JPH0716903B2 - Articulated robot gravity balancer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gravity balancer for an articulated robot.

(Prior Art) Recently, an articulated industrial robot is widely used in various fields, and FIG. 2 is a perspective view showing an example of such an articulated industrial robot.

In the figure, the industrial robot has a robot substrate 10,
The robot substrate 10 is mounted on a horizontal base 12 so as to be movable in a direction indicated by an arrow "I". Reference numeral 14 is a bellows device for protecting the moving surface of the robot base 10 on the horizontal base 12.

At the upper end of the robot base body 10, the trailing end of the robot upper arm 16 is pivotally attached along the C ₁ axis, and thus the robot upper arm 16 is provided so as to be swingable in both directions indicated by an arrow “II”. . Also, on the upper end 18 of the robot upper arm 16,
A robot forearm 20 is provided so as to be able to oscillate in both directions indicated by an arrow "III" with respect to the C ₂ axis. A wrist portion 30 is attached to a tip 24 of a forearm main portion 22 extending forward from the C ₂ axis line of the robot forearm 20, while a relatively short rearward extension portion 26 is provided rearward from the C ₂ axis line. is doing.

The wrist portion 30 is composed of a wrist base portion 32, an inner wrist 36 held by a forked support portion 34 fixed to the wrist base portion 32, and a hand holding portion 38 attached to the inner wrist 36. There is. The wrist base 32 is formed so as to be pivotable in both directions indicated by "IV" with respect to the forearm main portion 22, and the inner wrist 36 is provided with a forked support portion 34.
On the other hand, it is formed so as to be swingable in the direction indicated by the arrow "V", and the hand holding portion 38 is formed so as to be freely rotatable in both directions indicated by the arrow "VI".

The robot base 10, the robot upper arm 16, the robot forearm 20, and the wrist 30 described above are provided with drive sources for driving various operations thereof. A motor (not shown in the figure) built in the horizontal base 12 serves as a drive source for the robot base body 10 in the arrow "I" direction, and a motor M ₁ for swinging the robot upper arm 16 in the arrow "II" direction. As the motor M _{1 on} the rear side of the upper arm 16.
Motors (not shown in the figure) arranged in parallel with are provided as the drive sources for the hoisting motion of the robot forearm 20 in the direction of arrow "III", respectively. Of course, various mechanisms such as a motion transmission mechanism, a direction changing mechanism, and a speed reduction mechanism are provided between the three motors forming these driving sources and the respective driven parts, so that proper operation control of the driven parts can be achieved. And 48, 50 are part of their mechanism.

In addition, the motors M ₂ , M ₃ , and M ₄ are the wrist base 32 of the wrist 30,
It is a drive source that drives each part of the inner wrist 36 and the hand holding part 38, and is collectively provided in the rear extension part 26 of the forearm 20.

Reference numeral 40 denotes a machine frame portion for accommodating a motion transmitting mechanism or a speed reducing mechanism for transmitting the rotation of the output shafts of the motors M ₃ and M ₄ , and 42
Is a machine case portion in which a motion transmitting mechanism or a speed reducing mechanism for transmitting the rotation of the output shaft of the motor M ₂ is housed.

3 and 4 are a perspective view and a side view showing another example of the joint type industrial robot.

In the figure, a traveling base b is attached to a fixed base a so as to be movable along the Y-axis direction, that is, the longitudinal direction of the fixed base a. A robot torso C is arranged on the traveling platform b, and a robot upper arm d is provided on the robot torso C so as to be swingable around a W axis extending in a direction parallel to the traveling surface of the traveling platform b. There is. The robot forearm e is W on the robot upper arm d.
It is provided so that it can oscillate around a U axis that is parallel to the axis.
A triaxial wrist device including a first wrist base portion f, a second wrist base portion g, and a wrist tip portion h is attached to the robot upper arm d.

The first wrist base f is rotatably provided about the β axis orthogonal to the U axis with respect to the second robot forearm e, and the second wrist base g is aligned with the β axis with respect to the first wrist base f. It is provided so as to be rotatable around the γ-axes that intersect at right angles.

Further, the wrist tip end h is attached to the second wrist base g so as to be rotatable about an α axis orthogonal to the γ axis. i
Is an extension of the robot forearm, j is a first support, and k is a second support.

