The present invention relates to the field robotics. More particularly, the present invention relates to a gripping device having numerous degrees of freedom with few actuation components.
Conventional mechanical grippers use several “fingertips” that can be either rigid or non-rigid and retract or extend upon an object to form a grasp. These fingertips use contact forces to apply a wrench (force and torque) to the object, allowing it to be grasped and manipulated. Robust grasps overcome external wrenches applied to the grasped object, including gravity, inertial forces and environmental disturbances. Depending on their geometry and mode of operation, each fingertip can have a number of Degrees of Freedom (DOF). For instance, a cylindrical fingertip that moves in a plane has two degrees of freedom (i.e. x and y coordinates). A fingertip can have up to 6 DOF in 3D space. For example, if a 4 fingered robotic hand has 6 DOF for each fingertip, the fingertip's placements are a 24 DOF state.
Typically, a gripping device has the same number of actuators (e.g. motors) as DOFs. If a robotic gripping device has 3 fingertips with 4 DOF each, the gripping device contains 12 actuators to control the individual DOFs. A device with fewer actuators than DOFs is often termed under-actuated. These devices often use compliance to reduce the number of actuators. However, under-actuated devices cannot fully control all DOFs in the device. Rather, under-actuated devices are situational, and often non-deterministic.
Typical grasping devices with few actuators entail simplicity of a robotic hand. On the other hand, numerous actuators enable providing more DOFs, consequentially providing a better grasp of the grasped object. It has been an ongoing challenge to obtain gripper devices having the capability of providing a good grasp but with few actuators, as multiple actuators entail complexity of the gripper device, increase of the grasping device weight and increase of the grasping device construction costs and maintenance costs.
It is therefore an object of the present invention to provide a method and means for grasping and manipulating objects using numerous DOF of the fingertips of a gripper device hand, using substantially fewer actuators than the DOFs.
It is a further object of the present invention to provide a method and means for grasping and manipulating objects utilizing the grasping arm environment to adjust the grasping function.
Other objects and advantages of the present invention will become apparent as the description proceeds.
The present invention relates to a device, system and method for grasping an object. The present invention provides a lower number of actuators in relation to the DOFs that it is capable of carrying out. The present invention relates to a grasping hand comprising angularly displaceable fingers, each comprising linearly displaceable fingertips (to engage and grasp the object to be maneuvered). Angularly displacing the fingers and linearly displacing the fingertips may be carried out through various stages prior to grasping the object and in preparation for grasping the object. In this way, the gripper hand may be adjusted prior to the grasping and restructured one DOF at a time.
The present invention relates to a robotic grasping hand comprising:
Preferably, the palm comprises:
Preferably, each fingertip comprises a grasping member extending vertically downwards.
Preferably, each finger comprises a proximal vertical surface near its proximal end and a distal vertical surface near its distal end;
Preferably, the lead screw passes through the proximal vertical surface and the distal vertical surface;
Preferably, the upper housing plate bottom portion comprises a peripheral channel placed around the first face gear;
Preferably, said hand further comprises a thumb finger connected to the palm;
Preferably, the hand further comprises a central shaft anchored to the upper housing plate and lower housing plate;
Preferably, the distal driving member is a distal plunger surface.
Preferably, said hand further comprises a motor configured to drive and rotate the first or second face gear.
Preferably, the motor is configured to drive and rotate the shaft.
Preferably, the palm is connected to a flat surface and rotatable thereon;
Preferably, said hand comprises:
Preferably, said hand further comprises a bearing member comprising a second follower element;
Preferably, said hand comprises a distal vertical bearing surface and a proximal vertical bearing surface; wherein said hand comprises one or more secondary rods that pass through the bearing member and that are fixed between said proximal vertical surface and said distal vertical surface.
Preferably, the hand comprises an axel extending proximally from the third motor and connected to the engaging member such that said third motor is configured to rotate said axel and thereby said engaging member.
Preferably, the distal driving element comprises a protrusion compatible with the engaging member.
Preferably, the engaging member is a universal socket.
Preferably, said hand (e.g., hand 300 explained herein) comprises:
The present invention relates to a system for manipulating an object comprising:
The present invention relates to a method for grasping and manipulating an object comprising:
Preferably, adjusting the hand further comprises the following pre stages:
Preferably, providing the hand with the motor configured to drive and rotate the shaft (e.g., hand 100 explained herein);
Preferably, providing the hand with the motor configured to drive and rotate the shaft (e.g., hand 100 explained herein);
Preferably, (providing a hand e.g. hand 200, 300);
Preferably, (providing a hand e.g. hand 200, 300);
Preferably, (providing a hand e.g. hand 200, 300);
The present invention is illustrated by way of example in the accompanying drawings, in which similar references consistently indicate similar elements and in which:
The present invention relates to a gripping system and method for gripping and manipulating objects.
