JP7203379B2 - Actuator system - Google Patents

Description

TECHNICAL FIELD The present invention relates to an actuator system that generates a driving force by the hydraulic pressure of a working fluid, and more particularly to an actuator system that enables adjustment of the pressure resistance and frictional force of a seal interposed in a sliding portion.

Humanoid robots, care support robots, surgery support robots, etc. that coexist in human living spaces will drive in consideration of these situations when unexpected collisions or contact with humans occur during their operation. Compliance performance (flexibility) is required. Conventionally, an actuator to which a servo system is applied is used in order to ensure the compliance performance (see, for example, Patent Document 1, etc.).

However, in the servo system, due to the complexity of the system and the limitations of the frequency response inherent in the controller, it does not adequately cope with sudden and impulsive inputs. Therefore, robots that coexist with humans are required to have new flexible actuators that can quickly respond to unexpected application of external forces. Accordingly, the present inventors have already proposed a direct acting compliant actuator using a fluid pressure cylinder and a rotary compliant actuator using a vane type rotary actuator based on such a demand. (See Patent Documents 2 and 3).

The direct-acting compliant actuator includes a fluid pressure cylinder, which is an operating part that generates a driving force by the pressure of a magnetic functional fluid whose viscosity changes according to the magnetic field strength, and a magnetic functional fluid inside the fluid pressure cylinder. and control means for controlling the operation of the fluid pressure cylinder and controlling the supply of the magnetic functional fluid to the fluid pressure cylinder by the fluid supply means. The fluid pressure cylinder has a hollow cylinder tube and a piston that is arranged to be movable in the internal space of the cylinder tube and that moves to generate the driving force. Here, the internal space of the cylinder tube is partitioned by the piston into first and second chamber spaces each filled with a magnetic functional fluid. Furthermore, the piston is formed with a communication passage that communicates the first and second chamber spaces, and is provided with an electromagnet that generates a magnetic field inside the communication passage. In addition, the control means controls the flow rate of the magnetic functional fluid supplied into each chamber space by the fluid supply means, controls the state of the magnetic field in the communication channel, and changes the viscosity of the magnetic functional fluid. The driving state of the piston is changed by adjusting the flow rate of the magnetic functional fluid passing through the communication channel.

The rotary compliant actuator comprises a rotary actuator as an operating part that generates a driving force by the pressure of the magnetic functional fluid, fluid supply means for supplying the magnetic functional fluid to the rotary actuator, and operation of the rotary actuator. a control means for controlling and controlling the supply of the magnetic functional fluid to the rotary actuator by the fluid supply means. The rotary actuator includes a housing having a working fluid chamber in which a magnetic functional fluid is accommodated, a rotating unit rotatably provided in the working fluid chamber, a fixed arrangement in the working fluid chamber, and rotation of the rotating unit. and a stopper that regulates the Here, the rotating unit includes a drive shaft that is rotatably arranged in the housing and generates a driving force, and is fixed to the drive shaft so as to be rotatable integrally with the drive shaft, and the working fluid chamber is divided into two first and second chambers. It is divided into chamber spaces and has vanes provided with communication passages for communicating these chamber spaces, and magnetic field generating means for generating a magnetic field concentrated inside the communication passages. In addition, the control means controls the flow rate of the magnetic functional fluid supplied into each chamber space by the fluid supply means, controls the state of the magnetic field in the communication channel, and changes the viscosity of the magnetic functional fluid. The driving state of the rotating unit is changed by adjusting the flow rate of the magnetic functional fluid passing through the communication channel.

JP 2013-212564 A JP 2016-142320 A JP 2018-71776 A

In the direct-acting compliant actuator proposed in Patent Document 1, the piston moves in the internal space of the cylinder tube. In order to prevent leakage of the magnetic functional fluid from the sliding portion, the moving portion is provided with a sealing material made of rubber or the like, or a solid seal such as a ring. Similarly, in the rotary compliant actuator proposed in Patent Document 2, a solid seal is interposed in the sliding portion between the inner wall portion of the housing, the outer surface portion of the stopper, and the rotating unit, so that the sliding portion is prevented from Leakage of the magnetic functional fluid is prevented.

