JP7537296B2 - Robot Hand Device - Google Patents

Description

The present invention relates to a robot hand device.

Demand for robotics is increasing in factories and other workplaces due to labor shortages and other factors. As a result, there are more opportunities to use so-called pick-and-place systems, in which robots pick up parts and then place them. In recent years, the objects that robots can grasp have become more diverse, and some of these objects are sensitive to impact. When using robot hands to pick and place shock-sensitive objects, a design is required that takes into account the timing of grasping when picking and the timing of releasing when placing, and it is necessary to devise ways to reduce the impact on the object both when picking and placing.

In general, when an object of any shape is grasped using a robot hand such as a multi-fingered robot hand, or when the object is grasped from any direction, it is extremely difficult to appropriately control the timing of releasing the object from the robot hand when placing the object on the floor, etc. As a result, if the release timing is too early, the object will fall to the floor, and if the release timing is too late, the object will be pressed hard against the floor. In either case, the object will be subjected to an impact, which may cause damage to it.

Patent Document 1 describes a technology that calculates the reaction force from a specified location when placing an object held by a robot hand, and controls the robot hand to remove the object if the calculated reaction force exceeds a threshold value. Patent Document 1 also describes a technology that converts the fingertip resultant force in the coordinate system of the robot hand into a fingertip resultant force in the coordinate system of the base of the robot hand device depending on the posture of the robot hand from the coordinate system of the base of the robot hand device to the coordinate system of the robot hand, estimates the weight of the object based on the vertical fingertip resultant force among the fingertip resultant forces in the coordinate system of the base of the robot hand device, and calculates the reaction force from the location where the object is placed based on the difference between the estimated weight of the object and the force with which the robot hand grasps the object.

JP 2007-276112 A

However, the technology described in Patent Document 1 has a problem in that it is complex and difficult to calculate the release timing when placing an object grasped by a robot hand in a predetermined location (hereinafter also referred to as the "placement location") because there are multiple pieces of input information (an image signal PS obtained by photographing the object before it is grasped, a joint angle signal AS obtained by detecting the rotation angle of each joint, and a six-axis force signal FS in each finger) to calculate the release timing.

The present invention has been made to solve the above problems, and its purpose is to provide a robot hand device that can suppress impacts on objects with a simpler configuration.

The robot hand device according to the present invention includes a holding unit that holds an object, a movable unit that is displaced by a reaction force received from the object when the object held by the holding unit is placed at a place location, a displacement amount detection unit that detects the amount of displacement of the movable unit, and a control unit that controls the holding unit based on the amount of displacement of the movable unit detected by the displacement amount detection unit.

The present invention makes it possible to suppress the impact on an object with a simpler configuration.

1 is a side view showing a configuration example of a robot hand device according to an embodiment of the present invention. FIG. 2 is a schematic side view showing an enlarged view of part A in FIG. 1 . 4 is a flowchart showing an operation procedure of the robot hand device according to the embodiment of the present invention. 11 is a schematic side view showing a state in which the suction part is pressed against a pick location. FIG. 11 is a schematic side view showing a state in which the suction part is pressed against an object. FIG. 13 is a flowchart showing a method for setting a release threshold value.

Embodiments of the present invention will be described in detail below with reference to the drawings. In this specification and the drawings, elements having substantially the same functions or configurations are given the same reference numerals, and duplicated descriptions will be omitted.

<Configuration of Robot Hand Device>
FIG. 1 is a side view showing an example of the configuration of a robot hand device according to an embodiment of the present invention, and FIG. 2 is a schematic side view showing an enlarged view of a portion A in FIG.
As shown in FIGS. 1 and 2 , the robot hand device 10 includes a robot hand unit 12 and a control unit 14 that controls the operation of the robot hand unit 12 .

The robot hand unit 12 is used to transfer an object (not shown) from a pick location to a place location by pick and place. A pick location is a location for picking an object, i.e., a location from which the object is transferred. A place location is a location for placing an object, i.e., a location to which the object is transferred. The robot hand unit 12 is attached to a robot arm (not shown) and moves in accordance with the operation of the robot arm.

