JP3373351B2 - Articulated robot - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an articulated robot, and more particularly to a parallel link type vertical articulated robot.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing a conventional articulated robot, in which 1 is a base of a robot and 2 is a robot body provided on the base 1. A swing drive is performed by a partial drive source (not shown).
Reference numeral 3 denotes a first rotation shaft pivotally attached to the robot body 2, 4 denotes a first arm, and the lower end of the first arm 4 is fixed to the first rotation shaft 3 to make a first rotation. It is rotated about the first rotation shaft 3 by a shaft drive source (not shown). Reference numeral 5 is a second rotating shaft pivotally attached to the first arm 4, 6 is a second arm, and the second arm 6 is fixed to the second rotating shaft 5 to drive the second rotating shaft. It is rotated about the second rotation shaft 5 by a source (not shown). Reference numeral 7 denotes a rear end node of the second arm, which is a portion where the second arm 6 is extended rearward from the second rotary shaft 5 (the side on which the robot works is the front). 8 is a lower node whose one end is rotatably connected about the first rotating shaft 3 and the other end is rotatably connected to the rear node 9, and 9 is parallel to the first arm 4, This is a rear node that connects the end of the second arm rear end node 7 and the end of the lower node 8. Here, the first arm 4, the second arm rear end joint 7, the lower joint 8, and the rear joint 9 form a parallel four-joint link. Reference numeral 10 is a weight provided at the end of the lower joint 8 on the rear joint 9 mounting side. The articulated robot shown in FIG. 10 is referred to as Conventional Example 1.

Next, the operation will be described. The robot uses a robot body drive source, a first rotary axis drive source, and a second rotary axis drive source, respectively, to form a robot body 2 and a first arm 4 respectively.
When the work is performed by rotating the second arm 6 and the second arm 6, the lower joint 8 tries to lower the lower joint 8 due to the mass of the weight 10, the lower joint 8 pulls the rear joint 9 downward, and the rear joint 9 moves to the second joint. Arm rear end node 7
Try to lower. Therefore, with respect to the second rotating shaft 5,
The lower joint 8 serves as a moment arm, and the mass of the weight 10 reduces the load of the second arm 6 due to gravity.

FIG. 11 is a block diagram showing a parallel link type vertical multi-joint type robot disclosed in, for example, Japanese Utility Model Laid-Open No. 1-112682, in which reference numeral 20 denotes the first rotary shaft 3 of the first arm 4. It is a lower end portion of the first arm which is a portion extended further downward, and the end portion is connected to the lower joint 8. Two
Reference numeral 1 denotes a drive source for rotating the second arm at the pivot points of the rear section 9 and the lower section 8, and the mass of the drive source 21 serves as a weight. The parts corresponding to those in FIG. 10 are designated by the same reference numerals, and duplicate description will be omitted. In addition, this is an articulated robot that is an improvement of Conventional Example 1 and is hereinafter referred to as Conventional Example 2.

In the conventional example 1, the weight 10 has the same height as the first rotating shaft 3, but in the conventional example 2, the drive source 21 for rotating the second arm is located below the first rotating shaft 3. Therefore, the gravity load on the second arm 6 can be reduced as in the conventional example 1, and at the same time, with respect to the first rotating shaft 3, the first arm lower end portion 20
Serves as a moment arm, and the load of the first arm 4 due to gravity is reduced by the mass of the drive source 21 for rotating the second arm.

FIG. 12 shows a gravity balancer of an articulated robot disclosed in, for example, Japanese Patent Publication No. 7-16903.
This is also an articulated robot that is an improvement of Conventional Example 1 and is hereinafter referred to as Conventional Example 3. In the figure, C'1 is the pivot point of the first rotary shaft 3, C'2 is the pivot point of the second rotary shaft 5, and C '.
3 corresponds to the connecting point between the rear end portion 7 of the second arm and the rear joint 9, and C'4 corresponds to the connecting point between the lower joint 8 and the rear joint 9. Reference numeral 11 is a rear joint lower end joint extending below the connecting point C'4, and a weight W is attached to the lower end of the rear joint lower joint 11. Therefore, in Conventional Example 3, since the weight W is provided below the first rotation shaft 3 as in Conventional Example 2, it is possible to reduce the gravity load on the second arm 6 as in Conventional Example 2. At the same time, the gravity load of the first arm 4 can be reduced.

Further, in the prior art example 3, the moment force (length of each link, mass, position of the center of gravity) acting on each of the pivot points (and connecting points) C'1 to C'4 is determined. )
From the formula, the formula of the balance of the parallel four-bar links is established, and from this formula, the mass of the weight W and the optimum mounting position (in FIG.
The length of 1 lw) is obtained, and static balance around the joint is easily performed.

FIG. 13 is a block diagram showing a conventional vertical articulated robot using a spring. In the figure, 22 is a spring stretched between the upper part of the robot body 2 and the first arm 4. . Hereinafter, the vertical articulated robot shown in FIG. 13 is referred to as Conventional Example 4.

