KR100484885B1 - A rotary compliant joint with a damper using magneto―rheological fluid and a spring - Google Patents

Abstract

The present invention provides a compliant joint in the rotary compliant joint, to secure the interaction performance and the durability of the joint by using the spring force and the magnetorheological fluid rotation force The purpose is.

According to the present invention, in a compliant joint interconnecting two first and second links 201 and 202 so as to rotate relative to each other, the first joint and the second link 201 and 202 may rotate in connection with the driving unit 300 and rotate about the first link 201. Housing 111 is securely fixed, the one end is rotatably inserted into the housing 111, the other end is connected to the second link 202, the rotor 161, the rotor 161 and the housing 111 Is filled between the magnetorheological fluid 115, which is filled between the inner surfaces of the casing, and the yield stress varies according to the magnetic flux density, and is inserted into the circular groove 112 formed on one surface of the housing 111 facing the second link 202. A rotary compliant joint is provided that includes a spring 169 and a cover 163 secured to the other end of the rotor to close the grooves 112 and interlock with the second link 202 to stretch the plurality of springs 169. do.

Description

A rotary compliant joint with a damper using magneto--rheological fluid and a spring}

The present invention relates to a joint for a robot, and more particularly, to provide a compliant joint for imparting good compliance in operation to be safe for humans and the environment and at the same time to improve the durability of the robot.

Recently, robots have been developed to provide various services unlike conventional industrial robots, and these robots are directly put into human life to provide various services to humans. More variety of services will be provided to humans.

These service robots must be safe and smoothly interact with humans as well as high speed and high accuracy. To ensure this safety and interaction, compliance is being given to robots. In general, there are two ways to achieve robot compliance: active and passive.

The active compliant method usually obtains force information from a force torque (F / T) sensor attached to the distal end or each joint of the robot arm to generate appropriate control signals. In general, the active compliant method is fundamentally limited in response speed since the control signal is generated according to the sampling time of the controller. As a result, it may not be able to respond quickly to sudden situations such as a collision, which may cause a shock to a human being, and also a robot may be damaged due to an impact caused by a collision.

On the other hand, the passive compliant method can apply a manual mechanism to the distal end or each joint of the robot arm, thereby exhibiting rapid response to external forces.

However, the characteristics and disadvantages of the conventionally developed passive compliant joint operating methods are as follows.

The paper in "Proceeding of the IEEE / RSJ International Conference on Intelligent Robots and Systems (1995), page 407-412" (Title: Development of one-DOF robot arm equipped with mechanical impedance adjuster) is a pseudo Techniques for mechanical impedance regulators with dampers and variable springs are known. However, such a mechanical impedance regulator has a complicated structure and is difficult to implement in reality.

In addition, a series of articles published in "Proceeding of the IEEE / RSJ International Conference on Intelligent Robots and Systems (1995), vol. 1, page 399-406" (Title: series elastic actuators) contains a series of spring-loaded actuators. Related arts are known. In addition, a paper in "Proceeding of the IEEE International Conference on Robotics and Automation (2001), page 348-353" (Title: Design of programmable passive compliance shoulder mechanism) describes a technique for a programmable passive compliant mechanism with a variable spring. This is known.

However, these mechanisms have the disadvantage that they do not employ dampers and thus do not dampen the vibration of the spring.

In addition, the article in the International Journal of Robotics Research (2000), volume 19, number 4, page 307-335 (Title: Human safety mechanisms of human-friendly robots: passive viscoelastic trunk and passively movable base) There is a known technique relating to a joint employing a linear motion spring and a damper between the arms, but such a joint is a joint applied to linear motion and cannot be applied to a rotary motion joint.

As a result of combining existing compliant joint mechanisms, a damper is not used to construct a passive compliant joint, which does not damp the vibration of the spring, or even a damper has a fairly complicated structure to implement the actual implementation. It is difficult to do it, or difficult to apply to rotationally compliant joints as joints applied to linear motion.

On the other hand, if you look at the technology of the rotary damper using a magnetorheological fluid in recent years, Korean Patent Publication No. 1999-0031113 (Invention name: angle limit rotation damper using magnetorheological fluid), Korean Patent Publication No. 1999-0039850 (Name of invention: damping device using magnetorheological fluid and permanent magnet), Republic of Korea Patent Publication No. 1999-0047271 (Name of invention: Brake device combined with a load device using magnetorheological fluid) and US Patent 58,547 (Invention) The controllable brake) has a low rotational torque or an unsuitable configuration for robot joints, and it is difficult to configure because it does not present a technique for converting nonlinear coulomb friction into viscous friction proportional to speed. There is this.

