force sensing device

Abstract

A force sensing device for a robot finger comprises: a first segment having a first joint at a first end thereof; a second segment connected to the first segment via a second joint; a third segment connected to the second segment via a third joint; and a torque sensing device for sensing the torque at each joint when a force is applied to the third segment; wherein the first, second, and third joints are arranged in the same plane and in a triangular configuration.

Description

Technical Field

[0001] The present invention relates to a force sensing device, a method of determining force components of a contact force acting on a force sensing device, a robotic gripper comprising a force sensing device, and a robot comprising a robotic gripper. Background Art

[0002] In industries such as manufacturing, robotic devices comprising a robotic hand and a gripper arrangement (also referred to herein as a robot or robotic gripper) are known. A key capability of such robotic devices is generally their ability to manipulate a range of objects.

[0003] The contact forces generated by the interaction between a robotic gripper and an object can be determined by placing sensors within the robotic gripper's fingertips. However, such arrangements are limited because they can be complex (requiring a large number of force sensors to be deployed within the gripper's contact surface) or can only determine the normal component of the contact force acting on the robotic gripper.

[0004] It is an object of the present invention to provide a robotic gripper that alleviates or substantially alleviates the above mentioned problems. Summary of the Invention

[0005] According to an embodiment of the present invention, a force sensing device for a robot finger is provided, comprising: a first segment having a first joint at a first end thereof; a second segment connected to the first segment via a second joint; a third segment connected to the second segment via a third joint; and a torque sensing device for sensing the torque at each joint when force is applied to the third segment; wherein the first, second, and third joints are arranged in the same plane and in a triangular arrangement.

[0006] The present invention provides a force sensing device comprising three segments arranged in a triangular configuration and three associated joints. The torque at each joint is sensed by a torque sensing device. Advantageously, this arrangement allows the contact force at the third segment to be sensed, and the components of this force (normal and tangential to the surface of the third segment) to be determined along with the location of the contact force.

[0007] The torque sensing device may include an output for outputting torque data of the three joints to the control unit. In this way, the torque data can be used in combination with details of the joint geometry and the geometry of the contact surface of the third segment to determine the force component of the contact force acting on the force sensing device.

[0008] The torque sensing means may comprise a torque sensor associated with each of the first, second and third joints.Conveniently, each joint may be associated with a torque sensor so that the torque experienced at each joint can be accurately determined.

[0009] The torque sensors may be provided by force sensors located at a known distance from their associated joints. In one arrangement, channels may be provided through the force sensing device in the same plane as the joints, with each channel comprising a force sensor at one end of the channel and a joint at the other end.

[0010] The three joints of the force sensing device may be non-rotatable joints that are capable of limited bending and movement only in the presence of contact forces.

[0011] In an alternative arrangement, the first joint is rotatable. For example, the first joint can be the joint between the phalanges of the robotic gripper, or the joint between the base (palm) and phalanges of the robotic gripper. This arrangement would allow the entire phalange of the robotic gripper to operate as a force sensing device. The second and third joints in this arrangement might only be able to bend slightly, so that there is enough movement at the second and third joints to compress or stress the force sensor.

[0012] The third segment can be arranged to cover at least some of the other segments. Note that the force sensing device according to the present invention allows the calculation of the forces (normal and tangential components) acting on the third segment. Such calculations are possible due to the presence of three joints and their triangular arrangement. However, if the force contacts the first or second segment, there will not be a sufficient number of joints and torque data to resolve the force components. In order to provide a more efficient force sensing device, the third segment can be configured to cover the first and second segments so that the contact force always contacts the third segment, thereby allowing the force components to be decomposed. In a linear arrangement of the first, second and third segments, the third segment can be "folded" so that it covers the first and second segments.

[0013] The third segment can be surrounded by a cover that extends over the first and second segments, separated from the first and second segments by an air gap. This arrangement is an alternative to folding the third segment over the rest of the device. The cover is arranged to "shadow" the first and second segments so that contact with an object in the area of ​​these segments is actually made by the cover, resulting in all three joints experiencing a sensed change in torque.

[0014] The force sensing arrangement may include a fourth joint, and the torque sensing means may be arranged to determine the torque at the fourth joint, the fourth joint being located out of the plane of the first, second and third joints. Conveniently, providing an out-of-plane location at which torque can be sensed enables determination of force components acting out of the plane of the first, second and third joints.

