Double link slide block type coupling adaptive under-actuated robot finger device
Technical field
The invention belongs to the robot technical field, particularly a kind of structural design of double link slide block type coupling adaptive under-actuated robot finger device.
Background technology
Robot is as the indispensable part of robot, and with respect to other part of robot, robot has that joint freedom degrees is many, volume is little, characteristics and difficult points such as very dexterous, control complicacy.Robot is mainly used in grasping with spatial movement and do other hand motions such as gesture object.Though present existing Dextrous Hand control flexibly; But because its motor and number of sensors are many, its structure is very complicated, and the control difficulty is quite big; Manufacturing and maintenance cost are very high, and these factors have hindered Dextrous Hand humanoid robot hand in real-life wide popularization and application.Though fast-developing in recent years coupling is grasped the humanoid robot hand and is owed to drive the high flexibility ratio that extracting humanoid robot hand does not possess Dextrous Hand; But number of motors is few; Simple in structure, control greatly reduces manufacturing cost and use cost easily; And can better grasp familiar object, become the focus of development and research.
The parallel under-actuated device finger of existing a kind of doublejointed device; Like Chinese invention patent CN101633171A; Comprise pedestal, motor, nearly joint shaft, joint shaft far away and the end section of finger, also comprise transmission mechanism and a plurality of spring spare decoupling zero devices etc. realizing coupling respectively and owe to drive rotation.Before finger touches object, realize the effect of multi-joint coupled rotation, after finger touches object, adopt multi-joint to owe the type of drive grasping objects.The weak point of this device is: this device makes whole finger structure complicated owing to adopted two sets of transmission mechanism to realize coupling respectively and owe driving extracting, and it is high to make processing cost; This device coupled transmission mechanism with owe drive transmission device and influence each other, though adopted 3 spring spares to come decoupling zero, in-fighting the power of motor; Two sets of transmission mechanism of this device are arranged in parallel, and add a plurality of spring spares and on joint shaft, install, and cause finger too thick; Two sets of transmission mechanism of this device all adopt flexible drive parts, the easy loosening gap that produces, and transmission is accurate inadequately, realize good result, also needs pre-tightening apparatus, further increases manufacturing, installation and maintenance cost and difficulty.
Other has the parallel under-actuated device finger of a kind of doublejointed isomery device; Like Chinese invention patent CN101829994A; Comprise pedestal, motor, nearly joint shaft, joint shaft far away and the end section of finger, also comprise transmission mechanism and a plurality of spring spare decoupling zero devices etc. realizing coupling respectively and owe to drive rotation.Before finger touches object, realize the effect of multi-joint coupled rotation, after finger touches object, adopt multi-joint to owe the type of drive grasping objects.The weak point of this device is: near, the far away axle joint two of this device overlaps the transmission device isomeries, has increased the complexity of its structure; And isomery can cause two joint rotation angles can only in particular range, be similar to the 1:1 coupling, makes the rotation in axle far away joint be difficult to prediction, and the control difficulty increases.
Summary of the invention
The objective of the invention is in order to overcome the weak point of prior art, a kind of double link slide block type coupling adaptive under-actuated robot finger device is provided.This device can be realized the 1:1 coupled rotation and owe to drive the effect that rotation combines; Can realize the extracting that personalizes that is coupled to the full extent, and possess under-driven adaptive function, compact conformation; Stable drive is accurate; Manufacturing and maintenance cost are low, and profile is similar with finger, is applicable to anthropomorphic robot's hand.
