JPH0829517B2 - Robot collision avoidance control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for avoiding collision with an obstacle when operating a robot.

[Background of the Invention] As a method for controlling a robot so that it does not collide with an obstacle, an Australian computer journal is available.
Growing Polyhedral Obstacles for Planning Collis, August 1983, Volume 3, No. 15 (Vol.15.No.3)
ion-Free Paths) are known. In this method, when the position of the obstacle and the trajectory of the robot are known, it is determined whether or not the trajectory overlaps the obstacle, and a trajectory that does not overlap the obstacle is newly calculated. This method
There is an inconvenience that it cannot be applied unless the robot trajectory is known.

A force feedback control method is also known for preventing the collision of the robot. FIG. 10 is an explanatory view of a known example of the above-mentioned force feedback back control. In the control by this method, the operator 4 uses a force sensor 3 mounted between the robot arm 1 and the robot hand 2 and a control algorithm including processing from the force sensor, and the operator 4 exerts a force (translation force) on the robot hand. And a rotational force), the hand translates and rotates accordingly.

By this control method, when the operator applies a force to the hand of the robot, the robot can be moved at a speed according to the force, and as a method for making the robot hand take an arbitrary position and posture. It is useful. However, this method cannot automatically avoid the collision between the robot and the obstacle. By applying this method, it is possible to automatically control the direction to change the direction instantaneously when a collision occurs, but the impact load of the collision is received by the robot hand, so that safety is also unfavorable.

FIG. 11 is an explanatory diagram showing an example of a conventional collision avoidance control different from the above.

The orbit to be taken by the robot is given a starting point and an ending point in advance by play back, offline, etc., and the middle thereof is generally calculated by calculation.

Therefore, if there is no obstacle on the orbit, there is no problem, but if there is an obstacle, it is the current situation that it is not possible to check in advance whether or not it collides with the obstacle except the start point and the end point. .

Some have proposed a method in which the robot is equipped with an on / off sensor, a force sensor, etc. to detect a collision with an obstacle and make a sudden stop. However, the impact load or sudden stop may affect the robot. Considering it, it is not a desirable method, and there are practical problems.

[Object of the Invention]

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to, when an obstacle is present on the orbit of a robot, without making a sudden change such as a sudden stop or a large orbit change. It is to provide a control method for a robot that smoothly avoids an obstacle, and returns to the original trajectory again after avoiding enough, and is applied when the position of the obstacle is known. The avoidance control can be automatically performed without the need to specify the trajectory in advance. The present invention is
It can also be applied to a robot equipped with a force feedback control function shown in FIG.

[Outline of Invention]

In order to achieve the above object, the control method of the present invention provides a certain area outside the obstacle when the position of the obstacle is known so as to wrap the obstacle. When the robot enters this area, a collision avoidance speed command, which is the vector sum of the predetermined repulsion speed command and the speed command given to the robot, is calculated, and based on this collision avoidance speed command. And activate the robot. In this way, the software allows the robot to avoid obstacles.

Example of Invention

Next, examples of the method of the present invention will be described. FIG. 2 is a perspective view of the robot device used in this embodiment. This robot is a 6-DOF joint type and defines a base coordinate system (B system) fixed to the pedestal of the robot and a hand coordinate system (H system) fixed to the hand of the robot.

Next, a fixed auxiliary coordinate system (A system) is set in the H system. Also, an RH system that represents the equilibrium position and posture (spring element) of the H system,
Define the RA system that represents that of the A system.

FIG. 1 is an explanatory diagram illustrating the vicinity of an obstacle 5 to which the present embodiment is applied. A region 6 is provided around the obstacle 5 so as to surround the obstacle 5 with a certain thickness.

Conventionally, when the straight track 7 overlaps with an obstacle, the robot collides with the obstacle as it is. However, in the present invention, when the robot enters the area 6, the velocity in the direction of avoiding the collision is added, and as in the case of the trajectory 8, as a result, the collision is controlled as follows.

When the obstacle 5 is a rectangular parallelepiped as shown in FIG. 3, a region 6 having a thickness 2a is set around it as shown in FIG.

