CN101293351A - Safe Stiffness Adjustable Mechanical Joint of Magneto-rheological Fluid Clutch - Google Patents

Abstract

The invention relates to a safety-type adjustable stiffness mechanical joint of a magneto-rheological fluid clutch in the field of mechanical technology, including a power mechanism, a transmission mechanism, an output mechanism, a drive sensing component, and a variable stiffness mechanism, and the transmission mechanism is connected to the output mechanism , the variable stiffness mechanism is the magnetorheological fluid clutch, the magnetorheological fluid clutch is connected with the power mechanism and the transmission mechanism, and the driving and sensing components refer to the servo motor driver and the motor sensor. The motor driver uses the encoder feedback to adjust the joint speed by using the speed loop, and uses its own current loop to control the output current of the motor, thereby controlling the magnetic field strength in the clutch, and then controlling the joint stiffness and clutch transmission torque. Both stiffness and speed of the present invention are controllable, and can realize joint safety while maintaining joint performance. In the event of a collision, it can protect the safety of motors, robotic arms and people. It can realize the conversion of joint rigidity and softness, and ensure the accuracy of end motion.

Description

Safe Stiffness Adjustable Mechanical Joint of Magneto-rheological Fluid Clutch

technical field

The invention relates to a robot in the technical field of machinery, in particular to a safety-type mechanical joint with adjustable stiffness of a magneto-rheological fluid clutch.

Background technique

Robots are coming into human life, providing people with various services. Safety should be a priority when it comes to human-robot interactions. If a robotic arm with adjustable joint stiffness can be achieved to achieve compliant control, the robot will become safer. In the event of a collision, it can absorb the energy of the collision and reduce the risk of collision. The magnetorheological fluid clutch uses magnetorheological fluid as the working medium to transmit power. Magnetorheological fluid is a new type of intelligent liquid, which can produce magnetorheological effect under the action of an external magnetic field, and can be controlled by a current controller. Rheological fluid is used to adjust structural stiffness and output torque. The traditional variable stiffness method is generally a variable stiffness device using elastic bodies such as springs, which is a passive variable stiffness method. This traditional mechanical device can realize the change of stiffness, but cannot realize the controllable adjustment of stiffness.

After searching the documents of the prior art, it is found that Chinese Patent No. 200710037290.7 and Publication No. CN 101011825A disclose a safety type variable mechanical joint. It is achieved by a plurality of cylinders constrained by variable stiffness to achieve joint variable stiffness. The cylinder is composed of five parts: inner ejector rod, electromagnet, elastic support, rigid ball and cylinder wall. When the electromagnet is in the energized state, the entire system exhibits the characteristics of a rigid joint; when the electromagnet is in a de-energized state, the entire system exhibits the characteristics of a flexible joint. When it has dual rigidity characteristics of high rigidity during operation and low rigidity during impact buffering, it improves the safety of external operation, small in size, compact in structure, and easy to install, especially suitable for fine work machinery with high requirements on volume and weight arm. However, this variable-stiffness mechanical arm only has different stiffnesses in the two states of power on and off, and cannot achieve precise controllability of the stiffness, and cannot continuously adjust the stiffness of the joint.

Contents of the invention

The purpose of the present invention is to overcome the existing problems and deficiencies in the prior art, and propose a safety-type mechanical joint with adjustable stiffness of the magneto-rheological fluid clutch, which uses the special performance of the magneto-rheological fluid clutch to realize the torque transmission of the joint and according to the load Different stiffnesses are continuously adjustable. Using intelligent liquid-magnetorheological fluid as the transmission medium can realize stepless change of torque and speed, short response time, easy to obtain control signal (through the external magnetic field strength), and the joint has high stiffness under the condition of large load , the joint speed can be reduced to obtain higher operational safety; the joint stiffness is lower when the load is low, and the joint has greater flexibility, which can reduce the risk in the case of a fast joint speed. When colliding with a person, the clutch disengages, and the joint stiffness decreases rapidly. At this time, the joint has greater flexibility, which can protect the safety of the robot arm and people.