The present invention adopts following technical scheme:
A kind of double link slide block type coupling adaptive under-actuated robot finger device of the present invention; Comprise pedestal, joint semiaxis, first refers to that section, joint shaft far away, second refer to section and motor in the vicinity; Described motor is arranged in the pedestal, and the output shaft of motor links to each other with joint semiaxis in the vicinity; Described joint in the vicinity half-axile sleeve is located in the described pedestal, and described joint shaft far away is set in first and refers in the section, and described second refers to that section is fixed on the described joint shaft far away; This double link slide block type coupling adaptive under-actuated robot finger device also comprises first dial, first connecting rod, first, second, first slide block, second slide block, second connecting rod, the 3rd, the 4th, second dial and the first spring spare; Described first refers to that section is fixed in the vicinity on the semiaxis of joint, and first refers to that section is set on the semiaxis of right nearly joint; Nearly joint, described right side half-axile sleeve is located on the pedestal, and right nearly joint semiaxis is with the joint semiaxis is coaxial in the vicinity, and the right nearly joint semiaxis and first dial are affixed, and described first dial is set on the semiaxis of left joint, and first dial and pedestal are affixed; The described first connecting rod and first dial are hinged through first, and the other end and first slide block are hinged through second; Described first slide block is embedded in first and refers in first chute of section, and second slide block is embedded in first and refers to that described first chute is parallel with second chute in second chute of section, and first slide block and the second slide block loose joint are touched; Described second connecting rod one end and second slide block are hinged through the 3rd, and the other end and second dial are hinged through the 4th; Described second dial is fixed on the joint shaft far away; The described first spring spare is arranged on first and refers to that section and second refers between the section and the two ends of the first spring spare refer to that with first section and second refers to that section is connected respectively, the perhaps described first spring spare be arranged on second slide block and first refer to section between and the two ends of the first spring spare section be connected with second slide block and first finger respectively.
A kind of double link slide block type coupling adaptive under-actuated robot finger device of the present invention; Comprise pedestal, joint semiaxis, first refers to that section, joint shaft far away, second refer to section and motor in the vicinity; Described motor is arranged in the pedestal, and the output shaft of motor links to each other with joint semiaxis in the vicinity; Described joint in the vicinity half-axile sleeve is located in the described pedestal, and described joint shaft far away is set in first and refers in the section, and described second refers to that section is fixed on the described joint shaft far away; This double link slide block type coupling adaptive under-actuated robot finger device also comprises right nearly joint semiaxis, first dial, first connecting rod, first, second, first slide block, second slide block, second connecting rod, the 3rd, the 4th, second dial, the first spring spare and the second spring spare; Described first refers to that section is fixed in the vicinity on the semiaxis of joint, and first refers to that section is set on the semiaxis of right nearly joint; The two ends of the described second spring spare connect first respectively and refer to section and joint semiaxis in the vicinity; Nearly joint, described right side half-axile sleeve is located on the pedestal, and right nearly joint semiaxis is with the joint semiaxis is coaxial in the vicinity, and the right nearly joint semiaxis and first dial are affixed, and described first dial is set on the semiaxis of left joint, and first dial and pedestal are affixed; Described first connecting rod one end and first dial are hinged through first, and the other end and first slide block are hinged through second; Described first slide block is embedded in first and refers in first chute of section, and second slide block is embedded in first and refers to that described first chute is parallel with second chute in second chute of section, and first slide block and the second slide block loose joint are touched; Described second connecting rod one end and second slide block are hinged through the 3rd, and the other end and second dial are hinged through the 4th; Described second dial is fixed on the joint shaft far away; The described first spring spare is arranged on first and refers to that section and second refers between the section and the two ends of the first spring spare refer to that with first section and second refers to that section is connected respectively, the perhaps described first spring spare be arranged on second slide block and first refer to section between and the two ends of the first spring spare section be connected with second slide block and first finger respectively.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention, the structural parameters of described first connecting rod, second connecting rod, first dial and second dial meet following relation: the length of establishing first connecting rod is L
1, the distance of the center line of the center line to the second of first dial spool is R
1If the length of second connecting rod is L
2, the distance of the center line that the center line to the of second dial is four is R
2, then: L
1: R
1=L
2: R
2=2.5~3.5: 1.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention, described joint shaft far away is made up of left side joint far away semiaxis and right joint semiaxis, and joint far away, described left side semiaxis is set in the first finger section with right joint far away semiaxis is coaxial.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention; Described first slide block touches mode with the loose joint of second slide block and adopts first slide block to contact with the second slide block single face, and described first slide block promotes the slippage in finger of second slide block.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention, described first slide block touch mode with the loose joint of second slide block and adopt rope to be connected, and described first slide block spurs the slippage in finger of second slide block.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention, described spring spare adopts stage clip, torsion spring or elastic threads.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention also comprises transmission mechanism, and described transmission mechanism comprises decelerator, first gear and second gear; The output shaft of described motor links to each other with input shaft of speed reducer, and described first gear is fixed on the output shaft of decelerator, and described second gear is fixed on the nearly joint shaft, described first gear and second gears engaged.
