CN113246113A

CN113246113A - Variable-rigidity mechanical arm system driven by magnetorheological fluid, control method and robot

Info

Publication number: CN113246113A
Application number: CN202110426297.8A
Authority: CN
Inventors: 周俊杰; 张凌钰; 马惠臣
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-04-20
Filing date: 2021-04-20
Publication date: 2021-08-13

Abstract

The invention belongs to the technical field of mechanical arms and discloses a variable-rigidity mechanical arm system driven by magnetorheological fluid, a control method and a robot, wherein the variable-rigidity mechanical arm system driven by the magnetorheological fluid is provided with a hydraulic cylinder; the liquid cylinder is filled with magnetorheological fluid; one side of the hydraulic cylinder is provided with a four-way joint, and three pipe orifices of the four-way joint are respectively connected with an inlet of the electromagnetic valve through air pipes; the three air pipe joints are respectively connected with the outlets of the electromagnetic valves through air pipes; the piston end of the hydraulic cylinder is provided with a telescopic electric push rod. An electromagnetic valve is arranged at the right front side edge of the bottom fixing frame; two ends of the bottom fixing frame are respectively provided with a fixing corner connector; the inner side of the fixed corner brace is fixed with an electromagnet; a soft mechanical arm is arranged in the middle of the bottom fixing frame. The invention can effectively control the contact force of the tail end to achieve the effect of compliance. The variable-rigidity mechanical arm can ensure that the control of the contact force is more flexible and safer, and can be applied to automatic sample collection in the medical field.

Description

Variable-rigidity mechanical arm system driven by magnetorheological fluid, control method and robot

Technical Field

The invention belongs to the technical field of mechanical arms, and particularly relates to a variable-rigidity mechanical arm system driven by magnetorheological fluid, a control method and a robot.

Background

At present, compared with a rigid mechanical arm, the soft mechanical arm has the advantages of high degree of freedom, high flexibility, high safety, high environmental adaptability and the like. However, the application and transmission of force is difficult due to the poor load resistance of the soft material. Therefore, it is important to design a variable stiffness mechanical arm capable of realizing rigid-flexible coupling.

The variable-rigidity mechanical arm combines the multi-degree-of-freedom, flexibility and safety of a soft mechanical arm and the effective force control of a rigid mechanical arm, and can be applied to the aspects of grabbing, surgical medical treatment, remote exploration, search and rescue and the like. At present, the variable rigidity of the mechanical arm can be realized by using the principles of antagonism, blocking mechanism and the like and intelligent materials such as dielectric elastomer, shape memory polymer, electric/magnetic rheological fluid and the like.

For example, chinese patent application No. CN201810935837.3 entitled "a variable stiffness soft mechanical arm controlled by electrorheological fluid" describes: the variable-rigidity middle device is filled with electrorheological fluid, and the liquid-solid-liquid conversion of the electrorheological fluid is realized by changing the voltage, so that the rigidity change is realized; three air cavities are uniformly distributed around the soft mechanical arm body, and the soft mechanical arm body is connected with a quick connector through a sealing device to convey air so as to bend the soft mechanical arm body. The variable stiffness module is controlled by the voltage, and the bending is controlled by the conveying gas, so that the problems of inconvenient operation and the need of various control devices are caused.

The magnetorheological fluid is a controllable fluid which can be instantly converted into a Bingham body with high viscosity and low fluidity from a Newtonian fluid under the action of a magnetic field, and is usually applied to structures such as valve seals, dampers, brakes, clutches and the like.

Through the above analysis, the problems and defects of the prior art are as follows:

(1) the existing soft mechanical arm has poor load capacity and is difficult to apply and transmit force; the existing rigid mechanical arm has low degree of freedom, low flexibility and low environmental adaptability;

(2) the rigidity changing module of the existing variable-rigidity mechanical arm is controlled by the voltage, and the bending is controlled by conveying gas, so that the problems of inconvenience in operation and need of various control devices are caused.

(3) The existing invention using electrorheological fluid to control similar rigidity needs very large voltage and is unsafe.

(4) If the rigid mechanical arm is required to achieve the effect of soft force, the price is high, and the rigid mechanical arm is difficult to popularize.

The difficulty in solving the above problems and defects is:

(1) the bearing capacity of the soft material is small, and the integral bearing capacity of the soft material is improved by proper rigid-flexible coupling;

(2) the driving voltage of materials such as electrorheological fluid, dielectric elastomer and the like is large, the magnitude order of kV is reached, and the potential safety hazard is high during use;

(3) the force self-sensing of the soft mechanical arm is not easy to realize;

(4) the real-time performance is not high;

(5) the motion accuracy is not high.

