CN107097218B - Wire traction variable-rigidity mechanism based on mechanical locking - Google Patents

Abstract

The invention discloses a wire traction variable stiffness mechanism based on mechanical locking, which includes a basic structure of a continuous robot, a variable stiffness locking mechanism and a variable stiffness traction mechanism; Composed of four driving wires, the connecting disc is divided into a middle connecting disc and an end connecting disc, the end connecting disc is fixed with the central wire and the end of the driving wire through a wedge-shaped lock mouth, and the middle connecting disc is fixed with the central wire through a wedge-shaped lock mouth; variable stiffness lock The tightening mechanism is a single-degree-of-freedom mechanism composed of sliding helical gears, springs, incomplete gears, connecting rods, and inlaid metal sheets with each intermediate connecting plate as the frame; the variable-stiffness traction mechanism consists of a guide wire sheath, a tensile metal The outer sheath of the guide wire is concentric with the central wire, and the tensile metal wire passes through the wedge-shaped lock mouth of the outer sheath of the guide wire and the central wire, and is fixed by the locking grain of the wire and the sliding helical gear. The rigid-flexible state of the mechanism can be converted quickly, and the positioning rigidity is higher.

Description

A wire traction variable stiffness mechanism based on mechanical locking

technical field

The invention relates to the field of variable stiffness design of continuous mechanisms, in particular to a wire traction variable stiffness mechanism based on mechanical locking.

Background technique

Continuous mechanisms that imitate biological organs such as snakes and elephant trunks have high movement flexibility and strong adaptability in complex environments, especially in unstructured environments with many obstacles and narrow spaces. Change its shape flexibly. However, due to the high flexibility of the continuous mechanism, it also has the disadvantages of poor positioning rigidity and low control precision. In applications in medical and other fields, continuous mechanisms are often required to exhibit good flexibility and certain rigidity under certain conditions. For example, when a continuous mechanism is used for an endoscopic robot, its working process is divided into two stages. In the first stage, the robot needs to conform to the structure of the human cavity in a flexible state, and send the surgical tool to the target position; in the second stage, when the surgical tool is in the When operating in the human body, this requires the robot to have sufficient stiffness to provide mechanical support for the end-surgical tools. Therefore, the research on the variable stiffness of continuous mechanism has great significance.

In recent years, people have invented a variety of variable stiffness continuous mechanisms by using negative pressure blocking mechanisms, low melting point alloy phase transformation, positive pressure locking, etc., but most of them show defects such as insufficient variable stiffness and insufficient response speed.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a wire traction variable stiffness mechanism based on mechanical locking. The mechanism adopts the mechanism friction locking technology, and the relative movement inside the robot joint is limited by the friction of the labor-saving locking device. Thereby changing the structural stiffness. For the continuous robot driven by nickel-titanium alloy wire, the variable stiffness scheme is to directly lock the driving wire through the existing connecting plate, so the design is compact. In addition, the mechanical variable stiffness design has fast response, rapid transition between rigid and flexible states, and higher positioning rigidity.

The purpose of the present invention is achieved by the following technical solutions:

A wire traction variable stiffness mechanism based on mechanical locking, including the basic structure of a continuous robot, a variable stiffness locking mechanism and a variable stiffness traction mechanism; The driving wire is composed of a wire passing hole corresponding to the driving wire on the connecting plate. The connecting plate is divided into a middle connecting plate and an end connecting plate. The end connecting plate is connected with the central wire and the driving wire through a wedge-shaped lock mouth. The end is fixed, and the middle connection plate is fixed with the central wire through a wedge lock mouth, and the wedge lock mouth is composed of a slotted wedge screw and a nut;

