Hybrid magnetorheological clutch, compliant joint module and control strategy

Abstract

The application discloses a hybrid magneto-rheological clutch, a compliant joint module and a control strategy, and belongs to the technical field of robots. The clutch adopts a coaxial nested structure, integrates a compliant transmission multi-cylinder and a multi-disc structure, the two are staggered and filled with magneto-rheological fluid, and is equipped with double independent static excitation coils, so that independent magnetic circuits are formed. The compliant joint module is coaxially and compactly integrated with the magneto-rheological clutch, a harmonic reducer and a frameless torque motor. The control strategy adopts three-level nested closed-loop control, and a torque instruction is decoupled into multi-disc and multi-cylinder magnetic circuit components through dynamic weights. The multi-disc is responsible for high-precision dynamic adjustment, the multi-cylinder bears medium and high torque, and has an overload protection and a fault safety degradation mechanism. The application has high torque density and fast compliant adjustment characteristics, the static arrangement of the coil simplifies wiring, improves heat dissipation and reliability, can compensate for the nonlinearity of magneto-rheological material, realizes accurate torque control, and is suitable for complex interaction and safe operation of collaborative robots.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a hybrid magnetorheological clutch, a compliant joint module, and a control strategy. Background Technology

[0002] With the widespread application of industrial robots, service robots, and collaborative robots in industrial manufacturing, logistics handling, and special operations, robot joint modules not only need to possess high torque output capability, positioning accuracy, and dynamic response performance during operation, but also need to have a certain degree of compliance and safety to adapt to complex environments and human collaborative work conditions. Currently, most commonly used joint modules adopt an integrated rigid transmission structure of motor and reducer, which has limited compliance adjustment capabilities. Generally, compensation can only be achieved indirectly through mechanical elastic elements or control algorithms, making it difficult to adjust joint stiffness and damping in real time and controllably. This results in insufficient protection for personnel and equipment under external impact and collision conditions, and also limits the improvement of the robot's compliant interaction capabilities with the environment.

[0003] Magnetorheological fluids, as a typical smart material, can rapidly, reversibly, and continuously change their shear yield stress and viscosity in milliseconds under the action of an external magnetic field. They have been widely used in devices such as magnetorheological dampers, magnetorheological brakes, and magnetorheological clutches, enabling rapid and compliant control of torque or damping, and providing a new technical approach for achieving adjustable compliance in joint modules.

[0004] In the field of clutches, magnetorheological clutches, with their core advantages of millisecond-level response, continuous controllability, frictionless wear, and low energy consumption, have moved from laboratory prototypes to high-end equipment applications and are currently in a critical breakthrough period of industrialization and large-scale production. In the field of intelligent robots, they are used in the joint clutch components of collaborative robots, medical surgical robots, etc., which can achieve flexible force control and safe collision protection, thus driving a surge in market demand for high-precision magnetorheological clutches.

[0005] However, existing magnetorheological clutches still have the following shortcomings and need further improvement, such as:

[0006] (1) Most existing magnetorheological clutches are single-disc or single-cylinder structures, which can transmit limited torque per unit volume, making it difficult to meet the needs of intelligent robots for small volume and high power density.

[0007] (2) The coil current in a magnetorheological actuator directly determines the magnetic field strength of the working gap, which in turn determines its transmittable torque and equivalent stiffness. However, the coil current of existing magnetorheological clutches lacks precise algorithmic control, and only a fixed or coarse current is supplied. This can easily lead to torque and compliance characteristics drifting with working conditions and temperature, stiffness / damping deviating from expectations, inaccurate force control and torque limiting protection, inability to compensate for the nonlinearity and hysteresis of magnetorheological materials, and difficulty in achieving multi-stage compliance and smooth engagement. It can also easily generate engagement impact, high energy consumption and excessive temperature rise, weakening the safety and long-term stability of the joint.

[0008] (3) The magnetorheological clutch places the excitation coil on the rotating component, which requires power supply through conductive slip rings or flexible leads. This makes wiring difficult, has poor reliability, and is not conducive to heat dissipation and sealing. It is also difficult to directly integrate with the joint module which has limited volume and high power density requirements. Summary of the Invention

[0009] The purpose of this invention is to propose a hybrid magnetorheological clutch, a compliant joint module, and a control strategy to solve problems such as limited compliant adjustment capability of existing robot joint modules, low torque transmission per unit volume of magnetorheological clutches, insufficient coil control accuracy, and poor reliability of excitation coil wiring. This invention achieves precise control and compliant adjustment of robot joint torque, improves joint power density, positioning accuracy, dynamic response performance, and operational safety, and adapts to complex robot environments and human-assisted working conditions.