The present invention is achieved through the following technical proposals. The present invention is a joint with adjustable stiffness, which includes a power mechanism, a variable stiffness mechanism, a transmission mechanism, an output mechanism, and a drive sensing component. The variable stiffness mechanism is a magneto-rheological fluid clutch, which is connected with a power mechanism and a transmission mechanism through a shaft coupling.

The drive sensing component includes a servo motor driver and a motor encoder, which are the core for controlling joint stiffness and joint speed. The servo motor driver is connected to the motor encoder in the joint through the motor encoder line, and connected to the industrial computer through the CAN line. The motor driver can use the speed loop to adjust the joint speed through the motor encoder feedback, and use the current loop to control the output current of the motor, thereby controlling the magnetic field strength in the magneto-rheological fluid clutch, and then controlling the joint stiffness and the magneto-rheological fluid clutch transmission torque.

The power mechanism includes a DC servo motor with a reducer, a motor flange and a first shaft coupling. The DC servo motor is installed on the motor flange, and the motor flange is fixed on the joint shell. The motor shaft of the DC servo motor is connected with the variable stiffness mechanism through a first coupling.

The transmission mechanism includes a shaft coupling, a transmission shaft, a shaft sleeve, a bearing seat, and a bearing. The transmission shaft is covered with a shaft sleeve, and a bearing is installed on the shaft sleeve. The bearing is installed in the bearing seat, and the coupling is connected with the variable stiffness mechanism. .

The output mechanism includes an output flange and a spacer, and the output flange and the transmission shaft in the transmission mechanism are fixedly connected with the spacer through screws.

The magneto-rheological fluid clutch includes a driving shaft, magneto-rheological fluid, a driving element, an excitation coil, a rotor, a rolling bearing, and a driven shaft. The driving part connected with the driving shaft is a cylindrical shell, the rotor is connected with the driven shaft, and the driven shaft is supported on the driving part through rolling bearings. An excitation coil is embedded on the rotor, and magnetorheological fluid is filled in the concentric annular gap between the cylindrical shell and the driven rotor. When the electromagnetic coil is fed with current, the suspended particles in the magnetorheological fluid are magnetized under the action of the magnetic field, and attract each other along the direction of the magnetic field to form a chain. This chain structure increases the shear stress of the magnetorheological fluid. This shear stress is used to transmit torque, thereby engaging the driving member with the driven shaft, and the clutch is engaged. After the coil is de-energized, the magneto-rheological fluid is quickly transformed into Newton fluid, so the torque generated by the viscosity of the fluid is very small, which cannot drive the driven shaft to rotate, and the clutch is disengaged.

The magnetorheological fluid is mainly composed of a carrier liquid, magnetic particles, and a surfactant, and the proportions of the three are: 60%, 30%, and 10%, respectively.

The invention achieves the purpose of adjustable stiffness through current control on the magneto-rheological fluid clutch. The joint stiffness is determined by the stiffness of the magneto-rheological fluid clutch, and the stiffness of the magneto-rheological fluid clutch is actually the stiffness of the magnetorheological fluid. Magnetorheological fluid can produce obvious magnetorheological effect under the action of a magnetic field, that is, a rapid and reversible transformation between a liquid state and a solid state. The current of the magneto-rheological fluid clutch is controlled through the current loop of the motor driver, and the magnitude of the magnetic field is controlled by controlling the output current of the motor. As the clutch current increases, the magnetic field on the magnetorheological fluid increases, and the degree of solidification of the magnetorheological fluid becomes higher and higher, which indicates that the yield strength of the magnetorheological fluid becomes larger, and the joint stiffness becomes larger externally. When the load of the mechanical arm becomes larger, in order to balance the load, the torque fluid generated by the clutch must become larger, and the torque of the clutch is generated by the shear force of the magneto-rheological fluid, so the shear force becomes larger, and the shear force is It increases with the increase of the current, that is, the control current of the clutch must increase, so at this time, it is manifested as an increase in the joint stiffness; when the load of the mechanical arm becomes smaller, in order to balance the load, the torque generated by the clutch must decrease at this time, and the clutch The driving current decreases, and the joint stiffness decreases externally. Only when the external force is lower than the shear resistance of the magnetorheological fluid, the magnetorheological fluid is in a solid-like state; when the external force exceeds the shear resistance of the magnetorheological fluid, the magnetic chain of the magnetorheological fluid is cut, which means The magnetorheological fluid is in a liquid state. Therefore, if the external torque is too large, the stiffness of the clutch will drop sharply in an instant to protect the motor and the mechanical arm. If it collides with a person, it can also protect the safety of the person.

