JPS63193B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cable-like active body that can be effectively used, for example, for inspection work in a narrow space or for activating a medical endoscope. Active Cord Mechanism
ACM) has an elongated, string-like trunk, and a group of actuators installed in series along the trunk deforms the shape of the trunk axis through active and flexible bending motions to perform various movements. It is defined as a functional body that does This ACM is constructed by sequentially connecting multiple trunk segments in series, and in order to arbitrarily set the trunk posture, each joint mechanism that sequentially connects the trunk segments must be degrees of freedom of movement.
In this case, if the two degrees of freedom in this joint mechanism are both used for the flexed posture, the rotational posture about the axis of the joint cannot be changed arbitrarily. However, when considering this ACM as an arm of a manipulator, its overall posture is important, and the posture around the axis of each trunk segment, that is, the orientation of the trunk surface, is not so important. however,
The attitude around the axis at the end of this ACM is
In the case of a manipulator, it is necessary to determine the posture of the hand, and a degree of freedom regarding the posture around the axis is required at least at the terminal end. Two-degree-of-freedom joints for the basic degree-of-freedom distribution structure of ACM include: (a) A means for making the two axes, the normal and binormal of the axis, the center axis of rotation. (b) Means that uses two axes, the tangent to the axis and the remaining normal or binormal, as the center axis of rotation. There are two possible types. The above means (a) is, for example, known as a universal joint, which is a linear actuator attached to the center and periphery of the joint in the trunk joint, which produces a two-degree-of-freedom bending motion. be. However, this method has a structural problem in that the actuator connection portion also requires a two-degree-of-freedom joint. Since it is difficult to configure a structure in which two different turning movements occur at one point, in reality, as shown in FIG. 1(A), multiple trunk segments L1,
L2, L3, . . . are sequentially connected by a joint mechanism, and it is conceivable that this joint mechanism is alternately composed of a joint Ua of a normal axis and a joint Ub of a binormal axis, and the rotations are separated by one degree of freedom. In this structure, unless the node length between a pair of turning nodes is made sufficiently short, it will not be an ACM basic degrees of freedom distribution structure in the full sense.
In other words, with such means, the concreteness becomes inferior. In addition, although the above means (b) has a structure in which the joints are driven in two degrees of freedom using differential gears, other means such as the one shown in B in FIG. The joints connecting the nodes L1, L2, ... are connected to the coaxial rotation node Uc around the trunk axis and the joint
This can be achieved by constructing a unit joint by combining Ua with the same flexion/swivel joint Ud. Such a structure is relatively simple and can achieve motion equivalent to two degrees of freedom concentrated at one point of the unit joint, and can be driven in accordance with the curvature and torsion of a continuous curve. It has relatively desirable properties. However, in the case of such a structure, especially when bending motion is performed at the joint, the rotational motion by the motor etc. itself becomes a bending action, and the torsional force acts directly on the rotation axis. It becomes a state where For this reason, the results of various prototype experiments show that it is sufficiently robust and can perform spatial movements.
It was not possible to obtain a structure that would provide the necessary functionality as an ACM node. This invention was made in view of the above points, and has a sufficiently simple structure, incorporates various information transmission mechanisms, allows free spatial movement, and has sufficient robustness. The purpose of the present invention is to provide an active cord-like body (ACM) that can be obtained. An embodiment of the present invention will be described below with reference to the drawings. Figure 2 shows this schematic configuration.
A plurality of trunk segments L1, L2,... are arranged and connected in series, and the connecting joints of each trunk segment are connected by coaxial rotation joints.
It is composed of Ja and oblique rotation joint Jb.
These joints Ja and Jb are alternately distributed, and one set constitutes a unit joint J. Figure 3 shows this unit joint J section, which is made up of a coaxial rotation joint Ja _i that rotates coaxially with the trunk axis, and an oblique rotation joint Jb _i that makes an angle α to the trunk axis. This constitutes a unit joint J. In the above oblique rotation joint Jb _i , this joint is α
When rotating around the axis, point P moves on a circular locus as shown by the broken line. At this time, the coaxial rotation joint
When Ja _i is rotated, point P will move on a spherical shell with a maximum angle of 4α centered on point O. That is,
Due to the two-degree-of-freedom rotation of the oblique rotation joint Jb _i and the coaxial rotation joint Ja _i , the trunk joint L _i moves ±2α around point O.
