JP7489219B2 - Path generation device and machine tool - Google Patents

Description

The present invention relates to a path generation device for a robot when the operating range of the robot extends into the machining chamber of the machine tool, and a machine tool equipped with a path generation device.

In recent years, as the demand for automating production processes has increased, robots that can be installed inside the machining chambers of machine tools have been proposed.

The robot installed inside the machining chamber can supply and remove workpieces in a small space. Also, because it is inside the machining chamber, it is possible to clean the inside of the chamber using coolant and air.

In addition, since it is installed in the machining chamber as one of the machine tool units during assembly, the calibration process required at the user's site for typical robot cells is simplified, reducing the cost of setting up the system.

However, the robot installed in the machining chamber operates in the same machining chamber as the moving parts of the machine tool, such as the tool rest, headstock, tailstock, and front door, and the tools and jigs are changed each time machining is performed, which creates the problem that the environment in which the robot operates is different from the environment in which the robot program was created.

Therefore, for robots that operate in environments that change frequently as described above, a control device that can use a simulator to automatically plan, generate, and move a path between a start point and a goal point while avoiding obstacles may be required. By automatically planning a path, the robot can move without interference even if the environment during operation is slightly different.

However, if the environment is significantly different from the time of teaching, the robot movement path may not be found, resulting in an error and causing the machining cycle, including the entire machine tool, to stop.

In Patent Document 1, in a system in which multiple robots operate sequentially, interference calculations are performed on the robot's path, and if a robot interferes with another robot on the path, a means is provided for causing the interfering robot to retreat. However, the path along which the robot moves in Patent Document 1 is not an automatically planned path.

Japanese Patent Application Laid-Open No. 7-136975

When the control device automatically plans the robot's path, multiple paths from the start point to the target point are possible, so if the path planning fails, it is not easy to determine which object in the processing chamber should be removed. Therefore, the method of Patent Document 1 cannot be used to operate the robot.

In addition, when the robot's path cannot be planned and the program stops, the current system does not notify the operator of the cause, so the operator must either analyze the program contents and resolve the problem, or return the machine tool to the state it was in at the time of teaching.

The present invention was made in consideration of the above circumstances, and its purpose is to estimate the cause of failure in automatic path planning for a robot in a machining chamber, notify the operator, and, if possible, automatically move the moving parts of the machine tool away so that the robot can continue operating.

The path generation device disclosed in this specification is a path generation device for a robot having an operating range that extends to the inside of a machining chamber of a machine tool, and is characterized by comprising: a robot path planning means for generating a path plan for the robot based on preset object position conditions; an interference simulator for virtually determining whether or not the object interferes with the robot based on the object position conditions and the path plan; a plan failure factor estimation means for judging the success or failure of the path plan based on the judgment result of the interference simulator, and for estimating the failure factor and an interfering object that is an object that interferes with the robot if the path plan fails; and a notification means for outputting the failure factor and the interfering object estimated by the plan failure factor estimation means to an operator or an external device if the path plan fails.

In this case, the plan failure cause estimation means may determine whether the failure cause is interference at the starting point of the robot's movement, the target point of the robot's movement being outside the robot's range of motion, interference at the target point, or interference between the starting point and the target point.

In addition, if the robot interferes with one or more moving parts of the machine tool, the position condition may be changed to a condition in which the one or more moving parts are retracted to a specified retract position, and then the path plan may be regenerated and the success or failure of the path plan may be re-determined.

In this case, if the robot interferes with two or more movable parts, the regeneration of the path plan and the re-determination of the success or failure of the path plan are repeatedly executed while increasing the number of movable parts to be evacuated under the position conditions by one at a time until the path plan is successful, and the plan failure cause estimation means may estimate the movable parts to be evacuated based on the position conditions when the path plan is successful.

In this case, the order of retraction of two or more of the movable parts under the position condition may be determined based on the distance between the movable parts and a straight line passing through the start point and the target point of the robot's movement.

The machine tool disclosed in this specification is characterized in that it includes the above-mentioned path generation device and a message display means for displaying a message indicating the cause of failure output by the notification means when the path plan fails.

In this case, the machine tool may further include a machine tool control means for actually retracting the movable part in accordance with the positional conditions when the path planning is successful, and a robot control means for operating the robot in accordance with the planned path.