Particularly, the present invention relates to a gripping system and method that includes:
The present invention is advantageous as it improves upon fully-actuated grippers by reducing the number of actuators needed to control the gripper's DOFs. On the other hand, the present invention is advantageous as it improves upon under-actuated grippers by allowing full control of the gripper DOF's without sacrificing determinism.
The present invention enables use of fewer actuators in the gripping system hand device than the hand device DOF. Full freedom is achieved by augmenting the hand device with sequential adjustments of the gripping hand device prior to gripping an object. The adjustments of the hand device change the hand device structure, so that it grips the intended object in the intended manner when actuated.
This allows the gripping hand device to contain a small number of actuators relative to the hand device DOFs, which reduces weight and cost of the hand device, while simultaneously allowing more robust gripping capabilities by permitting high numbers of DOF.
The present invention is applicable to all manners of object manipulation (such as lifting, pulling and pushing), tool operation, bin-picking and packing operations. The present invention is also applicable to fixturing applications, where the gripper is adapted to fix a specific object.
The present invention system relates to a robotic hand. The robotic hand comprises a central hub (also referred to as “central palm” interchangeably). The robotic hand comprises a plurality of fingers, each connected to and extending from the central palm. Each finger comprises a fingertip drivable thereon. The robotic hand may be rotated by a robotic arm (according to one embodiment) or a dedicated actuator (according to another embodiment). According to a preferred embodiment, the plurality of fingers are all placed on an imaginary common plane, but other embodiments may include fingers not necessarily on the same plane.
As there are several objects to be manipulated that vary in size and shape, for a specific object, the fingertips need to be placed at specific locations along the fingers and at certain angles one from another, in order to retract on the specific object to grasp and manipulate it. Changing the configuration of the device hand comprises replacing the location of the fingertips such that they will be configured to grasp a specific object when retracted. The replacing of the fingertips location comprises:
To grasp an object, the object is first photographed (e.g. by a camera placed viewing an assembly line, or a camera on the robotic hand itself, or a camera on another external item, etc.). The present invention system comprises a control unit (also referred to herein as controller) comprising a processor. The controller is connected to the camera (or is in a remote communication connection with the camera). The controller (e.g. a PC) is configured to obtain the image and perform analysis on the obtained image of the object, e.g. perform a series of image processing actions to the image, and obtain an approximation of the shape of the object (for example, a polygon resembling the peripheral circumference of the object). Then, the controller calculates the desired positions of the fingertips in order to grasp and manipulate the object (when the hand is positioned to a dedicated location above the object). For example, the controller randomly samples different finger placements on the object's shape approximation perimeter and selects points that provide grasps with the highest quality. For any given set of fingertip placements there are many hand configurations. The controller determinates and selects one configuration that is easy to change into. The controller may carry out these stages (e.g., determining shape, sampling, determining fingertip configuration, etc.) by using programs such as MATLAB. An example of an imager/camera of the present invention capable of imaging and transferring the image to the controller is: Webcam. E.g., Logitech HD Webcam C270.
The robotic hand configuration is altered both in fingertip distance from the palm and finger angle relative one to another. Once the desired hand configuration is achieved the robotic hand can be used to grasp the object and manipulate it. This concept enables to adapt the hand to an object without sacrificing reliability.
In cases where several objects of the same shape are needed to be manipulated (e.g. a plurality of identical components on a manufacturing conveyer line) the system may be synced for grasping each of the identical components and the grasp and manipulation is just a matter of opening and closing the fingers without adjusting the system (of course the hand may be positioned and rotated such that the fingertips will be in the correct configuration for grasping). This is because a single actuator drives all of the fingertips to the same extent, inwards (proximally) or outwards (distally).
When a new object component is introduced, the system recognizes the need for a structure change. A new image is captured, a shape approximation (e.g., polygon) calculated, etc., and the robotic hand structure is rearranged (adjusted, reoriented) accordingly.
The upper housing plate 110u comprises a face gear 110uf placed within a recess within the upper housing plate 110u, wherein the face gear 110uf is capable of rotating within the recess (see
The face gears 110Lf and 110uf are connected to the housing plates 110L and 110u respectively, by means of roller bearings therein (wherein the face gears 110Lf and 110uf are placed within the roller bearings that are placed within a dedicated recess within the respective plates 110L and 110u).