In Conventional Example 4, when the first arm 4 falls in the front-rear direction, the extended spring 22 pulls the first arm 4,
Since an attempt is made to return to a vertically standing state, the load of gravity on the first rotating shaft 3 which is the rotating shaft of the first arm 4 is reduced. It should be noted that Japanese Patent Application Laid-Open No. 1-11, which discloses a multi-joint type robot that reduces a gravity load using a conventional spring is disclosed.
There is 09087 publication.

[0010]

Since the conventional articulated robot is constructed as described above, in the articulated robots such as the conventional example 1 and the conventional example 2, the first weight is attached by attaching the weight. Although the gravity load of the arm 4 and the second arm 6 is reduced, the mounting position of the weight is not necessarily optimal for reducing the gravity load. Does not take into account the case where the weight is operating (working), the optimum mounting position and mass of the weight are determined from the static equilibrium equation of parallel four-bar links, so the weight of the weight becomes heavy. However, there is a problem in that the moment of inertia of the arm increases due to the mass of the weight, the acceleration torque cannot be large, and the operation time is delayed. Further, in the articulated robot as in Conventional Example 4, there is a problem that the cost is increased by using the spring 22, and the life of the robot is limited by the life of the spring.

The present invention has been made to solve the above problems, and when the weight load is simultaneously used to reduce the gravity load of the first arm and the second arm, the mounting position of the weight is optimized. The purpose is to obtain a multi-joint robot that can be used. Another object of the present invention is to obtain an articulated robot that minimizes a decrease in the angular acceleration of the first arm and the second arm or an increase in the acceleration time when determining the optimum attachment position and mass of the weight. To do.

[0012]

According to a first aspect of the present invention, there is provided a multi-joint type robot comprising a rear joint, a lower joint and a corner of the rear joint.
Degree, the length of the rear node and the lower node and the mass of the weight,
And the angular acceleration of the second rotation axis, the first rotation axis and the second rotation axis.
Rotational shaft torque, first arm, second arm, lower joint
And the gravity acting on the rear and lower nodes
It

In the articulated robot according to the second aspect of the present invention, the angle with respect to the rear joint of the rear joint lower end joint, the length of the rear joint lower joint and the mass of the weight are set to the first rotation axis and the second rotary shaft. The operating time of the rotating shaft, the angular accelerations of the first rotating shaft and the second rotating shaft,
It is determined by the torques of the first rotary shaft and the second rotary shaft, and the gravity acting on the first arm, the second arm, the lower joint, and the rear lower joint.

In the articulated robot according to the third aspect of the present invention, the range of motion in which the robot actually works is limited, and the angle with respect to the rear node of the rear joint lower end joint, the length of the rear joint lower joint and the weight of the rear joint. It determines the mass.

According to a fourth aspect of the present invention, an articulated robot limits the operating range in which the robot actually works, and determines the angle of the rear joint lower joint with respect to the rear joint, the length of the rear joint lower joint, and the weight. It determines the mass.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a block diagram showing a parallel link type vertical articulated robot according to Embodiment 1 of the present invention.
In the figure, reference numeral 1 is a base of the robot, and 2 is a robot body provided on the base 1, which is driven to rotate by a robot body drive source (not shown). Reference numeral 3 denotes a first rotation shaft pivotally attached to the robot body 2, 4 denotes a first arm, and the lower end of the first arm 4 is fixed to the first rotation shaft 3 to make a first rotation. First by a shaft drive source (not shown)
It rotates about the rotation axis 3. Reference numeral 5 is a second rotating shaft pivotally attached to the first arm 4, 6 is a second arm, and the second arm 6 is fixed to the second rotating shaft 5 to drive the second rotating shaft. A source (not shown) rotates about the second rotating shaft 5. Reference numeral 7 denotes a rear end node of the second arm, which is a portion where the second arm 6 is extended rearward from the second rotary shaft 5 (the side on which the robot works is the front). Reference numeral 8 denotes a lower node, one end of which is rotatably connected about the first rotation shaft 3 and the other end is rotatably connected to a rear node 9, and 9 is an end portion of the second arm rear end node 7. This is a rear node that connects the ends of the lower joint 8 and is connected to each end so as to be rotatable and parallel to the first arm 4. Here, the first arm 4, the second arm rear end joint 7, the lower joint 8, and the rear joint 9 form a parallel four-joint link.