The significance of solving the problems and the defects is as follows:

(1) the device can apply proper force to work according to the requirement;

(2) the end force of the mechanical arm is more flexibly controlled, and the human-computer interaction is more safely carried out;

(3) the motion is controlled more accurately;

(4) the cost is reduced, and task equipment such as remote B-ultrasonic shooting and remote throat swab collection can be popularized, so that the work of medical personnel is more convenient and safer.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a variable-rigidity mechanical arm system driven by magnetorheological fluid, a control method and a robot.

The invention is realized in such a way that the magnetorheological fluid driven variable stiffness mechanical arm system is provided with a hydraulic cylinder;

the liquid cylinder is filled with magnetorheological fluid;

a four-way joint is arranged on one side of the hydraulic cylinder, and three pipe orifices of the four-way joint are respectively connected with an inlet of the electromagnetic valve through air pipes; the three air pipe joints are respectively connected with the outlets of the electromagnetic valves through air pipes;

and a telescopic electric push rod is arranged at the piston end of the hydraulic cylinder.

Further, the variable-rigidity mechanical arm system driven by the magnetorheological fluid is also provided with a bottom fixing frame;

an electromagnetic valve is arranged at the right front side edge of the bottom fixing frame;

two ends of the bottom fixing frame are respectively provided with a fixing corner connector; an electromagnet is fixed on the inner side of the fixed corner brace;

a soft mechanical arm is arranged in the middle of the bottom fixing frame;

the soft mechanical arm is provided with a silica gel casting base body, and the bottom of the silica gel casting base body is provided with an air pipe joint; a mechanical arm base is arranged below the air pipe joint; the arm base outside is provided with 3 trachea, 3 trachea are angle evenly distributed.

Further, the magnetorheological fluid-driven variable-stiffness mechanical arm system further comprises:

a power source; the power supply is connected with the singlechip, the electric push rod and the electromagnet through circuit connecting wires; the single chip microcomputer is connected with the electromagnet, the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve through circuit connecting wires.

Another object of the present invention is to provide a method for controlling a magnetorheological fluid-driven variable stiffness robot arm of a magnetorheological fluid-driven variable stiffness robot arm system, the method comprising:

the single chip microcomputer controls the electric push rod to stretch and push the piston to change the volume sum of the magnetorheological fluid in the mechanical arm cavity; the electromagnetic valve is used for controlling the opening and closing of each cavity of the mechanical arm to realize the pose control of the mechanical arm; meanwhile, the electromagnet is controlled by the single chip microcomputer to apply a magnetic field to change the integral rigidity of the mechanical arm, and the variable rigidity mechanical arm driven by the magnetorheological fluid is controlled.

Further, the control method of the variable-rigidity mechanical arm driven by the magnetorheological fluid comprises the following steps:

firstly, controlling the opening and closing of a three-cavity electromagnetic valve and the pushing and pulling of an electric push rod to realize the volume of magnetorheological fluid respectively introduced into three cavities;

step two, coupling control of the three-cavity electromagnetic valve and the electric push rod is carried out to realize integral motion control of the soft mechanical arm;

step three, applying voltage to the two ends of the electromagnet at a specified time, and increasing the viscosity of the magnetorheological fluid so as to increase the rigidity, thereby changing the integral rigidity of the soft mechanical arm;

further, in the second step, the performing the soft robot motion control includes:

(1) the single chip microcomputer controls the electric push rod to extend, and pushes the piston to enable magnetorheological fluid in the hydraulic cylinder to be filled into the specified cavity of the soft mechanical arm through the control of the electromagnetic valve, and the specified cavity of the mechanical arm extends correspondingly;

(2) the single chip microcomputer controls the electric push rod to stretch and retract, the piston is retracted, magnetorheological fluid in the designated cavity of the mechanical arm returns to the hydraulic cylinder through the control of the electromagnetic valve, and the designated cavity of the corresponding mechanical arm contracts.

It is another object of the present invention to provide a computer readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the magnetorheological-fluid-driven variable stiffness robotic arm control method.

Another object of the present invention is to provide a computer apparatus comprising a memory and a processor, the memory storing a computer program, the computer program, when executed by the processor, causing the processor to execute the method of controlling a magnetorheological-fluid-driven variable stiffness mechanical arm.

Another object of the present invention is to provide a robot, which carries a variable stiffness robot arm system driven by magnetorheological fluid; and operating the variable-rigidity mechanical arm control method driven by the magnetorheological fluid.

Another object of the present invention is to provide an information data processing terminal, where the information data processing terminal is configured to implement the method for controlling a variable-stiffness mechanical arm driven by magnetorheological fluid.

By combining all the technical schemes, the invention has the advantages and positive effects that: the invention provides a mechanical arm with variable rigidity, which can effectively control the contact force of the tail end to achieve the effect of compliance.