[0010] The technical solution adopted by the present invention is as follows: In the first aspect, the present invention proposes a hybrid magnetorheological clutch, including a coil support, an inner magnetic core, a magnetorheological compliant joint module output flange, an output transmission disc, a housing, a compliant transmission multi-cylinder structure, and a compliant transmission multi-disc structure;

[0011] The compliant transmission multi-cylinder structure includes an input cylinder, a magnetic yoke on the input cylinder, an output cylinder, a magnetic yoke on the output cylinder, and a coil of the cylinder; the input cylinder includes multiple concentric annular cylinders I with different radii, and the output cylinder includes multiple concentric annular cylinders II with different radii. The annular cylinders I are mounted on the magnetic yoke of the input cylinder, and the annular cylinders II are mounted on the magnetic yoke of the output cylinder. The annular cylinders I and II are staggered and have working gaps, which are filled with magnetorheological fluid.

[0012] The compliant drive multi-disc structure includes an input disk, a magnetic yoke on the input disk, an output disk, a magnetic yoke on the output disk, and coils on the disks. The input disk includes multiple disk plates I with identical structures, and the output disk includes multiple disk plates II with identical structures. The disk plates I are mounted on the magnetic yoke on the input disk, and the disk plates II are mounted on the magnetic yoke on the output disk. The disk plates I and II are arranged alternately with working gaps, and the working gaps are filled with magnetorheological fluid.

[0013] The axis of the compliant drive multi-cylinder structure and the compliant drive multi-disc structure coincides with the axis of the output flange of the magnetorheological compliant joint module.

[0014] The output transmission disk is fixedly connected to the output flange of the magnetorheological compliant joint module.

[0015] The coils of the cylinder and the disk are respectively wound on the coil support; the magnetic core is located inside the coil support and is rotatably connected to the coil support; the outer shell is located outside the coil support; the outer shell, the input cylinder, the magnetic yoke on the input cylinder, and the magnetic core are fixedly connected; the output cylinder and the magnetic yoke of the output cylinder are fixedly connected to the output transmission disk; the input disk is fixedly connected to the magnetic core, and the output disk is fixedly connected to the output transmission disk; the coil support is rotatably connected to the output flange of the magnetorheological compliant joint module.

[0016] As a further improvement of the present invention, the coil of the cylinder and the coil of the disk are independently wound dual-path excitation coils, which provide independent magnetic fields for the compliant drive multi-cylinder structure and the compliant drive multi-disc structure, respectively, forming a multi-cylinder magnetic circuit and a multi-disc magnetic circuit.

[0017] As a further improvement of the present invention, it also includes Hall sensor I, Hall sensor II, current sensor I, current sensor II, and dynamic torque sensor. Hall sensor II is installed near the working gap of the compliant drive multi-cylinder structure, and Hall sensor I is installed near the working gap of the compliant drive multi-disc structure, respectively, for detecting the magnetic field strength of the two working gaps; current sensor II is installed on the coil of the cylinder, and current sensor I is installed on the coil of the disk, respectively, for detecting the current of the coil of the cylinder and the coil of the disk; dynamic torque sensor is installed on the output flange of the magnetorheological compliant joint module for detecting the torque and rotational speed of the output flange of the magnetorheological compliant joint module.

[0018] As a further improvement of the present invention, the working gap I between the annular cylinder I and the annular cylinder II, and the working gap II between the disk I and the disk II, have a gap width ranging from 0.5 mm to 2.0 mm; and nano-sized silica particles or surface modifiers are added to the magnetorheological fluid filling the two working gaps to suppress particle sedimentation and agglomeration of the magnetorheological fluid under high-speed shear conditions.

[0019] Secondly, the present invention also proposes a compliant joint module, including the aforementioned hybrid magnetorheological clutch, and further including a harmonic reducer and a frameless torque motor; the harmonic reducer includes a flexible bearing, a cam, a harmonic reducer flex wheel, a harmonic reducer rigid wheel, and a crossed roller bearing, the flexible bearing and the cam forming a harmonic generator, the harmonic generator being embedded in the inner hole of the harmonic reducer flex wheel, the outer teeth of the harmonic reducer flex wheel meshing with the inner teeth of the harmonic reducer rigid wheel, and being fixedly connected to the outer ring of the crossed roller bearing; the harmonic reducer rigid wheel is fixedly connected to the inner ring of the crossed roller bearing, and is connected to the end face of the outer shell via a flange;

[0020] The frameless torque motor includes a stator winding, a rotor core, a drive plate, an adapter plate, an output shaft, and a base. The stator winding is mounted on the base, the rotor core is located inside the stator winding, the rotor core is fixedly connected to the output shaft, and the base is rotatably connected to the output shaft. The drive plate is detachably connected to the adapter plate, and the adapter plate is detachably connected to the base. The drive plate is electrically connected to the adapter plate and the stator winding. The output shaft is fixedly connected to the cam.