Reference numeral 11 denotes a rear joint lower end joint which extends the rear joint 9 on the side opposite to the second arm 6, and extends from the rear joint 9 by a predetermined angle φ and a predetermined length r. Reference numeral 10 is a weight provided at the lower end of the rear joint lower joint 11. Reference numeral 12 is a wrist shaft (grasping means) provided at the front end of the second arm 6 (the side where the robot works is the front).
Uses a parallel link (not shown) attached from the robot body 2 along the first arm 4 and the second arm 6 so as to maintain the horizontal position regardless of the postures of the first arm 4 and the second arm 6. Has become. Reference numeral 13 is a hand (grasping means) provided below the wrist shaft 12 and rotationally driven by a wrist shaft drive source (not shown). The hand 13 is a force of a hand drive source (not shown). By work 14
Is to hold. In addition, the robot body drive source,
The first rotary shaft drive source, the second rotary shaft drive source, and the wrist shaft drive source are composed of a motor and a speed reducer, or an air cylinder, and are installed on the outside (or inside) of the robot. (Not shown).

Next, the operation will be described. FIG. 2 is a schematic diagram for explaining the operation of the parallel link type vertical articulated robot, in which the first arm 4, the second arm 6, the lower joint 8, the rear joint 9, the rear joint lower joint 11, etc. are indicated by lines. It represents. Figure 2
As shown in (a), when the first rotating shaft 3 rotates and the first arm 4 falls forward, the rear joint lower end joint 11 becomes a moment arm with respect to the first rotating shaft 3. Since the mass of the weight 10 tries to raise the first arm 4, the gravity load on the first arm 4 is reduced. At this time, the mass of the weight 10, the predetermined angle φ with respect to the rear joint 9 of the rear joint lower end joint 11, and the predetermined length r are adjusted so that the gravity load is reduced most. Further, as shown in FIG. 2B, when the second rotating shaft 5 rotates and the second arm 6 becomes horizontal, the lower joint 8 is a moment arm with respect to the second rotating shaft 5. Therefore, since the weight of the weight 10 tries to lift the second arm 6, the gravity load on the second arm 6 is reduced. At this time, the mass of the weight 10, the predetermined angle φ with respect to the rear joint 9 of the rear joint lower end joint 11, and the predetermined length r are adjusted so that the gravity load is reduced most.

As described above, according to the first embodiment, when the gravitational load on the first arm 4 and the second arm 6 is simultaneously reduced by using the weight 10, the rear node 9 of the rear node and the lower node 11 of the rear node. By changing the angle φ with respect to and the length r of the rear lower end joint 11 and optimizing the mounting position of the weight 10, the optimum gravity load reduction can be obtained. Further, since the mounting position of the weight 10 is set to have a predetermined angle φ with respect to the rear node 9 of the rear node lower end node 11, the gravity load can be sufficiently reduced without making the mass of the weight 10 too heavy. .

Embodiment 2. In the first embodiment, the weight 10 is attached to the lower end of the rear joint lower joint 11, and the mass of the weight 10, the angle φ of the rear joint lower joint 11 with respect to the rear joint 9, and the length r of the rear joint lower joint 11 are adjusted. By doing so, the gravitational load is reduced, but in the second embodiment, the optimum mass, angle φ, and length r of the weight 10 for reducing the gravitational load are determined. FIG. 3 is a schematic view showing a parallel link type vertical articulated robot according to a second embodiment of the present invention. In the figure, .theta.2 is the angle of the first rotating shaft 3 (angle of the first arm 4 with respect to the vertical axis). ), Θ3 is the angle of the second rotating shaft 5 (the angle of the second arm 6 with respect to the horizontal axis), L1 is the length of the first arm 4, and L2 is
Is the length of the second arm 6, LW is the length of the lower joint 8, r is the length of the rear lower joint 11, and φ is the rear lower joint 11 with respect to the rear joint 9.
, Mc is the mass of the weight 10.

Next, a method for determining the mass mc of the weight 10 and the angle φ of the rear lower joint 11 with respect to the rear joint 9 and the length r of the rear lower joint 11 will be described. First, a method for reducing the gravity load on the first rotating shaft 3 will be described. The torque t2 to be applied to the output shaft of the speed reducer of the first rotary shaft 3 is approximately given by the following equation. The right side is positive in the clockwise direction.

[0022]     t2 =-(Iw2 + Ic2) * β2 + mw2 * g * L1           * Sin (θ2) -mc * g * r * Sin (θ2 + φ) (1)

Here, the value of each term is defined as follows.
t2 is the torque to be applied to the reduction gear output shaft of the first rotation shaft 3, β2 is the angular acceleration of the reduction gear output shaft of the first rotation shaft 3,
mw2 is an equivalent mass from the elbow (the second rotation shaft 5) ahead (this equivalent mass is considered to act on the elbow), and g is a gravitational acceleration. Iw2 is the moment of inertia about the first rotary shaft 3 due to the equivalent mass from the elbow to the tip, and Iw2 = mw2 * L1 * L1. Ic2 is the moment of inertia of the weight 10 about the first rotation axis 3, and Ic2 = mc * r * r.

In Conventional Example 3, the optimum mounting position and mass of the weight were determined from the static equilibrium formula of parallel four-bar links, but in the second embodiment, the robot actually operates (work). The optimum mounting position and mass of the weight are determined from the equation of the balance during the operation. Therefore, in Expression 1, not only the torque and the gravity acting on each node, but also the force (angular motion equation) acting by the angular acceleration is taken into consideration ((Iw2 + Ic2) * β2 in Expression 1).