The robot hand unit 12 includes a hand main body unit 20, which is the main body of the robot hand unit 12, an adsorption unit 22 that holds an object (not shown) by air adsorption, a gripping unit 24 that grips the object, a movable unit 26 that can move in a predetermined direction, and a displacement amount detection unit 28 that detects the amount of displacement of the movable unit 26. The adsorption unit 22 is provided as an example of a holding unit.

The hand main body 20 has a drive mechanism for operating the gripping part 24. The suction part 22 is attached to a bracket 30. The bracket 30 is attached to the hand main body 20. The suction part 22 is preferably made of an elastic material exhibiting rubber-like elasticity. The suction part 22 has an air flow path (not shown) for holding an object by air suction. The end of the air flow path opens downward at the lower end of the suction part 22. On the other hand, the start end of the air flow path is connected to an air circuit (not shown). The air circuit is composed of an air tube, an air control valve, and the like. When an object is held by the suction part 22, the air circuit sucks air through the air flow path. In addition, when the object held by the suction part 22 is released, the air circuit stops sucking air. The operation of the air circuit is controlled by the control unit 14. In the following description, the state in which air is sucked by the air circuit is referred to as an on state, and the state in which air suction is stopped is referred to as an off state.

The gripping unit 24 is attached to the hand main body 20. As shown in FIG. 1, the gripping units 24 are arranged in pairs on the left and right. The gripping unit 24 includes a link mechanism 241 and a gripper unit 242. The link mechanism 241 opens and closes the left and right gripper units 242 by moving in the direction B in FIG. 1. The gripper unit 242 is a part that grips an object (not shown) by pinching it from both sides. The gripper unit 242 has a recess 242a that comes into contact with the object when gripping the object (not shown). The gripping unit 24 positions the object by gripping the object with the pair of gripper units 242.

When an object held by the suction unit 22 is placed at a place location, the movable unit 26 is displaced by a reaction force received from the object. The direction in which the movable unit 26 is displaced is the same as the direction of the reaction force received from the object. In this embodiment, when an object held by the suction unit 22 is placed at a place location, the direction of the reaction force received by the suction unit 22 and the movable unit 26 from the object, and the direction in which the movable unit 26 is displaced are both upward.

As shown in FIG. 2, the movable part 26 includes a slide rod 261 and a spring member 262 that biases the slide rod 261. The slide rod 261 is provided as an example of a slide member, and the spring member 262 is provided as an example of an elastic body.

The slide rod 261 has a large diameter rod portion 261a and a small diameter rod portion 261b. The large diameter rod portion 261a and the small diameter rod portion 261b may be an integral structure, or may be connected by a screw. The slide rod 261 is arranged with the large diameter rod portion 261a facing downward. The suction portion 22 is fixed to the lower surface of the large diameter rod portion 261a. The small diameter rod portion 261b is supported by a slide guide member 263 so that it can slide (move) freely in the vertical direction. The slide guide member 263 is fixed to the base member 32. The base member 32 is a member attached to the lower end of the bracket 30 to support the suction portion 22, the movable portion 26, and the displacement amount detection portion 28.

The spring member 262 is attached to the small diameter rod portion 261b of the slide rod 261. The spring member 262 is composed of a coil spring. The spring member 262 is arranged in a compressed state between the large diameter rod portion 261a and the slide guide member 263. The reaction force caused by the compression of the spring member 262 acts as a biasing force that biases the slide rod 261 and the suction portion 22 downward. In addition, a stopper (not shown) is attached to the upper end side of the small diameter rod portion 261b. The stopper is abutted against the upper surface of the slide guide member 263 so that the small diameter rod portion 261b of the slide rod 261 does not come off from the slide guide member 263.