The DC servo motor is controlled by the motor driver, and the joint speed can be controlled by controlling the speed of the servo motor, while the speed of the DC servo motor is controlled by the speed loop in the motor driver, where the encoder provides a feedback signal. In order to achieve a safe mechanical arm, when the load is relatively large, the above analysis shows that the joint stiffness is relatively large, so the joint can be controlled to run at a low speed; when the load is relatively small, the joint can be controlled due to the small stiffness. Run at high speed to improve work efficiency.

The present invention can realize stepless speed regulation of joint speed and variable joint stiffness with different loads through the control of the motor driver. Stiffness and velocity are both controllable to achieve joint safety while maintaining joint performance. In the event of a collision, it can protect the safety of motors, robotic arms and people. It can realize the conversion of joint rigidity and softness, and can ensure the accuracy of end motion.

Description of drawings

Fig. 1 is a schematic diagram of the plane structure of the present invention

Fig. 2 is a schematic plan view of the magnetorheological fluid clutch of the present invention.

In the figure: joint housing 1, DC servo motor with reducer 2, motor flange 3, first coupling 5, magneto-rheological fluid clutch 6, second coupling 7, transmission shaft 8, lower bearing seat 9 , The first bearing 11, the shaft sleeve 12, the second bearing 13, the upper bearing seat 14, the output flange 16, the spacer ring 19, and the motor driver 20. Motor encoder 21; 4, 10, 15, 17, 18 are common connector screws among the figure.

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings: this embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following the described embodiment.

As shown in Figure 1, this embodiment includes: a power mechanism, a variable stiffness mechanism, a transmission mechanism, an output mechanism, and a drive sensing component.

The power mechanism includes a DC servo motor 2 with a reducer, a motor flange 3 and a first shaft coupling 5 . The servo motor 2 is fixed on the motor flange 3 by screws 18 , and the motor flange 3 is fixed on the joint housing 1 by screws 4 . The first coupling 5 is used to connect the DC servo motor 2 and the variable stiffness mechanism in the power mechanism.

The variable stiffness mechanism, that is, the magneto-rheological fluid clutch 6, is connected to the DC servo motor 2 through the first coupling 5, and connected to the transmission shaft 8 of the transmission mechanism through the second coupling 7.

The transmission mechanism includes a second shaft coupling 7, a transmission shaft 8, a shaft sleeve 12, a lower bearing seat 9, an upper bearing seat 14, a first bearing 11, and a second bearing 13. The transmission shaft 8 is covered with a shaft sleeve 12, and the shaft sleeve The first bearing 11,13 is installed on 12, and the first bearing 11 is to be contained in the lower bearing seat 9, and the second bearing 13 is to be contained in the upper bearing seat 14. The lower bearing seat 9 is fixed on the joint casing 1 by screws 10 , and the upper bearing seat 14 is fixed on the joint casing 1 by screws 15 .

The output mechanism includes an output flange 16 and a spacer 19, and the output flange 16 is fixedly connected with the transmission shaft 8 in the transmission mechanism through the screws 17 and the spacer 19. The output of the output mechanism is connected to the next joint of the mechanical arm.

