Single-motor underactuated robot end effector with mechanical self-locking function

Abstract

The present invention discloses a single-motor under-actuated robot end effector with a mechanical self-locking function, comprising an actuator housing, a driving motor, a left clamping jaw assembly, a right clamping jaw assembly and a transmission system which utilizes the power of the driving motor to drive the left clamping jaw assembly and the right clamping jaw assembly to complete a clamping action; the transmission system comprises a reduction mechanism, a differential and a worm gear mechanism; the power of the driving motor is decelerated and torque-increased by the reduction mechanism and then input into the differential; the differential distributes the power to the two worm gear mechanisms and drives the two worms to rotate; the worm wheel of the worm gear mechanism is used to drive the left clamping jaw assembly or the right clamping jaw assembly to complete a clamping action; the end effector of the present invention is driven by a single motor and can achieve clamping self-locking, and is matched with a binocular camera on the end effector to complete position and size adaptive clamping, and can achieve precise placement and assembly.

Description

Technical Field

[0001] The present invention relates to an under-actuated robot end effector driven by a single motor and having a mechanical self-locking function in the field of item sorting and parts assembly. Specifically, the present invention relates to an under-actuated robot end effector that utilizes vision for sorting or assembly and can realize adaptive adjustment of clamping position and timely mechanical self-locking. Background Art

[0002] As robotic technology becomes increasingly mature, robotic arms are now widely used in the industrial field. In the process of sorting items and assembling parts, the actuator at the end of the robotic arm often determines the specific purpose of the robotic arm. The existing end-effector of the robotic arm is limited by its mass and often only contains a limited number of degrees of freedom for the clamping of light and small objects. In response to this phenomenon, there have been many studies on underactuated end effectors, such as the three-finger dexterous hand with patent publication number 201711492166.X; finger linkage, such as the differential gear train coupled adaptive underactuated finger with patent publication number 201210084863.2, the coupled adaptive three-finger differential robot gripper with tendon transmission with patent number 201810929933.7; using multiple motors, such as the dual-motor cooperative control underactuated manipulator with patent publication number 201610265841.4, the shape adaptive three-finger underactuated manipulator with patent publication number 201810502179.9, and the multi-purpose adaptive robot gripper with patent publication number 200610156059.5. The above patents all use underactuated mechanisms to increase operability and have the ability to adapt to the shape of objects, but they are still limited to the quality of the end effector and reduce the standard of work quality. In addition, the under-actuated mechanisms currently proposed basically do not include a self-locking mechanism, which increases safety hazards and is more prominent when the driving force of the end effector is insufficient. The double self-locking gripper with patent publication number 201911205707.5 and the multi-degree-of-freedom lever thread self-locking structure with patent publication number 201610840243.5 are large in size and are not suitable for small robots or robotic arms. In addition, the under-actuated structure cannot clearly indicate the position of the object after clamping due to the uncontrollable movement, which limits precise assembly. Although the finger end trajectory controllable under-actuated manipulator with patent publication number 201710218397.5 can control the end trajectory, it still has many of the problems mentioned above. Therefore, the present invention discloses an under-actuated end effector that uses a single motor drive and can achieve clamping self-locking, and is equipped with a binocular camera on the end effector to complete position and size adaptive clamping, and can achieve precise placement and assembly. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a single-motor under-actuated robot end effector with a mechanical self-locking function, which realizes the movement of two grippers separately and adaptive adjustment of the touching objects through the cooperation of a single motor and a differential structure, thereby reducing the number of drives and the overall mass. The motion reversal and mechanical self-locking are realized through a worm gear transmission and a parallelogram linkage mechanism, and the speed is adjusted while reducing the complexity of the mechanical system. The end effector has the above characteristics to enrich the end effector function and improve the system integration.

[0004] like Figure 1 As shown, the single-motor under-actuated robot end effector with mechanical self-locking function of the present invention comprises an actuator housing, a drive motor, a left clamping jaw assembly, a right clamping jaw assembly and a transmission system that utilizes the power of the drive motor to drive the left clamping jaw assembly and the right clamping jaw assembly to complete the clamping action;

[0005] The transmission system includes a reduction mechanism, a differential and a worm gear mechanism; the power of the driving motor is decelerated and torque-increased by the reduction mechanism and then input into the differential; the differential distributes the power to the two worm gear mechanisms and drives the two worms to rotate; the worm wheel of the worm gear mechanism is used to drive the left clamping jaw assembly or the right clamping jaw assembly to complete the clamping action; the worm gear mechanism decelerates and reverses the power output by the differential and transmits it to the clamping jaw assembly of the compound four-bar linkage mechanism, so as to realize the smooth and horizontal clamping of the clamping jaw and maintain the clamping state when the motor loses power.