The displacement amount detection unit 28 detects the amount of displacement of the slide rod 261, which is one component of the movable unit 26. The displacement amount detection unit 28 is, for example, configured by a displacement sensor. The displacement sensor outputs an analog sensor signal according to the amount of displacement of the slide rod 261. The sensor signal output by the displacement amount detection unit 28 is an electrical signal whose value, such as current, voltage, or resistance, changes according to the amount of displacement of the slide rod 261. This electrical signal is taken into the control unit 14. The control unit 14 obtains a detection value indicating the amount of displacement of the slide rod 261 by A/D (analog/digital) conversion of the electrical signal taken in from the displacement amount detection unit 28.

The control unit 14 controls the suction unit 22 based on the displacement of the movable unit 26 detected by the displacement amount detection unit 28. Specifically, the control unit 14 controls the suction unit 22 by switching the on/off state of the air suction by the air circuit described above. When the air suction by the air circuit is switched from the off state to the on state, an adsorption force due to the suction of air is generated in the suction unit 22. Therefore, it is possible to hold the object 35 by adsorbing it to the lower end of the suction unit 22. In contrast, when the air suction by the air circuit is switched from the on state to the off state, the adsorption force due to the suction of air disappears. Therefore, it is possible to release the object 35. In addition, the control unit 14 controls the operation of the grip unit 24 by driving the above-mentioned drive mechanism of the hand main body unit 20. In this embodiment, the control unit 14 controls both the operation of the robot hand device 10 and the operation of the robot arm.

<Operation of the robot hand device>
Next, the operation of the robot hand device 10 according to the embodiment of the present invention will be described with reference to the flowchart of FIG.

First, the control unit 14 moves the robot hand unit 12 to directly above the pick location by operating the robot arm (step S1).

Next, the control unit 14 drives the drive mechanism to open the gripper 24 (step S2). When the gripper 24 is opened, the pair of gripper parts 242 move in a direction away from each other in accordance with the operation of the pair of link mechanism parts 241. When the gripper 24 is opened in this manner, the suction part 22 is positioned protruding downward from the gripper part 242. This allows the suction part 22 to contact the object without the gripper 24 touching the object. Also, as shown in FIG. 4, by pressing the suction part 22 against the pick location 33 or the like, it is possible to check in advance whether the displacement amount detection unit 28 operates normally. Note that if the gripper 24 is already in an open state at the stage of step S1, the process of step S2 may be omitted.

Next, the control unit 14 vertically lowers the robot hand unit 12 by operating the robot arm (step S3). As a result, as shown in FIG. 2, if an object 35 is placed at the pick location 33, the suction unit 22 gradually approaches the object 35 by the descent of the robot hand unit 12. Then, when the suction unit 22 comes into contact with the object 35, the control unit 14 temporarily stops the descent of the robot hand unit 12 (step S4), and then closes the gripping unit 24 by driving the drive mechanism (step S5). When the gripping unit 24 is closed, the pair of gripper units 242 move in a direction approaching each other according to the operation of the pair of link mechanism units 241. As a result, the object 35 is gripped by the pair of gripper units 242 and positioned at a predetermined position. The timing for temporarily stopping the descent of the robot hand unit 12 may be the timing when the movable unit 26 begins to be displaced due to contact between the suction unit 22 and the object 35.

Next, as shown in FIG. 5, the control unit 14 resumes the descent of the robot hand unit 12 by operating the robot arm, thereby pressing the suction unit 22 against the object 35 (step S6). As a result, the suction unit 22 is compressed and deformed by the reaction force received from the object 35, and the movable unit 26 is displaced upward by the reaction force received from the object 35. The displacement of the movable unit 26 described here occurs when the spring member 262 is compressed by the reaction force received from the object 35, causing the slide rod 261 to move upward while being guided by the slide guide member 263.

Next, the control unit 14 judges whether the displacement amount of the movable unit 26 detected by the displacement amount detection unit 28 exceeds the holding threshold (step S7). At this time, if the displacement amount of the movable unit 26 does not exceed the holding threshold, the control unit 14 continues the descent of the robot hand unit 12, and if the displacement amount of the movable unit 26 exceeds the holding threshold, the control unit 14 stops the descent of the robot hand unit 12 (step S8). The holding threshold is a threshold that is set in advance to control the operation of the robot hand unit 12. The holding threshold is preferably set according to the hardness of the pick location. For example, if the pick location is a hard location formed of metal, hard plastic, or the like, the holding threshold is set to a small value, and if the pick location is a soft location formed of sponge, rubber, or the like, the holding threshold is set to a large value.