The present invention has been proposed to solve the problems of the prior art as described above, the manual compliant method can be applied to facilitate the interaction between the human and the robot, and can accommodate a large torque applied from the outside The purpose of the present invention is to provide a rotary compliant joint for a robot using a damper and a spring using a magnetorheological fluid.

In order to achieve the above object, the present invention provides a compliant joint interconnecting two first and second links so as to rotate relative to each other, the housing being connected to the driving unit to rotate and rotatably fixed to the first link. And a magnetorheological fluid whose one end is rotatably inserted into the housing and the other end is filled between the rotor connected to the second link, the rotor and the inner surface of the housing, and the viscosity resistance varies according to the magnetic flux density. And a plurality of springs inserted into a circular groove formed on one surface of the housing facing the second link, and fixed to the other end of the rotor to close the groove and extend the plurality of springs while interlocking with the second link. It is characterized by a technical configuration including a cover to be.

Preferably, at least one disc-shaped blade is fixed to one end of the rotor, and a coil is located along both circumferences of both sides of the blade in the housing at a predetermined interval apart from the inside of the housing. The magnetorheological fluid is filled between the coils.

More preferably, the rotor includes a damper control unit fixed to the rotational angular velocity measuring sensor to measure the rotational angular velocity of the rotor and controlling the magnetic flux density to have a viscous resistance proportional to the rotational angular velocity.

In addition, the tensioner of the number of the spring is fixed to the cover of the present invention, each tensioner is located between the spring when the cover closes the groove.

In the following, with reference to the accompanying drawings a preferred embodiment of a damper and a compliant joint using a magnetorheological fluid according to the present invention will be described in detail.

1 is a partial cross-sectional view showing an example of applying the compliant joint to the robot according to an embodiment of the present invention, Figure 2 is a cross-sectional view schematically showing the damper portion and the spring portion of the joint shown in FIG. 3 is an exploded perspective view showing the spring portion shown in Figure 2, Figure 4a is a cross-sectional view showing the operation of the spring portion when no external force is applied to the output link shown in Figure 1, Figure 4b is an output link shown in Figure 1 Is a cross-sectional view showing the operating relationship of the spring portion when an external force is applied in a clockwise direction, FIG. 4C is a cross-sectional view showing the operating relationship of the spring portion when an external force is applied in a counterclockwise direction to the output link shown in FIG. 1 is a perspective view illustrating only the damper unit illustrated in FIG. 1, and FIG. 6 is a graph illustrating a change in torque according to a current applied to the damper unit illustrated in FIG. 5.

FIG. 1 illustrates an embodiment in which a compliant joint 100 using a damper and a spring using a magnetorheological fluid is installed in a robot arm, and is illustrated to explain in more detail an operation relationship of the compliant joint 100. will be. Hereinafter, the function of the compliant joint will be described first with reference to FIG. 1, and then, the components and the operating relationship will be described.

The compliant joint 100 is connected in a relative rotation between the output link 202 and the base link 201. The reducer 310 is positioned between the base link 201 and the joint 100, and the rotational force of the motor 300 installed in the base link 201 is transmitted to the housing 111 of the joint 100 through the reducer 310. Is passed on. When the housing 111 of the joint 100 is driven as described above, the torque of the spring 160 and the damper 110 connected in parallel between the housing 111 and the output link 202 is combined to form the rotor 161. Rotate Rotation of the rotor 161 rotates the output link 202 connected to the rotor 161.

On the contrary, when the force is applied to the output link 202 to rotate, the housing 111 integral with the output of the reducer 310 is decelerated and rotated by the reduction ratio of the reducer 310 so that the force applied to the output link 202 is reduced. Has little effect on the housing 111. That is, the output link 202 rotates in the direction in which the force is applied, but the housing 111 hardly rotates by the applied force, and only the spring 169 of the spring portion 160 is compressed. When the force applied after the spring 169 is compressed in this way is removed, the output link 202 vibrates and stops due to the damping effect generated by the elastic restoring force of the spring 169 and the damper unit 110. .