It becomes possible to perform movable movements within the solid angle range of . Generally, when considering flexible bending motion by ACM, since ACM is originally composed of a large number of unit groups, the range of bending motion per joint may be considerably limited. For example, in the case of the snake, which moves extremely flexibly, the entire trunk consists of about 200 dorsal vertebrae, so the anatomical range of movement per unit segment is only about ±4 degrees. Considering this point, it is believed that sufficiently flexible movement is possible even when an oblique rotation mechanism is used as the joint mechanism of the ACM. Then, ACM using such oblique rotation joint
By configuring the cylindrical shape, the geometrical arrangement eliminates unnecessary irregularities in the outer shape, and it becomes possible to change the posture by bending the cylindrical shape as it is. In other words, it becomes easier to effectively demonstrate the functionality unique to ACM, such as the ability to penetrate into narrow spaces. In addition, since it can be a kind of exoskeleton structure composed of a cylindrical body, it is possible to transmit angle commands to the actuator, power lines, etc. through the internal space, and the proportion of the cross-sectional dimension is The mechanism can be structurally lightweight and robust, and the spatial mobility of the ACM can be easily improved. Now, when considering the control of the oblique rotation mechanism, first, what is the relationship between the rotation angle θ _i of the oblique rotation joint and the rotation angle φ _i of the coaxial rotation joint with the bending angle ρ _i and the torsion angle τ _i ? Consider whether there is. Here, the bending angle ρ _i is the trunk node
It is an angle formed by L _i-1 and L _i , and is an angle around the trunk node L _i-1 in a direction having an inflection angle with respect to the curvature of the continuous curve, and corresponds to the torsion of the continuous curve. The torsion angle τ _i is the angle around the trunk node L _i-1 in the direction in which the trunk node L _i has an inclination angle with respect to l _i-1 , and corresponds to the torsion coefficient of the continuous curve. shall be. First, as a preparation for inducing such a relationship, a degree-of-freedom system consisting of an oblique rotation joint and coaxial rotation joints before and after the oblique rotation joint as shown in FIG. 4 will be considered. In Figure 4, the trunk (link) vector
Assuming that L _i-1 and L _i are linear in the initial state, the tangential vector t is taken in the direction of this trunk axis, and the normal vector n is perpendicular to t, and the oblique rotation center axis α is taken from t to n
The binormal vector b is taken to be included in the plane, and the binormal vector b is t
~ taken in the direction perpendicular to the n plane. The rotation of a space vector is expressed using Makino's method, in which the rotation of the vector x around the anti-time axis at an angle θ about the vector y is expressed as E ^y 〓(x) using a rotation transformation tensor. For example, the rotational transformation tensor E _i of this 3-degree-of-freedom link system is expressed as E _i =E ^t 〓 _i ′E ^b 〓E ^t 〓 _i E ^b(- 〓 ⁾ E ^t 〓 _i ″...(1) .However, here It shows. Equation (1) first corrects the rotation of L _i by φ _i ″, then aligns the center axis of oblique rotation α with t and rotates it by θ, then returns α to the original value, and changes L _i-1 to φ ₁ ′. In a three-degree-of-freedom system as shown in Figure 4, when the oblique rotation joint is rotated, by cooperatively rotating other coaxial rotation joints, In order to produce simple refraction without twisting as a whole, the following conditions are necessary: (a) The refraction motion of L _i occurs only in the t~b plane. (b) n erected on the vector L _i The direction vector does not change its direction even after transformation. The condition (a) above is that the normal vector component of E _i (t) is "0", and from the transformation tensor in equation (1), this is shown as follows. sinα{cosα(1−cosθ)cosφ ₁ ′
+sinθsinφ ₁ ′}=0 ...(2) Since sin≠0, this condition becomes as follows. cosα(1−cosθ)cosφ ₁ ′
+sinθsinφ ₁ ′=0 (3) On the other hand, the condition (b) is that E _(o) = n holds true. When this relationship is derived from the transformation tensor of equation (1), an isomorphic relationship is derived, especially for the tangential component, by replacing φ ₁ ′ with φ ₁ ″ in equation (2). From this, It can be said that φ _i ″=φ _i ′≡φ _i . In other words, in order to achieve a bending motion without twisting (τ _i = 0), when an oblique rotation joint turns at an angle θ _i , both coaxial rotation joints before and after it must correct the same angle φ _i in the same direction. All you have to do is rotate. This φ _i is obtained from equation (3) as follows. φ _i = tan ^-1 (−cosα(1−cosθ _i )/sinθ _i )……(
4) Furthermore, the inflection angle ρ _i that occurs at this time is determined by the ratio of the tangential component and the binormal component of E _i (t) as follows. ρ _i =−sgn(θ _i )cos ⁻¹ {cosθ _i +cos ² α(1−cosθ _i )} …(5) However,

[Formula] Conversely, the rotation angle θ _i of the oblique rotation joint is expressed by the bending angle ρ _i as follows. θ _i =−sgn(ρ _i )cos ⁻¹ (cosρ _i −cos ² α/1−cos ² α) ……(6) From the above, in order to produce refraction without twisting at the oblique rotation joint, It can be understood that equal angle correction circuits in the same direction are required for the coaxial rotary joints before and after the joint. From this, it can be seen that, conversely, the coaxial rotary joint in the oblique rotation mechanism performs three functions at the same time. In other words, the rotation angle φ _i of the coaxial rotation joint Jθ _i is the corrected rotation angle φ _i of the oblique rotation joints before and after it,
To yield φ _i-1 and the torsion angle τ _i given to its joint,
It is given by the following formula. φ _i = φ _i + φ _i-1 + τ _i ...(7) Figure 5 shows a specific configuration example of a coaxial rotation joint, and a pair of trunk segments connected by this joint are: Cylindrical hollow pipes 11a and 11b, respectively
Fixed disks 12a and 12b are fitted and fixed to the opposing end surfaces, respectively. A through hole is formed in each of the central shafts of the fixed disks 12a and 12b, and the fixed disks 12a and 12b are connected by a hollow shaft 13 and tightened with a nut 14. Here, a bearing 16 whose position is set by a bearing presser 15 is interposed between the fixed disks 12a and 12b, and the fixed disks 12a and 12b are set so that they can rotate freely relative to each other. Further, a ring gear 17 having teeth on the inner peripheral surface is fixedly attached to the fixed disc 12b. Further, a pulse motor 18 whose rotation is controlled by an encoder output is provided inside the hollow pipe 11a, and the rotation of this pulse motor 18 is transmitted to a rotating shaft 18 located outside the pipe 11a through a reduction gear mechanism.