[0021] As a further improvement of the present invention, the frameless torque motor further includes an electromagnetic brake, which is fixedly connected to the base of the frameless torque motor and is used to brake the output shaft of the frameless torque motor.

[0022] Thirdly, the present invention also proposes a control strategy for a compliant joint module, applied to the aforementioned compliant joint module. The control strategy employs a three-level nested closed-loop control, comprising the following steps:

[0023] Step S1, Torque outer loop control: Receive external target torque command, collect the actual output torque of the joint module through dynamic torque sensor, calculate the difference between the target torque and the actual torque as torque loop error, and output the torque loop error as intermediate control quantity to the weight allocation module.

[0024] Step S2, Dual-path decoupling allocation: Based on the preset weight coefficient, the weight allocation module decouples the intermediate control quantity into a multi-disc magnetic circuit target component and a multi-cylinder magnetic circuit target component. Among them, the multi-disc magnetic circuit undertakes the dynamic adjustment of high precision and low stiffness, while the multi-cylinder magnetic circuit undertakes the main load of medium and high torque and locking conditions.

[0025] Step S3, Magnetic Field-Current Inner Loop Control: Cascade control of magnetic field loop and current loop is set for multi-disc magnetic circuit and multi-cylinder magnetic circuit respectively. The target components of multi-disc magnetic circuit and multi-cylinder magnetic circuit are converted into corresponding magnetic field strength commands. The magnetic field loop error is calculated and adjusted based on the actual magnetic field strength detected by Hall sensor I and Hall sensor II. Then, the adjusted magnetic field strength command is converted into the corresponding coil current command. The current loop error is calculated and compensated based on the actual operating current detected by current sensor I and current sensor II. Finally, the compensated current command is output to the corresponding excitation coil to achieve accurate tracking and compensation of the magnetorheological clutch torque.

[0026] As a further improvement of the present invention, the control strategy also includes step S4, an overload protection and fail-safe degradation mechanism: when the dynamic torque sensor detects that the actual output torque exceeds the safety threshold, or the current loop detects an abnormal coil current, the following operations are performed:

[0027] 1. Immediately cut off the current output of the multi-cylinder magnetic circuit to allow the compliant drive multi-cylinder structure to enter a free sliding state;

[0028] 2. Only a weak current is retained in the multi-disc magnetic circuit to maintain the basic flexibility of the joint in order to absorb impact energy;

[0029] 3. Trigger the electromagnetic brake of the joint module to lock the brake.

[0030] Compared with the prior art, the present invention has the following technical advantages:

[0031] This invention combines a hybrid magnetorheological structure, coaxial integrated design, and a three-level nested closed-loop control strategy to achieve a unified high power density, high-precision compliant transmission, and high safety and reliability. It effectively improves the torque output capacity per unit volume and dynamic response speed, solves the problems of nonlinearity and torque drift in magnetorheological materials, and achieves precise tracking and smooth adjustment of output torque. The use of dual independent static excitation coils eliminates the need for conductive slip rings, simplifies wiring and sealing structures, and improves heat dissipation efficiency and service life. Relying on the decoupled distribution of dual magnetic circuits and real-time monitoring of all parameters, it balances fine and compliant interaction with high torque load locking, and possesses a comprehensive overload protection and fault-tolerant degradation mechanism, significantly enhancing the operational stability, adaptability, and safety of robot joints in complex working conditions and human-robot collaborative scenarios. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the hybrid magnetorheological compliant joint module of the present invention.

[0033] Figure 2 This is an exploded view of the hybrid magnetorheological compliant joint module of the present invention.

[0034] Figure 3This is a schematic diagram of the magnetorheological fluid gap and magnetic circuit of the present invention.

[0035] Figure 4 This is a flowchart of the dual-coil single-output control strategy of the present invention.

[0036] Figure reference numerals: 1-Coil bracket; 2-Inner magnetic core; 3-Coil of the disc; 4-Output flange of the magnetorheological compliant joint module; 5-Dynamic torque sensor; 6-Key; 7-Output drive disc; 8-Current sensor I; 9-Pin on the output disc; 10-Magnetic yoke on the output disc; 11-Output disc; 12-Input disc; 13-Hall sensor I; 14-Pin on the input disc; 15-Magnetic yoke on the input disc; 16-Magnetic yoke on the input cylinder; 17-Input cylinder; 18-Magnetorheological fluid; 19-Flexible bearing; 20-Cam; 21- 22-Inner ring of crossed roller bearing; 23-Stator winding; 24-Rotor core; 25-Dust cover; 26-Drive plate; 27-Adapter plate; 28-Electromagnetic brake; 29-Motor output shaft; 30-Flexible wheel; 31-Rigid wheel; 32-Dust cover of crossed roller bearing; 33-Outer ring of crossed roller bearing; 34-Magnetic yoke on output cylinder; 35-Pin on output cylinder; 36-Output cylinder; 37-Hall sensor II; 38-Pin on input cylinder; 39-Cylinder coil; 40-Current sensor II; 41-Housing shell. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0038] Please refer to Figure 1 This invention proposes a hybrid magnetorheological clutch, including a coil support 1, an inner magnetic core 2, a magnetorheological compliant joint module output flange 4, an output transmission disc 7, a housing 41, a compliant transmission multi-cylinder structure, and a compliant transmission multi-disc structure.