However, when the magnetic functional fluid, which is the working fluid of the actuator, is used in a high-pressure environment, using a solid seal designed to prevent leakage of the magnetic functional fluid from the sliding parts causes damage to the piston and rotation. A large sliding resistance of the solid seal occurs when the unit is in motion. In this case, there is not much problem if it is applied for output in a large range, but in human coexistence robots and work support robots that require environmental applicability, such a large sliding resistance is a safety issue. It causes a decrease in controllability. In addition, when a small external force acts on the operating portion of the actuator, back drivability is reduced due to the large sliding resistance described above. These problems cannot be improved even by adjusting the size of the communication channel or the magnetic field generated in the communication channel.

The present invention has been devised based on such a problem, and its object is to change the sliding resistance to improve backdrivability while realizing low sliding resistance compared to conventional solid seals. To provide a low-sliding actuator system capable of obtaining desired compliance performance by active adjustment.

In order to achieve the above object, the present invention mainly provides an actuator system comprising an actuator body for generating a driving force by the hydraulic pressure of a working fluid, and fluid supply means for supplying the working fluid to the actuator body, The actuator body is connected to the fluid supply means and divides the working fluid chamber into a working fluid chamber in which the working fluid is stored, and divides the working fluid chamber into a plurality of chamber spaces. It comprises an operating section that transmits the driving force to the outside by the pressure difference between the chamber spaces, and a magnetic field generating means that generates a magnetic field, and the operating section is slidable with respect to the working fluid chamber through a gap. is provided in the gap, the magnetic field acts on the gap, and a magnetic functional fluid whose viscosity changes according to the magnetic field strength is interposed, and the magnetic field generating means is provided so as to be able to adjust the magnetic field strength, By changing the viscosity of the magnetic functional fluid in the gap, the sliding resistance of the operating portion with respect to the working fluid chamber is made variable.

In the present invention, the magnetic functional fluid functions as a fluid seal with fluidity, so that the frictional resistance between the sliding members via the seal is greatly reduced compared to the case where a conventional solid seal is used, Back drivability higher than that of the conventional structure can be obtained. In addition, by changing the strength of the magnetic field acting on the magnetic functional fluid, it is possible to actively adjust the pressure resistance and frictional force of the sealing portion made of the magnetic functional fluid. As a result, for example, during direct teaching through an external member such as a robot arm connected to the operating part, it is possible to prevent the magnetic field from acting on the seal portion, reduce the sliding resistance of the seal portion, and improve the backdrivability. can. In addition, when it is implemented in a human-collaborative robot, the yield stress of the magnetic functional fluid is adjusted by changing the strength of the magnetic field acting on the magnetic functional fluid, and the yield stress is adjusted like a relief mechanism such as a mechanical seal. When an external force exceeding the stress acts on the moving part, it becomes possible to perform compliance control to operate the moving part according to the external force. In this case, a complicated relief mechanism including a valve, a tank, etc., a complicated circuit configuration, etc. are not required, the size of the entire system can be reduced, and an improvement in the degree of freedom in arranging the actuator can be expected. Further, according to the demonstration experiments by the inventors, in the present invention, the compliance performance is controlled by adjusting the sliding resistance mainly by controlling the magnetic field. It also has higher responsiveness than compliance performance control that mainly controls the supply of working fluid using a pump.

1 is a block diagram showing a schematic configuration of an actuator system according to this embodiment; FIG. 4 is a schematic perspective view of an actuator body; FIG. FIG. 4 is a schematic front view showing the internal structure of the actuator body with the cover removed, along with other partial configurations. Schematic cross-sectional front view of the base. FIG. 4 is an explanatory view schematically attaching a diagram showing a moving state of a magnetic field to FIG. 3 ;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram showing a schematic configuration of an actuator system according to this embodiment. In this figure, the actuator system 10 includes an actuator body 11 that generates a driving force by the fluid pressure of working fluid, a fluid supply means 12 that supplies the working fluid to the actuator body 11, and controls the operating state of the actuator body 11. A control means 13 is provided.

As the working fluid, a magneto-rheological fluid (MR fluid) is used as a magnetic functional fluid whose viscosity changes according to the strength of the acting magnetic field. This MR fluid is a type of functional fluid made by dispersing magnetic particles having ferromagnetism such as ferrite particles with particle diameters on the order of several tens of nanometers in a non-colloidal organic solution. Being constrained underneath changes the apparent viscosity of the liquid. The MR fluid does not flow unless a certain amount of shearing force is applied, and once the flow is generated, the shear stress and the shear rate have a proportional relationship like a Newtonian fluid. Note that the yield stress of the MR fluid, which affects the beginning of flow, increases as the magnetic field becomes stronger within a range up to a predetermined magnetic field strength.

