WO2016045658A1

WO2016045658A1 - Working mechanism

Info

Publication number: WO2016045658A1
Application number: PCT/DE2015/100352
Authority: WO
Inventors: Jessica Burgner-Kahrs; Thien-Dang Nguyen
Original assignee: Gottfried Wilhelm Leibniz Universität Hannover
Priority date: 2014-09-26
Filing date: 2015-08-25
Publication date: 2016-03-31
Also published as: DE102014113962B3

Abstract

The invention relates to a continuous or quasi continuous working mechanism (1). In order to overcome the drawbacks of the prior art and provide a working mechanism (1) that is more mobile, has a simpler design and is easier to handle, the working mechanism (1) comprises an uninterrupted backbone consisting of concentrically arranged small tubes (3) which are movable relative to one another, at least one control means (7) is associated with each of the small tubes (3), and a limiting element (4) is disposed at an end portion (6) of each of the small tubes (3).

Description

working mechanism

The invention relates to a continuous or quasi-continuous working mechanism for lifting, fixing, gripping, moving and adjusting objects, which has a continuous backbone of concentrically arranged and mutually movable tubes, wherein each of the tubes associated with at least one adjusting means and at one end portion of each of the tubes a limiting element is arranged.

Such mechanisms, also referred to as manipulators, are suitable for the design of robotic arms, limb prostheses or as controllable moving parts in medical instrumentation.

A generic working mechanism is known for example from US 8, 152,756 B2.

In the following, a discrete kinematic working mechanism is understood to mean a system of rigid bodies which are connected to one another by movable joints, the joints each having only one degree of freedom. An example is

Industrial robot arms with six swivel joints, whose rotation angle is one each

represent independent degree of freedom of the robot arm. Each point within the working space of such a robot arm then has a certain set of six angles of rotation. Here, the working space of a kinematic working mechanism is defined by all the space points that the kinematic working mechanism can reach with one end when its other end is stationary.

In contrast, a continuous or quasi-continuous kinematic working mechanism is understood to mean a spatial sequence of flexible segments, also called actuators. These flexible segments each have a plurality of Degrees of freedom. The configuration spaces of continuous and quasi-continuous kinematic work mechanisms are highly overdetermined, that is, in most points within their work spaces, a variety of degrees of freedom are freely adjustable. Due to this property, a continuous or quasi-continuous kinematic working mechanism is often referred to as "kinematically hyperredundant".

Unlike a quasi-continuous kinematic working mechanism, the segments of a continuous kinematic working mechanism do not contain hinges of rigid materials, but are constructed essentially of plastically and / or elastically deformable materials. Therefore, the segments have a

continuous kinematic working mechanism on countless degrees of freedom.

The prior art and predominantly common are continuous manipulators with segments of fixed length, are guided over the guide discs mechanical adjusting means such as cables, rods or the like, wherein by means of the adjusting means a constant curvature per segment can be produced. The guide discs are distributed at equal intervals to each other firmly connected to a flexible backbone, so that upon actuation of a setting means a uniform segment curvature arises. The angle of curvature is dependent on the shortening or lengthening of the

Variable means, the arc length remains immutable in each segment.

At the same time by the fixed length of the segments and their curvature characteristic is consistent, so that the individual segments of a manipulator depending on the work environment and task previously determined and the manipulator must be designed accordingly.

The introduction of such a working mechanism in a limited work space can be done by advancing the entire working mechanism and simultaneously adjusting the segment curvatures. Despite the preselection of the segment lengths, there are

Fields of application and work spaces where a continuous working mechanism according to the prior art can not reach the desired end position. This is

For example, the case when a collision-free feed of the working mechanism in the end position, especially in the circumvention of obstacles, is not possible.

Long segments have the advantage that a long range can be achieved.

However, due to the uniform curvature tight radii can not be realized. For a feed around tight curves, it is therefore necessary to short segments too choose. However, they lack the range. The order of the bends or segments must also be taken into account in a continuous working mechanism with mechanical actuating means, such as a rope-actuated continuous working mechanism.

As an alternative to mechanical manipulator continuous manipulators, tubular manipulators are known. These consist of concentrically arranged, displaceable and rotatable, precurved, elastic tubes. One of the peculiarities of tubular manipulators is the opposite of rope-actuated manipulators

Curvature order in the activation of the segments. In a tubular

Working mechanism becomes first the last or outer segment

advanced together with all internal segments. For this, the next is then translated and optionally rotated rotatory. Then follows the next segment and so on. The tubes of the individual segments have a pre-curvature. Here, the outer tube has a higher rigidity than the next inner, so that the pre-curvature sets only while the respective tube from the

next out is pushed out. The translation of the tubes allows one

Extension and shortening of the individual segments. Rotation of the tubes into each other allows control over the exit angle. The individual tubes have a pre-curvature, which is selected according to the requirements of the work situation.