The arrow 7 indicates the robot path before collision avoidance control, and the movement of the robot along the arrow 7 (the originally designated speed) is indicated by ▲ ▼ (tr of the safex is trajec.
is an abbreviation for tory).

When the robot hand progresses at the speed ▲ ▼ along the arrow 7, when the robot hand enters the area 6, the speed ▲ ▼ described in detail later is added, and the resultant force is And draw a gentle curve like the orbit 8 and obstruct the obstacle 5.
To avoid. (Suffix rep is short for repulsion).

FIG. 5 is an explanatory diagram of a method of setting the speed ▲ ▼ (the repulsive force applied in the direction of pushing back the robot when it enters the area 6).

The direction of the speed ▲ ▼ is a direction away from the obstacle 5 as indicated by a large number of arrows v _{1 to} v ₁₂ shown in FIG.

First, determine one point on the robot hand. This point will be referred to as the point where the robot is located in the future, and control will be performed thereafter so that this point does not overlap the obstacle. This point is the origin of the A system. Next, the arrows v _{1 to} v ₁₂ passing through this point are the regions 6
The point that intersects the outer surface of is the origin of the RA system. The posture of RA system is the same as that of A system.

The size of ▲ ▼ is proportional to the distance Δx between the origins of the A system and the RA system.

The ▼ determined in this way is added to the ▼ as shown in FIG. 4, and a new command speed is calculated for each sampling time. By this, the sixth
As shown in the figure, the robot moves so that the origin of the A system advances along the trajectory 8 (that is, avoiding an obstacle).

Also, Thus, when the robot moves like the orbit 8, the origin of the RA system moves as shown in FIG.

Next, an embodiment different from the above will be described with reference to FIG.

In the previous example, the A-system origin is set at one point on the robot hand, but the A-system origin can be set at a point outside the robot hand, if necessary. In this case, the origin of the A system may be an arbitrary point other than the hand of the robot,
It may be a hollow point. However, even a hollow point has a certain relationship with the robot hand. Further, it is not necessary to make one point, and a plurality of points may be set to A according to the situation, and in this case, A ₁ system origin, A ₂ system origin, ..., _An system origin.

In this case, therefore, the orbits 7 and 8 in FIG.
And 1 of 8 and 2 of orbit 7 and 2 of 8 ..., Orbit 7 n and 8 n.

Further, in the above-mentioned embodiment, the RA system and the A system have the same attitude, but this is a case where the attitude when the region 6 is intruded is maintained as it is.
You may change the posture with the system. In Figure 5, ▲
The arrows v _{1 to} v ₁₂ that determine the direction of ▼ are directed to the left on the left side of the obstacle, to the left below the lower side, and to the lower left corner at the lower left. However, when the original trajectory arrow 7 is directed almost rightward as shown in the figure, all the arrows that determine the direction of ▲ ▼ can be set leftward. In short, these arrows (▲
Good results can be obtained by setting the (direction)) substantially in the opposite direction to the originally given trajectory arrow 7 and away from the obstacle 5.

As shown in FIG. 7, when the obstacle 5 has a three-dimensional shape, the direction of ▲ ▼ described above is changed as shown by arrows v ₁₀₁ , v ₁₀₂ , v _103, ... V _n in FIG. It can also be set.

If the obstacle is represented as a sphere other than a rectangular parallelepiped, ▲
The direction of ▼ may be set so as to face outward from the center of the sphere.

Furthermore, if obstacles are indicated by a combination of cuboids and spheres, it is possible to handle a wider variety of obstacles, and on the other hand, the calculation becomes more complicated. You can apply the person.

The method of determining the directions of the arrows v ₁ , v _{2 to} v ₁₂ shown in FIG. 5 will be described in more detail with reference to FIG.

As shown in the figure, the area on the paper is blocked.
Classified into, A system origin _{(x a, y a, z} a) , each based on whether located one in each of these blocks ▲ ▼ direction to define as follows.

In the case of a block (x _a a, and y _a a), the robot hand cannot be located inside the obstacle, so the block is excluded from consideration.

