KR101668386B1 - under-actuated robot finger device and method for controlling the same - Google Patents

Abstract

An insufficiently driven robot finger device according to an embodiment of the present invention includes a robot finger adapted to be in direct contact with an object; And a robot finger control unit configured to control the robot finger, wherein the robot finger includes a plurality of phalanxes, the plurality of phalanxes includes a first phalanx rotatably connected to the base at a first joint joint, A second phalanx rotatably connected to the first phalanx at a third joint joint and a third phalanx rotatably connected to the second phalanx at a third joint joint, wherein the robot finger control unit controls the contact force .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an insufficient drive robot finger device and a control method thereof,

Field of the Invention [0002] The present invention relates to a robot finger, and more particularly, to an insufficiently driven robot finger device that does not require a complicated sensor and control system by arithmetically calculating the contact force at each contact point.

Robot finger devices that handle objects have been developed in various forms and have been used in various fields. In the case of isotropic grippers that provide uniform contact force, generally ten or more actuators and sensors are required to provide a device capable of gripping operations similar to human fingers. Utah / MIT Hand has been developed with this type of robot hand.

On the other hand, in the case of an insufficiently driven robot finger using an actuator smaller than the degree of freedom of the robot finger, the number of actuators can be reduced compared with the case where an actuator is provided for each joint, thereby providing various advantages. In the case of such an insufficiently powered robotic finger device, it is important to design the device so that it can adapt itself to the shape of the object it is handling, using springs or kinematic constraints.

However, in the case of the conventional insufficient drive type robot finger, there is no suggestion of a method of effectively controlling the robot finger by efficiently calculating the contact force at the contact point in each phalange.

(Prior art)

Patent Registration No. 10-1340294

As described above, the present invention provides a robot finger device capable of efficiently calculating a contact force at a contact point in each phalanx of an insufficiently driven robot finger and controlling the robot finger device based on the contact force.

According to an aspect of the present invention, there is provided an insufficiently driven robot finger device comprising: a robot finger adapted to be in direct contact with an object; And a robot finger control unit adapted to control the robot finger, wherein the robot finger includes a plurality of phalanxes,

Wherein the plurality of phalanxes comprises a first phalanx rotatably connected to the base at a first joint joint, a second phalanx rotatably connected to the first phalanx at a second joint joint, and a second phalanx rotatably connected to the second phalanx at a third joint joint. A third phalanx connected to the second phalanx,

The robot finger control unit calculates the contact force with the object from each of the plurality of phalanxes.

At this time, the robot finger device may further include an actuator for rotating the first phalanx against the base at the first joint joint,

A first kinetic transmission element for transmitting part of the rotational operating force applied to the first phalanx by the actuator to the second phalanx to rotate the second phalanx against the first phalanx at the second joint joint; A second motion transmitting element for transmitting a part of the rotational operating force applied to the second phalanx by the first motion transmitting element to the third phalanx to rotate the third phalanx against the second phalanx at the third joint joint, As shown in FIG.

The first kinetic transmission element includes a first passive element that mechanically restrains a position of the second phalanx against the first phalanx, and a second passive element that mechanically restrains the position of the second phalanx against the first phalanx, And a first spring for applying a first spring torque,

The second kinetic transmission element includes a second passive element that mechanically restrains the position of the third phalanx against the second phalanx and a second passive element that mechanically restrains the position of the third phalanx against the second phalanx, And a second spring for applying a torque.

Furthermore, the first passive element has a first main drive bar, one end of which is rotatably connected to the first joint joint, a first insufficient drive bar rotatably connected to the first main drive bar and having one end connected to the first main drive joint, And a first four-bar linkage structure including a first sub-drive bar rotatably connected to the first insufficient drive bar and having one end connected to the first sub-drive joint and the other end rotatably connected to the second joint joint, ,

The second passive element has a second main drive bar, one end of which is rotatably connected to the second joint joint, a second insufficient drive bar rotatably connected to the second main drive joint at one end thereof to the second main drive joint, And a second sub-drive bar rotatably connected to the second insufficient drive bar, the second sub-drive bar having one end connected to the second sub-drive joint and the other end rotatably connected to the third joint joint.

