A terminal gripper for picking spheroid fruits and a parameter optimization method

Abstract

The application relates to the field of agricultural machinery, and aims to provide an end gripper for picking spheroid fruits and a parameter optimization method, so as to improve the enveloping property, adaptability and reliability of the end gripper. The technical scheme is an end gripper for picking spheroid fruits, characterized in that the end gripper comprises a rack, a plurality of fingers, a motor, a camera, a transmission mechanism for transmitting motor power to drive the fingers to open and close simultaneously, and a controller; the fingers comprise first knuckles and second knuckles; the transmission mechanism comprises first push plates and second push plates which are slidably positioned on the rack, a transmission assembly for transmitting motor power to drive the first push plates and the second push plates to move, a first connecting rod assembly connecting the first push plates and the first knuckles, and a second connecting rod assembly connecting the second push plates and the second knuckles; and the controller is electrically connected with the motor and the camera.

Description

Technical Field

[0001] This invention relates to the field of agricultural machinery, specifically to an end gripper for picking spherical fruits and a method for optimizing its parameters. Background Technology

[0002] As urban and rural population transition and population aging intensify, the associated labor costs in fruit and vegetable production are rising further.

[0003] Developing harvesting robots to replace human labor is a feasible approach to solving the aforementioned problems. The end effector, as a key component of harvesting robots, directly impacts their harvesting success rate. Currently, most end effectors on the market employ rigid gripping, resulting in complex structures that struggle to encompass fruits of varying sizes and shapes, and they also fail to balance efficiency with damage-free harvesting. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings in the above-mentioned background technology and provide an end gripper for picking spherical fruits and a parameter optimization method to improve the enveloping properties, adaptability and reliability of the end gripper.

[0005] The technical solution of this invention is:

[0006] An end effector for picking spherical fruits, characterized in that: the end effector includes a frame, several fingers, a motor, a camera, a transmission mechanism for transmitting motor power to drive the fingers to open and close simultaneously, and a controller; the fingers include a first phalanx and a second phalanx; the transmission mechanism includes a first push plate and a second push plate slidably positioned on the frame, a transmission assembly for transmitting motor power to drive the first push plate and the second push plate to move, a first link assembly connecting the first push plate and the first phalanx, and a second link assembly connecting the second push plate and the second phalanx; the controller is electrically connected to the motor and the camera.

[0007] The transmission assembly includes a transmission shaft, a bevel gear set for transmitting power between the motor and the transmission shaft, a first cam and a second cam fixed on the transmission shaft, a first follower fixed to the first push plate and cooperating with the first cam, a second follower fixed to the second push plate and cooperating with the second cam, a first spring for pushing the first push plate, and a second spring for pushing the second push plate.

[0008] The first linkage assembly includes a first push rod fixed to a first push plate and a first connecting rod hinged between the first push rod and a first finger joint; the second linkage assembly includes a second push rod fixed to a second push plate and a second connecting rod hinged between the second push rod and a second finger joint.

[0009] The first connecting rod is located outside the hinge axis of the first phalanx; the second connecting rod is located inside the hinge axis of the second phalanx; the eccentricity of the first cam and the second cam are opposite.

[0010] The first push plate and the second push plate move in opposite directions; when the first push plate and the second push plate move toward each other, the fingers close to grasp the fruit; when the first push plate and the second push plate move away from each other, the fingers open to release the fruit.

[0011] The motor shaft is perpendicular to the axis of the transmission shaft; the bevel gear set includes a driving gear fixed to the motor shaft and a driven gear fixed to the transmission shaft.

[0012] The second phalanx is rotatably hinged to the frame, and the first phalanx is rotatably hinged to the second phalanx.

[0013] The frame includes a first guide rod and a second guide rod arranged in parallel, and a front bracket and a rear bracket fixed at both ends of the first guide rod and the second guide rod;

[0014] The first push plate is slidably positioned on the first guide rod; the second push plate is slidably positioned on the second guide rod.

[0015] The camera is fixed in the center of the front bracket, and three fingers are evenly arranged around the camera.

