JPS6190895A - Force sensor transformation matrix detection method - 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 is directed to the measurement of strain in a six-axis force sensor (that is, capable of detecting three components of force and three components of torque) mounted on a robot.
The present invention relates to a detection method for automatically detecting a transformation matrix indicating the relationship between forming pressure and force (force and torque are collectively referred to as "force").

[Background of the invention]

A force sensor is attached to the robot to find the relationship between force and strain voltage at the relevant part. The relationship between strain voltage and force is uniquely determined, el, and the equation is as follows.

F=(B)V ・・・・・・・・・・・・(1
)be. [B] is a constant indicating the relationship between F and V, and is generally called a transformation matrix. Both F and V can be expressed as vectors.

A conventional example of calculating the transformation matrix [B] is USP.

4094192 r Method and Aonar
atus for Six Degrees of Free
dom There is Farce Sensing J0
This conventional measuring device is shown in FIG. The force sensor 2 is fixed and attached to the base 1. A cable 4 is attached to the moving part 3 of the force sensor 2, and a weight 5 is suspended from the tip of the cable 4 via a pulley. With such a device, the number of strokes of the weight 5 can be changed, and the way in which the cable 4 is attached can be changed. By doing this, we obtain the data necessary for the transformation matrix and calculate the transformation matrix. This conventional example is an effective method for calculating the transformation matrix, but
It has problems that require a lot of effort and time.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting a transformation matrix of a force sensor, which makes it possible to detect a transformation matrix while the force sensor is attached to the lopinoto itself.

[Summary of the invention]

The present invention shows that attaching a force sensor and a standard workpiece to a logget and taking different postures is equivalent to applying many independent forces (force and torque) to the force sensor. I was disgusted by the layers. A force sensor and an appropriate standard workpiece are attached to the skin and mouth of a pregnant woman, and the transformation matrix is automatically detected by simply shaking the head and assuming several different postures based on certain conditions. I decided to do so.

[Embodiments of the invention]

FIG. 2 is a detailed explanatory diagram of the present invention. Arm 11 is an arm that constitutes a part of Robinoto.

A force sensor 1 is installed between the tip of the arm 11 and the hand portion 13.
Install 2. This force sensor 12 is a strain gauge,
In response to the force applied to the hand portion 13, a strain voltage corresponding to the force is generated. Here, force refers to both force and torque. This force becomes a six-dimensional vector.

Base coordinate axis (ob Xb7bzb) and force sensor 1
As shown in FIG. 2, it is different from the coordinate axes of No.

The configuration of the force sensor 12 is shown in FIG. It consists of an outer member 21, an inner member n, and a thin plate member n. The external member 21 is fixed to the tip of the arm part 11, and the internal member n is fixed to the band part 13.
Fixed to. The thin plate member 22 has an inner member% and an outer member 2
Connect with 1. A strain gauge is attached to a part of this thin plate member 4.

With this configuration, when a force is applied to the hand portion 13, the force is transmitted to the internal member B connected thereto, and the strain gauge is deflected via the connecting plate 24. A voltage corresponding to this distortion appears at the output terminal of the distortion goojim, resulting in voltage detection. Here, the relationship between force and strain voltage is uniquely determined by appropriately determining the number, dimensions, and mounting positions of the thin plate parts, the number of strain gauges to be attached, and the like. Therefore, force can be detected from the thick tower of strain voltage. The transformation matrix [B] determines the relationship between this force and strain voltage.

(1) Prerequisites for finding the transformation matrix [B].

Strictly speaking, the strain voltage V of the force sensor 12 is V=vo-vd
・・・・・・・・・・・・It can be specified by (2).

Here, ■ is the voltage generated when no force is applied to the force sensor 12 (internal weight is also considered as force). This VN is
It becomes an n-dimensional vector.

vo is a voltage generated when force (internal weight is also considered as force) is actually applied to the force sensor 12. This voltage v
o is also an n-dimensional vector. However, n≧6.

The force F is a force applied to the force sensor 12, and is considered in terms of sensor coordinates. This force F consists of force and torque and becomes a six-dimensional vector.

Furthermore, it is assumed that the force F and the strain voltage V have a linear relationship. As a result, F=[B)V ・・・・・・・・・・・・(3)
holds true. Here, CBI is a matrix of 6 rows and n columns.

(2) Procedure for determining voltage vd.