[0015] According to one aspect of the present invention, a method for determining force components of a contact force acting on a force sensing device according to the above aspect of the present invention is provided, the method comprising: measuring the torque at each joint of the force sensing device when an object contacts the surface of a third segment of the force sensing device at the contact point; and determining the position of the contact point and the force components of the contact force based on the torque measurements.

[0016] The method may also include defining a contact point of a contact force relative to a joint in a triangular joint arrangement within the force sensing device; and defining a torque at each joint based on the force components of the contact force, the size of the triangular joint arrangement in the force sensing device, and the contact point of the contact force.

[0017] The force component may include a force component perpendicular to the surface of the third segment at the point of contact and a force component tangential to the surface of the third segment at the point of contact. When the force sensing device is incorporated into a robotic gripper, the ability to determine the tangential force component of the contact force enables such a robotic gripper to determine the weight of an object to be lifted by gripping the object and determining the tangential force exerted by the object when the gripper lifts the object.

[0018] Note that the order of the steps in the above-described method according to the present disclosure may vary slightly depending on the specific implementation of the method, for example, certain steps may occur together or in a different order than described above.

[0019] According to one aspect of the present invention, there is provided a robotic gripper comprising: a base; a first finger comprising a proximal phalanx connected to the base via a joint; a second finger comprising a proximal phalanx connected to the base via a joint; wherein at least one of the phalanxes comprises a force sensing device.

[0020] The force sensing device according to the present invention can be advantageously incorporated into a robotic gripper to enable the gripper to determine the forces generated on the gripper when gripping an object. Conveniently, the force sensing device can be incorporated into all potential contact surfaces of the robotic gripper, for example, each phalanx of the robotic gripper can include a force sensing device.

[0021] According to an aspect of the present invention, there is provided a robotic gripper according to the above aspect of the present invention, comprising a control unit configured to perform the method of the present invention.

[0022] Within the scope of the present application, it is obvious that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular individual features thereof, may be employed independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, unless such features are incompatible. The applicant reserves the right to amend any initially filed claim or to file any new claim accordingly, including the right to amend any initially filed claim to make it dependent on and / or combined with any feature of any other claim, even though not originally claimed in this manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] One or more embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0024] Figure 1 shows a side view of a robotic gripper including a force sensing device, the gripper being in an open configuration according to an embodiment of the present invention;

[0025] Figure 2 Shown Figure 1 A perspective view of the robotic gripper;

[0026] Figure 3 Shown in an alternative open configuration Figure 1 A perspective view of the robotic gripper;

[0027] Figure 4 Shows the clamping of the object Figure 1 A side view of the robot gripper;

[0028] Figure 5 Shows the clamping of the object Figure 1 A perspective view of the robotic gripper;

[0029] Figure 6 Shows the clamping of the object Figure 1 A plan view of the robot gripper;

[0030] Figure 7 a side view showing a third section of the force sensing device and the contact force;

[0031] Figure 8 is a flow chart illustrating calculation of force components of contact force according to an embodiment of the present invention;

[0032] Figure 9 A robot including a robotic gripper is shown. DETAILED DESCRIPTION

[0033] Hereinafter, general and specific embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, like numerals are used to represent like features.

[0034] Figure 1 A side view of a robotic gripper 10 is shown according to an embodiment of the present invention. The gripper 10 includes a base 12, a first finger 14 and a second finger 16.

[0035] The first finger 14 includes a first or proximal phalanx 18 connected to the base 12 by a joint 20. The second finger 14 includes a first (proximal) phalanx 22 connected to the base 12 by a (base) joint 24. The second finger 16 also includes a second (distal) phalanx 26 connected to the adjacent proximal phalanx 22 by a (phalangeal) joint 28. The first and second fingers (14, 16) are opposite each other.

[0036] like Figure 1 As shown, the base comprises a first inner surface 30 and a second inner surface 31 arranged at 90 degrees to each other. These inner surfaces (30, 31) of the base comprise a textured surface to aid in gripping an object. The surface may comprise, for example, a rubber material. The robotic gripper further comprises a wrist connection 32 to enable the gripper 10 to be connected to a robotic arm ( Figure 1 not shown).