[0016] A method for optimizing the parameters of an end gripper used for picking spherical fruits includes the following steps:

[0017] 1) Solving the kinematic equations

[0018] H coordinates (X) H Y H )for

[0019]

[0020] EG is

[0021]

[0022] The kinematic equation of point D is:

[0023]

[0024] The kinematic equation for point B is:

[0025]

[0026] BH is

[0027]

[0028] The kinematic equation for point C is:

[0029]

[0030] The coordinates of point A are (X...) A Y A )for

[0031]

[0032]

[0033] 2) Analysis of fruit enveloping properties

[0034] The equation of the line BD during the gripper envelope is:

[0035] a1x + a2y + a3 = 0 (9)

[0036] In the formula, a1, a2, and a3 are all constants;

[0037] The equation of line AB is

[0038]

[0039] The equation of the inscribed circle inside the gripper is:

[0040] x 2 +(ym) 2 =r 2 (11)

[0041] In the formula, m is the ordinate of the center of the circle, and r is the radius of the inscribed circle;

[0042] Since the incircle is tangent to AB and BD, the radius of the incircle is...

[0043]

[0044] Solving the simultaneous equations will yield the expression for the ordinate of the circle's center.

[0045] m = f1(x A ,x B ,y A ,y B (13)

[0046] Solve the equations of the inscribed circle and BD simultaneously.

[0047]

[0048] The functional equations of the inscribed circle and the coordinates T(α1, β1) of the point of tangency during the envelope process can then be obtained.

[0049]

[0050] Define the position u of the tangent point T in BD as...

[0051]

[0052] Solve the equations of the inscribed circle and AB simultaneously.

[0053]

[0054] The functional equation of the point of tangency Q(α2, β2) between the inscribed circle and AB during the envelope process can then be obtained.

[0055]

[0056] Define the position v of the tangent point Q in AB as...

[0057]

[0058] 3) Optimize the model

[0059] Let l1, l3, and θ2 be used as design variables, denoted as X. n Then the set of variables X is:

[0060]

[0061] The final optimization objective function is:

[0062] min{f1(X),f2(X),f3(X)}

[0063]

[0064] or

[0065] min{f1(X),f2(X),f3(X)}

[0066]

[0067] or

[0068] min{f1(X),f2(X),f3(X)}

[0069]

[0070] After optimizing each of the three sets of conditions, the parameters with the best objective function are selected as the optimal parameters.

[0071] The beneficial effects of this invention are:

[0072] (1) This invention uses a single motor to drive a transmission mechanism with double cams to drive the movement of three fingers, which can achieve the enveloping grasp of spherical fruits of different diameters. The whole machine has fewer driving parts and lower complexity.

[0073] (2) Compared with other structures, the transmission mechanism of the present invention uses a double cam for driving, and is driven by the upper and lower finger joints to adapt to different working environments and fruits of different sizes.

[0074] (3) When the fingers of the present invention are wrapping the fruit, the contour curve of the double cam is designed so that the movement speed of the two finger joints increases first and then decreases, which effectively reduces the impact of the finger movement on the fruit and improves the grasping efficiency; and the speed of the first finger joint is faster than that of the second finger joint, which can quickly wrap the fruit and prevent the fruit from slipping out of the grasper.

[0075] (4) The present invention can optimize the size of the gripper structure through a multi-objective optimization algorithm. By optimizing the change in the centroid of the inscribed circle and the change in the tangent point when the gripper opens and closes, the stability of grasping the fruit can be optimized. Attached Figure Description

[0076] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0077] Figure 2 This is a schematic diagram of the main structure of the present invention.

[0078] Figure 3 This is a schematic diagram of the right-side structure of the present invention.

[0079] Figure 4 This is a three-dimensional structural diagram of the finger of the present invention.

[0080] Figure 5 This is a three-dimensional structural diagram of the transmission mechanism of the present invention.

[0081] Figure 6 This is a three-dimensional structural diagram of the frame of the present invention.

[0082] Figure 7 This is a three-dimensional structural diagram of the first pusher plate of the present invention.

[0083] Figure 8 This is a three-dimensional structural diagram of the second pusher plate of the present invention.

[0084] Figure 9 This is a three-dimensional structural diagram of the first cam and the second cam of the present invention.

[0085] Figure 10 This is one of the schematic diagrams of the parameter optimization method of the present invention.

[0086] Figure 11 This is the second schematic diagram of the parameter optimization method of the present invention.