When the block (-ax _a <a, and y _a a), the equation of the straight line showing the direction of ▲ ▼ is When the block (x _a a, and -ay _a <a), the equation of the straight line showing the direction of ▲ ▼ is Block (| x _a | a, and | y _a | a, where (x _a =
a and y _a = a) is excluded), the equation of the straight line showing the direction of ▲ ▼ is (Refer to FIG. 2) The angle of each joint is measured from the signal of the robot encoder, and from this value and the length of each part of the robot, the position, posture, etc. of the H system (robot hand),
(,,) is obtained.

Represents the relationship between H system and A system A system can be obtained more.

Further, in the present invention, the RA system is determined from FIGS.
Then, the position / orientation deviation of A system and RA system Is found.

In the present embodiment, the attitude deviation is not considered (that is, the attitude of the RA system is the same as that of the A system), so θ
= 0.

Therefore, Δ in the A system (deviation of the position and orientation between the A system and the R system) is Further, in the above-mentioned embodiment, the case where ▲ ▼ is determined only by the deviation ▲ ▼ between the A system and the RA system has been described, but a force sensor is added if necessary, and the force applied to the robot hand ( It is also possible to control the hand force applied by the operator and the force received by colliding with an obstacle) in addition to the determinants of ▲ ▼.

 In this case, the force applied to the force sensor is
Detected as ▼ and converted to ▲ ▼ in the hand system
Be done.

Convert the value after compensating for its own weight to ▲ ▼.

Using Δx, ▲ thus obtained, the command speed ▲ ▼ in the A system is calculated.

In this embodiment, ▲ ▼ = 0.

〔The invention's effect〕

As described in detail above, according to the control method of the present invention, for an obstacle existing within the operating range of the multi-degree-of-freedom robot, a region surrounding the obstacle is set, and the robot enters the set region. When a collision occurs, a means for issuing a collision avoidance speed command for avoiding a collision with an obstacle is provided, and the robot is operated based on the above collision avoidance speed command so that the robot does not suddenly change its speed. By avoiding the collision of the robot, it is possible to automatically perform the collision avoidance control without having to specify the trajectory of the robot hand in advance, and moreover, the avoidance operation is smoothly performed without causing a rapid speed change. It has a practical effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of control of one example of the present invention, and FIG.
The figure is a perspective view of a robot used in one embodiment of the method of the present invention,
3 to 8 are explanatory views of an embodiment of a collision avoidance control method of the present invention, FIG. 9 is a block diagram of control, and FIG. 10 is an explanatory view of a control method using a conventional force sensor. FIG. 11 is an explanatory diagram of the relationship between the obstacle and the trajectory. 1 ... Robot's arm, 2 ... Robot's hand, 3
...... Force sensor, 5 ...... Obstacle, 6 ...... Area set to avoid collision, 7 ...... Orbit originally given to the robot, 8 ...... Collision avoidance controlled trajectory.

Front page continuation (72) Inventor, Shinoyuki Sakagami, 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Pref., Institute of Industrial Science, Hitachi, Ltd. (56) Reference JP-A-58-158712 (JP, A) JP-A-58-158712 53-11291 (JP, A) JP 58-54956 (JP, B2)

Claims (2)

[Claims] 1. For an obstacle existing in the operating range of a multi-degree-of-freedom robot, a region for wrapping the obstacle is set, and the region is assumed on the assumption that the robot has entered the set region in advance. At each point in the
And, the repulsion speed command in the direction away from the obstacle is set in advance, and when the robot actually enters the setting area, the vector of the speed command given to the robot and the repulsion speed command A feature is that a sum of collision avoidance speed commands is calculated, and the robot in the set area is operated by the collision avoidance speed command to avoid collision with an obstacle without causing a rapid change in speed of the robot. Collision avoidance control method for robots. 2. The robot, when a force is applied to the robot, adds the point at which the robot was located at the time of receiving the force while being constrained as a spring restoring point. Patented that it moves according to the magnitude and direction of the applied force, and when the force applied to the robot disappears, it gives a speed command to return to the restoring point of the spring. The collision avoidance control method for a robot according to claim 1.