It is assumed that the output tr2 of the speed reducer is added to the left side t2 of the equation (1). Here, tr2 is the maximum allowable torque of the speed reducer of the first rotary shaft 3. If t2 = tr2 is set and the angular acceleration β2 of the first rotary shaft 3 is solved, the following is obtained.

[0026]   β2 = (tr2 + mw2 * g * L1 * Sin (θ2) -mc * g         * R * Sin (θ2 + φ)) / (mw2 * L1 * L1 + mc * r * r)                                                                 (2)

A known value is substituted into the equation (2). Known values are tr2 (maximum allowable torque of the reduction gear), L1 (length of the first arm 4), mw2 (equivalent mass from the elbow to the tip), and g (gravitational acceleration). Here, tr2 is positive in the clockwise direction. The result of substitution is the mass mc of the weight 10 and the rear node lower node 1
1, the length r of 1, the angle φ of the posterior lower node 11 with respect to the posterior segment 9,
And a function β2pls of the angle θ2 of the first rotation shaft 3.

Similarly, a known value is substituted into the above equation (2). Known values are tr2 (maximum allowable torque of the reducer), L1 (length of the first arm 4), mw2 (equivalent mass from the elbow to the tip), g (gravitational acceleration), as in the case of the angular acceleration β2pls.
However, tr2 is counterclockwise and is negative. The substituted result is the mass mc of the weight 10, the length r of the rear joint lower joint 11, the angle φ of the rear joint lower joint 11 with respect to the rear joint 9, and the first
Is a function β2mns of the angle θ2 of the rotation axis 3.

The angular accelerations β2pls and β2mns are integrated over the entire operating range of the robot. The operating range of the robot is from θ2l to θ2u. θ2l is the lower end of the robot motion range, and θ2u is the upper end of the robot motion range. The function obtained in this way is given by
Evaluation functions ea2pls and ea2mns that determine the length r and angle φ of
And The evaluation functions ea2pls and ea2mns are as follows.

[0030]

[Equation 1]

Since the counterclockwise angular acceleration ea2mns is negative and is therefore given a negative sign, the larger the numerical value is, the larger the angular acceleration is in both clockwise and counterclockwise directions. Therefore,
The length r and the angle φ of the rear lower end joint 11 are determined so that the evaluation functions ea2pls and ea2mns become large.

FIG. 4A is an example in which the evaluation function ea2pls is plotted with the length r of the rear lower end node 11 and the angle φ as variables. However, the constants of each part are defined as follows. Maximum torque tr2 ± 3000Nm Length of the first arm L1 1.2m Equivalent function from elbow to mw2 150Kg Operating range of the second axis θ2-45deg ~ 90deg As shown in Fig. 4 (a), the length of the rear end lower joint 11 The evaluation function ea2pls becomes larger as the length r becomes smaller, and the angle φ does not largely affect the evaluation function ea2pls.

FIG. 4B is an example in which the evaluation function ea2mns is plotted with the length r of the rear lower end node 11 and the angle φ as variables. The constants of the respective parts are the same as in the case of FIG. As shown in FIG. 4 (b), the length r of the posterior segment lower segment 11
There is a maximum for the combination of and the angle φ.

Here, as an example of determining the optimum mounting position of the weight 10, for the evaluation function having the smaller angular acceleration, the angular acceleration of the evaluation function is made larger.
That is, the portion where the angular acceleration becomes small is avoided.
In this case, the evaluation function ea2mns (absolute value) is set to be large. Therefore, the maximum point in FIG. 4B is the optimum value of the length r and the angle φ of the rear joint lower joint 11 with respect to the first rotation shaft 3, and r = 0.24 m φ = 60 deg.

Next, a method for reducing the gravity load on the second rotating shaft 5 will be described. The torque t3 to be applied to the output shaft of the speed reducer of the second rotary shaft 5 is approximately given by the following equation.
The clockwise direction is positive.

[0036]     t3 = (Iw3 + Ic3) * β3 + mw3 * g * L2 * Cos (θ3)           -Mc * g * Lw * Cos (θ3) (5)

Here, the value of each term is defined as follows.
t3 is the torque to be applied to the speed reducer output shaft of the second rotary shaft 5, β3 is the angular acceleration of the second rotary shaft speed reducer output shaft, mw3
Is the equivalent mass of the wrist shaft 12 (it is assumed that this equivalent mass is applied to the wrist shaft). Iw3 is the moment of inertia about the second rotation axis 5 due to the equivalent mass of the wrist shaft Iw3 = mw3 * L2 * L2 Ic3 is the moment of inertia about the second rotation axis 5 by the weight 10 Ic3 = mc * Lw * Lw.