Double link slide block type coupling adaptive under-actuated robot finger device of the present invention, described second shoe surface is coated with the second slider table panel.
The present invention compared with prior art has the following advantages and the high-lighting effect:
Apparatus of the present invention are utilized double-crank slide block and spring spare comprehensively to realize coupled rotation and are owed to drive the transmission effect that rotation is combined closely; Not only can the 1:1 coupled rotation; Make it realize the grasping objects that personalizes to greatest extent; And possess and owe to drive function, the object of self-adapting grasping difformity, size; This device joint is taked identical transmission device, makes it make processing simply, and compactness simple for structure is installed easily; This device has been realized coupled transmission mechanism and has owed drive transmission device organically blending, and does not influence each other, and the multiple mode of utilizing the slide block loose joint to touch has realized natural decoupling zero, and this decoupling zero does not consume power of motor, and capacity usage ratio is high.Wherein first refers to that the slider-crank mechanism of section can be converted into the wide-angle of motor the small distance movement of first slide block; Second refers to that the slider-crank mechanism of section can pass through the rotation of the small distance movement realization second finger section wide-angle of second slide block, and above-mentioned characteristic has been reduced the volume of first knuckle greatly.Profile is similar with people's hand finger; Can be used as a finger of anthropomorphic robot's hand or a part of pointing; Also can be combined into robot, in order to reach the excellent results of the high joint freedom degrees of anthropomorphic robot's hand, high adaptivity with a plurality of such parallel coupled under-actuated fingers based on the double-crank slide block.
Description of drawings
Fig. 1 is the sectional view of a kind of embodiment of double link slide block type coupling adaptive under-actuated robot finger device provided by the invention.
Fig. 2 is a positive view (also being the cut away left side view of Fig. 1) embodiment illustrated in fig. 1.
Fig. 3 is the sectional view of another embodiment of the present invention (embodiment that adopts rope to connect is touched in the loose joint between first slide block and second slide block).
Fig. 4 is the positive view of another embodiment of the present invention (having changeable grasping force effect embodiment).
Fig. 5 is the side view of outward appearance embodiment illustrated in fig. 1.
Fig. 6 is the front view of outward appearance embodiment illustrated in fig. 1.
Fig. 7 is the stereogram of outward appearance embodiment illustrated in fig. 1.
Fig. 8 is the stereogram of part embodiment illustrated in fig. 1.
Fig. 9 is a three-dimensional explosive view embodiment illustrated in fig. 1.
Figure 10,11,12, the 13rd, the middle side schematic appearance that realizes coupling extracting process embodiment illustrated in fig. 1.
Figure 14,15,16, the 17th, middle coupling extracting and the under-driven adaptive realized embodiment illustrated in fig. 1 grasps the side schematic appearance of process.
Figure 18,19,20, the 21st, the middle side schematic appearance that realizes the Grasp Modes process that elder generation's coupling back self adaptation owes to drive embodiment illustrated in fig. 1.
In Fig. 1 to Figure 21:
The 1-pedestal, the 11-abase frame, 12-pedestal backboard,
The 121-first projection 13-pedestal header board, the right support plate of 14-pedestal,
15-pedestal connecting plate, the 2-motor, the nearly joint shaft of 3-,
31-is the joint semiaxis in the vicinity, the right nearly joint of 32-semiaxis, and 4-first refers to section,
41-first refers to the section frame, and 42-first refers to the section backboard, 421-second projection,
43-first refers to the right support plate of section, 5-joint shaft far away, and joint far away, 51-left side semiaxis,
The right joint far away of 52-semiaxis, 6-second refers to section, 71-first dial,
The 72-first connecting rod, 73-first slide block, 74-second slide block,
741-slider table panel, the 75-second connecting rod, 76-second dial,
First of 77-, second of 78-, the 3rd of 79-,
The 4th of 80-, the 81-first spring spare, the 82-second spring spare,
The 91-decelerator, 92-first gear, 93-second gear,
The 94-sleeve, the 95-pin, the 96-rope,
The 97-object.