The variable stiffness locking mechanism is a single-degree-of-freedom mechanism composed of sliding helical gears, springs, incomplete gears, connecting rods and inlaid metal sheets, with each intermediate connecting plate as a frame. A helical gear that slides longitudinally on the middle connecting plate, one end of the incomplete gear is distributed with incomplete helical teeth meshing with the sliding helical gear, the other end is distributed with a connecting shaft that cooperates with the connecting rod, and the middle is distributed with a Cooperating shaft holes and locking thread holes, and connecting holes for fixing the inlaid metal sheet, the two ends of the connecting rod are provided with connecting holes matching the incomplete gear;

The traction mechanism with variable stiffness is composed of a guide wire sheath, a tensile metal wire, and a wire locking grain. The guide wire sheath is concentric with the central wire, and the tensile metal wire passes through the guide wire sheath and the central wire. The wedge-shaped lock mouth is fixed with the sliding helical gear through the metal wire lock grain.

The connecting plate is also provided with a tapered hole matching with the wedge-shaped lock mouth.

Helical teeth with a modulus less than 1mm are distributed around the sliding helical gear.

Both the central wire and the driving wire are made of alloy wires that are bendable and do not produce axial deformation.

The variable stiffness locking mechanism is a radially symmetrical single-degree-of-freedom mechanism, and is driven by a sliding helical gear.

The variable stiffness locking mechanism is provided with a link mechanism for balancing the locking force of each wire, and the link structure includes a link and an incomplete gear.

The variable stiffness traction mechanism can synchronously pull the variable stiffness locking mechanisms on all connecting plates.

In the structure described above, the sliding helical gear in the variable stiffness locking mechanism on each connecting plate moves along the axial direction of the connecting plate under the traction of the same tensile wire. According to the characteristics of the helical gear , its axial movement can be equivalent to the rotation around the central axis, and produces meshing motion with the incomplete gear. One side of the incomplete gear is used as a meshing gear, and at the same time as a locking labor-saving lever, which is used to limit the free sliding of the driving wire and fix it with the connecting disc by friction. The metal sheet is embedded on the incomplete gear and the connecting plate, and the metal sheet becomes a part that directly contacts the driving wire during the locking process, which can improve the locking friction. According to such a locking principle, the relative sliding between the connection plate and the driving wire can be eliminated, so that the connection plates of the continuous robot are fixed and supported by multiple metal wires, thereby improving the local rigidity, thereby improving the overall rigidity of the robot.

Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are:

1. The wire traction variable stiffness mechanism based on mechanical locking is designed for the basic structure of the continuous robot driven by alloy wire. It only needs to add a variable stiffness locking mechanism on each connecting plate to control the friction between the driving wire and the connecting plate The relationship is sufficient, and its advantage is that the design is simple and the structure is compact.

2. The variable stiffness locking mechanism in each connection plate has only one degree of freedom, and the variable stiffness locking mechanism on each connection plate can be connected in series through a tensile metal wire, so that a single traction can be achieved to complete the overall variable stiffness. The purpose of rigidity, and the sliding meshing principle of helical gears and the principle of leverage are adopted in the variable stiffness locking mechanism, which has a great labor-saving effect. Therefore, the variable stiffness scheme is simple to drive and easy to control.

3. The variable stiffness locking mechanism combines four parallelogram mechanisms connected end to end to form a ring-shaped linkage mechanism, which connects the four incomplete gears in coordination to coordinate and balance the locking force of each wire. Make each part of the continuous robot have uniform stiffness.

4. In addition to the simple structure, the variable stiffness scheme also performs stiffness control and motion control completely independently, realizing the decoupling of stiffness and motion. The mechanical design scheme makes its variable stiffness operation respond quickly, stable and reliable.

Description of drawings

Figures 1-1 and 1-2 are schematic diagrams of the overall structure of the present invention.

Fig. 2 is a structural schematic diagram of the central wire wedge lock mouth.

Figures 3-1, 3-2, and 3-3 are structural schematic diagrams of variable stiffness locking mechanisms.

Figure 4 is a schematic diagram of the meshing of the sliding helical gear and the incomplete meshing gear.