In the equation 5, as in the equation 1 (the equation relating to the first rotating shaft 3), it is assumed that the robot is actually operating (working), and from the equation of the balance during this operation, the weight is calculated. 1
The optimum mounting position and mass of 0 are determined. Therefore, equation 5
Considers not only torque and gravity acting on each node, but also force (angular motion equation) acting on angular acceleration ((Iw3 + Ic3) * β3 in Equation 5).

It is assumed that the output tr3 of the speed reducer is added to the left side t3 of the equation (5). Here, tr3 is the maximum allowable torque of the speed reducer of the second rotating shaft 5. If t3 = tr3 is set and the angular acceleration .beta.3 of the second rotary shaft 5 is solved, the following is obtained.

[0040]     β3 = (tr3 + mw3 * g * L2 * Cos (θ3) -mc * g * Lw           * Cos (θ3)) / (mw3 * L2 * L2 + mc * Lw * Lw)                                                                 (6)

A known value is substituted for the angular acceleration β3 in the above equation 6. The known value is tr3 (the maximum allowable torque of the reducer),
L2 (length of second arm 6), Lw (length of lower section 8),
mw3 (equivalent mass of the wrist shaft 12) and g (gravitational acceleration). Here, tr3 is positive in the clockwise direction. The substituted result is a function β3pls of the mass mc of the weight 10.

Similarly, a known value is substituted into the above equation 6. The known values are tr3 (the maximum allowable torque of the reducer), L2 (the length of the second arm 6), Lw (the length of the lower section 8), and mw3 (the equivalent mass of the wrist), similar to the angular acceleration β3pls. , G (gravitational acceleration), but tr3 is positive in the counterclockwise direction. The substituted result is defined as a function β3mns of the mass mc of the weight 10 and the angle θ3 of the second rotation shaft 5.

The angular accelerations β3pls and β3mns are integrated over the entire operation range of the robot. Robot motion range is θ
3 is from θ3l to θ3u. θ3l is the lower end of the robot motion range, and θ3u is the upper end of the robot motion range. The mass m of the weight 10
Assume that evaluation functions ea3pls and ea3mns that determine c. The evaluation functions ea3pls and ea3mns are as follows.

[0044]

[Equation 2]

Since the counterclockwise angular acceleration ea3mns is negative, a negative sign is attached, so that the larger the numerical value is, the larger the angular acceleration is in both clockwise and counterclockwise directions. Therefore,
In order to make the evaluation functions ea3pls and ea3mns large,
The mass mc of the weight 10 is determined.

FIG. 5 is an example in which the evaluation functions ea2pls and ea3mns are plotted with the mass mc of the weight 10 as a variable.
However, the constants of each part are defined as follows. Maximum torque tr3 ± 3000Nm Length of second arm L2 1.2m Equivalent function from elbow to mw3 100Kg Operating range of second axis θ3 -15deg to 90deg Evaluation function ea2pls is weight 10 as shown by the solid line in FIG.
The evaluation function ea2pls is smaller when the mass mc of the is larger. On the other hand, the evaluation function ea3mns has a larger mass mc of the weight 10 as shown by a broken line in FIG.
Grows larger.

Here, as an example of determining the mass mc of the weight 10, the portion where the angular acceleration (absolute value) is small is reduced. Therefore, the clockwise evaluation function ea2pls and the counterclockwise evaluation function ea3mns are superposed, and the intersection of these is the optimum mass. The mass mc of the weight 10 at this time is 40
It will be 0 kg.

If the mass mc of the weight 10 obtained as described above is too large in terms of, for example, mounting dimensions, the larger it is in a practical range, the better. Good.

As described above, according to the second embodiment, assuming that the robot is actually operating (working), the weight 10 of the weight 10 is calculated from the equation of the balance during the operation in consideration of the angular acceleration. Since the optimum mounting positions r and φ and the mass mc are determined, even if the weight 10 is mounted to reduce the gravity load, the first rotating shaft 3 (or the first arm 4) and the second rotating shaft 3 It is possible to obtain the effect of preventing a decrease in the angular acceleration of the armature 5 (or the second arm 6).

Embodiment 3. In the second embodiment, the first
Although the evaluation function is determined from the viewpoint that the angular accelerations of the rotating shaft 3 and the second rotating shaft 5 do not decrease, in the third embodiment, the operation time of the robot is shortened. The evaluation function is decided from the viewpoint. FIG. 6 is a diagram showing a relationship among angular velocities, time and motion angles of a first rotary shaft 3 and a second rotary shaft 5 of a vertical articulated robot according to a third embodiment of the present invention. ta is the acceleration time, td
Is the deceleration time, βa is the (acceleration) angular acceleration, βd is the (deceleration) angular acceleration, and θ is the operating angle. It shows a case where the first rotary shaft 3 and the second rotary shaft 5 of the robot are operating at a small angle by accelerating and decelerating around a certain angle within the motion range. An operation function at this time, that is, a value obtained by integrating the sum of the acceleration time and the deceleration time over the entire operation range of the robot is used as an evaluation function.