In addition, the robot finger control unit may control the robot finger control unit such that, in each of the plurality of phalanxes, a kinematic value of the robot finger, a kinematic value of the first passive element, a kinematic value of the second passive element, The contact force can be calculated using the characteristics of the spring and the characteristics of the second spring.

The kinematic value of the robot finger may be determined by a length of each of the plurality of phalanxes, a distance from the first joint joint to a contact point at which the first phalanx of the object contacts the object, May include the distance to the point of contact with the object.

In addition, the kinematic value of the first passive element may include the length of the first main drive bar, the length of the first insufficient drive bar, and the length of the first sub-drive bar.

In addition, the kinematic value of the second passive element may include the length of the second main drive bar, the length of the second insufficient drive bar, and the length of the second sub-drive bar.

Wherein the robot finger controller comprises:

May be configured to calculate the contact force,

From here

k _i is the distance from the i-th joint to the contact point at which the i-th phalanx contacts the object; F _i is the contact force at the contact point at which the i-th phalanx contacts the object;

이며;

;

Where L _k is the length of the k th phalanx,

θ _m is the rotation angle of the m-th phalanx for the base or m-1 th phalanx.

를 제거한 후 상기 접촉력을 산출하는 것일 수 있다.
Further, when the i-th phalanx does not contact the object, the robot finger control unit removes the i-th row and the i-th row of the matrix from the left side of the relational expression, removes F _i ,

And then the contact force is calculated.

The robot finger control unit may be configured to calculate the contact force using the kinematic value of the robot finger, the kinematic value of the first motion transmission element, and the kinematic value of the second motion transmission element in each of the plurality of phalanxes there is,

At this time,

To calculate the contact force,

From here,

J _T is an n by n matrix determined by the kinematic value of the robot finger, n is the number of phalanxes of the plurality,

인데, F_i는 i번째 지골이 상기 물체에 접촉하는 접촉점에서의 접촉력이며,

F _i is the contact force at the contact point at which the i-th phalanx contacts the object,

인데,

는 i번째 지골에서의 토크이다.

However,

Is the torque at the i-th phalanges.

를 제거한 후 상기 접촉력을 산출하도록 구성될 수 있다.
Similarly, when the i-th phalanx does not contact the object, the robot finger control unit removes the i-th row and the i-th row of the J _T matrix from the left side of the relational expression, removes F _i ,

And then calculate the contact force.

A control method of an insufficiently driven robot finger device according to another embodiment of the present invention uses a kinematic value of a robot finger including a plurality of phalanxes and a kinematic value of a kinetic transfer element between a plurality of phalanxes of a robot finger And calculating the contact force.

At this time,

The contact force can be calculated using the contact force,

From here,

J _T is an n by n matrix determined by the kinematic value of the robot finger, n is the number of phalanxes of the plurality,

인데, F_i는 i번째 지골이 상기 물체에 접촉하는 접촉점에서의 접촉력이며,

F _i is the contact force at the contact point at which the i-th phalanx contacts the object,

인데,

는 i번째 지골에서의 토크이다.

However,

Is the torque at the i-th phalanges.

를 제거한 후 상기 접촉력을 산출할 수 있다.
The contact force calculating step may include removing the i-th row and the i-th column of the J _T matrix at the left side of the relational expression when the i-th phalanx does not contact the object, removing F _i ,

The contact force can be calculated.

The insufficiently driven robot finger device according to the embodiment of the present invention efficiently calculates the contact force at the contact point in each phalanx and provides control based on the calculated contact force.