The machine tool control means may also return the movable part to the state before the robot was retracted after the robot has operated according to the planned path.

According to the path generation device disclosed in this specification, when a path plan for a robot operating inside the machining chamber of a machine tool fails, the cause of the failure is identified. Furthermore, when the robot interferes with one or more moving parts of the machine tool, the conditions are changed to one in which the one or more moving parts are retracted to a specified retract position, and the path plan is regenerated and the success or failure of the path plan is reassessed, thereby reducing the operator's work costs.

The machine tool disclosed in this specification is equipped with a message display means for displaying the estimated cause of failure in path generation on a screen, allowing the operator to easily recognize the cause of the failure. Furthermore, when machine tool control means and robot control means are provided, the moving parts of the machine tool are automatically retracted, allowing the robot to continue operating. As a result, it becomes possible to create a machining program without considering the contents of the robot program, reducing the operator's work costs.

1 is a block diagram illustrating a configuration example of a route generating device according to a first embodiment. FIG. 11 is a block diagram illustrating a configuration example of a route generating device according to a second embodiment. FIG. 13 is a block diagram illustrating a configuration example of a route generating device according to a third embodiment. 1 is a flowchart illustrating a process according to a first embodiment. 13 is a flowchart illustrating a process according to a second embodiment. 13 is a flowchart illustrating a process according to a third embodiment.

First, we will discuss cases where the route planning handled by this device fails.

The first case is when the target point is not within the robot's range of motion. This occurs when the robot's arm is fully extended or when the target point cannot be reached due to joint angle restrictions.

The second case is when the robot interferes with an object in the environment when in the robot pose at the target point.

The third case is when the robot can adopt collision-free poses at the start and end of the movement, but collisions cannot be avoided along either path.

The fourth case is when interference has already occurred at the starting point of the robot's movement and the robot cannot move. This can occur, for example, during the next robot movement if you forget to program a retreat movement immediately after gripping a workpiece.

The above four cases are covered in this example.

Next, an embodiment of the control device according to the present invention will be described with reference to the drawings. The control device is, physically, for example, a computer having a processor and a memory. This "computer" also includes a microcontroller in which a computer system is incorporated into a single integrated circuit. The processor refers to a processor in a broad sense, and includes a general-purpose processor (e.g., CPU: Central Processing Unit, etc.) and a dedicated processor (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.). The memory may include at least one of a semiconductor memory (e.g., RAM, ROM, solid state drive, etc.) and a magnetic disk (e.g., hard disk drive, etc.). The control device may also be composed of multiple physically separated computers. The control device may also have a communication I/F for wired or wireless communication with other external electronic devices. Figure 1 is a diagram illustrating the functional configuration of a control device in a first embodiment of the present invention. Each component of Figure 1 will be described in detail below.

The interference simulator 3 simulates the state of robots, machine tools, jigs, and peripheral devices using 3D objects (hereinafter, objects).

Moreover, the interference simulator 3 determines whether or not the objects will interfere with each other in any given state by setting for each object whether or not to perform interference calculation.
Furthermore, each object has information on whether it is a movable part, and if so, where the retraction position is, and whether it is okay to retract automatically. Information on the position and size of each object used by the interference simulator 3 is stored in memory as position conditions.

The robot path planning means 4 is a means for automatically generating the robot's movement path from the starting point to the target point using the state (i.e., positional conditions) of the interference simulator 3 and the inverse kinematics calculation of the robot.

The state storage means 1 is a means for storing the state of the interference simulator 3 at a certain point in time. The state of the interference simulator 3 can be set to the state stored in the state storage means 1.

The planning failure factor estimation means 2 is a means for estimating the failure factors of the robot path planning based on the results of the interference simulator 3 and the robot path planning means 4.

The notification means 5 is a means for notifying an external device, etc. of the failure cause of the robot's path planning based on the estimation by the planning failure cause estimation means 2, or for transmitting the generated path if the path planning is successful.

Figure 4 is a flowchart explaining the processing of the first embodiment of the present invention. The embodiment will be explained below based on Figure 4.

First, the robot path planning means 4 calculates the posture of the robot at the start point of the robot's movement (S10). If the calculation determines that the robot will interfere with another object at the start point (No in S12), the notification means 5 notifies the robot that it will interfere at the start point and the name of the interfering object (S14).