[0037] Figure 1 The gripper 10 is shown in a fully open configuration, wherein the surface 30 of the base 12 and the inner surface 34 of the first finger 14 are parallel to each other. In addition, the first and second phalanges (22, 26) of the second finger 16 define a straight line parallel to the inner surface 31 of the base 12. Figure 1 As shown, the first finger 14 is at 90 degrees to the second finger 16 .

[0038] for Figure 1 The robotic gripper 10 shown has an odd number of joints (3 in this case) and an odd number of phalanges. The existence of hands with an odd number of phalanges in the opposing fingers results in a "manual" gripper 10, which enables the gripper's fingers to perform gripping and clamping actions as well as more complex actions, such as rolling an object between two opposing fingers.

[0039] Figure 2 Shown in perspective Figure 1 The holder 10. Figure 3 Another perspective view shows Figure 1 , wherein the gripper is in another “open” configuration wherein the second phalanx 26 of the second finger 16 is parallel to the phalanx 18 of the first finger 14 .

[0040] Each joint (20, 24, 28) can rotate around an axis. Figure 1As shown, the axes of each joint (20, 24, 28) are parallel to each other and perpendicular to the plane of the drawing. Each joint comprises its own motor, allowing the robotic gripper to be fully actuated, thereby facilitating the gripping positions that the gripper can adopt.

[0041] The motor for each joint can be directly associated with the joint. This arrangement will facilitate replacing the gripper connected to the wrist connection with a replacement gripper (in the event of damage) or an alternative robotic manipulator. Alternatively, the motor for each joint can be positioned away from the gripper 10 (e.g., in an arm attached to the gripper 10 by the wrist connection 32) and can be connected to the joint by a suitable mechanical or hydraulic tendon system. Compared to positioning the motor directly at each joint in the gripper, this arrangement can make the design volume of the gripper smaller.

[0042] The gripper may be rotated about the wrist connection to enable the gripper to move between a first manual position and a second manual position.

[0043] Figure 1 (as well as Figure 2 and Figure 3 Each finger (14, 16) of the robotic gripper shown in FIG. 1 is further provided with a force sensing device. As described below, the force sensing device can be used to identify the contact point location of a force acting on the robotic finger (e.g., from contact with an object). The force sensing device can also be used to determine the normal force and the tangential force (relative to the finger surface) of the force acting on the finger.

[0044] like Figure 1 As shown, the phalanx 18 of the finger 14 includes a base segment 40 (containing the joint 20) and a force sensing device 42 (located at the end of the phalanx 18 distal from the base 12). The force sensing device includes first, second, and third segments (44, 46, 48) arranged such that the first segment 42 is adjacent to the base segment 40 of the finger 14.

[0045] The first segment 44 includes a first joint 50 between the base segment 40 and the first segment 44. The second segment 46 is connected to the first segment 44 by a second joint 52. The third segment 48 is connected to the second segment by a third joint 54.

[0046] Note that joints 50, 52, and 54 are not rotational joints, and that the three segments 44, 46, and 48 are essentially fixed relative to one another. However, the segments are not completely immobile relative to one another, and when forces act on finger 14, the structure of finger 14 compresses or stretches slightly. Consequently, there is some slight relative motion between the three segments when the finger contacts an object.

[0047] The force sensing device 42 also includes a torque sensing device, which Figure 1This takes the form of three force sensors 56 (located between the base section 40 and the first section 44), 58 (located between the first and second sections (44, 46)), and 60 (located between the second and third sections (46, 48)).

[0048] like Figure 1 As shown, the joints (50, 52, 54) and force sensors (56, 58, 60) are located at opposite ends of a channel (62, 64, 66) extending perpendicular to the longitudinal axis of the finger 14.

[0049] The third section 48 is shaped so that it includes a covering portion 68 that partially covers the first section 44 and the second section 46. Figure 1 In FIG. 3 , it can be seen that the third section is folded so that the covering portion 68 covers the inner surface 34 of the first and second sections.

[0050] The first, second and third joints (50, 52, 54) are arranged in the same plane and are further arranged in a triangular arrangement. Figure 7 As discussed in detail, this arrangement of joints allows for determination of both the normal and tangential components of the force acting on the third segment 48 .

