WO2011144796A1

WO2011144796A1 - Robot hand mechanism

Info

Publication number: WO2011144796A1
Application number: PCT/FI2011/050088
Authority: WO
Inventors: Maciej Borkowski; Tuomas Lukka
Original assignee: Zenrobotics Oy
Priority date: 2010-05-19
Filing date: 2011-02-02
Publication date: 2011-11-24
Also published as: FI20105548A; FI20105548A0

Abstract

The invention relates to a robot hand (1) mechanism, comprising an actuator block with a plurality of fingers (4) for gripping objects, and a joint for attaching said actuator block (3) to a robot arm (2). In order to avoid permanent damage due to collisions said robot hand (1) mechanism comprises at least one component (21, 23) constructed in a way that allows a change in the shape of the robot hand mechanism such that the robot hand mechanism temporarily yields when a force exceeding a predetermined threshold is directed towards said robot hand mechanism, and said robot hand (1) mechanism comprises at least one sensor for triggering an emergency stop when said temporary yielding occurs.

Description

ROBOT HAND MECHANISM

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0001] This invention relates to a robot hand mechanism, and more precisely, to a robot hand mechanism capable of tolerating collisions.

DESCRIPTION OF PRIOR ART

[0002] Prior art robots have been designed to work in a predetermined environment, where the location of objects within the working range of the robot are known. In such an environment a goal is to obtain a robot capable of repeating a predetermined sequence of movements as precisely as possible.

[0003] Due to the fact that the locations of the objects is known, and that the robot is capable of avoiding them by repeating predetermined sequences of moments with high precision, the possibility of collisions has not received much attention in prior art solutions. Consequently, the design of prior art robots is such that collisions will cause significant damages to the robot.

[0004] Due to the above mentioned drawback, prior art robots are not suitable for use in an environment where the objects and the locations of the objects are not known in advance. In such an environment the robot hand will inevitably, sooner or late, collide with an object. If a collision takes place between a heavy and hard object, the result is permanent damage to the robot, and possibly to the object.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to solve the above mentioned drawback and to provide a robot hand mechanism which reduces the risk of permanent damage to a robot that is used in an unstructured environment with unknown objects. This object is achieved with robot hand mechanism according to independent claim 1 .

[0006] The use of a linear guide allowing a change in the shape of the robot hand mechanism by facilitating temporary yielding of the robot hand mechanism, when a force exceeding a predetermined threshold is directed towards the robot hand mechanism, in combination with a sensor triggering an emergency stop in such a situation, significantly reduces the risk of permanent damage to the robot. In this connection "temporary yielding" refers to a significant change in the shape of the robot hand mechanism, which cannot be obtained simply by ordinary elasticity of the materials used in the robot hand mechanism.

BRIEF DESCRIPTION OF DRAWINGS

[0007] In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which

[0008] Figure 1 illustrates an overall view involving a robot hand mechanism,

[0009] Figures 2 to 4 illustrate a first embodiment of a robot hand mechanism,

[0010] Figure 5 illustrates an attachment part and a linear guide,

[0011] Figure 6 illustrates a linear guide,

[0012] Figure 7 illustrates a second embodiment of a robot hand mechanism,

[0013] Figure 8 illustrates a third embodiment of a robot hand mechanism, and

[0014] Figures 9 to 12 illustrate alternative attachment parts. DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0015] Figure 1 is an overall view involving a robot hand mechanism. In Figure 1 it has been assumed by way of example that the robot hand 1 is supported by a robot arm 2 in a position where the robot hand 1 can be utilized for sorting waste material. In such a solution waste may be conveyed on an endless belt below the robot hand, and the robot hand is used for picking up objects among the waste and for dropping these objects in predetermined locations (bins or other endless belts) depending on the material of the object. In this way the waste can be sorted such that the same materials end up in the same locations. It should be noted, however, that a similar robot also may be employed for other purposes. [0016] A challenge in such an implementation is that the precise location of the objects on the belt are not known in advance and therefore the robot hand 1 may collide with unknown objects during use. In order to avoid permanent damage, the robot hand needs to be manufactured in such a way that collisions, irrespective of directions, do not damage the robot hand 1 or the robot arm 2.