[0006] Furthermore, the differential includes a differential housing, a differential dynamic shaft located in the housing, a pair of differential fixed gears and a pair of differential dynamic gears; the differential dynamic shaft is fixed in the housing and is perpendicular to the worm; the two differential dynamic gears are outermost on the differential dynamic shaft; the two differential fixed gears are respectively connected to the worm shafts of the two worm gear mechanisms and mesh with the differential dynamic gears.

[0007] Further, the speed reduction mechanism includes a small gear drivingly connected to the output shaft of the drive motor and a large gear fixed to the differential housing;

[0008] Furthermore, the left jaw assembly and the right jaw assembly respectively include at least a jaw body, a connecting rod I and a connecting rod II hinged between the jaw body and the actuator housing, a worm gear fixed to the worm wheel, and a push rod hinged between the worm gear and the jaw body; the actuator housing, the jaw body, the connecting rod I and the connecting rod II together constitute a parallel four-bar linkage mechanism; the worm gear, the push rod, the jaw body and the connecting rod I together constitute a double rocker mechanism.

[0009] Furthermore, a binocular camera centered between the left clamping jaw assembly and the right clamping jaw assembly is provided on the actuator housing.

[0010] Furthermore, a motor mounting hole and a motor shaft input hole for inserting the output shaft of the drive motor are provided on the side of the actuator housing, and a cavity for accommodating the speed reduction mechanism and the differential is formed inside the actuator housing.

[0011] Furthermore, a motor mounting hole and a motor shaft input hole for inserting the output shaft of the driving motor are provided on the side of the actuator housing, and a cavity for accommodating the reduction mechanism and the differential is formed inside the actuator housing; the driving motor can be a Panasonic motor with a servo control function, which is installed on the actuator housing through the mounting holes at the four corners of the motor end face, and the motor output shaft extends into the actuator housing through the motor shaft input hole and cooperates with the pinion gear of the reduction mechanism to input the torque and speed into the end actuator, wherein the pinion gear is coaxially matched with the motor shaft and is fixedly connected with a set screw.

[0012] Furthermore, a cavity for accommodating the worm gear mechanism is formed inside the actuator housing; there are two groups of worm gear mechanisms, and each group of worm gear mechanisms includes at least one worm and one incomplete worm wheel.

[0013] Furthermore, the worm wheel is an incomplete worm wheel; the worm wheel rod is a variable-section rod, which is integrally formed on the circumferential portion of the incomplete worm wheel without gear teeth; the worm and the fixed axis gear in the above-mentioned differential are coaxially matched through the spline at the end of the worm.

[0014] The principle of the present invention is as follows:

[0015] The driving motor power drives the differential housing to rotate through the transmission action of the reduction mechanism, and the differential housing drives the moving shaft gear installed in the differential housing to perform a compound motion in which the rotating shaft rotates around the fixed shaft. Due to the cross-engagement of the moving shaft gear and the fixed shaft gear, the power is distributed to the two fixed shaft gears. The two fixed shaft gears transmit the power to the worm gear mechanism and then to the clamping assembly of the composite connecting rod group structure to realize the movement of the clamping jaws. During the clamping process, when the two clamping jaws do not contact the object, the two clamping jaws move synchronously. When one clamping jaw body contacts the object, the corresponding worm gear mechanism is mechanically self-locked due to the resistance factor and stops moving. The differential transmits all the speed to the other clamping jaw assembly, and under-driven adaptive clamping is realized at this time. When both clamping jaws touch the surface of the object, the current loop of the servo motor gives force feedback to stop the motor from rotating. Due to the existence of the clamping force, the two clamping jaws have a reaction force on their corresponding worm gear mechanisms. The reverse self-locking ability of the worm gear mechanism is used to realize the mechanical self-locking of the end effector, and the safety protection function of clamping is realized.

