JP7684205B2 - Working device and method for controlling working device - Google Patents

Description

The present invention relates to the configuration of a working device and its control, and in particular to technology that is effective when applied to adjusting the height of a working robot mounted on the working device.

Robots on vertically moving platforms are used to perform assembly, inspection and maintenance tasks in the construction and maintenance sector. Such tasks include, but are not limited to, automated installation of elevator rails, maintenance of building exteriors, fastening interior boards to walls, inspecting dam walls, wiping windows, etc. To perform these tasks, a winder is usually used to move the platform, which then moves the robot vertically to reach the height of the target object that the robot is to handle.

High accuracy height measurements are required when performing high precision tasks or following pre-programmed trajectories based on drawings or 3D schematics of the work environment.

However, typical reeling machines do not provide the millimeter-level accuracy required to avoid under-reaching of the robot, singularities in the robot, or collisions with obstacles, so a different height measurement method is needed.

As background technology in this technical field, for example, there is technology such as that disclosed in Patent Document 1. Patent Document 1 discloses technology that uses a laser distance sensor that is composed of a laser irradiator placed on the ground floor and a laser reflector installed on a movable platform.

Patent Document 2 also discloses a technology that detects scales traced on a vertically stretched piano wire to measure the platform height with high precision.

JP 2020-7095 A Japanese Patent Application Publication No. 4-55276

In Patent Document 1, in addition to the increased cost of adding a laser distance sensor, the laser irradiator must be placed on the lowest floor and aligned with the laser reflector before the robot system can be operated, increasing the lead time for preparing the system for operation.

Furthermore, the accuracy of the laser measurements decreases with platform height, limiting the maximum height at which the robot can be operated.

In addition to increasing the cost of the robot system, Patent Document 2 requires the use of specially calibrated piano wire, making the system more complicated.

Furthermore, when piano wire stretches, it undergoes plastic deformation, reducing the accuracy of height measurement. Also, because piano wire is thin, it is difficult to measure the scale.

The object of the present invention is to provide a work device in which a work robot is mounted on a vertically moving platform, and which has a relatively simple and inexpensive configuration and allows for highly accurate height adjustment of the work robot, and a control method thereof.

In order to solve the above problems, the present invention provides a work robot that performs work on a target object, a platform on which the work robot is mounted, a height adjustment device that adjusts the height of the platform, a detection device that detects the target object, a judgment device that determines whether the position of the target object detected by the detection device is within the operating range of the work robot, and a robot control device that controls the operation of the work robot, wherein when the platform is moving, the detection device continuously attempts to detect the target object at a sampling frequency equivalent to a value obtained by dividing the maximum vertical speed of the platform by the vertical dimension of the field of view of the detection device or the vertical dimension of a measurement range of the detection device , and the judgment device determines whether the target object is within the operating range of the work robot, and if it is within the operating range, instructs the robot control device to calculate a operating trajectory of the work robot in accordance with the position of the target object, and if it is not within the operating range, instructs the height adjustment device to adjust the height of the platform.

Moreover, the present invention has the steps of: (a) moving a platform on which a work robot is mounted to the height of a target object; (b) detecting the target object with a detection device attached to the work robot; and (c) determining whether the position of the target object detected by the detection device is within a motion range of the work robot, wherein in the step (b), while the platform is moving, detection of the target object is continuously attempted at a sampling frequency equivalent to a value obtained by dividing the maximum vertical speed of the platform by the vertical dimension of the field of view or the vertical dimension of the measurement range of the detection device; and in the step (c), if it is determined that the target object is within the motion range of the work robot, a motion trajectory of the work robot is calculated in accordance with the position of the target object, and if it is determined that the target object is not within the motion range of the work robot, the height of the platform is adjusted.

According to the present invention, in a work device in which a work robot is mounted on a vertically moving platform, it is possible to realize a work device and a control method thereof that can adjust the height of the work robot with high precision using a relatively simple and inexpensive configuration.

This allows the robot to perform tasks optimally when it comes to vertical movement.