Even with tubular working mechanisms, there are unfavorable configurations or

Workrooms. A well-known problem is the so-called snapping of two pre-curved tubes when their angles of curvature are opposite. If this positioning is approached by rotation of the tubes, the frictional force continues to increase until the tubes over-rotate jerkily. To take control of the

Not to lose the final effect position, such configurations, such as

For example, to avoid opposite curves. A pre-selection of the segments and tubes to realize an insertion in a spatially cramped and obstacle-rich work area is highly complex, especially as the radius of curvature in tubular

Manipulators is not adjustable.

In the prior art manipulators are known in which the segment length, the segment curvature and the curvature order can be regulated. In these, each segment has one or more pressure chambers, which are influenced by the supply of a gas or a liquid in its extension. However, such are pneumatic or hydraulic pressure chambers installed only in relatively large manipulators. An example of this is known from the document US 3,284,964 A, which proposes such a working mechanism mounted on a truck. Further examples of fluid-activated manipulators are known from US Pat. No. 4,848,179 A and US Pat. No. 4,551,061 A. Although the document DE 198 33 340 A1, which also discloses a working mechanism equipped with pressure chambers, mentions the use of the working mechanism as a medical instrument. However, it has been found that there are limits to miniaturization of a fluid-activated working mechanism in terms of mechanical implementation and actuation accuracy.

An alternative possibility shows the document DE 10 2010 056 607 A1. This describes the use of electroactive polymers as a substitute for the use of hydraulic or pneumatic media.

The invention has for its object to provide a way to eliminate the disadvantages of the above solutions and a working mechanism

to provide mobility whose mobility is improved and its construction and handling is simplified.

This object is achieved with a device according to the features of claim 1. The further embodiment of the invention can be found in the dependent claims. According to the invention, therefore, a working mechanism has a spatial sequence of flexible segments, wherein each of the segments is bounded by two adjacent limiting elements and comprises a return means, which between two adjacent

Limiting elements is arranged and acts on them. This makes it possible to use as adjusting means pressure and / or limp mechanics, which can be made very light and filigree. The movement of each segment, in particular the curving of a segment, is effected by the at least one adjusting means and by the return means directed counter to this in the force effect.

The at least one adjusting means assigned to the respective tube is firmly connected to its limiting element. It is by means of concentrically arranged and mutually axially movable tube a change in length of the segments and independently of this, a curvature of the segments is possible by means of the adjusting means attached to the limiting elements. Thus, within a segment, for example cable-actuated, a curvature can be achieved with a dynamic change in the length of the segment. As a result, when using a simple construction, the

Agility of the working mechanism improved.

The return means consists for example of at least one resilient body. As a resilient body, a helical spring is preferably used, which is arranged concentrically to the tube. It is also possible to arrange a plurality of elastic bodies in the axial direction behind one another and / or next to one another around the tube. The spring-elastic bodies are preferably each on one

Guide washer mounted. Particularly advantageous is a return means has been found which has a plurality of magnetic guide discs. By using magnetic guide disks within a rope-actuated segment, for example, a constant curvature can be achieved with a dynamic change in the length of the segment. In this case, a high setting or positioning accuracy in conjunction with a strong miniaturization is possible. The change in the length of the segments by means of slidable in the axial direction tube. It is also possible that the return means consists of a combination of at least one resilient body and a plurality of magnetic guide discs.

It is particularly favorable that the guide discs are permanent magnetic. This makes it possible to produce the working mechanism with reduced complexity, which enables a good miniaturization of the working mechanism. Permanent magnetic guide disks are particularly well suited for small-sized continuous manipulators because they lose their magnetic force only at very high temperatures or strong direct mechanical effects. By using juxtaposed segments, which can be impressed by adjusting means over its entire length a continuous curvature, in conjunction with concentrically arranged, mutually displaceable tubes, and the use of permanent magnetic guide discs results in respect to the prior art much improved continuous manipulator. Dynamic adjustment of the segment lengths is possible through the concentric tubes forming the backbone of the manipulator. Segment curvatures can be as needed on the Adjust the adjustment of the adjusting means. The magnetic guide discs ensure a uniform distribution of the guide discs over the length of a segment at each set segment length, so that the set curvature is constant. The concentric, mutually displaceable tubes of the segments are created on the model of tubular manipulators, however, unlike the tubular manipulators have no pre-curvature.

It has proved to be advantageous that the guide discs are toroidal and freely displaceable on the spine in the axial direction. The axial movement of the guide discs is limited by two adjacent boundary elements. The guide discs are arranged concentrically on the tube of their segment. A rotationally symmetrical design of tubes and the passage opening for the spine in the guide discs makes it possible that the guide discs are freely rotatable. Due to the free mobility of the guide discs, a uniform distribution of the guide discs and the forces generated by them within a segment is achieved.