[0087] Figure label:

[0088] Frame 1, First guide rod 1-1, Second guide rod 1-2, Front support 1-3, Rear support 1-4, Sub-support 1-5, Finger 2, First knuckle 2-1, First knuckle extension 2-1-1, Second knuckle 2-2, Second knuckle extension 2-2-1, Motor 3, Drive gear 3-1, Driven gear 3-2, Coupling 3-3, Camera 4, First push plate 5-1, Second push plate 5-2, Drive shaft 6, First cam 6-1, Second cam 6-2, Connecting seat 6-3, First follower 7-1, Guide groove 7-1-1, Second follower 7-2, Second follower guide plate 7-2-1, Second follower top column 7-2-2, First push rod 8-1, First push rod extension 8-1-1, Second push rod 8-2, First connecting rod 9-1, Second connecting rod 9-2, Central axis A. Detailed Implementation

[0089] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0090] Example 1

[0091] like Figure 1 As shown, an end gripper for picking spherical fruits includes a frame 1, several fingers 2, a motor 3, a camera 4, a transmission mechanism, and a controller.

[0092] The camera and finger are positioned at the front of the frame ( Figure 2 The upper part of the middle frame), the motor is located at the rear end of the frame ( Figure 2 The lower part of the frame contains a transmission mechanism that transmits motor power to drive the fingers to open and close simultaneously, enabling the grasping and release of the fruit. The controller (omitted in the figure) is electrically connected to the motor and the camera.

[0093] The camera is a depth camera, used to acquire three-dimensional information of the fruit, enabling the fingers to accurately grasp the fruit.

[0094] like Figure 6 As shown, the frame includes a first guide rod 1-1, a second guide rod 1-2, a front support 1-3, and a rear support 1-4. The first and second guide rods are arranged parallel to each other and vertically fixed between the front and rear supports. The camera is fixed on the front support and located at the center of the front support. The fingers are arranged on the front support and are evenly distributed around the camera.

[0095] The front support has a notch at its center, and it also has auxiliary supports 1-5. The camera is installed in the notch and fixed to the auxiliary supports. There are three first guide rods, with their ends fixed to the front support and the rear support, respectively. There are also three second guide rods, with their ends fixed to the auxiliary supports and the rear support, respectively.

[0096] like Figure 4 As shown, the finger includes a first phalanx 2-1 and a second phalanx 2-2, the second phalanx being rotatably hinged to the front support, and the first phalanx being rotatably hinged to the second phalanx.

[0097] like Figure 4 As shown, the transmission mechanism includes a first push plate 5-1, a second push plate 5-2, a transmission assembly, a first connecting rod assembly, and a second connecting rod assembly. The first push plate 5-1 and the second push plate 5-2 are slidably positioned on the frame. The transmission assembly transmits motor power to drive the first push plate and the second push plate to move on the frame. The first connecting rod assembly connects the first push plate to the first finger joint. The second connecting rod assembly connects the second push plate to the second finger joint.

[0098] The first push plate is slidably positioned on the first guide rod of the frame, and the second push plate is slidably positioned on the second guide rod of the frame. For example... Figure 4 As shown, the second push plate is positioned above the first push plate. Figure 2 As shown, the second push plate is arranged inside the first guide rod, and the second guide rod passes through the first push plate.

[0099] like Figure 5 As shown, the transmission assembly includes a transmission shaft 6, a bevel gear set, a first cam 6-1, a second cam 6-2, a first follower 7-1, a second follower 7-2, a first spring, and a second spring.

[0100] The motor is fixed on the rear bracket, and the transmission shaft is rotatably positioned on the rear bracket via the connecting seat 6-3. The bevel gear set is used to transmit power between the motor and the transmission shaft. A first cam and a second cam are fixed on the transmission shaft. A first follower is fixed to the first push plate and cooperates with the first cam (abutting against the circumferential surface of the first cam). A second follower is fixed to the second push plate and cooperates with the second cam (the second follower passes through the first push plate and abuts against the circumferential surface of the second cam). A first spring is fitted on the first guide rod to push the first push plate, and a second spring is fitted on the second guide rod to push the second push plate.

[0101] like Figure 7 and Figure 8As shown, the first push plate has a guide groove 7-1-1, and the second follower includes a second follower guide plate 7-2-1 fixed to the second push plate and a second follower top post 7-2-2 made at the bottom of the second follower guide plate. The second follower guide plate is slidably positioned in the guide groove to play a guiding role, and the second follower top post abuts against the second cam.