By the way, the joint type industrial robot as shown in FIGS. 2 and 3 is a multi-joint type robot using a parallel four-bar linkage mechanism, and this parallel four-bar linkage mechanism part is as shown in FIG. It can be represented schematically. Figure 6 shows
It is explanatory drawing of the moment force which acts on a robot in the schematic diagram of FIG.

In FIG. 5, C ₁ ′ is the pivot point of the first and second joints, indicating the position of the fulcrum. C ₂ ′ is the pivot point between the 1st and 4th sections, C ₃ ′ is the pivot point between the 3rd and 4th sections, and C ₄ ′ is the pivot point between the 2nd and 3rd sections. Is. W _{1 to} W ₄ are gravitational forces acting on the first to fourth nodes, and l ₁ g to l ₄ g are distances from each pivot point to the gravity action point.

Here, Section 1 or the robot upper arm and Section 4 or the robot
The rotation angles θ and ψ of the forearm and the points of gravity action
Angle α₁~ Α_FourAs shown in Fig. 5 and act on each pivot point
The vector direction of the moment force is determined as shown in Fig. 6.
And the parallel four-bar linkage mechanism,
A good equation holds. In addition, T_θ, T Respectively θ
The torque acts on the axis and ψ axis.

Section 1 T_θ＋ W₁l₁g sin (θ + α₁) −F₁₄xl₁ cos θ + F₁₄yl₁ sin θ = 0 (1) Section 2 T + W₂1₂g cos (ψ + α₂) −F_{twenty three}xl₂ sin ψ + F_{twenty three}yl₂ cosψ = 0 (2) Section 3 F_{twenty three}x-F₃₄x = 0 (3) F_{twenty three}y-F₃₄y-W₃= 0… (4) W₃l₃g sin (θ + α₃) −F₃₄xl₁ cosψ + F₃₄yl₁ sin θ = 0 (5) Section 4 F₁₄x + F₃₄x = 0 (6) F₁₄y + F₃₄y-W_Four= 0… (7) W_Fourl_Fourg cos (ψ + α_Four) + F₁₄xl₂ sin ψ−F₁₄yl₂ cos ψ = 0 (8) As described above, it is assumed that the moment acts on each node.
And transform the formula in sequence_θ, T And ask for
It is expressed as follows.

T_θ=-(W₁l₁g + W₃l₃g + W_Fourl₁) Sin θ (9) T =-{W₂l₂g + W₃l₂＋ W_Four(L₂-L_Fourg)} cosψ… (1
0) However, in order to simplify the explanation in the process of transformation, α₁~ Α_Four
= 0.

(Problems to be Solved by the Invention) As is clear from the expressions (9) and (10), the torques acting on the θ axis and the ψ axis are controlled by the robot control angles θ and ψ, respectively.
Since it fluctuates depending on the change of, there is a problem that the balance around the joint cannot be perfectly maintained and it is difficult to perform accurate control.

Therefore, in the present invention, a balance weight is attached at an optimum position to facilitate balancing around joints.

(Means for Solving Problems) The present invention relates to a robot upper arm having a tail end swingably mounted on a robot base, a robot forearm pivotally attached to an upper end of the robot upper arm so as to be capable of undulating, and the robot upper arm. An extension formed behind the pivot point of the
In a joint type robot in which a parallel four-bar linkage mechanism is constituted by a support part of the second support part and a second support part parallel to the robot upper arm, the second support part is connected to the first support part in a direction of a pivot point. By providing a gravity balancer for an articulated robot having a balance weight having a predetermined weight attached to a predetermined position of the extended second support portion, the above-mentioned problems of the prior art are solved. .

(Operation) The present invention relates to a third parallel four-bar linkage mechanism of an articulated robot.
The node is extended downward by a predetermined length to overhang, and at this position is uniquely determined by the length of each side of the link mechanism and the length from each pivot point of the link mechanism to the point of gravity acting on each side of the link mechanism. By attaching a weight balance weight, it is possible to easily balance around the joint.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
Reveal FIG. 1 is an explanatory view of the moment force of the present invention.
It In the present invention, it is expressed by equations (9) and (10).
Torque T_θAnd T In order to reduce the
The installation position of the kit W is determined as follows.