[0039] Specifically, the compliant drive multi-cylinder structure includes an input cylinder 17, a magnetic yoke 16 on the input cylinder, an output cylinder 36, a magnetic yoke 34 on the output cylinder, and a coil 39 on the cylinder. The input cylinder 17 includes multiple concentric annular cylinders I with different radii, and the output cylinder 36 includes multiple concentric annular cylinders II with different radii. The annular cylinders I are mounted on the magnetic yoke 16 of the input cylinder, and the annular cylinders II are mounted on the magnetic yoke 34 of the output cylinder. The annular cylinders I and II are staggered and provided with a working gap I, which is filled with magnetorheological fluid 18.

[0040] The compliant drive multi-disc structure includes an input disk 12, a magnetic yoke 15 on the input disk, an output disk 11, a magnetic yoke 10 on the output disk, and a coil 3 on the disk. The input disk 12 includes multiple identical disks I, and the output disk 11 includes multiple identical disks II. The disks I are mounted on the magnetic yoke 15 on the input disk, and the disks II are mounted on the magnetic yoke 10 on the output disk. The disks I and II are arranged alternately and have a working gap II, which is filled with magnetorheological fluid 18.

[0041] The shafts of the compliant drive multi-cylinder structure and the compliant drive multi-disc structure coincide with the shaft of the output flange 4 of the magnetorheological compliant joint module.

[0042] The output drive disk 7 is fixedly connected to the output flange 4 of the magnetorheological compliant joint module via key 6. The coil 39 of the cylinder and the coil 3 of the disk are respectively wound on the coil support 1; the magnetic core 2 is located inside the coil support 1 and between the compliant drive multi-cylinder structure and the compliant drive multi-disc structure, and is rotatably connected to the coil support 1. The outer shell 41 is located outside the coil support 1.

[0043] The outer casing 41, the input cylinder 17, the magnetic yoke 16 on the input cylinder, and the magnetic core 2 are fixedly connected by the pin 38 on the input cylinder; the output cylinder 36 and the magnetic yoke 34 of the output cylinder are fixedly connected to the output transmission disk 7 by the pin 35 on the output cylinder.

[0044] The input disk 12 is fixedly connected to the input disk of the magnetic core 2 via pin 14, and the output disk 11 is fixedly connected to the output transmission disk 7 via pin 9. The coil bracket 1 and the output flange 4 of the magnetorheological compliant joint module are rotatably connected via bearings.

[0045] When the magnetorheological clutch is working, the coil support 1, the coil 39 of the cylinder, and the coil 3 of the disc form a stationary body, while the inner magnetic core 2, the magnetorheological compliant joint module output flange 4, the output transmission disc 7, the outer shell 41, and the compliant transmission multi-cylinder structure and the compliant transmission multi-disc structure form a relatively rotating body.

[0046] The coil 39 of the cylinder and the coil 3 of the disc are independently wound dual-path excitation coils, providing independent magnetic fields for the compliant drive multi-cylinder structure and the compliant drive multi-disc structure, respectively. At the same time, since the coil support 1 is stationary, the coil 39 of the cylinder and the coil 3 of the disc on it are also stationary, which makes wiring more convenient and avoids the problem of wire tangling.

[0047] The hybrid magnetorheological clutch also includes signal detection devices: Hall sensor I13, Hall sensor II37, current sensor I8, current sensor II40, and dynamic torque sensor 5. Hall sensor II37 is installed near the working gap of the compliant multi-cylinder structure, and Hall sensor I13 is installed near the working gap of the compliant multi-disc structure, respectively, to detect changes in magnetic field strength in the two working gaps. Current sensor II40 is installed on the coil 39 of the cylinder, and current sensor I8 is installed on the coil 3 of the disc, respectively, to detect changes in current in the coil 39 of the cylinder and the coil 3 of the disc. Dynamic torque sensor 5 is installed on the output flange 4 of the magnetorheological compliant joint module to detect its torque and speed.