Problems, configurations, and advantages other than those described above will become clear from the description of the embodiments below.

FIG. 2 is a front view of the assembly system arranged in the elevator hoistway according to the first embodiment of the present invention. FIG. 2 is a top view of the assembly system of FIG. 1 . 1 is a flowchart illustrating a method for optimizing the height of a robot for an assembly task according to the first embodiment of the present invention. 10 is a flowchart illustrating a method for optimizing the height of a robot for an assembly operation according to a second embodiment of the present invention. FIG. 11 is a front view of an assembly system arranged outside a building with windows according to a third embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to the drawings. Note that the same components in each drawing will be given the same reference numerals, and detailed descriptions of overlapping parts will be omitted.

The working device and its control method according to the first embodiment of the present invention will be described with reference to Figures 1 to 3.

In this specification, the working device will be described using an example of an assembly system that mainly performs assembly work inside an elevator hoistway, but the present invention is not limited to this, and as mentioned above, the device can also be applied to working devices for maintaining the exterior of buildings, fixing interior boards to walls, inspecting dam walls, wiping windows, etc.

Figure 1 is a front view of an assembly system 100 disposed within an elevator hoistway 101 in this embodiment. Figure 2 is a top view of the assembly system 100 in Figure 1. Figure 3 is a flow chart showing a method for optimizing the height of a robot for an assembly operation in this embodiment.

As shown in Figures 1 and 2, the assembly system 100 of this embodiment is disposed in an elevator hoistway 101 to perform assembly work. The assembly system 100 includes a robot arm 1 disposed on top of a vertically moving platform 2 suspended by at least two ropes 3.

The ropes 3 are wound or unwound by at least one reeling machine 4, respectively, allowing the vertically moving platform 2 to move up and down. At least one of the reeling machines 4 is equipped with an absolute position detector (not shown) that allows a rough estimation of the height of the vertically moving platform 2.

Note that the accuracy of estimating the height of the vertical moving platform 2 decreases due to the stretching and deterioration of the rope 3, so the value of the absolute position detector cannot be accurately related to the height of the vertical moving platform 2.

The orientation of the vertical moving platform 2 in the X and Y axes is measured by the tilt sensor 5. This orientation is adjusted by the winder controller 12, which sends winding commands to the winder 4 to keep the vertical moving platform 2 horizontal.

The assembly system 100 also includes a system control device 10 that includes a robot control device 11, a winding machine control device 12, a robot motion range determination device 13 (hereinafter simply referred to as the determination device 13), and a work planning device 14.

The robot control device 11 sends control commands to the robot arm to move the robot arm according to the plan created by the work planning device 14.

The work planning device 14 plans the operation of the winding machine 4, which is driven by the winding machine control device 12.

The determination device 13 determines whether the robot is at a height where it can perform assembly work without reaching an inaccessible area, whether the robot is at a singular point, or whether the robot will collide with the surrounding environment.

The elevator hoistway 101 in which the assembly system 100 is located includes a wall 6 surrounding the assembly system 100, two rails 7 fixed to the ground at a lower position, and a target 8 fixed to the rails 7.

The target 8 includes a bracket 8a, a clip bolt 8b, a clip 8c, and a nut 8d.

The clip bolt 8b presses the clip 8c against one side of the edge of the rail 7, and the nut 8d is screwed into the surface of the bracket 8a on the opposite side of the edge of the rail 7, thereby fixing the bracket 8a on the opposite side of the edge of the rail 7 to the rail 7. The clip bolt 8b passes through a hole (not shown) in the bracket 8a to connect with the nut 8d on the opposite side.

In addition to being fixed to the rail 7 by the clip bolt 8b and nut 8d, the bracket 8a may also be fixed by, for example, soldering.

The robot arm 1 is equipped with a target detection device 9 (hereinafter simply referred to as the target detection device 9) that is used to detect a target 8 outside the assembly system 100.