1 is a conceptual diagram according to a first embodiment of the present invention.
2 is a three degree of freedom example of the first embodiment of the present invention.
Fig. 3 is a view showing the number of cases in which an object of three degree of freedom degree is treated in the first embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, preferred embodiments of the present invention will be described. However, the technical idea of the present invention is not limited to these, and various modifications may be made by those skilled in the art.

Figure 1 shows a finger device 100, i.e., an n-phalanx finger device 100, having n phalanges that can be used in an embodiment in accordance with the present invention. The first phalanx 12 is rotatably connected to the base 2 at the first joint joint O ₁ and the second phalanx 22 is connected to the first phalanx 12 at the second joint joint O ₂ , And the third phalanx 32 is rotatably connected to the second phalanx 12 at the third joint joint O ₃ . Thus, the i-th phalanx is rotatably connected to the i-1 th phalanx at the i-th joint joint.

When an operating force T ₁ for rotating the first phalanx 12 by an actuator (not shown) is applied to the first phalanx 12 as an input, a part of the operating force T ₁ is transmitted to the first kinetic transmission element 14 ) it is transmitted to the second phalange 22 by a, so that the first phalanx (force (T _s2) for rotating the second phalanx (22) with respect to 12) is generated. The actuator may be any device capable of imparting rotational force, for example, a rotary motor or the like. A simple and highly adaptable finger device 100 can be obtained if an elastic means such as a spring is added thereto. For example, a torque spring is used for the second articulating joint O ₂ to prevent the second phalanx 22 from moving arbitrarily. The same description can be made from the second phalanx 22 to the nth phalanx, and repetitive description and illustration are omitted.

Kinematic passive elements can be used to increase the adaptability to the shape of the object handled and to mechanically constrain the fingers. The illustrated passive elements 14, 24 and 34 are four-bar linkages, each comprising a main drive bar, an insufficient drive bar and a sub-drive bar. In other words, the first passive element (14) relative to the first main drive bar (14a), the first main drive bar (14a) connected to one end of the first articulated joint (O ₁₎ to be rotatable relative to the base (2) a rotatably Once the first main drive joint (P ₁₎ of claim 1 sufficient driving bar (14b) and the first insufficient driving bar (14b) rotatably Once the first part drive joint (P _'2) in connected to the connected and the other end has a second articulated joint (O ₂₎ first drive bar portion (14c) that is rotatably connected to. The second manual element 24 and the following nth manual element can be equally described, and the repetitive description and the illustration are omitted.

The four-bar link is merely an example of a passive element, and various other passive elements that impart kinematic constraints may be used as appropriate.

The state in which the finger device 100 handles an object can be defined by the kinematic conditions of the robot finger and the contact point of the phalanxes 12, 22, 32,. That is, if the kinematic conditions of the robot finger and the contact points of the phalanxes (12, 22, 32, ...) are known, the operation of the robot finger can be analyzed.

In FIG. 1, the meaning of each symbol indicating the mechanical condition of the finger device 100 is as follows:

L _i : length of i-th phalanx (ie, i-th phalanx)

a _i : the length of the main drive bar of the i th four-section link (ie, the i th passive element)

b _i : Insufficient length of the i-th four-bar link (ie, i-th passive element)

c _i : length of the sub-driving bar of the i-th four-bar link (i.e., the i-th passive element)

θ _i : the rotation angle of the i-th phalanx (ie, the i-th phalanx) for the base (2) or i-1 phalanx

θ _ia is the rotation angle of the main drive bar of the first four-pass link (ie, the i-th passive element) to the base (2) or i-1 phalanx

ψ _i : the angle between O _i P ' _i and O _i P _i (where i> 1)

T ₁ : torque of the actuator at the first joint joint (O ₁ )

T _si : spring torque at i-th joint (O _i ) (where i> 1)

F _i : contact force with object at i-th phalanx

k _i : the position of contact with the object at the i-th phalanx (the distance from O _i to the contact point)

The distribution of the contact force depends on the position of the contact point and the spring torque applied by the spring. In the following, the static state of the finger device 100 is assumed for the sake of simplicity of calculation and explanation, that is, the acceleration due to the motion is ignored. Further, the friction is also ignored. Of course, it is also possible to consider dynamic states and friction for more accurate calculations.