[0102] like Figure 5 As shown, when the first cam and the second cam rotate, they can drive the first follower and the second follower to perform simple harmonic motion, reducing the impact force during motion. Figure 5 As shown, the first cam pushes the first push plate upwards via the first follower, and the first spring is used to reset the first push plate. The first spring is located above the first push plate. The second cam pushes the second push plate upwards via the second follower, and the second spring is used to reset the second push plate. The second spring is located above the second push plate. The first and second springs are omitted in the figure.

[0103] like Figure 5 As shown, when the motor starts, it rotates at a certain angle. The first cam, the second cam, the first spring, and the second spring work together to drive the first push plate and the second push plate to move. Then, through the first linkage assembly and the second linkage assembly, the fingers are driven to close, thereby grasping the fruit (enveloping the fruit). When the motor rotates in the opposite direction, the first push plate and the second push plate move in the opposite direction to reset. Then, through the first linkage assembly and the second linkage assembly, the fingers are driven to open, thereby releasing the fruit.

[0104] like Figure 4 , Figure 7 As shown, the first linkage assembly includes a first push rod 8-1 fixed to the first push plate and a first connecting rod 9-1 hinged between the first push rod and the first finger joint. The first finger joint has a first finger joint extension 2-1-1, and the first push rod has a first push rod extension 8-1-1. The two ends of the first connecting rod are rotatably hinged to the first finger joint extension and the first push rod extension, respectively. Three first push rods are vertically fixed on the first push plate. The first push rods pass through the front bracket and then connect to the first connecting rod. The first connecting rod is located outside the hinge axis between the first finger joint and the second finger joint (on the side away from the central axis A).

[0105] like Figure 4 , Figure 8As shown, the second linkage assembly includes a second push rod 8-2 fixed to the second push plate and a second connecting rod 9-2 hinged between the second push rod and the second finger joint. The second finger joint has a second finger joint extension 2-2-1, which passes through a first push rod extension (which is a frame structure) and is rotatably hinged to the front support. Both ends of the second connecting rod are rotatably hinged to one end of the second finger joint extension and the second push rod, respectively. Three second push rods are vertically fixed to the second push plate, passing through the front support and then connecting to the second connecting rod. The second connecting rod is located inside the hinge axis of the second finger joint (on the side closest to the central axis A).

[0106] To avoid the first link interfering with finger movement, it needs to be positioned further out. The second link, however, is closer to the front support and will not interfere with finger movement, so it can be positioned further in.

[0107] like Figure 4 As shown, when the first pusher plate rises, the first finger joint retracts inward; when the second pusher plate rises, the second finger joint opens outward. To ensure that the first and second finger joints move in the same direction, the first and second pusher plates must move in opposite directions. Therefore, the eccentricity directions of the first and second cams are opposite. Figure 9 As shown, the first cam and the second cam protrude to both sides of the drive shaft, respectively.

[0108] like Figure 4 As shown, when the first push plate and the second push plate move towards each other, that is, the first push plate rises and the second push plate falls, the fingers close to grasp the fruit (envelop the fruit), and when the first push plate and the second push plate move away from each other, that is, the second push plate rises and the first push plate falls, the fingers open to release the fruit.

[0109] On the other hand, the second link can also be set further out (omitted in the figure). In this case, the eccentricity of the first cam and the second cam are the same, and the movement direction of the first push plate and the second push plate is the same. When the first push plate and the second push plate move upward at the same time, the fingers close to grasp the fruit (envelop the fruit). When the first push plate and the second push plate move downward at the same time, the fingers open to release the fruit.

[0110] The motor shaft is perpendicular to the axis of the transmission shaft. The bevel gear set includes a driving gear 3-1 fixed to the motor shaft and a driven gear 3-2 fixed to the transmission shaft. The driving gear is coaxially connected to the motor shaft via a coupling 3-3.

[0111] All components of this invention are existing technologies and can be purchased externally.

[0112] The following provides a further explanation of finger movements:

[0113] 1. Close your fingers

[0114] The first and second cams rotate, which in turn causes the fingers to close. Figure 9 The arrows and dashed lines represent the direction and trajectory of the first follower on the first cam, and the reverse direction and trajectory of the second follower on the second cam, respectively.

[0115] At this point, the height of the first cam gradually increases, thus lifting the first push plate upwards via the first follower. The height of the second cam gradually decreases, causing the second spring to press down on the second push plate. Because the size of the first cam is larger than that of the second cam, the height change range of the first cam is greater than that of the second cam, resulting in the first push plate rising a greater distance than the second push plate falling. This causes the first knuckle to swing faster than the second knuckle, allowing the first knuckle to quickly close and envelop the fruit, preventing it from slipping out of the gripper.