[0048] Figure 3 This diagram illustrates the magnetic circuit layout of the magnetic field in compliant drive multi-cylinder and compliant drive multi-disc structures, including the multi-cylinder and multi-disc magnetic circuits. The blue closed loop represents the multi-cylinder magnetic circuit, and the green closed loop represents the multi-disc magnetic circuit. The coil support 1, magnetic core 2, output drive disc 7, and outer casing 41 are all made of magnetically conductive material. Specifically, the yoke 16 on the input cylinder, the yoke 34 on the output cylinder, the yoke 15 on the input disc, and the yoke 10 on the output disc are all made of electrical pure iron, while the outer casing 41 is made of magnetically conductive stainless steel.

[0049] Please refer to Figure 1 and Figure 2 The present invention also proposes a compliant joint module, including the above-mentioned hybrid magnetorheological clutch, and further including a harmonic reducer and a frameless torque motor.

[0050] Specifically, the harmonic reducer includes a flexible bearing 19, a cam 20, a flexure wheel 30, a rigid wheel 31, and a crossed roller bearing. The flexible bearing 19 and the cam 20 form a harmonic generator, which is embedded in the inner hole of the flexure wheel 30. The external teeth of the flexure wheel 30 mesh with the internal teeth of the rigid wheel 31, and the flexure wheel 30 is fixedly connected to the outer ring 33 of the crossed roller bearing. The rigid wheel 31 is fixedly connected to the inner ring 21 of the crossed roller bearing, and the rigid wheel 31 is connected to the end face of the housing 41 via a flange. The crossed roller dust cover 32 is used to protect the rollers inside the crossed roller bearing.

[0051] The frameless torque motor includes a stator winding 22, a rotor core 23, a drive plate 25, an adapter plate 26, a motor output shaft 28, and a motor base 29. The stator winding 22 is mounted on the motor base 29, and the rotor core 23 is located inside the stator winding 22. The rotor core 23 is fixedly connected to the motor output shaft 28, and the motor base 29 is rotatably connected to the motor output shaft 28. The drive plate 25 is detachably connected to the adapter plate 26, and the adapter plate 26 is detachably connected to the motor base 29. The drive plate 25, adapter plate 26, and stator winding 22 are electrically connected, and the motor output shaft 28 is fixedly connected to a cam 20. The flexible wheel 30 is also fixedly connected to the motor base 29. The adapter plate 26 is an intermediary circuit connecting the drive plate 25 to other components.

[0052] Specifically, the frameless torque motor also includes an electromagnetic brake 27, which is fixedly connected to the motor base 29 and is used to brake the motor output shaft 28.

[0053] Specifically, the frameless torque motor also includes a dust cover 24, which is detachably connected to the adapter plate 26 and rotatably connected to the output flange 4 of the magnetorheological compliant joint module. The dust cover 24 serves two purposes: firstly, it protects the internal drive board 25, adapter plate 26, and other circuit boards and components from dust; secondly, it has multiple electrical interfaces on its rear end face.

[0054] The transmission principle of the compliant joint module is as follows: After the frameless torque motor is started, the motor output shaft 28 rotates and drives the cam 20 of the harmonic generator to rotate. The flexible bearing 19 is sleeved on the cam 20 and meshes with the flexible wheel 30. Because the flexible wheel 30 meshes with the rigid wheel 31 and the flexible wheel 30 and the outer ring 33 of the crossed roller bearing are fixedly connected and remain stationary, the rigid wheel 31 is driven to rotate. The rigid wheel 31 and the inner ring 21 of the crossed roller bearing rotate synchronously. Because the rigid wheel 31 is fixedly connected to the end face of the outer shell 41, the outer shell 41 is finally driven to rotate. The outer casing 41, input cylinder 17, magnetic yoke 16 on the input cylinder, and inner magnetic core 2 are fixed together by pin 38 on the input cylinder. As the outer casing 41 rotates, it drives the input cylinder 17 to rotate. The input cylinder 17 drives the output cylinder 36 to rotate by means of the flexible properties of the magnetorheological fluid 18 in the working gap. The output cylinder 36 and the magnetic yoke 34 on the output cylinder are fixedly connected to the output transmission disk 7 by pin 35 on the output cylinder, thus driving the output transmission disk 7 to rotate. The output transmission disk 7 is then fixed to the output flange 4 of the magnetorheological compliant joint module by key 6, ultimately driving the output flange to rotate. Meanwhile, as the inner magnetic core 2 rotates with the outer casing 41, it will synchronously drive the input disk 12 to rotate because the inner magnetic core 2 is fixed to the input disk 12 by the pin 14 on the input disk. The input disk 12 drives the output disk 11 to rotate by the magnetorheological fluid 18 in the working gap between it and the output disk 11. The output disk 11 is also fixed to the output transmission disk 7 by the pin 9 on the output disk, which will also drive the output transmission disk 7 to rotate, thereby driving the output flange of the magnetorheological compliant joint module to rotate.

