Object detection method and robot system

Abstract

This object detection method is for detecting an object on the basis of the relative speed and the distance with respect to each reflection point in a reflection point group measured by an electromagnetic wave sensor, the method comprising: a recognition step for recognizing, as an object, a plurality of reflection points proximal to each other in the reflection point group; a distance-setting step for setting, as the distance to the object, the distance to a reflection point most proximal to the electromagnetic wave sensor among the plurality of reflection points included in the recognized object; and a speed-setting step for setting, as the speed of the object, the speed of a reflection point having the highest speed toward the electromagnetic wave sensor among the plurality of reflection points included in the recognized object.

Description

Object detection method and robot system

[0001] Disclosed herein are object detection methods and robotic systems.

[0002] Conventionally, radar devices are known that transmit radio waves, receive reflected waves reflected by reflection points on an object, and recognize the relative position (distance and direction) and relative speed of the object (reflection point). For example, Patent Document 1 discloses a device that groups multiple reflection points moving approximately on the same line, recognizes them as an object, and sets the reflection point in the group that is closest to the radar device as the representative position of the group (position of the object). Furthermore, Patent Document 2 discloses a device that performs clustering processing on reflection points whose relative positions and relative speeds are close, and calculates the average speed of each reflection point in the cluster as the speed of the object.

[0003] JP 2008-298544 A JP 2018-5787 A

[0004] However, when detecting an approaching object to avoid a collision with the object, it may not be sufficient to simply set the average position as the representative position or the average speed as the representative speed. This is because the distance may vary depending on the reflection point of the object, and the relative speed may vary depending on the reflection point of the object. An example of a case where the distance may vary depending on the reflection point of the object or the relative speed may be when a worker approaches the sensor while swinging his or her arms. In this case, the speed of the worker's arms approaches the radar device faster than the walking speed of the worker, and the worker's arms are closer to the radar device than the torso.

[0005] A primary object of the present disclosure is to more reliably detect the risk of a collision with an approaching object.

[0006] The present disclosure has adopted the following means to achieve the above-mentioned main object.

[0007] The object detection method disclosed herein is an object detection method that detects an object based on the distance and relative speed to each reflection point of a group of reflection points measured by an electromagnetic wave sensor, and includes: a recognition step of recognizing multiple reflection points that are close to each other in the group of reflection points as the object; a distance setting step of setting the distance to the object to the distance of the reflection point that is closest to the electromagnetic wave sensor among the multiple reflection points included in the recognized object; and a speed setting step of setting the speed of the reflection point that is moving toward the electromagnetic wave sensor the fastest among the multiple reflection points included in the recognized object.

[0008] This object detection method determines that the object located at the reflection point closest to the sensor is approaching at the speed of the reflection point approaching the sensor at the fastest speed, making it possible to more reliably detect the risk of collision with an approaching object.

[0009] The robot system of the present disclosure comprises a robot; a sensor unit that measures the distance and relative speed to each reflection point of a group of reflection points by transmitting electromagnetic waves and receiving reflected waves; a recognition unit that recognizes multiple reflection points that are close to each other in the group of reflection points as the object; a distance setting unit that sets the distance to the object to the distance of the reflection point that is closest to the sensor unit among the multiple reflection points included in the recognized object; a speed setting unit that sets the speed of the object to the speed of the reflection point that is moving toward the sensor unit at the fastest speed among the multiple reflection points included in the recognized object; and a robot control unit that controls the robot based on the distance to the object and the speed of the object.

[0010] This robot system can more reliably determine the risk of collision with an approaching object, ensuring safety when operating the robot.

[0011] 1 is a schematic configuration diagram of a robot system 1. FIG. 2 is a block diagram showing electrical connection relationships of the robot system 1. FIG. 3 is a flowchart showing an example of detection processing. FIG. 4 is an explanatory diagram showing how reflection points D are clustered. FIG. 5 is an explanatory diagram showing how a relative distance L to an object is set. FIG. 6 is an explanatory diagram showing how a relative speed V to an object is set. FIG. 7 is an explanatory diagram showing how a speed limit value is set based on the relative distance L and relative speed V to each of a plurality of clusters C. FIG. 8 is an explanatory diagram showing an example of a setting table. FIG. 9 is a schematic configuration diagram showing a modified example of a robot system.