The variable-rigidity mechanical arm can enable the control of contact force to be more flexible and safer, can be applied to automatic sample collection (such as throat swab collection) in the medical field, and can also be applied to aspects of massage, physical therapy and the like of a robot.

The invention takes the magnetorheological fluid as the driving deformation of the medium and adjusts the rigidity by the change of the fluid property of the magnetorheological fluid under the action of the magnetic field. The invention uses the electric push rod as power to push the piston to change the volume sum of the magnetorheological fluid in the cavity of the mechanical arm, and uses the electromagnetic valve as the control of the opening and closing of each cavity of the mechanical arm, thereby causing the pose of the mechanical arm to change; and the overall stiffness of the mechanical arm is changed by applying a magnetic field.

Due to the characteristic that the viscosity of the magnetorheological fluid changes along with the magnetic field, before and after the voltage is applied to the electromagnet, the magnetorheological fluid is converted from low-viscosity high-fluidity Newtonian fluid into a high-viscosity low-fluidity Bingham body, so that the rigidity of the whole mechanical arm is changed, and the bearing capacity is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a magnetorheological fluid driven variable stiffness mechanical arm system according to an embodiment of the invention.

Fig. 2 is a schematic view of a magnetorheological fluid driven variable stiffness mechanical arm system according to an embodiment of the invention.

Fig. 3 is a schematic perspective view of a magnetorheological fluid driven variable stiffness mechanical arm system according to an embodiment of the present invention.

Fig. 4 is a structural diagram of a variable stiffness robotic arm provided in an embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a variable stiffness robotic arm according to an embodiment of the present invention.

Fig. 6 is a schematic perspective view of a mechanical arm with variable stiffness according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of a circuit connection object of the variable stiffness robotic arm system according to the embodiment of the present invention.

Fig. 8 is a schematic circuit diagram of a variable stiffness robotic arm system according to an embodiment of the present invention.

Fig. 9 is a flowchart of a method for controlling a variable-stiffness mechanical arm driven by magnetorheological fluid according to an embodiment of the present invention.

In the figure: 1. fixing the corner connectors; 2. an electromagnet; 3. a soft mechanical arm; 4. a gas pipe joint; 5. an electromagnetic valve; 6. a bottom mount; 7. a four-way joint; 8. a hydraulic cylinder 9 and an electric push rod; 10. casting a matrix by using silica gel; 11. an air tube; 12. mechanical arm base.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In view of the problems in the prior art, the present invention provides a magnetorheological fluid driven variable stiffness mechanical arm system, and the present invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1 to 6, the magnetorheological fluid driven variable stiffness mechanical arm system provided by the embodiment of the invention is provided with a hydraulic cylinder 8;

the liquid cylinder 8 is filled with magnetorheological fluid; a four-way joint 7 is arranged on one side of the hydraulic cylinder 8, and three pipe orifices of the four-way joint 7 are respectively connected with the inlet of the electromagnetic valve 5 through air pipes; the three air pipe joints 4 are respectively connected with the outlets of the electromagnetic valves 5 through air pipes; the piston end of the hydraulic cylinder 8 is provided with a telescopic electric push rod 9.

The magnetorheological fluid driven variable-rigidity mechanical arm system provided by the embodiment of the invention is also provided with a bottom fixing frame 6; the electromagnetic valve 5 is arranged at the right front side edge of the bottom fixing frame 6; two ends of the bottom fixing frame 6 are respectively provided with a fixed corner connector 1; an electromagnet 2 is fixed on the inner side of the fixed corner brace 1; a soft mechanical arm 3 is arranged in the middle of the bottom fixing frame 6; the soft mechanical arm 3 is provided with a silica gel casting base body 10, and the bottom of the silica gel casting base body 10 is provided with an air pipe joint 4; a mechanical arm base 12 is arranged below the air pipe joint 4; the arm base 12 outside is provided with 3 trachea 11, and 3 trachea 11 are angle evenly distributed.

As shown in fig. 7 to 8, the magnetorheological fluid driven variable stiffness mechanical arm system according to the embodiment of the present invention further includes:

The method for controlling the variable-rigidity mechanical arm driven by the magnetorheological fluid comprises the following steps:

As shown in fig. 9, the method for controlling a variable-stiffness mechanical arm driven by magnetorheological fluid according to an embodiment of the present invention includes the following steps:

s101, controlling the opening and closing of the three electromagnetic valves and the pushing and pulling of the electric push rod to control the volume of the magnetorheological fluid respectively introduced into the three cavities;

s102, realizing the overall motion control of the soft mechanical arm by coupling control of the electromagnetic valve and the electric push rod;

s103, applying voltage to the two ends of the electromagnet at the appointed time, increasing the viscosity of the magnetorheological fluid, and reducing the fluidity, so that the integral rigidity of the soft arm is improved.