[0055] Because the multi-cylinder magnetic circuit and the multi-disc magnetic circuit are set independently, relying on the characteristics of magnetorheological fluid under an external magnetic field, the on / off control of the transmission connection between the input cylinder and the output cylinder, and between the input disk and the output disk can be realized by adjusting the coil current, thus forming a variety of transmission combination working conditions: First, the input cylinder 17, the output cylinder 36, and the input disk 12 and the output disk 11 simultaneously generate a driving relationship. The two structures work together to drive the output transmission disk 7 to work, and the combined output force drives the output flange 4 of the magnetorheological compliant joint module to rotate. In this working condition, the output torque ratio of the two structures can be adjusted according to the needs to achieve a torque distribution effect of large torque in the input cylinder-output cylinder path and small torque in the input disk-output disk path, or vice versa; Second, only the input cylinder 17 and the output cylinder 36 form a driving relationship, and the transmission between the input disk 12 and the output disk 11 is disconnected. The output transmission disk 7 is driven solely by the input cylinder-output cylinder path, which drives the output flange of the magnetorheological compliant joint module to rotate. By flexibly combining the multi-disc transmission structure and the multi-cylinder transmission structure, the optimal torque output and adjustment can be achieved according to the torque and stiffness requirements of the actual working conditions.

[0056] This invention also proposes a control strategy for a compliant joint module, employing a three-level nested closed-loop control, including the following steps:

[0057] Step S1, Torque outer loop control: Receive external target torque command, collect the actual output torque of the joint module through dynamic torque sensor 5, calculate the difference between the target torque and the actual torque as the torque loop error, and transmit the torque loop error as an intermediate control quantity to the weight allocation module.

[0058] Step S2, Dual-path decoupling allocation: Based on preset weight coefficients, the weight allocation module decouples the intermediate control quantity into a multi-disc magnetic circuit target component and a multi-cylinder magnetic circuit target component. The multi-disc magnetic circuit undertakes high-precision, low-stiffness dynamic adjustment, while the multi-cylinder magnetic circuit undertakes the main load-bearing capacity under medium-to-high torque and locking conditions.

[0059] Step S3, Magnetic Field-Current Inner Loop Control: Cascade control of the magnetic field loop and current loop is set for the multi-disc magnetic circuit and the multi-cylinder magnetic circuit respectively. The actual magnetic field strength of the multi-disc magnetic circuit is detected by Hall sensor I13, the actual magnetic field strength of the multi-cylinder magnetic circuit is detected by Hall sensor II37, the actual operating current of coil 3 of the disc is detected by current sensor I8, and the actual operating current of coil 39 of the cylinder is detected by current sensor II40. The target components of the multi-disc magnetic circuit and the multi-cylinder magnetic circuit are converted into corresponding magnetic field strength commands. The magnetic field loop error is calculated and adjusted based on the actual magnetic field strength detected by the Hall sensors. Then, the adjusted magnetic field strength command is converted into the corresponding coil current command. The current loop error is calculated and compensated based on the actual operating current detected by the current sensor. Finally, the compensated current command is output to the corresponding static excitation coil to achieve accurate tracking and compensation of the magnetorheological clutch torque.

[0060] Specifically, Figure 4 The specific control strategy for the joint module is illustrated. At the control structure level, this invention abstracts the hybrid magnetorheological clutch as a torque control object with dual actuators and a single output, using a single torque closed loop as the outer loop, and controlling the torque according to the desired torque. The error between them is first determined by the weighting coefficients. Torque commands are distributed between the multi-cylinder and multi-disc magnetorheological units. Each unit employs a three-stage nested closed-loop structure of torque-magnetic field-current. Under torque control, the desired magnetic flux density required to achieve the desired torque is determined. The actual magnetic flux density detected by the magnetic field sensor and The error is used to generate the coil reference current under the magnetic field control algorithm. The actual current detected by the current sensor and The error generates current under current control. This refers to the current that the excitation coil should generate. The magnetic field generated by the energized excitation coil acts on the magnetorheological fluid. The working process is the same for multi-disc and multi-cylinder systems; the final output torque is the sum of the torque provided by the multi-disc system and the torque provided by the multi-cylinder system, i.e. Furthermore, through closed-loop feedback from a torque sensor, precise torque control and smooth adjustment of the dual-coil magnetorheological clutch are achieved.