According to an embodiment of the present invention, the robotic hand 100 comprises a motor 101 (shown in
The face gear 110uf is connected to the motor via a shaft 180 and key 185. The shaft 180 is placed at the center of palm 110 (passing through corresponding central bores within face gears 110uf and 110Lf). The shaft 180 is anchored to housing plates 110u and 110L through thrust bearings 181 and 182 respectively. The shaft comprises a top surface 180t (preferably having a disc form wider than the shaft 180 center) resting on thrust bearings 181. The shaft comprises a bottom surface 180b (preferably having a disc/plate form wider than the shaft 180 center) beneath thrust bearings 181 and engaging thrust bearings 181. The bottom surface 180b may be an independent item having a plate form connected to the shaft 180 main body portion by means of bolts (said plate prevents the bottom thrust bearing 181 from moving along the shaft axis). The thrust bearings 181, 182 are placed within respective recesses within the respective housing plates 110u and 110L. The thrust bearings 181, 182 enable the rotation of shaft 180 with low friction.
The spinnable axel 101a is rigidly connected to shaft 180. According to one embodiment the spinnable axel 101a is rigidly connected to shaft 180 by means of bolts. According to another embodiment, the spinnable axel 101a comprises one or more side protrusions protruding sideways therefrom into corresponding complementary recesses within shaft 180. In any case, the connection between shaft 180 and axel 101a is firm such that when axel 101a rotates, it causes shaft 180 to rotate accordingly. The shaft 180 is connected to face gear 110uf by means of a shaft and key mechanism shown in
According to an embodiment of the present invention, upper connection plate 105 is connected to the motor 101 (e.g., by bolts). The motor 101 is connected to upper housing plate 110u (e.g., by bolts).
The thumb finger 120 and movable fingers 130 are all placed on an imaginary common plane. Fingers 130 are angularly displaceable on the imaginary common plane. More specifically, the fingers' 130 central lead screws 135, explained hereinafter, are all placed on a common imaginary plane and the lead screws 135 of the movable fingers 130 are angularly displaceable on the imaginary plane. The thumb finger 120 is stationary, i.e., it is not angularly displaceable. The thumb finger 120 and movable fingers 130 extend radially from the palm 110.
For obtaining a better understanding of the present invention, the fingers will be explained as follows. For each single finger (120, 130) the proximal direction is the horizontal moving direction when closing on an object to be grasped, i.e. the direction towards the center of palm 110. The distal direction is opposite to the proximal direction, i.e. the direction away from the center of palm 110.
According to a preferred embodiment, each of the fingers comprises a lead screw and follower mechanism. Each finger (120, 130) comprises a rotatable lead screw 135 along its length. The fingertips 170 each comprise an upper follower vertical surface member 170f and lower object engaging/grasping member 170g (configured to engage and then grasp, the object to be manipulated). The lower object engaging/grasping member 170g extends vertically downwards from the upper follower vertical surface member 170f. Optionally, an intermediate surface 170i attached to and between both the lower object engaging/grasping member 170g and the upper follower vertical surface member 170f, provides a distance offset between them. In
The lead screw 135 passes through the upper follower vertical surface member 170f via a follower element. The follower element and the lead screw 135 form the lead screw and follower mechanism. Each finger (120, 130) comprises a proximal vertical surface 150 near its proximal end and a distal vertical surface 160 near its distal end (wherein the lead screw 135 passes through both via an aperture passageway). Each finger (120, 130) preferably comprises one or more rods 171 fixed between proximal vertical surface 150 and distal vertical surface 160. The one or more rods 171 also pass through the upper follower vertical surface member 170f. The upper follower vertical surface member 170f is movable between the proximal vertical surface 150 and the distal vertical surface 160 by the lead screw and follower mechanism.
The two rods 171 provide structural support and torque resistance (e.g., preventing fingertip 170 from rotating). The rods 171 are rigidly attached to proximal vertical surface 150 and distal vertical surface 160, creating a rigid rail. The upper follower vertical surface member 170f comprises linear bearings therewithin such that the rods 171 that pass therethrough slide along the linear bearings. The upper follower vertical surface member 170f houses the follower element, i.e. a screw follower (a nut) that is rigidly attached to it, so that when the lead screw 135 rotates inside the follower it forces the follower vertical surface member 170f (and thus the entire fingertip 170) to move linearly (distally or proximally depending on the rotation direction) along the respective finger 120, 130, lead screw 135 and rails 171.