[0017] The robot hand mechanism comprises an actuator block 3 with a plurality of fingers 4 for gripping objects. Such fingers 4 may be driven with pneumatic (or hydraulic) cylinders, as illustrated in Figure 1 by way of example, arranged in the actuator block 3. Alternatively, pneumatic muscles may be used, in which case the pneumatic muscles are used instead of cylinders. In any case the actuator block 3, the fingers 4 and other parts of the robot hand mechanism are preferably manufactured of an elastic material providing at least a certain amount of elasticity in the robot arm mechanism, which is advantageous to avoid permanent damage when collisions occur.

[0018] Figures 2 to 4 illustrate a first embodiment of a robot hand mechanism. The robot hand mechanism of Figures 2 to 4 may be employed in the robot of Figure 1 .

[0019] In Figures 2 to 4, the robot hand 10 is attached to the robot arm 2 via a joint that comprises at least one component constructed in a way that allows a change in the shape of the robot hand mechanism in such a way that the robot hand mechanism temporarily yields when a force exceeding a predetermined threshold is exerted on the robot hand mechanism. The threshold has been set to a level where permanent damage to the robot hand 10 or robot arm 2 can be avoided. In the embodiment of Figures 2 to 4 this at least one component is an attachment part 1 1 that attaches the robot hand 10 to the robot arm 2. When a collision occurs, the robot hand mechanism yields such that the attachment part 1 1 disengages from other parts included in the joint, in other words, the connection between the robot arm 2 and the robot hand 10 is released, and therefore the shape of the robot hand mechanism changes. The disengagement is, however, temporary, as once the object having caused the collision is no longer an obstacle to the robot hand mechanism, the attachment part 1 1 may again engage other parts of the joint in order to return the shape of the robot hand mechanism to be the same as before the collision. Preferably, the robot is capable of automatically detecting the position of the disengaged robot hand 10, to move the arm 2 to a correct position relative to the robot hand 10, and to allow the attachment part 1 1 to engage other parts of the joint. This can be accomplished by utilizing one of the attachment parts illustrated in Figures 9 to 12, for instance. Alternatively human intervention is needed in order for the robot hand mechanism to return to its original shape by engaging the disengaged parts to each other.

[0020] The robot hand mechanism of Figures 2 to 4 additionally comprises at least one sensor 12 for triggering an emergency stop when the temporary yielding occurs, in other words in this embodiment when the attachment part 1 1 disengages from other parts of the joint. This sensor 12 is connected to a control system of the robot which thereby receives information about when disengagement between the robot hand 10 and the robot arm 2 occurs. Additionally the robot hand mechanism may involve other sensors providing information from the robot hand mechanism to the control system. Such other sensors may, for instance, provide information about the size of the forces which at any particular moment are exerted on the robot hand mechanism. In this way the control system may make changes in the operation of the robot hand 10 when the 'pain' felt by the robot hand increases, in other words when the external forces exerted on the robot hand 10 reach a level where permanent damage may occur.

[0021] The embodiments of Figures 2 to 4 are different from each other regarding the direction from which the robot arm 2 engages with the robot hand 10. Such a difference is mainly caused by the intended use of the robot and the location of the robot with respect to the robot hand 10 during use.

[0022] Figure 5 illustrates an attachment part. The illustrated attachment part 21 may be utilized in the robot of Figure 1 for ensuring that the robot hand mechanism temporarily yields by changing shape of the robot hand mechanism, as has been explained in connection with Figures 2 to 4.

[0023] In Figure 5 two similar attachment parts 21 and 22 are in use in the joint between the robot hand 1 and the robot arm 2. The first attachment part 21 and the second attachment part 23 are arranged to engage in different directions to other components included in the joint. More specifically, the first attachment part 21 consists in this example of a horizontally (in the illustrated situation) arranged magnet, whose upper surface is permanently attached to the robot hand 1 , and whose lower surface by magnetic force is attached to a steel plate 22. The steel plate is another component included in the joint, and it is bent into an L-shape in the illustrated example. The second attachment part 23 consists of a vertically (in the illustrated situation) arranged magnet, whose left surface is permanently attached to the steel plate 22, and whose right surface is by magnetic force attached to a steel plate 24 in the robot arm 2. Therefore, in the illustrated embodiment, the first and second attachment parts are arranged to engage in directions which differ 90° from each other.