[0061] Step S4, Overload Protection and Fault-Safe Degradation Mechanism: When the dynamic torque sensor 5 detects that the actual output torque exceeds the safety threshold, or the current loop detects an abnormal coil current, the following operations are performed:

[0062] 1. Immediately cut off the current output of the multi-cylinder magnetic circuit to allow the multi-cylinder magnetorheological structure to enter a free-slip state;

[0063] 2. Only a weak current is retained in the multi-disc magnetic circuit to maintain the basic flexibility of the joint in order to absorb impact energy;

[0064] 3. Trigger the electromagnetic brake 27 of the joint module to lock the brake.

[0065] The three-level nested closed-loop control strategy adopted in this invention enables the compliant joint module to achieve high-precision tracking and stable control of output torque, effectively compensating for the nonlinearity and hysteresis characteristics of magnetorheological materials, suppressing disturbances caused by factors such as temperature rise and rotational speed, and avoiding transmission shock and torque drift. Through dual-path magnetic circuit decoupling and dynamic weight allocation, the advantages of multi-disc and multi-cylinder structures can be complemented, taking into account both high-precision compliant adjustment and medium-to-large torque bearing capacity, improving the dynamic response and working condition adaptability of the joint. At the same time, with the real-time monitoring of all parameters of magnetic field, current, and torque and the fault safety degradation mechanism, it can quickly realize graded protection and safety braking under overload or abnormal conditions, greatly improving the reliability of joint operation and the safety of human-machine interaction. Overall, the joint module achieves an overall improvement in control accuracy, compliant performance, response speed, and operational safety.

[0066] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A hybrid magneto-rheological clutch, characterized by, Includes coil support (1), inner magnetic core (2), magnetorheological compliant joint module output flange (4), output drive disk (7), housing (41), compliant drive multi-cylinder structure and compliant drive multi-disc structure; The compliant transmission multi-cylinder structure includes an input cylinder (17), a magnetic yoke (16) on the input cylinder, an output cylinder (36), a magnetic yoke (34) on the output cylinder, and a coil (39) of the cylinder; the input cylinder (17) includes multiple concentric annular cylinders I with different radii, and the output cylinder (36) includes multiple concentric annular cylinders II with different radii. The annular cylinders I are mounted on the magnetic yoke (16) of the input cylinder, and the annular cylinders II are mounted on the magnetic yoke (34) of the output cylinder. The annular cylinders I and II are staggered and have a working gap, which is filled with magnetorheological fluid (18). The compliant drive multi-disc structure includes an input disk (12), a magnetic yoke (15) on the input disk, an output disk (11), a magnetic yoke (10) on the output disk, and a coil (3) of the disk; the input disk (12) includes multiple disks I with the same structure, and the output disk (11) includes multiple disks II with the same structure. The disks I are mounted on the magnetic yoke (15) on the input disk, and the disks II are mounted on the magnetic yoke (10) on the output disk; the disks I and II are arranged alternately and have working gaps, and the working gaps are filled with magnetorheological fluid (18); The axis of the compliant drive multi-cylinder structure and the compliant drive multi-disc structure coincides with the axis of the magnetorheological compliant joint module output flange (4). The output transmission disk (7) is fixedly connected to the output flange (4) of the magnetorheological compliant joint module; The coil (39) of the cylinder and the coil (3) of the disk are respectively wound on the coil support (1); the magnetic core (2) is located inside the coil support (1) and is rotatably connected to the coil support (1); the outer shell (41) is located outside the coil support (1); the outer shell (41), the input cylinder (17), the magnetic yoke (16) on the input cylinder and the magnetic core (2) are fixedly connected; the output cylinder (36) and the magnetic yoke (34) of the output cylinder are fixedly connected to the output transmission disk (7); the input disk (12) is fixedly connected to the magnetic core (2) and the output disk (11) is fixedly connected to the output transmission disk (7); the coil support (1) is rotatably connected to the magnetorheological compliant joint module output flange (4).

2. The hybrid magnetorheological clutch according to claim 1, characterized in that, The coil (39) of the cylinder and the coil (3) of the disk are independently wound dual-path excitation coils, which provide independent magnetic fields for the compliant drive multi-cylinder structure and the compliant drive multi-disc structure, respectively, forming a multi-cylinder magnetic circuit and a multi-disc magnetic circuit.

3. The hybrid magnetorheological clutch according to claim 2, characterized in that, It also includes Hall sensor I (13), Hall sensor II (37), current sensor I (8), current sensor II (40) and dynamic torque sensor (5). Hall sensor II (37) is installed near the working gap of the compliant drive multi-cylinder structure, and Hall sensor I (13) is installed near the working gap of the compliant drive multi-disc structure, respectively, to detect the magnetic field strength of the two working gaps; current sensor II (40) is installed on the coil (39) of the cylinder, and current sensor I (8) is installed on the coil (3) of the disc, respectively, to detect the current of the coil (39) of the cylinder and the coil (3) of the disc; dynamic torque sensor (5) is installed on the output flange (4) of the magnetorheological compliant joint module, to detect the torque and rotational speed of the output flange (4) of the magnetorheological compliant joint module.

