JPS6171986A - Measurement system of external force - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for measuring external force in a robot equipped with a force sensor, and in particular, the present invention relates to a method for measuring external force in a robot equipped with a force sensor, and in particular, the same measurement method is applied even when the final operator is changed or its position and orientation are changed. It has 3 pages and is about an external force measurement method that can add 11 forces and moments that act on the final operator from the outside according to the principle.

[Background of the invention]

Until now, force feedback control using force sensors attached to robots has been used for direct teaching, etc., but any method for measuring the external force acting on the final operator is unique to the final operator attached to the robot. It has become. That is, if the final operator is changed or its position and orientation are changed, the same measurement method cannot be applied as is. Note that the final operator herein refers to the tip end of the arm excluding the force sensor, and is defined as including not only the hand itself but also objects grasped by the hand.

[Purpose of the invention]

Therefore, an object of the present invention is to provide an external force measurement method that can measure external force on a final operator by applying the same method even if the final operator is changed or its position and orientation are changed.

[Overview of the invention]

For this purpose, the present invention calculates the weight and center of gravity of the final operator by comparing the theoretical values, in which the weight and the center of gravity are included as unknowns, with the actual values detected by the force sensor. In addition, the force (moment)1 acting externally on the final operator is calculated based on the weight, the center of gravity position, the position and orientation of the final operator, and the output of the force sensor.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 to 6.

First, a multi-degree-of-freedom robot equipped with a force sensor will be explained. FIG. 1 shows its external configuration, and as shown in the figure, a hand 3 is attached to the tip of an arm 1 via a force sensor 2.

In this case, the force sensor 2 can detect the translational force in the direction of rotation and the rotational moment around a point υ fixed to the sensor.
Moment QS-(FsIlx, F8Ily, F crystal.

M8Ill, , M,8. , , M, B, ) and senna output V8: (V84, ・.

vst ) (t>6) is related to the stiffness matrix [A) of the sensor as follows.

-5-page vs- [A: Screw ・・・・・・(1
) However, [A] is a matrix with 2 rows and 6 columns, and t is the number of channels of the senna output.

Equation (11) can also be transformed as follows using the analogous inverse matrix [A+:l* of [A].

Possible=[t]8 ・・・・・・(2) However, C”
13-([A)'[A])-1[A)'Ashi, [
A) 1 and [A]-1 represent the transposed matrix and inverse matrix of [A], respectively.

FIG. 2 shows various coordinate systems fixed to the hand, its surroundings, and the base of the robot. Coordinate system 8b-ma b
ib revenge 1 stone S-maSwa S78. The robot base, the force sensor, and the hand are respectively fixed to coordinate systems (hereinafter, the respective coordinate systems are referred to as B system, B system, and H system). In addition, in the figure, ih
is the position vector of the origin of the B system as seen from the H system, and 7
H,? 1. Hundred is SS from the perspective of H system
The unit vector in the X - yv Z axis direction of the S B system is further expressed as Q
, a, and J are unit vectors in the X + 7 + Z axis direction of the B system as seen from the H system.

FIG. 3 shows a block configuration for determining the weight of the hand including the object (work) and the position of its center of gravity.

Here, the unit vector W5b in the direction of gravity seen from the B frame
When bbb is ug ``gx 'ugy' ugz), the unit vector Hp in the direction of gravity seen from the H system is expressed as follows.

uD `` ugx i'4 '' ugy gD '' murmur J ''''... (Jl Also, the weight of the hand is 1 (il-W,
If the position vector of the center of gravity of the hand as seen from the H system is il, the square and moment formation due to the weight of the hand as seen from the H system are as follows.

Q=wXR・・・(4) ξ= Mh×−■・・・・・・(5) Equation (5) can be further transformed into a matrix of 3 rows and 3 columns as follows. Ru.

hhh is XiR's X * yv, however, ugx
Lugy + ug 77 pages in 2 directions.

On the other hand, if the force and moment in the S system detected by the force sensor are respectively F':' and M:', when viewed from the H system, they are expressed as follows.