The relation between input and output is as follows.

From here,

T is the input torque vector applied to each phalanx by the actuator and spring;

? _a is the corresponding angular velocity vector;

F is the contact force vector;

v is the projected velocity vector at the contact point.

Therefore, the following equation is obtained.

From here,

K _i is the stiffness of the torsion spring at the i-th joint (O _i );

는 i번째 관절 조인트(O_i)의 현재각과 최초각 사이의 차이다(단, i>1);Δ

Is the difference between the current angle and the initial angle of the i-th joint (O _i ), where i>1;

v _yci is the projected velocity in the y _i axis direction at the contact point of the i-th _phi .

의 벡터곱으로 간단히 표현될 수 있다. Thus, the projection velocity v is the derivative vector of the Jacobian matrix J _T and the gyro joint coordinates

As shown in FIG.

Here, the Jacobian matrix J _T of the projection velocity (v) can be obtained in a lower triangular form as shown below.

From here,

이고,

ego,

이다.

to be.

If we use the calculator to correlate the derivative vector of the geobio- plastic joint coordinates defined above with the driving Jacobian matrix J _a , the following equation is obtained.

In the insufficient drive finger model, a four-bar link is used to transmit the actuator torque to each phalanx, and the angular velocity of the four-bar link is the i-th four-bar link, O _i P _i P _{i i +1} O _{i +1} The following equation is obtained.

In the last four-section link O _{n -1} P _{n -1} P _n O _n ,

Therefore, substituting Equations (6) and (7) into Equation (5), the following expression can be obtained.

From here,

이고;

ego;

이며;

;

이고;

ego;

X _i is a function used to deliver actuator air torque to the i-th phalange.

From the equations (1), (3) and (5), the following equations are obtained.

의 경우에만 유효하다는 것이다. J_a는 특이성(singularity)을 가질 수 없다. 하지만, 핑거 장치(100)는 n보다 작은 수의 지골이 물체에 접촉하는 상태로 물체를 다룰 수도 있다.
Equation 9 shows a substantial correlation between the actuator torque and the contact force. The problem is that equation (9)

Is only valid for J _a can not have singularity. However, the finger device 100 may handle an object in a state in which a number of phials less than n are in contact with the object.

In order for an object to be treated with a smaller number of phalanges than n, active forces must be applied to all phalanxes that contact the object. And, the generated force at the phalanges not touching the object should be zero. However, equation (9) it can not be used to obtain the contact force when J _T matrix with specificity.

Equation (9) may be expressed as follows.

은 액추에이터, 스프링 토크, 액추에이터와 지골 사이의 토크 전달 함수와 관련되는 모든 관절 조인트에서의 토크 벡터

로서, 아래와 같은 식으로 표시할 수 있다.In Equation 10,

Is the torque vector at all joint joints related to the actuator, spring torque, torque transfer function between the actuator and phalanx

And can be expressed by the following expression.

In Equation (10), the left side can be expressed by the following equation.

Hence, Equation (10) becomes the following equation.

가 접촉력 벡터 F와 파라미터

에 대하여 아래와 같은 식으로 계산됨을 보여준다.Equation (13) represents the torque

Lt; RTI ID = 0.0 > F &

Is calculated as follows.

는 상관이 없으며, F_i는 0이된다. 즉, 이러한 조건에서 수학식 14는 적합하지 않고, i번째 지골이 물체에 접촉하지 않는 경우에는 토크

를 계산하는 데에는 수학식 14를 고려할 필요가 없다. 따라서, 수학식 13에서 F_i를 제외하고 접촉력 벡터 F를 계산하기 위해서는 아래와 같은 프로세스를 따른다.When the number of phials smaller than n contacts the object, for example, if the i-th phalanx does not contact the object,

And F _i is zero. That is, in this condition, the expression (14) is not suitable, and when the i-th phalanx does not contact the object,

It is not necessary to consider equation (14). Therefore, in order to calculate the contact force vector F except for F _i in the equation (13), the following process is followed.