[0016] Beneficial effects of the present invention:

[0017] 1. The end effector of the present invention adopts a single motor with a planetary bevel gear differential, which can increase the freedom of the system without increasing the number of driving parts. When clamping, the clamping movement is adaptively adjusted according to the position of the object, and the movement is smooth without excessive impact.

[0018] 2. The two clamping jaws of the end effector of the present invention are respectively connected to a set of worm gear transmission mechanisms, and each of them stops moving by relying on the clamping resistance when it hits the object during the clamping process, and can adaptively self-lock.

[0019] 3. The driver of the end effector of the present invention adopts a reasonable arrangement of four mechanisms: a spur gear reduction mechanism, a differential, a worm gear reduction mechanism, and a parallel four-bar linkage mechanism, to achieve the integration of under-actuated adaptive adjustment, mechanical clamping self-locking, movement direction adjustment and speed adjustment functions in the volume of a conventional end effector, enrich the system functions and improve the system integration.

[0020] 4. A binocular camera is installed between the two grippers of the end effector of the present invention. The robotic arm control system equipped with the end effector can obtain the state of the adaptive clamping of the end effector, and actively adjust the posture of the robotic arm when putting down an object to ensure accurate prevention of the object from being clamped. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0022] Figure 1 It is an overall structural diagram of the end effector of the present invention.

[0023] Figure 2 It is a schematic diagram of the internal structure of the end effector of the present invention (in the figure, the housing of the end effector is sectioned and the sections are marked with section lines).

[0024] Figure 3 It is a transmission diagram of the under-driven structure for automatically distributing rotational speed in the present invention (in the figure, the differential housing is partially cut away).

[0025] Figure 4 yes Figure 3 An enlarged view of the structure within the middle dotted circle (the differential housing is partially cut in the figure and the section is marked with a hatching line).

[0026] Figure 5 It is a schematic diagram of the installation of the worm gear of the protection mechanism for mechanical self-locking of the end effector in the present invention (the end effector housing is symmetrically sectioned along the installation hole of the incomplete worm gear, and the section is marked with a section line).

[0027] Figure 6 It is a schematic diagram of the installation position of the binocular camera in the present invention. DETAILED DESCRIPTION

[0028] This embodiment discloses a single-motor underactuated robot end effector with a mechanical self-locking function, such as Figure 1 As shown, the single-motor under-actuated robot end effector with a mechanical self-locking function of this embodiment includes an actuator housing 1, a drive motor 2, a left gripper assembly, a right gripper assembly, and a transmission system that utilizes the power of the drive motor 2 to drive the left gripper assembly and the right gripper assembly to complete a gripping action;

[0029] The transmission system includes a reduction mechanism, a differential and a worm gear mechanism; the power of the drive motor 2 is decelerated and torque-increased by the reduction mechanism and then input into the differential; the differential distributes the power to the two worm gear mechanisms and drives the two worms to rotate; the worm wheel of the worm gear mechanism is used to drive the left clamping jaw assembly or the right clamping jaw assembly to complete the clamping action; the worm gear mechanism decelerates and reverses the power output by the differential and transmits it to the clamping jaw assembly of the compound four-bar linkage mechanism, so as to realize the smooth and horizontal clamping of the clamping jaw and maintain the clamping state when the motor loses power.

[0030] like Figure 2 As shown, the deceleration mechanism includes a motor shaft bearing 3, a pinion 4, a large gear 6, and a flange bearing 5. The output shaft of the motor 2 coaxially passes through the motor shaft bearing 3 fixed on the end effector housing 1 to achieve position fixation, and the output shaft of the motor 2 is coaxially fixedly connected with the pinion 4 as a whole to output power. The pinion 4 is coaxially matched with the flange bearing 5 installed on the end effector housing 1, thereby supporting the pinion 4 to rotate around its rotation axis. The pinion 4 meshes with the large gear 6 to achieve the functions of power transmission, deceleration and torque increase. The large gear 6 is welded and fixed to the differential housing 7, and the large gear 6 drives the rotation of the differential housing 7 when it rotates.