Although not shown in the flowchart, if the robot is outside the operating area at the starting point, a notification to that effect may be sent.

Next, the robot path planning means 4 performs inverse motion calculation at the target point (S16). If the calculation result indicates that the target point is outside the robot's motion range (No in S18), the notification means 5 notifies the robot that the target point is outside the robot's motion range (S20).

Alternatively, if the inverse kinematics calculation results in an object interfering with the robot at the target point (Yes in S22) and all of these interfering objects are movable parts (Yes in S24), the interfering objects are moved to a pre-set evacuation position on the interference simulator (S28), and the inverse kinematics calculation is performed again (S16).

If the inverse kinematics calculation above determines that the robot will interfere again (Yes in S26), the name of the interfering object is notified, and a notification is given that interference may occur even if the object is moved away (S32).

On the other hand, if the inverse kinematics calculation shows that the objects with which the robot will interfere at the target point include an object that is not a moving part of the machine tool (No in S24), the name of the interfering object is immediately notified (S30).

If the robot can assume a position that does not interfere with the start point and the target point (No in S22), path planning is carried out (S34 to S52).

Here, we define success and failure of path planning. A successful path planning is when the robot finds a collision-free path connecting the start point and the destination point. A failed path planning is when the path planning is not successful.

If an algorithm loops infinitely until a route is found, and a failure is defined as a set number of iterations or a timeout, then the path planning algorithm will always ultimately take one of two states: failure or success. Therefore, path planning only considers success or failure.

If the path planning fails even though the robot can assume a posture at the start point and the target point that does not interfere with other objects (Yes in S42), the moving parts are ordered (S46). The ordered machine tool moving part objects are evacuated in order on the interference simulator, and path planning is performed each time (S50, S52, S40).

There are various possible methods for ordering the moving parts, but in this embodiment, a distance d is defined between the pair of start point and target point and the moving part of the machine tool, and the objects are ordered in ascending order of distance d.

For example, when the target point is x _e , the starting point is x _b , and the center of gravity of an object is x _g in the ^R3 space, the distance d can be defined as follows:

Here, the symbols <.,.> are the dot product, and ||.|| is the dot product norm. The distance d is equal to the length of a perpendicular line drawn from the center of gravity of the object to the line passing through the start point and the target point. By defining the distance d in this way, it is possible to evacuate objects in order starting from those closest to the line connecting the start point and the target point.

The distance d is not limited to the distance from the center of gravity, but may be, for example, the minimum distance from the object surface.

If there are two or more objects with the same distance d, then the objects with the same distance d can be sorted in lexicographical order using their object names.

If the moving parts are evacuated on the simulator and the path planning is successful (No in S42, Yes in S54), a notification of the evacuation of the moving parts is sent (S56).

If the route planning fails even though all moving parts have been evacuated (No in S48), a notification is given that the route cannot be found (S58).

If the moving parts can take two states, a retracted state and a non-retracted state (current state), the combinations of the states of the n machine tool moving parts will be 2 ⁿ , which will result in a very large number of trials. Therefore, by considering only cases in which the ordered machine tool moving part objects are sequentially put into the retracted state, the number of attempts for the path planning can be limited to a maximum of n times.

When the first embodiment is executed online, the program may be paused when the cause of failure is estimated, or may be terminated with an alarm.

Figure 2 is a diagram illustrating the configuration of a control device in a second embodiment of the present invention. Below, we will explain in detail the components of the second embodiment that differ from the first embodiment.

The message display means 6 is a means for displaying the cause of failure notified by the path generation device 10 described in the first embodiment on the screen of an NC device, etc.

Figure 5 is a flowchart explaining the second embodiment. Compared to the flowchart for the first embodiment shown in Figure 4, only the differences will be explained.

The path generating device 10 is the device described in the first embodiment. In FIG. 5, in step S70, the path generating device 10 generates a path and estimates the cause of failure, specifically, the flow shown in FIG. 4 is executed. If the path planning for the robot is successful in the initial state in which the path planning is executed according to the notification from the path generating device 10 (Yes in S72), the message display means 6 is used to display on the screen of the NC device or the like that the path planning was successful (S74). Also, if the path planning fails (No in S72), the cause of failure is displayed on the screen based on the notification from the path generating device 10 (S76).