[0024] It is not necessary to utilize two attachment parts 21 and 23 in all implementations. However, the embodiment of Figure 5, with a first attachment part 21 allowing disengagement due to collision in the vertical direction (Z direction), and a second attachment part 23 allowing disengagement due to collision in the horizontal direction (X direction), lowers the risk of permanent damage to the robot hand 1 and the robot arm 2. Preferably the robot hand mechanism should allow change in the shape of the robot hand mechanism by yielding temporarily irrespective of the direction of the collision. Thus, any force applied on the robot hand 1 along any one of the three direction axes (X, Y or Z), or as a torque attempting to rotate the robot hand about any of the three axes, should result in temporary yielding by disengagement of the robot hand, for instance, rather than to permanent damage. Therefore, in some embodiments it is advantageous to use even more than two attachment parts (arranged to engage in different directions) in the joint between the robot hand 1 and the robot arm 2.

[0025] Figure 6 illustrates a linear guide. The linear guide 28 may be utilized in the robot of Figures 1 to 4, and in connection with the attachment parts 21 and 23 illustrated in Figure 5, for instance.

[0026] In Figure 6 a linear guide 28 is utilized as a component allowing a change in the shape of the robot hand mechanism such that the robot hand mechanism temporarily yields. Such a linear guide 28 may include a rail 26 or a groove with a sliding component 27, that is allowed to slide along the rail 26 or groove. The linear guide 28 may be implemented in the joint between the robot hand 1 and the robot arm 2 such that one of the rail 26 or sliding component 27 is attached to the robot hand 1 and the other one to the robot arm 2, as has been illustrated in Figure 5.

[0027] When a collision occurs, the sliding component 27 slides along the rail 26 or groove such that the forces acting on the robot hand 1 and the robot arm 2 do not cause any permanent damage, but instead the shape of the robot hand mechanism is temporarily changed by yielding provided by the linear guide 28. The linear guide 28 may include a spring, for instance, that returns the sliding component 27 to its original position once the object having caused the temporary yielding is no longer within the range of the robot hand.

[0028] In order to detect temporary yielding to an extent that requires an emergency stop, the robot hand mechanism also comprises a sensor 12. In the illustrated example it has been assumed by way of example that the sensor 12 triggers an emergency stop once the sliding component 27 has moved sufficiently to come into contact with the sensor 12. One alternative is that said sensor 12, or an additional sensor arranged to the robot hand mechanism, is a linear displacement sensor. Such a sensor will indicate the size of the linear movement, in other words the distance the sliding component 27 has travelled as compared to an initial position. This makes it possible for the robot to detect a situation where the forces exerted on the robot hand mechanism are increasing and to react accordingly in order to avoid an emergency stop or damages.

[0029] In the example of Figure 6 it has been assumed by way of example that the linear guide 28 is used in combination with the attachment parts 21 and 23 described in connection with Figure 5. In practice, this is an efficient combination. However, in some implementations it is possible that the linear guide 28 alone, without any of the illustrated attachment parts 21 or 23, is utilized in the joint between the robot hand 1 and the robot arm 2.

[0030] Figure 7 illustrates a second embodiment of a robot hand mechanism. The embodiment of Figure 7 differs from the previous embodiments regarding the location of the first and second attachment parts 21 and 23.

[0031] In Figure 7 the first and second attachment parts 21 and 23 are not arranged in the joint between the robot hand 30 and the robot arm, but instead, into the actuator block 3. The first and second 21 and 23 attachment parts are in Figure 7 used for attaching the upper ends of the actuators 31 , such as pneumatic cylinders, to an upper plate 32 included in the actuator block 3. If a collision occurs where one of the fingers 4 is subjected to a force that exceeds a predetermined threshold, then this force will cause the attachment part attaching the upper end of the actuator of this finger to the plate 32 to disengage from the actuator. Consequently, the shape of the robot hand mechanism changes as the robot hand mechanism temporarily yields. Once the object having caused the collision is no longer present, the actuator can again be attached to the attachment part, which will restore the shape of the robot hand mechanism, and the operation of the robot can continue. Sensors 12 for triggering an emergency stop can be arranged in connection with the attachment parts or actuators 31 , for instance.

[0032] Figure 8 illustrates a third embodiment of a robot hand mechanism. The embodiment of Figure 8 is very similar to the one explained in connection with Figure 7, and therefore the embodiment of Figure 8 will be mainly explained by pointing out the differences.