[0116] Meanwhile, the height change range of the first cam first increases and then decreases, and the height change range of the second cam also first increases and then decreases, so that the swing speed of the first and second knuckles first increases and then decreases. This can achieve flexible grasping, reduce the impact on the fruit and avoid damage to the fruit surface, and improve grasping efficiency.

[0117] In the above process, the drive shaft only needs to rotate through a certain angle (preferably 120 degrees) to enable the fingers to complete the grasping action and envelop the fruit.

[0118] 2. Spread your fingers

[0119] The drive shaft rotates in the opposite direction (preferably 120 degrees), and the fingers are fully opened to release the fruit. The specific process is the reverse of the first step and will not be described further.

[0120] Example 2

[0121] A method for optimizing the parameters of an end gripper used for picking spherical fruits includes the following steps:

[0122] 1) Solving the kinematic equations

[0123] The purpose of optimizing the parameters of the end effector is to improve its harvesting range and harvesting stability. Therefore, before optimization, it is necessary to obtain the motion characteristics of the end effector.

[0124] like Figure 10 As shown:

[0125] AB is the first knuckle with a length of l1, BC is the extension of the first knuckle with a length of l2, BD is the second knuckle with a length of l3, DG is the extension of the second knuckle with a length of l5, CH is the first link with a length of l6, DE is the second link with a length of l4, EF is the second push rod with a length of l8, HI is the extension of the first push rod with a length of l7, and IJ is the first push rod with a length of l9.

[0126] The angle between AB and BD is θ1, the angle between AB and BC is θ2, the angle between BC and CH is θ3, the angle between BD and DE is θ4, the angle between BD and DG is θ5, the angle between DE and EF is θ6, the angle between CH and HI is θ7, and the angle between BD and DE is θ8.

[0127] The horizontal direction is the X-axis, the vertical direction is the Y-axis, and the origin O is the intersection of the central axis of the frame and the central axis of the drive shaft;

[0128] K is the base circle radius of the cam (the base circle radii of the two cams are the same).

[0129] Let the distance EF (second pusher) moves be C1, and the distance IJ (first pusher) moves be C2, then:

[0130] The coordinate of E is (l 10 ,C1+k+l8), F coordinate is (l 10 ,C1+k), J coordinate is (l 11 ,C2+k), I coordinates are (l 11 ,C2+k+l9), G coordinate is (l 12 , l 13 ).

[0131] H coordinates (X) H Y H )for

[0132]

[0133] Therefore, EG is calculated as:

[0134]

[0135] The kinematic equation of point D is then obtained as follows:

[0136]

[0137] From the coordinates of point D, the kinematic equation of point B is:

[0138]

[0139] Calculate BH from the coordinates of point B.

[0140]

[0141] The kinematic equation of point C is then obtained as follows:

[0142]

[0143] Then the coordinates (X) of point A at the end of the first phalanx can be obtained. A Y A )for

[0144]

[0145]

[0146] 2) Analysis of fruit enveloping properties

[0147] like Figure 11 As shown, the picking stability and envelope performance of the end gripper are mainly determined by solving the range of change of the center of the inscribed circle and the change of the coordinates of the tangent point.

[0148] Based on the aforementioned dimensional parameters, the linear equation of BD can be calculated when the gripper envelops the servo motor and it rotates to a specified angle.

[0149] a1x + a2y + a3 = 0 (9)

[0150] In the formula, a1, a2, and a3 are all constants;

[0151] The equation of line AB is

[0152]

[0153] Let the equation of the inscribed circle inside the gripper be...

[0154] x 2 +(ym) 2 =r 2 (11)

[0155] In the formula, m is the ordinate of the center of the circle, and r is the radius of the inscribed circle;

[0156] The radius of the inscribed circle is

[0157]

[0158] Solving the simultaneous equations will yield the expression for the ordinate of the circle's center.

[0159] m = f1(x A ,x B ,y A ,y B (13)

[0160] Solve the equations of the inscribed circle and BD simultaneously.

[0161]

[0162] The functional equations of the inscribed circle and the coordinates T(α1, β1) of the point of tangency during the envelope process can then be obtained.