Take it out at 9. The rotating shaft 19 is led out through the through hole 20 of the fixed disc 12a, rotates a gear 21 that meshes with the ring gear 17, and the pulse motor 18 causes the hollow pipes 11a and 11b to be aligned with each other. It becomes like being rotated. FIG. 6 shows a specific configuration example of an oblique rotation joint constructed between hollow pipes 11b and 11c. The fixed elliptical plates 22a and 22b are fitted and fixed in correspondence with the oblique end faces. That is, the fixed elliptical plates 22a, 22b are the same as the fixed disks 11a, 11 in FIG.
This fixed elliptical plate 22 is a member corresponding to b.
In relation to a and 22b, a hollow shaft 13, a nut 14, and a bearing retainer 1 similar to those shown in FIG.
5. A bearing 16 is combined, and the ring gear 17 is rotated by a pulse motor 18, so that the hollow pipe 11c is rotated. However, in this case, the axis α of the rotation mechanism that performs the above-mentioned turning movement is set to be inclined at an angle α with respect to the axes of the hollow pipes 11b and 11c. Here, if the rotation axis inclination α of this oblique rotation joint is, for example, 25 degrees, a certain degree of bending movement range of ±50 degrees is generated in each joint. Further, the elliptical shape of the opposing end surfaces of the hollow pipes 11b and 11c is α
= 25 degrees, the difference in length between the major axis and minor axis is about 10%. By connecting multiple sets of unit joints configured in this way, an ACM mechanism that can be freely deformed as shown in Figure 7 is completed, and the pulse motor in each joint can be digitally connected. As a servo system, its rotation angle and rotational angular velocity are directly driven and controlled by a microcomputer. This kind of ACM overall trunk consists of two parts on the floor.
In addition to being capable of dimensional movement, it is also possible to take a three-dimensional posture that maintains the balance as commanded, and then change that posture. In addition, this ACM mechanism can use the difference in the coefficient of friction between the floor surface in the axial direction and the normal direction to perform a propulsion motion by a "snake"-like scouring motion. It is possible. However, as shown in FIG. 8, if the wheel mechanism 25 is provided with a large number of legs along the trunk, and each wheel mechanism 25 is provided with a rotation control drive mechanism, it will be more effective. Propulsion movement can be achieved. In this case, this wheel mechanism 25 includes a ring 26 rotatably attached to the outer periphery of the trunk, as shown in FIG.
If the structure is such that the wheels 27 are attached to the body, it is possible to set the body in contact with the floor regardless of the rotation of the trunk, and it is also possible to penetrate into narrow passages, wrap around columnar bodies, and propel the body. It is possible. As described above, according to the present invention, it is possible to obtain a cable-like active body that exhibits excellent functions such as spatial mobility. It can be expected to be effective in making medical endoscopes more active and in applications such as self-propelled inspection robots in environments with poor accessibility, such as inside nuclear reactors.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a conventionally considered ACM, FIG. 2 is a schematic diagram illustrating an ACM according to an embodiment of the present invention, FIG. 3 is a diagram illustrating unit joints of the above ACM, and FIG. The figure also explains the controllability, Figures 5 and 6 are exploded perspective views showing the configuration of the coaxial and oblique rotation joints, Figure 7 is the overall view of the ACM, and A in Figure 8 is the above A diagram explaining the self-propelled mechanism of ACM, B in the diagram is b-b in diagram A
It is a line enlarged sectional view. L1, L2,... Trunk joint, Ja... Coaxial rotation joint, Jb... Oblique rotation joint, 11a, 11b... Hollow pipe, 12a, 12b... Fixed disc, 13...
...Hollow shaft, 16...Bearing, 17...
Ring gear, 18...Pulse motor, 22a, 2
2b...Fixed disc.

Claims (1)

[Claims] 1. A plurality of trunk joints are arranged in sequence, and each joint is arranged sequentially and alternately. A first connecting mechanism that can freely control rotation coaxially with the trunk axis, and a first connecting mechanism that is tilted to the trunk axis. The rope-like structure is connected by a second connecting mechanism that can freely control the rotation in the state, and the first and second connecting mechanisms control the rotation angle to be coaxial or obliquely rotating, respectively. active body.