廼′−FB′い+p8′、h+FB′100h
・・・・・・(7)s sxs sys
sz s sub' = M:'x7h + M
, 8'yih + M, 8', p + p h X
ph'・・・・・・(8) However, is/, Fs/
, Fs/ is the X * yrsx of is/, respectively
sy sz s2
It is a directional valve, and M:'x4 M:/y1M:'z are the X·7+Z direction components of M'', respectively.

In addition, the force and moment due to the weight of the hand detected by the force sensor are ih' and ``, respectively, from the H system.
4', the sensor output Vg at that time and equation (2).

(7) and (8) The following equations (9) to αυ hold true.

h'a11a' h tl h ,,0
．． , QO)Fg −Fgx fs +Fgy gs +
Fgz hs town = yr:'xt': +yrj'yg
': + to yr8 +d x y'j'...
・(11) However, Fj' and Mj' are each hand Mg'y ' from the S system, and M8 is X+yr of MB'.
Indicates the Z direction component.

By the way, Yuzu 9 strength and formula α in formulas (4) and (5)
1. (The relationship between 7W and ξ′ at 1υ is as follows.

"h-door'...a4
g ii' - y' . . . 0 Therefore, the following formula (+4), Q5) holds true regarding the force and moment due to the hand's own weight.

Scolding - Isshuo...A Xun said,
If the hand posture (f”n (n〉2)) surface quality is to be obtained, n
The set of equations (14), a! 19 is established.

1---page That is, formulas H and αD are generally expressed as follows.

Fg = [:Bl) w ・
・・・・・・(1 second yrQ = w [c) ”'4
・・・・−(19h If w + dg is an unknown quantity, Equation (181, H is generally impossible, but if we consider the least squares solution, W, “vomit is”)
This is the position of the center of gravity. Therefore, the hand weight can be obtained from equation aQ as follows.

W: [B+) Fi...
・・翰10 了1 However, [B':] - ([B':l [B]) [B]
It is.

In addition, if we change the posture n times so that the gravitational direction vectors seen from the H system are not parallel for any two postures among the postures of the hand changed in n planes, we can use the equation (1
G, (21) The position of the center of gravity can be found as follows.

ah = # [C+:] 4 wheels...
01) However, [c+)= ([:c)'(C] )-'
[c]'.

In addition, to briefly explain the relationship between each of the above formulas and the main calculation blocks in FIG.
] 1n performs the calculation shown in equation (3), calculation blocks 121 to 12n perform the calculation shown in equation (9), and calculation blocks 131 to 13n perform the calculation shown in equations OI and 0υ. There is. In the calculation block 14, the calculation shown in equation (2) is performed, and in the calculation block 15, the calculation shown in equation (21) is also performed.

FIG. 4 shows a block configuration for determining force and moment acting on the hand.

As shown in FIG. 5, an external force F is applied to the hand 3. , Momen 11
- The page becomes p or less according to equation (2) when viewed from the S thread.

These FSIMS are also expressed by the equation (force, (8)
It is converted as follows.

ph = FEI ill + pg gh + F8
p, ,,,, (23xs ys z
s 1 = M870 + 吋■ + Maqjuki x Yuzu ・・・・・・(
24) However, F-Ying, 2nd base, and the mark are each X on p8 *
y+2 direction component, and Mx e % l M: indicates the X + ys z direction component of Ml, respectively.

On the other hand, the force and moment detected by the sensor consist of an external force, a moment, a force 4 due to the hand's own weight, and a moment.

剋−i + ph・・・・・・(
2 clauses g 1 = 100 degrees ・2ce Here, the force 4 due to the hand's own weight and the moment force are . υ has become something that is sought after. Therefore, according to equations (25) and (26), the force and moment acting on the hand can be obtained as follows.

1-V-廼 Scream...(5)e
g Sub-1h- Building ・・・・・・(c) Furthermore,
In FIG. 4, the calculation block 21 performs the calculation shown in equation (221), and the calculation block n performs the calculation shown in equation (c).

The calculation shown in C24) is performed. Furthermore, in calculation block n, 1! based on equation (3)! !碩 is calculated, and in this ■, Vlz → is expressed as the formula (
4) , (by acting as shown in 51)
It has become a trap that requires strength. Subtractor 5 is 廼.

Yay p? 1. , Yuzu by subtracting 4.

The river is needed.

