实现手腕侧摆与俯仰两种单自由度控制模态。单自由度模态稳定性好，控制变量少，用于位置精确控制。其它步骤相同，以上第四步、在第五步分别按照如下控制，可实现单自由度控制模态。
新型电磁驱动手腕单自由度主动模态工作过程是：
第四步，只对制动器a13通电解除外部十字万向节c的单轴锁定，径向磁化永磁体1在旋转磁场同轴随动磁矩作用下，转子随动部分b轴线追随旋转磁场轴线进行侧摆运动，偏转角度通过编码器b18测量；或者只对制动器b19通电解除对外部十字万向节c的单轴锁定，径向磁化永磁体1在旋转磁场同轴随动磁矩作用下，转子随动部分b轴线追随旋转磁场轴线进行侧摆运动，俯仰转角度通过编码器a4测量。
第五步，通过编码器a4或者编码器b18实时反馈俯仰或者侧摆角度信息；根据反馈的角度信息，依据公式(3)对同轴随动磁矩进行反馈控制，直到满足精度为止，手腕到达目标位置，分别实现单自由度运动的控制。
下面结合图5说明实现新型电磁驱动两自由度球型机器人手腕的主、被动模式变刚度与柔顺控制的具体实施方式。
两自由度机器人手腕h的转子随动部分b具有侧摆与俯仰驱动功能，可以实现腕部末端执行器f在固定端e轴线的任意平面内的俯仰摆动，考虑到拉开舱门时，能避开腕部末端执行器f轨迹与舱门运动轨迹发生干涉，在机器人腕部末端执行器f上安装一个力传感器g，同轴随动磁矩控制系统与力传感器g检测到的力F构成闭环控制，根据力F的大小，即当F很大时，夹角α变化很大，按照公式(3)通过同轴随动电磁驱动力矩控制，即使腕部输出端在检测力平面内沿受力方向直接减少正弦电流的幅值I 0和通过空间万向旋转磁场方向改变夹角α并使其减少，保证腕部末端执行器f的运动轨迹在过末端执行器f轴线和力F组成的平面内 沿力F的方向摆动；当F很小时，夹角α变化很小，则可按照公式(6)直接减少正弦电流的幅值I 0，就可以控制两自由度机器人手腕h的刚度减小，实现腕部末端执行器f在所受力F的平面内沿着所受力F的方向运动，同轴随动磁矩控制系统与力传感器g检测到的力F通过闭环控制并追随力F的方向摆动，当力传感器g的检测到的力F值小到0.1N以下，就能实现完全柔顺被动腕，提高腕部的灵活性，保护腕部拉开舱门时不受损坏。同理，当力F的方向改变时，但F很大时，夹角α变化很大，依据公式(3)控制同轴随动磁矩改变力矩方向与大小，即直接减少正弦电流的幅值I 0并使腕部输出端在检测力平面内沿受力方向改变夹角α并使其减少；当F很小时，α角变化很小，公式(6)成立，则按照公式(6)直接减少正弦电流的幅值I 0，实现变刚度控制，保护手腕。两自由度机器人手腕h采用被动腕模式作业时，侧摆、俯仰的位置依然可以绝对编码器a4与绝对编码器b18存储记忆，两自由度机器人手腕h作业完成恢复到主动腕时，可以恢复到零点标定位置。
通过两自由度机器人手腕h变刚度控制，可以解除腕部俯仰和侧摆的约束，使腕部变成被动腕模式，当停止电磁力矩驱动时，手腕变成柔顺的绳子，实现完全柔顺，有效的解除机械干涉，满足空间极限环境对机器人腕部的特殊需求，完成外星球采样时拔出石头和航天器舱门拉开等复杂作业。

Claims (2)

  1. 一种电磁驱动两自由度球型机器人手腕，其特征在于，所述的电磁驱动两自由度球型机器人手腕包括三轴亥姆霍兹线圈组(a)和转子随动部分(b)；其中，三轴亥姆霍兹线圈组(a)提供空间万向旋转磁场，转子随动部分(b)提供旋转磁场同轴随动磁矩驱动下侧摆和俯仰两个自由度转动；具体结构如下：
    所述的转子随动部分(b)包括内部十字万向节(d)、外部十字万向节(c)以及固定端(e)；固定端(e)的顶部为固定端支承座(5)，固定端支承座(5)分为四个位于同一轴线的竖直支撑架，支撑架的上设有水平的通孔，中间两个竖直支撑架用于安装内部十字万向节(d)，外端两个竖直支撑架用于安装外部十字万向节(c)；
    所述的内部十字万向节(d)包括固定端支承座(5)中间两个竖直支撑架、内部万向节内环(14)和柱形壳体(2)，其中，内部万向节内环(14)作为十字轴支架，柱形壳体(2)作为从动叉；内部万向节内环(14)的两侧分别通过深沟球轴承a(15)和深沟球轴承b(16)安装在与固定端支承座(5)上中间的两个竖直支撑架的通孔中，固定端支承座(5)和内部万向节内环(14)实现相对转动，形成俯仰转角转轴；柱形壳体(2)位于内部万向节内环(14)内，连接轴d(23)和连接轴e(26)的一端分别对称固定在柱形壳体(2)的两侧，另一端分别通过深沟球轴承c(24)和深沟球轴承d(25)安装在内部万向节内环(14)内侧，实现柱形壳体(2)和内部万向节内环(14)相对转动，形成侧摆角转轴；径向磁化永磁体(1)通过轴承(31)安装于柱形壳体(2)内；