In this embodiment, a camera equipped with image processing capabilities for detecting a specific target is used as the target detection device 9. Note that other sensors equipped with target detection capabilities can also be used instead of a camera. For example, a laser profiler equipped with an algorithm for object detection, a laser scanner, or an ultrasonic distance sensor can be used instead of a camera.

In addition, in this embodiment, the assembly system 100 is used in the elevator hoistway 101, but the scope of application of the present invention is not limited to elevator hoistways. The present invention can also be applied to building exteriors, locations close to dam walls, construction facilities where interior boards need to be fixed to walls, and the like.

The assembly tasks performed by the assembly system 100 of this embodiment include tasks related to handling the target object 8. The type of handling task affects the determination of the robot's operating range, but is not critical to the concept of the present invention.

However, for ease of understanding in explaining the present invention, the handling operation is defined herein as a series of operations including untightening the clip bolt 8b, partially shifting the position of the bracket 8a, and tightening the clip bolt 8b.

This operation is performed to move the bracket 8a, one end of which is fixed to the rail 7, to a height on the wall 6 at which the bracket can be fixed to the wall surface (e.g., the height of a wall with a smooth surface).

Although not shown in Figures 1 and 2, to perform this task, at least a tool such as a nut runner for loosening the clip bolt and a tool such as an air gripper for gripping the bracket are required.

Figure 3 shows a flowchart of a method for optimizing the height of a robot to perform an assembly task in this embodiment.

First, in step S30, the vertical moving platform 2 is moved to a predetermined height close to the target 8.

Next, in step S31, the target detection device 9 (hereinafter also referred to as the camera) is moved to the previously estimated position of the target 8.

Next, in step S32, an attempt is made to detect the target 8 using the camera 9.

Next, in step S33, it is determined whether or not the target 8 can be detected.

Due to inaccuracies in the winder 4 or inaccuracies in the height of the target 8 due to manual placement, the target 8 may not be within the field of view 15 of the camera 9. If this is the case (No), move the camera 9 to a new search position and return to step S32 to repeat the detection of the target 8 by the camera 9.

On the other hand, if the target 8 is detected by the camera 9 in step S33 (Yes), the process proceeds to step S35, where it is checked whether the target 8 is within the working range of the robot arm 1.

If it is determined in step S35 that the target 8 is within the working range of the robot arm 1 (Yes), the process proceeds to step S37, where the trajectory of the robot assembly including the robot arm 1 is adjusted to a new target position to accommodate the height of the target 8, and the assembly work is performed.

On the other hand, if it is determined in step S35 that the target 8 is not within the working range of the robot arm 1 (No), the process proceeds to step S36, where the vertically moving platform 2 is moved to a new height, and the process returns to step S31, where the operations from step S31 onwards are repeated.

Note that the predetermined initial height of the vertical moving platform 2 and the pre-estimated search position of the target 8 can be obtained from 3D data or 2D drawings of the elevator hoistway 101.

It can also be obtained by directly measuring the height of the target 8 in advance, for example if the target 8 is manually positioned.

When considering the initial height of the vertical moving platform 2, the blind spot of the target detection device (camera) 9 should also be taken into account.

An example of a blind spot is a position of the camera 9 where there is a rope 3 or other object between the camera 9 and the target 8.

To detect a target 8, for example, features of the target 8 can be extracted via image processing from previously captured images of the same target 8, and then features matching those extracted features can be searched for in newly captured images during the search for the target 8.

If a matching feature is found, it means that the target 8 has been found. Examples of image processing methods for extracting image features include template matching and pattern detection. Also, the use of neural networks is conceivable.

To determine whether the target 8 is within the working range of the robot arm 1, the determination device 13 can simply check whether (1) the target 8 is within the joint limits of the robot arm 1, (2) whether it is not in a position that requires a robot configuration that may cause a robot singularity according to the specifications of the robot arm 1, (3) whether it is not in a position where a collision of the robot arm 1 has occurred in previous experience, and (4) even if it is not included in (1) to (3), it is not in a position where the joints of the robot arm 1 may be damaged by overload due to the posture of the robot.