The upper housing plate 110u bottom portion comprises a peripheral channel 110uc (preferably circular) placed around the face gear 110uf (see
The lead screw 135 of each finger passes through the proximal vertical surface 150. The rotatable lead screw 135 comprises a spur gear 136 fixedly attached to its proximal side (placed proximally to the proximal vertical surface 150). The spur gear 136 meshes with face gear 110uf and with face gear 110Lf, such that when face gear 110uf rotates it causes spur gear 136 (and thus lead screw 135) to rotate (it causes the lead screws 135 of all of the fingers to rotate). Face gear 110Lf rotates in the opposite direction of face gear 110uf accordingly. When lead screw 135 rotates in a certain direction, the fingertip 170 moves distally. When lead screw 135 rotates in the opposite direction, the fingertip 170 moves proximally. The system is structured such that the face gear 110uf causes the lead screws 135 (of all of the fingers) to always rotate in the same direction and thus all fingertips 170 move proximally at the same time, or all fingertips 170 move distally at the same time. The motor is configured to rotate face gear 110uf in both directions, and thus cause fingertip 170 to either move distally or proximally. The motor is connected to the system controller and when adjusting the hand (or grasping an object) the controller causes movement of the fingertip 170 according to the requested action.
The two movable fingers 130 each comprise a plunger mechanism incorporated with a “clutch” mechanism. The lead screw 135 comprises a distal driving element 161 (which is a distal plunger surface, also referred to herein as “distal plunger surface 161”) fixedly attached to its distal side (see
As said, in a normal state, the fingers are in a mode such that the spur gear 136 meshes with face gear 110uf and with face gear 110Lf. However, when an external force pushes the distal plunger surface 161 proximally, it causes the entire lead screw 135 and thus spur gear 136 to move proximally. This causes the spur gear 136 to move proximally within the interior of face gears 110Lf and 110uf (decoupling from the state of meshing with them) such that spur gear 136 no longer meshes with face gears 110Lf and 110uf. In this manner, fingers 130 may be angularly displaceable. When the external force ceases, the plunger spring 162 pushes the distal plunger surface 161 distally (and thus lead screw 135 distally) and thus the spur gear 136 remeshes with face gear 110uf and with face gear 110Lf. Preferably, the spur gear 136 (shown in
The thumb finger 120 may not comprise the plunger mechanism, as it is sufficient that the fingertips may be placed in any configuration with moving the fingertips and angularly displacing fingers 130 only. Also, the angles between the fingers may be calculated in relation to thumb finger 120. Therefore, thumb finger 120 may just terminate at its distal vertical surface 160. According to one embodiment, an optical rotary encoder 165 is attached to the distal side of distal vertical surface 160. Thus, the spur gear 136 of thumb finger 120 always remains meshing with face gear 110uf and with face gear 110Lf. It should be noted that all of the portions in thumb finger 120 proximal to distal vertical surface 160 may be the same as in movable fingers 130.
This configuration is very advantageous as it enables to displace the fingertips 170 to be in the required location prior to grasping. For example, in a Polar Coordinate System three fingertips 170 can be placed at any required location on the Polar Coordinate System.
In the following example,
All of the adjusting stages are controlled by the controller. At first, the plunger mechanism of finger 130b is applied and disengages the spur gear 136 from meshing with the face gears 110Lf and 110uf. This is carried out by the system arm connected to the hand 100 at upper connection plate 105. The system arm manipulates the hand 100 and pushes the distal plunger surface 161 of finger 130b towards an environment item (e.g. a wall, the system arm body) compressing its distal plunger surface 161 inwards disengaging the spur gear 136 from meshing with the face gears 110Lf and 110uf. The motor is activated and drives the fingertips 170 of thumb 120 and finger 130b from distance 10 to distance 6.
The angular calculation shifting between the fingers herein is calculated in relation to the thumb finger 120 (the entire hand may angularly change in the process but the relative angles between the fingers remains unless shifted by the plunger).
Then the system arm rotates upper connection plate 105 (and thus entire hand 100) clockwise by 20 degrees. As the plunger system of finger 130b is pressed, the finger 130b stays in place and the angle between it and thumb 120 enlarges to 260 degrees. Then, the arm pushed the hand 100 away from the environment item and the plunger mechanism returns the finger 130b back to normal. The spring expands and pushes its corresponding distal plunger surface 161 distally, thus the spur gear 136 remeshes with face gear 110uf and with face gear 110Lf. The system then retracts all three fingertips 120, 130a and 130b by two distances, i.e. from distances 6, 6 and 10 respectively to distances 4, 4 and 8 respectively.