4. The hybrid magnetorheological clutch according to claim 1, characterized in that, The working gap I between the annular cylinder I and the annular cylinder II, and the working gap II between the disk I and the disk II, have a gap width ranging from 0.5 mm to 2.0 mm; and nano-sized silica particles or surface modifiers are added to the magnetorheological fluid filling the two working gaps to suppress particle sedimentation and agglomeration of the magnetorheological fluid under high-speed shear conditions.

5. A compliant joint module, characterized in that, The system includes the hybrid magnetorheological clutch as described in claim 3, and further includes a harmonic reducer and a frameless torque motor; the harmonic reducer includes a flexible bearing (19), a cam (20), a harmonic reducer flexure (30), a harmonic reducer rigid wheel (31), and a crossed roller bearing; the flexible bearing (19) and the cam (20) form a harmonic generator; the harmonic generator is embedded in the inner hole of the harmonic reducer flexure (30); the outer teeth of the harmonic reducer flexure (30) mesh with the inner teeth of the harmonic reducer rigid wheel (31) and are fixedly connected to the outer ring (33) of the crossed roller bearing; the harmonic reducer rigid wheel (31) is fixedly connected to the inner ring (21) of the crossed roller bearing and is connected to the end face of the housing (41) via a flange; The frameless torque motor includes a frameless torque motor stator winding (22), a rotor core (23), a drive plate (25), an adapter plate (26), a frameless torque motor output shaft (28), and a frameless torque motor base (29). The frameless torque motor stator winding (22) is mounted on the frameless torque motor base (29), and the rotor core (23) is located inside the frameless torque motor stator winding (22). The rotor core (23) and the frameless torque motor output shaft (28) are connected. 8) Fixed connection: The frameless torque motor base (29) is rotatably connected to the frameless torque motor output shaft (28); The drive plate (25) is detachably connected to the adapter plate (26), and the adapter plate (26) is detachably connected to the frameless torque motor base (29); The drive plate (25) is electrically connected to the adapter plate (26) and the frameless torque motor stator winding (22); The frameless torque motor output shaft (28) is fixedly connected to the cam (20).

6. The compliant joint module according to claim 5, characterized in that, The frameless torque motor also includes an electromagnetic brake (27), which is fixedly connected to the frameless torque motor base (29) and is used to brake the output shaft (28) of the frameless torque motor.

7. A control strategy for a compliant joint module, applied to the compliant joint module as described in claim 5 or 6, characterized in that, The control strategy employs a three-level nested closed-loop control, including the following steps: Step S1, Torque outer loop control: Receive external target torque command, collect the actual output torque of the joint module through dynamic torque sensor (5), calculate the difference between the target torque and the actual torque as torque loop error, and output the torque loop error as intermediate control quantity to the weight allocation module; Step S2, Dual-path decoupling allocation: Based on the preset weight coefficient, the weight allocation module decouples the intermediate control quantity into a multi-disc magnetic circuit target component and a multi-cylinder magnetic circuit target component. Among them, the multi-disc magnetic circuit undertakes the dynamic adjustment of high precision and low stiffness, while the multi-cylinder magnetic circuit undertakes the main load of medium and high torque and locking conditions. Step S3, Magnetic Field-Current Inner Loop Control: For multi-disc magnetic circuits and multi-cylinder magnetic circuits, cascade control of magnetic field loop and current loop is set respectively. The target components of multi-disc magnetic circuits and multi-cylinder magnetic circuits are converted into corresponding magnetic field strength commands. The magnetic field loop error is calculated and adjusted in combination with the actual magnetic field strength detected by Hall sensor I (13) and Hall sensor II (37). The adjusted magnetic field strength command is then converted into the corresponding coil current command. The current loop error is calculated and compensated in combination with the actual working current detected by current sensor I (8) and current sensor II (40). Finally, the compensated current command is output to the corresponding excitation coil to achieve accurate tracking and compensation of the torque of the magnetorheological clutch.

8. The control strategy for the compliant joint module according to claim 7, characterized in that, The control strategy also includes step S4, overload protection and fault-safe degradation mechanism: when the dynamic torque sensor (5) detects that the actual output torque exceeds the safety threshold, or when the current loop detects an abnormal coil current, the following operations are performed:

1. Immediately cut off the current output of the multi-cylinder magnetic circuit to allow the compliant drive multi-cylinder structure to enter a free sliding state; 2. Only a weak current is retained in the multi-disc magnetic circuit to maintain the basic flexibility of the joint in order to absorb impact energy; 3. Trigger the electromagnetic brake (27) of the joint module to lock the brake.

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