The specific embodiment
Below in conjunction with accompanying drawing and embodiment further explain concrete structure of the present invention, operation principle and the course of work.
The embodiment of a kind of double link slide block type coupling adaptive under-actuated robot finger device of the present invention's design; Cutaway view is like Fig. 1, shown in 2; Outward appearance is like Fig. 5, shown in 6, and three-dimensional appearance is as shown in Figure 7, and part is as shown in Figure 8; Three-dimensional explosive view is as shown in Figure 9, operating principle such as Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15, Figure 16, Figure 17, Figure 18, Figure 19, Figure 20, shown in Figure 21.A kind of double link slide block type coupling adaptive under-actuated robot finger device; Comprise pedestal 1, joint semiaxis 31, first refers to that section 4, joint shaft far away 5, second refer to section 6 and motor 2 in the vicinity; Described motor 2 is arranged in the pedestal 1, and the output shaft of motor 2 links to each other with joint semiaxis 31 in the vicinity; Described joint in the vicinity semiaxis 31 is set in the described pedestal 1, and described joint shaft 5 far away is set in first and refers in the section 4, and described second refers to that section 6 is fixed on the described joint shaft far away 5; This double link slide block type coupling adaptive under-actuated robot finger device also comprises right nearly joint semiaxis 32, first dial 71, first connecting rod 72, first 77, second 78, first slide blocks 73, second slide block 74, second connecting rod 75, the 3rd 79, the 4th 80, second dial 76 and the first spring spare 81; Described first refers to that section 4 is fixed in the vicinity on the joint semiaxis 31, and first refers to that section 4 is set on the right nearly joint semiaxis 32; Nearly joint, described right side semiaxis 32 is set on the pedestal 1, and right nearly joint semiaxis is with the joint semiaxis is coaxial in the vicinity, and the right nearly joint semiaxis and first dial 71 are affixed, and described first dial 71 is set on the left joint semiaxis 31, and first dial 71 is affixed with pedestal 1; Described first connecting rod 72 1 ends and first dial 71 are hinged through first 77, and the other end and first slide block 73 are hinged through second 78; Described first slide block 73 is embedded in first and refers in first chute of section 4, and second slide block 74 is embedded in first and refers to that described first chute is parallel with second chute in second chute of section 4, and first slide block 73 and 74 loose joints of second slide block are touched; Described second connecting rod 75 1 ends and second slide block 74 are hinged through the 3rd 79, and the other end and second dial 76 are hinged through the 4th 80; Described second dial 76 is fixed on the joint shaft 5 far away; The described first spring spare 81 is arranged on first and refers to that section 4 and second refers between the section 6 and the two ends of the first spring spare 81 refer to that with first section 4 and second refers to that section 6 is connected respectively, and the perhaps described first spring spare 81 is arranged on second slide block 74 and first and refers between sections 4 and the two ends of the first spring spare 81 are connected with second slide block 74 and first finger sections 4 respectively.Other has the embodiment cutaway view like Fig. 3, shown in 4, and the two ends of the second spring spare 82 connect first respectively and refer to section 4 and joint semiaxis 31 in the vicinity, and all the other structures are identical.
In the present embodiment, the structural parameters of described first connecting rod, second connecting rod, first dial and second dial meet following relation: the length of establishing first connecting rod 72 is L
1, the distance of the center line of the center line to the second of first dial 71 spools 78 is R
1If the length of second connecting rod 75 is L
2, the distance of the center line that the center line to the of second dial 76 is four 80 is R
2, then: L
1: R
1=L
2: R
2=2.5~3.5: 1.
In the present embodiment, described joint shaft 5 far away is made up of joint far away, left side semiaxis 51 and right joint semiaxis 52, joint far away, described left side semiaxis 51 and right joint far away semiaxis 52 coaxial being set in the first finger section.
In the present embodiment, described first slide block 73 touches mode with the loose joint of second slide block 74 and adopts first slide block 73 to contact with second slide block, 74 single faces, and described first slide block 73 promotes the slippage in finger of second slide block 74.
In the present embodiment, described first slide block 73 touches mode with the loose joint of second slide block 74 and adopts rope 96 to be connected, described first slide block 73 pullings, second slide block 74 slippage in finger.
In the present embodiment, described spring spare 81 adopts stage clip, torsion spring or elastic threads.