To obtain these experiences, the robot arm 1 needs to be moved to various heights and tasks simulated to check for possible collisions. The possible collisions are then stored in a database (not shown) for access by the decision device 13.

As an example of (4), when the robot arm 1 tries to grasp an object, the position of the center of gravity of the robot arm 1 changes, causing the platform 2 to mutate and rotate, which causes the gripper position of the robot arm 1 to mutate, making it unable to grasp the object or resulting in a collision. In addition, when the robot arm grasps an object and is handling it, the posture of the robot may cause the platform 2 to move in a way that puts strain on the joints of the robot arm 1, causing the robot arm 1 to break or stop due to joint overload.

To determine whether the robot arm 1 is in a position where it will stop due to an overload, it is necessary to detect the load just before the overload using data from past operation tests or a sensor. Examples of load detection sensors include current sensors that measure the current at each joint of the robot arm 1, torque sensors that measure the torque at each joint of the robot arm 1, and force sensors that are attached to the tip of the robot arm 1 and measure the force and moment at the tip of the robot arm 1.

Another method for determining whether the target 8 is within the working range of the robot arm 1 is to (1) create a simulated environment with all components of the assembly system 100 as well as all components of the working environment (i.e., the elevator shaft 101), (2) update the environment based on the position of the target 8 obtained by the camera 9, and (3) try to find a collision-free path to manipulate the target 8 via a graph-based trajectory search algorithm, e.g., a fast-searching random tree (RRT).

If a path is found, the target 8 is determined to be within the working range of the robot arm 1; otherwise, the target 8 is determined to not be within the working range of the robot arm 1. If the target 8 is not found at the initial search position, the new camera 9 position for searching the target 8 can be any position within the working range of the robot arm 1 and not measured by the camera 9.

To efficiently search for the target 8, the robot arm 1 can be moved with a step size equal to or smaller than the horizontal or vertical field of view 15 of the camera 9.

Considering that the estimation of the target 8's position in the lateral direction (Y-axis in Fig. 1) is always accurate, an efficient approach to search for the target 8 is to move in the direction (upwards or downwards) in which the robot arm 1 can move longer without reaching its reach limit, with a step size equal to the vertical field of view of the camera 9.

If a reach limit is reached after successive search steps in one direction, an efficient approach is to return the robot arm 1 to the initial search position and continue searching in the other direction.

In this way, the robot arm 1 can cover the entire search area in the vertical direction, and if the target object 8 is not found, the determination device 13 can reliably determine that the target object 8 is not within the working range of the robot arm 1.

When the position of the detected target 8 is determined not to be within the working range of the robot arm 1, the new height of the vertical moving platform 2 may be in a direction and step size that places the target 8 in a predetermined optimal working position relative to the robot arm 1. This optimal position may be obtained by prior experimentation using the assembly system 100.

If the target 8 is not found, the new vertical moving platform 2 height may be a height shifted upwards or downwards from the current platform position with a step size equal to the vertical working range of the robot arm 1.

Without any experience as to why target 8 was not detected, the search direction can be chosen randomly.

The above-described method allows the robot arm 1 of the assembly system 100 to be positioned at a height that optimizes the assembly operation.

A working device and a control method thereof according to a second embodiment of the present invention will be described with reference to FIG. 4. FIG. 4 is a flow chart showing a method for optimizing the height of a robot for assembly work according to this embodiment. This embodiment is a modified version of the first embodiment (FIG. 3).

As shown in FIG. 4, first, in step S40, the vertical moving platform 2 is moved (raised) while attempting to detect the target 8 using the camera 9.

Next, in step S41, it is determined whether or not the target 8 can be detected.

If the camera 9 does not detect the target 8 (No), return to step S40 and continue moving the vertical moving platform 2 until it reaches the upper or lower limit, depending on the direction of movement of the vertical moving platform 2.

On the other hand, if the camera 9 detects the target 8 (Yes), the process proceeds to step S42, and the movement of the vertical moving platform 2 is stopped.