The actuator body 11 is configured as a vane-type rotary actuator, and as shown in FIGS. , a rotating unit 17 arranged to be rotatable inside the base 15 , and a coil unit 18 attached to the side of the base 15 .

As shown in FIGS. 3 and 4, the base 15 has a recess 20 formed in the vicinity of the center and having a generally fan-shaped outer shape in a plan view, and an internal space of the recess 20 which is open to the outside to form a coil unit. 18, and first and second ports 22 and 23 that open to the outside from other two locations in the internal space of the recess 20 and are connected to the fluid supply means 12 are formed. A cover 24 is attached to the surface of the base 15 on the open side of the recess 20 so as to cover the recess 20, as shown in FIG.

As shown in FIG. 3, the embedding member 16 consists of an outer peripheral embedding member 26 fixedly arranged along the arc-shaped outer peripheral region of the inner edge portion forming the inner space of the recess 20, and an inner space of the recess 20. Among them, a central embedded member 27 fixedly arranged near the center of the sector, and a connection embedded fixedly arranged in each groove 21 so as to contact the outer peripheral embedded member 26 and the central embedded member 27 and contact the coil unit 18. and a member 28 .

Here, of the internal space of the recess 20, the remaining space formed with the peripheral embedded member 26 and the central embedded member 27 arranged serves as a working fluid chamber 30 filled with the MR fluid from the fluid supply means 12. It's becoming Here, the first and second ports 22 and 23 are always in communication with the working fluid chamber 30, so that the MR fluid can be supplied to and discharged from the working fluid chamber 30 by the fluid supply means 12. It's becoming

The rotating unit 17 is arranged in the working fluid chamber 30 and functions as an operating part that transmits driving force to the outside while rotating and sliding in the working fluid chamber 30 with respect to the peripheral embedded member 26 and the central embedded member 27 . . The rotary unit 17 includes a drive shaft 32 whose one end is fitted in a mounting hole 15A (see FIG. 4) of the base 15 so as to be rotatable near the central embedded member 27 using the central embedded member 27 as a bearing, and a drive shaft 32 integral with the drive shaft 32. and a rotary member 33 which is fixed to and rotatable about a drive shaft 32 and which divides the working fluid chamber 30 into two first and second chamber spaces 30A and 30B.

Here, of the working fluid chamber 30, the first chamber space 30A on the upper right side in FIG. 3 is connected to the first port 22, and the second chamber space 30B on the lower left side in It is connected to the second port 23 . Therefore, when the MR fluid is supplied to one of the ports 22, 23 from the fluid supply means 12, the pressure in the one chamber space 30A, 30B connected to the port 22, 23 increases. The pressure difference between the chamber spaces 30A and 30B causes the rotating member 33 to rotate in the direction of increasing the volume of one of the chamber spaces 30A and 30B. The fluid is discharged outside.

The drive shaft 32 rotates along with the rotation of the rotating member 33, and as shown in FIG. The rotary driving force, which is the output of the actuator main body 11, is transmitted to other members (not shown).

As shown in FIG. 3, the rotary member 33 is slidably arranged through a small gap 35 formed between the outer peripheral embedded member 26 and the central embedded member 27. , the MR fluid can flow into and out of the respective chamber spaces 30A and 30B.

The coil unit 18 includes a substantially U-shaped core member 37 in a side view, which is disposed so as to abut on the connection embedded member 28 embedded in each groove 21 , and a coil 38 wound around the core member 37 . Consists of The coil 38 is supplied with external power from a power supply device 39 arranged outside the actuator body 11, and energizes the coil 38 to generate a magnetic field of arbitrary strength. Therefore, the core member 37, the coil 38, and the power supply device 39 function as magnetic field generating means for generating a magnetic field within the gap 35 by a structure described later.