[0051] Finger 16 includes a force sensing device 42a that corresponds to the configuration of force sensing device 42 on finger 14. Corresponding features of force sensing device 42a are labeled (e.g., first, second, and third segments (44a, 46a, 48a), joints (50a, 52a, 54a), force sensors (56a, 58a, 60a), channels (62a, 64a, 66a), and cover portion 68a).

[0052] The output of the torque sensing devices in the force sensing devices 42 and 42a may be sent to a control unit (not shown) which may determine the force applied to the clamped object, as described below with respect to Figure 6 and 7 Further detailed discussion.

[0053] The control unit may further be configured to send control signals to a motor that controls the operation of the gripper 10 .

[0054] exist Figures 1 to 3 , force sensing devices (42, 42a) are shown at the tips of the fingers (14, 16).Alternative configurations of robotic fingers including force sensing devices according to embodiments of the present invention are possible.

[0055] For example, as shown in finger 14, force sensing device 42 is located at the end of phalanx 18, and the phalanx also includes base segment 40. In an alternative configuration, force sensing device 42 can extend across the entire length of phalanx 18. In such an alternative configuration, a separate first joint 50 may not be required, and base joint 20 may instead serve as part of force sensing device 42 (i.e., base joint 20 forms the "first joint" of force sensing device 42). In such a configuration, the first joint of first sensing device 42 is a rotatable joint, while second joint 52 and third joint 54 are substantially fixed as described above.

[0056] In a further alternative configuration, each phalanx of a robotic finger (eg, phalanxes 22 , 26 in finger 16 ) may include a force sensing device 42 .

[0057] Figure 4 and Figure 5 shows the interaction with the object 80 Figure 1 As can be seen from the figure, the object 80 contacts the cover portion (68, 68a) of the force sensing device (42, 42a).

[0058] Figure 6 Shown according to Figures 1 to 5 FIG. 8 is a side view of a gripper 10 holding an object 80 in a vertical grip. The figure shows the direction of gravity 82 and the weight 84 of the object 80. The contact force 86 from the gripper 10 acting on the object is also shown.

[0059] Figure 7 A simplified view of the gripper 10 is shown in order to illustrate the force f acting on the gripper 10 when the gripper interacts with an object. c The component (f cx ,f cy ).

[0060] Figure 7 The third section 48 of the force sensing device 42 is shown, along with the cover portion 68 and the first, second, and third joints 50 , 52 , 54 .

[0061] Likewise Figure 1 As shown, the three joints ( 50 , 52 , 54 ) of the force sensing device 42 are in the same plane (the drawing plane) and are arranged in a triangular configuration.

[0062] like Figure 7 As shown, the triangle formed by the three joints is isosceles or equilateral, with a base dimension of 2a and a height from the base (joints 50, 54) to the vertex (joint 52) ​​dimension b.

[0063] exist Figure 7In FIG, the x-axis is parallel to the longitudinal axis of the finger segment 48, the y-axis is perpendicular to the longitudinal axis, and the x-axis, the y-axis and the three joints (50, 52, 54) are in the same plane. With the joint 54 as the origin, the contact force 90 is located at (x p, h).

[0064] The torque at the non-rotational joint 50 measured by the force sensor 56 is τ1; the torque at the non-rotational joint 52 measured by the force sensor 58 is τ2; and the torque at the non-rotational joint 54 measured by the force sensor 60 is τ3.

[0065] The three torques caused by external forces can be expressed as:

[0066]

[0067] This can also be expressed as:

[0068]

[0069] Then the item It can be calculated:

[0070]

[0071] From this we can conclude that:

[0072]

[0073] Then the item It can be calculated:

[0074]

[0075] From this we can conclude that:

[0076]

[0077] Considering the calculated terms The expression of can be written as:

[0078]

[0079] At this stage of the calculation, and can be considered known. Then the equation for τ3 can be used to obtain x p , as shown below:

[0080]

[0081]

[0082] In the manner described above, the x and y components of the force fc acting on the third section 48 of the force sensing device and the contact point location of that force may be determined.

[0083] exist Figure 7 In the arrangement shown, the profile of the segments is constant because the top surface of the segment 48 (ie, f c The surface of action) is a horizontal straight line spanning the extent of the segment in the x-direction (in other words, the depth of segment 48 is a constant value h). Note, however, that the force could also be calculated for a different profile of the third segment, such as h(x)=mx+q (slope) or as a quadratic curve.