Next, in step S43, the camera 9 is moved to the position where the target 8 was detected, and the target 8 is detected more precisely. In other words, the vertical moving platform 2 and the robot arm 1 are moved to a better detection height in order to redetect the target 8.

Next, proceed to step S44 and check whether the target 8 is within the working range of the robot arm 1.

If it is determined in step S44 that the target object 8 is within the working range of the robot arm 1 (Yes), the process proceeds to step S46, where the trajectory of the robot assembly including the robot arm 1 is adjusted to a new target position to accommodate the height of the target object 8, and the assembly work is performed.

On the other hand, if it is determined in step S44 that the target 8 is not within the working range of the robot arm 1 (No), the process proceeds to step S45, where the vertical moving platform 2 is moved to a new (different) height, and then the process returns to step S43, and the operations from step S43 onwards are repeated.

The redetection of the target 8 in step S43 is performed because detection of the target 8 while the vertical moving platform 2 is moving may be subject to image acquisition errors due to the movement of the vertical moving platform 2.

Higher sampling frequencies and faster shutter speeds can reduce this image acquisition error, but redetection is more reliable.

Another reason for redetection is that there is a delay between when the target 8 is detected and when the vertical moving platform 2 comes to a complete stop. Therefore, after the vertical moving platform 2 comes to a stop, the position of the target 8 is not the same as when the target 8 was detected.

By performing a pre-estimation of the delay and an estimation of the height traveled during this delay, it is possible to compensate for height errors in the target 8 position estimate. However, re-detection of the target 8 with the vertical moving platform 2 in a stationary state is more accurate.

If the height traveled during this delay is used to compensate for height errors in the position of the detected target 8, it can be ensured that the target 8 is within the field of view 15 of the camera 9 when the camera 9 moves to redetect the target 8.

Compared to the method of Example 1 (Figure 3), this method is advantageous because it seeks to continuously detect the target 8 as the vertical moving platform 2 ascends, and does not rely on a prior estimation of the position of the target 8, e.g. by 3D data verification.

However, this method is prone to detection errors since the target 8 is detected as moving. Another drawback is that the camera 9 used must have a high enough sampling frequency to capture all heights traveled by the vertical moving platform 2, which can be calculated by equation (1).

where f is the sampling frequency, Vplatf is the maximum vertical speed of the platform, and dVFOV' is the vertical field of view of camera 9. Note that if another sensor is used, the measurement range of the sensor can be replaced with dVFOV.

The working device and its control method according to the third embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 is a front view of the assembly system arranged outside the building with windows according to this embodiment.

As shown in FIG. 5, the assembly system 100 of this embodiment is placed outside a building 501 with windows, and performs window cleaning work as an example of maintenance work.

The basic configuration of the assembly system 100 of this embodiment is similar to that of embodiment 1 (FIGS. 1 and 2), but differs from embodiment 1 (FIGS. 1 and 2) in that the winding machine 4 is disposed on the vertically moving platform 2, and the rope 3 is not stored inside the winding machine 4 when wound, but passes through the winding machine 4 when the vertically moving platform 2 moves vertically.

The exterior of the building with windows 501 has an exterior wall 52 and a window 53. The window 53 is rectangular and has four corners. These four corners are the target 8 in this embodiment. In FIG. 5, the four corners that are the target 8 are highlighted, but they are the shape of the four corners of a normal window and do not have the special shape required for use in the method of the present invention.

The methods described in Examples 1 and 2 can be used with the windowed building 501 of this example, but in this assembly environment, the detected targets 8 are the four corners of the window 53. The window has four corners, any of which can be detected. A detection algorithm that can detect all four corners of the window 53 is more effective in estimating the robot's position, since it provides more options for detecting the window's position in case one corner is misdetected.

It should be noted that the targets 8 used in Examples 1 to 3 are merely illustrative and do not limit the scope of the claims. Any object that can be used as a reference to determine the height of the assembly system 100 compared to the area in which the assembly work is performed is valid. Non-objects such as marks on a wall or rail can also be used as reference points (targets 8).