    所述的外部十字万向节(c)包括固定端支承座(5)外端两个竖直支撑架、外部万向节内环(3)和外部万向节外环(17)，其中，外部万向节内环(3)作为十字轴支架，外部万向节内环(3)上对称设有四个水平的同轴通孔，外部万向节外环(17)作为从动叉；连接轴a(7)和连接轴b(9)分别通过法兰轴承a(8)和法兰轴承b(10)安装在固定端支承座(5)外端两个竖直支撑架的通孔中；外部万向节内环(3)的两侧同轴通孔分别通过普通平键a(6)和普通平键b(11)与连接轴a(7)和连接轴b(9)固定连接，固定端支承座(5)和外部万向节内环(3)实现相对转动，形成俯仰角转轴；连接轴a(7)外端与编码器a(4)连接，连接轴b(9)一端与阻尼器a(12)连接，另一端与制动器a(13)连接，且编码器a(4)、阻尼器a(12)和制动器a(13)均固定在固定端支承座(5)上；连接轴c(21)和连接轴f(28)分别通过法兰轴承c(22)和法兰轴承d(27)安装在外部万向节内环(3)另外两侧的同轴通孔中；外部万向节外环(17)由两个半环形结构的支撑杆对称组成，两个支撑杆的一端分别通过普通平键c(20)和普通平键d(29)与连接轴c(21)和连接轴f(28)固定连接，且支撑杆的端部位于外部万向节内环(3)外部，两个支撑杆的另一端固定在输出端(33)的两侧；外部万向节外环(17)和外部万向节内环(3)实现相对转动，形成侧摆角转轴；连接杆(32)的一端固定在柱形壳体(2)的顶部，另一端与输出端(33)固定连接；连接轴c(21)的两端分别与编码器b(18)和制动器b(19)连接，连接轴f(28)的外端与阻尼器b(30)连接，且编码器b(18)、制动器b(19)和阻尼器b(30)均固定安装在外部万向节内环(3)外侧；
    所述的外部十字万向节(c)和内部十字万向节(d)两个输入端同轴连接的前提下，外部十字万向节(c)和内部十字万向节(d)两个输出端通过同轴连接构成手腕的转子随动部分(b)，外部十字万向节(c)和内部十字万向节(d)具有同一转动中心，构成球型腕，实现手腕两个自由度的运动解耦，侧摆、俯仰角度可单独测量与控制，即编码器a(4)、制动器a(13)、阻尼器a(12)分别实现了俯仰运动的测量、制动、改变阻尼特性的功能，转子随动部分(b)轴线即为手腕转动轴线，实现侧摆、俯仰两自由度定点旋转运动，径向磁化永磁体(1)在空间万向旋转磁场的同轴随动磁矩驱动下，实现手腕侧摆、俯仰两自由度定点运动；
    所述的三轴亥姆霍兹线圈组(a)包括大线圈组、小线圈组和中间线圈组，每组包括两个完全相同的线圈，对称布置；三组线圈的轴线相互垂直，且三组线圈相互固定，其中大线圈组的底部固定在固定端(e)上，且中间线圈组的轴线与固定端(e)的轴线重合；内部十字 万向节(d)位于三组线圈中间的内部空间内，外部十字万向节(c)位于三组线圈外部；所述的外部十字万向节(c)、三轴亥姆霍兹线圈组(a)、内部十字万向节(d)在空间上形成三层嵌套结构。
  2. 权利要求1所述的一种电磁驱动两自由度球型机器人手腕的控制方法，其特征在于，具体控制过程如下：
    (1)作业前姿态零点标定过程
    通过三轴亥姆霍兹线圈组(a)产生旋转轴线垂直的空间万向旋转磁场，在同轴随动磁矩驱动下，转子随动部分(b)与固定端(e)的轴线重合，此时，俯仰转角的编码器a(4)和侧摆转角的编码器b(18)相对转角为零，此时分别给编码器a(4)和编码器b(18)上电，便存储并记忆两自由度解耦手腕的零点位置；当机器人手腕定位时，驱动侧摆与俯仰使机器人手腕处于主动腕模式，根据公式(2)的同轴随动磁矩控制系统与编码器a(4)和编码器b(18)构成转角位置闭环控制；
    (2)两自由度主动模态工作过程
    第一步，通电前，制动器a(13)与制动器b(19)一直锁定外部十字万向节(c)，无法进行侧摆、俯仰运动；