[0012] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0013] Fig. 1 is a schematic configuration diagram of a robot system 1. Fig. 2 is a block diagram showing the electrical connections of the robot system 1. As shown in the figure, the robot system 1 of this embodiment includes a robot main body 10, a robot control device 20 that controls the operation of the robot main body 10, a robot safety device 30 that can detect objects (interfering objects such as a worker) around the robot main body 10, and a setting device 40 (see Fig. 2).

[0014] The robot body 10 is a work robot that performs a specified task, and examples thereof include a processing robot that processes a workpiece with a tool, a transport robot that grasps a workpiece with a chuck and transports it to another position, and an assembly robot that grasps a workpiece with a chuck and assembles it to an object.

[0015] As shown in Fig. 1, the robot main body 10 has a base 11 and an articulated arm 12 mounted on the base 11. The articulated arm 12 has a plurality of arms connected in series to the base 11 via joint axes. As shown in Fig. 2, each joint axis is provided with a servo motor 15 that drives the corresponding joint axis, and an encoder 16 (rotary encoder) that detects the rotation angle of the corresponding servo motor 15. The robot main body 10 also has an amplifier unit 17 that applies a driving current to each servo motor 15.

[0016] The robot control device 20 includes a control unit 21 configured as a microprocessor including a CPU, ROM, and RAM, and an I / O port 22 for exchanging signals with the control unit 31 of the safety device 30. The robot control device 20 also outputs control signals to the amplifier unit 17 of the robot main body 10 and inputs detection signals from the encoder 16.

[0017] The control unit 21 of the robot control device 20 controls the operation of the robot main body 10 as follows. Specifically, the control unit 21 first sets a target angle for each joint axis of the articulated arm 12 using inverse kinematics based on the target position and target posture of the hand. Next, the control unit 21 acquires the current angle of each joint axis from the corresponding encoder 16 and sets a speed command value for each joint axis using feedback calculations (e.g., proportional-integral calculations or proportional-integral-derivative calculations) based on the difference between the target angle and the current angle. Next, the control unit 21 inputs a speed limit value from the safety device 30. The speed limit value is a value that limits the speed command value within a range of 0 (0%) to 1 (100%). The speed limit value is set so that the higher the risk level, which indicates the degree of risk of an object colliding with the robot main body 10, i.e., the higher the risk of an object colliding with the robot main body 10, the greater the speed limit of the robot main body 10. The risk level will be described in detail later. The control unit 21 then multiplies the speed limit value by the speed command value to set a target speed that limits the speed command value. For example, if the speed limit value is 1 (100%), the target speed is the same as the speed command value. In other words, the movement of the robot body 10 is not limited. If the speed limit value is 0.5 (50%), the target speed is half the speed command value. If the speed limit value is 0 (0%), the target speed is 0 regardless of the speed command value. In other words, the movement of the robot body 10 is stopped. After setting the target speed, the control unit 21 calculates the current speed from the current angle of the joint axis acquired from the encoder 16, and sets a torque command value to be output from the servo motor 15 by feedback calculation (e.g., proportional-integral calculation or proportional-integral-derivative calculation) based on the difference between the calculated current speed and the target speed. The control unit 21 then outputs a control signal to the corresponding amplifier unit 17 so that the servo motor 15 outputs a torque corresponding to the set torque command.

[0018] In this embodiment, the robot safety device 30 is attached to the hand of the articulated arm 12. The safety device 30 includes a control unit 31 configured as a microprocessor including a CPU, ROM, and RAM, a sensor unit 32 that monitors the surroundings, and an I / O port 33 for exchanging signals with the control unit 21 of the robot control device 20. Note that the signals exchanged with the control unit 21 of the robot control device 20 may be duplicated.