Then, the system arm manipulates the hand 100 and pushes the distal plunger surface 161 of finger 130a towards an environment item (e.g. a wall, the system arm body) compressing its distal plunger surface 161 inwards disengaging the spur gear 136 from meshing with the face gears 110Lf and 110uf. The motor is activated and drives the fingertips 170 of thumb 120 and finger 130b from distances 4 and 8 respectively to distances 5 and 9 respectively.
Then the system arm rotates upper connection plate 105 (and thus entire hand 100) counterclockwise by 60 degrees. As the plunger system of finger 130a is pressed, the finger 130a stays in place and the angle between it and thumb 120 lessens to 60 degrees (120−60=60). Then, the arm pushed the hand 100 away from the environment item and the plunger mechanism returns the finger 130a back to normal. The spring expands and pushes its corresponding distal plunger surface 161 distally, thus the spur gear 136 remeshes with face gear 110uf and with face gear 110Lf. Thus, the hand is in the position of
The present invention hand 100 may include embodiments with additional (or less) movable fingers 130, mutatis mutandis.
The following example particularly shows the clutch mechanism of the present invention.
In
In
The following example particularly shows the clutch mechanism of the present invention with a relative distance change of the fingertips 170.
In
In
Thus this embodiment provides a robotic gripping device hand 100 with a single actuator.
According to another embodiment, the present invention comprises a hand 200 comprising a palm 210 mounted on a flat surface 211 (e.g. a flat plate), as shown in
In this embodiment, there is no motor that spins the face gear 210Lf (and no elements connecting a motor to the central shaft, mutatis mutandis). The gears are driven in a different manner as will be explained herein. In this embodiment, there is no plate 105. In this embodiment, there are no elements connecting a motor to a central shaft.
As said, the finger elements of finger 230 are similar to those explained in relation to finger 130 (e.g. some embodiments do not necessarily have a plunger spring like element 162). The fingers 230 comprise a distal driving element 261 similar to the function of distal plunger surface 161 (but may have a structure that assists its rotation, as will be explained herein). The distal driving element 261 may comprise a hollow cylindrical element with an interior protrusion, or have a distal surface with means for connecting to an external manipulator for being manipulated (e.g. rotated, pushed, pulled). The driving element 261 is fixedly connected to the lead screw 235 and when it rotates, the lead screw 235 rotates accordingly.
The palm 210 of hand 200 is connected to surface 211 by being mounted on base 212 that is mounted on surface 211 (or it is mounted directly on surface 211). Hand 200 comprises three motors. The first motor 201 is mounted near palm 210 (e.g. on base 212 or directly on surface 211) configured to rotate palm 210 (with all its connected fingers). The motor shaft (e.g. rotor, axel extending therefrom) is rigidly attached to the housing plate 210u, such that when it spins it spins the housing plate 210u accordingly. The motor body is preferably rigidly attached to the base 212.
The second motor 202 is configured to linearly move an engaging member 265 distally or proximally. The engaging member 265 is configured to engage the distal driving element 261 and move it distally or proximally and also configured to rotate it.
Hand 200 comprises a horizontal lower descended surface 205 connected to surface 211 and substantially parallel to surface 211 (because
The third motor 203 is rigidly connected to bearing 204 (mounted thereon), and thus they are both traversed proximally or distally by motor 202. The third motor 203 is connected to engaging member 265 and configured to rotate and spin engaging member 265 in both directions (e.g., the engaging member 265 is connected to an axel extending proximally from motor 203 where motor 203 drives the axel and causes it to spin). Thus, motor 202 causes engaging member 265 to move distally and proximally and motor 203 causes engaging member 265 to rotate.
The motor 203 is mounted on bearing 204 at a location such that the engaging member 265 (connected to the spinning axel) may be aligned and engageable with driving element 261 of each finger 230.
The motor 202 is placed at a distance from palm 210 that is well greater than the length of the fingers 230 to enable bearing 204 (placed proximally from motor 202) to move distally and proximally. Motor 202 may be mounted on a vertical surface 215 extending vertically from surface 205.
Engaging member 265 is preferably a universal socket. The distal driving element 261 preferably comprises a protrusion compatible with the engaging member 265 (i.e. compatible with a portion of engaging member 265 e.g. the protrusion may be a hexagonal protrusion). When the engaging member 265 is pressed against the distal driving element 261 (e.g. engaging the hexagonal protrusion) it can rotate it. It moves the finger proximally by pushing it inwards (motor 202) against a coil spring (just like the plunger was pressed in the embodiment of finger 100). It moves the finger distally by retreating distally, allowing the coil spring to expand and return the finger to its default position. The default position is when the spur gear 236 distal portion 236d (thicker than the passageway that lead screw 235 passes through) engages the proximal side of proximal vertical surface 250 (i.e., the area around the passageway that lead screw 235 passes through; or an inner surface within a recess in proximal vertical surface 250 around the passageway that lead screw 235 passes through), similarly to as described in relation to distal portion 136d of hand 100, mutatis mutandis.