As is apparent from FIG. 6, since the maximum velocities (indicated by M in the figure) are equal, the following equation holds.

[0052]     βa * ta = βd * td (9)

Further, the following equation is established using the operating angle θ (area surrounded by a triangle in the figure).

[0054] ^{βa * ta 2/2 + βd} * td 2/2 = θ (10)

From the above equations 9 and 10, the operating time t is

[0056]

[Equation 3]

It becomes Here, with respect to the first rotation axis 3, an evaluation function that shortens the operation time is obtained. The evaluation functions ea2pls and ea2mns (Equation 3 and Equation 4) of the angular acceleration of the first rotation shaft 3 obtained in the above-mentioned Embodiment 2 are substituted into the above Equation 11 to determine the evaluation function eb2 as the following equation. .

[0058]

[Equation 4]

In this equation 12, the coefficient √ (2) and the term of θ are excluded. Also, β2mns is negative, so a negative sign is added to make it positive. In order to shorten the operation time, it is sufficient that the evaluation function eb2 becomes small, and thus the length r and the angle φ of the rear node lower node 11 are determined.

In FIG. 7A, the evaluation function eb2 is represented by
It is a figure which shows an example which plotted length r of 1 and angle (phi) as a variable. Here, the constants of the respective parts are the same as those in the second embodiment. As shown in FIG. 7A, there is a minimum value for a certain combination of the length r and the angle φ of the rear node lower node 11. Therefore, the values of the length r and the angle φ of the rear lower end node 11 at the minimum value are optimum values. The optimum value is r = 0.2 m φ = 8 deg.

Next, with respect to the second rotating shaft 5, an evaluation function that shortens the operation time is obtained. Similarly to the evaluation function eb2 for the first rotation axis 3, the operation time t is given by the equation 11,

[0062]

[Equation 5]

It is The angular acceleration β3p of the second rotary shaft 5 obtained in the above-described second embodiment is calculated by the expression 13 (similar to the expression 11).
By substituting ls and β3mns (formula 7 and formula 8), the evaluation function eb3 is determined as follows.

[0064]

[Equation 6]

In this equation 14, the terms of coefficient √ (2) and θ are excluded. Also, β3mns is negative, so a negative sign is added to make it positive. In order to shorten the operation time, it is sufficient that the evaluation function eb3 becomes small.
The mass mc of is determined.

FIG. 7B is a diagram showing an example in which the evaluation function eb3 is plotted with the mass mc of the weight 10 as a variable.
Here, the constants of the respective parts are the same as those in the second embodiment. As shown in FIG. 7B, there is a minimum value with respect to the mass mc of the weight 10. Therefore, the value of the mass mc of the weight 10 at the minimum value becomes the optimum value. The optimum value is mc = 240 Kg.

As described above, according to the third embodiment, the evaluation function is obtained by using the operating time of the first rotary shaft 3 and the second rotary shaft 5, and the rear node lower end node 11 Since the length r, the angle φ, and the mass mc of the weight 10 are determined, even if the weight 10 is attached to reduce the gravity load, the first rotating shaft 3 (or the first arm 4) and the 2 rotation axis 5
The effect that the operating time of (or the second arm 6) can be shortened is obtained. In the case where the first rotary shaft 3 and the second rotary shaft 5 of the robot reach the upper limit of the angular velocity immediately (the upper limit of the angular velocity is reached by a small angular movement), the second embodiment described above is used. It is possible to reduce the gravity load more efficiently than the method using the angular acceleration shown in.

Fourth Embodiment In the second and third embodiments described above, it is assumed that the robot operates in the entire operating range (θ2l ≦ θ ≦ θ2u, θ3l ≦ θ ≦ θ3u) of the first rotating shaft 3 and the second rotating shaft 5, A value obtained by integrating the angular acceleration or the operation time within this range was used as the evaluation function. However, this evaluation function includes the range where the wrist axis 12 does not reach during the actual work in the range of integration. Therefore, in the fourth embodiment, the evaluation function is obtained by limiting the operation range in which the robot actually works. FIG. 8 is a diagram showing an actual operating range of a vertical articulated robot according to Embodiment 4 of the present invention. Each point in the figure is the first rotation axis 3 of the robot.
And the position of the wrist shaft 12 when the second rotation shaft 5 is moved by 5 degrees within the operating range of each shaft. Further, the portion surrounded by the rectangle shows the movement range in which the robot actually works.

When the robot operates in the entire operating range of the first rotating shaft 3 and the second rotating shaft 5, the range in which the wrist shaft 12 can operate is a crescent-shaped range as shown by the points in the figure. However, the operating range in which the robot actually works is often the part surrounded by the rectangle in the figure. Therefore, the angular acceleration or the operation time is integrated for the part surrounded by the rectangle in the figure, and this value is used as the evaluation function.