The driving and sensing components include a servo motor driver 20 and a motor encoder 21, and the servo motor driver 20 is the core for controlling joint stiffness and joint speed. Due to the problem of space in the joint, the servo motor driver 20 cannot be placed in the joint housing. In this embodiment, it is placed in a separate control box. The motor encoder 21 is installed at the tail end of the DC servo motor 2. The servo motor driver 20 is It is connected to the motor encoder 21 in the joint through the motor encoder line, connected to the power supply through the auxiliary power line, and connected to the industrial computer through the CAN line. The rotor of the DC servo motor 2 rotates under the action of the magnetic field. At the same time, the encoder 21 feeds back a signal to the servo motor driver 20. The servo motor driver 20 compares the feedback value with the target value and adjusts the rotation angle of the DC servo motor 2, thereby realizing the control of the DC servo motor. Servo motor 2 speed control. The motor driver 20 can use the speed loop to adjust the joint speed through the feedback of the encoder 21, and use the current loop to control the output current of the DC servo motor 2, so as to control the magnetic field in the magneto-rheological fluid clutch 6, and then control the joint stiffness and magnetorheology. The hydraulic clutch 6 transmits torque.

As shown in FIG. 2 , in this embodiment, the magneto-rheological fluid clutch includes a driving shaft 22 , a magneto-rheological fluid 23 , a driving element 24 , an excitation coil 25 , a rotor 27 , a rolling bearing 28 and a driven shaft 29 . The driving part 24 connected with the driving shaft 22 is a cylindrical shell, the rotor 27 is connected with the driven shaft 29 , and the driven shaft 29 is supported on the driving part 24 through the rolling bearing 28 . An excitation coil 25 is embedded on the rotor 27 , and the magneto-rheological fluid 23 is filled in the concentric annular gap between the cylindrical casing and the driven rotor 27 . Part 26 is the total number of magnetic force lines on the cross-section generated by the current and the coil, that is, the magnetic flux. When the motor driver 20 provides current to the clutch magneto-rheological fluid 23, the suspended particles in the magnetorheological fluid 23 are magnetized under the action of a magnetic field and attract each other along the direction of the magnetic field to form a chain. This chain structure increases the strength of the magnetorheological fluid. The shearing stress of 23 relies on the shearing stress to transmit the torque, thereby engaging the driving member 24 with the driven shaft 29, and the clutch is in an engaged state. After the excitation coil 25 is powered off, the magneto-rheological fluid 23 is rapidly converted into Newton fluid again, so the torque generated by the viscosity of the fluid is very small, and the driven shaft 29 cannot be driven to rotate, and the clutch is disengaged.

Magnetorheological fluid is mainly composed of carrier fluid, magnetic particles, and surfactants. The three are respectively: 60%, 30%, and 10% according to the weight ratio.

In order to reduce the structural size of the clutch as much as possible, for the material of the magnetorheological fluid, try to use a larger volume fraction or higher viscosity carrier fluid, appropriate additives, particles with appropriate diameter and high magnetization strength, etc., can make the clutch The torque transmitted per unit volume of magnetorheological fluid increases. When selecting the core material, not only high magnetic permeability and high magnetic saturation are required, but also to ensure that the remanence of the core material is relatively small. For coil distribution, multi-coils should be distributed with small intervals, which can enhance the uniformity of the working magnetic field and increase the transmitted torque.

In this embodiment, silicone oil is selected as the carrier liquid. Magnetic particles adopt carbonyl iron powder. In order to ensure the suspension stability of the particles and increase the rheological properties of the entire magnetorheological fluid, the surfactant oleic acid is added to prevent the magnetic particles from settling and irreversible spongy flocculation.