Internal weight cannot be ignored. However, the internal weight W
in, the center of gravity position din of the internal weight ('s shown in Figure 2)
The value expressed in the sensor coordinate system (hereinafter referred to as the S system) indicated by s is determined in advance using a design drawing or the like, so it can be considered to be known.

I would like to find the strain gauge voltage vd when the internal weight Win is removed, but +Win is part of the sensor and cannot be removed. Therefore, we will take the following method.

The force sensor 2 is attached to the tip of the arm portion 11 of the logo nose. Furthermore, do not attach anything to the tip of the tip sensor 2. Therefore, the hand portion 13 as shown in FIG. 2, which is the actual logo-nod operation system, is not attached.

Therefore, the robot is operated so that the position ml111z of the sensor coordinate system faces downward, that is, toward the direction of gravity. The strain voltage is measured by the force sensor 2 under the condition that the coordinate axis 2 is in the direction of gravity. Let this strain voltage be vdow.

Next, set the coordinate axis 2 of the sensor coordinate system in an upward posture,
Under this posture, the force sensor 2 measures the strain voltage. ■ This distortion voltage. , and so on.

From Vdow and V up , voltage Vd is determined by the following equation.

"a = ('dow + "up)/2 ---
(4) These downward and upward directions are based on the concept of reversing the posture with respect to the direction of gravity, so that the positive and negative of the sword and torque generated by the internal weight of the force sensor are reversed and canceled out. becomes zero. Now, the unit vector in the direction of gravity when facing downward is "dow" (S system display), and the unit vector in the direction of gravity when facing upward is Uu.
(S-system display). However, both are considered in the sensor coordinate system. In this case, u do W=u up
”””””” (5). Therefore, force F1. The torque F2 is as follows.

Therefore, equation (4) is correct, and voltage vd can be found from equation (4).

(3) Procedure for determining strain voltage V and force F.

A standard workpiece is attached to the force sensor 12 in place of the grip section 13 shown in FIG. Figure 4 shows a perspective view of the standard workpiece installed. The standard workpiece 31 has a weight Wst
, the original center of gravity position dat of the sensor coordinate system. It is assumed that both W and j l d3t are known.

Since the standard workpiece 13 W and t are added to the internal weight Win, the weight W of both is W=Win
+ ”st −・−・・(8).

On the other hand, the center of gravity position d (S system display) is d = (Win' d in + Wst'', 0
/(Wt n+Wat ) (9).

Here, as shown in FIG. 2, in the coordinate system ('b Xb Ybzb) of the base of the arm 11, the unit vector indicating the direction of gravity is defined as i. This i is known.

Let 13 be the unit vector indicating the direction of the center of gravity in the sensor coordinate system. Let f , g , and h be unit vectors in each coordinate axis direction in the sensor coordinate system. Under this condition, the following formula holds true.

"s ="' g , ' ) T' y b ・” ・
..."' (io) Now, let's say that the force and torque are collectively F when considering both the internal weight of the force sensor and the weight of the standard workpiece.

becomes. Here, F is expressed as a sensor coordinate system, and torque is torque around the origin in the sensor coordinate system. F is a six-dimensional vector.

The six elements of vector F are the x, y, and z axis components of force.

Of torque! ,7. Refers to the Z-axis component.

On the other hand, the strain voltage V can be found from (2). That is, by finding the actual strain voltage vo and subtracting the voltage vd from this vo, we get ■
can be found.

(4) Procedure for finding 11 CB].

The process described in item (3) above is an example of measurement using one posture and one standard workpiece. In reality, measurements are taken under various conditions, including changing the posture and changing the standard workpiece (changes in weight and center of gravity position).

Therefore, (posture al l work b,), (posture IL2
If measurements are made for each of r workpieces b2), . . . (posture aml workpiece bm), the following will be obtained. 02) When formulas are summarized in a matrix, it becomes...03). Here, [Fl, F2. ..., Fm] is a matrix with 6 rows and m columns, [B] is a matrix with 6 rows and n columns, (Vl + F
2 + "', V day is a matrix of 5 rows and m columns. However,
m≧5. n≧6. Also, F, , F2. ...,
It is assumed that Fm includes at least six independent vectors.

03) The formula is CFL + "2 + "' + Fm]
CFI, CV+.

F2. ..., vm] as CVI, CF)=
(B) [v] ......04). Therefore, jB:]m=F:] [V]” ・・・・・・
... α5). However, [V]*=[v)T[[v][v)T]-1...
...(16). From formula 05), the transformation matrix [B
] can be found.