Next, the control unit 14 causes the suction unit 22 to hold the object 35 by sucking air from the air flow path of the suction unit 22 through the operation of the air circuit (step S9). As a result, the object 35 is held by the suction unit 22 while being positioned by the gripping unit 24.

Next, the control unit 14 drives the drive mechanism to open the gripping unit 24 (step S10), and then moves the robot arm to raise the robot hand unit 12 vertically (step S11).

Next, the control unit 14 moves the robot hand unit 12 to directly above the placement location by operating the robot arm (step S12).

Next, the control unit 14 vertically lowers the robot hand unit 12 by operating the robot arm (step S13). As a result, the object 35 held by the suction unit 22 gradually approaches the place location. When the object 35 comes into contact with the place location, the suction unit 22 is compressed and deformed by the reaction force from the object 35, and the movable unit 26 is displaced upward. The state of the robot hand unit 12 at this time is basically the same as that shown in FIG. 5, except that the pick location 33 has changed to the place location.

Next, the control unit 14 judges whether the displacement amount of the movable part 26 detected by the displacement amount detection unit 28 exceeds the release threshold (step S14). At this time, if the displacement amount of the movable part 26 does not exceed the release threshold, the control unit 14 continues the descent of the robot hand unit 12, and if the displacement amount of the movable part 26 exceeds the release threshold, the control unit 14 stops the descent of the robot hand unit 12 (step S15). The release threshold is a threshold that is set in advance to control the operation of the robot hand unit 12. The release threshold is preferably set according to the hardness of the place location. For example, if the place location is a hard location formed of metal, hard plastic, etc., the release threshold is set to a small value, and if the place location is a soft location formed of sponge, rubber, etc., the release threshold is set to a large value. The release threshold and the holding threshold may be the same value or different values.

Next, the control unit 14 releases the object 35 by stopping the air suction of the suction unit 22 through the operation of the air circuit (step S16). At this time, the control unit 14 may sequentially perform the closing and opening operations of the gripping unit 24 by driving the drive mechanism in order to improve the positional accuracy of the object 35 placed at the place location.

Next, the control unit 14 vertically raises the robot hand unit 12 by operating the robot arm (step S17). This causes the robot hand unit 12 to retreat from the placement location.

Then, the control unit 14 checks whether the transfer of all the planned objects 35 has been completed (step S18). If the next object 35 to be transferred remains at the pick location, the control unit 14 returns to the process of step S1 above, and if the transfer of all the objects 35 has been completed, the control unit 14 ends the series of operations. Note that the check in step S16 can be performed by counting the number of objects 35 transferred from the pick location to the place location by the control unit 14, and checking whether the count value has reached a predetermined value. The predetermined value is set to the number of objects planned to be transferred.

<Threshold setting method>
Next, a method for setting the release threshold will be described with reference to Fig. 6. Note that the method for setting the hold threshold is basically the same as the method for setting the release threshold, so a description thereof will be omitted.

First, the hardness of the object is measured using a hardness measuring device (not shown) (step S31). The hardness of the object may be measured by either an indentation test method or a dynamic test method. Measurement values obtained by the indentation test method include Brinell hardness, Vickers hardness, Rockwell hardness, etc., and measurements obtained by the dynamic test method include Shore hardness, Knoop hardness, etc.

Next, the hardness of the place location is measured using the hardness measuring device (step S32). The hardness measurement of the place location may be performed in the same manner as the hardness measurement of the object described above.

Next, a release threshold is set based on the hardness of the object obtained by the measurement in step S31 and the hardness of the place obtained by the measurement in step S32 (step S33). The release threshold may be set, for example, as follows.
First, the hardness of the object and the hardness of the place are added together, and the hardness value is calculated as half of the sum. Meanwhile, table data that associates multiple thresholds with multiple hardnesses is prepared in advance. Then, the threshold value associated with the hardness value calculated above is read from the table data, and the read threshold value is set as the release threshold value.