That is, the pivot point C '_FourTo the distance lw in Section 3
Balance weight with weight W is installed at the
It At this time, the torque T of the θ axis and the ψ axis_θAnd T Is next
It is expressed as.

T_θ=-(W₁l₁g + W₃l₃g-Wlw + W_Fourl₁) Sinθ… (11) T =-{W₂l₂g + W₃+ W) l₂＋ W_Four(L₂-L_Fourg)} cos
ψ (12) Therefore, regardless of the control angles θ and ψ of the robot, T_θ, T
Position and weight of gravity balancer such that
W to determine₁l₁g + W₃l₃g-Wlw + W_Fourl₁= 0… (13) W₂l₂g + (W₃+ W) l₂＋ W_Four(L₂-L_Fourg) = 0 ... (14) should be solved.

From equation (14), Wl ₂ = -W ₂ l ₂ g-W ₃ l ₂ -W ₄ (l ₂ -l ₄ g) (15) Therefore, W = W ₄ {(l ₄ g / l ₂ ) −1} −W ₃ −W ₂ (l ₂ g / l ₂ ) ... (16) From equation (13), lw = (W ₁ l ₁ g + W ₃ l ₃ g + W ₄ l ₁ ) / W… (17 ) Is obtained. Therefore, from equations (16) and (17), lw = lw = (W ₁ l ₁ g + W ₃ l ₃ g + W ₄ l ₁ ) / [W ₄ {(l ₄ g / l ₂ )-
_{1} -W 3 -W 2 (l} 2 g / l 2)] ... is represented as (18).

That is, equations (16) and (18) are the weight of the balance weight W.
And the installation position lw from the length of each side of the link part and each pivot point
The length to the point of gravity and the gravity acting on each side of the link
It is shown that it is required uniquely. This and
Come, T_θ= T = 0, and the balance around the joint can be perfectly taken.

In the above embodiment, the weight of the balance weight and the installation position were obtained in consideration of the gravity acting on each arm, but it is possible to obtain a perfect balance with the load such as the workpiece or gun handled by the robot attached. It is also possible to determine the weight and mounting position of the balance weight. In this case, the weight of the balance weight and the mounting position are adjusted according to the weight of the work and the gun.

Further, the present invention can be applied to the configuration so that the perfect balance can be obtained even when the perfect balance cannot be obtained as a result of a mechanical constraint or a design constraint of the robot.

(Effects of the Invention) As described above, according to the present invention, in the articulated robot that configures the parallel four-bar link mechanism, the length of each side of the link portion and each link portion from each pivot point of the link portion The weight up to the point of gravity and the gravity acting on each link are used to uniquely determine the weight and mounting position of the balance weight, and the balance around the joints can be easily obtained. It is possible to provide a gravity balancer for an articulated robot that can perform accurate control regardless of the above.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a moment force using the gravity balancer of the present invention, FIGS. 2 and 3 are perspective views showing an articulated robot, and FIG. 4 is a side view of the robot shown in FIG. , Fifth
FIG. 6 is an explanatory view schematically showing the principle of the present invention. a: fixed base, b: traveling platform, c: robot body, d ...
Robot upper arm, e ... Robot forearm, f ... First wrist base,
g ... second wrist base, h ... wrist tip, i ... extension, j ...
1st support part, k ... 2nd support part.

Claims (2)

[Claims] 1. A robot upper arm having a tail end swingably mounted on a robot base, and a robot upper arm pivotably movably attached to an upper end of the robot upper arm and a robot upper arm formed behind a pivot point of the robot upper arm. In the articulated robot in which a parallel four-bar linkage mechanism is configured by the extended extension, the first support parallel to the extension, and the second support parallel to the robot upper arm, the second support A gravity balancer for an articulated robot, characterized in that the part is extended from the direction of the pivot point with the first support part, and a balance weight having a predetermined weight is attached to a predetermined position of the extended second support part. 2. The weight and position of the balance weight are
The selection is made according to the length of each side that constitutes the parallel four-bar link mechanism, the length from the pivot point of each side of the parallel link to the gravity action point of each link, and the gravity acting on each side of the link. A gravity balancer for an articulated robot according to claim 1.