[0031] The left and right sides of the actuator housing 1 respectively include a pair of worm gear mechanisms. The left worm gear mechanism consists of a left worm shaft bearing 8, a left worm shaft 9, a left sleeve 10, a left sleeve fixing screw 11 (only 3 of the 6 are indicated in the figure), and a left worm wheel 17. The left worm shaft bearing 8 fixed on the end actuator housing 1 is coaxially matched with the left worm shaft 9, the left sleeve 10 fixed on the end actuator housing 1 is coaxially matched with the left worm shaft 9, the left sleeve 10 is fixed to the end actuator housing 1 by the left sleeve fixing screw 11, and the left worm shaft 9 is supported in the left sleeve 10 by two opposing angular contact bearings, thereby realizing the axial positioning of the left worm shaft 9 in the actuator housing 1, and the left worm bearing 8 tightly fitted on the left worm shaft 9 can slide along the axis in the corresponding mounting hole of the actuator housing 1, thereby preventing the thermal expansion and contraction of the left worm shaft 9 from causing mechanical interference with the actuator housing 1. Right worm gear mechanism (see Figure 3) includes a right sleeve fixing screw 15, a right sleeve 14, a right worm shaft 13, a right worm shaft bearing 12, and a right worm wheel 16. Since the right worm gear mechanism is similar in structure to the left worm gear mechanism and is symmetrically installed, it will not be described here. It should be noted that in order to ensure that the two jaws of the end effector are closed inward or outward at the same time, the left worm shaft 9 and the right worm shaft 13 should be rotated in opposite directions.

[0032] like Figure 3 The differential comprises a differential housing 7, a differential driving shaft 20, a differential driving gear 18, and a differential fixed gear 19. Figure 3 The large gear 6 in the differential is fixedly connected to the differential housing 7, driving the differential to rotate as a whole. Figure 4 A differential moving shaft 20 is mounted on the differential case 7 and rotates with the differential case 7. Two differential moving gears 18 are coaxially mounted inside the differential moving shaft 20. The differential moving gears 18 mesh with two differential fixed gears 19 respectively connected to the left worm shaft 9 and the right worm shaft 13. When the large gear 6 drives the differential case 7 to rotate, the axes of the worm shafts of the two differential moving gears 18 rotate, thereby driving the differential fixed gears, the left worm shaft 9, and the right worm shaft 13 to rotate. When the end effector is closed and does not contact the object, the left clamping jaw body 25 and the right clamping jaw body 28 (such as Figure 2 As shown in the figure, there is no external load, the left worm shaft 9 and the right worm shaft 13 are subjected to equal forces and rotate at the same speed. When one of the clamping jaws touches an object, the worm on the corresponding side is subjected to greater resistance, causing the rotation speed to decrease, and the rotation speed of the worm on the other side increases, thus realizing the function of automatically distributing the rotation speed. At the same time, the left worm shaft 9 and the right worm shaft 13 are single-headed worms. When both clamping jaws touch an object, due to the reaction force of the clamped object on the left clamping jaw body 25 and the right clamping jaw body 28, the left worm wheel 17 and the right worm wheel 16 (as shown in the figure) are rotated at the same speed. Figure 3 As shown in the figure, the left worm 9 and the right worm 13 have a strong effect respectively. Due to the reverse self-locking effect of the single-head worm, the left worm 9 and the right worm 13 can lock their own positions before the motor 2 reverses, realizing the clamping self-locking insurance function.

[0033] like Figure 5As shown, the structure of the clamping jaw assembly adopts a composite four-bar linkage translation mechanism; the left clamping jaw assembly at least includes a left clamping jaw body 25, a left connecting rod I and a left connecting rod II hinged between the left clamping jaw body 25 and the actuator housing 1, a left worm gear fixed to the left worm wheel, and a left push rod 24 hinged between the left worm gear and the left clamping jaw body 25; the actuator housing 1, the left clamping jaw body 25, the left connecting rod I and the left connecting rod II together constitute a parallel four-bar linkage mechanism; the left worm gear, the left push rod 24, the left clamping jaw body 25 and the left connecting rod I together constitute a double rocker mechanism; when the left worm gear 17 rotates, the motion is transmitted to the left clamping jaw body 25, causing it to perform a translational motion relative to the end actuator housing 1. Two worm gear fastening screws 23 are installed on the end actuator housing 1, respectively clamping a worm gear bearing 22 (only one is marked in the figure) to fix the left worm gear 17 at a determined position of the end actuator housing 1, so that the left worm gear 17 can only rotate around itself; the right clamping jaw assembly at least includes a right clamping jaw body 28, a right connecting rod I and a right connecting rod II hinged between the right clamping jaw body 28 and the actuator housing 1, a right worm gear rod fixed to the right worm wheel, and a right push rod hinged between the right worm gear rod and the right clamping jaw body 28; since the right clamping jaw assembly and the left clamping jaw assembly have similar structures and are symmetrically installed, they will not be repeated here.