In the present embodiment, also comprise transmission mechanism, described transmission mechanism comprises decelerator 91, first gear 92 and second gear 93; The output shaft of described motor 2 links to each other with the power shaft of decelerator 91, and described first gear 92 is fixed on the output shaft of decelerator 91, and described second gear 93 is fixed on the nearly joint shaft 3, described first gear 92 and 93 engagements of second gear.
In the present embodiment, described second slide block, 74 surface coverage have the second slider table panel 741.
The embodiment of a kind of double link slide block type coupling adaptive under-actuated robot finger device that the present invention also provides, its cutaway view is as shown in Figure 3.First slide block 73 touches mode with the loose joint of second slide block 74 and adopts rope 96 to be connected, and when first slide block 73 moved in finger, first slide block 73 can spur the slippage in finger of second slide block 74.Run into object when the first finger section 4, when second slide block 74 moved in finger, 74 pairs first slide blocks 73 of second slide block can not exert an influence, and have realized natural decoupling zero.
Introduce the operation principle of the embodiment of double link slide block type coupling adaptive under-actuated robot finger device shown in Figure 1 below in conjunction with accompanying drawing.
Robot finger's original state is shown in figure 10, and when this moment, finger did not contact object 97, first referred to that section 4 is in straight configuration (first projection 121 heads on first and refers to that section 4 makes finger be unlikely back-flexing) with respect to pedestal 1; What the first spring spare 81 adopted is stage clip, and this stage clip forces second to refer to that section 6 and first refers to keep between the section 4 original state of stretching, and joint shaft 5 promptly far away does not rotate (second projection 421 heads on second and refers to section 6), whole finger maintenance this moment straight configuration.
The Grasp Modes of present embodiment has two kinds, and narration is as follows respectively:
(a) coupling extracting process
When robot finger's grasping objects 97; Motor 2 is just changeing; Driving first gear 92 through decelerator 91 rotates; Drive second gear 93 and rotate, make in the vicinity that joint shaft 31 is just changeing, drive first and refer to that section 4 just changes (this positive veer is meant that first refers to that section 4 meets the object that grasps to needs gradually) around the center line of joint shaft 31 in the vicinity.Because first dial 71 is set in the vicinity on the joint shaft 31 and is affixed with pedestal 1; Therefore the rotation of the first finger section 4; Can make and oppositely stirred (first connecting rod 72 is to the finger interior translational motion) by first dial 71 with first connecting rod 72, then be embedded in first refer in the section 4 first slide block 73 along with first connecting rod 72 to the finger interior translational motion.Because second slide block 74 contacts with first slide block, 73 single faces, first slide block 73 can drive second slide block 74 and refer to 4 li slippages of section to first; Second connecting rod 75 slippage in finger, driving joint shaft 5 far away is just changeing, and the second finger section 6 is just being changeed (meeting the object that grasps to needs), up to finger contact object.
First dial 71 of present embodiment and the reference diameter of second dial 76 equate, so first refers to that section 4 refers to that with respect to the angle and second of pedestal 1 rotation section 6 refers to that with respect to first the angle of section 4 rotations is identical, has promptly realized the coupled drive of 1:1.In sum, present embodiment has been realized the function that coupling is grasped under the motionless situation of object.Concrete motion process such as Figure 10, Figure 11, Figure 12, shown in Figure 13.
The process of decontroling object is identical with the process of above-mentioned grasping objects, and motor 2 counter-rotatings will drive first and refer to that section 4 and second refers to section 6 backward rotation simultaneously, realize decontroling object, finally be returned to the initial straight configuration of finger.
(b) owe to drive the extracting process
Have two kinds to owe to drive the extracting process:
1) owe to drive the extracting process for first kind: other fingers and external force are directly pushed object, and object pushes 74 triggerings of second slide block and owes to drive extracting, and final second refers to that section 6 fastens object fast.Specifically, slidably second slide block 74 contacts with object 97 on the first finger section 4, and second refers to that section 6 does not contact with object; Object is when promoting second slide block 74 under other finger or the external force effect in finger, the slippage in finger of second slide block 74 is because second slide block 74 contacts with first slide block, 73 single faces; So can not exert an influence to first slide block 73; Realized natural decoupling zero (employing embodiment illustrated in fig. 3 96 connected modes of restricting have realized natural decoupling zero, and principle is identical therewith, repeats no more).The slippage meeting of second slide block 74 drives second connecting rod 75 and in finger, slides; Driving joint shaft 5 far away is just changeing; The second finger section 6 just being changeed up to the contact object realized extracting, and can adapt to the size shape of object automatically, is that a kind of self adaptation that need not machine operation owes to drive Grasp Modes.Concrete motion process such as Figure 14, Figure 15, Figure 16, shown in Figure 17.