Fig. 5 is a structural schematic diagram of the traction mechanism with variable stiffness.

Reference signs: 1-end connecting disc 2-driving wire 3-intermediate connecting disc 4-incomplete gear 5-connecting rod 6-guide wire sheath 7 tensile wire 8-wire locking grain 9-sliding helical gear 10 -Central wire 11-Drive wire wedge lock mouth 12-Central wire wedge lock mouth 13-Wedge lock mouth nut 14-Spring 15-Fixed mosaic metal piece 16-Movement mosaic metal piece 17-Thread hole 18-Lever lock shaft 19 - gap

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1-1 and Figure 1-2, a wire traction variable stiffness mechanism based on mechanical locking includes the basic structure of a continuous robot, a variable stiffness locking mechanism and a variable stiffness traction mechanism. The basic structure of the continuous robot consists of a central wire 10 that connects all the connection plates in the joint in series, and the bending motion of the joint can be realized under the combined drive of the surrounding driving wire 2; Under the traction effect of 7, the driving wire 2 distributed around can be clamped, so that it is fixed relative to each connection plate, thereby changing the structural stiffness of the continuous robot, and playing a role in regulating the overall structural stiffness; the variable stiffness traction mechanism is used for conduction resistance The tension of the wire is drawn, and the tension distribution of the wire acts on the variable stiffness locking mechanism on each connecting plate. Both the driving wire 2 and the central wire 10 in this embodiment are nickel-titanium alloy wires. The nickel-titanium alloy wires do not produce axial deformation but can be bent. Other alloy wires with this property are applicable to the present invention.

In this embodiment, in the basic structure of the continuous robot, a central wire 10 is fixed and connected in series with a plurality of intermediate connecting discs 3 and an end connecting disc 1 by means of a central wire wedge lock mouth 12 to form a joint of the continuous robot. The four driving wires 2 distributed around are fixed on the end connecting plate 1 by means of the driving wire wedge lock mouth 11, and pass through the wire passing holes 17 on all the intermediate connecting plates 3 to be connected with the power driving parts. This embodiment takes the central wire wedge lock mouth 12 as an example to describe its working principle, as shown in Figure 2 is the working principle diagram of the central wire wedge lock mouth 12. The tapered holes on the connection plate 3 are matched, and the large end of the central wire wedge lock mouth 12 is designed with a vertically intersecting slot. The grooved part of the mouth 12 is deformed under the constraint of the taper hole of the middle connecting plate 3, and the deformed central wire wedge-shaped locking mouth 12 will surround the central wire 10, and under the action of a large encircling force, the central wire 10 and the central wire will The wire wedge-shaped lock mouth 12 has a good friction effect, so it can play the role of firmly connecting the central wire 10 to the middle connection plate 3. Similarly, the fixing principle of the driving wire 2 and the end connection plate 1 is also the same. An important advantage of the fixing method is that it can be disassembled at will. In a single flexible joint, because the surrounding four driving wires 2 are constrained by all the intermediate connection discs 3 fixed by the central wire 10, and have good elasticity, when pushing and pulling each driving wire 2 in combination, the entire flexible joint will Constrained to bend toward the specified direction, it becomes the basic motion of the continuous robot driven by nickel-titanium alloy wire.

Before the joints of the continuous robot bend and move to the specified pose for operation, it is necessary to change the stiffness of each joint of the robot to resist the external force. Lock the surrounding driving wire 2 so that it is fixedly connected to the middle connecting disk 3, so that the support between the two middle connecting disks is changed from one central wire to five nickel-titanium alloy wires, so the flexible joint can obtain the best rigidity performance. promote.