[0034] Figure 6 Schematic diagram of the installation position of the binocular camera. The binocular camera 26 is fixed to the center of the end effector housing 1 by the camera fixing screws 27 (only 2 of the 4 screws are marked in the figure). After the left clamp body 25 and the right clamp body 28 clamp the object, the binocular camera 26 can measure the left and right offset of the object relative to the center line of the end effector housing 1, so as to feed back the object posture in real time to the control system of the machine where the end effector is installed, so as to perform subsequent precise operations.

[0035] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A single-motor underactuated robot end effector with mechanical self-locking function, characterized in that: It includes an actuator housing, a drive motor, a left clamping jaw assembly, a right clamping jaw assembly, and a transmission system that utilizes the power of the drive motor to drive the left clamping jaw assembly and the right clamping jaw assembly to complete the clamping action; The transmission system includes a reduction mechanism, a differential and a worm gear mechanism; the power of the driving motor is decelerated and torque-increased by the reduction mechanism and then input into the differential; the differential distributes the power to the two worm gear mechanisms and drives the two worms to rotate; the worm wheel of the worm gear mechanism is used to drive the left clamping jaw assembly or the right clamping jaw assembly to complete the clamping action; The differential comprises a differential housing, a differential fixed rotating gear, a differential dynamic rotating gear and a differential dynamic rotating shaft located in the housing; the differential dynamic rotating shaft is fixed in the housing and is perpendicular to the worm; the two differential dynamic rotating gears are outer-mounted on the differential dynamic rotating shaft; the two differential fixed rotating gears are respectively connected to the worm shafts of the two worm gear mechanisms and mesh with the differential dynamic rotating gear; The large gear is fixedly connected to the differential housing, driving the differential to rotate as a whole; the differential housing is equipped with a differential dynamic shaft, which rotates with the differential housing; two differential dynamic gears are coaxially installed on the differential dynamic shaft, and the differential dynamic gears mesh with two differential fixed gears respectively fixedly connected to the left worm shaft and the right worm shaft; When the large gear drives the differential housing to rotate, the axes of the worm shafts of the two differential moving gears rotate, thereby driving the differential fixed gear, the left worm shaft and the right worm shaft to rotate.

2. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 1, characterized in that: The speed reduction mechanism includes a small gear drivingly connected to the output shaft of the drive motor and a large gear fixed to the differential housing.

3. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 2, characterized in that: The left jaw assembly and the right jaw assembly respectively include at least a jaw body, a connecting rod I and a connecting rod II hinged between the jaw body and the actuator housing, a worm gear fixed to the worm wheel, and a push rod hinged between the worm gear and the jaw body; the actuator housing, the jaw body, the connecting rod I and the connecting rod II together constitute a parallel four-bar linkage mechanism; the worm gear, the push rod, the jaw body and the connecting rod I together constitute a double rocker mechanism.

4. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 3, characterized in that: The actuator housing is provided with a binocular camera centered between the left clamping jaw assembly and the right clamping jaw assembly.

5. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 4, characterized in that: The side of the actuator housing is provided with a motor mounting hole and a motor shaft input hole for the output shaft of the driving motor to extend therein, and a cavity for accommodating a speed reduction mechanism and a differential is formed inside the actuator housing.

6. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 5, characterized in that: The side of the actuator housing is provided with a motor mounting hole and a motor shaft input hole for the output shaft of the driving motor to extend therein, and a cavity for accommodating a speed reduction mechanism and a differential is formed inside the actuator housing.

7. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 6, characterized in that: A cavity for accommodating the worm gear mechanism is formed inside the actuator housing.

8. The single-motor underactuated robot end effector with mechanical self-locking function according to claim 7, characterized in that: The worm wheel is an incomplete worm wheel; the worm wheel rod is a variable cross-section rod, which is integrally formed on the circumferential portion of the incomplete worm wheel without gear teeth.

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