2) owe to drive the extracting process for second kind: object fixed (by palm or other fingers, external force constraint); Thereby present embodiment was rotated further and caused second slide block 74 to refer to have triggered in the section 4 owe to drive and grasp because of object blocks is pressed into first this moment, and final second refers to that section 6 fastens object fast.Specifically; Slidably second slide block 74 contacts with object 97 on the first finger section 4; Second refers to that section 6 does not contact with object; This moment is because object is firmly fixed by palm or other finger constraints; Second slide block 74 is by object blocks, refers to that section 4 can also rotate a very little angle δ this moment first, this rotation will produce one second refer to section 6 with respect to first refer to the 1:1 of section 4 coupled rotation angle δ (reason is seen aforesaid coupling extracting process); And this moment is because second slide block 74 has referred to that with respect to first section 4 is to the finger interior one section less distance, delta d that slided; Therefore the distance of this variation will make second connecting rod 75 slide, thereby drive second dial 76 and a bigger angle θ of the second finger section, 6 rotations, because the contact point on object and second slide block, 74 surfaces arrives the reference radius r of the distance h of nearly joint shaft 3 center lines greater than first dial 71
1, can know that through following calculating θ can be greater than α, thereby realize that second refers to that the angle that section 6 turns over is a bigger angle θ, no longer be the angle [alpha] of coupled rotation.Computational analysis is following: this moment first slide block 73 first refer to can to move in the rotation process of smaller angle δ of section 4 one less apart from d
1, d
1=δ r
1And second slide block 74 first refer to can to move in the rotation process of smaller angle δ of section 4 one bigger apart from d
2, d
2=δ h is because h is greater than r
1, so d
2Greater than d
1This moment second slide block 74 with the disengagements of first slide block 73, realized natural decoupling zero, one of second slide block, 74 translation are apart from d
2, cause second to refer to section 6 quick buttons to object, this process refers to that up to second section 6 tightly fastens object, thereby has realized owing to drive the extracting process.This owes to drive to grasp and has realized that the extracting of the big wisp of difformity is had adaptivity, has alleviated the requirement to the control system.Owe to drive extracting process such as Figure 18, Figure 19, Figure 20, shown in Figure 21 for second kind.
Comprehensively (a) and (b) coupling can know that present embodiment has been realized the Grasp Modes that a kind of special back of coupling earlier self adaptation owes to drive with the self-adapting grasping process, the decoupling zero mode is natural, need not the loss power of motor.Apparatus of the present invention are utilized motor, two cover crank slide block mechanisms and spring spare comprehensively to realize coupled rotation and are owed to drive the transmission effect that rotation is combined closely; Not only can reach 1: 1 by the coupled rotation ratio; The ground grasping objects can more personalize; And possess and owe to drive function, the object of self-adapting grasping difformity, size; This device has been owing to adopted a sets of transmission mechanism just to realize coupling simultaneously and owe to drive and grasp, and makes whole finger structure concision and compact, installs easily, and it is low to make processing cost; This device coupled transmission mechanism with owe drive transmission device and organically blend, do not influence each other, the multiple mode of utilizing the slide block loose joint to touch has realized natural decoupling zero, this decoupling zero does not consume power of motor, capacity usage ratio is high; This device can be enlarged into bigger rotational angle with less displacement because the transmission of employing slider-crank mechanism is simple in structure; Its profile is similar with people's hand finger; Can be used as a finger of anthropomorphic robot's hand or a part of pointing; Also can be combined into robot, in order to reach the excellent results of the high joint freedom degrees of anthropomorphic robot's hand, high adaptivity with a plurality of such double link slide block type coupling adaptive under-driving robot fingers.