The coordinates of a point within the range enclosed by the rectangle in FIG. 8 are (X, Z), and the first rotation axis 3 when the wrist axis 12 reaches this point (X, Z). If the angle between the second rotation axis 5 and the second rotation axis 5 is (θ2, θ3) as shown in FIG. 9, the coordinates (x, z) of the wrist axis 12 are the length L1 of the first arm 4 and the second arm 6 It can be expressed as follows using the length L2 of

[0071]   X = SX + L1 Sin (θ2) + L2 Cos (θ3) + WX (15)   Z = SZ + L1 Cos (θ2) -L2 Sin (θ3) -WZ (16)

However, (Sx, Sz) is the coordinate of the shoulder (first rotation axis 3) of the robot, and (Wx, Wz) is the offset coordinate of the wrist axis 12 of the robot. The above relational expression (Equation 1
5, the equation 16) is used to determine the angles θ2 and θ3 of the first rotary shaft 3 and the second rotary shaft 5 with respect to the coordinates within the range enclosed by the rectangle in the figure, and the above-described Embodiment 2 is used. The evaluation function is obtained in the same manner as in Steps 3 and 3, and the length r and the angle φ of the rear section lower section 11 are
The mass mc of the weight 10 may be optimized. In addition, when giving the coordinates within the range enclosed by the rectangle in the figure, the coordinates of the grid points at regular intervals may be given within this range, and the work is specifically decided and the trajectory of the robot is decided. When it is present, its orbit may be given, or may be given as a random number using the Monte Carlo method.

As described above, according to the fourth embodiment, the evaluation function is obtained only within the motion range in which the robot actually works, and the length r and the angle φ of the rear node lower node 11 are thereby obtained.
Since the mass mc of the weight 10 is determined, the gravity load can be reduced more efficiently.

Although mw2 is simply the equivalent mass from the elbow to the tip and mw3 is simply the equivalent mass of the wrist shaft 12 in the above-described second, third and fourth embodiments, the robot can be used for welding robots, painting robots and the like. Yes, if the hand has a welding gun, paint spray, etc., and the mass of the hand is constant, mw2 is the equivalent mass from the elbow to the mass including the hand, and mw3 is the mass of the hand. Including wrist axis 12
Becomes the equivalent mass of. In addition, when the robot is an assembly robot, a palletizing robot, etc., and there is a case where the robot hand near the hand has a work and there is a case where it does not have a work, proper gravity compensation is provided in both cases. As it works, for example, mw2 is the equivalent mass from the elbow to the end including the half of the work mass, and mw3 is the equivalent mass of the wrist shaft 12 including the half of the work mass.

In the second and third embodiments described above, the angular acceleration over the motion range of the robot or the integrated value of the motion time is used as the evaluation function, but the angular acceleration for the angle given at an appropriate interval is used instead of the integrated value. You may use the sum total (Σ) of operating time.

Although the allowable maximum torque of the speed reducer is used as the torque limit value (maximum value) in the second, third, and fourth embodiments, the maximum torque of the motor may be used in some cases.

[0077]

As described above, according to the first aspect of the present invention, the angle of the rear joint lower joint with respect to the rear joint, the length of the rear joint lower joint,
Of the first rotary shaft and the second rotary shaft.
Angular acceleration, torques of the first rotary shaft and the second rotary shaft, and
And 1st arm, 2nd arm, lower joint and rear joint lower joint
Since it is configured to determine by the gravity to
Angular acceleration assuming that the bot is operating (working)
Optimal mounting of the weight based on the balance equation during operation considering the degree
To determine position and mass, and to reduce gravity load
Even if the weight is attached, the first rotating shaft (or the first arm)
Acceleration of the second rotation axis (or second arm)
Is effective in preventing the decrease of

According to the second aspect of the present invention, the angle of the rear section lower end section with respect to the rear section, the length of the rear section lower end section and the mass of the weight are determined by the first rotating shaft and the second rotating shaft. Operating time, angular accelerations of the first rotation shaft and the second rotation shaft, torques of the first rotation shaft and the second rotation shaft, and the first arm, the second arm,
Since it is configured to be determined by the gravity acting on the lower section and the lower section of the rear section, the evaluation function is obtained using the operating time of each rotation axis, and the length, angle, and mass of the weight of the lower section of the rear section The effect that the operation time of the first rotation shaft (or the first arm) and the second rotation shaft (or the second arm) can be shortened even if the weight is attached to reduce the gravity load. There is. Further, when the rotation axis of the robot reaches the upper limit of the angular velocity immediately (when the upper limit of the angular velocity is reached by a small angular motion), the gravity load can be reduced more efficiently than the method using the angular acceleration. effective.

According to the third aspect of the invention, the range of motion in which the robot actually works is limited, and the angle of the rear joint lower joint to the rear joint, the length of the rear joint lower joint and the mass of the weight are determined. Since the robot is configured to do so, the evaluation function is obtained only within the motion range in which the robot actually works, and the length, angle, and mass of the weight of the rear and lower joints are determined by the evaluation function. There is an effect that can be reduced.