(5) Modification example.

Although the above embodiments are methods using different postures and different sets of workpieces (for example, six sets), other methods are also possible. As shown in FIG. 5, a workpiece 34 having its center of gravity on the z3 axis is attached to the sensor 12 and is made to take various postures.

An example of the posture is shown in FIG.

Figure 6 shows five postures, (a) facing downward, (b)
is an inclination of +451' around the x' axis, (C) is an inclination of -45° around the x' axis, (d) is an inclination of +45° around the y'5 axis.
The inclination of (C) shows the inclination of -45° around the y' axis.

In both cases, we consider the coordinate axes of the base system. That is, 01
)-x'b-y', -3'5 coordinate system is the base system's corresponding x, y, two axes and x-shi.

The coordinate system has the same attitude as the yb and b axes, and the origin oG can coincide with the origin 0 of the sensor system.

Under the five postures shown in Figure 6 above, each force'
+ Fb + "C+ Fd r Fe. These five vectors are independent vectors. For one workpiece, only a maximum of five independent vectors can be obtained just by determining the posture, but with this method, six independent vectors can be obtained. Therefore, as shown in FIG.
Attach to 2. Next, have them assume a posture in which the moment around the z-3 axis is not zero. In this attitude, it is assumed that the vector is the 6th independent vector (however, m=6).

Therefore, by substituting Fa-Ff into equation 03), the voltage of the corresponding strain gauge v, , Vb, , ·, v( is expressed as "l *
By substituting F2 r ”'vm, we get [B
] can be obtained.

(6) Other variations.

The above example is just an example, and the types of workpieces, the number of workpieces, the types of postures, and the postures may be selected in any way as long as the condition that they contain at least 6 independent F's is satisfied. do not have. Therefore, the conditions when calculating [B] are, for example, (a) the change in Sa of the workpiece should be minimized (b) the posture of the workpiece should be as close to the downward position as possible (・') a good [B] of one treetop. An appropriate combination can be selected according to each request such as what one wants to obtain.

Also, for convenience of explaining the posture, O', -x', -y'5
−z′.

Although a coordinate system has been defined, other coordinate systems may be used as necessary.

〔Effect of the invention〕

According to the present invention, the transformation matrix can be detected using o+yt itself without using a dedicated device.

This resulted in a reduction in calculation time and labor.

[Brief explanation of drawings]

Figure 1 is a diagram of a conventional example, Figure 2 is a diagram of an embodiment of the present invention, Figure 3 is a side view of the structure of the force sensor, Figure 4 is a diagram of a standard workpiece attached, and Figure 5 is a diagram of another standard workpiece. FIG. 6 is a diagram showing a case where a workpiece is attached, FIG. 6 is a diagram showing a measurement mode, and FIG. 7 is a diagram showing another measurement mode. 10... Base part of loggett, 11... 7-m part,
12...force sensor, 13...hunt part. Agent Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3 Prisoner Figure 4 Figure 6 Figure 6 2 et al.↑ Figure 7

Claims (1)

[Claims] 1. A force sensor installed between a robot arm and a hand section, which sensor applies a force @F@ to the hand section.
A detection method for detecting the transformation matrix [B] when the characteristic is to generate a distortion voltage @V@ with the relationship @F@ = [B] @V@ (where [B] is a transformation matrix). In this process, various standard workpieces with known weights and center of gravity positions are successively attached to the tip of the force sensor attached to the tip of the robot arm, and the strain voltage of the force sensor @V@ with the standard workpieces attached is A method for detecting a transformation matrix of a force sensor, in which a force @F@ consisting of N and force/torque is determined, and a transformation matrix [B] is detected from the obtained @V@ and @F@. 2. A force sensor installed between the robot arm and the hand section, which measures the force @F@ that the sensor applies to the hand section.
A detection method for detecting the transformation matrix [B] when the characteristic is to generate a distortion voltage @V@ with the relationship @F@ = [B] @V@ (where [B] is a transformation matrix). At least two standard workpieces are attached to the tip of a force sensor attached to the tip of a robot arm, and the postures of the standard workpieces are successively changed to measure the strain voltage @V@ of the force sensor and the force A method for detecting a transformation matrix for a force sensor, in which a force @F@ consisting of torque is determined, and a transformation matrix [B] is detected from the obtained @V@ and @F@.