The present invention is not limited to the above-described embodiments, but includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

REFERENCE SIGNS LIST 1: Robot arm 2: Vertical moving platform 3: Rope 4: Winding machine 5: Tilt sensor 6: Wall 7: Rail 8: Target 8a: Bracket 8b: Clip bolt 8c: Clip 8d: Nut 9: Target detection device (target detection device, camera)
10: System control device 11: Robot control device 12: Winding machine control device 13: Robot motion range determination device (determination device)
14: Work planning device 15: Field of view 52: Exterior wall (of a building with windows) 53: Window (of a building with windows) 100: Assembly system 101: Elevator hoistway 501: Building with windows

Claims (11)

A work robot that performs a task on a target object;
A platform on which the work robot is mounted;
a height adjustment device for adjusting the height of the platform;
A detection device for detecting the target;
a determination device that determines whether the position of the target detected by the detection device is within an operating range of the work robot;
a robot control device for controlling an operation of the working robot,
the detection device continually attempts to detect the target as the platform moves, at a sampling frequency corresponding to a maximum vertical velocity of the platform divided by a vertical dimension of a field of view or a vertical dimension of a measurement range of the detection device;
the determination device determines whether the target is within an operating range of the work robot;
If the target object is within the motion range, instruct the robot control device to calculate a motion trajectory of the working robot in accordance with the position of the target object;
A working device characterized in that, if the platform is not within its operating range, the working device instructs the height adjustment device to adjust the height of the platform. The working device according to claim 1,
The work apparatus is characterized in that the determination device determines whether the position of the target object is within the joint limits of the work robot, or whether the position of the target object is within an area where a collision occurred with the work robot in a past movement experiment. The working device according to claim 1,
the determination device updates a simulation environment using components of the work device and components of a work environment based on the position of the target object detected by the detection device;
A work apparatus that generates a collision-free path within the simulated environment via a path generation algorithm that represents the location of the object within a working envelope of the work robot. The working device according to claim 1,
The work device is characterized in that, when the determination device determines that the target is not within the operating range of the work robot, the determination device moves the detection device with a step size that is equal to or smaller than the vertical measurement capability of the detection device. The working device according to claim 1,
The work device is characterized in that, when the determination device determines that the target is not within the operating range of the work robot, the determination device moves the platform in a step size that is equal to or smaller than the vertical movement range of the work robot. The working device according to claim 1,
A working device characterized in that a height of the platform that will move from the time the target is detected until the platform completely stops is estimated in advance, and the detection position of the target by the detection device is corrected based on the estimated height. The working device according to claim 1,
1. A working device that is disposed in an elevator shaft and performs assembly work within the elevator shaft. The working device according to claim 1,
A work device that is placed on the exterior wall of a building with windows, detects the four corners of the windows as the targets, and performs window wiping work. The working device according to claim 1,
The working apparatus is characterized in that the determination device determines whether the posture of the work robot is in a posture just before the joints of the work robot would have stopped due to overload in a past movement experiment, or whether the joints of the work robot are in a posture just before the joints of the work robot would have stopped due to overload, based on a signal from a load detector attached to the work robot. (a) moving a platform carrying a work robot to a target height;
(b) detecting the target object with a detection device attached to the work robot;
(c) determining whether the position of the target detected by the detection device is within an operating range of the work robot;
In step (b), while the platform is moving, continuously attempting to detect the target at a sampling frequency corresponding to a maximum vertical speed of the platform divided by a vertical dimension of a field of view or a vertical dimension of a measuring range of the detection device;
When it is determined in step (c) that the target object is within a motion range of the work robot, a motion trajectory of the work robot is calculated in accordance with the position of the target object;
A method for controlling a working device, comprising the steps of: adjusting a height of the platform when it is determined that the target is not within an operating range of the working robot. A control method for a work device according to claim 10, comprising:
Between the step (b) and the step (c),
(d) a step of moving the detection device to the position where the target was detected and re-detecting the target.

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