[0084] like Figure 7 As shown, the force f c Acting on the surface. If the force f c With a component acting in or out of the paper (i.e., in the z-axis direction, wherein the z-axis is perpendicular to the drawing plane), a fourth force sensor (not shown) may be mounted on the robot gripper 10 in order to determine the component f cz .

[0085] Figure 8 is a flow chart illustrating a process for determining the components of the contact force acting on the gripper 10 when the gripper interacts with an object.

[0086] In step 100 , the torque at each joint ( 50 , 52 , 54 ) of the force sensing device 42 is measured when the object contacts the surface of the third segment.

[0087] In step 102, the contact force f c The contact point 90 is defined relative to one joint in the triangular joint arrangement (as described above with respect to Figure 7 Discussion, the contact point is x p ,h).

[0088] At step 104 , the torque at each point is defined based on the force components of the contact force, the size of the triangular arrangement of joints in the force sensing device, and the contact point of the contact force.

[0089] At step 106, the force component of the contact force at the contact point can be determined from the measured torque value. Figure 7 As shown, the force component (f cx ,f cy ) can be defined entirely from known parameters (the dimensions of the triangular arrangement of joints) or can be measured (torque measurements at the three joints).

[0090] Figure 9 A robot 120 is shown, comprising an arm 122 and a Figures 1 to 7 The robotic gripper 10 of any of the Figures.

[0091] Many modifications may be made to the examples described above without departing from the scope of the present disclosure as defined by the appended claims.

Claims

1. A force sensing device for a robot finger, comprising: a first segment having a first joint at a first end thereof; a second segment connected to the first segment via a second joint; a third segment connected to the second segment via a third joint; a torque sensing device for sensing the torque at each joint when a force is applied to the third segment; The first joint, the second joint and the third joint are arranged in the same plane and in a triangular arrangement. The third section is arranged to cover the first section and the second section.

2. The force sensing device of claim 1, wherein: The torque sensing device comprises an output for outputting torque data of the three joints to a control unit.

3. The force sensing device according to claim 1 or 2, wherein: The torque sensing means includes a torque sensor associated with each of the first joint, the second joint and the third joint.

4. The force sensing device of claim 3, wherein: Each torque sensor includes a force sensor.

5. The force sensing device according to claim 3 or 4, wherein: Channels are provided through the device in the plane, and each channel includes a force sensor at one end of the channel and a joint at the other end of the channel.

6. A force sensing device as claimed in any one of the preceding claims, wherein: The first joint is rotatable.

7. The force sensing device according to any one of claims 1 to 6, wherein: The third section is surrounded by a cover arranged to extend over the first and second sections, the cover being separated from the first and second sections by an air gap.

8. A force sensing apparatus as claimed in any preceding claim, comprising a torque sensing means at a fourth joint, the fourth joint being out of the plane of the first, second and third joints.

9. A method of determining force components of a contact force acting on a force sensing device according to any one of claims 1 to 8, the method comprising: measuring a torque at each joint of the force sensing device when the object contacts the surface of the third segment of the force sensing device at the contact point; The position of the contact point and the force components of the contact force are determined from the torque measurement.

10. The method of claim 9, further comprising: defining a contact force relative to a contact point of one joint in a triangular joint arrangement within the force sensing device; The torque at each joint is defined based on the force components of the contact force, the dimensions of the triangular joint arrangement in the force sensing device, and the contact point of the contact force.

11. The method according to claim 10, wherein: The force components include a force component perpendicular to the surface of the third segment at the contact point and a force component tangential to the surface of the third segment at the contact point.

12. A robotic gripper comprising: base; a first finger comprising a proximal phalanx connected to a base by a joint; a second finger comprising a proximal phalanx connected to a base by a joint; Wherein at least one phalanx comprises a force sensing device according to any one of claims 1 to 8.

13. The robotic gripper of claim 12, wherein: Each phalanx includes a force sensing device.

14. A robotic gripper according to claim 12 or 13, comprising a control unit configured to perform the method according to any one of claims 9 to 10.

15. A robot comprising the force sensing device according to any one of claims 1 to 8 or the robot gripper according to any one of claims 12 to 14.

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