Figure 3 is a diagram illustrating the configuration of a control device in a third embodiment of the present invention. Below, we will explain in detail the components of the third embodiment that differ from the second embodiment.

The machine tool control means 7 is a means for retracting the moving parts of the machine tool based on the estimations of the path generation device 10.

The robot control means 8 is a means for actually operating the robot if the robot path planning is successful.

Fig. 6 is a flowchart for explaining the processing of the third embodiment. Compared with the flowchart in the second embodiment shown in Fig. 5, only the differences will be explained . In the third embodiment, first, the path generation device 10 generates a path and estimates the cause of failure, specifically, the flow shown in Fig. 4 is executed (S80). If the path generation is successful (Yes in S82), it is confirmed whether or not the evacuation target has been notified (S84). If the confirmation result shows that the evacuation target has been notified (Yes in S54 in Fig. 4, Yes in S84 in Fig. 6), it is confirmed whether the movable part that has been evacuated on the simulator is set to be automatically evacuated (S86).

If the movable parts that have been retracted on all simulators are set to be automatically retractable (Yes in S86), the movable parts are automatically retracted (S88) and the robot operation is performed (S90).

If any of the moving parts that have been evacuated on the simulator are not set to be automatically evacuated (No in S86), the program is paused and the moving part that should be evacuated is displayed on the screen as the cause of failure (S92). Also, if path generation fails (No in S82), the program is paused and the cause of failure is displayed on the screen (S92).

According to the above embodiment, many of the causes of failure in path planning are identified and the operator is notified of the causes, and the moving parts of the machine tool are automatically retracted so that the robot can continue to operate, thereby reducing the operator's work costs.

In the third embodiment, the automatically retracted moving parts of the machine tool are not returned to their original state, but the retracted moving parts of the machine tool may be returned to their original positions after the robot has operated, based on the state stored in the state storage means 1.

REFERENCE SIGNS LIST 1 Status storage means, 2 Plan failure cause estimating means, 3 Interference simulator, 4 Robot path planning means, 5 Notification means, 6 Message display means, 7 Machine tool control means, 8 Robot control means, 10 Path generating device.

Claims (8)

A path generation device for a robot having an operating range extending to a machining chamber of a machine tool,
a robot path planning means for generating a path plan for the robot based on a preset object position condition;
an interference simulator that virtually determines whether or not there is interference between the object and the robot based on a position condition of the object and the path plan;
a plan failure cause estimating means for judging whether the path plan has been successful or not based on a judgment result by the interference simulator, and for estimating a cause of the failure and an interfering object that is an object interfering with the robot if the path plan has failed;
a notification means for outputting the cause of failure and the interfering object estimated by the plan failure cause estimation means to an operator or an external device when the path planning fails;
A route generation device comprising: The route generating device according to claim 1 ,
the plan failure cause estimating means judges whether the failure cause is interference at a start point of the movement of the robot, a target point of the movement of the robot being outside the movable range of the robot, interference at the target point, or interference between the start point and the target point;
A route generation device comprising: 3. The route generating device according to claim 1,
When the robot interferes with one or more movable parts of the machine tool, the position condition is changed to a condition in which the one or more movable parts are retreated to a specified retreat position, and then the path plan is regenerated and the success or failure of the path plan is re-determined.
A route generation device comprising: The route generating device according to claim 3,
When the robot interferes with two or more movable parts, the regeneration of the path plan and the re-determination of the success or failure of the path plan are repeatedly performed while increasing the number of the movable parts to be evacuated by one under the position condition until the path plan is successful;
The plan failure cause estimation means estimates a movable part to be evacuated based on the position condition when the path plan is successful.
A route generation device comprising: The route generating device according to claim 4,
A path generation device characterized in that the order of retraction of two or more movable parts under the positional conditions is determined based on the distance between the movable parts and a straight line passing through the starting point and target point of the robot's movement. A route generating device according to claim 3 or 4 ;
a message display means for displaying a message indicating a cause of failure output by the notification means when the route planning fails;
A machine tool comprising: 7. The machine tool according to claim 6,
a machine tool control means for realistically retracting the movable part in accordance with the position condition when the path planning is successful;
A robot control means for moving the robot according to a planned path;
A machine tool comprising: 8. The machine tool according to claim 7,
The machine tool, characterized in that the machine tool control means returns the movable part to a state before the robot was retracted after the robot operated according to a planned path.

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