As described above, the joint 100 of the present invention rotates the output link 202 integral with the rotor 161, causing less vibration by the spring 160 and the damper 160 during normal operation. When an external force is applied to the output link 202 due to a collision, the output link is manually pushed and rotated by the compression effect of the spring so that a small force is transmitted to the collided object and the reducer output. It is a compliant joint that causes link 202 to stop slowly.

Meanwhile, although not shown in FIG. 1, the components that are not described include the small pulley 301 fixed to the rotation shaft of the motor 300, the large pulley 305 fixed to the input shaft of the reducer 310, and the small pulley 301. The timing belt 303 surrounding the large pulley 305, the rotation of the small pulley 301 is transmitted to the large pulley 305 by the timing belt 303, whereby the rotation of the motor 300 is reduced 310 is transmitted to the input shaft.

Hereinafter, a compliant joint according to an embodiment of the present invention shown in FIG. 1 will be described in more detail.

As shown in FIG. 2, the compliant joint 100 is largely divided into a damper unit 110 and a spring unit 160. The damper unit 110 includes a rotor 161, a disc-shaped blade 162 fixed to one end of the rotor 161, a housing 111 surrounding the rotor 161 and the blade 162, and a housing 111. Magneto Rheological Fluid (MRF) (115) filled in the inside of the) and the coil 117 is positioned up and down along the circumference of the blade 162 to generate the magnetic flux by the supplied current do.

Here, the magnetorheological fluid 115 is a non-colloidal solution in which particles having a micron size magnet are dispersed in a non-conductive solvent such as silicon oil or mineral oil. When the magnetic field is not loaded, the magnetic particles are dispersed. Although Newton has a fluid property, when the magnetic field is loaded, the dispersed magnetic particles are polarized, and the magnetic particles are connected in parallel with the loaded magnetic field so that the Bingham fluid property has a shear yield stress at the initial stage without the shear strain.

On the other hand, as shown in Figure 3, the spring 160 closes the open upper surface of the housing 111 and the disc-shaped cover 163 is fixed to the other end of the rotor 161 in the center and the housing ( A plurality of springs 169 inserted and positioned in the grooves 112 formed along the upper circumference of the upper surface of the 111 and between the springs 169 when the upper surface of the housing 111 is closed by the cover 163. And a spring tensioner 165 fixed to the cover 163 to be inserted and positioned.

In addition, as shown in Figure 2, the rotational angular velocity measuring sensor 119 is installed around the middle of the rotor 161 to measure the rotational angular velocity of the rotating rotor 161, in the rotational angular velocity measuring sensor 119 The measured rotational angular velocity value is converted into an electrical signal and fed back to the damper control unit 120. In this way, the current value supplied to the coil 117 is proportionally determined according to the rotational angular velocity value fed back to the damper control unit 120.

And, the control algorithm of the damper control unit 120 for controlling the operation of the damper unit 110 will be described in detail later, the operation relationship of the joint 100 when an external force is applied to the output link 202 below. I will explain in detail first.

As described above, when the housing 111 rotates, the rotor 161 rotates by combining the torques of the spring 160 and the damper 110. As such, the rotation of the rotor 161 rotates the cover 163 integrally formed and the output link 202 fixed to the cover 163. When an external force is applied to the output link 202 in this state, the output link 202 rotates in the direction in which the force is applied.

4A is a spring state when no external force is applied to the output link 202, and FIGS. 4B and 4C show a state of the spring 169 contracted while the output link 202 is rotated in accordance with the direction of the external force. to be.

As shown in FIG. 4A, when no external force is applied, the output link 202 rotates according to the rotation of the housing 111 because the plurality of springs 169 push the spring tensioner 165 to a constant elasticity. 4B and 4C, while the output link 202 is rotated by an external force, each spring 169 is pushed and contracted by the spring tensioner 165 to generate an elastic restoring force. In this state, if the damper unit 110 does not exist, the output link 202 may be restored to the state of FIG. 4A by causing the vibration of the output link 202 several times due to the elasticity of the springs 169. Will not be appropriate for the robot's function.

The damper unit 110 serves to appropriately reduce vibration of the spring 169 when external force is applied and when rotational force is transmitted to the housing 111 by the action of the motor 300 and the reducer 310. Looking at the operation relationship of the damper unit 110, the rotational angular velocity sensor 119 fixed to the rotor 161 measures the sudden change in the rotational angular velocity of the rotor 161, the electrical signal according to the measured rotational angular velocity To generate and feed back to the damper control unit 120. The damper controller 120 supplies a current proportional to the input rotational angular velocity value to the coil 117.