[0163]

[0164] Define the position u of the tangent point T in BD as...

[0165]

[0166] Solve the equations of the inscribed circle and AB simultaneously.

[0167]

[0168] The functional equations of the inscribed circle and the coordinates of the point of tangency Q(α2, β2) during the envelope process can then be obtained.

[0169]

[0170] Define the position v of the tangent point Q in AB as...

[0171]

[0172] 3) Optimize the model

[0173] The optimization goal of the end effector is to cover the largest possible area of ​​fruit while ensuring that the contact area between the end effector and fruit of different sizes is minimized in different opening and closing states, and that the displacement of the fruit's center of mass within the gripper is minimized, thereby ensuring stability during grasping.

[0174] The key variable parameters l1, l3, and θ2 that have a significant impact on the success rate of the capture are taken as design variables and denoted as X. n Then the set of variables X is:

[0175] X = (x1, x2, x3) T =(l1,l2,θ2) T (20)

[0176] The final optimization design objective function is to minimize the change in the coordinates of the centers of the two inscribed circles in the open and closed states of the gripper, and to ensure that the offset between the inscribed circles and the contact positions of the first and second phalanges is minimized at this time.

[0177] The final optimization objective function is:

[0178] Scenario 1:

[0179] min{f1(X),f2(X),f3(X)}

[0180]

[0181] Scenario 2:

[0182] min{f1(X),f2(X),f3(X)}

[0183]

[0184] Scenario 3:

[0185] min{f1(X),f2(X),f3(X)}

[0186]

[0187] In the formula:

[0188]

[0189] m1 is the ordinate of the center of the largest inscribed circle of the gripper, and m2 is the ordinate of the center of the smallest inscribed circle of the gripper;

[0190] u1 is the lower tangent point T when the gripper is in its maximum inscribed circle state, u2 is the lower tangent point T when the gripper is in its minimum inscribed circle state, v1 is the upper tangent point Q when the gripper is in its maximum inscribed circle state, and v2 is the upper tangent point Q when the gripper is in its minimum inscribed circle state.

[0191] θ 2min θ 2max l 1min l 1max l 3min l 3max These are the upper and lower limits of the optimization variable, respectively;

[0192] θ1min and θ1max are the upper and lower limits of the angle between the first and second phalanges, respectively. A `max` represents the maximum envelope radius of the first phalanx, `rmax` represents the maximum grasping radius of the fruit, and `x` represents the maximum grasping radius of the fruit. A min is the minimum envelope radius of the first finger joint, rmin is the minimum grasping radius of the fruit, lsafe is the safe distance to avoid finger collision, and x B max is the x-coordinate of the hinge between the first and second phalanges when the gripper is in its maximum inscribed circle state;

[0193] yc、y B Let C and B be the ordinates of the joints.

[0194] yc1、y B1 The ordinates of joints C and B are given when the gripper is in its maximum inscribed circle state.

[0195] yc2、y B2 The ordinates of joints C and B are given when the gripper is in its smallest inscribed circle state.

[0196] The three sets of optimization conditions were optimized using multi-objective optimization algorithms (existing algorithms, such as NGSA-2) and compared. The one with the optimal objective function was selected as the best parameter.

[0197] The accompanying drawings illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

Claims

1. A terminal gripper for picking spherical fruits, characterized in that: The end effector includes a frame (1), several fingers (2), a motor (3), a camera (4), a transmission mechanism that transmits motor power to drive the fingers to open and close simultaneously, and a controller; the fingers include a first phalanx (2-1) and a second phalanx (2-2); the transmission mechanism includes a first push plate (5-1) and a second push plate (5-2) that are slidably positioned on the frame, a transmission assembly that transmits motor power to drive the first push plate and the second push plate to move, a first link assembly that connects the first push plate and the first phalanx, and a second link assembly that connects the second push plate and the second phalanx; the controller is electrically connected to the motor and the camera; The transmission assembly includes a transmission shaft (6), a bevel gear set for transmitting power between the motor and the transmission shaft, a first cam (6-1) and a second cam (6-2) fixed on the transmission shaft, a first follower (7-1) fixed to the first push plate and cooperating with the first cam, a second follower (7-2) fixed to the second push plate and cooperating with the second cam, a first spring for pushing the first push plate, and a second spring for pushing the second push plate. The first linkage assembly includes a first push rod (8-1) fixed to the first push plate and a first connecting rod (9-1) hinged between the first push rod and the first finger joint; the second linkage assembly includes a second push rod (8-2) fixed to the second push plate and a second connecting rod (9-2) hinged between the second push rod and the second finger joint. The first connecting rod is located outside the hinge axis of the first phalanx; the second connecting rod is located inside the hinge axis of the second phalanx; the eccentricity directions of the first cam and the second cam are opposite. The frame includes a first guide rod (1-1) and a second guide rod (1-2) arranged in parallel, and a front bracket (1-3) and a rear bracket (1-4) fixed at both ends of the first guide rod and the second guide rod. The first push plate is slidably positioned on the first guide rod; the second push plate is slidably positioned on the second guide rod.