In the actuator body 11 configured as described above, the base 15 is made of a non-magnetic material with low magnetic permeability such as aluminum, and the embedded member 16, the rotating unit 17 and the core member 37 are made of magnetic material such as electromagnetic stainless steel and iron. It is made of a magnetic material with high magnetic permeability. Therefore, the magnetic field generated by energization of the coil 38 has only a route passing through the core member 37, the connecting embedded member 28, the peripheral embedded member 26, the rotating member 33, and the central embedded member 27, as indicated by the dashed lines in FIG. , a magnetic circuit is formed by these members. At this time, the gaps 35 formed in the sliding portions between the rotating member 33 and the outer peripheral embedded member 26 and central embedded member 27 are filled with the MR fluid. A magnetic field acts. Therefore, by changing the magnetic field intensity with the magnetic field generating means and changing the viscosity of the MR fluid interposed in the gap 35, when the rotating member 33 rotates, the outer peripheral embedded member 26 and the central embedded member 27 Sliding resistance against is variable.

In other words, the magnetic circuit is structured to apply a magnetic field to the MR fluid interposed in the gap 35 in a direction substantially perpendicular to the sliding direction of the rotating member 33 . Therefore, when the magnetic field acts, the magnetic particles in the MR fluid are arranged along the acting direction, and the flow of the MR fluid along the sliding direction in the gap 35 is restricted. Therefore, by adjusting the arrangement density of the magnetic particles at this time with the strength of the magnetic field, the MR fluid in the gap is controlled by the pressure resistance and frictional force of the sliding portion separately from the working fluid that rotates the rotating member 33 . It functions as a fluid seal that makes the

The magnetic circuit preferably has a structure in which magnetic field leakage from the magnetic field generating means to the chamber spaces 30A and 30B is suppressed, and the magnetic field is concentrated in the gap 35 to act. For example, it is preferable to provide a cover made of a non-magnetic material on the outer peripheral surface of the rotating member 33 to suppress magnetic emission to the outside. As a result, a magnetic field having a desired strength can be applied intensively to the gap 35, and the magnetic field strength can be adjusted to change the sliding resistance of the rotating member 33 by adjusting the first and second chambers. The influence on the MR fluid in the spaces 30A, 30B can be reduced.

Although not shown, the fluid supply means 12 includes pipelines connected to the first and second ports 22 and 23, valves appropriately arranged in the pipelines, and MR fluid in the pipelines. , a flow sensor for detecting the flow rate of the MR fluid supplied to the actuator body, and a pressure sensor for detecting the differential pressure between the first and second ports 22 and 23. . The operation of the pump unit and the valves is controlled by the control means 13, and when the pump unit is driven based on this control, the MR fluid is discharged from either the first or second port 22, 23. The MR fluid supplied to one of the chamber spaces 30A and 30B and discharged to the outside of the actuator body 11 through the other of the first and second ports 22 and 23 is the MR fluid in the other chamber space 30A and 30B. Further, when the pump unit is stopped, the MR fluid does not flow into the actuator main body 11 from the outside, and the MR fluid is not discharged to the outside of the actuator main body 11 .

The control means 13 controls the operation of the pump unit of the fluid supply means 12 based on the previously required performance and specifications of the actuator body 11 and the detection results from the various sensors described above, and supplies the fluid to the actuator body 11 . The driving force output through the rotation unit 17 is adjusted by adjusting the flow rate of the MR fluid. In addition, the control means 13 performs magnetic field control to change the strength of the magnetic field flowing through the magnetic circuit, changes the viscosity of the MR fluid interposed in the gap 35, and adjusts the sliding resistance of the rotating member 33. be.

Therefore, according to this embodiment, a slight gap 35 is provided between the peripheral embedded member 26 and the central embedded member 27 and the rotating member 33 sliding against them, and the MR fluid is introduced into the gap 35. Since the structure is such that the strength of the magnetic field acting on the MR fluid is variable, it is possible to adjust the sliding resistance while lowering the sliding resistance compared to the case where a solid seal is used. . For example, when no magnetic field acts in the gap 35, the rotary member 33 can rotate almost freely when an external force acts on the drive shaft 32, and high back drivability can be exhibited. On the other hand, by adjusting the strength of the magnetic field acting in the gap 35, the yield stress of the MR fluid when the rotating member 33 slides is adjusted, and when an external force less than the yield stress acts on the drive shaft 32, , the rotating member 33 does not move under the influence of the external force, and a desired compliance performance can be obtained according to the usage conditions. As described above, it becomes possible to rotate the rotating member 33 in a less sliding state than in the case of adopting a solid seal, which contributes to the improvement of safety and controllability, and the flow from the fluid supply means 12 into the working fluid chamber 30. In addition to controlling the supply of the MR fluid, desired compliance performance can be obtained with a relatively simple device configuration.