As shown in Figures 3-1, 3-2 and 3-3, the variable stiffness locking mechanism is composed of sliding helical gear 9, incomplete gear 4, connecting rod 5, fixed inlaid metal sheet 15 and movable inlaid metal sheet 16, etc. . The sliding helical gear 9 is an active part driven by a variable stiffness traction mechanism, and its outer circumference is distributed with small modulus helical teeth. The sliding helical gear 9 can move axially along the chute on the middle connecting plate 3, and the sliding helical gear axially The movement can produce equivalent rotation in the radial direction, as shown in Figure 4, when the sliding helical gear 9 moves down the X distance, and the angle of one tooth is equivalently rotated in the circumferential direction, the sliding helical gear 9 and the incomplete gear 4 It is a complete meshing helical gear mechanism. The relative rotation generated by the movement of the sliding helical gear 9 finally drives the incomplete gear 4 to rotate around the shaft 18 of the locking lever. During the rotation, the movable inlaid metal sheet fixed with the incomplete gear 4 16 and the fixed inlaid metal sheet 15 produce a narrow gap 19, through the clamping force friction of two inlaid metal sheets and the driving wire 2, the relative fixing of the driving wire 2 and the intermediate connection plate 3 can be ensured. In the variable stiffness locking mechanism, the driving force applied by the sliding helical gear 9 to the incomplete gear 4 and the pressure exerted by the drive wire 2 on the movable mosaic metal sheet 16 are a pair of balanced forces. The distance of the screw lever rotating shaft 18 is much smaller than the distance from the gear meshing index circle circumference to the screw locking lever rotating shaft 18, so this mechanism is a labor-saving mechanism, and its effect is exactly to obtain larger locking force under small driving force. The sliding helical gear 9 slides under the traction of the tensile metal wire 7. After the sliding helical gear 9 slides and locks the driving wire 2 downwards, if you want to unlock the locking and reduce the overall rigidity, you only need to loosen the drive of the sliding helical gear 9. The tensile metal wire 7 slides the helical gear 9 to move upwards to release the lock under the action of the restoring force of the spring 14 . In addition, in order to balance the locking force of each incomplete gear, an annular parallelogram linkage mechanism is combined in the variable stiffness locking mechanism. The linkage mechanism includes a connecting rod 5 and an incomplete gear 4; two incomplete gears 4 are connected as A group of opposite sides of a parallelogram mechanism, so that the four incomplete gears 4 can be linked to obtain a balanced locking force.

The variable stiffness traction mechanism is a device that transmits and distributes the traction force on the base to each connection plate. As shown in Figure 1-1 and Figure 1-2, the variable stiffness traction mechanism is composed of Tensile metal wire 7, guide wire outer sheath 6, and wire lock grain 8 are composed, as shown in Figure 1-1 and Figure 5, the tensile metal wire 7 passes through the guide wire outer sheath 6 on the central wire 10 and then passes through Through the fine holes on the central wire wedge-shaped lock mouth 12 and the sliding helical gear 9, the upper edge of each sliding helical gear 9 is fixed with a metal wire lock particle 8, and when the tensile metal wire 7 is pulled, each can be pulled synchronously. Sliding helical gear 9 on a connecting plate. In order to make the traction force distribution to the sliding helical gear 9 uniform, four tensile metal wires 7 are used at the same time, and these four tensile metal wires move under the same traction force.

The working process of the present invention is as follows: in the compliant state, the length change of the driving wire 2 is controlled by the power driving part, so that the joint of the continuous robot reaches a specified pose. Under the condition of keeping its shape unchanged, under the traction of the tensile metal wire 7, the sliding helical gear 9 on each connection plate moves axially relative to each intermediate connection plate 3, and then drives the gears in each variable stiffness locking mechanism. The incomplete gear 4 makes the driving wire 2 locked relative to the middle connection plate 3, so that the whole is converted into a rigid state; after that, the traction force of the tensile metal wire 7 is released, and the spring 14 in each variable stiffness locking mechanism slides obliquely. Gear 9 reverts to move, unlocks, and recovers the flexibility of the whole. During the locking process, the tensile metal wire 7 has to overcome the elastic force of the springs 14 in each variable stiffness locking mechanism.