[0019] In this embodiment, the sensor unit 32 is configured as a MIMO (Multi-Input Multi-Output) radar sensor using the FMCW (Frequency Modulation Continuous Wave) method. The sensor unit 32 has, for example, a fan-shaped detection area in three-dimensional space. The sensor unit 32 includes a transmitting antenna that transmits a transmitted chirp, a receiving antenna that receives a reflected wave from a target (reflection point) as a received chirp, a mixer that mixes the transmitted chirp and the received chirp to generate an intermediate frequency signal (IF signal), and a processing unit that processes the IF signal to detect the relative distance to the target (reflection point), the relative velocity with respect to the target (reflection point), and the angle of the target (reflection point). The transmitting antenna transmits multiple transmitted chirps, each spaced at a fixed interval, as one frame. The processing unit includes an A / D converter that performs A / D conversion on the IF signal generated by the mixer, a DSP that performs Fourier transform (FFT) processing on the A / D converted IF signal, and the like. The DSP performs FFT processing (distance FFT processing) on ​​the IF signal in chirp units to obtain a frequency spectrum, and then calculates the relative distance between the sensor unit 32 and the object (reflection point) based on the peak frequency. The DSP also performs FFT processing (velocity FFT processing) on ​​the data after the distance FFT processing in frame units to obtain a frequency spectrum, and then calculates the relative velocity between the sensor unit 32 and the object (reflection point) based on the peak frequency. The DSP also performs FFT processing (angle FFT processing) on ​​the data after the velocity FFT processing in receiving antenna units to obtain a frequency spectrum, and then calculates the angle of the object (reflection point) relative to the sensor unit 32 based on the peak frequency. In this way, the sensor unit 32 obtains point cloud data by measuring the relative distance and relative velocity from the reflection point for each angle.

[0020] Next, a description will be given of the operation of the safety device 30 when the robot main body 10 is in operation. Fig. 3 is a flowchart showing an example of detection processing executed by the control unit 31 of the safety device 30. This processing is executed at predetermined time intervals (for example, every few ms) while the robot main body 10 is in operation.

[0021] When this process starts, the control unit 31 first acquires the point cloud data described above from the sensor unit 32 (S100). Next, the control unit 31 performs clustering processing (S102). Specifically, the control unit 31 calculates the distances between reflection points D, extracts a set of reflection points D (hereinafter referred to as cluster C) of a predetermined number or more where the calculated distances fall within a predetermined range as the object, and assigns a cluster number to each cluster C. The control unit 31 also removes reflection points D with a number less than the predetermined number as noise. Next, the control unit 31 sets the value of cluster number i to 1 (S104). Then, as shown in FIG. 5, the control unit 31 sets the shortest relative distance (relative distance L2 in FIG. 5) among the relative distances of the reflection points D belonging to the i-th cluster C (hereinafter referred to as the i-th cluster C) as the relative distance L from the safety device 30 to the object (S106).

[0022] Next, as shown in FIG. 6 , the control unit 31 sets the maximum relative speed among the relative speeds of the reflection points D belonging to the i-th cluster C as the relative speed V of the object with respect to the safety device 30 (relative speed V3 in FIG. 6 ) (S108). An example of a case in which the relative speeds vary within cluster C is when a worker approaches the sensor unit 32 while swinging their arms. In this case, the reflection points D obtained by receiving reflected waves reflected by the worker's arms and torso are close to each other, and are extracted as a single object in the clustering process. However, because the speed at which the worker swings their arms is faster than the speed at which the torso approaches, the relative speeds vary within cluster C. Next, the control unit 31 sets a risk level based on a combination of the relative distance L to the object and the relative speed V of the object (S110). The risk level is, for example, 0, 1, 2, 3, or 4, and the higher the value, the higher the possibility that the object will collide with the robot main body 10. Specifically, the control unit 31 sets a risk level corresponding to a combination of the relative distance L to the object and the relative speed V of the object, with reference to the setting table shown in Fig. 9. In the setting table, the risk level is determined to increase, for example, as the relative distance L decreases and as the relative speed V increases. The worker can create the setting table by connecting a setting device (PC) (not shown) to the safety device 30 in advance and operating the setting device to input the risk level for each relative distance L and each relative speed V. After setting the risk level, the control unit 31 stores the speed limit value in a storage device (not shown) in association with the cluster number i (S112).