For a uniform distribution of the guide disks, it has proven to be practical that in one segment all guide disks have the same magnetic field strength. As a result, it is achieved in a particularly simple manner that all guide disks of a segment repel each other with equal force or attract each other.

It has proved to be practical that at least one of the adjusting means is a pressure-elastic cable pull and / or a pressure-resistant push rod. According to the invention, other, in particular mechanical, adjusting means, which counteract the force of the magnetic guide disks, are not excluded. The force of the magnetic guide disks acts like a passive rear-part device. Upon actuation of the at least one actuating means, a force is actively applied and directed into the corresponding segment, which at least locally counteracts the magnetic force in the segment. By an axially asymmetric action of the force on a segment this is forced a curvature.

It is also advantageous that each of the guide discs has at least one hole through which the adjusting means of the working mechanism are guided. The adjusting means and the guide discs are movable relative to each other. Likewise, it is advantageous that at least one of the limiting elements has at least one hole through which a Adjusting means is guided at least one other limiting element. Furthermore, it has proven to be practical that the actuating means and / or tubes are not ferromagnetic. It has proved to be particularly favorable that the tubes are made of a super-elastic material, in particular of a nickel-titanium alloy. By means of a superelastic material, which shows a pseudoelastic behavior, in addition to the usual elastic deformation caused by external force reversible change in shape can be achieved, which exceeds the elasticity of conventional metals up to twenty times. This allows a very precise positioning of the working mechanism in the workspace. The material returns to its original form when relieved by its internal tension.

According to one embodiment, it is provided that the magnetic guide disks arranged in a segment are aligned alternately with opposite polarity. As a result of this alignment of the guide disks, in which poles of the same name face one another, it is achieved that the guide disks repel each other. As actuating means in such a segment, a cable is preferably provided. The

Guide elements are aligned so that their identical poles always face each other.

According to an alternative or additional embodiment, it is provided that all arranged in a segment magnetic guide plates are aligned with the same polarity. This ensures that the guide discs attract each other. As a control agent in such a segment, a pressure-resistant rod is preferably provided.

In a preferred embodiment, it is provided that the magnetic

Guiding discs made of carriers mounted on the tube and in the carriers

arranged permanent magnets consist. The carriers are preferably made of a different material from the tube material, which is preferably a plastic.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in Fig. 1 is a schematic sectional view of a working mechanism according to the invention comprising two segments;

Figure 2 is a schematic representation of the working mechanism shown in Figure 1 with guide discs and two segments in compressed functional position.

FIG. 3 shows a schematic illustration of the working mechanism shown in FIG. 1 with guide disks and a segment in expanded functional position; FIG.

4 shows a schematic, enlarged representation of a detail of the segment shown in FIG. 3 in the expanded functional position;

Fig. 5 is a schematic representation of a working mechanism comprising three

Segments in fully expanded functional position;

Fig. 6 is a schematic representation of a first step of using the

Working mechanism on an application example;

Fig. 7 is a schematic representation of a second step of using the

Working mechanism on an application example;

Fig. 8 is a schematic representation of a third step of the use of

Working mechanism on an application example;

9 is a schematic representation of a fourth step of using the

Working mechanism on an application example;

10 is a schematic representation of a fifth step of using the

Working mechanism on an application example;

Fig. 11 is a schematic representation of a sixth step of using the working mechanism on an application example;

Fig. 12 is a schematic representation of a seventh step of using the

Working mechanism on an application example. FIG. 1 shows that the working mechanism 1, which is also referred to as a manipulator, consists of two segments 2, 12 arranged in a spatial sequence and a continuous backbone made of concentric and mutually arranged parts movable tube 3 consists. The tubes 3 are not pre-curved, but highly elastic, preferably superelastic. Furthermore, the

Working mechanism 1 a plurality of limiting elements 4. At a end effector 5 of the working mechanism 1 facing end portion 6 of each of the tubes 3, a limiting element 4 is arranged and fixedly connected to the respective tube 3. A segment 2, 12 is bounded by two adjacent boundary elements 4. Of the

Working mechanism 1 also comprises a plurality of adjusting means 7, wherein each of the tubes 3 is associated with at least one adjusting means 7, each fixed to the

Limiting element 4 is connected and movable relative to the limiting elements 4 of the other tube 3. Figures 2 and 3 show in addition that the