The motor 202 may linearly displace the bearing 204 such that the engaging member 265 may be in 3 positions. The first position is where the engaging member 265 is at its most distal position (furthest from palm 201). In this position the motor 201 may spin the palm 210 without the fingers colliding with engaging member 265 of fingers 230.
The second position is where the motor 202 has pushed bearing 204 and thus engaging member 265 proximally such that engaging member 265 connects to a specific finger distal driving element 261 (the specific finger referred to as the connecting finger). The connecting finger has previously been angularly displaced by motor 201 such that it is now pointed to the engaging member 265 (and aligned with the direction of the engaging member 265 extending from motor 203). In this position motor 203 spins the distal driving element 261 causing the spinning of lead screw 135 and thus of spur gear 236. The spinning of spur gear 236 that meshes with face gears 210Lf and 210Lc, causes face gears 210Lf and 210Lc to rotate (each at a different corresponding direction) which cause the other spur gears 236 of hand 200 to rotate. This activates the lead screw and follower mechanisms of all of the fingers in hand 200, which moves all of the corresponding fingertips 270 distally or proximally, depending on the spinning direction that motor 203 drives. All of the fingertips 270 move distally (away from palm 210) or proximally (towards palm 210) depending on the face gears rotation direction (where all of the fingers' spur gears 236 mesh similarly with the face gears 210Lf and 210Lc).
In the third position the motor 202 pushes the bearing 204 and thus engaging member 265 to its most proximal direction such that the connecting finger's spur gear 236 disengages from meshing with the face gears 210Lf and 210uf and is placed within the interior of the circular face gears 210Lf and 210uf. In this third position the connecting finger may be angularly displaced in relation to the other fingers. The engaging member 265 (pushing on driving element 261) holds the connecting finger in place while motor 201 rotates palm 210 (with all the other hand 200 fingers) until the required angle between the connecting finger and the other fingers, is achieved. Also, in this third position the motor 203 may spin the engaging member 265 which spins the connecting finger distal driving element 261 and moves only the fingertip 270 of the connecting finger distally or proximally. As the connecting finger spur gear 236 is not in a meshing position with the face gears, when the connecting finger lead screw 235 spins this affects only the connecting finger fingertip 270 positioning and not the positioning of the other fingertips 270 of hand 200. This third position enables the adjustment of the angle of the connecting finger (in relation to the other hand 200 fingers) and enables the adjustment of the position of the connecting finger fingertip 270 (in relation to the other fingertips). After the connecting finger angle adjusting and/or the position adjusting of the connecting finger fingertip 270 (in relation to the other fingertips) is completed, the engaging member 265 moves distally and the spring of the connected finger pushes the driving element 261 back distally and thus the lead screw 235 moves distally and the connecting finger spur gear 236 remeshes with face gears 210Lf and 210uf. Then the engaging member 265 moves further distally disengaging from the connecting finger distal driving element 261.
The engaging member 365 (that may be similar to engaging member 265 as explained herein) is engageable with the distal driving elements 361 of the fingers 330. The revolute joints enable the arm 350 to move the engaging member 365 distally and proximally, thereby enabling the displacing of the distal driving element 361 distally or proximally (thereby applying the plunger effect, etc.). the robotic arm comprises a rotatable segment 351 (its rotating joint 352 that it is connected to enables it to rotate). This enables the engaging member 365 to rotate (at a certain position) and thereby enables rotating the distal driving element 361, the corresponding lead screw, driving the corresponding fingertips distally/proximally, as explained in detail herein, mutatis mutandis. In other embodiments, an internal motor (e.g., within the segment that the engaging member 365 is connected to) may rotate the engaging member 365, mutatis mutandis. Other segment joint connections may also be carried out (e.g., telescopic mechanism, pneumatic or electric cylinder approach, etc.).
The motor 201 may be for example a Dynamixel PM 54 servo motor. The motors 202, 203 may be for example a DC brushed motor with a gear reduction. The motor 101 driving the face gear 110uf in hand 100 may be for example a NEMA 17 stepper motor.
The lead screw 135, 235 length is preferably between 220 and 400 mm. Its diameter is preferably between 8 and 12 mm.
The rods' 171, 271 lengths are preferably between 210 and 380 mm. Their diameters are preferably between 6 and 12 mm.