[0023] Next, the control unit 31 increments the value of the cluster number i by 1 (S114). Then, the control unit 31 determines whether the value of the cluster number i is greater than the number of clusters C extracted in S102 (S116). If it is determined that the value of the cluster number i is equal to or less than the number of clusters C extracted in S102, the control unit 31 determines that there are still clusters C for which a risk level is to be set, and returns to S106 again.

[0024] In this way, the control unit 31 sets the relative distance to the object as the relative distance L to the object, which is the closest relative distance to the sensor unit 32 among the reflection points D in the cluster C, sets the relative speed of the object that approaches the sensor unit 32 fastest among the reflection points D in the cluster as the relative speed V of the object, and sets the risk level based on the combination of the relative distance L and the relative speed V. This makes it possible to more reliably detect the risk of collision with the object.

[0025] If it is determined that the value of the cluster number i is greater than the number of clusters C extracted in S102, the control unit 31 determines that risk levels have been set for all clusters C and sets a speed limit value based on the largest risk level among the risk levels of the clusters C (S118). An example of this process will be described with reference to FIG. 7. In the example shown in FIG. 7, a cluster C (hereinafter referred to as the first cluster C1) having a relative distance L of 900 (mm) and a relative velocity V of 600 (mm / S) and a cluster C (hereinafter referred to as the second cluster C2) having a relative distance L of 1600 (mm) and a relative velocity V of 1800 (mm / S) are extracted from the point cloud data. The risk level corresponding to the relative distance L and relative velocity V from the first cluster C1 is a value of 2, and the risk level corresponding to the relative distance L and relative velocity V from the second cluster C2 is a value of 3. Next, the control unit 31 sets a speed limit value corresponding to the largest risk level among the risk levels of the clusters C. The speed limit value is the ratio of the target speed to the speed command value. The speed limit value is set in the range of 0 to 1, for example, 0, 0.25, 0.5, 0.75, or 1. The control unit 31 sets the speed limit value to 0 if the maximum risk level is 4; 0.75 if the maximum risk level is 3; 0.5 if the maximum risk level is 2; 0.25 if the maximum risk level is 1; and 1 if the maximum risk level is 0. In the example shown in FIG. 7 , the risk level corresponding to the combination of the relative distance L and relative velocity V from the first cluster C1 is 2, and the risk level corresponding to the combination of the relative distance L and relative velocity V from the second cluster C2 is 3. Therefore, the speed limit value (0.25) corresponding to the risk level value 3 is set. In this way, the control unit 31 sets the speed limit value that most greatly limits the speed of the robot main body 10. Then, the control unit 31 outputs the speed limit value to the robot control device 20 (S120), and ends this process. The control unit 21 of the robot control device 20 multiplies the speed command value by the speed limit value to set the target speed.

[0026] In the detection process, the control unit 31 sets the risk level based on a combination of the relative distance L and the relative speed V. This makes it possible to quantitatively determine the risk of collision between the robot main body 10 and an object.

[0027] Furthermore, in the detection process, the control unit 31 sets a risk level based on a combination of the relative distance L and the relative speed V, and sets a speed limit value according to the risk level. Therefore, the robot main body 10 can be operated safely according to the risk level.

[0028] In the detection process, the control unit 31 outputs to the robot control device 20 a speed limit value that most greatly limits the speed of the robot main body 10. This allows the robot main body 10 to operate more safely.

[0029] In addition to the normal mode in which the above-described detection process is performed, the safety device 30 also has a setting mode in which various settings of the safety device 30 can be configured by connecting a setting device. In the setting mode, the operator can check whether there are any problems with the settings of the safety device 30. In the setting mode, instead of performing the process of S120, the control unit 31 outputs the relative distance L set in S106, the relative velocity V set in S108, the risk level set in S110, and the speed limit value set in S118 to the setting device, and then ends the detection process. The setting device displays this information on the display device. This allows the operator to perform various settings, including creating a setting table, while checking the risk level and speed limit value corresponding to the combination of the relative distance L and the relative velocity V before installing the safety device 30 on the robot main body 10 and checking the operation of the robot main body 10.