는 존재하지 않기 때문이다.- Ignore the ith column in matrix J _T. Because all parameters

Is not present.

에 대하여 좌변에서 F_i=0이 되기 때문이다.- Ignores the i-th row in the matrix J _T. Because all parameters

F _i = 0 at the left side.

- Remove the F _i = 0 element of the contact force vector F from the left side.

의 i번째 관절 조인트에서의

요소를 무시한다.
- Torque vector on right side

Of the i-th joint joint

Ignore the element.

If the i-th row and the i-th row are thus ignored, the dimension of the J _T matrix is reduced to n-1 × n-1. Now J _T has no specificity. Hence, equation (13) can be used to calculate the contact force except F _i . The above process can also be used when two or more phalanges are not in contact with an object.

(3 degrees of freedom, example in 1-drive fingers)

Fig. 2 shows an example of a case where n = 1, i.e., a three-degree-of-freedom finger device 100. Fig.

인 경우에만 유효하다. 하지만, 도 3a 내지 도 3d에 예시된 바와 같이 핑거의 지골(12, 22, 32) 중 물체에 접촉하지 않는 것이 있을 경우(도 3b 내지 도 3d)가 가능하다.
In a deficient drive, Equation (9)

Is valid. However, as exemplified in Figs. 3A to 3D, it is possible that the finger's phalanxes 12, 22 and 32 are not in contact with an object (Figs. 3B to 3D).

In order to obtain the contact forces F ₁ , F ₂ , and F ₃ , the following four possible cases will be described.

(1) When all the phalanxes 12, 22, 32 come in contact with an object as shown in FIG. 3A

(2) As shown in FIG. 3B, the proximal phalanxes, i.e., the first phalanx 12 and the distal phalanx, i.e., the third phalanx 32, contact the object and the central phalanx, that is, the second phalanx 22, If the

(3) As shown in FIG. 3C, the central phalanx, that is, the second phalanx 22 and the distal phalanx, that is, the third phalanx 32, contact the object and the proximal phalanx, If the

(4) As shown in FIG. 3D, when only the distal phalanx, that is, the third phalanx 32,

(First case)

이며, 수학식 13은 아래와 같은 식이 된다.When all phalanxes 12, 22, and 32 are in contact with an object

&Quot; (13) "

In Equation (15), the contact force (F ₁ ) of the first phalanx is calculated according to the following equation.

From here,

이고;

ego;

이다.

to be.

In Equation 15, the contact force F ₂ of the second phalanx is calculated according to the following equation.

In Equation 15, the contact force F ₃ of the third phalanx is calculated according to the following equation.

(Second case)

를 제거하면 아래와 같은 식이 된다.When only the first phalanx 12 and the third phalanx 32 contact the object, k ₂ does not exist, and F ₂ becomes zero. The second row and second row associated with the second phalanges 22 in the J _T matrix in Equation (15) are removed and F ₂ and

The following equation is obtained.

Therefore, the contact force F ₁ in the first phalanx 12 is calculated in the following manner.

The contact force F ₃ in the third phalanx 32 is as shown in the following equation (18).

(Third case)

을 제거하면 아래와 같은 식이 된다.When only the second phalanx 22 and the third phalanx 32 contact the object, k ₁ does not exist and F ₁ becomes zero. In Equation (15), the first column and the first row associated with the first phalanx 12 in the J _T matrix are removed, and F ₁ and

The following equation is obtained.

The contact force F ₂ at the second phalanx 22 is calculated by the equation 17 and the contact force F ₃ at the third phalanx 32 is calculated by the equation 18.