[0033] In Figure 8 the robot hand 40 comprises attachment parts arranged in connection with the lower plate 41 of the actuator block 3. These attachment parts 21 and 23 attach the actuator 31 and/or fingers to the lower plate 41 . In case of a collision, the attachment parts allow disengagement to occur, in order for the robot hand mechanism to yield, as has been previously explained.

[0034] Figures 9 to 12 illustrate alternative attachment parts. The illustrated attachment parts may be utilized in a joint between a robot hand and a robot arm in a actuator block to connect actuators or fingers to the actuator block, or in any other suitable position of the robot hand mechanism.

[0035] Figure 9 illustrates an attachment part 51 including a permanent magnet. In order to ensure attachment precisely in an intended mutual position and to prevent undesired rotation between the attachment part 51 and the opposite component 52, such as a steel plate, the attachment part is provided with protrusions that fit into the holes in the opposite component 52, once attachment occurs.

[0036] Figure 10 illustrates an attachment part 61 for mechanical attachment. In this case the attachment is carried out as a 'snap' attachment with the opposite component 62.

[0037] Figure 1 1 illustrates an attachment part 71 for magnetic attachment with an opposite component 73, such as a steel plate. However, in this case the magnet is an electromagnet, which is connected to a power source 72 in order to generate the necessary magnetic force for attachment. [0038] Figure 12 illustrates an attachment part 81 for vacuum attachment. Consequently a low pressure source 82, such as a compressor, is utilized for creating a suction that facilitates the attachment between the attachment part 81 and the opposite component 83, such as a plate.

[0039] It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.

Claims

CLAIMS:

1. A robot hand (1 , 10, 30, 40) mechanism, comprising: an actuator block (3) with a plurality of fingers (4) for gripping objects, and

a joint for attaching said actuator block (3) to a robot arm (2), characterized in that

in order to allow a change in the shape of the robot hand mechanism such that the robot hand mechanism temporarily yields when a force exceeding a predetermined threshold is exerted on said robot hand mechanism, said robot hand (1, 10, 30, 40) mechanism comprises at least a linear guide (28) included in said joint or in said actuator block (3) for allowing a linear movement of at least the fingers (4) in relation to said robot arm (2), such that said yielding comprises linear movement of at least the fingers (4) in relation to said robot arm (2), and

said robot hand (1, 10, 30, 40) mechanism comprises at least one sensor (12) arranged in connection with said linear guide (28) for triggering an emergency stop when a linear movement of a predetermined length has occurred.

2. The robot hand mechanism according to claim 1, characterized in that

in order to allow temporary yielding, said robot hand mechanism additionally comprises an attachment part (11,21, 23, 51,61,71,81) included in said joint, and

said yielding comprises disengagement of said attachment part (11 ,

21, 2351, 61, 71, 81) from other components (22, 52, 62, 73, 83) included in said joint.

3. The robot hand mechanism of claim 2, characterized in that said attachment part (61) attaches the robot arm (2) and the actuator block (3) to each other by a snap attachment.

4. The robot hand mechanism of claim 2, characterized in that said attachment part (51, 71) attaches the robot arm (2) and the actuator block (3) to each other by a magnetic attachment.

5. The robot hand mechanism of claim 2, characterized in that said attachment part attaches (81) the robot arm (2) and the actuator block (3) to each other by a vacuum attachment.

6. The robot hand mechanism according to one of claims 2 or 5, characterized in that said joint comprises a second similar attachment part (23), said attachment part (21) and said second attachment part (23) are arranged to engage in different directions to other components (22) included in said joint.

7. The robot hand mechanism according to one of claims 1 to 6, characterized in that

in order to allow temporary yielding, said robot hand mechanism additionally comprises an attachment part (21, 23) included in said actuator block (3) for attaching at least one of said fingers (4) or at least one actuator (31 ) for moving a finger (4) to said actuator block (3), and

said yielding comprises disengagement of said at least one finger

(4) or said at least one actuator from said actuator block (3).

8. The robot hand mechanism according to one of claims 1 to 7, characterized in that the actuator block (3), the plurality of fingers (4) or the joint is manufactured at least partly of an elastic material allowing elastic displacement of at least some of the parts of the robot hand (1 , 10, 30, 40) mechanism.

9. The robot hand mechanism according to claim 8, characterized in that said sensor (12) or an additional second sensor arranged in connection with said linear guide is a linear displacement sensor indicating at all times the size of said linear movement.