[0030] Here, the correspondence between the main elements of the embodiment and the main elements of the present disclosure described in the claims will be described. That is, the detection process of the embodiment corresponds to an object detection method, S102 of the detection process corresponds to a recognition process, S106 of the detection process corresponds to a distance setting process, and S108 of the detection process corresponds to a speed setting process. Furthermore, S110 of the detection process corresponds to a risk level setting process. Furthermore, S112 of the detection process corresponds to a command value setting process. Furthermore, S120 of the detection process corresponds to a setting process. Furthermore, the robot main body 10 corresponds to the robot, the control unit 31 that executes the process of S102 of the detection process corresponds to a recognition unit, the control unit 31 that executes the process of S106 of the detection process corresponds to a distance setting unit, the control unit 31 that executes the process of S108 of the detection process corresponds to a speed setting unit, and the control unit 21 of the robot control device 20 corresponds to a robot control unit.

[0031] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

[0032] In the above-described embodiment, the control unit 31 of the safety device 30 sets the risk level based on the combination of the relative distance L and the relative speed V, and sets the speed limit value according to the risk level. However, the control unit 31 of the safety device 30 may directly set the speed limit value based on the combination of the relative distance L and the relative speed V, without setting the risk level. In this case, the setting table may store speed limit values ​​according to the combinations of the relative distance L and the relative speed V.

[0033] In the embodiment described above, the control unit 31 of the safety device 30 sets the speed limit value based on the combination of the relative distance L and the relative speed V. However, the control unit 31 of the safety device 30 may transmit the relative distance L and the relative speed V to the robot control device 20, so that the control unit 21 of the robot control device 20 sets the speed limit value based on the combination of the relative distance L and the relative speed V.

[0034] In the above-described embodiment, the safety device 30 is attached to the hand (tip) of the articulated arm 12 of the robot main body 10. However, it may also be attached to the base 11 of the robot main body 10. Furthermore, while the safety device 30 is provided on a stationary robot, it may also be provided on a self-propelled robot. The self-propelled robot may be an arm robot with the above-described articulated arm, or a transport robot. For example, as shown in FIG. 9 , in a mounting line 100 having multiple component mounters 101 each having feeder tables arranged in the transport direction of a board and each having a detachable feeder 102, the automatic exchange robot 110 may move along the mounting line 100 to exchange the feeders 102 for each component mounter 101. The safety device 30 is provided on the automatic exchange robot 110. When an object is detected within its detection range, the safety device 30 sets a speed limit value based on the relative distance and relative speed to the object and outputs the speed limit value to the automatic exchange robot 110. The automatic exchange robot 110 sets a target speed based on the input speed limit value.

[0035] In the above-described embodiment, the control unit 31 of the safety device 30 sets the speed limit value based on a combination of the relative distance L and the relative speed V to the object. However, the control unit 31 may calculate an expected arrival time until the robot reaches the sensor unit 32 based on the combination of the relative distance L and the relative speed V to the object, and set the speed limit value based on the expected arrival time. In this case, the control unit 31 may set the speed limit value such that the shorter the expected arrival time, the greater the restriction on the speed of the robot main body 10.

[0036] As described above, the object detection method of the present disclosure determines that the object located at the reflection point closest to the sensor is approaching the sensor at the speed of the reflection point approaching the sensor at the fastest speed, thereby making it possible to more reliably detect the risk of collision with an approaching object.

[0037] The object detection method disclosed herein may also include a risk level setting step of setting a risk level of the object relative to the electromagnetic wave sensor based on a combination of the distance to the object and the speed of the object. This allows for quantitative understanding of the risk of the object colliding with the electromagnetic wave sensor. In this case, the method may be applied to a robot system equipped with the electromagnetic wave sensor and may include a command value setting step of setting a control command value including a movement limit for a robot of the robot system based on the risk level. This allows the robot to operate safely. In this case, the command value setting step may set the control command value such that the greater the risk level, the greater the restriction on the movement of the robot. This allows the robot to operate more safely.