As such, the current supplied to the coil 117 generates a magnetic flux, and the magnetorheological fluid 115 has a Bingham fluid property due to the magnetic flux. The blade 162 accommodated in the magnetorheological fluid 115 resists the rotational force of the rotor 161 to rotate by the elasticity of the spring 169 while its rotational speed is slowed.

On the other hand, as shown in Figure 5, the amount of current supplied and the torque generated is proportional. That is, in the present invention, when the external force acts quickly and largely, the amount of current supplied to the coil 117 increases, and the torque generated accordingly increases.

Hereinafter, a damping control technique for converting the nonlinear coulomb friction characteristic of the magnetorheological fluid 115 into linear viscous friction will be described.

When the nonlinear coulomb friction characteristic of the damper is approximately expressed, it can be expressed as Equation 1 below.

Where I is the current flowing through the coil, sign () is a function that produces a value of +1 if the variable in parentheses is positive, -1 if negative, and 0 if zero, Is the rotational angular velocity, τ _MRD is the torque of the magnetorheological fluid damper, and slope is the proportional coefficient of current and torque.

When the damper control unit 120 supplies a current to the coil 117 with the current value calculated by Equation 2 below, the magnetorheological fluid 115 has a linear viscous damping property as shown in Equation 3 below.

Where B is the desired viscosity damping coefficient.

As described in detail above, the compliant joint of the present invention has a function of a passive compliant with respect to external force applied by using a spring, and includes a damper portion that damps the vibration of such a spring, The impact can be reduced when a robot, a surrounding object, or a person collides with each other. As the impact is reduced, the impulse applied to the joint and the object can be minimized to prevent the breakage and accident of the joint.

Although the technical idea of the damper using the magnetorheological fluid of the present invention and the compliant joint using the spring have been described above with the accompanying drawings, the present invention has been described by way of example only and is not intended to limit the present invention. no.

1 is a partial cross-sectional view showing an example of applying the compliant joint to a robot according to an embodiment of the present invention,

2 is a cross-sectional view schematically showing a damper portion and a spring portion of the joint shown in FIG.

3 is an exploded perspective view showing the spring portion shown in FIG.

Figure 4a is a cross-sectional view showing the operating relationship of the spring when no external force is applied to the output link shown in Figure 1,

Figure 4b is a cross-sectional view showing the operation of the spring when the external force is applied to the output link shown in Figure 1 in the clockwise direction,

4C is a cross-sectional view illustrating an operation relationship of the spring unit when an external force is applied counterclockwise to the output link shown in FIG. 1,

5 is a perspective view illustrating only the damper unit illustrated in FIG. 1;

FIG. 6 is a graph illustrating a change in torque according to a current applied to the damper unit illustrated in FIG. 5.

     Explanation of symbols on the main parts of the drawings

  100: joint 110: damper part

  111 housing 115 magneto Rheological fluid

  117: coil 119: rotational angular velocity measuring sensor

  120: damper control unit 160: spring unit

  161: rotor 162: blade

  165: spring tensioner 169: spring

  201, 202: Link 300: Motor

Claims (4)

A compliant joint interconnecting two first and second links so that they rotate relative to each other, A housing connected to the drive unit to rotate and rotatably fixed to the first link; A rotor having one end rotatably inserted into the housing and the other end connected to the second link; A magnetorheological fluid filled between the rotor and the inner surface of the housing and having a yield stress changed according to magnetic flux density, A plurality of springs inserted into a circular groove formed on one surface of the housing facing the second link; A cover fixed to the other end of the rotor to close the groove and extend and contract the plurality of springs while interlocking with the second link, At least one disc-shaped blade is fixed to one end of the rotor, and a coil is positioned along both circumferences of both sides of the blade at a predetermined distance from the inside of the housing, and between the blade and the coil. The compliant joint, characterized in that the magnetorheological fluid is filled. delete The method of claim 1, The rotor is fixed to the rotational angular velocity measuring sensor to measure the rotational angular velocity of the rotor, a compliant joint, characterized in that it comprises a damper control unit for controlling the magnetic flux density to have a viscous resistance proportional to the rotational angular velocity. The method of claim 1, The tensioner is fixed to the cover as much as the number of springs, and each of the tensioners is located between the springs when the cover closes the groove.