FIG. 6 shows the configuration of the control drive system for the robot. When carrying out the present invention, the teaching pendant 31 is operated with the hand 3 holding nothing or a workpiece of some kind, and the hand 3 is placed at an appropriate position. The posture is now forced. In this case hand 3
vector indicating the attitude of ``j: , Q is the displacement detector (
The displacement of the actuator detected by an encoder (not shown) is stored in a memory circuit in the robot controller 32. At the same time, the output of the force sensor 2 is also stored. In the following pages, the teaching pendant 31 will be operated multiple times while changing the position and orientation of the hand 3, and the position and orientation of the hand and sensor output for each operation will be memorized. can be found. A vector ph, ′? indicating the position/posture relationship between the hand 3 and the force sensor 2? l.

Since B a I hR+ u is determined in advance by the specifications of the robot and the installation position, the position and orientation obtained each time the above operation is performed, the output of the force sensor 2, the weight of the hand 30 and its center of gravity according to Fig. 3. is what is required. Note that the position and orientation operations for the hand 3 may be programmed in advance.

14-.

After the weight of the hand 3 and the position of its center of gravity are determined, the external force applied to the hand 3 when the robot performs work according to the teaching pendant 31 or program commands is determined by the posture of the hand, which can be found from the displacement of the actuator, and This is obtained from the force sensor output according to FIG. Note that the reference numeral 33 in FIG. 6 indicates a servo amplifier.

In this way, even if the type of hand and its position and orientation are changed, the external force and moment can be easily determined based on the output of the force sensor and the position and orientation of the hand using exactly the same method. ffOchi,
There is no need to change the external force measurement method when changing the hand, and there is no need to perform pre-installation processing such as measuring the center of gravity position of the hand. Therefore, even if the hand attached to the tip of the robot arm is converted, or if the hand is working while gripping a seal, the weight required to determine the external force can be reduced by changing the posture of the hand at least twice. Since the position of the center of gravity is known, it is easy to replace the hand and seal during work.

In addition, it is possible to detect in real time only the reaction force required for fitting work, for example, which is applied to the workpiece, and feedback control can be performed easily.

〔Effect of the invention〕

As explained above, the present invention has the advantage that even if the hand or its position/orientation is changed, the external force or moment acting on the hand can be easily measured using the same method.

[Brief explanation of drawings]

Figure 1 is a diagram showing the external configuration of a multi-degree-of-freedom robot equipped with a force sensor, Figure 2 is a diagram to explain the coordinate system fixed to each part of the robot, and Figure 3 is a diagram showing the coordinate system fixed to each part of the robot. Figure 4 shows the block configuration for determining the weight of the hand and the position of its center of gravity.
FIG. 5 is a diagram illustrating the external force and moment acting on the hand, and FIG. 6 is a diagram showing the configuration of the control drive system together with the robot. 1...Arm, 2...Force sensor, 3...Hand. Figure 1 Figure 4 Figure 5

Claims (1)

[Claims] 1. A method for measuring the force and moment acting on the final operator attached to the arm through a force sensor capable of detecting force in any direction and moment around a reference point, which is external. In a state where no force or moment is applied,
The weight and center of gravity position of the final operator are calculated by comparing the theoretical force and moment values, which include the weight and center of gravity position as unknowns, with the actual force and moment values detected by the force sensor. a force acting on the final operator from the outside based on the weight and center of gravity position, the position and orientation of the final operator, and the output of the force sensor;
An external force measurement method characterized by determining moments. 2. The weight and center of gravity position of the final operator are determined by the theoretical force and moment values corresponding to the position and orientation obtained by changing the position and orientation of the operator, and the force and moment corresponding to the position and orientation detected by the force sensor. The external force measurement method according to claim 1, which is determined by comparing with the value of . 3. The force and moment acting on the final operator from the outside are:
the force acting on the final operator detected by the force sensor,
The external force measurement method according to claim 1, wherein the external force measurement method is obtained by subtracting the force and moment due to the weight of the operator from the moment. 4. Theoretical force and moment values corresponding to position and orientation,
The force and moment values corresponding to the position and orientation detected by the force sensor are defined as simultaneous equations regarding the weight of the final operator and the position of the center of gravity, and the weight and the position of the center of gravity are obtained as a least squares solution. External force measurement method described in Section 2.