[0038] Furthermore, the object detection method of the present disclosure may be applied to a robot system equipped with the electromagnetic wave sensor, and may include a command value setting step of setting a control command value including a movement limit for a robot of the robot system based on a combination of the distance to the object and the speed of the object. This allows the robot to operate safely. In this case, the command value setting step may set the control command value such that the movement of the robot is more greatly restricted as the distance to the object becomes closer and the speed of the object becomes faster. This allows the robot to operate more safely.

[0039] In addition, in the object detection method of the present disclosure in which the movement of the robot is significantly restricted, when multiple objects are recognized in the recognition step, the command value setting step may set the control command value that most significantly restricts the movement of the robot for the multiple objects. In this way, the control command value can be determined taking into consideration the distance and relative speed to the object that is most likely to collide with the electromagnetic wave sensor among multiple objects approaching the electromagnetic wave sensor, thereby allowing the robot to operate sufficiently safely.

[0040] The present disclosure can also be applied to a robot system, in which case it is possible to more reliably determine the risk of collision with an approaching object, thereby ensuring safety when operating the robot.

[0041] The present disclosure is applicable to the robot manufacturing industry and the like.

[0042] 1 Robot system, 10 Robot body, 11 Base, 12 Articulated arm, 15 Servo motor, 16 Encoder, 17 Amplifier unit, 20 Robot control device, 21 Control unit, 22 I / O port, 30 Safety device, 31 Control unit, 32 Sensor unit, 33 I / O port, 40 Setting device, 100 Mounting line, 101 Component mounter, 102 Feeder, 110 Automatic exchange robot.

Claims

1. A method for detecting an object based on the distance and relative speed of each reflection point of a group of reflection points measured by an electromagnetic wave sensor, comprising: a recognition step of recognizing multiple reflection points that are close to each other in the group of reflection points as the object; a distance setting step of setting the distance to the object to the distance of the reflection point that is closest to the electromagnetic wave sensor among the multiple reflection points included in the recognized object; and a speed setting step of setting the speed of the reflection point that is moving toward the electromagnetic wave sensor the fastest among the multiple reflection points included in the recognized object to the speed of the object.

2. An object detection method as claimed in claim 1, comprising a danger level setting step of setting the danger level of the object to the electromagnetic wave sensor based on a combination of the distance to the object and the speed of the object.

3. An object detection method as claimed in claim 2, which is applied to a robot system equipped with the electromagnetic wave sensor and includes a command value setting step of setting a control command value including an operational limit for the robot of the robot system based on the degree of danger.

4. An object detection method according to claim 3, wherein the command value setting step sets the control command value so that the greater the degree of danger, the greater the restriction on the movement of the robot.

5. An object detection method as claimed in claim 1, which is applied to a robot system equipped with the electromagnetic wave sensor, and which includes a command value setting step of setting a control command value including an operational limit for the robot of the robot system based on a combination of the distance to the object and the speed of the object.

6. An object detection method as claimed in claim 5, wherein the command value setting step sets the control command value so that the movement of the robot is restricted to a greater extent the closer the distance to the object and the faster the speed.

7. An object detection method as claimed in claim 4 or 6, wherein, when a plurality of objects are recognized by the recognition process, the command value setting process sets the control command value that most largely restricts the movement of the robot with respect to the plurality of objects.

8. A robot system comprising: a robot; a sensor unit that measures the distance and relative speed to each reflection point in a group of reflection points by transmitting electromagnetic waves and receiving reflected waves; a recognition unit that recognizes a plurality of mutually adjacent reflection points in the group of reflection points as the target object; a distance setting unit that sets the distance to the target object to the distance of the reflection point that is closest to the sensor unit among the plurality of reflection points included in the recognized target object; a speed setting unit that sets the speed of the reflection point that is moving toward the sensor unit the fastest among the plurality of reflection points included in the recognized target object to the speed of the target object; and a robot control unit that controls the robot based on the distance to the target object and the speed of the target object.

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