The joint stiffness is determined by the stiffness of the magnetorheological fluid clutch, and the stiffness of the magnetorheological fluid clutch is actually the stiffness of the magnetorheological fluid 23 . The magnetorheological fluid 23 can produce an obvious magnetorheological effect under the action of a magnetic field, that is, a rapid and reversible transformation between a liquid state and a quasi-solid state. The servo motor driver 20 controls the output current of the motor. When the output current increases, the magnetic field received by the magnetorheological fluid 23 increases, and the degree of solidification of the magnetorheological fluid 23 becomes higher and higher, indicating that the yield strength of the magnetorheological fluid 22 becomes larger. Externally, the joint stiffness becomes larger. When the load of the mechanical arm becomes larger, in order to balance the load, the torque fluid generated by the clutch must become larger, and the torque of the clutch is generated by the shearing force of the magneto-rheological fluid 23, so the shearing force becomes larger, and the shearing force It increases with the increase of the current, that is, the control current of the clutch must increase, so at this time, the external performance of the joint stiffness increases; when the load of the mechanical arm decreases, in order to balance the load, the torque generated by the clutch must decrease at this time. The clutch driving current decreases, and the joint stiffness becomes smaller externally. Only when the external force is lower than the shear resistance of the magnetorheological fluid 23, the magnetorheological fluid 22 is in a solid-like state; when the external force exceeds the shear resistance of the magnetorheological fluid 23, the flux linkage of the magnetorheological fluid 23 At this time, the magnetorheological fluid 23 is in a liquid state. Therefore, if the external torque is too large, the stiffness of the clutch will drop sharply in an instant to protect the motor and the mechanical arm. If it collides with a person, it can also protect the safety of the person.

In this embodiment, the control of the servo motor driver 20 can realize the stepless speed regulation of the joint speed and the variable joint stiffness with different loads. Both the stiffness and the speed are controllable, and the safety of the joint can be realized while maintaining the performance of the joint. sex. In the event of a collision, it can protect the safety of motors, robotic arms and people. It can realize the conversion of joint rigidity and softness, and ensure the accuracy of end motion.

Claims (7)

1, a kind of safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid, comprise actuating unit, transmission mechanism, output mechanism, driving sensing element, transmission mechanism is connected with output mechanism, it is characterized in that, also comprise becoming rigidity mechanism that described change rigidity mechanism is exactly a clutch with magnetic rheologic liquid, clutch with magnetic rheologic liquid is connected with transmission mechanism with actuating unit

Described driving sensing element comprises motor servo driver and motor encoder, motor servo driver is connected with motor encoder in the joint by the motor encoder line, link to each other with industrial computer by the CAN line, motor driver utilizes speed ring to regulate joint velocity by the motor encoder feedback, and utilize current loop control motor output current, thereby control clutch with magnetic rheologic liquid internal magnetic field intensity, and then control joint stiffness and clutch with magnetic rheologic liquid carry-over moment.

2, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 1, it is characterized in that, described clutch with magnetic rheologic liquid comprises driving shaft, magnetic flow liquid, driving link, magnetizing coil, rotor, rolling bearing, driven shaft, the driving link that connects with driving shaft is a columniform housing, rotor connects with driven shaft, driven shaft by roller bearings on driving link, be embedded with magnetizing coil on the rotor, magnetic flow liquid is filled in the annular concentric gap of cylindrical housings and driven rotor, and magnetizing coil adopts the closely-spaced distribution of multi-thread circle.

3, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 1 is characterized in that, described magnetic flow liquid is made up of carrier fluid, magnetic-particle, surfactant, and three's weight ratio is: 60%, 30%, 10%.

4, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 3 is characterized in that, described carrier fluid is selected silicone oil for use, and magnetic-particle is selected carbonyl iron dust for use, and surfactant is selected oleic acid for use.

5, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 1, it is characterized in that, described actuating unit comprises DC servo motor, motor flange, first shaft coupling of being with decelerator, DC servo motor is mounted on the motor flange, motor flange is to be fixed on the shell of joint, and the motor shaft of DC servo motor is connected by first shaft coupling with change rigidity mechanism.

6, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 1, it is characterized in that, described transmission mechanism comprises shaft coupling, power transmission shaft, axle sleeve, bearing block, bearing, be with axle sleeve on the power transmission shaft, bearing is installed on the axle sleeve, bearing is to be contained in the bearing block, and shaft coupling links to each other with change rigidity mechanism.

7, the safe mechanical joint with adjustable stiffness of clutch with magnetic rheologic liquid according to claim 1 is characterized in that, described output mechanism comprises output flange, spacer ring, and the power transmission shaft in output flange and the transmission mechanism is fixed together by screw and spacer ring.

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