    第二步，根据目标空间方位，确定应该施加空间万向旋转磁场的旋转轴线方向，向三轴亥姆霍兹线圈组(a)通入三组等频交流电，产生相应方位的空间旋转磁场；
    第三步，径向磁化永磁体(1)在旋转磁场的作用开始进行自转，产生同轴随动磁矩，但由于制动器a(13)与制动器b(19)对外部十字万向节(c)两自由度的锁定，转子随动部分(b)无法进行侧摆、俯仰运动；
    第四步，制动器a(13)与制动器b(19)通电解除对外部十字万向节(c)的锁定，径向磁化永磁体(1)在旋转磁场同轴随动磁矩作用下，转子随动部分(b)轴线追随旋转磁场轴线进行侧摆、俯仰运动，俯仰转角通过编码器a(4)测量，偏转角度通过编码器b(18)测量，运动过程由阻尼器a(12)与阻尼器b(30)提供阻尼，防止发生振动；
    第五步，通过编码器a(4)与编码器b(18)实时反馈俯仰、侧摆角度信息；根据反馈的角度信息，对同轴随动磁矩进行反馈控制，直到满足精度为止，手腕到达目标位置，实现两自由度运动的控制；
    第六步，三轴亥姆霍兹线圈组(a)断电，制动器a(13)与制动器b(19)断电，再次对外部十字万向节(c)锁定，以固定机器人手腕方位；
    (3)单自由度主动模态工作过程
    第一步～第三步、第六步，同两自由度主动模态工作过程，其余过程如下；
    第四步，只对制动器a(13)通电解除外部十字万向节(c)的单轴锁定，径向磁化永磁体(1)在旋转磁场同轴随动磁矩作用下，转子随动部分(b)轴线追随旋转磁场轴线进行侧摆运动，偏转角度通过编码器b(18)测量；或者只对制动器b(19)通电解除对外部十字万向节(c)的单轴锁定，径向磁化永磁体(1)在旋转磁场同轴随动磁矩作用下，转子随动部分(b)轴线追随旋转磁场轴线进行侧摆运动，俯仰转角度通过编码器a(4)测量；
    第五步，通过编码器a(4)或者编码器b(18)实时反馈俯仰或者侧摆角度信息；根据反馈的角度信息，对同轴随动磁矩进行反馈控制，直到满足精度为止，手腕到达目标位置，分别实现单自由度运动的控制；
    (4)被动模态下同轴随动磁矩控制
    首先，假设在末端执行器(f)端部作用力矢量F与末端执行器(f)轴线所构成的平面内，F对手腕转动中心产生的力矩方向与同轴随动磁矩方向相反，此时，机器人手腕是一种直接电磁驱动的球形主动关节，电磁驱动原理是旋转磁场同轴随动磁矩效应，同轴随动磁矩计算公式为：
    Figure PCTCN2020093737-appb-100001
    式中，α角为磁矩为m永磁圆柱体轴线与旋转磁场B旋转轴线之间的夹角，m 0，B 0为磁矩矢量与旋转磁矢量幅值；
    (3)式表明，手腕同轴随动磁矩大小同时通过三组正交亥姆霍兹线圈中正弦电流的幅值I 0和永磁圆柱体轴线与旋转磁场轴线夹角α进行控制，使手腕变成柔顺腕；
    (5)手腕关节变刚度控制
    首先，假设在末端执行器f端部作用力矢量F与末端执行器f轴线所构成的平面内，F对手腕转动中心产生的力矩方向与同轴随动磁矩方向相反，此时，电磁驱动球型关节的刚度是：
    Figure PCTCN2020093737-appb-100002
    式中，s为末端执行器f端部沿着作用力方向的变形，L为执行器末端作用力F到电磁驱动球型关节中心的距离，则有，s＝Lα，α为磁矩为m径向磁化永磁体(1)轴线与旋转磁场B轴线的夹角；
    末端执行器f端部作用力F产生的力矩等于旋转磁场同轴随动磁矩，即
    Figure PCTCN2020093737-appb-100003
    将(5)代入(4)得
    Figure PCTCN2020093737-appb-100004
    由于
    Figure PCTCN2020093737-appb-100005
    则
    Figure PCTCN2020093737-appb-100006
    (6)式表明，手腕刚度通过旋转磁矢量幅值B0进行线性控制，即通过三组正交亥姆霍兹线圈中正弦电流的幅值I0进行控制，使手腕变成柔顺腕。
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