The distal plunger surface 161 and distal driving element 261 have a diameter preferably between 10 and 60 mm. Their thickness is preferably between 3 and 10 mm. The coil spring 162 has a diameter preferably between 10 and 50 mm.
The distal vertical surface 160, 260 has a length preferably between 10 and 40 mm. Its width is preferably between 20 and 50 mm. Its thickness is preferably between 10 and 30 mm.
The proximal vertical surface 150, 250 has a length preferably between 15 and 40 mm. Its width is preferably between 20 and 50 mm. Its thickness is preferably between 10 and 50 mm.
The upper follower vertical surface member 170f, 270f has a length preferably between 20 and 50 mm. Its width is preferably between 20 and 50 mm. Its thickness is preferably between 10 and 40 mm.
The lower object engaging/grasping member 170g, 270g has a length preferably between 10 and 100 mm. Its diameter is preferably between 3 and 30 mm.
The intermediate surface 170i, 270i has a thickness preferably between 3 and 10 mm.
The upper housing plate 110u, 210u and lower housing plate 110L, 210L have a diameter preferably between 60 and 240 mm. Their thickness is preferably between 20 and 70 mm.
The circular face gears 110uf, 110Lf, 210uf, 210Lf, have a diameter preferably between 70 and 200 mm. The lengths of their meshing teeth are preferably between 10 and 30 mm.
The diameter of the spur gear 136, 236 is preferably between 10 and 40 mm. Its thickness is preferably between 30 and 60 mm.
The length of distal portion 136d, 236d is preferably between 0 and 40 mm. Its diameter is preferably between 6 and 36 mm.
The width of peripheral channel 110uc, 210uc is preferably between 3 and 10 mm. Its depth is preferably between 3 and 10 mm.
Top protrusion 150t, 250t and bottom protrusion 150b, 250b have a length preferably between 3 and 10 mm. Their thickness is preferably between 3 and 10 mm.
The upper connection plate 105 has a diameter preferably between 40 and 100 mm. Its thickness is preferably between 8 and 20 mm.
The engaging member 265 has a length preferably between 20 and 50 mm. Its diameter is preferably between 30 and 60 mm.
Surface 211 has a length preferably between 400 and 1500 mm. Its width is preferably between 400 and 1000 mm. Its thickness is preferably between 3 and 20 mm.
Lower descended surface 205 has a length preferably between 60 and 300 mm. Its width is preferably between 60 and 300 mm. Its height (distance from surface 211) is preferably between 50 and 250 mm. The lengths of surfaces 215, 208 and 209 may be along the width of surface 205. Their height is preferably within the range of between 40 and 100 mm.
The present invention system may comprise a power unit (not shown) electrically coupled to all of the motors, cameras, controller, etc., in the system, and configured to power them. Optionally, the power unit is electrically coupled to an external power source (e.g. external power socket). The controller is connected to all of the motors, cameras, and the other electric units in the system and is configured to activate them.
Other embodiments of the present invention may include other mechanisms (other than the lead screw and follower mechanism) for displacing the fingertips distally and proximally, for example, a cable driven mechanism, a telescopic mechanism, a pneumatic or electric cylinder approach, etc.
The present invention relates to a system for manipulating an object comprising:
The present invention method is explained hereinbelow, however, part of the present invention method has been explained hereinabove in conjunction with the description of the device/system explained hereinabove.
The present invention relates to a method for grasping and manipulating an object comprising:
Preferably, adjusting the hand further comprises the following pre stages (before the angularly displacing and before the linearly displacing):
Preferably, providing the hand 100;
Preferably, providing the hand 100;
Preferably, providing the hand 200;
Preferably, providing hand 200;
Preferably, providing hand 200;
The method may be carried out by hand 300 as explained in relation to hand 200, wherein displacing the engaging member proximally/distally is carried out by the corresponding arm 350 (revolute joints or other mechanisms-telescopic mechanism pneumatic or electric cylinder approach, etc.). Displacing the fingertip(s) (by rotating the distal driving member 261) may be carries out by rotating a corresponding segment or by means of an internal motor, etc., mutatis mutandis.
The present invention method portion of calculating angular positions of the fingers and linear positions of the fingertips for grasping may comprise the following possibility as explained in the following section. This section describes a novel approach for selecting a grasp configuration for an object. When using a non-configurable robot hand, any grasp configuration must conform to the hand shape. For instance, if an equidistant, three-fingered hand is used, only grasp configurations that constitute equilateral triangles may be considered. The present invention approach utilizes the reconfiguration ability of the hand to maximize grasp quality by relaxing the finger positioning constraints. A grasp configuration is defined as the fingertip placements on the object's perimeter. A hand structure is defined as a combination of the grasp configuration and the location of the hand's center. Although the hand allows total freedom in grasp configuration selection, physical constraints still exist, so not every hand structure is possible.