When a magnetic field is generated by the magnetic field generating means, the magnetic field always exists in the rotating unit 17. Therefore, for example, hole By providing a magnetic sensor such as an effect sensor, the rotation angle of the rotation unit 17 can be detected without providing a separate angle sensor.

In addition, as the magnetic field generating means, a structure using a permanent magnet can be adopted, and by doing so, improvement in energy efficiency can be expected, and members connected to the drive shaft 32 and the like can be used even in the event of a power failure. can be held in a predetermined posture.

Furthermore, in the above-described embodiment, the case where the actuator main body 11 is a vane-type rotary actuator has been illustrated and explained, but the present invention is not limited to this, and can be applied to a direct-acting hydraulic actuator or the like to generate a driving force. A structure may be employed in which sliding resistance is made variable by providing a gap in the sliding portion, inserting the MR fluid, and adjusting the strength of the magnetic field applied to the MR fluid.

In addition, in the present invention, other magnetic functional fluids such as magnetic fluids (MF) and magnetic mixed fluids (MCF) may be applied instead of MR fluids (MRF) as long as the same effects as those described above are achieved. is also possible.

In addition, the configuration of each part of the device in the present invention is not limited to the illustrated configuration example, and various modifications are possible as long as substantially the same action is exhibited.

REFERENCE SIGNS LIST 10 Actuator system 11 Actuator body 12 Fluid supply means 17 Rotating unit (moving unit)
30 working fluid chamber 30A first chamber space 30B second chamber space 35 gap 37 core member (magnetic field generating means)
38 coil (magnetic field generating means)
39 power supply device (magnetic field generating means)

Claims (4)

An actuator system comprising an actuator body for generating a driving force by the fluid pressure of a working fluid made of a magnetic functional fluid whose viscosity changes according to the strength of a magnetic field, and fluid supply means for supplying the working fluid to the actuator body ,
The actuator main body includes a working fluid chamber connected to the fluid supply means and containing the working fluid, and dividing the working fluid chamber into a plurality of chamber spaces. An operating unit that transmits the driving force to the outside by the pressure difference between the chamber spaces, and a magnetic field generating means that generates a magnetic field,
the operating portion is provided slidably with respect to the working fluid chamber through a gap,
The magnetic field acts on the gap, and the magnetic functional fluid is interposed in the gap. The gap is provided so that the magnetic functional fluid can flow in and out of each of the chamber spaces. functioning the magnetic functional fluid as a fluid seal separate from the working fluid;
The magnetic field generating means is provided so as to be able to adjust the strength of the magnetic field, and changes the viscosity of the magnetic functional fluid in the gap to vary the sliding resistance of the operating portion with respect to the working fluid chamber. An actuator system characterized by: An actuator system comprising an actuator body for generating a driving force by the fluid pressure of a working fluid, and fluid supply means for supplying the working fluid to the actuator body,
The actuator main body includes a working fluid chamber connected to the fluid supply means and containing the working fluid, and dividing the working fluid chamber into a plurality of chamber spaces. An operating unit that transmits the driving force to the outside by the pressure difference between the chamber spaces, and a magnetic field generating means that generates a magnetic field,
the operating portion is provided slidably with respect to the working fluid chamber through a gap,
The magnetic field acts on the gap, and a magnetic functional fluid whose viscosity changes according to the magnetic field strength is interposed in the gap,
The magnetic field generating means is provided so as to be able to adjust the strength of the magnetic field, and changes the viscosity of the magnetic functional fluid in the gap to vary the sliding resistance of the operating portion with respect to the working fluid chamber,
An actuator system according to claim 1, wherein the actuator main body includes a magnetic circuit for applying the magnetic field in the gap in a direction substantially perpendicular to the sliding direction of the moving portion . 2. The actuator system according to claim 1 , wherein said actuator main body includes a magnetic circuit for applying said magnetic field in said gap in a direction substantially perpendicular to the sliding direction of said moving portion. 4. The actuator system according to claim 2 , wherein the magnetic circuit suppresses leakage of the magnetic field from the magnetic field generating means to the room space and concentrates the magnetic field in the gap. .

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