In this embodiment, the central wire 10 and the driving wire 2 in the overall structure are super-elastic nickel-titanium alloy wires, and the tensile wire 7, the wire locking grain 8, the guide wire outer sheath 6 and the locking wire lever shaft 18 are all procurement standards. The fixed inlaid metal sheet 15 and the movable inlaid metal sheet 16 are all aluminum alloy metal sheets processed by laser cutting, and other parts are all 3D printed parts made of photosensitive resin. Each part of the mechanism and the traction mechanism with variable stiffness includes each other and is assembled into one body.

The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention, and the above specific embodiments are only illustrative and not restrictive. Without departing from the gist of the present invention and the scope of protection of the claims, those skilled in the art can also make many specific changes under the inspiration of the present invention, and these all belong to the protection scope of the present invention.

Claims (8)

1. A wire traction variable stiffness mechanism based on mechanical locking is characterized by comprising a continuous robot basic structure, a variable stiffness locking mechanism and a variable stiffness traction mechanism; the basic structure of the continuous robot comprises a connecting disc, a central wire and four driving wires which are distributed circumferentially, wherein the connecting disc is provided with a wire passing hole corresponding to the driving wires, the connecting disc is divided into a middle connecting disc and a tail end connecting disc, the tail end connecting disc is fixed with the central wire and the tail ends of the driving wires through a wedge-shaped locking nozzle, the middle connecting disc is fixed with the central wire through the wedge-shaped locking nozzle, and the wedge-shaped locking nozzle is formed by a slotted wedge-shaped screw and a slotted nut;

the variable-rigidity locking mechanism is a single-degree-of-freedom mechanism which takes each middle connecting disc as a frame and consists of a sliding helical gear, a spring, an incomplete gear, a connecting rod and an embedded metal sheet, wherein the sliding helical gear is a helical gear capable of longitudinally sliding on the middle connecting disc, one end of the incomplete gear is provided with incomplete helical teeth meshed with the sliding helical gear, the other end of the incomplete gear is provided with a connecting shaft matched with the connecting rod, the middle of the incomplete gear is provided with a shaft hole and a wire locking hole matched with the connecting discs and a connecting hole used for fixing the embedded metal sheet, and two ends of the connecting rod are provided with connecting holes matched with the incomplete gear;

the variable-rigidity traction mechanism is composed of a guide wire outer sheath, a tensile metal wire and a metal wire locking particle, wherein the guide wire outer sheath is concentric with the central wire, and the tensile metal wire penetrates through the guide wire outer sheath and a wedge-shaped locking nozzle of the central wire and is fixed with the sliding helical gear through the metal wire locking particle.

2. The mechanical locking based wire traction variable stiffness mechanism is characterized in that a taper hole matched with the wedge-shaped lock nozzle is further formed in the connecting disc.

3. The mechanical locking based wire traction variable stiffness mechanism according to claim 1, wherein helical teeth with modulus less than 1mm are distributed around the sliding helical gear.

4. The mechanical locking-based wire pulling stiffness varying mechanism according to claim 1, wherein the central wire and the driving wire are made of an alloy wire that can bend without axial deformation.

5. The mechanical locking-based wire traction variable stiffness mechanism is characterized in that the variable stiffness locking mechanism is a radiation symmetric single-degree-of-freedom mechanism and is driven by a sliding bevel gear.

6. The mechanical locking based wire pulling stiffness varying mechanism according to claim 1 or 5, wherein the stiffness varying locking mechanism is provided with a link mechanism for equalizing locking force of each wire, the link mechanism comprising a link and a partial gear.

7. The mechanical locking based wire pulling variable stiffness mechanism of claim 1, wherein the variable stiffness pulling mechanism can pull the variable stiffness locking mechanism on all the connecting discs synchronously.

8. The mechanical lock-based wire pulling stiffness varying mechanism of claim 1, wherein the insert metal pieces comprise a fixed insert metal piece and a movable insert metal piece.

Images