According to the invention described in claim 4, the range of motion in which the robot actually works is limited, and the angle of the rear joint lower joint to the rear joint, the length of the rear joint lower joint and the mass of the weight are determined. Since the robot is configured to do so, the evaluation function is obtained only within the motion range in which the robot actually works, and the length, angle, and mass of the weight of the rear and lower joints are determined by the evaluation function. There is an effect that can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a parallel link type vertical articulated robot according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the parallel link type vertical articulated robot according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing a parallel link type vertical articulated robot according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example in which the evaluation functions e2pls and e2mns are plotted with the length r of the rear node and the lower node and the angle φ as variables.

[Fig. 5] Evaluation functions ea2pls, ea3mns are weight mass mc
It is a figure which shows an example which plotted as a variable.

FIG. 6 is a diagram showing a relationship among angular velocities, time and motion angles of a first rotary shaft and a second rotary shaft of a vertical articulated robot according to a third embodiment of the present invention.

FIG. 7 shows the evaluation function eb2 as the angle r and the length r of the lower node of the rear node.
Showing an example in which P is plotted as a variable and an evaluation function e
It is a figure which shows an example which plotted b3 using the mass mc of a weight as a variable.

FIG. 8 is a diagram showing an actual operating range of a vertical articulated robot according to a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a vertical articulated robot according to a fourth embodiment of the present invention.

FIG. 10 is a configuration diagram showing a conventional articulated robot.

FIG. 11 is a configuration diagram showing a parallel link type vertical articulated robot disclosed in Japanese Utility Model Laid-Open No. 1-112682.

FIG. 12 is a diagram showing a gravity balancer of an articulated robot disclosed in Japanese Patent Publication No. 7-16903.

FIG. 13 is a configuration diagram showing a vertical articulated robot using a conventional spring.

[Explanation of symbols]

2 robot body, 3 first rotation axis, 4 first arm, 5 second rotation axis, 6 second arm, 8 lower section, 9
Rear section, 10 weights, 11 rear section lower end section, 12 wrist axis (holding means), 13 hands (holding means), 14 works.

Claims (3)

(57) [Claims] 1. A first rotary shaft rotatably held on a robot body in a vertical plane, and one end of which is locked to the first rotary shaft to rotate around the first rotary shaft. A first arm that rotates in a vertical direction, a second rotation shaft that is rotatably held at the other end of the first arm in a vertical plane, and a gripping means that holds a workpiece at one end. A second arm which is locked to the second rotation shaft and rotates about the second rotation shaft, and one end of which is the first arm.
Of the lower arm, which is rotatable about its rotation axis and is locked to the first rotation axis so as to be parallel to the second arm, and one end of which is supported by the other end of the second arm. , The other end is supported by the other end of the lower joint, and forms a parallel four-joint link with the first arm, the second arm, and the lower joint, and one end holds a predetermined angle with the rear joint. In the articulated robot having a rear joint lower end joint attached to the other end of the rear joint and a heavy sledge attached to the other end of the rear joint lower end joint, the angle with respect to the rear joint of the rear joint lower joint , Above
The length of the lower end node and the mass of the weight are set to the first rotary shaft and the second rotary shaft.
Of the rotation axis of the first rotation axis and the second rotation axis of
Torque and 1st arm, 2nd arm, lower joint and lower joint
Many characterized by being determined by gravity acting on end nodes
Articulated robot. 2. A robot body is rotatably held in a vertical plane.
The held first rotating shaft and one end of which is engaged with the first rotating shaft.
A first arm that is stopped and rotates about the first rotation axis.
And the other end of the first arm is rotatably held in the vertical plane.
Second rotating shaft and gripping means for holding the work at one end
And is locked to the second rotation shaft and has the second rotation.
A second arm that rotates about an axis and one end of the first arm
Is rotatable about the rotation axis of and parallel to the second arm.
So that the lower joint locked to the first rotating shaft and one end
The other end of the second arm is supported while the other end is the lower part.
The first arm and the second arm are supported by the other end of the node.
Posterior segment that forms a parallel four-segment link with
And one end of the rear section to maintain a certain angle with the latter section.
A rear node lower end node attached to the other end of the node and the rear node lower end node
An articulated robot with a weight attached to the other end of
The angle with respect to the rear segment of the rear segment, the lower segment of the rear segment, the length of the lower segment of the rear segment and the mass of the weight,
Operating time of the rotating shaft, angular acceleration of the first rotating shaft and the second rotating shaft, torque of the first rotating shaft and the second rotating shaft, and the first arm, the second arm, An articulated robot characterized by being determined by gravity acting on the lower node and the lower node of the posterior segment. Wherein limiting the operating range of the robot is actually working, the angle with respect to sections of the rear section section bottom, claim 1 or claim, characterized in that the length and mass of the rear section clause bottom Item 2. The articulated robot according to item 2 .