In this way, by setting the release threshold based on the hardness of the object and the hardness of the place location, for example when handling a soft object or placing an object in a hard place location, the release threshold can be set so that the object is released at an earlier timing. This allows the object to be released before it is pressed hard against the place location. Therefore, the impact on the object can be suppressed. This effect can also be obtained when setting the retention threshold using a method similar to that described above.

In this embodiment, the hardness of the object is measured before the hardness of the place location is measured, but the opposite can also be done, that is, the hardness of the object can be measured after the hardness of the place location is measured.

In addition, in this embodiment, the release threshold is set based on the hardness of the object and the hardness of the place location, but the present invention is not limited to this, and the release threshold may be set based only on the hardness of the object, or the release threshold may be set based only on the hardness of the place location.

Also, when setting a holding threshold, the hardness of the pick location can be measured instead of the hardness of the place location.

The holding threshold is preferably set based on the amount of objects piled up in bulk at the pick location. The bulk amount means the amount of multiple objects piled up in a loose state. If the bulk amount is large, when one of the multiple objects piled up is held by the suction unit 22, the object is more likely to collapse when pressed by the suction unit 22. For this reason, when the bulk amount is large, the holding threshold can be set to a small value to prevent the object from collapsing.

Effects of the embodiment
As described above, in the robot hand device 10 according to the embodiment of the present invention, when the object 35 held by the suction unit 22 is placed at a place location, the movable part 26 is displaced by the reaction force from the object 35, and the displacement amount of the movable part 26 is detected by the displacement amount detection unit 28. Then, the control unit 14 controls the suction unit 22 based on the displacement amount of the movable part 26 detected by the displacement amount detection unit 28. This makes it possible to release the object 35 held by the suction unit 22 at an appropriate timing. In addition, the release timing of the object 35 can be set with a simpler configuration than in the past. As a result, the impact given to the object 35 can be suppressed with a simpler configuration. In addition, it is possible to realize a robot hand device that can safely pick and place various objects at various locations with a simple configuration.

In addition, in this embodiment, the movable part 26 is configured to displace in the same direction as the reaction force received from the object 35. As a result, the amount of displacement of the movable part 26 is a value that directly reflects the reaction force received from the object 35 placed at the place location. Therefore, the release timing can be set with a simpler configuration.

<Modifications, etc.>
The technical scope of the present invention is not limited to the above-described embodiments, but also includes forms in which various modifications and improvements are made within the scope that can derive specific effects obtained by the constituent elements of the invention and their combinations.

For example, in the above embodiment, the suction unit 22 is given as an example of a holding unit, and a case has been described in which the suction unit 22 holds the object 35 by air suction, but the present invention is not limited to this, and the holding unit may hold the object by, for example, an electromagnet. Also, the gripping unit 24 may be configured to double as a holding unit.

10: Robot hand device 14: Control unit 22: Suction unit (holding unit)
24: gripping portion 26: movable portion 28: displacement amount detection portion 35: object

Claims (4)

A holder for holding an object;
a movable portion that is displaced by a reaction force received from the object when the object held by the holding portion is placed in a place location;
a displacement amount detection unit that detects a displacement amount of the movable portion;
a control unit that controls the holding unit based on the displacement amount of the movable unit detected by the displacement amount detection unit;
Equipped with
the control unit controls the holding unit to release the object when the object held by the holding unit is placed at the place location and the displacement amount of the movable unit detected by the displacement amount detection unit exceeds a release threshold value;
The release threshold is set based on the hardness of the place location.
Robot hand device. The robot hand device according to claim 1 , wherein the movable portion is displaced in the same direction as a reaction force received from the object. 3. The robot hand device according to claim 1, wherein the control unit controls the holding unit to hold an object placed at a pick location when the object is held by the holding unit and a displacement amount of the movable part detected by the displacement amount detection unit exceeds a holding threshold. The robot hand device according to any one of claims 1 to 3, further comprising a gripping section that grips the object to position the object.

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