2. The end gripper for picking spherical fruits according to claim 1, characterized in that: The first push plate and the second push plate move in opposite directions; when the first push plate and the second push plate move toward each other, the fingers close to grasp the fruit; when the first push plate and the second push plate move away from each other, the fingers open to release the fruit.

3. The end gripper for picking spherical fruits according to claim 2, characterized in that: The motor shaft is perpendicular to the axis of the transmission shaft; the bevel gear set includes a driving gear (3-1) fixed to the motor shaft and a driven gear (3-2) fixed to the transmission shaft.

4. The end gripper for picking spherical fruits according to claim 3, characterized in that: The second phalanx is rotatably hinged to the frame, and the first phalanx is rotatably hinged to the second phalanx.

5. The end gripper for picking spherical fruits according to claim 4, characterized in that: The camera is fixed in the center of the front bracket, and three fingers are evenly arranged around the camera.

6. A parameter optimization method, applied to an end gripper for picking spherical fruits as described in any one of claims 1-5, comprising the following steps: 1) Solving the kinematic equations AB is the first knuckle with a length of l1, BC is the extension of the first knuckle with a length of l2, BD is the second knuckle with a length of l3, DG is the extension of the second knuckle with a length of l5, CH is the first link with a length of l6, DE is the second link with a length of l4, EF is the second push rod with a length of l8, HI is the extension of the first push rod with a length of l7, and IJ is the first push rod with a length of l9. The angle between AB and BD is θ1, the angle between AB and BC is θ2, the angle between BC and CH is θ3, the angle between BD and DE is θ4, the angle between BD and DG is θ5, the angle between DE and EF is θ6, the angle between CH and HI is θ7, and the angle between BD and DE is θ8. The horizontal direction is the X-axis, the vertical direction is the Y-axis, and the origin O is the intersection of the central axis of the frame and the central axis of the drive shaft; K is the radius of the cam base circle; Let the distance EF moves be C1, and the distance IJ moves be C2, then: The coordinate of E is (l) 10 C1+k+l8), F coordinate is (l 10 (C1+k), J coordinate is (l) 11 , C2+k), I coordinates are (l 11 C2+k+l9), G coordinates are (l 12 , l 13 ); H coordinates (X) H Y H )for （1） EG is （2） The kinematic equation of point D is: （3） The kinematic equation for point B is: （4） BH is （5） The kinematic equation for point C is: （6） The coordinates of point A (X) A Y A )for （7） （8） 2) Analysis of fruit enveloping properties The equation of the line BD during the gripper envelope is: （9） In the formula, a1, a2, and a3 are all constants; The equation of line AB is （10） The equation of the inscribed circle inside the gripper is: （11） In the formula, m is the ordinate of the center of the circle, and r is the radius of the inscribed circle; Since the incircle is tangent to AB and BD, the radius of the incircle is... （12） Solving the simultaneous equations will yield the expression for the ordinate of the circle's center. （13） Solve the equations of the inscribed circle and BD simultaneously. （14） The functional equations of the inscribed circle and the coordinates T(α1, β1) of the point of tangency during the envelope process can then be obtained. （15） Define the position u of the tangent point T in BD as... （16） Solve the equations of the inscribed circle and AB simultaneously. （17） The functional equation of the point of tangency Q(α2, β2) between the inscribed circle and AB during the envelope process can then be obtained. （18） Define the position v of the tangent point Q in AB as... （19） 3) Optimization Model Let l1, l3, and θ2 be used as design variables, denoted as X. n Then the set of variables X is: （20） The final optimization objective function is: （21） or （22） or （23） After optimizing each of the three sets of conditions, the parameters with the best objective function are selected as the optimal parameters.

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