Working mechanism 1 further comprises a plurality of magnetic guide discs 8 as return means 18, wherein between two adjacent limiting elements 4 always more magnetic guide discs 8 are arranged. By acting on the tube 3 of the first segment 2 force 9, the first segment 2 is held in a compressed functional position. The working mechanism 1 is completely compressed. The first or foremost segment 2 is that which is closest to the end effector 5. In FIG. 3, the tube 3 of the first segment 2 is moved in a direction opposite to the force 9. The first segment 2 is now in an expanded functional position. In this case, the guide discs 8 of the first segment 2 are evenly distributed between the limiting elements 4. Since the adjusting means 7 follow the tube 3 with a movement 10 to the same extent, the first segment 2 is not curved. The uniform distribution of the guide discs 8 is achieved by a special orientation of the magnetic guide discs 8. The section of the working mechanism 1 framed by a dashed line 16 is shown enlarged in FIG. This illustrates that the guide discs 8 are aligned alternately with opposite polarity, for example, identical poles are facing each other and the guide discs 8 thus repel each other. In adjacent guide disks 8, the south poles S or the north poles N are alternately facing each other. Since the guide discs 8 repel each other with the same force 1 1, they distribute evenly over the entire segment length, which allows a uniform curvature. FIGS. 5 to 12 show, by means of a working mechanism 1 with three segments 2, 12, 17, an example of application of the working mechanism 1 according to the invention. In FIG. 5, the working mechanism 1 is shown in a fully expanded functional position. The fully expanded functional position is achieved by the movement 10 of the tube 3. To facilitate the understanding of the following description of the application example, the segments 2, 12, 17 are distinguished with respect to their relative position with respect to the end effector 5. The first segment 2 is closest to the end effector 5. As the distance from the end effector 5 increases, only the second segment 12 and then the third segment 17 follow.

Figures 6 to 12 show a working area 13, by which the working mechanism 1 is moved. Initially, the working mechanism 1 is in the fully compressed functional state. The working mechanism 1 is horizontal in the

Work area 13 introduced (Figure 6). Then, the third segment 17 is extended until the end effector 5 almost touches the obstacle 14 (Figure 7). Then, the second segment 12 is expanded and at the same time curved by an actuation of the corresponding actuating means 7, wherein the third segment 17 remains unchanged (Figure 8). Then, the working mechanism 1 is moved further into the working space 13. In this case, the second segment 17 is further expanded and curved until it finally reaches a vertical position (Figure 9). Now, the third segment 17 is further expanded and curved. In the second segment 12, the direction of curvature is changed so that the first segment 2 is moved with the end effector 5 over the obstacle 14 (FIG. 10). Finally, the third segment 17 reaches its final state. The second segment 12 is further extended and curved at the same time to reach the gap 15 between the two obstacles 14 without touching any of the obstacles 14. Then reach the second

Segment 12 its final state (Figure 1 1). Finally, the first segment 2 is elongated and curved until the end effector 5 reaches its target without damaging any obstacles (Figure 12).

Claims

PATE N TAN SP RU CHE

1. Continuous or quasi-continuous working mechanism (1), wherein the

Working mechanism (1) has a continuous backbone of concentrically arranged and mutually movable tube (3), wherein each of the tubes (3) at least one adjusting means (7) is associated and at one end portion (6) of each of the tubes (3) has a limiting element (4), characterized in that the

Working mechanism (1) has a spatial sequence of flexible segments (2, 12, 17), wherein each of the segments (2, 12, 17) by two adjacent

Limiting elements (4) is limited and comprises a return means (18) which is arranged between two adjacent limiting elements (4) and acts on these.

2. Working mechanism (1) according to claim 1, characterized in that the return means (18) at least one resilient body and / or more

magnetic guide discs (8).

3. working mechanism (1) according to claim 2, characterized in that the

Guide discs (8) formed like a torus and on the spine in the axial direction, bounded by two adjacent boundary elements (4), are freely displaceable.

4. working mechanism (1) according to one of claims 2 or 3, characterized

in that the guide discs (8) are made permanently magnetic or are mounted on the tube (3) mounted carriers and on the carriers

Permanent magnets exist.

5. Working mechanism (1) according to at least one of claims 2 to 4, characterized in that in a segment (2, 12, 17) arranged magnetic guide discs (8) are aligned alternately with opposite polarity.

6. Working mechanism (1) according to at least one of the preceding claims, characterized in that at least one of the adjusting means (7) is a pressure-elastic cable and / or a pressure-resistant push rod.

7. Working mechanism (1) according to at least one of the preceding claims, characterized in that the guide discs (8) and / or limiting elements (4) have holes for the adjusting means (7).

8. Working mechanism (1) according to at least one of the preceding claims, characterized in that the tubes (3) are made of a superelastic material, in particular of a nickel-titanium alloy.

9. working mechanism (1) according to at least one of the preceding claims, characterized in that the guide discs (8) has a diameter of less than 12 millimeters, preferably a diameter between 2 and 7 millimeters and / or the segments (2, 12, 17) each have a length between 30 and 100 millimeters in the expanded state and between 5 and 25 millimeters in the compressed state.