In step S102, the performing of the soft mechanical arm motion control according to the embodiment of the present invention includes:

The technical effects of the present invention will be further described with reference to specific embodiments.

Example 1:

fig. 1 to 3 show the structural composition of the variable stiffness robot arm system of the present invention, fig. 4 to 6 show the structural composition of the variable stiffness robot arm of the present invention, and fig. 7 shows a drive control circuit of the variable stiffness robot arm system of the present invention. The invention is described by combining the above figures, and comprises a fixed angle code, an electromagnet, a soft mechanical arm, an air pipe joint, an electromagnetic valve, a system bottom fixing frame, a four-way joint, a hydraulic cylinder, an electric push rod, magnetorheological fluid, a fixing piece, an air pipe and the like. Three pipe orifices of the four-way joint are respectively connected with the inlet of the electromagnetic valve through air pipes, and three air pipe joints are respectively connected with the outlet of the electromagnetic valve through air pipes. The liquid cylinder is filled with magnetorheological fluid. When the electric push rod extends, magnetorheological fluid in the cylinder is filled into the specified cavity of the soft mechanical arm through the control of the electromagnetic valve, the cavity extends, when the electric push rod retracts, the magnetorheological fluid in the cavity returns to the liquid cylinder through the control of the electromagnetic valve, and the cavity retracts. The soft mechanical arm realizes certain movement under the action of the extension and contraction of the electric push rod and the opening and closing of the electromagnetic valves of the cavities. By applying a certain voltage to the two ends of the two electromagnets at a specified time, the magnetorheological fluid in the cavity is magnetized, the viscosity is increased, and the integral rigidity of the soft mechanical arm is increased. The magnetic field can be changed by changing the voltage at the two ends of the electromagnet, so that the whole soft mechanical arm can be changed within a certain rigidity range. Objects in specific scenes such as a throat swab sampling rod and the like can be fixed in the groove at the tail end of the soft mechanical arm so as to complete corresponding tasks.

Example variable stiffness robotic arm system actions:

as shown in fig. 3, when 1 electromagnetic valve is opened and the other 2 electromagnetic valves are closed to control the electric push rod to push for 2mm, the soft mechanical arm bends, and the voltage applied to the two ends of the electromagnet is 12V, which is larger than the end force of the soft mechanical arm before and after electrification.

The variable rigidity of the mechanical arm can change the contact force of the tail end so as to realize better compliance. The principle is that magnetorheological fluid is filled into a silicon cavity of the mechanical arm to be driven to deform, the magnetorheological fluid in the cavity is magnetized by applying a magnetic field, and finally the mechanical arm integrally has high rigidity.

According to the test data provided by the magnetorheological fluid manufacturer, when the exciting current is changed from 0A to 4A, the shear stress of the magnetorheological fluid is increased from 0 to 72 kPa. The soft mechanical arm has higher shear stress and higher magnetic saturation yield stress under a higher magnetic field, and can meet the requirement of rigidity change of the soft mechanical arm.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A control method for a variable-rigidity mechanical arm driven by magnetorheological fluid is characterized by comprising the following steps:

2. The method for controlling a magnetorheological-fluid-driven variable-stiffness mechanical arm according to claim 1, comprising the steps of:

step one, controlling the motion of a soft mechanical arm;

step two, applying voltage to two ends of the electromagnet at a specified time to change the integral rigidity of the soft mechanical arm;

and step three, performing mechanical arm control through an electromagnetic valve and an electromagnet.

3. The method for controlling a variable stiffness robotic arm actuated by magnetorheological fluid according to claim 2, wherein the first step of performing the soft robotic arm motion control comprises:

4. The variable-rigidity mechanical arm system driven by the magnetorheological fluid is characterized in that the variable-rigidity mechanical arm system driven by the magnetorheological fluid is provided with a hydraulic cylinder;

the liquid cylinder is filled with magnetorheological fluid;

5. The magnetorheological-fluid-driven variable stiffness robotic arm system according to claim 4, further comprising a bottom mount;

a soft mechanical arm is arranged in the middle of the bottom fixing frame;

6. The magnetorheological-fluid-driven variable stiffness robotic arm system according to claim 4, further comprising:

7. A computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the magnetorheological-fluid-driven variable stiffness robotic arm control method of any one of claims 1 to 3.

8. A computer readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the magnetorheological-fluid-driven variable stiffness robotic arm control method of any one of claims 1 to 3.

9. A robot, characterized in that the robot is provided with a magnetorheological fluid driven variable stiffness mechanical arm system according to any one of claims 4 to 6, and a magnetorheological fluid driven variable stiffness mechanical arm control method according to any one of claims 1 to 3 is operated.

10. An information data processing terminal, characterized in that the information data processing terminal is used for implementing the magnetorheological fluid driven variable stiffness mechanical arm control method according to any one of claims 1 to 3.