(Fourth case)

을 제거한 후, 제2 지골(22)에 관련된 제2열 및 제2행을 제거하고, F₂ 및

를 제거하면 아래와 같은 식이 된다.
When only the third phalanx 32 contacts an object, k ₁ and k ₂ do not exist, and F ₁ and F ₂ become zero. In Equation (15), the first column and the first row associated with the first phalanx 12 in the J _T matrix are removed, and F ₁ and

The second row and second row associated with the second phalanx 22 are removed, and F2 and < _{RTI ID = 0.0} &_gt;

The following equation is obtained.

The contact force F ₃ at the third phalanx 32 is calculated by the following equation (18).

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: finger device
2: Base
12: first phalanx 14: first manual element
22: second phalanx 24: second manual element
32: third phalanx 34: third manual element

Claims (14)

A robot finger adapted to be in direct contact with an object;
A robot finger control unit configured to control the robot finger,
The robot finger device comprising:
Wherein the robot finger comprises a plurality of phalanxes,
A first phalanx rotatably connected to the base at the first joint joint,
A second phalanx rotatably connected to the first phalanx at a second joint joint,
A third phalanx rotatably connected to the second phalanx at the third joint joint;
/ RTI >
Wherein the robot finger control unit calculates a contact force with the object using the kinematic values of the robot finger in each of the plurality of phalanxes,
The kinematic values of the robot fingers,
A length of each of the plurality of phalanxes,
A distance from the first joint joint to a contact point at which the first phalanxes contact the object, and
And a distance from the second joint joint to a contact point at which the second phalanx contacts the object.
The method according to claim 1,
An actuator for rotating the first phalanx against the base at the first joint joint;
A first kinetic transmission element for transmitting part of the rotational operating force applied to the first phalanx by the actuator to the second phalanx to rotate the second phalanx against the first phalanx at the second joint joint;
A second motion transmitting element for transmitting a part of the rotational operating force applied to the second phalanx by the first motion transmitting element to the third phalanx to rotate the third phalanx against the second phalanx at the third joint joint,
The robot finger device further comprising:
3. The method of claim 2,
The first motion transmission element
A first passive element for mechanically restraining a position of the second phalanx against the first phalanx;
A first spring for applying a first spring torque as a second rotational operating force to the second phalanx at the second joint joint,
It includes
The second motion transmission element
A second passive element mechanically restraining a position of the third phalanx against the second phalanx;
A second spring for applying a second spring torque as a third rotational operating force to the third phalanx at the third joint joint,
The robot finger device comprising:
The method of claim 3,
The first passive element
A first main drive bar rotatably connected to the first joint joint,
A first insufficient drive bar rotatably connected to the first main drive bar and having one end connected to the first main drive joint,
A first sub-drive bar rotatably connected at one end to the first sub-drive joint and at the other end rotatably connected to the second joint joint,
And a first four-bar link structure including a first four-
The second passive element
A second main drive bar, one end of which is rotatably connected to the second joint joint,
A second insufficient drive bar rotatably connected to the second main drive bar and having one end connected to the second main drive joint,
A second sub-drive bar rotatably connected to the second insufficient drive bar and having one end connected to the second sub-drive joint and the other end rotatably connected to the third joint joint,
And a second four-bar link structure including a second four-bar link structure.
delete delete The method according to claim 1,
Wherein the robot finger controller comprises:

To calculate the contact force,
In the above relationship
k _i is the distance from the i-th joint to the contact point at which the i-th phalanx contacts the object;
F _i is the contact force at the contact point at which the i-th phalanx contacts the object;
T _i is the torque at the i-th joint joint;

;
Where L _k is the length of the k th phalanx,
and _m is the rotation angle of the m-th phalanx with respect to the base or m-1 th phalanx.
8. The method of claim 7,
The robot finger control unit removes the i-th row and the i-th row of the matrix from the left side of the relational expression when the i-th phalanx does not contact the object, removes F _i ,

And the contact force is calculated.
delete delete delete delete delete delete

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