The decision process for finger placement—the grasp configuration is thereby examined. The object is given as a polygon in configuration space. i.e., the object has been represented as a polygon, and dilated by the radius of the fingertips. This means that any point on the boundary of the configuration-space object corresponds to a fingertip-object contact point. The friction coefficient between the fingertips and the object p is known, as is the number of fingers k. The grasp configuration is now chosen. To do this, a Monte-Carlo simulation of grasp configurations is used. The polygon perimeter is discretized as a set of points, each with its own location and normal direction. Then, k fingertips are randomly placed at different points on the polygon perimeter, and test the grasp quality. There are many grasp quality measures. This procedure grants the user the option to choose between wrench space sphere radius and grasp matrix ellipsoid quality measures, although any other quality measure can be used.
The grasp is evaluated, and its quality is marked according to the guidelines of the quality measure. If the grasp is found to be immobilizing, the grasp configuration enters a list of possible grasp configurations. After exhausting the user-defined number of grasp attempts, the list is sorted by grasp quality. A list of immobilizing grasp configurations, sorted by their quality is then obtained. While all of these grasps are immobilizing, the physical structure of the hand imposes another constraint; not all of these immobilizing grasp configurations are actually feasible. A candidate hand structure is feasible if a hand center exists for the given grasp configuration. Therefore, each grasp configuration can be examined to determine its potential as a feasible hand structure. Starting from the best grasp configuration in the list, it is tested to see if a hand structure can be synthesized, i.e., it is tested to see if a hand center point P exists with its fingers at the candidate grasp configuration. This test is performed by converting the physical hand limitations to three geometric constraints.
Consider the point P representing the center of the hand. The first physical limitation of P is angular. Two neighboring digits cannot be at angles less than δ apart.
This limitation can be described geometrically as two overlapping discs, shown in
∠({right arrow over (fi−P)},{right arrow over (fj−P)})=δ.
The set of points P that conform to this rule lie within the union of two overlapping discs. Each disc is bounded by fi and fj. Each point on the perimeter of either disc is such that
If the distance between fi and fj is di,j, then the radii of the two discs are:
The center of the hand, therefore, must lie within the area:
i,j=i,j1∪i,j2
1=∩i,j for 1≤i,j≤k,i≠j.
This constraint can be seen in
The second constraint is that the hand center P must lie within a circle of radius Lmax centered at each fingertip placement, where Lmax is the maximal extension of a fingertip. Therefore, the hand center must lie within the area A2:
Finally, the geometric constraints are combined to obtain the valid area for the hand center. Any point P in this area is a physically feasible placement for the hand center:
=1∩2∩.
Any point in A that allows a squeezing grasp of the object is valid, and as far as grasp quality they are identical. However, some hand center positions are better in other regards. Special centers that have certain advantages can be identified. For instance, a special center for three-fingered hands is the center of the circle defined by the three fingertip placements. This center has two advantages: 1) Each of the three fingertips is equidistant from the center. If the previous grasp configuration was also equidistant, the hand's distances adjustment procedure is exceedingly short. 2) If a triangle is defined by the three fingertip placements, it is noted that extending or retracting the fingertips maintains a similar triangle. Similar triangle formations can be used to compute caging regions on polygons, potentially increasing grasp reliability and robustness using caging grasps.
If the preferred hand center is not feasible, one prefers hand centers that require shorter adjustment procedures of the hand. Each hand center Pi corresponds with a hand structure
C
i=({right arrow over (θ)}i,{right arrow over (d)}i).
Starting from the hand's current structure, C0, each of the alternative structures, Ci, may take a different number of adjustments to achieve. Therefore, adjustment procedures for every structure is constructed. After synthesizing the adjustment procedure for each candidate hand structure, the hand center that requires the shortest adjustment procedure is chosen. At this point, a number of valid hand structures have been found.
While some of the embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of a person skilled in the art, without departing from the spirit of the invention, or the scope of the claims.
This application is a National Stage application of International Patent Application No. PCT/IL2021/050747, filed on Jun. 20, 2021, which claims priority to U.S. Provisional Patent Application No. 63/042,026, filed on Jun. 22, 2020, each of which is hereby incorporated by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/IL2021/050747 | 6/20/2021 | WO |
Number | Date | Country | |
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63042026 | Jun 2020 | US |